Sample records for plasma current profiles

  1. Surface currents associated with external kink modes in tokamak plasmas during a major disruption

    NASA Astrophysics Data System (ADS)

    Ng, C. S.; Bhattacharjee, A.

    2017-10-01

    The surface current on the plasma-vacuum interface during a disruption event involving kink instability can play an important role in driving current into the vacuum vessel. However, there have been disagreements over the nature or even the sign of the surface current in recent theoretical calculations based on idealized step-function background plasma profiles. We revisit such calculations by replacing step-function profiles with more realistic profiles characterized by a strong but finite gradient along the radial direction. It is shown that the resulting surface current is no longer a delta-function current density, but a finite and smooth current density profile with an internal structure, concentrated within the region with a strong plasma pressure gradient. Moreover, this current density profile has peaks of both signs, unlike the delta-function case with a sign opposite to, or the same as the plasma current. We show analytically and numerically that such current density can be separated into two parts, with one of them, called the convective current density, describing the transport of the background plasma density by the displacement, and the other part that remains, called the residual current density. It is argued that consideration of both types of current density is important and can resolve past controversies.

  2. Kinetic simulations of the stability of a plasma confined by the magnetic field of a current rod

    NASA Astrophysics Data System (ADS)

    Tonge, J.; Leboeuf, J. N.; Huang, C.; Dawson, J. M.

    2003-09-01

    The kinetic stability of a plasma in the magnetic field of a current rod is investigated for various temperature and density profiles using three-dimensional particle-in-cell simulations. Such a plasma obeys similar physics to a plasma in a dipole magnetic field, while it is easier to perform computer simulations, and do theoretical analysis, of a plasma in the field of a current rod. Simple energy principle calculations and simulations with a variety of temperature and density profiles show that the plasma is stable to interchange for pressure profiles proportional to r-10/3. As predicted by theory the simulations also show that the density profile will be stationary as long as density is proportional to r-2 even though the temperature profile may not be stable.

  3. Linear MHD stability analysis of post-disruption plasmas in ITER

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Aleynikova, K., E-mail: ksenia.aleynikova@gmail.com; Huijsmans, G. T. A.; Aleynikov, P.

    2016-05-15

    Most of the plasma current can be replaced by a runaway electron (RE) current during plasma disruptions in ITER. In this case the post-disruption plasma current profile is likely to be more peaked than the pre-disruption profile. The MHD activity of such plasma will affect the runaway electron generation and confinement and the dynamics of the plasma position evolution (Vertical Displacement Event), limiting the timeframe for runaway electrons and disruption mitigation. In the present paper, we evaluate the influence of the possible RE seed current parameters on the onset of the MHD instabilities. By varying the RE seed current profile,more » we search for subsequent plasma evolutions with the highest and the lowest MHD activity. This information can be applied to a development of desirable ITER disruption scenario.« less

  4. Observation of instability-induced current redistribution in a spherical-torus plasma.

    PubMed

    Menard, J E; Bell, R E; Gates, D A; Kaye, S M; LeBlanc, B P; Levinton, F M; Medley, S S; Sabbagh, S A; Stutman, D; Tritz, K; Yuh, H

    2006-09-01

    A motional Stark effect diagnostic has been utilized to reconstruct the parallel current density profile in a spherical-torus plasma for the first time. The measured current profile compares favorably with neoclassical theory when no large-scale magnetohydrodynamic instabilities are present in the plasma. However, a current profile anomaly is observed during saturated interchange-type instability activity. This apparent anomaly can be explained by redistribution of neutral beam injection current drive and represents the first observation of interchange-type instabilities causing such redistribution. The associated current profile modifications contribute to sustaining the central safety factor above unity for over five resistive diffusion times, and similar processes may contribute to improved operational scenarios proposed for ITER.

  5. Reconstruction of Pressure Profile Evolution during Levitated Dipole Experiments

    NASA Astrophysics Data System (ADS)

    Mauel, M.; Garnier, D.; Boxer, A.; Ellsworth, J.; Kesner, J.

    2008-11-01

    Magnetic levitation of the LDX superconducting dipole causes significant changes in the measured diamagnetic flux and what appears to be an isotropic plasma pressure profile (p˜p||). This poster describes the reconstruction of plasma current and plasma pressure profiles from external measurements of the equilibrium magnetic field, which vary substantially as a function of time depending upon variations in neutral pressure and multifrequency ECRH power levels. Previous free-boundary reconstructions of plasma equilibrium showed the plasma to be anisotropic and highly peaked at the location of the cyclotron resonance of the microwave heating sources. Reconstructions of the peaked plasma pressures confined by a levitated dipole incorporate the small axial motion of the dipole (±5 mm), time varying levitation coil currents, eddy currents flowing in the vacuum vessel, constant magnetic flux linking the superconductor, and new flux loops located near the hot plasma in order to closely couple to plasma current and dipole current variations. I. Karim, et al., J. Fusion Energy, 26 (2007) 99.

  6. Test of electical resistivity and current diffusion modelling on MAST and JET

    NASA Astrophysics Data System (ADS)

    Keeling, D. L.; Challis, C. D.; Jenkins, I.; Hawkes, N. C.; Lupelli, I.; Michael, C.; de Bock, M. F. M.; the MAST Team; contributors, JET

    2018-01-01

    Experiments have been carried out on the MAST and JET tokamaks intended to compare the electrical resistivity of the plasma with theoretical formulations. The tests consist of obtaining motional stark effect (MSE) measurements in MHD-free plasmas during plasma current ramp-up (JET and MAST), ramp-down (MAST) and in stationary state (JET and MAST). Simulations of these plasmas are then performed in which the current profile evolution is calculated according to the poloidal field diffusion equation (PFDE) with classical or neoclassical resistivity. Synthetic MSE data are produced in the simulations for direct comparison with the experimental data. It is found that the toroidal current profile evolution modelled using neoclassical resistivity did not match the experimental observations on either device during current ramp-up or ramp-down as concluded from comparison of experimental and synthetic MSE profiles. In these phases, use of neoclassical resistivity in the modelling systematically overestimates the rate of current profile evolution. During the stationary state however, the modelled toroidal current profile matched experimental observations to a high degree of accuracy on both devices using neoclassical resistivity. Whilst no solution to the mismatch in the dynamic phases of the plasma is proposed, it is suggested that some physical process other than MHD which is not captured by the simple diffusive model of current profile evolution is responsible.

  7. Profile control simulations and experiments on TCV: a controller test environment and results using a model-based predictive controller

    NASA Astrophysics Data System (ADS)

    Maljaars, E.; Felici, F.; Blanken, T. C.; Galperti, C.; Sauter, O.; de Baar, M. R.; Carpanese, F.; Goodman, T. P.; Kim, D.; Kim, S. H.; Kong, M.; Mavkov, B.; Merle, A.; Moret, J. M.; Nouailletas, R.; Scheffer, M.; Teplukhina, A. A.; Vu, N. M. T.; The EUROfusion MST1-team; The TCV-team

    2017-12-01

    The successful performance of a model predictive profile controller is demonstrated in simulations and experiments on the TCV tokamak, employing a profile controller test environment. Stable high-performance tokamak operation in hybrid and advanced plasma scenarios requires control over the safety factor profile (q-profile) and kinetic plasma parameters such as the plasma beta. This demands to establish reliable profile control routines in presently operational tokamaks. We present a model predictive profile controller that controls the q-profile and plasma beta using power requests to two clusters of gyrotrons and the plasma current request. The performance of the controller is analyzed in both simulation and TCV L-mode discharges where successful tracking of the estimated inverse q-profile as well as plasma beta is demonstrated under uncertain plasma conditions and the presence of disturbances. The controller exploits the knowledge of the time-varying actuator limits in the actuator input calculation itself such that fast transitions between targets are achieved without overshoot. A software environment is employed to prepare and test this and three other profile controllers in parallel in simulations and experiments on TCV. This set of tools includes the rapid plasma transport simulator RAPTOR and various algorithms to reconstruct the plasma equilibrium and plasma profiles by merging the available measurements with model-based predictions. In this work the estimated q-profile is merely based on RAPTOR model predictions due to the absence of internal current density measurements in TCV. These results encourage to further exploit model predictive profile control in experiments on TCV and other (future) tokamaks.

  8. Current drive for stability of thermonuclear plasma reactor

    NASA Astrophysics Data System (ADS)

    Amicucci, L.; Cardinali, A.; Castaldo, C.; Cesario, R.; Galli, A.; Panaccione, L.; Paoletti, F.; Schettini, G.; Spigler, R.; Tuccillo, A.

    2016-01-01

    To produce in a thermonuclear fusion reactor based on the tokamak concept a sufficiently high fusion gain together stability necessary for operations represent a major challenge, which depends on the capability of driving non-inductive current in the hydrogen plasma. This request should be satisfied by radio-frequency (RF) power suitable for producing the lower hybrid current drive (LHCD) effect, recently demonstrated successfully occurring also at reactor-graded high plasma densities. An LHCD-based tool should be in principle capable of tailoring the plasma current density in the outer radial half of plasma column, where other methods are much less effective, in order to ensure operations in the presence of unpredictably changes of the plasma pressure profiles. In the presence of too high electron temperatures even at the periphery of the plasma column, as envisaged in DEMO reactor, the penetration of the coupled RF power into the plasma core was believed for long time problematic and, only recently, numerical modelling results based on standard plasma wave theory, have shown that this problem should be solved by using suitable parameter of the antenna power spectrum. We show here further information on the new understanding of the RF power deposition profile dependence on antenna parameters, which supports the conclusion that current can be actively driven over a broad layer of the outer radial half of plasma column, thus enabling current profile control necessary for the stability of a reactor.

  9. Detection of an electron beam in a high density plasma via an electrostatic probe

    NASA Astrophysics Data System (ADS)

    Majeski, Stephen; Yoo, Jongsoo; Zweben, Stewart; Yamada, Masaaki

    2018-07-01

    An electron beam is detected by a 1D floating potential probe array in a relatively high density (1012–1013 cm‑3) and low temperature (∼5 eV) plasma of the Magnetic Reconnection Experiment. Clear perturbations in the floating potential profile by the electron beam are observed. Based on the floating potential profile and a current balance equation to the probe array tips, the effective width of the electron beam is determined, from which we determine the radial and toroidal beam current density profiles. After the profile of the electron beam is specified from the measured beam current, we demonstrate the consistency of the current balance equation and the location of the perturbation is also in agreement with field line mapping. No significant broadening of the electron beam is observed after the beam propagates for tens of centimeters through the high density plasma. These results prove that the field line mapping is, in principle, possible in high density plasmas.

  10. Vertical Position and Current Profile Measurements by Faraday-effect Polarimetry On EAST tokamak

    NASA Astrophysics Data System (ADS)

    Ding, Weixing; Liu, H. Q.; Jie, Y. X.; Brower, D. L.; Qian, J. P.; Zou, Z. Y.; Lian, H.; Wang, S. X.; Luo, Z. P.; Xiao, B. J.; Ucla Team; Asipp Team

    2017-10-01

    A primary goal for ITER and prospective fusion power reactors is to achieve controlled long-pulse/steady-state burning plasmas. For elongated divertor plasmas, both the vertical position and current profile have to be precisely controlled to optimize performance and prevent disruptions. An eleven-channel laser-based POlarimeter-INTerferometer (POINT) system has been developed for measuring the internal magnetic field in the EAST tokamak and can be used to obtain the plasma current profile and vertical position. Current profiles are determined from equilibrium reconstruction including internal magnetic field measurements as internal constraints. Horizontally-viewing chords at/near the mid-plane allow us to determine plasma vertical position non-inductively with subcentimeter spatial resolution and time response up to 1 s. The polarimeter-based position measurement, which does not require equilibrium reconstruction, is benchmarked against conventional flux loop measurements and can be exploited for feedback control. Work supported by US DOE through Grants No. DE-FG02-01ER54615 and No. DC-SC0010469.

  11. Detection of an electron beam in a high density plasma via an electrostatic probe

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Majeski, Stephen; Yoo, Jongsoo; Zweben, Stewart

    Here, an electron beam is detected by a 1D floating potential probe array in a relatively high density (10 12–10 13 cm -3) and low temperature (~5 eV) plasma of the Magnetic Reconnection Experiment. Clear perturbations in the floating potential profile by the electron beam are observed. Based on the floating potential profile and a current balance equation to the probe array tips, the effective width of the electron beam is determined, from which we determine the radial and toroidal beam current density profiles. After the profile of the electron beam is specified from the measured beam current, we demonstratemore » the consistency of the current balance equation and the location of the perturbation is also in agreement with field line mapping. No significant broadening of the electron beam is observed after the beam propagates for tens of centimeters through the high density plasma. These results prove that the field line mapping is, in principle, possible in high density plasmas.« less

  12. Detection of an electron beam in a high density plasma via an electrostatic probe

    DOE PAGES

    Majeski, Stephen; Yoo, Jongsoo; Zweben, Stewart; ...

    2018-05-08

    Here, an electron beam is detected by a 1D floating potential probe array in a relatively high density (10 12–10 13 cm -3) and low temperature (~5 eV) plasma of the Magnetic Reconnection Experiment. Clear perturbations in the floating potential profile by the electron beam are observed. Based on the floating potential profile and a current balance equation to the probe array tips, the effective width of the electron beam is determined, from which we determine the radial and toroidal beam current density profiles. After the profile of the electron beam is specified from the measured beam current, we demonstratemore » the consistency of the current balance equation and the location of the perturbation is also in agreement with field line mapping. No significant broadening of the electron beam is observed after the beam propagates for tens of centimeters through the high density plasma. These results prove that the field line mapping is, in principle, possible in high density plasmas.« less

  13. Towards Current Profile Control in ITER: Potential Approaches and Research Needs

    NASA Astrophysics Data System (ADS)

    Schuster, E.; Barton, J. E.; Wehner, W. P.

    2014-10-01

    Many challenging plasma control problems still need to be addressed in order for the ITER Plasma Control System (PCS) to be able to successfully achieve the ITER project goals. For instance, setting up a suitable toroidal current density profile is key for one possible advanced scenario characterized by noninductive sustainment of the plasma current and steady-state operation. The nonlinearity and high dimensionality exhibited by the plasma demand a model-based current-profile control synthesis procedure that can accommodate this complexity through embedding the known physics within the design. The development of a model capturing the dynamics of the plasma relevant for control design enables not only the design of feedback controllers for regulation or tracking but also the design of optimal feedforward controllers for a systematic model-based approach to scenario planning, the design of state estimators for a reliable real-time reconstruction of the plasma internal profiles based on limited and noisy diagnostics, and the development of a fast predictive simulation code for closed-loop performance evaluation before implementation. Progress towards control-oriented modeling of the current profile evolution and associated control design has been reported following both data-driven and first-principles-driven approaches. An overview of these two approaches will be provided, as well as a discussion on research needs associated with each one of the model applications described above. Supported by the US Department of Energy under DE-SC0001334 and DE-SC0010661.

  14. Effect of resistivity profile on current decay time of initial phase of current quench in neon-gas-puff inducing disruptions of JT-60U

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kawakami, S.; Ohno, N.; Shibata, Y.

    2013-11-15

    According to an early work [Y. Shibata et al., Nucl. Fusion 50, 025015 (2010)] on the behavior of the plasma current decay in the JT-60U disruptive discharges caused by the radiative collapse with a massive neon-gas-puff, the increase of the internal inductance mainly determined the current decay time of plasma current during the initial phase of current quench. To investigate what determines the increase of the internal inductance, we focus attention on the relationship between the electron temperature (or the resistivity) profile and the time evolution of the current density profile and carry out numerical calculations. As a result, wemore » find the reason of the increase of the internal inductance: The current density profile at the start of the current quench is broader than an expected current density profile in the steady state, which is determined by the temperature (or resistivity) profile. The current density profile evolves into peaked one and the internal inductance is increasing.« less

  15. Analysis of Rotation and Transport Data in C-Mod ITB Plasmas

    NASA Astrophysics Data System (ADS)

    Fiore, C. L.; Rice, J. E.; Reinke, M. L.; Podpaly, Y.; Bespamyatnov, I. O.; Rowan, W. L.

    2009-11-01

    Internal transport barriers (ITBs) spontaneously form near the half radius of Alcator C-Mod plasmas when the EDA H-mode is sustained for several energy confinement times in either off-axis ICRF heated discharges or in purely ohmic heated plasmas. These plasmas exhibit strongly peaked density and pressure profiles, static or peaking temperature profiles, peaking impurity density profiles, and thermal transport coefficients that approach neoclassical values in the core. It has long been observed that the intrinsic central plasma rotation that is strongly co-current following the H-mode transition slows and often reverses as the density peaks as the ITB forms. Recent spatial measurements demonstrate that the rotation profile develops a well in the core region that decreases continuously as central density rises while the value outside of the core remains strongly co-current. This results in the formation of a steep potential gradient/strong electric field at the location of the foot of the ITB density profile. The resulting E X B shearing rate is also quite significant at the foot. These analyses and the implications for plasma transport and stability will be presented.

  16. Passive MHD Spectroscopy for Enabling Magnetic Reconstructions on Spherical Tokamak Plasmas at General Fusion Inc

    NASA Astrophysics Data System (ADS)

    O'Shea, Peter; Laberge, Michel; Mossman, Alex; Reynolds, Meritt

    2017-10-01

    Magnetic reconstructions on lab based plasma injectors at General Fusion relies heavily on edge magnetic (``Bdot'') probes. On plasma experiments built for field compression (PCS) tests, the number and locations of Bdot probes is limited by mechanical constraints. Additional information about the q profiles near the core in our Spector plasmas is obtained using passive MHD spectroscopy. The coaxial helicity injection (CHI) formation process naturally generates hollow current profiles and reversed shear early in each discharge. Central Ohmic heating naturally peaks the current profiles as our plasmas evolve in time, simultaneously reducing the core safety factor, q(0), and reverse shear. As the central, non-monotonic q-profile crosses rational flux surfaces, we observe transient magnetic reconnection events (MRE's) due to the double tearing mode. Modal analysis allows us to infer the q surfaces involved in each burst. The parametric dependence of the timing of MRE's allows us to estimate the continuous time evolution of the core q profile. Combining core MHD spectroscopy with edge magnetic probe measurements greatly enhances our certainty of the overall q profile.

  17. Correlation of ion and beam current densities in Kaufman thrusters.

    NASA Technical Reports Server (NTRS)

    Wilbur, P. J.

    1973-01-01

    In the absence of direct impingement erosion, electrostatic thruster accelerator grid lifetime is defined by the charge exchange erosion that occurs at peak values of the ion beam current density. In order to maximize the thrust from an engine with a specified grid lifetime, the ion beam current density profile should therefore be as flat as possible. Knauer (1970) has suggested this can be achieved by establishing a radial plasma uniformity within the thruster discharge chamber; his tests with the radial field thruster provide an example of uniform plasma properties within the chamber and a flat ion beam profile occurring together. It is shown that, in particular, the ion density profile within the chamber determines the beam current density profile, and that a uniform ion density profile at the screen grid end of the discharge chamber should lead to a flat beam current density profile.

  18. Numerical optimization of actuator trajectories for ITER hybrid scenario profile evolution

    NASA Astrophysics Data System (ADS)

    van Dongen, J.; Felici, F.; Hogeweij, G. M. D.; Geelen, P.; Maljaars, E.

    2014-12-01

    Optimal actuator trajectories for an ITER hybrid scenario ramp-up are computed using a numerical optimization method. For both L-mode and H-mode scenarios, the time trajectory of plasma current, EC heating and current drive distribution is determined that minimizes a chosen cost function, while satisfying constraints. The cost function is formulated to reflect two desired properties of the plasma q profile at the end of the ramp-up. The first objective is to maximize the ITG turbulence threshold by maximizing the volume-averaged s/q ratio. The second objective is to achieve a stationary q profile by having a flat loop voltage profile. Actuator and physics-derived constraints are included, imposing limits on plasma current, ramp rates, internal inductance and q profile. This numerical method uses the fast control-oriented plasma profile evolution code RAPTOR, which is successfully benchmarked against more complete CRONOS simulations for L-mode and H-mode mode ITER hybrid scenarios. It is shown that the optimized trajectories computed using RAPTOR also result in an improved ramp-up scenario for CRONOS simulations using the same input trajectories. Furthermore, the optimal trajectories are shown to vary depending on the precise timing of the L-H transition.

  19. Model-based Optimization and Feedback Control of the Current Density Profile Evolution in NSTX-U

    NASA Astrophysics Data System (ADS)

    Ilhan, Zeki Okan

    Nuclear fusion research is a highly challenging, multidisciplinary field seeking contributions from both plasma physics and multiple engineering areas. As an application of plasma control engineering, this dissertation mainly explores methods to control the current density profile evolution within the National Spherical Torus eXperiment-Upgrade (NSTX-U), which is a substantial upgrade based on the NSTX device, which is located in Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ. Active control of the toroidal current density profile is among those plasma control milestones that the NSTX-U program must achieve to realize its next-step operational goals, which are characterized by high-performance, long-pulse, MHD-stable plasma operation with neutral beam heating. Therefore, the aim of this work is to develop model-based, feedforward and feedback controllers that can enable time regulation of the current density profile in NSTX-U by actuating the total plasma current, electron density, and the powers of the individual neutral beam injectors. Motivated by the coupled, nonlinear, multivariable, distributed-parameter plasma dynamics, the first step towards control design is the development of a physics-based, control-oriented model for the current profile evolution in NSTX-U in response to non-inductive current drives and heating systems. Numerical simulations of the proposed control-oriented model show qualitative agreement with the high-fidelity physics code TRANSP. The next step is to utilize the proposed control-oriented model to design an open-loop actuator trajectory optimizer. Given a desired operating state, the optimizer produces the actuator trajectories that can steer the plasma to such state. The objective of the feedforward control design is to provide a more systematic approach to advanced scenario planning in NSTX-U since the development of such scenarios is conventionally carried out experimentally by modifying the tokamak's actuator trajectories and analyzing the resulting plasma evolution. Finally, the proposed control-oriented model is embedded in feedback control schemes based on optimal control and Model Predictive Control (MPC) approaches. Integrators are added to the standard Linear Quadratic Gaussian (LQG) and MPC formulations to provide robustness against various modeling uncertainties and external disturbances. The effectiveness of the proposed feedback controllers in regulating the current density profile in NSTX-U is demonstrated in closed-loop nonlinear simulations. Moreover, the optimal feedback control algorithm has been implemented successfully in closed-loop control simulations within TRANSP through the recently developed Expert routine. (Abstract shortened by ProQuest.).

  20. Evidence cross-validation and Bayesian inference of MAST plasma equilibria

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nessi, G. T. von; Hole, M. J.; Svensson, J.

    2012-01-15

    In this paper, current profiles for plasma discharges on the mega-ampere spherical tokamak are directly calculated from pickup coil, flux loop, and motional-Stark effect observations via methods based in the statistical theory of Bayesian analysis. By representing toroidal plasma current as a series of axisymmetric current beams with rectangular cross-section and inferring the current for each one of these beams, flux-surface geometry and q-profiles are subsequently calculated by elementary application of Biot-Savart's law. The use of this plasma model in the context of Bayesian analysis was pioneered by Svensson and Werner on the joint-European tokamak [Svensson and Werner,Plasma Phys. Controlledmore » Fusion 50(8), 085002 (2008)]. In this framework, linear forward models are used to generate diagnostic predictions, and the probability distribution for the currents in the collection of plasma beams was subsequently calculated directly via application of Bayes' formula. In this work, we introduce a new diagnostic technique to identify and remove outlier observations associated with diagnostics falling out of calibration or suffering from an unidentified malfunction. These modifications enable a good agreement between Bayesian inference of the last-closed flux-surface with other corroborating data, such as that from force balance considerations using EFIT++[Appel et al., ''A unified approach to equilibrium reconstruction'' Proceedings of the 33rd EPS Conference on Plasma Physics (Rome, Italy, 2006)]. In addition, this analysis also yields errors on the plasma current profile and flux-surface geometry as well as directly predicting the Shafranov shift of the plasma core.« less

  1. Non-axisymmetric equilibrium reconstruction of a current-carrying stellarator using external magnetic and soft x-ray inversion radius measurements

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ma, X., E-mail: xzm0005@auburn.edu; Maurer, D. A.; Knowlton, S. F.

    2015-12-15

    Non-axisymmetric free-boundary equilibrium reconstructions of stellarator plasmas are performed for discharges in which the magnetic configuration is strongly modified by ohmically driven plasma current. These studies were performed on the compact toroidal hybrid device using the V3FIT reconstruction code with a set of 50 magnetic diagnostics external to the plasma. With the assumption of closed magnetic flux surfaces, the reconstructions using external magnetic measurements allow accurate estimates of the net toroidal flux within the last closed flux surface, the edge safety factor, and the plasma shape of these highly non-axisymmetric plasmas. The inversion radius of standard sawteeth is used tomore » infer the current profile near the magnetic axis; with external magnetic diagnostics alone, the current density profile is imprecisely reconstructed.« less

  2. Non-axisymmetric equilibrium reconstruction of a current-carrying stellarator using external magnetic and soft x-ray inversion radius measurements

    NASA Astrophysics Data System (ADS)

    Ma, X.; Maurer, D. A.; Knowlton, S. F.; ArchMiller, M. C.; Cianciosa, M. R.; Ennis, D. A.; Hanson, J. D.; Hartwell, G. J.; Hebert, J. D.; Herfindal, J. L.; Pandya, M. D.; Roberds, N. A.; Traverso, P. J.

    2015-12-01

    Non-axisymmetric free-boundary equilibrium reconstructions of stellarator plasmas are performed for discharges in which the magnetic configuration is strongly modified by ohmically driven plasma current. These studies were performed on the compact toroidal hybrid device using the V3FIT reconstruction code with a set of 50 magnetic diagnostics external to the plasma. With the assumption of closed magnetic flux surfaces, the reconstructions using external magnetic measurements allow accurate estimates of the net toroidal flux within the last closed flux surface, the edge safety factor, and the plasma shape of these highly non-axisymmetric plasmas. The inversion radius of standard sawteeth is used to infer the current profile near the magnetic axis; with external magnetic diagnostics alone, the current density profile is imprecisely reconstructed.

  3. Non-axisymmetric equilibrium reconstruction of a current-carrying stellarator using external magnetic and soft x-ray inversion radius measurements

    DOE PAGES

    Ma, X.; Maurer, D. A.; Knowlton, Stephen F.; ...

    2015-12-22

    Non-axisymmetric free-boundary equilibrium reconstructions of stellarator plasmas are performed for discharges in which the magnetic configuration is strongly modified by ohmically driven plasma current. These studies were performed on the compact toroidal hybrid device using the V3FIT reconstruction code with a set of 50 magnetic diagnostics external to the plasma. With the assumption of closed magnetic flux surfaces, the reconstructions using external magnetic measurements allow accurate estimates of the net toroidal flux within the last closed flux surface, the edge safety factor, and the plasma shape of these highly non-axisymmetric plasmas. Lastly, the inversion radius of standard saw-teeth is usedmore » to infer the current profile near the magnetic axis; with external magnetic diagnostics alone, the current density profile is imprecisely reconstructed.« less

  4. Development of internal magnetic probe for current density profile measurement in Versatile Experiment Spherical Torus

    NASA Astrophysics Data System (ADS)

    Yang, J.; Lee, J. W.; Jung, B. K.; Chung, K. J.; Hwang, Y. S.

    2014-11-01

    An internal magnetic probe using Hall sensors to measure a current density profile directly with perturbation of less than 10% to the plasma current is successfully operated for the first time in Versatile Experiment Spherical Torus (VEST). An appropriate Hall sensor is chosen to produce sufficient signals for VEST magnetic field while maintaining the small size of 10 mm in outer diameter. Temperature around the Hall sensor in a typical VEST plasma is regulated by blown air of 2 bars. First measurement of 60 kA VEST ohmic discharge shows a reasonable agreement with the total plasma current measured by Rogowski coil in VEST.

  5. Study on the Characteristics of Plasma Profiles in Improved Confinement Plasmas in HT-7 Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Zhang, Shouyin; Gao, Xiang; Li, Jiangang; Wan, Baonian; Kuang, Guangli; Mao, Jianshan; Zhang, Xiaodong; Xie, Jikang; Wan, Yuanxi; Team HT-7

    2000-10-01

    In HT-7 superconducting tokamak of circular limiter configuration (R0=122cm, a=30cm, Bt:1 ~2.2T), plasma profiles were modified and controlled by means of gas puffing, supersonic molecule injection, pellet injection, ICRF and IBW heating as well as LHW heating and current drive; improved plasma confinements were achieved either by application of one of the above measures or by the combination of them, study of the effects of the characteristics of plasma profiles on plasma confinements were performed. The results show that in most of the improved confinement plasmas in HT-7, there are very steep and strong peeking electron temperature profiles in core plasma, and/or large decrease of local temperature in radius of 0.5 ~0.7a which makes temperature gradient steeper when improvements begin, as temperature profile evolves back to previous normal shape the improvements end. Electron density profile and soft X-ray profiles were studied as well. This research was supported under Natural Science Foundation of China contract No.19905010.

  6. Tokamak plasma current disruption infrared control system

    DOEpatents

    Kugel, Henry W.; Ulrickson, Michael

    1987-01-01

    In a magnetic plasma confinment device having an inner toroidal limiter mounted on an inner wall of a plasma containment vessel, an arrangement is provided for monitoring vertical temperature profiles of the limiter. The temperature profiles are taken at brief time intervals, in a time scan fashion. The time scans of the vertical temperature profile are continuously monitored to detect the presence of a peaked temperature excursion, which, according to the present invention, is a precursor of a subsequent major plasma disruption. A fast scan of the temperature profile is made so as to provide a time interval in real time prior to the major plasma disruption, such that corrective action can be taken to reduce the harmful effects of the plasma disruption.

  7. Non-axisymmetric equilibrium reconstruction and suppression of density limit disruptions in a current-carrying stellarator

    NASA Astrophysics Data System (ADS)

    Ma, Xinxing; Ennis, D. A.; Hanson, J. D.; Hartwell, G. J.; Knowlton, S. F.; Maurer, D. A.

    2017-10-01

    Non-axisymmetric equilibrium reconstructions have been routinely performed with the V3FIT code in the Compact Toroidal Hybrid (CTH), a stellarator/tokamak hybrid. In addition to 50 external magnetic measurements, 160 SXR emissivity measurements are incorporated into V3FIT to reconstruct the magnetic flux surface geometry and infer the current distribution within the plasma. Improved reconstructions of current and q profiles provide insight into understanding the physics of density limit disruptions observed in current-carrying discharges in CTH. It is confirmed that the final scenario of the density limit of CTH plasmas is consistent with classic observations in tokamaks: current profile shrinkage leads to growing MHD instabilities (tearing modes) followed by a loss of MHD equilibrium. It is also observed that the density limit at a given current linearly increases with increasing amounts of 3D shaping fields. Consequently, plasmas with densities up to two times the Greenwald limit are attained. Equilibrium reconstructions show that addition of 3D fields effectively moves resonance surfaces towards the edge of the plasma where the current profile gradient is less, providing a stabilizing effect. This work is supported by US Department of Energy Grant No. DE-FG02-00ER54610.

  8. Integrated modeling of plasma ramp-up in DIII-D ITER-like and high bootstrap current scenario discharges

    NASA Astrophysics Data System (ADS)

    Wu, M. Q.; Pan, C. K.; Chan, V. S.; Li, G. Q.; Garofalo, A. M.; Jian, X.; Liu, L.; Ren, Q. L.; Chen, J. L.; Gao, X.; Gong, X. Z.; Ding, S. Y.; Qian, J. P.; Cfetr Physics Team

    2018-04-01

    Time-dependent integrated modeling of DIII-D ITER-like and high bootstrap current plasma ramp-up discharges has been performed with the equilibrium code EFIT, and the transport codes TGYRO and ONETWO. Electron and ion temperature profiles are simulated by TGYRO with the TGLF (SAT0 or VX model) turbulent and NEO neoclassical transport models. The VX model is a new empirical extension of the TGLF turbulent model [Jian et al., Nucl. Fusion 58, 016011 (2018)], which captures the physics of multi-scale interaction between low-k and high-k turbulence from nonlinear gyro-kinetic simulation. This model is demonstrated to accurately model low Ip discharges from the EAST tokamak. Time evolution of the plasma current density profile is simulated by ONETWO with the experimental current ramp-up rate. The general trend of the predicted evolution of the current density profile is consistent with that obtained from the equilibrium reconstruction with Motional Stark effect constraints. The predicted evolution of βN , li , and βP also agrees well with the experiments. For the ITER-like cases, the predicted electron and ion temperature profiles using TGLF_Sat0 agree closely with the experimental measured profiles, and are demonstrably better than other proposed transport models. For the high bootstrap current case, the predicted electron and ion temperature profiles perform better in the VX model. It is found that the SAT0 model works well at high IP (>0.76 MA) while the VX model covers a wider range of plasma current ( IP > 0.6 MA). The results reported in this paper suggest that the developed integrated modeling could be a candidate for ITER and CFETR ramp-up engineering design modeling.

  9. Modeling of the control of the driven current profile in ICRF MCCD on EAST plasma

    NASA Astrophysics Data System (ADS)

    Yin, L.; Yang, C.; Gong, X. Y.; Lu, X. Q.; Cao, J. J.; Wu, Z. Y.; Chen, Y.; Du, D.

    2018-05-01

    Control of the current profile is a crucial issue for improved confinement and the inhibition of instability in advanced tokamak operation. Using typical discharge data for the Experimental Advanced Superconducting Tokamak, numerical simulations of driven-current profile control in mode conversion current drive (MCCD) in the ion cyclotron range of frequencies were performed employing a full-wave method and Ehst-Karney efficiency formula. Results indicate that the driven current profile in MCCD can be effectively modified by shifting the mode conversion layer. The peak of the driven current can be located at an aimed position in the normalized minor radius range (-0.60 ≤r/a≤0) by changing the radiofrequency and the minority-ion concentration. The efficiency of the off-axis MCCD can reach 233 kA/MW through optimization, and the mode converted ion cyclotron wave plays an important role in such scenarios. The effects of electron temperature and plasma density on the driven current profile are also investigated.

  10. Performance Assessment of Model-Based Optimal Feedforward and Feedback Current Profile Control in NSTX-U using the TRANSP Code

    NASA Astrophysics Data System (ADS)

    Ilhan, Z.; Wehner, W. P.; Schuster, E.; Boyer, M. D.; Gates, D. A.; Gerhardt, S.; Menard, J.

    2015-11-01

    Active control of the toroidal current density profile is crucial to achieve and maintain high-performance, MHD-stable plasma operation in NSTX-U. A first-principles-driven, control-oriented model describing the temporal evolution of the current profile has been proposed earlier by combining the magnetic diffusion equation with empirical correlations obtained at NSTX-U for the electron density, electron temperature, and non-inductive current drives. A feedforward + feedback control scheme for the requlation of the current profile is constructed by embedding the proposed nonlinear, physics-based model into the control design process. Firstly, nonlinear optimization techniques are used to design feedforward actuator trajectories that steer the plasma to a desired operating state with the objective of supporting the traditional trial-and-error experimental process of advanced scenario planning. Secondly, a feedback control algorithm to track a desired current profile evolution is developed with the goal of adding robustness to the overall control scheme. The effectiveness of the combined feedforward + feedback control algorithm for current profile regulation is tested in predictive simulations carried out in TRANSP. Supported by PPPL.

  11. Off-axis current drive and real-time control of current profile in JT-60U

    NASA Astrophysics Data System (ADS)

    Suzuki, T.; Ide, S.; Oikawa, T.; Fujita, T.; Ishikawa, M.; Seki, M.; Matsunaga, G.; Hatae, T.; Naito, O.; Hamamatsu, K.; Sueoka, M.; Hosoyama, H.; Nakazato, M.; JT-60 Team

    2008-04-01

    Aiming at optimization of current profile in high-β plasmas for higher confinement and stability, a real-time control system of the minimum of the safety factor (qmin) using the off-axis current drive has been developed. The off-axis current drive can raise the safety factor in the centre and help to avoid instability that limits the performance of the plasma. The system controls the injection power of lower-hybrid waves, and hence its off-axis driven current in order to control qmin. The real-time control of qmin is demonstrated in a high-β plasma, where qmin follows the temporally changing reference qmin,ref from 1.3 to 1.7. Applying the control to another high-β discharge (βN = 1.7, βp = 1.5) with m/n = 2/1 neo-classical tearing mode (NTM), qmin was raised above 2 and the NTM was suppressed. The stored energy increased by 16% with the NTM suppressed, since the resonant rational surface was eliminated. For the future use for current profile control, current density profile for off-axis neutral beam current drive (NBCD) is for the first time measured, using the motional Stark effect diagnostic. Spatially localized NBCD profile was clearly observed at the normalized minor radius ρ of about 0.6-0.8. The location was also confirmed by multi-chordal neutron emission profile measurement. The total amount of the measured beam driven current was consistent with the theoretical calculation using the ACCOME code. The CD location in the calculation was inward shifted than the measurement.

  12. Role of the lower hybrid spectrum in the current drive modeling for DEMO scenarios

    NASA Astrophysics Data System (ADS)

    Cardinali, A.; Castaldo, C.; Cesario, R.; Santini, F.; Amicucci, L.; Ceccuzzi, S.; Galli, A.; Mirizzi, F.; Napoli, F.; Panaccione, L.; Schettini, G.; Tuccillo, A. A.

    2017-07-01

    The active control of the radial current density profile is one of the major issues of thermonuclear fusion energy research based on magnetic confinement. The lower hybrid current drive could in principle be used as an efficient tool. However, previous understanding considered the electron temperature envisaged in a reactor at the plasma periphery too large to allow penetration of the coupled radio frequency (RF) power due to strong Landau damping. In this work, we present new numerical results based on quasilinear theory, showing that the injection of power spectra with different {n}// widths of the main lobe produce an RF-driven current density profile spanning most of the outer radial half of the plasma ({n}// is the refractive index in a parallel direction to the confinement magnetic field). Plasma kinetic profiles envisaged for the DEMO reactor are used as references. We demonstrate the robustness of the modeling results concerning the key role of the spectral width in determining the lower hybrid-driven current density profile. Scans of plasma parameters are extensively carried out with the aim of excluding the possibility that any artefact of the utilised numerical modeling would produce any novelty. We neglect here the parasitic effect of spectral broadening produced by linear scattering due to plasma density fluctuations, which mainly occurs for low magnetic field devices. This effect will be analyzed in other work that completes the report on the present breakthrough.

  13. Determination of current and rotational transform profiles in a current-carrying stellarator using soft x-ray emissivity measurements

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ma, X.; Cianciosa, M. R.; Ennis, D. A.

    In this research, collimated soft X-ray (SXR) emissivity measurements from multi-channel cameras on the Compact Toroidal Hybrid (CTH) tokamak/torsatron device are incorporated in the 3D equilibrium reconstruction code V3FIT to reconstruct the shape of flux surfaces and infer the current distribution within the plasma. Equilibrium reconstructions of sawtoothing plasmas that use data from both SXR and external magnetic diagnostics show the central safety factor to be near unity under the assumption that SXR iso-emissivity contours lie on magnetic flux surfaces. The reconstruction results are consistent with those using the external magnetic data and a constraint on the location of qmore » = 1 surfaces determined from the sawtooth inversion surface extracted from SXR brightness profiles. The agreement justifies the use of approximating SXR emission as a flux function in CTH, at least within the core of the plasma, subject to the spatial resolution of the SXR diagnostics. Lastly, this improved reconstruction of the central current density indicates that the current profile peakedness decreases with increasing external transform and that the internal inductance is not a relevant measure of how peaked the current profile is in hybrid discharges.« less

  14. Determination of current and rotational transform profiles in a current-carrying stellarator using soft x-ray emissivity measurements

    NASA Astrophysics Data System (ADS)

    Ma, X.; Cianciosa, M. R.; Ennis, D. A.; Hanson, J. D.; Hartwell, G. J.; Herfindal, J. L.; Howell, E. C.; Knowlton, S. F.; Maurer, D. A.; Traverso, P. J.

    2018-01-01

    Collimated soft X-ray (SXR) emissivity measurements from multi-channel cameras on the Compact Toroidal Hybrid (CTH) tokamak/torsatron device are incorporated in the 3D equilibrium reconstruction code V3FIT to reconstruct the shape of flux surfaces and infer the current distribution within the plasma. Equilibrium reconstructions of sawtoothing plasmas that use data from both SXR and external magnetic diagnostics show the central safety factor to be near unity under the assumption that SXR iso-emissivity contours lie on magnetic flux surfaces. The reconstruction results are consistent with those using the external magnetic data and a constraint on the location of q = 1 surfaces determined from the sawtooth inversion surface extracted from SXR brightness profiles. The agreement justifies the use of approximating SXR emission as a flux function in CTH, at least within the core of the plasma, subject to the spatial resolution of the SXR diagnostics. This improved reconstruction of the central current density indicates that the current profile peakedness decreases with increasing external transform and that the internal inductance is not a relevant measure of how peaked the current profile is in hybrid discharges.

  15. Determination of current and rotational transform profiles in a current-carrying stellarator using soft x-ray emissivity measurements

    DOE PAGES

    Ma, X.; Cianciosa, M. R.; Ennis, D. A.; ...

    2018-01-31

    In this research, collimated soft X-ray (SXR) emissivity measurements from multi-channel cameras on the Compact Toroidal Hybrid (CTH) tokamak/torsatron device are incorporated in the 3D equilibrium reconstruction code V3FIT to reconstruct the shape of flux surfaces and infer the current distribution within the plasma. Equilibrium reconstructions of sawtoothing plasmas that use data from both SXR and external magnetic diagnostics show the central safety factor to be near unity under the assumption that SXR iso-emissivity contours lie on magnetic flux surfaces. The reconstruction results are consistent with those using the external magnetic data and a constraint on the location of qmore » = 1 surfaces determined from the sawtooth inversion surface extracted from SXR brightness profiles. The agreement justifies the use of approximating SXR emission as a flux function in CTH, at least within the core of the plasma, subject to the spatial resolution of the SXR diagnostics. Lastly, this improved reconstruction of the central current density indicates that the current profile peakedness decreases with increasing external transform and that the internal inductance is not a relevant measure of how peaked the current profile is in hybrid discharges.« less

  16. Current sheet in plasma as a system with a controlling parameter

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fridman, Yu. A., E-mail: yulya-fridman@yandex.ru; Chukbar, K. V., E-mail: Chukbar-KV@nrcki.ru

    2015-08-15

    A simple kinetic model describing stationary solutions with bifurcated and single-peaked current density profiles of a plane electron beam or current sheet in plasma is presented. A connection is established between the two-dimensional constructions arising in terms of the model and the one-dimensional considerations by Bernstein−Greene−Kruskal facilitating the reconstruction of the distribution function of trapped particles when both the profile of the electric potential and the free particles distribution function are known.

  17. Electron temperature response to ECRH on FTU tokamak in transient conditions.

    NASA Astrophysics Data System (ADS)

    Jacchia, A.; Bruschi, A.; Cirant, S.; Granucci, G.; Sozzi, C.; de Luca, F.; Amadeo, P.; Bracco, G.; Tudisco, O.

    2001-10-01

    Steady-state electron heat transport analysis of FTU high density plasmas under Electron Cyclotron Heating (ECRH) shows "stiff" electron temperature profiles [1,2,3]. Plasma response to off-axis EC heating, in fact, exibits a lower limit to electron temperature gradient length, Lc , below which electron thermal conductivity switches to higher values. Stiffness, however, is attenuated in the plasma core of saw-tooth free discharges with flat-hollow temperature profile and during current ramp-up [3,4,5], in which cases the temperature gradient length can be brought to very low values by means of on-axis ECH. Steady and current ramp-up discharges probed by steady and modulated ECH are analyzed in terms of stiffnes. Critical gradient length dependence on local features of computed current density profile is discussed. [1] Sozzi, C. et al., Paper EXP5/13, Plasma Phys. Contr. Fus. Res., Proc.18th IAEA Conf., Sorrento, 2000. [2] Jacchia, A. et al. Topical Conference on Radio Frequency Power in Plasmas, Oxnard, USA, (2001). [3] Cirant, S. et al. Topical Conference on Radio Frequency Power in Plasmas, Oxnard, USA, (2001). [4] Sozzi, C. et al., EPS, Madeira 2001. [5] Bracco, G. et al.,Plasma Phys. Contr. Fus. Res., Proc.18th IAEA Conf., Sorrento, 2000.

  18. Lower hybrid current drive in experiments for transport barriers at high βN of JET (Joint European Torus)

    NASA Astrophysics Data System (ADS)

    Cesario, R. C.; Castaldo, C.; Fonseca, A.; De Angelis, R.; Parail, V.; Smeulders, P.; Beurskens, M.; Brix, M.; Calabrò, G.; De Vries, P.; Mailloux, J.; Pericoli, V.; Ravera, G.; Zagorski, R.

    2007-09-01

    LHCD has been used in JET experiments aimed at producing internal transport barriers (ITBs) in highly triangular plasmas (δ≈0.4) at high βN (up to 3) for steady-state application. The LHCD is a potentially valuable tool for (i) modifying the target q-profile, which can help avoid deleterious MHD modes and favour the formation of ITBs, and (ii) contributing to the non-inductive current drive required to prolong such plasma regimes. The q-profile evolution has been simulated during the current ramp-up phase for such a discharge (B0 = 2.3 T, IP = 1.5 MA) where 2 MW of LHCD has been coupled. The JETTO code was used taking measured plasma profiles, and the LHCD profile modeled by the LHstar code. The results are in agreement with MSE measurements and indicate the importance of the elevated electron temperature due to LHCD, as well as the driven current. During main heating with 18 MW of NBI and 3 MW of ICRH the bootstrap current density at the edge also becomes large, consistently with the observed reduction of the local turbulence and of the MHD activity. JETTO modelling suggests that the bootstrap current can reduce the magnetic shear (sh) at large radius, potentially affecting the MHD stability and turbulence behaviour in this region. Keywords: lower hybrid current drive (LHCD), bootstrap current, q (safety factor) and shear (sh) profile evolutions.

  19. Development of high poloidal beta, steady-state scenario with ITER-like tungsten divertor on EAST

    NASA Astrophysics Data System (ADS)

    Garofalo, A. M.; Gong, X. Z.; Qian, J.; Chen, J.; Li, G.; Li, K.; Li, M. H.; Zhai, X.; Bonoli, P.; Brower, D.; Cao, L.; Cui, L.; Ding, S.; Ding, W. X.; Guo, W.; Holcomb, C.; Huang, J.; Hyatt, A.; Lanctot, M.; Lao, L. L.; Liu, H.; Lyu, B.; McClenaghan, J.; Peysson, Y.; Ren, Q.; Shiraiwa, S.; Solomon, W.; Zang, Q.; Wan, B.

    2017-07-01

    Recent experiments on EAST have achieved the first long pulse H-mode (61 s) with zero loop voltage and an ITER-like tungsten divertor, and have demonstrated access to broad plasma current profiles by increasing the density in fully-noninductive lower hybrid current-driven discharges. These long pulse discharges reach wall thermal and particle balance, exhibit stationary good confinement (H 98y2 ~ 1.1) with low core electron transport, and are only possible with optimal active cooling of the tungsten armors. In separate experiments, the electron density was systematically varied in order to study its effect on the deposition profile of the external lower hybrid current drive (LHCD), while keeping the plasma in fully-noninductive conditions and with divertor strike points on the tungsten divertor. A broadening of the current profile is found, as indicated by lower values of the internal inductance at higher density. A broad current profile is attractive because, among other reasons, it enables internal transport barriers at large minor radius, leading to improved confinement as shown in companion DIII-D experiments. These experiments strengthen the physics basis for achieving high performance, steady state discharges in future burning plasmas.

  20. Development of high poloidal beta, steady-state scenario with ITER-like tungsten divertor on EAST

    DOE PAGES

    Garofalo, Andrea M.; Gong, X. Z.; Qian, J.; ...

    2017-06-07

    Recent experiments on EAST have achieved the first long pulse H-mode (61 s) with zero loop voltage and an ITER-like tungsten divertor, and have demonstrated access to broad plasma current profiles by increasing the density in fully-noninductive lower hybrid current-driven discharges. These long pulse discharges reach wall thermal and particle balance, exhibit stationary good confinement (H 98y2~1.1) with low core electron transport, and are only possible with optimal active cooling of the tungsten armors. In separate experiments, the electron density was systematically varied in order to study its effect on the deposition profile of the external lower hybrid current drivemore » (LHCD), while keeping the plasma in fully-noninductive conditions and with divertor strike points on the tungsten divertor. A broadening of the current profile is found, as indicated by lower values of the internal inductance at higher density. A broad current profile is attractive because, among other reasons, it enables internal transport barriers at large minor radius, leading to improved confinement as shown in companion DIII-D experiments. These experiments strengthen the physics basis for achieving high performance, steady state discharges in future burning plasmas.« less

  1. Bootstrap current in a tokamak

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kessel, C.E.

    1994-03-01

    The bootstrap current in a tokamak is examined by implementing the Hirshman-Sigmar model and comparing the predicted current profiles with those from two popular approximations. The dependences of the bootstrap current profile on the plasma properties are illustrated. The implications for steady state tokamaks are presented through two constraints; the pressure profile must be peaked and {beta}{sub p} must be kept below a critical value.

  2. Diagnostics for real-time plasma control in PBX-M

    NASA Astrophysics Data System (ADS)

    Kaita, R.; Batha, S.; Bell, R. E.; Bernabei, S.; Hatcher, R.; Kozub, T.; Kugel, H.; Levinton, F.; Okabayashi, M.; Sesnic, S.; von Goeler, S.; Zolfaghari, A.; PBX-M Group

    1995-01-01

    An important issue for future tokamaks is real-time plasma control for the avoidance of magnetohydrodynamic instabilities and other applications that require detailed plasma profile and fluctuation data. Although measurements from diagnostics providing this information require significantly more processing than magnetic flux data, recent advancements could make them practical for adjusting operational settings for plasma heating and current drive systems as well as field coil currents. On the Princeton Beta Experiment-Modification (PBX-M), the lower hybrid current drive phasing can be varied during a plasma shot using digitally programmable ferrite phase shifters, and neural beam functions can be fully computer controlled. PBX-M diagnostics that may be used for control purposes include motional Stark-effect polarimetry for magnetic field pitch angle profiles, soft x-ray arrays for plasma position control and the separation of βp from li, hard x-ray detectors for energetic electron distributions, a multichannel electron cyclotron emission radiometer for ballooning mode identification, and passive plate eddy current monitors for kink stabilization. We will describe the present status of these systems on PBX-M, and discuss their suitability for feedback applications.

  3. Investigation of the plasma shaping effects on the H-mode pedestal structure using coupled kinetic neoclassical/MHD stability simulations

    NASA Astrophysics Data System (ADS)

    Pankin, A. Y.; Rafiq, T.; Kritz, A. H.; Park, G. Y.; Snyder, P. B.; Chang, C. S.

    2017-06-01

    The effects of plasma shaping on the H-mode pedestal structure are investigated. High fidelity kinetic simulations of the neoclassical pedestal dynamics are combined with the magnetohydrodynamic (MHD) stability conditions for triggering edge localized mode (ELM) instabilities that limit the pedestal width and height in H-mode plasmas. The neoclassical kinetic XGC0 code [Chang et al., Phys. Plasmas 11, 2649 (2004)] is used in carrying out a scan over plasma elongation and triangularity. As plasma profiles evolve, the MHD stability limits of these profiles are analyzed with the ideal MHD ELITE code [Snyder et al., Phys. Plasmas 9, 2037 (2002)]. Simulations with the XGC0 code, which includes coupled ion-electron dynamics, yield predictions for both ion and electron pedestal profiles. The differences in the predicted H-mode pedestal width and height for the DIII-D discharges with different elongation and triangularities are discussed. For the discharges with higher elongation, it is found that the gradients of the plasma profiles in the H-mode pedestal reach semi-steady states. In these simulations, the pedestal slowly continues to evolve to higher pedestal pressures and bootstrap currents until the peeling-ballooning stability conditions are satisfied. The discharges with lower elongation do not reach the semi-steady state, and ELM crashes are triggered at earlier times. The plasma elongation is found to have a stronger stabilizing effect than the plasma triangularity. For the discharges with lower elongation and lower triangularity, the ELM frequency is large, and the H-mode pedestal evolves rapidly. It is found that the temperature of neutrals in the scrape-off-layer (SOL) region can affect the dynamics of the H-mode pedestal buildup. However, the final pedestal profiles are nearly independent of the neutral temperature. The elongation and triangularity affect the pedestal widths of plasma density and electron temperature profiles differently. This provides a new mechanism of controlling the pedestal bootstrap current and the pedestal stability.

  4. Investigation of the plasma shaping effects on the H-mode pedestal structure using coupled kinetic neoclassical/MHD stability simulations

    DOE PAGES

    Pankin, A. Y.; Rafiq, T.; Kritz, A. H.; ...

    2017-06-08

    The effects of plasma shaping on the H-mode pedestal structure are investigated. High fidelity kinetic simulations of the neoclassical pedestal dynamics are combined with the magnetohydrodynamic (MHD) stability conditions for triggering edge localized mode (ELM) instabilities that limit the pedestal width and height in H-mode plasmas. We use the neoclassical kinetic XGC0 code [Chang et al., Phys. Plasmas 11, 2649 (2004)] to carry out a scan over plasma elongation and triangularity. As plasma profiles evolve, the MHD stability limits of these profiles are analyzed with the ideal MHD ELITE code [Snyder et al., Phys. Plasmas 9, 2037 (2002)]. In simulationsmore » with the XGC0 code, which includes coupled ion-electron dynamics, yield predictions for both ion and electron pedestal profiles. The differences in the predicted H-mode pedestal width and height for the DIII-D discharges with different elongation and triangularities are discussed. For the discharges with higher elongation, it is found that the gradients of the plasma profiles in the H-mode pedestal reach semi-steady states. In these simulations, the pedestal slowly continues to evolve to higher pedestal pressures and bootstrap currents until the peeling-ballooning stability conditions are satisfied. The discharges with lower elongation do not reach the semi-steady state, and ELM crashes are triggered at earlier times. The plasma elongation is found to have a stronger stabilizing effect than the plasma triangularity. For the discharges with lower elongation and lower triangularity, the ELM frequency is large, and the H-mode pedestal evolves rapidly. It is found that the temperature of neutrals in the scrape-off-layer (SOL) region can affect the dynamics of the H-mode pedestal buildup. But the final pedestal profiles are nearly independent of the neutral temperature. The elongation and triangularity affect the pedestal widths of plasma density and electron temperature profiles differently. This provides a new mechanism of controlling the pedestal bootstrap current and the pedestal stability.« less

  5. Investigation of the plasma shaping effects on the H-mode pedestal structure using coupled kinetic neoclassical/MHD stability simulations

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pankin, A. Y.; Rafiq, T.; Kritz, A. H.

    The effects of plasma shaping on the H-mode pedestal structure are investigated. High fidelity kinetic simulations of the neoclassical pedestal dynamics are combined with the magnetohydrodynamic (MHD) stability conditions for triggering edge localized mode (ELM) instabilities that limit the pedestal width and height in H-mode plasmas. We use the neoclassical kinetic XGC0 code [Chang et al., Phys. Plasmas 11, 2649 (2004)] to carry out a scan over plasma elongation and triangularity. As plasma profiles evolve, the MHD stability limits of these profiles are analyzed with the ideal MHD ELITE code [Snyder et al., Phys. Plasmas 9, 2037 (2002)]. In simulationsmore » with the XGC0 code, which includes coupled ion-electron dynamics, yield predictions for both ion and electron pedestal profiles. The differences in the predicted H-mode pedestal width and height for the DIII-D discharges with different elongation and triangularities are discussed. For the discharges with higher elongation, it is found that the gradients of the plasma profiles in the H-mode pedestal reach semi-steady states. In these simulations, the pedestal slowly continues to evolve to higher pedestal pressures and bootstrap currents until the peeling-ballooning stability conditions are satisfied. The discharges with lower elongation do not reach the semi-steady state, and ELM crashes are triggered at earlier times. The plasma elongation is found to have a stronger stabilizing effect than the plasma triangularity. For the discharges with lower elongation and lower triangularity, the ELM frequency is large, and the H-mode pedestal evolves rapidly. It is found that the temperature of neutrals in the scrape-off-layer (SOL) region can affect the dynamics of the H-mode pedestal buildup. But the final pedestal profiles are nearly independent of the neutral temperature. The elongation and triangularity affect the pedestal widths of plasma density and electron temperature profiles differently. This provides a new mechanism of controlling the pedestal bootstrap current and the pedestal stability.« less

  6. MHD and resonant instabilities in JT-60SA during current ramp-up with off-axis N-NB injection

    NASA Astrophysics Data System (ADS)

    Bierwage, A.; Toma, M.; Shinohara, K.

    2017-12-01

    The excitation of magnetohydrodynamic (MHD) and resonant instabilities and their effect on the plasma profiles during the current ramp-up phase of a beam-driven JT-60SA tokamak plasma is studied using the MHD-PIC hybrid code MEGA. In the simple scenario considered, the plasma is only driven by one negative-ion-based neutral beam, depositing 500 keV deuterons at 5 MW power off-axis at about mid-radius. The beam injection starts half-way in the ramp-up phase. Within 1 s, the beam-driven plasma current and fast ion pressure produce a configuration that is strongly unstable to rapidly growing MHD and resonant modes. Using MEGA, modes with low toroidal mode numbers in the range n = 1-4 are examined in detail and shown to cause substantial changes in the plasma profiles. The necessity to develop reduced models and incorporate the effects of such instabilities in integrated codes used to simulate the evolution of entire plasma discharges is discussed.

  7. Plasma MRI Experiments at UW-Madison

    NASA Astrophysics Data System (ADS)

    Flanagan, K.; Clark, M.; Desangles, V.; Siller, R.; Wallace, J.; Weisberg, D.; Forest, C. B.

    2015-11-01

    Experiments for driving Keplerian-like flow profiles on both the Plasma Couette Experiment Upgrade (PCX-U) and the Wisconsin Plasma Astrophysics Laboratory (WiPAL) user facility are described. Instead of driving flow at the boundaries, as is typical in many liquid metal Couette experiments, a global drive is implemented. A large radial current is drawn across a small axial field generating torque across the whole profile. This global electrically driven flow is capable of producing profiles similar to Keplerian flow. PCX-U has been purposely constructed for MRI experiments, while similar experiments on the WiPAL device show the versatility of the user facility and provide a larger plasma volume. Numerical calculations show the predicted parameter spaces for exciting the MRI in these plasmas and the equilibrium flow profiles expected. In both devices, relevant MRI parameters appear to be within reach of typical operating characteristics.

  8. Development of Integrated Magnetic and Kinetic Control-oriented Transport Model for q-profile Response Prediction in EAST Discharges

    NASA Astrophysics Data System (ADS)

    Wang, Hexiang; Schuster, Eugenio; Rafiq, Tariq; Kritz, Arnold; Ding, Siye

    2016-10-01

    Extensive research has been conducted to find high-performance operating scenarios characterized by high fusion gain, good confinement, plasma stability and possible steady-state operation. A key plasma property that is related to both the stability and performance of these advanced plasma scenarios is the safety factor profile. A key component of the EAST research program is the exploration of non-inductively driven steady-state plasmas with the recently upgraded heating and current drive capabilities that include lower hybrid current drive and neutral beam injection. Anticipating the need for tight regulation of the safety factor profile in these plasma scenarios, a first-principles-driven (FPD)control-oriented model is proposed to describe the safety factor profile evolution in EAST in response to the different actuators. The TRANSP simulation code is employed to tailor the FPD model to the EAST tokamak geometry and to convert it into a form suitable for control design. The FPD control-oriented model's prediction capabilities are demonstrated by comparing predictions with experimental data from EAST. Supported by the US DOE under DE-SC0010537,DE-FG02-92ER54141 and DE-SC0013977.

  9. High current ion source

    DOEpatents

    Brown, Ian G.; MacGill, Robert A.; Galvin, James E.

    1990-01-01

    An ion source utilizing a cathode and anode for producing an electric arc therebetween. The arc is sufficient to vaporize a portion of the cathode to form a plasma. The plasma leaves the generation region and expands through another regon. The density profile of the plasma may be flattened using a magnetic field formed within a vacuum chamber. Ions are extracted from the plasma to produce a high current broad on beam.

  10. GPU based 3D feature profile simulation of high-aspect ratio contact hole etch process under fluorocarbon plasmas

    NASA Astrophysics Data System (ADS)

    Chun, Poo-Reum; Lee, Se-Ah; Yook, Yeong-Geun; Choi, Kwang-Sung; Cho, Deog-Geun; Yu, Dong-Hun; Chang, Won-Seok; Kwon, Deuk-Chul; Im, Yeon-Ho

    2013-09-01

    Although plasma etch profile simulation has been attracted much interest for developing reliable plasma etching, there still exist big gaps between current research status and predictable modeling due to the inherent complexity of plasma process. As an effort to address this issue, we present 3D feature profile simulation coupled with well-defined plasma-surface kinetic model for silicon dioxide etching process under fluorocarbon plasmas. To capture the realistic plasma surface reaction behaviors, a polymer layer based surface kinetic model was proposed to consider the simultaneous polymer deposition and oxide etching. Finally, the realistic plasma surface model was used for calculation of speed function for 3D topology simulation, which consists of multiple level set based moving algorithm, and ballistic transport module. In addition, the time consumable computations in the ballistic transport calculation were improved drastically by GPU based numerical computation, leading to the real time computation. Finally, we demonstrated that the surface kinetic model could be coupled successfully for 3D etch profile simulations in high-aspect ratio contact hole plasma etching.

  11. Transport simulation of EAST long-pulse H-mode discharge with integrated modeling

    NASA Astrophysics Data System (ADS)

    Wu, M. Q.; Li, G. Q.; Chen, J. L.; Du, H. F.; Gao, X.; Ren, Q. L.; Li, K.; Chan, Vincent; Pan, C. K.; Ding, S. Y.; Jian, X.; Zhu, X.; Lian, H.; Qian, J. P.; Gong, X. Z.; Zang, Q.; Duan, Y. M.; Liu, H. Q.; Lyu, B.

    2018-04-01

    In the 2017 EAST experimental campaign, a steady-state long-pulse H-mode discharge lasting longer than 100 s has been obtained using only radio frequency heating and current drive, and the confinement quality is slightly better than standard H-mode, H98y2 ~ 1.1, with stationary peaked electron temperature profiles. Integrated modeling of one long-pulse H-mode discharge in the 2016 EAST experimental campaign has been performed with equilibrium code EFIT, and transport codes TGYRO and ONETWO under integrated modeling framework OMFIT. The plasma current is fully-noninductively driven with a combination of ~2.2 MW LHW, ~0.3 MW ECH and ~1.1 MW ICRF. Time evolution of the predicted electron and ion temperature profiles through integrated modeling agree closely with that from measurements. The plasma current (I p ~ 0.45 MA) and electron density are kept constantly. A steady-state is achieved using integrated modeling, and the bootstrap current fraction is ~28%, the RF drive current fraction is ~72%. The predicted current density profile matches the experimental one well. Analysis shows that electron cyclotron heating (ECH) makes large contribution to the plasma confinement when heating in the core region while heating in large radius does smaller improvement, also a more peaked LHW driven current profile is got when heating in the core. Linear analysis shows that the high-k modes instability (electron temperature gradient driven modes) is suppressed in the core region where exists weak electron internal transport barriers. The trapped electron modes dominates in the low-k region, which is mainly responsible for driving the electron energy flux. It is found that the ECH heating effect is very local and not the main cause to sustained the good confinement, the peaked current density profile has the most important effect on plasma confinement improvement. Transport analysis of the long-pulse H-mode experiments on EAST will be helpful to build future experiments.

  12. Fivefold confinement time increase in the Madison Symmetric Torus using inductive poloidal current drive

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Stoneking, M.R.; Lanier, N.E.; Prager, S.C.

    1996-12-01

    Current profile control is employed in the Madison Symmetric Torus reversed field pinch to reduce the magnetic fluctuations responsible for anomalous transport. An inductive poloidal electric field pulse is applied in the sense to flatten the parallel current profile, reducing the dynamo fluctuation amplitude required to sustain the equilibrium. This technique demonstrates a substantial reduction in fluctuation amplitude (as much as 50%), and improvement in energy confinement (from 1 ms to 5 ms); a record low fluctuation (0.8%) and record high temperature (615 eV) for this device were observed simultaneously during current drive experiments. Plasma beta increases by 50% andmore » the Ohmic input power is three times lower. Particle confinement improves and plasma impurity contamination is reduced. The results of the transient current drive experiments provide motivation for continuing development of steady-state current profile control strategies for the reversed field pinch.« less

  13. Drive Beam Shaping and Witness Bunch Generation for the Plasma Wakefield Accelerator

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    England, R. J.; Frederico, J.; Hogan, M. J.

    2010-11-04

    High transformer ratio operation of the plasma wake field accelerator requires a tailored drive beam current profile followed by a short witness bunch. We discuss techniques for generating the requisite dual bunches and for obtaining the desired drive beam profile, with emphasis on the FACET experiment at SLAC National Accelerator Laboratory.

  14. Characterization of Electron Temperature and Density Profiles of Plasmas Produced by Nike KrF Laser for Laser Plasma Instability (LPI) Research

    NASA Astrophysics Data System (ADS)

    Oh, Jaechul; Weaver, J. L.; Phillips, L.; Obenschain, S. P.; Schmitt, A. J.; Kehne, D. M.; Chan, L.-Y.; Serlin, V.

    2011-10-01

    Previous experiments with Nike KrF laser (λ = 248 nm , Δν ~ 1 THz) observed LPI signatures near quarter critical density (nc / 4) in CH plasmas, however, detailed measurement of the temperature (Te) and density (ne) profiles was missing. The current Nike LPI campaign will perform experimental determination of the plasma profiles. A side-on grid imaging refractometer (GIR) is the main diagnostic to resolve Te and ne in space taking 2D snapshots of probe laser (λ = 266 nm , Δt = 8 psec) beamlets (50 μm spacing) refracted by the plasma at laser peak time. Ray tracing of the beamlets through hydrodynamically simulated (FASTRAD3D) plasma profiles estimates the refractometer may access densities up to ~ 0 . 2nc . With the measured Te and ne profiles in the plasma corona, we will discuss analysis of light data radiated from the plasmas in spectral ranges relevant to two plasmon decay and convective Raman instabilities. Validity of the (Te ,ne) data will also be discussed for the thermal transport study. Work supported by DoE/NNSA and ONR and performed at NRL.

  15. Nonlinear Simulation of DIII-D Plasma and Poloidal Systems Using DINA and Simulink

    NASA Astrophysics Data System (ADS)

    Walker, M. L.; Leuer, J. A.; Deranian, R. D.; Humphreys, D. A.; Khayrutdinov, R. R.

    2002-11-01

    Hardware-in-the-loop simulation capability was developed previously for poloidal shape control testing using Matlab Simulink [1]. This has been upgraded by replacing a linearized plasma model with the DINA nonlinear plasma evolution code [2]. In addition to its use for shape control studies, this new capability will allow study of current profile control using the DINA model of electron cyclotron current drive (ECCD) and current profile information soon to be available from the Plasma Control System (PCS) real time EFIT [3] calculation. We describe the incorporation of DINA into the Simulink DIII-D tokamak systems model and results of validating this combined model against DIII-D data. \\vspace0.1em [1] J.A. Leuer, et al., 18th IEEE/NPSS SOFE (1999), p. 531. [2] R.R. Khayrutdinov, V.E. Lukash, J. Comput. Phys. 109, 193 (1993). [3] J.R. Ferron, et al., Nucl. Fusion 38, 1055 (1988).

  16. Simulation of profile evolution from ramp-up to ramp-down and optimization of tokamak plasma termination with the RAPTOR code

    NASA Astrophysics Data System (ADS)

    Teplukhina, A. A.; Sauter, O.; Felici, F.; Merle, A.; Kim, D.; the TCV Team; the ASDEX Upgrade Team; the EUROfusion MST1 Team

    2017-12-01

    The present work demonstrates the capabilities of the transport code RAPTOR as a fast and reliable simulator of plasma profiles for the entire plasma discharge, i.e. from ramp-up to ramp-down. This code focuses, at this stage, on the simulation of electron temperature and poloidal flux profiles using prescribed equilibrium and some kinetic profiles. In this work we extend the RAPTOR transport model to include a time-varying plasma equilibrium geometry and verify the changes via comparison with ATSRA code simulations. In addition a new ad hoc transport model based on constant gradients and suitable for simulations of L-H and H-L mode transitions has been incorporated into the RAPTOR code and validated with rapid simulations of the time evolution of the safety factor and the electron temperature over the entire AUG and TCV discharges. An optimization procedure for the plasma termination phase has also been developed during this work. We define the goal of the optimization as ramping down the plasma current as fast as possible while avoiding any disruptions caused by reaching physical or technical limits. Our numerical study of this problem shows that a fast decrease of plasma elongation during current ramp-down can help in reducing plasma internal inductance. An early transition from H- to L-mode allows us to reduce the drop in poloidal beta, which is also important for plasma MHD stability and control. This work shows how these complex nonlinear interactions can be optimized automatically using relevant cost functions and constraints. Preliminary experimental results for TCV are demonstrated.

  17. Experimental validation of a Lyapunov-based controller for the plasma safety factor and plasma pressure in the TCV tokamak

    NASA Astrophysics Data System (ADS)

    Mavkov, B.; Witrant, E.; Prieur, C.; Maljaars, E.; Felici, F.; Sauter, O.; the TCV-Team

    2018-05-01

    In this paper, model-based closed-loop algorithms are derived for distributed control of the inverse of the safety factor profile and the plasma pressure parameter β of the TCV tokamak. The simultaneous control of the two plasma quantities is performed by combining two different control methods. The control design of the plasma safety factor is based on an infinite-dimensional setting using Lyapunov analysis for partial differential equations, while the control of the plasma pressure parameter is designed using control techniques for single-input and single-output systems. The performance and robustness of the proposed controller is analyzed in simulations using the fast plasma transport simulator RAPTOR. The control is then implemented and tested in experiments in TCV L-mode discharges using the RAPTOR model predicted estimates for the q-profile. The distributed control in TCV is performed using one co-current and one counter-current electron cyclotron heating actuation.

  18. A phenomenological model for orificed hollow cathodes. Ph.D. Thesis, 1 Dec. 1981 - 1 Dec. 1982; [electrostatic thruster

    NASA Technical Reports Server (NTRS)

    Siegfried, D. E.

    1982-01-01

    A quartz hollow tube cathode was used to determine the operating conditions within a mercury orificed hollow cathode. Insert temperature profiles, cathode current distributions, plasma properties profile, and internal pressure-mass flow rate results are summarized and used in a phenomenological model which qualitatively describes electron emission and plasma production processes taking place within the cathode. By defining an idealized ion production region within which most of the plasma processes are concentrated, this model is expressed analytically as a simple set of equations which relate cathode dimensions and specifiable operating conditions, such as mass flow rate and discharge current, to such important parameters as emission surface temperature and internal plasma properties. Key aspects of the model are examined.

  19. EAST kinetic equilibrium reconstruction combining with Polarimeter-Interferometer internal measurement constraints

    NASA Astrophysics Data System (ADS)

    Lian, H.; Liu, H. Q.; Li, K.; Zou, Z. Y.; Qian, J. P.; Wu, M. Q.; Li, G. Q.; Zeng, L.; Zang, Q.; Lv, B.; Jie, Y. X.; EAST Team

    2017-12-01

    Plasma equilibrium reconstruction plays an important role in the tokamak plasma research. With a high temporal and spatial resolution, the POlarimeter-INTerferometer (POINT) system on EAST has provided effective measurements for 102s H-mode operation. Based on internal Faraday rotation measurements provided by the POINT system, the equilibrium reconstruction with a more accurate core current profile constraint has been demonstrated successfully on EAST. Combining other experimental diagnostics and external magnetic fields measurement, the kinetic equilibrium has also been reconstructed on EAST. Take the pressure and edge current information from kinetic EFIT into the equilibrium reconstruction with Faraday rotation constraint, the new equilibrium reconstruction not only provides a more accurate internal current profile but also contains edge current and pressure information. One time slice result using new kinetic equilibrium reconstruction with POINT data constraints is demonstrated in this paper and the result shows there is a reversed shear of q profile and the pressure profile is also contained. The new improved equilibrium reconstruction is greatly helpful to the future theoretical analysis.

  20. Study of neoclassical effects on the pedestal structure in ELMy H-mode plasmas

    NASA Astrophysics Data System (ADS)

    Pankin, A. Y.; Bateman, G.; Kritz, A. H.; Rafiq, T.; Park, G. Y.; Ku, S.; Chang, C. S.; Snyder, P. B.

    2009-11-01

    The neoclassical effects on the H-mode pedestal structure are investigated in this study. First principles' kinetic simulations of the neoclassical pedestal dynamics are combined with the MHD stability conditions for triggering ELM crashes that limit the pedestal width and height in H-mode plasmas. The neoclassical kinetic XGC0 code [1] is used to produce systematic scans over plasma parameters including plasma current, elongation, and triangularity. As plasma profiles evolve, the MHD stability limits of these profiles are analyzed with the ideal MHD stability ELITE code [2]. The scalings of the pedestal width and height are presented as a function of the scanned plasma parameters. Simulations with the XGC0 code, which include coupled ion-electron dynamics, yield predictions for both ion and electron pedestal profiles. Differences in the electron and ion pedestal scalings are investigated. [1] C.S. Chang et al, Phys. Plasmas 11 (2004) 2649. [2] P.B. Snyder et al, Phys. Plasmas, 9 (2002) 2037.

  1. RF current profile control studies in the alcator C-mod tokamak

    NASA Astrophysics Data System (ADS)

    Bonoli, P. T.; Porkolab, M.; Wukitch, S. J.; Bernabei, S.; Kaita, R.; Mikkelsen, D.; Phillips, C. K.; Schilling, G.

    1999-09-01

    Time dependent calculations of lower hybrid (LH) current profile control in Alcator C-Mod have been done using the TRANSP [1], FPPRF [2], and LSC [3] codes. Up to 3 MW of LH current drive power was applied in plasmas with high power ICRF minority heating (PICH=1.8-3 MW) and fast current ramp up. Using the experimentally measured temperature profiles, off-axis current generation resulted in nonmonotonic q-profiles with qmin~=1.6. Self-consistent effects of off-axis electron heating by the LH power were also included in the analysis and significant broadening of the electron temperature profile was found with qmin>~2 and a larger shear reversal radius.

  2. Particle in cell simulation of instabilities in space and astrophysical plasmas

    NASA Astrophysics Data System (ADS)

    Tonge, John William

    Several plasma instabilities relevant to space physics are investigated using the parallel PIC plasma simulation code P3arsec. This thesis addresses electrostatic micro-instabilities relevant to ion ring distributions, proceeds to electromagnetic micro-instabilities pertinent to streaming plasmas, and then to the stability of a plasma held in the field of a current rod. The physical relevance of each of these instabilities is discussed, a phenomenological description is given, and analytic and simulation results are presented and compared. Instability of a magnetized plasma with a portion of the ions in a velocity ring distribution around the magnetic field is investigated using simulation and analytic theory. The physics of this distribution is relevant to solar flares, x-ray emission by comets, and pulsars. Physical parameters, including the mass ratio, are near those of a solar flare in the simulation. The simulation and analytic results show agreement in the linear regime. In the nonlinear stage the simulation shows highly accelerated electrons in agreement with the observed spectrum of x-rays emitted by solar flares. A mildly relativistic streaming electron positron plasma with no ambient magnetic field is known to be unstable to electrostatic (two-stream/beam instability) and purely electromagnetic (Weibel) modes. This instability is relevant to highly energetic interstellar phenomena, including pulsars, supernova remnants, and the early universe. It is also important for experiments in which relativistic beams penetrate a background plasma, as in fast ignitor scenarios. Cold analytic theory is presented and compared to simulations. There is good agreement in the regime where cold theory applies. The simulation and theory shows that to properly characterize the instability, directions parallel and perpendicular to propagation of the beams must be considered. A residual magnetic field is observed which may be of astro-physical significance. The stability of a plasma in the magnetic field of a current rod is investigated for various temperature and density profiles. Such a plasma obeys similar physics to a plasma in a dipole magnetic field, while the current rod is much easier to analyze theoretically and realize in simulations. The stability properties of a plasma confined in a dipole field are important for understanding a variety of space phenomena and the Levitated Dipole eXperiment (LDX). Simple energy principle calculations and simulations with a variety of temperature and density profiles show that the plasma is stable to interchange for pressure profiles ∝ r-10/3. The simulations also show that the density profile will be stationary as long as density ∝ r -2 even though the temperature profile may not be stable.

  3. Model Predictive Control of the Current Profile and the Internal Energy of DIII-D Plasmas

    NASA Astrophysics Data System (ADS)

    Lauret, M.; Wehner, W.; Schuster, E.

    2015-11-01

    For efficient and stable operation of tokamak plasmas it is important that the current density profile and the internal energy are jointly controlled by using the available heating and current-drive (H&CD) sources. The proposed approach is a version of nonlinear model predictive control in which the input set is restricted in size by the possible combinations of the H&CD on/off states. The controller uses real-time predictions over a receding-time horizon of both the current density profile (nonlinear partial differential equation) and the internal energy (nonlinear ordinary differential equation) evolutions. At every time instant the effect of every possible combination of H&CD sources on the current profile and internal energy is evaluated over the chosen time horizon. The combination that leads to the best result, which is assessed by a user-defined cost function, is then applied up until the next time instant. Simulations results based on a control-oriented transport code illustrate the effectiveness of the proposed control method. Supported by the US DOE under DE-FC02-04ER54698 & DE-SC0010661.

  4. TRANSP-based Trajectory Optimization of the Current Profile Evolution to Facilitate Robust Non-inductive Ramp-up in NSTX-U

    NASA Astrophysics Data System (ADS)

    Wehner, William; Schuster, Eugenio; Poli, Francesca

    2016-10-01

    Initial progress towards the design of non-inductive current ramp-up scenarios in the National Spherical Torus Experiment Upgrade (NSTX-U) has been made through the use of TRANSP predictive simulations. The strategy involves, first, ramping the plasma current with high harmonic fast waves (HHFW) to about 400 kA, and then further ramping to 900 kA with neutral beam injection (NBI). However, the early ramping of neutral beams and application of HHFW leads to an undesirably peaked current profile making the plasma unstable to ballooning modes. We present an optimization-based control approach to improve on the non-inductive ramp-up strategy. We combine the TRANSP code with an optimization algorithm based on sequential quadratic programming to search for time evolutions of the NBI powers, the HHFW powers, and the line averaged density that define an open-loop actuator strategy that maximizes the non-inductive current while satisfying constraints associated with the current profile evolution for MHD stable plasmas. This technique has the potential of playing a critical role in achieving robustly stable non-inductive ramp-up, which will ultimately be necessary to demonstrate applicability of the spherical torus concept to larger devices without sufficient room for a central coil. Supported by the US DOE under the SCGSR Program.

  5. Coupled low-energy - ring current plasma diffusion in the Jovian magnetosphere

    NASA Technical Reports Server (NTRS)

    Summers, D.; Siscoe, G. L.

    1985-01-01

    The outwardly diffusing Iogenic plasma and the simultaneously inwardly diffusing ring current plasma in the Jovian magnetosphere are described using a coupled diffusion model which incorporates the effects of the pressure gradient of the ring current into the cross-L diffusion coefficient. The coupled diffusion coefficient is derived by calculating the total energy available to drive the diffusion process. The condition is imposed that the diffusion coefficient takes on a local minimum value at some point in the region L = 7-8, at which point the gradient of the Io plasma density is specified as ramp value given by Siscoe et al. (1981). The hypothesis that the pressure gradient of the ring current causes the diminution of radial plasma transport is tested, and solution profiles for the Iogenic and ring current plasma densities are obtained which imply that the Io plasma ramp is caused by a high-density, low-energy component of the ring current hitherto unobserved directly.

  6. A Numerical Characterization of the Gravito-Electrostatic Sheath Equilibrium Structure in Solar Plasma

    NASA Astrophysics Data System (ADS)

    Karmakar, Pralay Kumar

    This article describes the equilibrium structure of the solar interior plasma (SIP) and solar wind plasma (SWP) in detail under the framework of the gravito-electrostatic sheath (GES) model. This model gives a precise definition of the solar surface boundary (SSB), surface origin mechanism of the subsonic SWP, and its supersonic acceleration. Equilibrium parameters like plasma potential, self-gravity, population density, flow, their gradients, and all the relevant inhomogeneity scale lengths are numerically calculated and analyzed as an initial value problem. Physical significance of the structure condition for the SSB is discussed. The plasma oscillation and Jeans time scales are also plotted and compared. In addition, different coupling parameters, and electric current profiles are also numerically studied. The current profiles exhibit an important behavior of directional reversibility, i.e., an electrodynamical transition from negative to positive value. It occurs beyond a few Jeans lengths away from the SSB. The virtual spherical surface lying at the current reversal point, where the net current becomes zero, has the property of a floating surface behavior of the real physical wall. Our investigation indicates that the SWP behaves as an ion current-carrying plasma system. The basic mechanism behind the GES formation and its distinctions from conventional plasma sheath are discussed. The electromagnetic properties of the Sun derived from our model with the most accurate available inputs are compared with those of others. These results are useful as an input element to study the properties of the linear and nonlinear dynamics of various solar plasma waves, oscillations and instabilities.

  7. Calculation of the non-inductive current profile in high-performance NSTX plasmas

    NASA Astrophysics Data System (ADS)

    Gerhardt, S. P.; Fredrickson, E.; Gates, D.; Kaye, S.; Menard, J.; Bell, M. G.; Bell, R. E.; Le Blanc, B. P.; Kugel, H.; Sabbagh, S. A.; Yuh, H.

    2011-03-01

    The constituents of the current profile have been computed for a wide range of high-performance plasmas in NSTX (Ono et al 2000 Nucl. Fusion 40 557); these include cases designed to maximize the non-inductive fraction, pulse length, toroidal-β or stored energy. In the absence of low-frequency MHD activity, good agreement is found between the reconstructed current profile and that predicted by summing the independently calculated inductive, pressure-driven and neutral beam currents, without the need to invoke any anomalous beam ion diffusion. Exceptions occur, for instance, when there are toroidal Alfvén eigenmode avalanches or coupled m/n = 1/1 + 2/1 kink-tearing modes. In these cases, the addition of a spatially and temporally dependent fast-ion diffusivity can reduce the core beam current drive, restoring agreement between the reconstructed profile and the summed constituents, as well as bringing better agreement between the simulated and measured neutron emission rate. An upper bound on the fast-ion diffusivity of ~0.5-1 m2 s-1 is found in 'MHD-free' discharges, based on the neutron emission, the time rate of change in the neutron signal when a neutral beam is stepped and reconstructed on-axis current density.

  8. Physics-based Control-oriented Modeling of the Current Profile Evolution in NSTX-Upgrade

    NASA Astrophysics Data System (ADS)

    Ilhan, Zeki; Barton, Justin; Shi, Wenyu; Schuster, Eugenio; Gates, David; Gerhardt, Stefan; Kolemen, Egemen; Menard, Jonathan

    2013-10-01

    The operational goals for the NSTX-Upgrade device include non-inductive sustainment of high- β plasmas, realization of the high performance equilibrium scenarios with neutral beam heating, and achievement of longer pulse durations. Active feedback control of the current profile is proposed to enable these goals. Motivated by the coupled, nonlinear, multivariable, distributed-parameter plasma dynamics, the first step towards feedback control design is the development of a physics-based, control-oriented model for the current profile evolution in response to non-inductive current drives and heating systems. For this purpose, the nonlinear magnetic-diffusion equation is coupled with empirical models for the electron density, electron temperature, and non-inductive current drives (neutral beams). The resulting first-principles-driven, control-oriented model is tailored for NSTX-U based on the PTRANSP predictions. Main objectives and possible challenges associated with the use of the developed model for control design are discussed. This work was supported by PPPL.

  9. Design and simulation of control algorithms for stored energy and plasma current in non-inductive scenarios on NSTX-U

    NASA Astrophysics Data System (ADS)

    Boyer, Mark; Andre, Robert; Gates, David; Gerhardt, Stefan; Menard, Jonathan; Poli, Francesca

    2015-11-01

    One of the major goals of NSTX-U is to demonstrate non-inductive operation. To facilitate this and other program goals, the center stack has been upgraded and a second neutral beam line has been added with three sources aimed more tangentially to provide higher current drive efficiency and the ability to shape the current drive profile. While non-inductive start-up and ramp-up scenarios are being developed, initial non-inductive studies will likely rely on clamping the Ohmic coil current after the plasma current has been established inductively. In this work the ability to maintain control of stored energy and plasma current once the Ohmic coil has been clamped is explored. The six neutral beam sources and the mid-plane outer gap of the plasma are considered as actuators. System identification is done using TRANSP simulations in which the actuators are modulated around a reference shot. The resulting reduced model is used to design an optimal control law with anti-windup and a recently developed framework for closed loop simulations in TRANSP is used to test the control. Limitations due to actuator saturation are assessed and robustness to beam modulation, changes in the plasma density and confinement, and changes in density and temperature profile shapes are studied. Supported by US DOE contract DE-AC02-09CH11466.

  10. Radio-frequency-assisted current startup in the fusion engineering device

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Borowski, S. K.; Peng, Yueng Kay Martin; Kammash, T.

    1984-01-01

    Auxiliary radio-frequency (RF) heating of electrons before and during the current rise phase of a large tokamak, such as the Fusion Engineering Device (FED) (R{sub 0} = 4.8 m, a = 1.3 m, sigma = 1.6, B(R{sub 0}) = 3.62 T), is examined as a means of reducing both the initiation loop voltage and resistive flux expenditure during startup. Prior to current initiation, 1 to 2 MW of electron cyclotron resonance heating power at about90 GHz is used to create a small volume of high conductivity plasma (T {sub e} approx. = 100 eV, n {sub e} approx. = 10{supmore » 19} m{sup -3}) near the upper hybrid resonance (UHR) region. This plasma conditioning, referred to as preheating, permits a small radius (a{sub 0} approx. = 0.2 to 0.4 m) current channel to be established with a relatively low initial loop voltage (less than or equal to 25 V as opposed to about 100 V without rf assist). During the subsequent plasma expansion and current rise phase, a combination of rf heating (up to 5 MW) and linear current ramping leads to a substantial savings in voltseconds by (a) minimizing the resistive flux consumption and (b) producing broad current density profiles. (With such broad profiles, the internal flux requirements are maintained at or near the flat profile limit.)« less

  11. Radio-frequency-assisted current startup in the Fusion Engineering Device

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Borowski, S.K.; Kammash, T.; Martin Peng, Y.K.

    1984-07-01

    Auxiliary radio-frequency (RF) heating of electrons before and during the current rise phase of a large tokamak, such as the Fusion Engineering Device (FED) (R/sub 0/ = 4.8 m, a = 1.3 m, sigma = 1.6, B(R/sub 0/) = 3.62 T), is examined as a means of reducing both the initiation loop voltage and resistive flux expenditure during startup. Prior to current initiation, 1 to 2 MW of electron cyclotron resonance heating power at about90 GHz is used to create a small volume of high conductivity plasma (T /sub e/ approx. = 100 eV, n /sub e/ approx. = 10/supmore » 19/ m/sup -3/) near the upper hybrid resonance (UHR) region. This plasma conditioning, referred to as preheating, permits a small radius (a/sub 0/ approx. = 0.2 to 0.4 m) current channel to be established with a relatively low initial loop voltage (less than or equal to 25 V as opposed to about 100 V without rf assist). During the subsequent plasma expansion and current rise phase, a combination of rf heating (up to 5 MW) and linear current ramping leads to a substantial savings in voltseconds by (a) minimizing the resistive flux consumption and (b) producing broad current density profiles. (With such broad profiles, the internal flux requirements are maintained at or near the flat profile limit.)« less

  12. 2D model of plasma current sheath propagation in a Mather type plasma focus device

    NASA Astrophysics Data System (ADS)

    Mohamad, Saiful Najmee; Rashid, Natashah Abdul; Halim, Mohd Mahadi; Ali, Jalil

    2018-06-01

    Plasma focus device is initially developed by two known researchers back in the 1960s, Mather and Filippov. The interest on the research built due to its capability to produce high energetic neutron from a fusion reaction. The relevance of the research in Plasma Focus device remain after decade is because of its competence to produce multi radiation yield and its known physics during nanosecond of plasma compression remain open for discussed. In the recent years, the direction of the plasma research is in device optimisation, where many possible configurations have been present, discuss and highlighting its performance for differences conditions. The significant difference between the electrode configuration is the profile of the dynamics inductance. In this context, this paper comparatively discusses the 1D dynamics model of the plasma current sheath (PSC) propagation axially and radially with the 2D model. The 2D model algorithm for the PSC propagation is developed using macro (Excel) by incorporating a drag force to solve the momentum exchange of the PCS with neutral gas. The discharge current profile of both model successfully calibrated to agree with each other with 2% difference at 1.83 µs after discharge but with an expense of different assumption.

  13. First-Principles-Driven Model-Based Optimal Control of the Current Profile in NSTX-U

    NASA Astrophysics Data System (ADS)

    Ilhan, Zeki; Barton, Justin; Wehner, William; Schuster, Eugenio; Gates, David; Gerhardt, Stefan; Kolemen, Egemen; Menard, Jonathan

    2014-10-01

    Regulation in time of the toroidal current profile is one of the main challenges toward the realization of the next-step operational goals for NSTX-U. A nonlinear, control-oriented, physics-based model describing the temporal evolution of the current profile is obtained by combining the magnetic diffusion equation with empirical correlations obtained at NSTX-U for the electron density, electron temperature, and non-inductive current drives. In this work, the proposed model is embedded into the control design process to synthesize a time-variant, linear-quadratic-integral, optimal controller capable of regulating the safety factor profile around a desired target profile while rejecting disturbances. Neutral beam injectors and the total plasma current are used as actuators to shape the current profile. The effectiveness of the proposed controller in regulating the safety factor profile in NSTX-U is demonstrated via closed-loop predictive simulations carried out in PTRANSP. Supported by PPPL.

  14. Measurements of Electron Temperature and Density Profiles of Plasmas Produced by Nike KrF Laser for Laser Plasma Instability (LPI) Research

    NASA Astrophysics Data System (ADS)

    Oh, Jaechul; Weaver, J. L.; Obenschain, S. P.; Schmitt, A. J.; Kehne, D. M.; Karasik, M.; Chan, L.-Y.; Serlin, V.; Phillips, L.

    2012-10-01

    ExperimentsfootnotetextJ. Oh, et al, GO5.4, APS DPP (2010).^,footnotetextJ. L. Weaver, et al, GO5.3, APS DPP (2010). using Nike KrF laser observed LPI signatures from CH plasmas at the laser intensities above ˜1x10^15 W/cm^2. Knowing spatial profiles of temperature (Te) and density (ne) in the underdense coronal region (0 < n < nc/4) of the plasma is essential to understanding the LPI observation. However, numerical simulation was the only way to access the profiles for the previous experiments. In the current Nike LPI experiment, a side-on grid imaging refractometer (GIR)footnotetextR. S. Craxton, et al, Phys. Fluids B 5, 4419 (1993). is being deployed for measuring the underdense plasma profiles. The GIR will resolve Te and ne in space taking a 2D snapshot of probe laser (λ= 263 nm, δt = 10 psec) beamlets (50μm spacing) refracted by the plasma at a selected time during the laser illumination. Time-resolved spectrometers with an absolute-intensity-calibrated photodiode array and a streak camera will simultaneously monitor light emission from the plasma in spectral ranges relevant to Raman (SRS) and two plasmon decay (TDP) instabilities. The experimental study of effects of the plasma profiles on the LPI initiation will be presented.

  15. Current/Pressure Profile Effects on Tearing Mode Stability in DIII-D Hybrid Discharges

    NASA Astrophysics Data System (ADS)

    Kim, K.; Park, J. M.; Murakami, M.; La Haye, R. J.; Na, Yong-Su

    2015-11-01

    It is important to understand the onset threshold and the evolution of tearing modes (TMs) for developing a high-performance steady state fusion reactor. As initial and basic comparisons to determine TM onset, the measured plasma profiles (such as temperature, density, rotation) were compared with the calculated current profiles between a pair of discharges with/without n=1 mode based on the database for DIII-D hybrid plasmas. The profiles were not much different, but the details were analyzed to determine their characteristics, especially near the rational surface. The tearing stability index calculated from PEST3, Δ' tends to increase rapidly just before the n=1 mode onset for these cases. The modeled equilibrium with varying pressure or current profiles parametrically based on the reference discharge is reconstructed for checking the onset dependency on Δ' or neoclassical effects such as bootstrap current. Simulations of TMs with the modeled equilibrium using resistive MHD codes will also be presented and compared with experiments to determine the sensibility for predicting TM onset. Work supported by US DOE under DE-FC02-04ER54698 and DE-AC52-07NA27344.

  16. Feedback control of the lower hybrid power deposition profile on Tore Supra

    NASA Astrophysics Data System (ADS)

    Barana, O.; Mazon, D.; Laborde, L.; Turco, F.

    2007-07-01

    The Tore Supra facility is well suited to study ITER relevant topics such as the real-time control of plasma current and the sustaining of steady-state discharges. This work describes a tool that was recently developed and implemented on Tore Supra to control in real time, by means of the direct knowledge of the suprathermal electron local emission profile, the width of the lower hybrid power deposition profile. This quantity can be considered to some extent equivalent to the width of the plasma current density profile in case of fully non-inductive discharges. This system takes advantage of an accurate hard x-ray diagnostics, of an efficient lower hybrid additional heating and of a reliable real-time communication network. The successful experiments carried out to test the system employed, as actuators, the parallel refractive index n// and the total power PLH. The control of the suprathermal electron local emission profile through n// was also integrated with the feedback control of the total plasma current IP with PLH and of the loop voltage Vloop with the central solenoid flux. These results demonstrate that the system is robust, reliable and able to counterbalance destabilizing events. This tool can be effectively used in the future in fully non-inductive discharges to improve the MHD stability and to maintain internal transport barriers or lower hybrid enhanced performance modes. The real-time control of the lower hybrid power deposition profile could also be used in conjunction with the electron-cyclotron radiofrequency heating for synergy studies.

  17. Current drive by spheromak injection into a tokamak

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Brown, M.R.; Bellan, P.M.

    1990-04-30

    We report the first observation of current drive by injection of a spheromak plasma into a tokamak (Caltech ENCORE small reasearch tokamak) due to the process of helicity injection. After an abrupt 30% increase, the tokamak current decays by a factor of 3 due to plasma cooling caused by the merging of the relatively cold spheromak with the tokamak. The tokamak density profile peaks sharply due to the injected spheromak plasma ({ital {bar n}}{sub 3} increases by a factor of 6) then becomes hollow, suggestive of an interchange instability.

  18. Optimization of Kink Stability in High-Beta Quasi-axisymmetric Stellarators

    NASA Astrophysics Data System (ADS)

    Fu, G. Y.; Ku, L.-P.; Manickam, J.; Cooper, W. A.

    1998-11-01

    A key issue for design of Quasi-axisymmetric stellarators( A. Reiman et al, this conference.) (QAS) is the stability of external kink modes driven by pressure-induced bootstrap current. In this work, the 3D MHD stability code TERPSICHORE(W.A. Cooper, Phys. Plasmas 3), 275(1996). is used to calculate the stability of low-n external kink modes in a high-beta QAS. The kink stability is optimized by adjusting plasma boundary shape (i.e., external coil configuration) as well as plasma pressure and current profiles. For this purpose, the TERPSICHORE code has been implemented successfully in an optimizer which maximizes kink stability as well as quasi-symmetry. A key factor for kink stability is rotational transform profile. It is found that the edge magnetic shear is strongly stabilizing. The amount of the shear needed for complete stabilization increases with edge transform. It is also found that the plasma boundary shape plays an important role in the kink stability besides transform profile. The physics mechanisms for the kink stability are being studied by examining the contributions of individual terms in δ W of the energy principle: the field line bending term, the current-driven term, the pressure-driven term, and the vacuum term. Detailed results will be reported.

  19. Hollow Cathode and Keeper-region Plasma Measurements Using Ultra-fast Miniature Scanning Probes

    NASA Technical Reports Server (NTRS)

    Goebel, Dan M.; Jameson, Kristina K.; Watkins, Ron M.; Katz, Ira

    2004-01-01

    In order to support the development of comprehensive performance and life models for future deep space missions that will utilize ion thrusters, we have undertaken a study of the plasma structure in hollow cathodes using an new pneumatic scanning probe diagnostic. This device is designed to insert a miniature probe directly into the hollow cathode orifice from either the upstream insert region in the interior of the hollow cathode, or from the downstream keeper-plasma region at the exit of the hollow cathode, to provide complete axial profiles of the discharge plasma parameters. Previous attempts to diagnose this region with probes was Limited by the melting of small probes in the intense discharge near the orifice, or caused significant perturbation of the plasma by probes large enough to survive. Our new probe is extremely compact, and when configured as a single Langmuir probe, the ceramic tube insulator is only 0.5mm in diameter and the current collecting conductor has a total area of 0.002 cm2. A series of current-voltage characteristics are obtained by applying a rapid sawtooth voltage waveform to the probe as it is scanned by the pneumatic actuator into and out of the plasma region, The bellow-sealed pneumatic drive scans the probe 4 cm in the cathode insert region and 10 cm in the anode/keeper plasmas region at average speeds of about 1 mm/msec, and the residence time at the end of the insertion stroke in the densest part of the plasma near the orifice is measured to be only 10 msec. Since the voltage sweep time is fast compared to the motion of the probe, axial profiles of the plasma density, temperature and potential with reasonable spatial resolution are obtained. Measurements of the internal cathode pressures and the axial plasma-parameter profiles for a hollow cathode operating at discharge currents of up to 35 A in xenon will be presented.

  20. DOE Office of Scientific and Technical Information (OSTI.GOV)

    Seo, Dongcheol; Peterson, B. J.; Lee, Seung Hun

    The resistive bolometers have been successfully installed in the midplane of L-port in Korea Superconducting Tokamak Advanced Research (KSTAR) device. The spatial and temporal resolutions, 4.5 cm and {approx}1 kHz, respectively, enable us to measure the radial profile of the total radiated power from magnetically confined plasma at a high temperature through radiation and neutral particles. The radiated power was measured at all shots. Even at low plasma current, the bolometer signal was detectable. The electron cyclotron resonance heating (ECH) has been used in tokamak for ECH assisted start-up and plasma control by local heating and current drive. The detectorsmore » of resistive bolometer, near the antenna of ECH, are affected by electron cyclotron wave. The tomographic reconstruction, using the Phillips-Tikhonov regularization method, will be carried out for a major radial profile of the radiation emissivity of the circular cross-section plasma.« less

  1. Measurements of the momentum and current transport from tearing instability in the Madison Symmetric Torus reversed-field pinch

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kuritsyn, A.; Fiksel, G.; Almagri, A. F.

    2009-05-15

    In this paper measurements of momentum and current transport caused by current driven tearing instability are reported. The measurements are done in the Madison Symmetric Torus reversed-field pinch [R. N. Dexter, D. W. Kerst, T. W. Lovell, S. C. Prager, and J. C. Sprott, Fusion Technol. 19, 131 (1991)] in a regime with repetitive bursts of tearing instability causing magnetic field reconnection. It is established that the plasma parallel momentum profile flattens during these reconnection events: The flow decreases in the core and increases at the edge. The momentum relaxation phenomenon is similar in nature to the well established relaxationmore » of the parallel electrical current and could be a general feature of self-organized systems. The measured fluctuation-induced Maxwell and Reynolds stresses, which govern the dynamics of plasma flow, are large and almost balance each other such that their difference is approximately equal to the rate of change of plasma momentum. The Hall dynamo, which is directly related to the Maxwell stress, drives the parallel current profile relaxation at resonant surfaces at the reconnection events. These results qualitatively agree with analytical calculations and numerical simulations. It is plausible that current-driven instabilities can be responsible for momentum transport in other laboratory and astrophysical plasmas.« less

  2. Three-dimensional modeling of a negative ion source with a magnetic filter: impact of biasing the plasma electrode on the plasma asymmetry

    NASA Astrophysics Data System (ADS)

    Fubiani, G.; Boeuf, J. P.

    2015-10-01

    The effect on the plasma characteristics of biasing positively the plasma electrode (PE) in negative ion sources with a magnetic filter is analysed using a 3D particle-in-cell model with Monte-Carlo collisions (PIC-MCC). We specialize to the one driver (i.e. one inductively coupled radio-frequency discharge) BATMAN negative ion source and the 4-drivers (large volume) ELISE device. Both are ITER prototype high power tandem-type negative ion sources developed for the neutral beam injector (NBI) system. The plasma is generated in the driver and diffuses inside the second chamber which is magnetized. Asymmetric plasma profiles originate from the formation of an electric field transverse to the electron current flowing through the magnetic filter (Hall effect). The model shows that the importance of the asymmetry increases with the PE bias potential, i.e. with the electron flow from the driver to the extraction region and depends on the shape of the magnetic filter field. We find that although the plasma density and potential profiles may be more or less asymmetric depending on the filter field configuration, the electron current to the plasma grid is always strongly asymmetric.

  3. Comprehensive and quantitative proteomic analyses of zebrafish plasma reveals conserved protein profiles between genders and between zebrafish and human.

    PubMed

    Li, Caixia; Tan, Xing Fei; Lim, Teck Kwang; Lin, Qingsong; Gong, Zhiyuan

    2016-04-13

    Omic approaches have been increasingly used in the zebrafish model for holistic understanding of molecular events and mechanisms of tissue functions. However, plasma is rarely used for omic profiling because of the technical challenges in collecting sufficient blood. In this study, we employed two mass spectrometric (MS) approaches for a comprehensive characterization of zebrafish plasma proteome, i.e. conventional shotgun liquid chromatography-tandem mass spectrometry (LC-MS/MS) for an overview study and quantitative SWATH (Sequential Window Acquisition of all THeoretical fragment-ion spectra) for comparison between genders. 959 proteins were identified in the shotgun profiling with estimated concentrations spanning almost five orders of magnitudes. Other than the presence of a few highly abundant female egg yolk precursor proteins (vitellogenins), the proteomic profiles of male and female plasmas were very similar in both number and abundance and there were basically no other highly gender-biased proteins. The types of plasma proteins based on IPA (Ingenuity Pathway Analysis) classification and tissue sources of production were also very similar. Furthermore, the zebrafish plasma proteome shares significant similarities with human plasma proteome, in particular in top abundant proteins including apolipoproteins and complements. Thus, the current study provided a valuable dataset for future evaluation of plasma proteins in zebrafish.

  4. Comprehensive and quantitative proteomic analyses of zebrafish plasma reveals conserved protein profiles between genders and between zebrafish and human

    PubMed Central

    Li, Caixia; Tan, Xing Fei; Lim, Teck Kwang; Lin, Qingsong; Gong, Zhiyuan

    2016-01-01

    Omic approaches have been increasingly used in the zebrafish model for holistic understanding of molecular events and mechanisms of tissue functions. However, plasma is rarely used for omic profiling because of the technical challenges in collecting sufficient blood. In this study, we employed two mass spectrometric (MS) approaches for a comprehensive characterization of zebrafish plasma proteome, i.e. conventional shotgun liquid chromatography-tandem mass spectrometry (LC-MS/MS) for an overview study and quantitative SWATH (Sequential Window Acquisition of all THeoretical fragment-ion spectra) for comparison between genders. 959 proteins were identified in the shotgun profiling with estimated concentrations spanning almost five orders of magnitudes. Other than the presence of a few highly abundant female egg yolk precursor proteins (vitellogenins), the proteomic profiles of male and female plasmas were very similar in both number and abundance and there were basically no other highly gender-biased proteins. The types of plasma proteins based on IPA (Ingenuity Pathway Analysis) classification and tissue sources of production were also very similar. Furthermore, the zebrafish plasma proteome shares significant similarities with human plasma proteome, in particular in top abundant proteins including apolipoproteins and complements. Thus, the current study provided a valuable dataset for future evaluation of plasma proteins in zebrafish. PMID:27071722

  5. Validation of theoretical models of intrinsic torque in DIII-D

    NASA Astrophysics Data System (ADS)

    Grierson, B. A.; Wang, W. X.; Battaglia, D. J.; Chrystal, C.; Solomon, W. M.; Degrassie, J. S.; Staebler, G. M.; Boedo, J. A.

    2016-10-01

    Plasma rotation experiments in DIII-D are validating models of main-ion intrinsic rotation by testing Reynolds stress induced toroidal flow in the plasma core and intrinsic rotation induced by ion orbit losses in the plasma edge. In the core of dominantly electron heated plasmas with Te=Ti, the main-ion intrinsic toroidal rotation undergoes a reversal that correlates with the critical gradient for ITG turbulence. Residual stress arising from zonal-flow ExB shear and turbulence intensity gradient produce residual stress and counter-current intrinsic torque, which is balanced by momentum diffusion, creating the hollow profile. Quantitative agreement is obtained for the first time between the measured main-ion toroidal rotation and the rotation profile predicted by nonlinear GTS gyrokinetic simulations. At the plasma boundary, new main-ion CER measurements show a co-current rotation layer and this is tested against ion orbit loss models as the source of bulk plasma rotation. Work supported by the US Department of Energy under DE-AC02-09CH11466 and DE-FC02-04ER54698.

  6. Non-inductive current generation in fusion plasmas with turbulence

    NASA Astrophysics Data System (ADS)

    Wang, Weixing; Ethier, S.; Startsev, E.; Chen, J.; Hahm, T. S.; Yoo, M. G.

    2017-10-01

    It is found that plasma turbulence may strongly influence non-inductive current generation. This may have radical impact on various aspects of tokamak physics. Our simulation study employs a global gyrokinetic model coupling self-consistent neoclassical and turbulent dynamics with focus on electron current. Distinct phases in electron current generation are illustrated in the initial value simulation. In the early phase before turbulence develops, the electron bootstrap current is established in a time scale of a few electron collision times, which closely agrees with the neoclassical prediction. The second phase follows when turbulence begins to saturate, during which turbulent fluctuations are found to strongly affect electron current. The profile structure, amplitude and phase space structure of electron current density are all significantly modified relative to the neoclassical bootstrap current by the presence of turbulence. Both electron parallel acceleration and parallel residual stress drive are shown to play important roles in turbulence-induced current generation. The current density profile is modified in a way that correlates with the fluctuation intensity gradient through its effect on k//-symmetry breaking in fluctuation spectrum. Turbulence is shown to deduct (enhance) plasma self-generated current in low (high) collisionality regime, and the reduction of total electron current relative to the neoclassical bootstrap current increases as collisionality decreases. The implication of this result to the fully non-inductive current operation in steady state burning plasma regime should be investigated. Finally, significant non-inductive current is observed in flat pressure region, which is a nonlocal effect and results from turbulence spreading induced current diffusion. Work supported by U.S. DOE Contract DE-AC02-09-CH11466.

  7. Rotation and transport in Alcator C-Mod ITB plasmas

    NASA Astrophysics Data System (ADS)

    Fiore, C. L.; Rice, J. E.; Podpaly, Y.; Bespamyatnov, I. O.; Rowan, W. L.; Hughes, J. W.; Reinke, M.

    2010-06-01

    Internal transport barriers (ITBs) are seen under a number of conditions in Alcator C-Mod plasmas. Most typically, radio frequency power in the ion cyclotron range of frequencies (ICRFs) is injected with the second harmonic of the resonant frequency for minority hydrogen ions positioned off-axis at r/a > 0.5 to initiate the ITBs. They can also arise spontaneously in ohmic H-mode plasmas. These ITBs typically persist tens of energy confinement times until the plasma terminates in radiative collapse or a disruption occurs. All C-Mod core barriers exhibit strongly peaked density and pressure profiles, static or peaking temperature profiles, peaking impurity density profiles and thermal transport coefficients that approach neoclassical values in the core. The strongly co-current intrinsic central plasma rotation that is observed following the H-mode transition has a profile that is peaked in the centre of the plasma and decreases towards the edge if the ICRF power deposition is in the plasma centre. When the ICRF resonance is placed off-axis, the rotation develops a well in the core region. The central rotation continues to decrease as long as the central density peaks when an ITB develops. This rotation profile is flat in the centre (0 < r/a < 0.4) but rises steeply in the region where the foot in the ITB density profile is observed (0.5 < r/a < 0.7). A correspondingly strong E × B shear is seen at the location of the ITB foot that is sufficiently large to stabilize ion temperature gradient instabilities that dominate transport in C-Mod high density plasmas.

  8. Concurrent profiling of polar metabolites and lipids in human plasma using HILIC-FTMS

    NASA Astrophysics Data System (ADS)

    Cai, Xiaoming; Li, Ruibin

    2016-11-01

    Blood plasma is the most popularly used sample matrix for metabolite profiling studies, which aim to achieve global metabolite profiling and biomarker discovery. However, most of the current studies on plasma metabolite profiling focused on either the polar metabolites or lipids. In this study, a comprehensive analysis approach based on HILIC-FTMS was developed to concurrently examine polar metabolites and lipids. The HILIC-FTMS method was developed using mixed standards of polar metabolites and lipids, the separation efficiency of which is better in HILIC mode than in C5 and C18 reversed phase (RP) chromatography. This method exhibits good reproducibility in retention times (CVs < 3.43%) and high mass accuracy (<3.5 ppm). In addition, we found MeOH/ACN/Acetone (1:1:1, v/v/v) as extraction cocktail could achieve desirable gathering of demanded extracts from plasma samples. We further integrated the MeOH/ACN/Acetone extraction with the HILIC-FTMS method for metabolite profiling and smoking-related biomarker discovery in human plasma samples. Heavy smokers could be successfully distinguished from non smokers by univariate and multivariate statistical analysis of the profiling data, and 62 biomarkers for cigarette smoke were found. These results indicate that our concurrent analysis approach could be potentially used for clinical biomarker discovery, metabolite-based diagnosis, etc.

  9. Refraction-enhanced backlit imaging of axially symmetric inertial confinement fusion plasmas.

    PubMed

    Koch, Jeffrey A; Landen, Otto L; Suter, Laurence J; Masse, Laurent P; Clark, Daniel S; Ross, James S; Mackinnon, Andrew J; Meezan, Nathan B; Thomas, Cliff A; Ping, Yuan

    2013-05-20

    X-ray backlit radiographs of dense plasma shells can be significantly altered by refraction of x rays that would otherwise travel straight-ray paths, and this effect can be a powerful tool for diagnosing the spatial structure of the plasma being radiographed. We explore the conditions under which refraction effects may be observed, and we use analytical and numerical approaches to quantify these effects for one-dimensional radial opacity and density profiles characteristic of inertial-confinement fusion (ICF) implosions. We also show how analytical and numerical approaches allow approximate radial plasma opacity and density profiles to be inferred from point-projection refraction-enhanced radiography data. This imaging technique can provide unique data on electron density profiles in ICF plasmas that cannot be obtained using other techniques, and the uniform illumination provided by point-like x-ray backlighters eliminates a significant source of uncertainty in inferences of plasma opacity profiles from area-backlit pinhole imaging data when the backlight spatial profile cannot be independently characterized. The technique is particularly suited to in-flight radiography of imploding low-opacity shells surrounding hydrogen ice, because refraction is sensitive to the electron density of the hydrogen plasma even when it is invisible to absorption radiography. It may also provide an alternative approach to timing shockwaves created by the implosion drive, that are currently invisible to absorption radiography.

  10. Studies on plasma profiles and its effect on dust charging in hydrogen plasma

    NASA Astrophysics Data System (ADS)

    Kakati, B.; Kausik, S. S.; Saikia, B. K.; Bandyopadhay, M.

    2010-02-01

    Plasma profiles and its influence on dust charging are studied in hydrogen plasma. The plasma is produced in a high vacuum device by a hot cathode discharge method and is confined by a cusped magnetic field cage. A cylindrical Espion advanced Langmuir probe having 0.15 mm diameter and 10.0 mm length is used to study the plasma parameters for various discharge conditions. Optimum operational discharge parameters in terms of charging of the dust grains are studied. The charge on the surface of the dust particle is calculated from the capacitance model and the current by the dust grains is measured by the combination of a Faraday cup and an electrometer. Unlike our previous experiments in which dust grains were produced in-situ, here a dust dropper is used to drop the dust particles into the plasma.

  11. Plasma metabolic profiling of dairy cows affected with clinical ketosis using LC/MS technology.

    PubMed

    Li, Y; Xu, C; Xia, C; Zhang, Hy; Sun, Lw; Gao, Y

    2014-01-01

    Ketosis in dairy cattle is an important metabolic disorder. Currently, the plasma metabolic profile of ketosis as determined using liquid chromatography-mass spectrometry (LC/MS) has not been reported. To investigate plasma metabolic profiles from cows with clinical ketosis in comparison to control cows. Twenty Holstein dairy cows were divided into two groups based on clinical signs and plasma β-hydroxybutyric acid and glucose concentrations 7-21 days postpartum: clinical ketosis and control cows. Plasma metabolic profiles were analyzed using LC/MS. Data were processed using principal component analysis and orthogonal partial least-squares discriminant analysis. Compared to control cows, the levels of valine, glycine, glycocholic, tetradecenoic acid, and palmitoleic acid increased significantly in clinical ketosis. On the other hand, the levels of arginine, aminobutyric acid, leucine/isoleucine, tryptophan, creatinine, lysine, norcotinine, and undecanoic acid decreased markedly. Our results showed that the metabolic changes in cows with clinical ketosis involve complex metabolic networks and signal transduction. These results are important for future studies elucidating the pathogenesis, diagnosis, and prevention of clinical ketosis in dairy cows.

  12. RMP ELM Suppression in DIII-D Plasmas with ITER Similar Shapes and Collisionalities

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Evans, T.E.; Fenstermacher, M. E.; Moyer, R.A.

    2008-01-01

    Large Type-I edge localized modes (ELMs) are completely eliminated with small n = 3 resonant magnetic perturbations (RMP) in low average triangularity, = 0.26, plasmas and in ITER similar shaped (ISS) plasmas, = 0.53, with ITER relevant collisionalities ve 0.2. Significant differences in the RMP requirements and in the properties of the ELM suppressed plasmas are found when comparing the two triangularities. In ISS plasmas, the current required to suppress ELMs is approximately 25% higher than in low average triangularity plasmas. It is also found that the width of the resonant q95 window required for ELM suppression is smaller inmore » ISS plasmas than in low average triangularity plasmas. An analysis of the positions and widths of resonant magnetic islands across the pedestal region, in the absence of resonant field screening or a self-consistent plasma response, indicates that differences in the shape of the q profile may explain the need for higher RMP coil currents during ELM suppression in ISS plasmas. Changes in the pedestal profiles are compared for each plasma shape as well as with changes in the injected neutral beam power and the RMP amplitude. Implications of these results are discussed in terms of requirements for optimal ELM control coil designs and for establishing the physics basis needed in order to scale this approach to future burning plasma devices such as ITER.« less

  13. Interplay between plasma hormone profiles, sex and body condition in immature hawksbill turtles (Eretmochelys imbricata) subjected to a capture stress protocol.

    PubMed

    Jessop, Tim S; Sumner, Joanna M; Limpus, Colin J; Whittier, Joan M

    2004-01-01

    We investigated plasma hormone profiles of corticosterone and testosterone in immature hawksbill turtles (Eretmochelys imbricata) in response to a capture stress protocol. Further, we examined whether sex and body condition were covariates associated with variation in the adrenocortical response of immature turtles. Hawksbill turtles responded to the capture stress protocol by significantly increasing plasma levels of corticosterone over a 5 h period. There was no significant sex difference in the corticosterone stress response of immature turtles. Plasma testosterone profiles, while significantly different between the sexes, did not exhibit a significant change during the 5 h capture stress protocol. An index of body condition was not significantly associated with a turtle's capacity to produce plasma corticosterone both prior to and during exposure to the capture stress protocol. In summary, while immature hawksbill turtles exhibited an adrenocortical response to a capture stress protocol, neither their sex nor body condition was responsible for variation in endocrine responses. This lack of interaction between the adrenocortical response and these internal factors suggests that the inactive reproductive- and the current energetic- status of these immature turtles are important factors that could influence plasma hormone profiles during stress.

  14. Plasma Flow During RF Discharges in VASIMR

    NASA Technical Reports Server (NTRS)

    Jacobson, V. T.; Chang Diaz, F. R.; Squire, J. P.; Ilin, A. V.; Bengtson, R. D.; Carter, M. D.; Goulding, R. H.

    1999-01-01

    The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) plasma source consists of a helical antenna, driven at frequencies of 4 to 19 MHz with powers up to 1 kW, in a magnetic field up to 3 kG. Helium is the current test gas, and future experiments with hydrogen are planned. Plasma density and temperature profiles were measured by a reciprocating Langmuir probe, and plasma flow profiles were measured with a reciprocating Mach probe. Both probes were located about 0.5 m downstream from the helical antenna. The plasma source operated in capacitive and inductive modes in addition to a helicon mode. During capacitive and inductive modes, densities were low and plasma flow was < 0.5 Cs. When the plasma operated in a helicon mode, the densities measured downstream from the source were higher [10(exp 12) / cubic cm ] and plasma flow along the magnetic field was of the order Mach 1. Details of the measurements will be shown.

  15. Edge Stability and Performance of the ELM-Free Quiescent H-Mode and the Quiescent Double Barrier Mode on DIII-D

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    West, W P; Burrell, K H; Casper, T A

    2004-12-03

    The quiescent H (QH) mode, an edge localized mode (ELM)-free, high-confinement mode, combines well with an internal transport barrier to form quiescent double barrier (QDB) stationary state, high performance plasmas. The QH-mode edge pedestal pressure is similar to that seen in ELMing phases of the same discharge, with similar global energy confinement. The pedestal density in early ELMing phases of strongly pumped counter injection discharges drops and a transition to QH-mode occurs, leading to lower calculated edge bootstrap current. Plasmas current ramp experiment and ELITE code modeling of edge stability suggest that QH-modes lie near an edge current stability boundary.more » At high triangularity, QH-mode discharges operate at higher pedestal density and pressure, and have achieved ITER level values of {beta}{sub PED} and {nu}*. The QDB achieves performance of {alpha}{sub N}H{sub 89} {approx} 7 in quasi-stationary conditions for a duration of 10 tE, limited by hardware. Recently we demonstrated stationary state QDB discharges with little change in kinetic and q profiles (q{sub 0} > 1) for 2 s, comparable to ELMing ''hybrid scenarios'', yet without the debilitating effects of ELMs. Plasma profile control tools, including electron cyclotron heating and current drive and neutral beam heating, have been demonstrated to control simultaneously the q profile development, the density peaking, impurity accumulation and plasma beta.« less

  16. Plasma currents and anisotropy in the tail-dipole transition region

    NASA Astrophysics Data System (ADS)

    Artemyev, A.; Zhang, X. J.; Angelopoulos, V.; Runov, A.

    2017-12-01

    Using conjugated THEMIS and Van Allen Probes observations in the nightside magnetosphere, we examine statistically plasma and magnetic field characteristics at multiple locations simultaneously across the 3-10 RE region (i.e., across the tail-dipole transition region, whose location depends on tail flux loading and the strength of global convection). We find that the spatial distributions of ion and electron anisotropies vary significantly but systematically with radial distance and geomagnetic activity. For low Kp (<2), ions are transversely anisotropic near Earth but isotropic in the tail, whereas electrons are isotropic closer to Earth but field-aligned in tail. For large Kp (>4), the anisotropy profiles for ions and electrons reverse: ions are isotropic closer to the Earth and field-aligned in the tail, whereas electrons are transversely anisotropic closer to Earth but isotropic in the tail. Using the measured plasma anisotropy radial profiles we estimate the currents from curvature drifts and compare them with diamagnetic currents. We also discuss the implications of the observed plasma anisotropies for the presence and spatial distribution of field-aligned electric fields.

  17. Enhanced reproducibility of L-mode plasma discharges via physics-model-based q-profile feedback control in DIII-D

    NASA Astrophysics Data System (ADS)

    Schuster, E.; Wehner, W. P.; Barton, J. E.; Boyer, M. D.; Luce, T. C.; Ferron, J. R.; Holcomb, C. T.; Walker, M. L.; Humphreys, D. A.; Solomon, W. M.; Penaflor, B. G.; Johnson, R. D.

    2017-11-01

    Recent experiments on DIII-D demonstrate the potential of physics-model-based q-profile control to improve reproducibility of plasma discharges. A combined feedforward  +  feedback control scheme is employed to optimize the current ramp-up phase by consistently achieving target q profiles (Target 1: q_min=1.3, q95=4.4 ; Target 2: q_min=1.65, q95=5.0 ; Target 3: q_min=2.1, q95=6.2 ) at prescribed times during the plasma formation phase (Target 1: t=1.5 s; Target 2: t=1.3 s; Target 3: t=1.0 s). At the core of the control scheme is a nonlinear, first-principles-driven, physics-based, control-oriented model of the plasma dynamics valid for low confinement (L-mode) scenarios. To prevent undesired L-H transitions, a constraint on the maximum allowable total auxiliary power is imposed in addition to the maximum powers for the individual heating and current-drive sources. Experimental results are presented to demonstrate the effectiveness of the combined feedforward  +  feedback control scheme to consistently achieve the desired target profiles at the predefined times. These results also show how the addition of feedback control significantly improves upon the feedforward-only control solution by reducing the matching error and also how the feedback controller is able to reduce the matching error as the constraint on the maximum allowable total auxiliary power is relaxed while keeping the plasma in L-mode.

  18. Modifications to the edge current profile with auxiliary edge current drive and improved confinement in a reversed-field pinch

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chapman, B.E.; Biewer, T.M.; Chattopadhyay, P.K.

    2000-09-01

    Auxiliary edge current drive is routinely applied in the Madison Symmetric Torus [R.N. Dexter, D. W. Kerst, T.W. Lovell et.al., Fusion Technol. 19, 131 (1991)] with the goal of modifying the parallel current profile to reduce current- driven magnetic fluctuations and the associated particle and energy transport. Provided by an inductive electric field, the current drive successfully reduces energy transport. First-time measurements of the modified edge current profile reveal that, relative to discharges without auxiliary current drive, the edge current density decreases. This decrease is explicable in terms of newly measured reductions in the dynamo (fluctuation-based) electric field and themore » electrical conductivity. Induced by the current drive, these two changes to the edge plasma play as much of a role in determining the resultant edge current profile as does the current drive itself.« less

  19. MHD Equilibrium with Reversed Current Density and Magnetic Islands Revisited: the Vacuum Vector Potential Calculus

    NASA Astrophysics Data System (ADS)

    L. Braga, F.

    2013-10-01

    The solution of Grad-Shafranov equation determines the stationary behavior of fusion plasma inside a tokamak. To solve the equation it is necessary to know the toroidal current density profile. Recent works show that it is possible to determine a magnetohydrodynamic (MHD) equilibrium with reversed current density (RCD) profiles that presents magnetic islands. In this work we show analytical MHD equilibrium with a RCD profile and analyze the structure of the vacuum vector potential associated with these equilibria using the virtual casing principle.

  20. Particle pinch with fully noninductive lower hybrid current drive in Tore Supra.

    PubMed

    Hoang, G T; Bourdelle, C; Pégourié, B; Schunke, B; Artaud, J F; Bucalossi, J; Clairet, F; Fenzi-Bonizec, C; Garbet, X; Gil, C; Guirlet, R; Imbeaux, F; Lasalle, J; Loarer, T; Lowry, C; Travère, J M; Tsitrone, E

    2003-04-18

    Recently, plasmas exceeding 4 min have been obtained with lower hybrid current drive (LHCD) in Tore Supra. These LHCD plasmas extend for over 80 times the resistive current diffusion time with zero loop voltage. Under such unique conditions the neoclassical particle pinch driven by the toroidal electric field vanishes. Nevertheless, the density profile remains peaked for more than 4 min. For the first time, the existence of an inward particle pinch in steady-state plasma without toroidal electric field, much larger than the value predicted by the collisional neoclassical theory, is experimentally demonstrated.

  1. Ground-based plasma contractor characterization

    NASA Technical Reports Server (NTRS)

    Patterson, Michael J.; Aadland, Randall S.

    1987-01-01

    Presented are recent NASA Lewis Research Center (LeRC) plasma contractor experimental results, as well as a description of the plasma contractor test facility. The operation of a 24 cm diameter plasma source with hollow cathode was investigated in the lighted-mode regime of electron current collection from 0.1 to 7.0 A. These results are compared to those obtained with a 12 cm plasma source. Full two-dimensional plasma potential profiles were constructed from emissive probe traces of the contractor plume. The experimentally measured dimensions of the plume sheaths were then compared to those theoretically predicted using a model of a spherical double sheath. Results are consistent for currents up to approximately 1.0 A. For currents above 1.0 A, substantial deviations from theory occur. These deviations are due to sheath asphericity, and possibly volume ionization in the double-sheath region.

  2. Uncertainty propagation in q and current profiles derived from motional Stark effect polarimetry on TFTR (abstract)a)

    NASA Astrophysics Data System (ADS)

    Batha, S. H.; Levinton, F. M.; Bell, M. G.; Wieland, R. M.; Hirschman, S. P.

    1995-01-01

    The magnetic-field pitch-angle profile, γp(R)≡arctan(Bpol/Btor), is measured on the TFTR tokamak using a motional Stark effect (MSE) polarimeter. Measured profiles are converted to q profiles with the equilibrium code vmec. Uncertainties in the q profile due to uncertainties in the γp(R), magnetics, and kinetic measurements are quantified. Subsequent uncertainties in the vmec-calculated profiles of current density and shear, both of which are important for stability and transport analyses, are also quantified. Examples of circular plasmas under various confinement modes, including the supershot and L mode, will be given.

  3. Combined magnetic and kinetic control of advanced tokamak steady state scenarios based on semi-empirical modelling

    NASA Astrophysics Data System (ADS)

    Moreau, D.; Artaud, J. F.; Ferron, J. R.; Holcomb, C. T.; Humphreys, D. A.; Liu, F.; Luce, T. C.; Park, J. M.; Prater, R.; Turco, F.; Walker, M. L.

    2015-06-01

    This paper shows that semi-empirical data-driven models based on a two-time-scale approximation for the magnetic and kinetic control of advanced tokamak (AT) scenarios can be advantageously identified from simulated rather than real data, and used for control design. The method is applied to the combined control of the safety factor profile, q(x), and normalized pressure parameter, βN, using DIII-D parameters and actuators (on-axis co-current neutral beam injection (NBI) power, off-axis co-current NBI power, electron cyclotron current drive power, and ohmic coil). The approximate plasma response model was identified from simulated open-loop data obtained using a rapidly converging plasma transport code, METIS, which includes an MHD equilibrium and current diffusion solver, and combines plasma transport nonlinearity with 0D scaling laws and 1.5D ordinary differential equations. The paper discusses the results of closed-loop METIS simulations, using the near-optimal ARTAEMIS control algorithm (Moreau D et al 2013 Nucl. Fusion 53 063020) for steady state AT operation. With feedforward plus feedback control, the steady state target q-profile and βN are satisfactorily tracked with a time scale of about 10 s, despite large disturbances applied to the feedforward powers and plasma parameters. The robustness of the control algorithm with respect to disturbances of the H&CD actuators and of plasma parameters such as the H-factor, plasma density and effective charge, is also shown.

  4. Three dimensional equilibrium solutions for a current-carrying reversed-field pinch plasma with a close-fitting conducting shell

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Koliner, J. J.; Boguski, J., E-mail: boguski@wisc.edu; Anderson, J. K.

    2016-03-15

    In order to characterize the Madison Symmetric Torus (MST) reversed-field pinch (RFP) plasmas that bifurcate to a helical equilibrium, the V3FIT equilibrium reconstruction code was modified to include a conducting boundary. RFP plasmas become helical at a high plasma current, which induces large eddy currents in MST's thick aluminum shell. The V3FIT conducting boundary accounts for the contribution from these eddy currents to external magnetic diagnostic coil signals. This implementation of V3FIT was benchmarked against MSTFit, a 2D Grad-Shafranov solver, for axisymmetric plasmas. The two codes both fit B{sub θ} measurement loops around the plasma minor diameter with qualitative agreementmore » between each other and the measured field. Fits in the 3D case converge well, with q-profile and plasma shape agreement between two distinct toroidal locking phases. Greater than 60% of the measured n = 5 component of B{sub θ} at r = a is due to eddy currents in the shell, as calculated by the conducting boundary model.« less

  5. Feature Profile Evolution of SiO2 Trenches In Fluorocarbon Plasmas

    NASA Technical Reports Server (NTRS)

    Hwang, Helen; Govindan, T. R.; Meyyappan, M.; Arunachalam, Valli; Rauf, Shahid; Coronell, Dan; Carroll, Carol W. (Technical Monitor)

    1999-01-01

    Etching of silicon microstructures for semiconductor manufacturing in chlorine plasmas has been well characterized. The etching proceeds in a two-part process, where the chlorine neutrals passivate the Si surface and then the ions etch away SiClx. However, etching in more complicated gas mixtures and materials, such as etching of SiO2 in Ar/C4F8, requires knowledge of the ion and neutral distribution functions as a function of angle and velocity, in addition to modeling the gas surface reactions. In order to address these needs, we have developed and integrated a suite of models to simulate the etching process from the plasma reactor level to the feature profile evolution level. This arrangement allows for a better understanding, control, and prediction of the influence of equipment level process parameters on feature profile evolution. We are currently using the HPEM (Hybrid Plasma Equipment Model) and PCMCM (Plasma Chemistry Monte Carlo Model) to generate plasma properties and ion and neutral distribution functions for argon/fluorocarbon discharges in a GEC Reference Cell. These quantities are then input to the feature scale model, Simulation of Profile Evolution by Level Sets (SPELS). A surface chemistry model is used to determine the interaction of the incoming species with the substrate material and simulate the evolution of the trench profile. The impact of change of gas pressure and inductive power on the relative flux of CFx and F to the wafer, the etch and polymerization rates, and feature profiles will be examined. Comparisons to experimental profiles will also be presented.

  6. Mode suppression of a two-dimensional potential relaxation instability in a weakly magnetized discharge plasma

    NASA Astrophysics Data System (ADS)

    Gyergyek, T.; Čerček, M.; Jelić, N.; Stanojević, M.

    1993-05-01

    A potential relaxation instability (PRI) is modulated by an external signal using an additional grid to modulate the radial plasma potential profile in a magnetized plasma column in a linear magnetized discharge plasma device. It is observed that the electrode current oscillations follow the van der Pol equation with an external forcing term, and the linear growth rate of the instability is measured.

  7. CORSICA modelling of ITER hybrid operation scenarios

    NASA Astrophysics Data System (ADS)

    Kim, S. H.; Bulmer, R. H.; Campbell, D. J.; Casper, T. A.; LoDestro, L. L.; Meyer, W. H.; Pearlstein, L. D.; Snipes, J. A.

    2016-12-01

    The hybrid operating mode observed in several tokamaks is characterized by further enhancement over the high plasma confinement (H-mode) associated with reduced magneto-hydro-dynamic (MHD) instabilities linked to a stationary flat safety factor (q ) profile in the core region. The proposed ITER hybrid operation is currently aiming at operating for a long burn duration (>1000 s) with a moderate fusion power multiplication factor, Q , of at least 5. This paper presents candidate ITER hybrid operation scenarios developed using a free-boundary transport modelling code, CORSICA, taking all relevant physics and engineering constraints into account. The ITER hybrid operation scenarios have been developed by tailoring the 15 MA baseline ITER inductive H-mode scenario. Accessible operation conditions for ITER hybrid operation and achievable range of plasma parameters have been investigated considering uncertainties on the plasma confinement and transport. ITER operation capability for avoiding the poloidal field coil current, field and force limits has been examined by applying different current ramp rates, flat-top plasma currents and densities, and pre-magnetization of the poloidal field coils. Various combinations of heating and current drive (H&CD) schemes have been applied to study several physics issues, such as the plasma current density profile tailoring, enhancement of the plasma energy confinement and fusion power generation. A parameterized edge pedestal model based on EPED1 added to the CORSICA code has been applied to hybrid operation scenarios. Finally, fully self-consistent free-boundary transport simulations have been performed to provide information on the poloidal field coil voltage demands and to study the controllability with the ITER controllers. Extended from Proc. 24th Int. Conf. on Fusion Energy (San Diego, 2012) IT/P1-13.

  8. Numerical experiments on neutron yield and soft x-ray study of a ˜100 kJ plasma focus using the current profile fitting technique

    NASA Astrophysics Data System (ADS)

    Ong, S. T.; Chaudhary, K.; Ali, J.; Lee, S.

    2014-07-01

    Numerical experiments using the Lee model were performed to study the neutron yield and soft x-ray emission from the IR-MPF-100 plasma focus using the current fitting technique. The mass sweeping factor and the current factor for the axial and radial phase were used to represent the imperfections encountered in experiments. All gross properties including the yields were realistically simulated once the computed and measured current profiles were well fitted. The computed neutron yield Yn was in agreement with the experimentally measured Yn at 20 kV (E0 ˜ 30 kJ) charging voltage. The optimum computed neutron yield of Yn = 1.238 × 109 neutrons per shot was obtained at optimum physics parameters of the plasma focus operated with deuterium gas. It was also observed that no soft x-rays were emitted from the IR-MPF-100 plasma focus operated with argon gas due to the absence of helium-like and hydrogen-like ions at a low plasma temperature (˜0.094 keV) and axial speed (8.12 cm µs-1). However, the soft x-ray yield can be achieved by increasing the charging voltage, using a higher ratio of outer anode radius to inner anode radius c or shorter anode length z0, or using neon as the operating gas.

  9. Coupling of RF antennas to large volume helicon plasma

    NASA Astrophysics Data System (ADS)

    Chang, Lei; Hu, Xinyue; Gao, Lei; Chen, Wei; Wu, Xianming; Sun, Xinfeng; Hu, Ning; Huang, Chongxiang

    2018-04-01

    Large volume helicon plasma sources are of particular interest for large scale semiconductor processing, high power plasma propulsion and recently plasma-material interaction under fusion conditions. This work is devoted to studying the coupling of four typical RF antennas to helicon plasma with infinite length and diameter of 0.5 m, and exploring its frequency dependence in the range of 13.56-70 MHz for coupling optimization. It is found that loop antenna is more efficient than half helix, Boswell and Nagoya III antennas for power absorption; radially parabolic density profile overwhelms Gaussian density profile in terms of antenna coupling for low-density plasma, but the superiority reverses for high-density plasma. Increasing the driving frequency results in power absorption more near plasma edge, but the overall power absorption increases with frequency. Perpendicular stream plots of wave magnetic field, wave electric field and perturbed current are also presented. This work can serve as an important reference for the experimental design of large volume helicon plasma source with high RF power.

  10. Langmuir probe diagnostics of an atmospheric pressure, vortex-stabilized nitrogen plasma jet

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Prevosto, L.; Mancinelli, B. R.; Kelly, H.

    Langmuir probe measurements in an atmospheric pressure direct current (dc) plasma jet are reported. Sweeping probes were used. The experiment was carried out using a dc non-transferred arc torch with a rod-type cathode and an anode of 5 mm diameter. The torch was operated at a nominal power level of 15 kW with a nitrogen flow rate of 25 Nl min{sup -1}. A flat ion saturation region was found in the current-voltage curve of the probe. The ion saturation current to a cylindrical probe in a high-pressure non local thermal equilibrium (LTE) plasma was modeled. Thermal effects and ionization/recombination processesmore » inside the probe perturbed region were taken into account. Averaged radial profiles of the electron and heavy particle temperatures as well as the electron density were obtained. An electron temperature around 11 000 K, a heavy particle temperature around 9500 K and an electron density of about 4 Multiplication-Sign 10{sup 22} m{sup -3}, were found at the jet centre at 3.5 mm downstream from the torch exit. Large deviations from kinetic equilibrium were found throughout the plasma jet. The electron and heavy particle temperature profiles showed good agreement with those reported in the literature by using spectroscopic techniques. It was also found that the temperature radial profile based on LTE was very close to that of the electrons. The calculations have shown that this method is particularly useful for studying spraying-type plasma jets characterized by electron temperatures in the range 9000-14 000 K.« less

  11. Algebraic motion of vertically displacing plasmas

    NASA Astrophysics Data System (ADS)

    Pfefferlé, D.; Bhattacharjee, A.

    2018-02-01

    The vertical motion of a tokamak plasma is analytically modelled during its non-linear phase by a free-moving current-carrying rod inductively coupled to a set of fixed conducting wires or a cylindrical conducting shell. The solutions capture the leading term in a Taylor expansion of the Green's function for the interaction between the plasma column and the surrounding vacuum vessel. The plasma shape and profiles are assumed not to vary during the vertical drifting phase such that the plasma column behaves as a rigid body. In the limit of perfectly conducting structures, the plasma is prevented to come in contact with the wall due to steep effective potential barriers created by the induced Eddy currents. Resistivity in the wall allows the equilibrium point to drift towards the vessel on the slow timescale of flux penetration. The initial exponential motion of the plasma, understood as a resistive vertical instability, is succeeded by a non-linear "sinking" behaviour shown to be algebraic and decelerating. The acceleration of the plasma column often observed in experiments is thus concluded to originate from an early sharing of toroidal current between the core, the halo plasma, and the wall or from the thermal quench dynamics precipitating loss of plasma current.

  12. Combined magnetic and kinetic control of advanced tokamak steady state scenarios based on semi-empirical modelling

    DOE PAGES

    Moreau, Didier; Artaud, J. F.; Ferron, John R.; ...

    2015-05-01

    This paper shows that semi-empirical data-driven models based on a twotime- scale approximation for the magnetic and kinetic control of advanced tokamak (AT) scenarios can be advantageously identified from simulated rather than real data, and used for control design. The method is applied to the combined control of the safety factor profile, q(x), and normalized pressure parameter, β N, using DIII-D parameters and actuators (on-axis co-current neutral beam injection (NBI) power, off axis co-current NBI power, electron cyclotron current drive power, and ohmic coil). The approximate plasma response model was identified from simulated data obtained using a rapidly converging plasmamore » transport code, METIS, which includes an MHD equilibrium and current diffusion solver, and combines plasma transport nonlinearity with 0-D scaling laws and 1.5-D ordinary differential equations. A number of open loop simulations were performed, in which the heating and current drive (H&CD) sources were randomly modulated around the typical values of a reference AT discharge on DIIID. Using these simulated data, a two-time-scale state space model was obtained for the coupled evolution of the poloidal flux profile and βN parameter, and a controller was synthesized based on the near-optimal ARTAEMIS algorithm [D. Moreau et al., Nucl. Fusion 53 (2013) 063020]. The paper discusses the results of closed-loop nonlinear simulations, using this controller for steady state AT operation. With feedforward plus feedback control, the steady state target q-profile and β N are satisfactorily tracked with a time scale of about ten seconds, despite large disturbances applied to the feedforward powers and plasma parameters. The effectiveness of the control algorithm is thus demonstrated for long pulse and steady state high-β N AT discharges. Its robustness with respect to disturbances of the H&CD actuators and of plasma parameters such as the H-factor, plasma density and effective charge, is also shown.« less

  13. Enhanced reproducibility of L-mode plasma discharges via physics-model-based q-profile feedback control in DIII-D

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Schuster, Eugenio J.; Wehner, William P.; Barton, Joseph E.

    Recent experiments on DIII-D demonstrate the potential of physics-model-based q-profile control to improve reproducibility of plasma discharges. A combined feed forward + feedback control scheme is employed to optimize the current ramp-up phase by consistently achieving target q profiles (Target 1: q min = 1.3,q 95 = 4:4; Target 2: q min = 1.65,q 95 = 5.0; Target 3: q min = 2.1,q 95 = 6:2) at prescribed times during the plasma formation phase (Target 1: t = 1.5 s; Target 2: t = 1:3 s; Target 3: t = 1.0 s). At the core of the control scheme ismore » a nonlinear, first-principles-driven, physics-based, control-oriented model of the plasma dynamics valid for low confinement (L-mode) scenarios. To prevent undesired L-H transitions, a constraint on the maximum allowable total auxiliary power is imposed in addition to the maximum powers for the individual heating and current-drive sources. Experimental results are presented to demonstrate the effectiveness of the combined feed forward + feedback control scheme to consistently achieve the desired target profiles at the predefined times. Here, these results also show how the addition of feedback control significantly improves upon the feed forward only control solution by reducing the matching error and also how the feedback controller is able to reduce the matching error as the constraint on the maximum allowable total auxiliary power is relaxed while keeping the plasma in L-mode.« less

  14. Enhanced reproducibility of L-mode plasma discharges via physics-model-based q-profile feedback control in DIII-D

    DOE PAGES

    Schuster, Eugenio J.; Wehner, William P.; Barton, Joseph E.; ...

    2017-08-09

    Recent experiments on DIII-D demonstrate the potential of physics-model-based q-profile control to improve reproducibility of plasma discharges. A combined feed forward + feedback control scheme is employed to optimize the current ramp-up phase by consistently achieving target q profiles (Target 1: q min = 1.3,q 95 = 4:4; Target 2: q min = 1.65,q 95 = 5.0; Target 3: q min = 2.1,q 95 = 6:2) at prescribed times during the plasma formation phase (Target 1: t = 1.5 s; Target 2: t = 1:3 s; Target 3: t = 1.0 s). At the core of the control scheme ismore » a nonlinear, first-principles-driven, physics-based, control-oriented model of the plasma dynamics valid for low confinement (L-mode) scenarios. To prevent undesired L-H transitions, a constraint on the maximum allowable total auxiliary power is imposed in addition to the maximum powers for the individual heating and current-drive sources. Experimental results are presented to demonstrate the effectiveness of the combined feed forward + feedback control scheme to consistently achieve the desired target profiles at the predefined times. Here, these results also show how the addition of feedback control significantly improves upon the feed forward only control solution by reducing the matching error and also how the feedback controller is able to reduce the matching error as the constraint on the maximum allowable total auxiliary power is relaxed while keeping the plasma in L-mode.« less

  15. Experiments and Simulations of ITER-like Plasmas in Alcator C-Mod

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    .R. Wilson, C.E. Kessel, S. Wolfe, I.H. Hutchinson, P. Bonoli, C. Fiore, A.E. Hubbard, J. Hughes, Y. Lin, Y. Ma, D. Mikkelsen, M. Reinke, S. Scott, A.C.C. Sips, S. Wukitch and the C-Mod Team

    Alcator C-Mod is performing ITER-like experiments to benchmark and verify projections to 15 MA ELMy H-mode Inductive ITER discharges. The main focus has been on the transient ramp phases. The plasma current in C-Mod is 1.3 MA and toroidal field is 5.4 T. Both Ohmic and ion cyclotron (ICRF) heated discharges are examined. Plasma current rampup experiments have demonstrated that (ICRF and LH) heating in the rise phase can save voltseconds (V-s), as was predicted for ITER by simulations, but showed that the ICRF had no effect on the current profile versus Ohmic discharges. Rampdown experiments show an overcurrent inmore » the Ohmic coil (OH) at the H to L transition, which can be mitigated by remaining in H-mode into the rampdown. Experiments have shown that when the EDA H-mode is preserved well into the rampdown phase, the density and temperature pedestal heights decrease during the plasma current rampdown. Simulations of the full C-Mod discharges have been done with the Tokamak Simulation Code (TSC) and the Coppi-Tang energy transport model is used with modified settings to provide the best fit to the experimental electron temperature profile. Other transport models have been examined also. __________________________________________________« less

  16. Equilibrium evolution in oscillating-field current-drive experiments

    NASA Astrophysics Data System (ADS)

    McCollam, K. J.; Anderson, J. K.; Blair, A. P.; Craig, D.; Den Hartog, D. J.; Ebrahimi, F.; O'Connell, R.; Reusch, J. A.; Sarff, J. S.; Stephens, H. D.; Stone, D. R.; Brower, D. L.; Deng, B. H.; Ding, W. X.

    2010-08-01

    Oscillating-field current drive (OFCD) is a proposed method of steady-state toroidal plasma sustainment in which ac poloidal and toroidal loop voltages are applied to produce a dc plasma current. OFCD is added to standard, inductively sustained reversed-field pinch plasmas in the Madison Symmetric Torus [R. N. Dexter et al., Fusion Technol. 19, 131 (1991)]. Equilibrium profiles and fluctuations during a single cycle are measured and analyzed for different relative phases between the two OFCD voltages and for OFCD off. For OFCD phases leading to the most added plasma current, the measured energy confinement is slightly better than that for OFCD off. By contrast, the phase of the maximum OFCD helicity-injection rate also has the maximum decay rate, which is ascribed to transport losses during discrete magnetic-fluctuation events induced by OFCD. Resistive-magnetohydrodynamic simulations of the experiments reproduce the observed phase dependence of the added current.

  17. Profile measurements in the plasma edge of mega amp spherical tokamak using a ball pen probe

    NASA Astrophysics Data System (ADS)

    Walkden, N. R.; Adamek, J.; Allan, S.; Dudson, B. D.; Elmore, S.; Fishpool, G.; Harrison, J.; Kirk, A.; Komm, M.

    2015-02-01

    The ball pen probe (BPP) technique is used successfully to make profile measurements of plasma potential, electron temperature, and radial electric field on the Mega Amp Spherical Tokamak. The potential profile measured by the BPP is shown to significantly differ from the floating potential both in polarity and profile shape. By combining the BPP potential and the floating potential, the electron temperature can be measured, which is compared with the Thomson scattering (TS) diagnostic. Excellent agreement between the two diagnostics is obtained when secondary electron emission is accounted for in the floating potential. From the BPP profile, an estimate of the radial electric field is extracted which is shown to be of the order ˜1 kV/m and increases with plasma current. Corrections to the BPP measurement, constrained by the TS comparison, introduce uncertainty into the ER measurements. The uncertainty is most significant in the electric field well inside the separatrix. The electric field is used to estimate toroidal and poloidal rotation velocities from E × B motion. This paper further demonstrates the ability of the ball pen probe to make valuable and important measurements in the boundary plasma of a tokamak.

  18. Radial scanning diagnostics of bremsstrahlung and line emission in T-10 plasma

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nemets, A. R., E-mail: Nemets-AR@nrcki.ru; Krupin, V. A.; Klyuchnikov, L. A., E-mail: lklyuchnikov@list.ru

    2016-12-15

    The paper describes the scanning spectroscopic diagnostics designed for measurement of line integrated plasma radiation in two visible spectral ranges. This diagnostic system is aimed at measuring the bremsstrahlung absolute values and profile with high spatial resolution. The bremsstrahlung absolute values are used to determine the value and radial distribution of effective plasma ion charge Z{sub eff}(r) in T-10 discharges. The importance of Z{sub eff} measurement is due to its strong influence on plasma heating, confinement, and stability. The spatial distribution of emission for one of the chosen spectral lines is measured simultaneously with bremsstrahlung. The spatial resolution of measurementsmore » is ~1 cm, and the temporal resolution is up to 10 ms. The spectral equipment and methods for its calibration are described. Examples of line integrated brightness distribution in a “continuum window” of 5236 ± 6 Å and brightness of the lines C{sup 5+} (5291 Å), He{sup 1+} (4686 Å), and D{sub β} (4861 Å) are given. Flattening of the bremsstrahlung brightness profile in the central region of the plasma column in some discharges with sawtooth oscillations in the T-10 is observed. The measured effective ion charge profiles in ohmic discharges with high plasma density and low discharge currents demonstrate accumulation of light impurities at the column axis; as a consequence, quenching of sawtooth oscillations in some discharges is observed. The developed diagnostics provides necessary data for investigation of heat, particle, and current transport in the plasma of the T-10. Successful application of the obtained data on Z{sub eff}(r) for investigation of geodesic acoustic modes of plasma oscillations in the T-10 should be specially noted.« less

  19. Thermal island destabilization and the Greenwald limit

    DOE PAGES

    White, R. B.; Gates, D. A.; Brennan, D. P.

    2015-02-24

    Magnetic reconnection is ubiquitous in the magnetosphere, the solar corona, and in toroidal fusion research discharges. A magnetic island saturates at a width which produces a minimum in the magnetic energy of the configuration is evident in a fusion device. At saturation, the modified current density profile, a function of the flux in the island, is essentially flat, the growth rate proportional to the difference in the current at the O-point and the X-point. Furthermore, modification of the current density profile in the island interior causes a change in the island stability and additional growth or contraction of the saturatedmore » island. Because field lines in an island are isolated from the outside plasma, an island can heat or cool preferentially depending on the balance of Ohmic heating and radiation loss in the interior, changing the resistivity and hence the current in the island. A simple model of island destabilization due to radiation cooling of the island is constructed, and the effect of modification of the current within an island is calculated. In addition destabilization effect is described, and it is shown that a small imbalance of heating can lead to exponential growth of the island. A destabilized magnetic island near the plasma edge can lead to plasma loss, and because the radiation is proportional to plasma density and charge, this effect can cause an impurity dependent density limit.« less

  20. Thermal island destabilization and the Greenwald limit

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    White, R. B.; Gates, D. A.; Brennan, D. P.

    Magnetic reconnection is ubiquitous in the magnetosphere, the solar corona, and in toroidal fusion research discharges. A magnetic island saturates at a width which produces a minimum in the magnetic energy of the configuration is evident in a fusion device. At saturation, the modified current density profile, a function of the flux in the island, is essentially flat, the growth rate proportional to the difference in the current at the O-point and the X-point. Furthermore, modification of the current density profile in the island interior causes a change in the island stability and additional growth or contraction of the saturatedmore » island. Because field lines in an island are isolated from the outside plasma, an island can heat or cool preferentially depending on the balance of Ohmic heating and radiation loss in the interior, changing the resistivity and hence the current in the island. A simple model of island destabilization due to radiation cooling of the island is constructed, and the effect of modification of the current within an island is calculated. In addition destabilization effect is described, and it is shown that a small imbalance of heating can lead to exponential growth of the island. A destabilized magnetic island near the plasma edge can lead to plasma loss, and because the radiation is proportional to plasma density and charge, this effect can cause an impurity dependent density limit.« less

  1. Thermal island destabilization and the Greenwald limit

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    White, R. B.; Gates, D. A.; Brennan, D. P.

    Magnetic reconnection is ubiquitous in the magnetosphere, the solar corona, and in toroidal fusion research discharges. In a fusion device, a magnetic island saturates at a width which produces a minimum in the magnetic energy of the configuration. At saturation, the modified current density profile, a function of the flux in the island, is essentially flat, the growth rate proportional to the difference in the current at the O-point and the X-point. Further modification of the current density profile in the island interior causes a change in the island stability and additional growth or contraction of the saturated island. Becausemore » field lines in an island are isolated from the outside plasma, an island can heat or cool preferentially depending on the balance of Ohmic heating and radiation loss in the interior, changing the resistivity and hence the current in the island. A simple model of island destabilization due to radiation cooling of the island is constructed, and the effect of modification of the current within an island is calculated. An additional destabilization effect is described, and it is shown that a small imbalance of heating can lead to exponential growth of the island. A destabilized magnetic island near the plasma edge can lead to plasma loss, and because the radiation is proportional to plasma density and charge, this effect can cause an impurity dependent density limit.« less

  2. High Protein Intake Does Not Prevent Low Plasma Levels of Conditionally Essential Amino Acids in Very Preterm Infants Receiving Parenteral Nutrition.

    PubMed

    Morgan, Colin; Burgess, Laura

    2017-03-01

    We have shown that increasing protein intake using a standardized, concentrated, added macronutrients parenteral (SCAMP) nutrition regimen improves head growth in very preterm infants (VPIs) compared with a control parenteral nutrition (PN) regimen. VPIs are at risk of conditionally essential amino acid (CEAA) deficiencies because of current neonatal PN amino acid (AA) formulations. We hypothesized that the SCAMP regimen would prevent low plasma levels of CEAAs. To compare the plasma AA profiles at approximately day 9 of life in VPIs receiving SCAMP vs a control PN regimen. VPIs (<29 weeks' gestation) were randomized to receive SCAMP (30% more PN AA) or a control regimen. Data were collected to measure parenteral and enteral protein, energy, and individual AA intake and the first plasma AA profile. Plasma profiles of the 20 individual protogenic AA levels were measured using ion exchange chromatography. Plasma AA profiles were obtained at median (interquartile range [IQR]) age of 9 (8-10) days in both SCAMP (n = 59) and control (n = 67) groups after randomizing 150 VPIs. Median (IQR) plasma levels of individual essential AAs were higher than the reference population mean (RPM) in both groups, especially for threonine. SCAMP infants had higher plasma levels of essential AAs than did the controls. Median (IQR) plasma levels of glutamine, arginine, and cysteine (CEAAs) were lower than the RPM in both groups. Plasma AA levels in PN-dependent VPIs indicate there is an imbalance in essential and CEAA provision in neonatal PN AA formulations that is not improved by increasing protein intake.

  3. Plasma Rotation and Radial Electric Field Response to Resonant Magnetic Perturbations in DIII-D

    NASA Astrophysics Data System (ADS)

    Moyer, R. A.

    2012-10-01

    Analysis of DIII-D experiments have revealed a complex picture of the evolution of the toroidal rotation vtor and radial electric field Er when applying edge resonant magnetic perturbations (RMPs) in H-mode plasmas. Measurements indicate that RMPs induce changes to the plasma rotation and Er across the plasma profile, well into the plasma core where islands or stochasticity are not expected. In the pedestal, the change in Er comes primarily from the vxB changes even though the ion diamagnetic contribution to Er is larger. This allows the RMP to change Er faster than the transport timescale for altering the pressure gradient. For n=3 RMPs, the pedestal vtor goes to zero as fast as the RMP current rises, suggesting increased toroidal viscosity with the RMP, followed by a slow rise in co-plasma current vtor (pedestal ``spin-up'') as the pedestal density pumps out. This spin-up could result from a reduction in ELM-induced momentum transport or a resonant jxB torque due to radial current. As vtor becomes more positive and the pressure pedestal narrows, the electron perpendicular rotation ˜0 point moves out toward the top of the pedestal; increasing the RMP current moves this crossing point closer to the top of the pedestal. These changes reduce the mean ExB shearing rate across the outer half of the discharge from several times the linear growth rate for intermediate-scale turbulence to less than the linear growth rate, consistent with increased turbulent transport. Full-f kinetic simulations with self-consistent plasma response and Er using the XGC0 code have qualitatively reproduced the observed profile and Er changes. These results suggest that similar to their role in regulating H-mode plasma transport and stability, plasma rotation and Er play a critical role in the effect of RMPs on plasma performance.

  4. Three dimensional equilibrium solutions for a current-carrying reversed-field pinch plasma with a close-fitting conducting shell

    DOE PAGES

    Koliner, J. J.; Boguski, J.; Anderson, J. K.; ...

    2016-03-25

    In order to characterize the Madison Symmetric Torus (MST) reversed-field pinch(RFP)plasmas that bifurcate to a helical equilibrium, the V3FIT equilibrium reconstruction code was modified to include a conducting boundary. RFPplasmas become helical at a high plasma current, which induces large eddy currents in MST's thick aluminum shell. The V3FIT conducting boundary accounts for the contribution from these eddy currents to external magnetic diagnostic coil signals. This implementation of V3FIT was benchmarked against MSTFit, a 2D Grad-Shafranov solver, for axisymmetric plasmas. The two codes both fit B measurement loops around the plasma minor diameter with qualitative agreement between each other andmore » the measured field. Fits in the 3D case converge well, with q-profile and plasma shape agreement between two distinct toroidal locking phases. Greater than 60% of the measured n = 5 component of B at r = a is due to eddy currents in the shell, as calculated by the conducting boundary model.« less

  5. Modifications to the edge current profile with auxiliary edge current drive and improved confinement in a reversed-field pinch

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chapman, B. E.; Biewer, T. M.; Chattopadhyay, P. K.

    2000-09-01

    Auxiliary edge current drive is routinely applied in the Madison Symmetric Torus [R. N. Dexter, D. W. Kerst, T. W. Lovell et al., Fusion Technol. 19, 131 (1991)] with the goal of modifying the parallel current profile to reduce current-driven magnetic fluctuations and the associated particle and energy transport. Provided by an inductive electric field, the current drive successfully reduces fluctuations and transport. First-time measurements of the modified edge current profile reveal that, relative to discharges without auxiliary current drive, the edge current density decreases. This decrease is explicable in terms of newly measured reductions in the dynamo (fluctuation-based) electricmore » field and the electrical conductivity. Induced by the current drive, these two changes to the edge plasma play as much of a role in determining the resultant edge current profile as does the current drive itself. (c) 2000 American Institute of Physics.« less

  6. Unstable domains of tearing and Kelvin-Helmholtz instabilities in a rotating cylindrical plasma

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fan, D. M.; Wei, L.; Wang, Z. X., E-mail: zxwang@dlut.edu.cn

    2014-09-15

    Effects of poloidal rotation profile on tearing and Kelvin-Helmholtz (KH) instabilities in a cylindrical plasma are investigated by using a reduced magnetohydrodynamic model. Since the poloidal rotation has different effects on the tearing and KH modes in different rotation regimes, four unstable domains are numerically identified, i.e., the destabilized tearing mode domain, stabilized tearing mode domain, stable-window domain, and unstable KH mode domain. It is also found that when the rotation layer is in the outer region of the rational surface, the stabilizing role of the rotation can be enhanced so significantly that the stable window domain is enlarged. Moreover,more » Alfvén resonances can be induced by the tearing and KH modes in such rotating plasmas. Radially wide profiles of current and vorticity perturbations can be formed when multiple current sheets on different resonance positions are coupled together.« less

  7. Test of bootstrap current models using high- β p EAST-demonstration plasmas on DIII-D

    DOE PAGES

    Ren, Qilong; Lao, Lang L.; Garofalo, Andrea M.; ...

    2015-01-12

    Magnetic measurements together with kinetic profile and motional Stark effect measurements are used in full kinetic equilibrium reconstructions to test the Sauter and NEO bootstrap current models in a DIII-D high-more » $${{\\beta}_{\\text{p}}}$$ EAST-demonstration experiment. This aims at developing on DIII-D a high bootstrap current scenario to be extended on EAST for a demonstration of true steady-state at high performance and uses EAST-similar operational conditions: plasma shape, plasma current, toroidal magnetic field, total heating power and current ramp-up rate. It is found that the large edge bootstrap current in these high-$${{\\beta}_{\\text{p}}}$$ plasmas allows the use of magnetic measurements to clearly distinguish the two bootstrap current models. In these high collisionality and high-$${{\\beta}_{\\text{p}}}$$ plasmas, the Sauter model overpredicts the peak of the edge current density by about 30%, while the first-principle kinetic NEO model is in close agreement with the edge current density of the reconstructed equilibrium. Furthermore, these results are consistent with recent work showing that the Sauter model largely overestimates the edge bootstrap current at high collisionality.« less

  8. The DIII-D Plasma Control System as a Scientific Research Tool

    NASA Astrophysics Data System (ADS)

    Hyatt, A. W.; Ferron, J. R.; Humphreys, D. A.; Leuer, J. A.; Walker, M. L.; Welander, A. S.

    2006-10-01

    The digital plasma control system (PCS) is an essential element of the DIII-D tokamak as a scientific research instrument, providing experimenters with real-time measurement and control of the plasma equilibrium, heating, current drive, transport, stability, and plasma-wall interactions. A wide range of sensors and actuators allow feedback control not only of global quantities such as discharge shape, plasma energy, and toroidal rotation, but also of non-axisymmetric magnetic fields and features of the internal profiles of temperature and current density. These diverse capabilities of the PCS improve the effectiveness of tokamak operation and enable unique physics experiments. We will present an overview of the PCS and the systems it controls and interacts with, and show examples of various plasma parameters controlled by the PCS and its actuators.

  9. Inductive current startup in large tokamaks with expanding minor radius and rf assist

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Borowski, S.K.

    1984-02-01

    Auxiliary rf heating of electrons before and during the current-rise phase of a large tokamak, such as the Fusion Engineering Device (R = 4.8 m, a = 1.3 m, sigma = 1.6, B/sub T/ = 3.62 T), is examined as a means of reducing both the initiation loop voltage and resistive flux expenditure during startup. Prior to current initiation, 1 to 2 MW of electron cyclotron resonance heating power at approx. 90 GHz is used to create a small volume of high conductivity plasma (T/sub e/ approx. = 100 eV, n/sub e/ approx. = 10/sup 19/ m/sup -3/) near themore » upper hybrid resonance (UHR) region. This plasma conditioning permits a small radius (a/sub 0/ approx. = 0.2 to 0.4 m) current channel to be established with a relatively low initial loop voltage (less than or equal to 25 V as opposed to approx. 100 V without rf assist). During the subsequent plasma expansion and current ramp phase, a combination of rf heating (up to 5 MW) and current profile control leads to a substantial savings in volt-seconds by: (1) minimizing the resistive flux consumption; and (2) maintaining the internal flux at or near the flat profile limit.« less

  10. High-beta, steady-state hybrid scenario on DIII-D

    DOE PAGES

    Petty, C. C.; Kinsey, J. E.; Holcomb, C. T.; ...

    2015-12-17

    Here, the potential of the hybrid scenario (first developed as an advanced inductive scenario for high fluence) as a regime for high-beta, steady-state plasmas is demonstrated on the DIII-D tokamak. These experiments show that the beneficial characteristics of hybrids, namely safety factor ≥1 with low central magnetic shear, high stability limits and excellent confinement, are maintained when strong central current drive (electron cyclotron and neutral beam) is applied to increase the calculated non-inductive fraction to ≈100% (≈50% bootstrap current). The best discharges achieve normalized beta of 3.4, IPB98(y,2) confinement factor of 1.4, surface loop voltage of 0.01 V, and nearlymore » equal electron and ion temperatures at low collisionality. A zero-dimensional physics model shows that steady-state hybrid operation with Q fus ~ 5 is feasible in FDF and ITER. The advantage of the hybrid scenario as an Advanced Tokamak regime is that the external current drive can be deposited near the plasma axis where the efficiency is high; additionally, good alignment between the current drive and plasma current profiles is not necessary as the poloidal magnetic flux pumping self-organizes the current density profile in hybrids with an m/n=3/2 tearing mode.« less

  11. Measurements of plasma profiles using a fast swept Langmuir probe in the VINETA-II magnetic reconnection experiment

    NASA Astrophysics Data System (ADS)

    Shesterikov, I.; Von Stechow, A.; Grulke, O.; Stenzel, R.; Klinger, T.

    2017-07-01

    A fast-swept Langmuir probe capable to be biased at a high voltages has been constructed and successfully operated at the VINETA-II magnetic reconnection experiment. The presented circuit has two main features beneficial for fast transient parameter changes in laboratory experiments as, e.g., plasma guns or magnetic reconnection: the implementation simplicity and the high voltage sweep range. This work presents its design and performance for time-dependent measurements of VINETA-II plasmas. The probe is biased with a sinusoidal voltage at a fixed frequency. Current - voltage characteristics are measured along the falling and rising slopes of the probe bias. The sweep frequency is fsweep= 150 kHz. The spatiotemporal evolution of radial plasma profiles is obtained by evaluation of the probe characteristics. The plasma density measurements agree with those derived from a microwave interferometer, demonstrating the reliability of the measurements. As a model plasma system, a plasma gun discharge with typical pulse times of 60 μ s is chosen.

  12. Beam current enhancement of microwave plasma ion source utilizing double-port rectangular cavity resonator.

    PubMed

    Lee, Yuna; Park, Yeong-Shin; Jo, Jong-Gab; Yang, J J; Hwang, Y S

    2012-02-01

    Microwave plasma ion source with rectangular cavity resonator has been examined to improve ion beam current by changing wave launcher type from single-port to double-port. The cavity resonators with double-port and single-port wave launchers are designed to get resonance effect at TE-103 mode and TE-102 mode, respectively. In order to confirm that the cavities are acting as resonator, the microwave power for breakdown is measured and compared with the E-field strength estimated from the HFSS (High Frequency Structure Simulator) simulation. Langmuir probe measurements show that double-port cavity enhances central density of plasma ion source by modifying non-uniform plasma density profile of the single-port cavity. Correspondingly, beam current from the plasma ion source utilizing the double-port resonator is measured to be higher than that utilizing single-port resonator. Moreover, the enhancement in plasma density and ion beam current utilizing the double-port resonator is more pronounced as higher microwave power applied to the plasma ion source. Therefore, the rectangular cavity resonator utilizing the double-port is expected to enhance the performance of plasma ion source in terms of ion beam extraction.

  13. Formation and sustainment of internal transport barriers in the International Thermonuclear Experimental Reactor with the baseline heating mixa)

    NASA Astrophysics Data System (ADS)

    Poli, Francesca M.; Kessel, Charles E.

    2013-05-01

    Plasmas with internal transport barriers (ITBs) are a potential and attractive route to steady-state operation in ITER. These plasmas exhibit radially localized regions of improved confinement with steep pressure gradients in the plasma core, which drive large bootstrap current and generate hollow current profiles and negative magnetic shear. This work examines the formation and sustainment of ITBs in ITER with electron cyclotron heating and current drive. The time-dependent transport simulations indicate that, with a trade-off of the power delivered to the equatorial and to the upper launcher, the sustainment of steady-state ITBs can be demonstrated in ITER with the baseline heating configuration.

  14. Sex specific differences in hepatic and plasma lipid profiles in healthy cats pre and post spaying and neutering: relationship with feline hepatic lipidosis.

    PubMed

    Valtolina, Chiara; Vaandrager, Arie B; Favier, Robert P; Tuohetahuntila, Maidina; Kummeling, Anne; Jeusette, Isabelle; Rothuizen, Jan; Robben, Joris H

    2017-08-08

    A link between lipid metabolism and disease has been recognized in cats. Since hepatic lipidosis is a frequent disorder in cats, the aim of the current study was to evaluate liver and plasma lipid dimorphism in healthy cats and the effects of gonadectomy on lipid profiling. From six female and six male cats plasma and liver lipid profiles before and after spaying/neutering were assessed and compared to five cats (three neutered male and two spayed female) diagnosed with hepatic lipidosis. Intact female cats had a significantly lower level of plasma triacylglycerides (TAG) and a higher liver level of the long chain polyunsaturated fatty acid arachidonic acid (AA) compared to their neutered state. Both male and female cats with lipidosis had a higher liver, but not plasma TAG level and an increased level of plasma and liver sphingomyelin compared to the healthy cats. Although lipid dimorphism in healthy cats resembles that of other species, intact female cats show differences in metabolic configuration that could predispose them to develop hepatic lipidosis. The increased sphingomyelin levels in cats with lipidosis could suggest a potential role in the pathogenesis of hepatic lipidosis in cats.

  15. DOE Office of Scientific and Technical Information (OSTI.GOV)

    Popovich, P.; Carter, T. A.; Friedman, B.

    Numerical simulation of plasma turbulence in the Large Plasma Device (LAPD) [W. Gekelman, H. Pfister, Z. Lucky et al., Rev. Sci. Instrum. 62, 2875 (1991)] is presented. The model, implemented in the BOUndary Turbulence code [M. Umansky, X. Xu, B. Dudson et al., Contrib. Plasma Phys. 180, 887 (2009)], includes three-dimensional (3D) collisional fluid equations for plasma density, electron parallel momentum, and current continuity, and also includes the effects of ion-neutral collisions. In nonlinear simulations using measured LAPD density profiles but assuming constant temperature profile for simplicity, self-consistent evolution of instabilities and nonlinearly generated zonal flows results in a saturatedmore » turbulent state. Comparisons of these simulations with measurements in LAPD plasmas reveal good qualitative and reasonable quantitative agreement, in particular in frequency spectrum, spatial correlation, and amplitude probability distribution function of density fluctuations. For comparison with LAPD measurements, the plasma density profile in simulations is maintained either by direct azimuthal averaging on each time step, or by adding particle source/sink function. The inferred source/sink values are consistent with the estimated ionization source and parallel losses in LAPD. These simulations lay the groundwork for more a comprehensive effort to test fluid turbulence simulation against LAPD data.« less

  16. Diagnostic value of plasma and bronchoalveolar lavage samples in acute lung allograft rejection: differential cytology.

    PubMed

    Speck, Nicole E; Schuurmans, Macé M; Murer, Christian; Benden, Christian; Huber, Lars C

    2016-06-21

    Diagnosis of acute lung allograft rejection is currently based on transbronchial lung biopsies. Additional methods to detect acute allograft dysfunction derived from plasma and bronchoalveolar lavage samples might facilitate diagnosis and ultimately improve allograft survival. This review article gives an overview of the cell profiles of bronchoalveolar lavage and plasma samples during acute lung allograft rejection. The value of these cells and changes within the pattern of differential cytology to support the diagnosis of acute lung allograft rejection is discussed. Current findings on the topic are highlighted and trends for future research are identified.

  17. Global plasma oscillations in electron internal transport barriers in TCV

    NASA Astrophysics Data System (ADS)

    Udintsev, V. S.; Sauter, O.; Asp, E.; Fable, E.; Goodman, T. P.; Turri, G.; Graves, J. P.; Scarabosio, A.; Zhuang, G.; Zucca, C.; TCV Team

    2008-12-01

    In the Tokamak à Configuration Variable (TCV) (Hofmann F et al1994 Plasma Phys. Control. Fusion 36 B277), global plasma oscillations have been discovered in fully non-inductively driven plasmas featuring electron internal transport barriers (ITB) with strong ECRH/ECCD. These oscillations are linked to the destabilization and stabilization of MHD modes near the foot of the ITB and can lead to large oscillations of the total plasma current and line-averaged density, among others. They are intrinsically related to the fact that ITBs have large pressure gradients in a region of low magnetic shear. Therefore, the ideal MHD limit is relatively low and infernal modes can be unstable. Depending on the proximity to the ideal limit, small crashes or resistive modes can appear which affect the time evolution of the discharge. Being near marginal stability, the modes can self-stabilize due to the modification of the pressure gradient and local q-profile. The plasma recovers good confinement, reverses shear and the ITB builds up, until a new MHD mode is destabilized. TCV results show that this cycling behaviour can be controlled by modifying the current density or the pressure profiles, either with Ohmic current density perturbation or by modifying the ECH/ECCD power. It is demonstrated that many observations such as q >= 2 sawteeth, beta collapses, minor disruptions and oscillation regimes in ITBs can be assigned to the same physics origin: the proximity to the infernal mode stability limit.

  18. Non-inductively driven tokamak plasmas at near-unity βt in the Pegasus toroidal experiment

    NASA Astrophysics Data System (ADS)

    Reusch, J. A.; Bodner, G. M.; Bongard, M. W.; Burke, M. G.; Fonck, R. J.; Pachicano, J. L.; Perry, J. M.; Pierren, C.; Rhodes, A. T.; Richner, N. J.; Rodriguez Sanchez, C.; Schlossberg, D. J.; Weberski, J. D.

    2018-05-01

    A major goal of the spherical tokamak (ST) research program is accessing a state of low internal inductance ℓi, high elongation κ, and high toroidal and normalized beta ( βt and βN) without solenoidal current drive. Local helicity injection (LHI) in the Pegasus ST [Garstka et al., Nucl. Fusion 46, S603 (2006)] provides non-solenoidally driven plasmas that exhibit these characteristics. LHI utilizes compact, edge-localized current sources for plasma startup and sustainment. It results in hollow current density profiles with low ℓi. The low aspect ratio ( R0/a ˜1.2 ) of Pegasus allows access to high κ and high normalized plasma currents ( IN=Ip/a BT>14 ). Magnetic reconnection during LHI provides auxiliary ion heating. Together, these features provide access to very high βt plasmas. Equilibrium analyses indicate that βt up to ˜100% is achieved. These high βt discharges disrupt at the ideal no-wall β limit at βN˜7.

  19. Algebraic motion of vertically displacing plasmas

    DOE PAGES

    Pfefferle, D.; Bhattacharjee, A.

    2018-02-27

    In this paper, the vertical motion of a tokamak plasma is analytically modelled during its non-linear phase by a free-moving current-carrying rod inductively coupled to a set of fixed conducting wires or a cylindrical conducting shell. The solutions capture the leading term in a Taylor expansion of the Green's function for the interaction between the plasma column and the surrounding vacuum vessel. The plasma shape and profiles are assumed not to vary during the vertical drifting phase such that the plasma column behaves as a rigid body. In the limit of perfectly conducting structures, the plasma is prevented to comemore » in contact with the wall due to steep effective potential barriers created by the induced Eddy currents. Resistivity in the wall allows the equilibrium point to drift towards the vessel on the slow timescale of flux penetration. The initial exponential motion of the plasma, understood as a resistive vertical instability, is succeeded by a non-linear “sinking” behaviour shown to be algebraic and decelerating. Finally, the acceleration of the plasma column often observed in experiments is thus concluded to originate from an early sharing of toroidal current between the core, the halo plasma, and the wall or from the thermal quench dynamics precipitating loss of plasma current.« less

  20. Algebraic motion of vertically displacing plasmas

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pfefferle, D.; Bhattacharjee, A.

    In this paper, the vertical motion of a tokamak plasma is analytically modelled during its non-linear phase by a free-moving current-carrying rod inductively coupled to a set of fixed conducting wires or a cylindrical conducting shell. The solutions capture the leading term in a Taylor expansion of the Green's function for the interaction between the plasma column and the surrounding vacuum vessel. The plasma shape and profiles are assumed not to vary during the vertical drifting phase such that the plasma column behaves as a rigid body. In the limit of perfectly conducting structures, the plasma is prevented to comemore » in contact with the wall due to steep effective potential barriers created by the induced Eddy currents. Resistivity in the wall allows the equilibrium point to drift towards the vessel on the slow timescale of flux penetration. The initial exponential motion of the plasma, understood as a resistive vertical instability, is succeeded by a non-linear “sinking” behaviour shown to be algebraic and decelerating. Finally, the acceleration of the plasma column often observed in experiments is thus concluded to originate from an early sharing of toroidal current between the core, the halo plasma, and the wall or from the thermal quench dynamics precipitating loss of plasma current.« less

  1. Turbulent current drive mechanisms

    NASA Astrophysics Data System (ADS)

    McDevitt, Christopher J.; Tang, Xian-Zhu; Guo, Zehua

    2017-08-01

    Mechanisms through which plasma microturbulence can drive a mean electron plasma current are derived. The efficiency through which these turbulent contributions can drive deviations from neoclassical predictions of the electron current profile is computed by employing a linearized Coulomb collision operator. It is found that a non-diffusive contribution to the electron momentum flux as well as an anomalous electron-ion momentum exchange term provide the most efficient means through which turbulence can modify the mean electron current for the cases considered. Such turbulent contributions appear as an effective EMF within Ohm's law and hence provide an ideal means for driving deviations from neoclassical predictions.

  2. Comparison of fusion alpha performance in JET advanced scenario and H-mode plasmas

    NASA Astrophysics Data System (ADS)

    Asunta, O.; Kurki-Suonio, T.; Tala, T.; Sipilä, S.; Salomaa, R.; contributors, JET-EFDA

    2008-12-01

    Currently, plasmas with internal transport barriers (ITBs) appear the most likely candidates for steady-state scenarios for future fusion reactors. In such plasmas, the broad hot and dense region in the plasma core leads to high fusion gain, while the cool edge protects the integrity of the first wall. Economically desirable large bootstrap current fraction and low inductive current drive may, however, lead to degraded fast ion confinement. In this work the confinement and heating profile of fusion alphas were compared between H-mode and ITB plasmas in realistic JET geometry. The work was carried out using the Monte Carlo-based guiding-center-following code ASCOT. For the same plasma current, the ITB discharges were found to produce four to eight times more fusion power than a comparable ELMy H-mode discharge. Unfortunately, also the alpha particle losses were larger (~16%) compared with the H-mode discharge (7%). In the H-mode discharges, alpha power was deposited to the plasma symmetrically around the magnetic axis, whereas in the current-hole discharge, the power was spread out to a larger volume in the plasma center. This was due to wider particle orbits, and the magnetic structure allowing for a broader hot region in the centre.

  3. Investigation of the residue in an electric rail gun employing a plasma armature

    NASA Technical Reports Server (NTRS)

    Bauer, D. P.; Barber, J. P.

    1984-01-01

    The performance of dc electric rail guns using plasma-armature-accelerated projectiles was studied. It was found that the initial rail launcher acceleration profile was consistent with the simulation, but that after the projectile had traveled approximately 25 to 30 cm along the gun, a considerable portion of the current in the projectile armature commutated into a secondary current path. Also noted were the lower than expected muzzle velocities. It was proposed that the secondary current path was a relatively high conductivity layer of residue on the launcher bore.

  4. Laboratory simulation of the electrodynamic interactions of a tethered satellite with an ionospheric plasma

    NASA Technical Reports Server (NTRS)

    Bonifazi, C.; Lebreton, J. P.; Vannaroni, G.; Cosmovici, C.; Debrie, R.; Hamelin, M.; Pomathiod, L.; Arends, H.

    1986-01-01

    An improved experimental set-up in the Orleans Plasma Chamber allowed investigations of the I-V characteristics of a conductive spherical body (10 cm diameter) in a plasma environment. Moreover, the influence of a transversal magnetic field at 0.6 and 1.2 G was investigated, for the first time, both on the sheath potential profile and current collection. Floating potential profiles were measured at 16 different radial distances from the test body up to 9 body radii in 8 different angular positions. The test body potential could be increased in the range from -200 V up to +100 V. Preliminary results are shown and discussed.

  5. An investigation of transient pressure and plasma properties in a pinched plasma column. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Stover, E. K.; York, T. M.

    1971-01-01

    The transient pinched plasma column generated in a linear Z-pinch was studied experimentally and analytically. The plasma column was investigated experimentally with the following plasma diagnostics: a special rapid response pressure transducer, a magnetic field probe, a voltage probe and discharge luminosity. Axial pressure profiles on the discharge chamber axis were used to identify three characteristic regions of plasma column behavior; they were in temporal sequence: strong axial pressure asymmetry noted early in plasma column lifetime followed by plasma heating in which there is a rapid rise in static pressure and a slight decrease static pressure before plasma column breakup. Plasma column lifetime was approximately 5 microseconds. The axial pressure asymmetry was attributed to nonsimultaneous pinching of the imploding current sheet along the discharge chamber axis. The rapid heating is attributed in part to viscous effects introduced by radial gradients in the axial streaming velocity. Turbulent heating arising from discharge current excitation of the ion acoustic wave instability is also considered a possible heating mechanism.

  6. Profile measurements in the plasma edge of mega amp spherical tokamak using a ball pen probe

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Walkden, N. R., E-mail: nrw504@york.ac.uk; Department of Physics, York Plasma Institute, University of York, Heslington, York YO10 5DD; Adamek, J.

    The ball pen probe (BPP) technique is used successfully to make profile measurements of plasma potential, electron temperature, and radial electric field on the Mega Amp Spherical Tokamak. The potential profile measured by the BPP is shown to significantly differ from the floating potential both in polarity and profile shape. By combining the BPP potential and the floating potential, the electron temperature can be measured, which is compared with the Thomson scattering (TS) diagnostic. Excellent agreement between the two diagnostics is obtained when secondary electron emission is accounted for in the floating potential. From the BPP profile, an estimate ofmore » the radial electric field is extracted which is shown to be of the order ∼1 kV/m and increases with plasma current. Corrections to the BPP measurement, constrained by the TS comparison, introduce uncertainty into the E{sub R} measurements. The uncertainty is most significant in the electric field well inside the separatrix. The electric field is used to estimate toroidal and poloidal rotation velocities from E × B motion. This paper further demonstrates the ability of the ball pen probe to make valuable and important measurements in the boundary plasma of a tokamak.« less

  7. Internal transport barrier triggered by non-linear lower hybrid wave deposition under condition of beam-driven toroidal rotation

    NASA Astrophysics Data System (ADS)

    Gao, Q. D.; Budny, R. V.

    2015-03-01

    By using gyro-Landau fluid transport model (GLF23), time-dependent integrated modeling is carried out using TRANSP to explore the dynamic process of internal transport barrier (ITB) formation in the neutral beam heating discharges. When the current profile is controlled by LHCD (lower hybrid current drive), with appropriate neutral beam injection, the nonlinear interplay between the transport determined gradients in the plasma temperature (Ti,e) and toroidal velocity (Vϕ) and the E×B flow shear (including q-profile) produces transport bifurcations, generating spontaneously a stepwise growing ITB. In the discharge, the constraints imposed by the wave propagation condition causes interplay of the LH driven current distribution with the plasma configuration modification, which constitutes non-linearity in the LH wave deposition. The non-linear effects cause bifurcation in LHCD, generating two distinct quasi-stationary reversed magnetic shear configurations. The change of current profile during the transition period between the two quasi-stationary states results in increase of the E×B shearing flow arising from toroidal rotation. The turbulence transport suppression by sheared E×B flow during the ITB development is analysed, and the temporal evolution of some parameters characterized the plasma confinement is examined. Ample evidence shows that onset of the ITB development is correlated with the enhancement of E×B shearing rate caused by the bifurcation in LHCD. It is suggested that the ITB triggering is associated with the non-linear effects of the LH power deposition.

  8. Toroidal momentum pinch velocity due to the coriolis drift effect on small scale instabilities in a toroidal plasma.

    PubMed

    Peeters, A G; Angioni, C; Strintzi, D

    2007-06-29

    In this Letter, the influence of the "Coriolis drift" on small scale instabilities in toroidal plasmas is shown to generate a toroidal momentum pinch velocity. Such a pinch results because the Coriolis drift generates a coupling between the density and temperature perturbations on the one hand and the perturbed parallel flow velocity on the other. A simple fluid model is used to highlight the physics mechanism and gyro-kinetic calculations are performed to accurately assess the magnitude of the pinch. The derived pinch velocity leads to a radial gradient of the toroidal velocity profile even in the absence of a torque on the plasma and is predicted to generate a peaking of the toroidal velocity profile similar to the peaking of the density profile. Finally, the pinch also affects the interpretation of current experiments.

  9. Toroidal Momentum Pinch Velocity due to the Coriolis Drift Effect on Small Scale Instabilities in a Toroidal Plasma

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Peeters, A. G.; Angioni, C.; Strintzi, D.

    In this Letter, the influence of the ''Coriolis drift'' on small scale instabilities in toroidal plasmas is shown to generate a toroidal momentum pinch velocity. Such a pinch results because the Coriolis drift generates a coupling between the density and temperature perturbations on the one hand and the perturbed parallel flow velocity on the other. A simple fluid model is used to highlight the physics mechanism and gyro-kinetic calculations are performed to accurately assess the magnitude of the pinch. The derived pinch velocity leads to a radial gradient of the toroidal velocity profile even in the absence of a torquemore » on the plasma and is predicted to generate a peaking of the toroidal velocity profile similar to the peaking of the density profile. Finally, the pinch also affects the interpretation of current experiment000.« less

  10. DOE Office of Scientific and Technical Information (OSTI.GOV)

    Medvedev, S. Yu., E-mail: medvedev@a5.kiam.ru; Ivanov, A. A., E-mail: aai@a5.kiam.ru; Martynov, A. A., E-mail: martynov@a5.kiam.ru

    The influence of current density and pressure gradient profiles in the pedestal on the access to the regimes free from edge localized modes (ELMs) like quiescent H-mode in ITER is investigated. Using the simulator of MHD modes localized near plasma boundary based on the KINX code, calculations of the ELM stability were performed for the ITER plasma in scenarios 2 and 4 under variations of density and temperature profiles with the self-consistent bootstrap current in the pedestal. Low pressure gradient values at the separatrix, the same position of the density and temperature pedestals and high poloidal beta values facilitate reachingmore » high current density in the pedestal and a potential transition into the regime with saturated large scale kink modes. New version of the localized MHD mode simulator allows one to compute the growth rates of ideal peeling-ballooning modes with different toroidal mode numbers and to determine the stability region taking into account diamagnetic stabilization. The edge stability diagrams computations and sensitivity studies of the stability limits to the value of diamagnetic frequency show that diamagnetic stabilization of the modes with high toroidal mode numbers can help to access the quiescent H-mode even with high plasma density but only with low pressure gradient values at the separatrix. The limiting pressure at the top of the pedestal increases for higher plasma density. With flat density profile the access to the quiescent H-mode is closed even with diamagnetic stabilization taken into account, while toroidal mode numbers of the most unstable peeling-ballooning mode decrease from n = 10−40 to n = 3−20.« less

  11. Anomalous Ion Heating, Intrinsic and Induced Rotation in the Pegasus Toroidal Experiment

    NASA Astrophysics Data System (ADS)

    Burke, M. G.; Barr, J. L.; Bongard, M. W.; Fonck, R. J.; Hinson, E. T.; Perry, J. M.; Redd, A. J.; Thome, K. E.

    2014-10-01

    Pegasus plasmas are initiated through either standard, MHD stable, inductive current drive or non-solenoidal local helicity injection (LHI) current drive with strong reconnection activity, providing a rich environment to study ion dynamics. During LHI discharges, a large amount of anomalous impurity ion heating has been observed, with Ti ~ 800 eV but Te < 100 eV. The ion heating is hypothesized to be a result of large-scale magnetic reconnection activity, as the amount of heating scales with increasing fluctuation amplitude of the dominant, edge localized, n = 1 MHD mode. Chordal Ti spatial profiles indicate centrally peaked temperatures, suggesting a region of good confinement near the plasma core surrounded by a stochastic region. LHI plasmas are observed to rotate, perhaps due to an inward radial current generated by the stochastization of the plasma edge by the injected current streams. H-mode plasmas are initiated using a combination of high-field side fueling and Ohmic current drive. This regime shows a significant increase in rotation shear compared to L-mode plasmas. In addition, these plasmas have been observed to rotate in the counter-Ip direction without any external momentum sources. The intrinsic rotation direction is consistent with predictions from the saturated Ohmic confinement regime. Work supported by US DOE Grant DE-FG02-96ER54375.

  12. Circuit analysis on the inductance evolution based on electrical signal from various type plasma focus device

    NASA Astrophysics Data System (ADS)

    Mohamad, Saiful Najmee; Ismail, Fairuz Diana; Noorden, Ahmad Fakhrurrazi Ahmad; Haider, Zuhaib; Ali, Jalil

    2017-03-01

    Numerous configurations of plasma focus devices (PFD) have been introduced around the globe. The distinct electrode configuration of the PFD will give out different inductance profile. A circuit analysis has been done to study on the significant difference between the inductance evolution in a coaxial discharge based on various published results of PFD. The discharge current signal, tube voltage and current derivative of the particular shots from distinct PFD was digitized and analyze. The investigation was piloted for three different types of PFD. It was observed that there is a significant difference for the normalize inductance profile during the discharge between the individual PFD with different electrode configuration. The depletion of the radial start current with the normalised inductance development for Mather type (PF-1000) is found to be 25.9% from static discharge. The current depletion continues to drop 1.1% and 1.3% more for a Spherical type (PNK-13) and Filippov type (PF-3) respectively.

  13. DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ferrario, Lorenzo, E-mail: lorenzo.ferrario@polimi.it; Little, Justin M., E-mail: jml@princeton.edu; Choueiri, Edgar Y., E-mail: choueiri@princeton.edu

    The plasma flow in a finite-electron-temperature magnetic nozzle, under the influence of an applied azimuthal current at the throat, is modeled analytically to assess its propulsive performance. A correction to the nozzle throat boundary conditions is derived by modifying the radial equilibrium of a magnetized infinite two-population cylindrical plasma column with the insertion of an external azimuthal body force for the electrons. Inclusion of finite-temperature effects, which leads to a modification of the radial density profile, is necessary for calculating the propulsive performance, which is represented by nozzle divergence efficiency and thrust coefficient. The solutions show that the application ofmore » the azimuthal current enhances all the calculated performance parameters through the narrowing of the radial density profile at the throat, and that investing power in this beam focusing effect is more effective than using the same power to pre-heat the electrons. The results open the possibility for the design of a focusing stage between the plasma source and the nozzle that can significantly enhance the propulsive performance of electron-driven magnetic nozzles.« less

  14. Plasma shape control by pulsed solenoid on laser ion source

    NASA Astrophysics Data System (ADS)

    Sekine, M.; Ikeda, S.; Romanelli, M.; Kumaki, M.; Fuwa, Y.; Kanesue, T.; Hayashizaki, N.; Lambiase, R.; Okamura, M.

    2015-09-01

    A Laser ion source (LIS) provides high current heavy ion beams with a very simple mechanical structure. Plasma is produced by a pulsed laser ablation of a solid state target and ions are extracted by an electric field. However, it was difficult to manipulate the beam parameters of a LIS, since the plasma condition could only be adjusted by the laser irradiation condition. To enhance flexibility of LIS operation, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The experimentally obtained current profile was satisfactorily controlled by the pulsed magnetic field. This approach may also be useful to reduce beam emittance of a LIS.

  15. Plasma shape control by pulsed solenoid on laser ion source

    DOE PAGES

    Sekine, M.; Ikeda, S.; Romanelli, M.; ...

    2015-05-28

    A Laser ion source (LIS) provides high current heavy ion beams with a very simple mechanical structure. Plasma is produced by a pulsed laser ablation of a solid state target and ions are extracted by an electric field. It was difficult to manipulate the beam parameters of a LIS, since the plasma condition could only be adjusted by the laser irradiation condition. To enhance flexibility of LIS operation, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The experimentally obtained current profile was satisfactorily controlled bymore » the pulsed magnetic field. Thus, this approach may also be useful to reduce beam emittance of a LIS.« less

  16. Turbulent current drive mechanisms

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    McDevitt, Christopher J.; Tang, Xian-Zhu; Guo, Zehua

    Mechanisms through which plasma microturbulence can drive a mean electron plasma current are derived. The efficiency through which these turbulent contributions can drive deviations from neoclassical predictions of the electron current profile is computed by employing a linearized Coulomb collision operator. It is found that a non-diffusive contribution to the electron momentum flux as well as an anomalous electron-ion momentum exchange term provide the most efficient means through which turbulence can modify the mean electron current for the cases considered. Such turbulent contributions appear as an effective EMF within Ohm’s law, and hence provide an ideal means for driving deviationsmore » from neoclassical predictions.« less

  17. Turbulent current drive mechanisms

    DOE PAGES

    McDevitt, Christopher J.; Tang, Xian-Zhu; Guo, Zehua

    2017-07-01

    Mechanisms through which plasma microturbulence can drive a mean electron plasma current are derived. The efficiency through which these turbulent contributions can drive deviations from neoclassical predictions of the electron current profile is computed by employing a linearized Coulomb collision operator. It is found that a non-diffusive contribution to the electron momentum flux as well as an anomalous electron-ion momentum exchange term provide the most efficient means through which turbulence can modify the mean electron current for the cases considered. Such turbulent contributions appear as an effective EMF within Ohm’s law, and hence provide an ideal means for driving deviationsmore » from neoclassical predictions.« less

  18. Characteristics of plasma ring, surrounding the Earth at geocentric distances ˜7-10RE, and magnetospheric current systems

    NASA Astrophysics Data System (ADS)

    Antonova, E. E.; Kirpichev, I. P.; Vovchenko, V. V.; Stepanova, M. V.; Riazantseva, M. O.; Pulinets, M. S.; Ovchinnikov, I. L.; Znatkova, S. S.

    2013-07-01

    There are strong experimental evidences of the existence of plasma domain forming a closed plasma ring around the Earth at geocentric distances ∼7-10RE. In this work, we analyze the main properties of this ring, using the data of the THEMIS satellite mission, acquired between April 2007 and September 2011. We also analyze the contribution of this ring to the storm dynamics. In particular, it is shown that the distribution of plasma pressure at ∼7-10RE is nearly azimuthally symmetric. However, the daytime compression of the magnetic field lines and the shift of the minimal value of the magnetic field to higher latitudes lead to the spreading of the transverse current along field lines and splitting of the daytime integral transverse current into two branches in Z direction. The CRC is the high latitude continuation of the ordinary ring current (RC), generated by plasma pressure gradients, directed to the Earth. We evaluated the contribution of the azimuthally symmetric part of the plasma ring to the Dst index for strong geomagnetic storms using the AMPTE/CCE radial profiles of plasma pressure published before, and showed that the contribution of the ring current including both RC and CRC is sufficient to obtain the observed Dst variation without the necessity to include the tail current system.

  19. Novel aspects of plasma control in ITER

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Humphreys, D.; Jackson, G.; Walker, M.

    2015-02-15

    ITER plasma control design solutions and performance requirements are strongly driven by its nuclear mission, aggressive commissioning constraints, and limited number of operational discharges. In addition, high plasma energy content, heat fluxes, neutron fluxes, and very long pulse operation place novel demands on control performance in many areas ranging from plasma boundary and divertor regulation to plasma kinetics and stability control. Both commissioning and experimental operations schedules provide limited time for tuning of control algorithms relative to operating devices. Although many aspects of the control solutions required by ITER have been well-demonstrated in present devices and even designed satisfactorily formore » ITER application, many elements unique to ITER including various crucial integration issues are presently under development. We describe selected novel aspects of plasma control in ITER, identifying unique parts of the control problem and highlighting some key areas of research remaining. Novel control areas described include control physics understanding (e.g., current profile regulation, tearing mode (TM) suppression), control mathematics (e.g., algorithmic and simulation approaches to high confidence robust performance), and integration solutions (e.g., methods for management of highly subscribed control resources). We identify unique aspects of the ITER TM suppression scheme, which will pulse gyrotrons to drive current within a magnetic island, and turn the drive off following suppression in order to minimize use of auxiliary power and maximize fusion gain. The potential role of active current profile control and approaches to design in ITER are discussed. Issues and approaches to fault handling algorithms are described, along with novel aspects of actuator sharing in ITER.« less

  20. Novel aspects of plasma control in ITER

    DOE PAGES

    Humphreys, David; Ambrosino, G.; de Vries, Peter; ...

    2015-02-12

    ITER plasma control design solutions and performance requirements are strongly driven by its nuclear mission, aggressive commissioning constraints, and limited number of operational discharges. In addition, high plasma energy content, heat fluxes, neutron fluxes, and very long pulse operation place novel demands on control performance in many areas ranging from plasma boundary and divertor regulation to plasma kinetics and stability control. Both commissioning and experimental operations schedules provide limited time for tuning of control algorithms relative to operating devices. Although many aspects of the control solutions required by ITER have been well-demonstrated in present devices and even designed satisfactorily formore » ITER application, many elements unique to ITER including various crucial integration issues are presently under development. We describe selected novel aspects of plasma control in ITER, identifying unique parts of the control problem and highlighting some key areas of research remaining. Novel control areas described include control physics understanding (e.g. current profile regulation, tearing mode suppression (TM)), control mathematics (e.g. algorithmic and simulation approaches to high confidence robust performance), and integration solutions (e.g. methods for management of highly-subscribed control resources). We identify unique aspects of the ITER TM suppression scheme, which will pulse gyrotrons to drive current within a magnetic island, and turn the drive off following suppression in order to minimize use of auxiliary power and maximize fusion gain. The potential role of active current profile control and approaches to design in ITER are discussed. Finally, issues and approaches to fault handling algorithms are described, along with novel aspects of actuator sharing in ITER.« less

  1. Impact of the Hall effect on high-energy-density plasma jets.

    PubMed

    Gourdain, P-A; Seyler, C E

    2013-01-04

    Using a 1-MA, 100 ns-rise-time pulsed power generator, radial foil configurations can produce strongly collimated plasma jets. The resulting jets have electron densities on the order of 10(20) cm(-3), temperatures above 50 eV and plasma velocities on the order of 100 km/s, giving Reynolds numbers of the order of 10(3), magnetic Reynolds and Péclet numbers on the order of 1. While Hall physics does not dominate jet dynamics due to the large particle density and flow inside, it strongly impacts flows in the jet periphery where plasma density is low. As a result, Hall physics affects indirectly the geometrical shape of the jet and its density profile. The comparison between experiments and numerical simulations demonstrates that the Hall term enhances the jet density when the plasma current flows away from the jet compared to the case where the plasma current flows towards it.

  2. Advanced ST plasma scenario simulations for NSTX

    NASA Astrophysics Data System (ADS)

    Kessel, C. E.; Synakowski, E. J.; Bell, M. E.; Gates, D. A.; Harvey, R. W.; Kaye, S. M.; Mau, T. K.; Menard, J.; Phillips, C. K.; Taylor, G.; Wilson, R.; NSTX Research Team

    2005-08-01

    Integrated scenario simulations are done for NSTX that address four primary objectives for developing advanced spherical torus (ST) configurations: high β and high βN inductive discharges to study all aspects of ST physics in the high β regime; non-inductively sustained discharges for flattop times greater than the skin time to study the various current drive techniques; non-inductively sustained discharges at high β for flattop times much greater than a skin time which provides the integrated advanced ST target for NSTX and non-solenoidal startup and plasma current rampup. The simulations done here use the tokamak simulation code and are based on a discharge 109070. TRANSP analysis of the discharge provided the thermal diffusivities for electrons and ions, the neutral beam deposition profile and other characteristics. CURRAY is used to calculate the high harmonic fast wave (HHFW) heating depositions and current drive. GENRAY/CQL3D is used to establish the heating and CD deposition profiles for electron Bernstein waves (EBW). Analysis of the ideal MHD stability is done with JSOLVER, BALMSC and PEST2. The simulations indicate that the integrated advanced ST plasma is reachable, obtaining stable plasmas with βT ap 40% at βN's of 7.7-9, IP = 1.0 MA and BT = 0.35 T. The plasma is 100% non-inductive and has a flattop of four skin times. The resulting global energy confinement corresponds to a multiplier of H98(y),2 = 1.5. The simulations have demonstrated the importance of HHFW heating and CD, EBW off-axis CD, strong plasma shaping, density control and early heating/H-mode transition for producing and optimizing these plasma configurations.

  3. A contoured gap coaxial plasma gun with injected plasma armature.

    PubMed

    Witherspoon, F Douglas; Case, Andrew; Messer, Sarah J; Bomgardner, Richard; Phillips, Michael W; Brockington, Samuel; Elton, Raymond

    2009-08-01

    A new coaxial plasma gun is described. The long term objective is to accelerate 100-200 microg of plasma with density above 10(17) cm(-3) to greater than 200 km/s with a Mach number above 10. Such high velocity dense plasma jets have a number of potential fusion applications, including plasma refueling, magnetized target fusion, injection of angular momentum into centrifugally confined mirrors, high energy density plasmas, and others. The approach uses symmetric injection of high density plasma into a coaxial electromagnetic accelerator having an annular gap geometry tailored to prevent formation of the blow-by instability. The injected plasma is generated by numerous (currently 32) radially oriented capillary discharges arranged uniformly around the circumference of the angled annular injection region of the accelerator. Magnetohydrodynamic modeling identified electrode profiles that can achieve the desired plasma jet parameters. The experimental hardware is described along with initial experimental results in which approximately 200 microg has been accelerated to 100 km/s in a half-scale prototype gun. Initial observations of 64 merging injector jets in a planar cylindrical testing array are presented. Density and velocity are presently limited by available peak current and injection sources. Steps to increase both the drive current and the injected plasma mass are described for next generation experiments.

  4. Quasi-steady-state high confinement at high density by lower hybrid waves in the HT-6M tokamak

    NASA Astrophysics Data System (ADS)

    Li, Jiangang; Luo, Jiarong; Wan, Baonian; Wan, Yuanxi; Liu, Yuexiu; Yin, Finxian; Gong, Xianzu; Li, Duochuan; Liu, Shen; Jie, Yinxian; Gao, Xiang; Luo, Nancang; Jiang, Jiaguang; Han, Yuqing; Wu, Mingjun; Wang, Guangxin; Liang, Yunfeng; Yao, Ailing; Wu, Zhenwei; Zhang, Shouyin; Mao, Jiansan; Cui, Lingzhuo; Xu, Yuhong; Meng, Yuedong; Zhao, Junyu; Ding, Bolong; Li, Guiming; Xu, Xiangdong; Lin, Bili; Wei, Meishen; Yie, Weiwei

    2000-03-01

    The quasi-steady-state (tH > 10 τEoh) H mode with high plasma density (ELMy and ELM free) was routinely obtained by the injection of lower hybrid wave heating and lower hybrid current drive with a power threshold of 50 kW. The antenna spectrum was scanned over a wide range and τE was about 1.5-2.0 times that of the L mode scaling. The density increases by almost a factor of 3 during the H phase by gas puffing and the particle confinement time increases by more than this factor even with a line averaged density of 3 × 1013cm-3, which is about 60% of the Greenwald density limit. A hollow Te profile was achieved in the high density case. The experimental results reproducibly show a good agreement with the theoretical prediction for the LH off-axis power deposition profile. When a certain fraction of the plasma current is non-inductively sustained by the LH waves, a hollow current density profile is formed and the magnetic shear is reversed. This off-axis hollow profile and enhanced confinement improvement are attributed to a strong reduction of the electron thermal diffusivity in the reversed shear region.

  5. Control of linear modes in cylindrical resistive magnetohydrodynamics with a resistive wall, plasma rotation, and complex gain

    NASA Astrophysics Data System (ADS)

    Brennan, D. P.; Finn, J. M.

    2014-10-01

    Feedback stabilization of magnetohydrodynamic (MHD) modes in a tokamak is studied in a cylindrical model with a resistive wall, plasma resistivity, viscosity, and toroidal rotation. The control is based on a linear combination of the normal and tangential components of the magnetic field just inside the resistive wall. The feedback includes complex gain, for both the normal and for the tangential components, and it is known that the imaginary part of the feedback for the former is equivalent to plasma rotation [J. M. Finn and L. Chacon, Phys. Plasmas 11, 1866 (2004)]. The work includes (1) analysis with a reduced resistive MHD model for a tokamak with finite β and with stepfunction current density and pressure profiles, and (2) computations with a full compressible visco-resistive MHD model with smooth decreasing profiles of current density and pressure. The equilibria are stable for β = 0 and the marginal stability values βrp,rw < βrp,iw < βip,rw < βip,iw (resistive plasma, resistive wall; resistive plasma, ideal wall; ideal plasma, resistive wall; and ideal plasma, ideal wall) are computed for both models. The main results are: (a) imaginary gain with normal sensors or plasma rotation stabilizes below βrp,iw because rotation suppresses the diffusion of flux from the plasma out through the wall and, more surprisingly, (b) rotation or imaginary gain with normal sensors destabilizes above βrp,iw because it prevents the feedback flux from entering the plasma through the resistive wall to form a virtual wall. A method of using complex gain Gi to optimize in the presence of rotation in this regime with β > βrp,iw is presented. The effect of imaginary gain with tangential sensors is more complicated but essentially destabilizes above and below βrp,iw.

  6. Simulation of current-filament dynamics and relaxation in the Pegasus Spherical Tokamak

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    O'Bryan, J. B.; Sovinec, C. R.; Bird, T. M.

    Nonlinear numerical computation is used to investigate the relaxation of non-axisymmetric current-channels from washer-gun plasma sources into 'tokamak-like' plasmas in the Pegasus toroidal experiment [Eidietis et al. J. Fusion Energy 26, 43 (2007)]. Resistive MHD simulations with the NIMROD code [Sovinec et al. Phys. Plasmas 10(5), 1727-1732 (2003)] utilize ohmic heating, temperature-dependent resistivity, and anisotropic, temperature-dependent thermal conduction corrected for regions of low magnetization to reproduce critical transport effects. Adjacent passes of the simulated current-channel attract and generate strong reversed current sheets that suggest magnetic reconnection. With sufficient injected current, adjacent passes merge periodically, releasing axisymmetric current rings from themore » driven channel. The current rings have not been previously observed in helicity injection for spherical tokamaks, and as such, provide a new phenomenological understanding for filament relaxation in Pegasus. After large-scale poloidal-field reversal, a hollow current profile and significant poloidal flux amplification accumulate over many reconnection cycles.« less

  7. The Use of a 28 GHz Gyrotron for EBW Startup Experiments on MAST

    NASA Astrophysics Data System (ADS)

    Caughman, J. B.; Bigelow, T. S.; Diem, S. J.; Peng, Y. K. M.; Rasmussen, D. A.; Shevchenko, V.; Hawes, J.; Lloyd, B.

    2009-11-01

    The use of electron Bernstein waves for non-inductive plasma current startup in MAST has recently been demonstrated [1]. The injection of 100 kW at 28 GHz generated plasma currents of up to 33 kA without the use of solenoid flux, and limited solenoid assist resulted in up to 55 kA of plasma current. A higher power 28 GHz gyrotron, with power levels of up to 300 kW for 0.5 seconds, is currently being commissioned. It is being used to investigate the scaling of startup current with microwave power and power profile as a function of time. Power modulation experiments are also being explored. Gyrotron performance and experimental results will be presented. [4pt] [1] V. Shevchenko, et al., Proceedings of the 15^th Joint Workshop on ECE and ECRH, Yosimite, USA, p. 68 (2009)

  8. Characterization of the concurrent metabolic changes in brain and plasma during insulin-induced moderate hypoglycemia using 1H NMR spectroscopy in juvenile rats.

    PubMed

    Ennis, Kathleen; Lusczek, Elizabeth; Rao, Raghavendra

    2017-07-13

    Treatment of hypoglycemia in children is currently based on plasma glucose measurements. This approach may not ensure neuroprotection since plasma glucose does not reflect the dynamic state of cerebral energy metabolism. To determine whether cerebral metabolic changes during hypoglycemia could be better characterized using plasma metabolomic analysis, insulin-induced acute hypoglycemia was induced in 4-week-old rats. Brain tissue and concurrent plasma samples were collected from hypoglycemic (N=7) and control (N=7) rats after focused microwave fixation to prevent post-mortem metabolic changes. The concentration of 29 metabolites in brain and 34 metabolites in plasma were determined using 1 H NMR spectroscopy at 700MHz and examined using partial least squares-discriminant analysis. The sensitivity of plasma glucose for detecting cerebral energy failure was assessed by determining its relationship to brain phosphocreatine. The brain and plasma metabolite profiles of the hypoglycemia group were distinct from the control group (brain: R 2 =0.92, Q 2 =0.31; plasma: R 2 =0.95, Q 2 =0.74). Concentration differences in glucose, ketone bodies and amino acids were responsible for the intergroup separation. There was 45% concordance between the brain and plasma metabolite profiles. Brain phosphocreatine correlated with brain glucose (control group: R 2 =0.86; hypoglycemia group: R 2 =0.59; p<0.05), but not with plasma glucose. The results confirm that plasma glucose is an insensitive biomarker of cerebral energy changes during hypoglycemia and suggest that a plasma metabolite profile is superior for monitoring cerebral metabolism. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Bootstrap current control studies in the Wendelstein 7-X stellarator using the free-plasma-boundary version of the SIESTA MHD equilibrium code

    NASA Astrophysics Data System (ADS)

    Peraza-Rodriguez, H.; Reynolds-Barredo, J. M.; Sanchez, R.; Tribaldos, V.; Geiger, J.

    2018-02-01

    The recently developed free-plasma-boundary version of the SIESTA MHD equilibrium code (Hirshman et al 2011 Phys. Plasmas 18 062504; Peraza-Rodriguez et al 2017 Phys. Plasmas 24 082516) is used for the first time to study scenarios with considerable bootstrap currents for the Wendelstein 7-X (W7-X) stellarator. Bootstrap currents in the range of tens of kAs can lead to the formation of unwanted magnetic island chains or stochastic regions within the plasma and alter the boundary rotational transform due to the small shear in W7-X. The latter issue is of relevance since the island divertor operation of W7-X relies on a proper positioning of magnetic island chains at the plasma edge to control the particle and energy exhaust towards the divertor plates. Two scenarios are examined with the new free-plasma-boundary capabilities of SIESTA: a freely evolving bootstrap current one that illustrates the difficulties arising from the dislocation of the boundary islands, and a second one in which off-axis electron cyclotron current drive (ECCD) is applied to compensate the effects of the bootstrap current and keep the island divertor configuration intact. SIESTA finds that off-axis ECCD is indeed able to keep the location and phase of the edge magnetic island chain unchanged, but it may also lead to an undesired stochastization of parts of the confined plasma if the EC deposition radial profile becomes too narrow.

  10. The Role of Plasma Rotation in C-Mod Internal Transport Barriers

    NASA Astrophysics Data System (ADS)

    Fiore, C. L.; Ernst, D. R.; Rice, J. E.; Podpaly, Y.; Reinke, M. L.; Greenwald, M. J.; Hughes, J. W.; Ma, Y.; Bespamyatnov, I. O.; Rowan, W. L.

    2010-11-01

    ITBs in Alcator C-Mod featuring highly peaked density and pressure profiles are induced by injecting ICRF power with the second harmonic of the resonant frequency for minority hydrogen off-axis at the plasma half radius. These ITBs are formed in the absence of particle or momentum injection, and with monotonic q profiles with qmin < 1. In C-Mod a strong co-current toroidal rotation, peaked on axis, develops after the transition to H-mode. If an ITB forms, this rotation decreases in the center of the plasma and forms a well, and often reverses direction in the core. This indicates that there is a strong EXB shearing rate in the region where the foot in the ITB density profile is observed. Preliminary gyrokinetic analyses indicate that this shearing rate is comparable to the ion temperature gradient mode (ITG) growth rate at this location and may be responsible for stabilizing the turbulence. Gyrokinetic analyses of recent experimental data obtained from a complete scan of the ICRF resonance position across the entire C-Mod plasma will be presented.

  11. Recommendations for Improving Identification and Quantification in Non-Targeted, GC-MS-Based Metabolomic Profiling of Human Plasma

    PubMed Central

    Wang, Hanghang; Muehlbauer, Michael J.; O’Neal, Sara K.; Newgard, Christopher B.; Hauser, Elizabeth R.; Shah, Svati H.

    2017-01-01

    The field of metabolomics as applied to human disease and health is rapidly expanding. In recent efforts of metabolomics research, greater emphasis has been placed on quality control and method validation. In this study, we report an experience with quality control and a practical application of method validation. Specifically, we sought to identify and modify steps in gas chromatography-mass spectrometry (GC-MS)-based, non-targeted metabolomic profiling of human plasma that could influence metabolite identification and quantification. Our experimental design included two studies: (1) a limiting-dilution study, which investigated the effects of dilution on analyte identification and quantification; and (2) a concentration-specific study, which compared the optimal plasma extract volume established in the first study with the volume used in the current institutional protocol. We confirmed that contaminants, concentration, repeatability and intermediate precision are major factors influencing metabolite identification and quantification. In addition, we established methods for improved metabolite identification and quantification, which were summarized to provide recommendations for experimental design of GC-MS-based non-targeted profiling of human plasma. PMID:28841195

  12. Non-inductively driven tokamak plasmas at near-unity β t in the Pegasus toroidal experiment

    DOE PAGES

    Reusch, Joshua A.; Bodner, Grant M.; Bongard, Michael W.; ...

    2018-03-14

    Amore » major goal of the spherical tokamak (ST) research program is accessing a state of low internal inductance ℓ i , high elongation κ , and high toroidal and normalized beta ( β t and β N ) without solenoidal current drive. Local helicity injection (LHI) in the Pegasus ST [Garstka et al., Nucl. Fusion 46, S603 (2006)] provides non-solenoidally driven plasmas that exhibit these characteristics. LHI utilizes compact, edge-localized current sources for plasma startup and sustainment. It results in hollow current density profiles with low ℓ i . The low aspect ratio ( R 0 / a ~ 1.2 ) of Pegasus allows access to high κ and high normalized plasma currents I N = I p / a B T > 14 ). Magnetic reconnection during LHI provides auxiliary ion heating. Together, these features provide access to very high β t plasmas. Equilibrium analyses indicate that β t up to ~100% is achieved. Finally, these high β t discharges disrupt at the ideal no-wall β limit at β N ~ 7. « less

  13. Non-inductively driven tokamak plasmas at near-unity β t in the Pegasus toroidal experiment

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Reusch, Joshua A.; Bodner, Grant M.; Bongard, Michael W.

    Amore » major goal of the spherical tokamak (ST) research program is accessing a state of low internal inductance ℓ i , high elongation κ , and high toroidal and normalized beta ( β t and β N ) without solenoidal current drive. Local helicity injection (LHI) in the Pegasus ST [Garstka et al., Nucl. Fusion 46, S603 (2006)] provides non-solenoidally driven plasmas that exhibit these characteristics. LHI utilizes compact, edge-localized current sources for plasma startup and sustainment. It results in hollow current density profiles with low ℓ i . The low aspect ratio ( R 0 / a ~ 1.2 ) of Pegasus allows access to high κ and high normalized plasma currents I N = I p / a B T > 14 ). Magnetic reconnection during LHI provides auxiliary ion heating. Together, these features provide access to very high β t plasmas. Equilibrium analyses indicate that β t up to ~100% is achieved. Finally, these high β t discharges disrupt at the ideal no-wall β limit at β N ~ 7. « less

  14. Streaming sausage, kink and tearing instabilities in a current sheet with applications to the earth's magnetotail

    NASA Technical Reports Server (NTRS)

    Lee, L. C.; Wang, S.; Wei, C. Q.; Tsurutani, B. T.

    1988-01-01

    This paper investigates the growth rates and eigenmode structures of the streaming sausage, kink, and tearing instabilities in a current sheet with a super-Alfvenic flow. The growth rates and eigenmode structures are first considered in the ideal incompressible limit by using a four-layer model, as well as a more realistic case in which all plasma parameters and the magnetic field vary continuously along the direction perpendicular to the magnetic field and plasma flow. An initial-value method is applied to obtain the growth rate and eigenmode profiles of the fastest growing mode, which is either the sausage mode or kink mode. It is shown that, in the earth's magnetotail, where super-Alfvenic plasma flows are observed in the plasma sheet and the ratio between the plasma and magnetic pressures far away from the current layer is about 0.1-0.3 in the lobes, the streaming sausage and streaming tearing instabilities, but not kink modes, are likely to occur.

  15. Magnetless magnetic fusion

    NASA Astrophysics Data System (ADS)

    Beklemishev, A. D.; Tajima, T.

    1994-02-01

    The authors propose a concept of thermonuclear fusion reactor in which the plasma pressure is balanced by direct gas-wall interaction in a high-pressure vessel. The energy confinement is achieved by means of the self-contained toroidal magnetic configuration sustained by an external current drive or charged fusion products. This field structure causes the plasma pressure to decrease toward the inside of the discharge and thus it should be magnetohydrodynamically stable. The maximum size, temperature and density profiles of the reactor are estimated. An important feature of confinement physics is the thin layer of cold gas at the wall and the adjacent transitional region of dense arc-like plasma. The burning condition is determined by the balance between these nonmagnetized layers and the current-carrying plasma. They suggest several questions for future investigation, such as the thermal stability of the transition layer and the possibility of an effective heating and current drive behind the dense edge plasma. The main advantage of this scheme is the absence of strong external magnets and, consequently, potentially cheaper design and lower energy consumption.

  16. Scaling of confinement and profiles in the EXTRAP T2 reversed-field pinch

    NASA Astrophysics Data System (ADS)

    Welander, A.

    1999-01-01

    In the EXTRAP T2 reversed-field pinch the diagnostic techniques for the measurement of electron density and temperature include; Thomson scattering which gives values at three radial positions in the core (r/a = 0, 0.28, 0.56), Langmuir probes which give values at the edge (r/a > 0.9) and interferometry which gives a line-averaged density. The empirical scaling of electron density and temperature including profile information with global plasma parameters has been studied. The density profile is subject to large variations, with an average parabolic shape when the density is low and flatter shapes when the density is increased. The change in the profile shape can be attributed to a shift in the penetration length of neutrals from the vicinity of the wall. The temperature scales roughly as I/n1/2 where I is the plasma current and n is the density. The temperature profile is always quite flat with lower variations and there is a tendency for a flatter profile at higher temperatures.

  17. Profile modification computations for LHCD experiments on PBX-M using the TSC/LSC model

    NASA Astrophysics Data System (ADS)

    Kaita, R.; Ignat, D. W.; Jardin, S. C.; Okabayashi, M.; Sun, Y. C.

    1996-02-01

    The TSC-LSC computational model of the dynamics of lower hybrid current drive has been exercised extensively in comparison with data from a Princeton Beta Experiment-Modification (PBX-M) discharge where the measured q(0) attained values slightly above unity. Several significant, but plausible, assumptions had to be introduced to keep the computation from behaving pathologically over time, producing singular profiles of plasma current density and q. Addition of a heuristic current diffusion estimate, or more exactly, a smoothing of the rf-driven current with a diffusion-like equation, greatly improved the behavior of the computation, and brought theory and measurement into reasonable agreement. The model was then extended to longer pulse lengths and higher powers to investigate performance to be expected in future PBX-M current profile modification experiments.

  18. DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tierno, S. P., E-mail: sp.tierno@upm.es; Donoso, J. M.; Domenech-Garret, J. L.

    The interaction between an electron emissive wall, electrically biased in a plasma, is revisited through a simple fluid model. We search for realistic conditions of the existence of a non-monotonic plasma potential profile with a virtual cathode as it is observed in several experiments. We mainly focus our attention on thermionic emission related to the operation of emissive probes for plasma diagnostics, although most conclusions also apply to other electron emission processes. An extended Bohm criterion is derived involving the ratio between the two different electron densities at the potential minimum and at the background plasma. The model allows amore » phase-diagram analysis, which confirms the existence of the non-monotonic potential profiles with a virtual cathode. This analysis shows that the formation of the potential well critically depends on the emitted electron current and on the velocity at the sheath edge of cold ions flowing from the bulk plasma. As a consequence, a threshold value of the governing parameter is required, in accordance to the physical nature of the electron emission process. The latter is a threshold wall temperature in the case of thermionic electrons. Experimental evidence supports our numerical calculations of this threshold temperature. Besides this, the potential well becomes deeper with increasing electron emission, retaining a fraction of the released current which limits the extent of the bulk plasma perturbation. This noninvasive property would explain the reliable measurements of plasma potential by using the floating potential method of emissive probes operating in the so-called strong emission regime.« less

  19. Generalization of Solovev’s approach to finding equilibrium solutions for axisymmetric plasmas with flow

    NASA Astrophysics Data System (ADS)

    M, S. CHU; Yemin, HU; Wenfeng, GUO

    2018-03-01

    Solovev’s approach of finding equilibrium solutions was found to be extremely useful for generating a library of linear-superposable equilibria for the purpose of shaping studies. This set of solutions was subsequently expanded to include the vacuum solutions of Zheng, Wootton and Solano, resulting in a set of functions {SOLOVEV_ZWS} that were usually used for all toroidally symmetric plasmas, commonly recognized as being able to accommodate any desired plasma shapes (complete-shaping capability). The possibility of extending the Solovev approach to toroidal equilibria with a general plasma flow is examined theoretically. We found that the only meaningful extension is to plasmas with a pure toroidal rotation and with a constant Mach number. We also show that the simplification ansatz made to the current profiles, which was the basis of the Solovev approach, should be applied more systematically to include an internal boundary condition at the magnetic axis; resulting in a modified and more useful set {SOLOVEV_ZWSm}. Explicit expressions of functions in this set are given for equilibria with a quasi-constant current density profile, with a toroidal flow at a constant Mach number and with specific heat capacity 1. The properties of {SOLOVEV_ZWSm} are studied analytically. Numerical examples of achievable equilibria are demonstrated. Although the shaping capability of the set {SOLOVE_ZWSm} is quite extensive, it nevertheless still does not have complete shaping capability, particularly for plasmas with negative curvature points on the plasma boundary such as the doublets or indented bean shaped tokamaks.

  20. Internal transport barrier triggered by non-linear lower hybrid wave deposition under condition of beam-driven toroidal rotation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gao, Q. D., E-mail: qgao@swip.ac.cn; Budny, R. V.

    2015-03-15

    By using gyro-Landau fluid transport model (GLF23), time-dependent integrated modeling is carried out using TRANSP to explore the dynamic process of internal transport barrier (ITB) formation in the neutral beam heating discharges. When the current profile is controlled by LHCD (lower hybrid current drive), with appropriate neutral beam injection, the nonlinear interplay between the transport determined gradients in the plasma temperature (T{sub i,e}) and toroidal velocity (V{sub ϕ}) and the E×B flow shear (including q-profile) produces transport bifurcations, generating spontaneously a stepwise growing ITB. In the discharge, the constraints imposed by the wave propagation condition causes interplay of the LHmore » driven current distribution with the plasma configuration modification, which constitutes non-linearity in the LH wave deposition. The non-linear effects cause bifurcation in LHCD, generating two distinct quasi-stationary reversed magnetic shear configurations. The change of current profile during the transition period between the two quasi-stationary states results in increase of the E×B shearing flow arising from toroidal rotation. The turbulence transport suppression by sheared E×B flow during the ITB development is analysed, and the temporal evolution of some parameters characterized the plasma confinement is examined. Ample evidence shows that onset of the ITB development is correlated with the enhancement of E×B shearing rate caused by the bifurcation in LHCD. It is suggested that the ITB triggering is associated with the non-linear effects of the LH power deposition.« less

  1. Effects of magnetic islands on bootstrap current in toroidal plasmas

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dong, G.; Lin, Z.

    The effects of magnetic islands on electron bootstrap current in toroidal plasmas are studied using gyrokinetic simulations. The magnetic islands cause little changes of the bootstrap current level in the banana regime because of trapped electron effects. In the plateau regime, the bootstrap current is completely suppressed at the island centers due to the destruction of trapped electron orbits by collisions and the flattening of pressure profiles by the islands. In the collisional regime, small but finite bootstrap current can exist inside the islands because of the pressure gradients created by large collisional transport across the islands. Lastly, simulation resultsmore » show that the bootstrap current level increases near the island separatrix due to steeper local density gradients.« less

  2. Effects of magnetic islands on bootstrap current in toroidal plasmas

    DOE PAGES

    Dong, G.; Lin, Z.

    2016-12-19

    The effects of magnetic islands on electron bootstrap current in toroidal plasmas are studied using gyrokinetic simulations. The magnetic islands cause little changes of the bootstrap current level in the banana regime because of trapped electron effects. In the plateau regime, the bootstrap current is completely suppressed at the island centers due to the destruction of trapped electron orbits by collisions and the flattening of pressure profiles by the islands. In the collisional regime, small but finite bootstrap current can exist inside the islands because of the pressure gradients created by large collisional transport across the islands. Lastly, simulation resultsmore » show that the bootstrap current level increases near the island separatrix due to steeper local density gradients.« less

  3. Non-targeted plasma metabolomic profile at early and late lactation in parity 1 dams with diverging body composition at weaning

    USDA-ARS?s Scientific Manuscript database

    Lactation is an extremely energy demanding event, impacting naïve dams to a greater extent as they are still physiologically immature. The objective of the current study was to determine if a unique plasma metabolome exists at early and late lactation from first parity gilts having similar body meas...

  4. Exploration of high harmonic fast wave heating on the National Spherical Torus Experiment

    NASA Astrophysics Data System (ADS)

    Wilson, J. R.; Bell, R. E.; Bernabei, S.; Bitter, M.; Bonoli, P.; Gates, D.; Hosea, J.; LeBlanc, B.; Mau, T. K.; Medley, S.; Menard, J.; Mueller, D.; Ono, M.; Phillips, C. K.; Pinsker, R. I.; Raman, R.; Rosenberg, A.; Ryan, P.; Sabbagh, S.; Stutman, D.; Swain, D.; Takase, Y.; Wilgen, J.

    2003-05-01

    High harmonic fast wave (HHFW) heating has been proposed as a particularly attractive means for plasma heating and current drive in the high beta plasmas that are achievable in spherical torus (ST) devices. The National Spherical Torus Experiment (NSTX) [M. Ono, S. M. Kaye, S. Neumeyer et al., in Proceedings of the 18th IEEE/NPSS Symposium on Fusion Engineering, Albuquerque, 1999 (IEEE, Piscataway, NJ, 1999), p. 53] is such a device. An rf heating system has been installed on the NSTX to explore the physics of HHFW heating, current drive via rf waves and for use as a tool to demonstrate the attractiveness of the ST concept as a fusion device. To date, experiments have demonstrated many of the theoretical predictions for HHFW. In particular, strong wave absorption on electrons over a wide range of plasma parameters and wave parallel phase velocities, wave acceleration of energetic ions, and indications of current drive for directed wave spectra have been observed. In addition HHFW heating has been used to explore the energy transport properties of NSTX plasmas, to create H-mode discharges with a large fraction of bootstrap current and to control the plasma current profile during the early stages of the discharge.

  5. Overview of ASDEX Upgrade results

    DOE PAGES

    Aguiam, D.

    2017-06-28

    Here, the ASDEX Upgrade (AUG) programme is directed towards physics input to critical elements of the ITER design and the preparation of ITER operation, as well as addressing physics issues for a future DEMO design. Since 2015, AUG is equipped with a new pair of 3-strap ICRF antennas, which were designed for a reduction of tungsten release during ICRF operation. As predicted, a factor two reduction on the ICRF-induced W plasma content could be achieved by the reduction of the sheath voltage at the antenna limiters via the compensation of the image currents of the central and side straps in the antenna frame. There are two main operational scenario lines in AUG. Experiments with low collisionality, which comprise current drive, ELM mitigation/suppression and fast ion physics, are mainly done with freshly boronized walls to reduce the tungsten influx at these high edge temperature conditions. Full ELM suppression and non-inductive operation up to a plasma current ofmore » $${{I}_{\\text{p}}}=0.8$$ MA could be obtained at low plasma density. Plasma exhaust is studied under conditions of high neutral divertor pressure and separatrix electron density, where a fresh boronization is not required. Substantial progress could be achieved for the understanding of the confinement degradation by strong D puffing and the improvement with nitrogen or carbon seeding. Inward/outward shifts of the electron density profile relative to the temperature profile effect the edge stability via the pressure profile changes and lead to improved/decreased pedestal performance. Seeding and D gas puffing are found to effect the core fueling via changes in a region of high density on the high field side (HFSHD).« less

  6. Characterization of Flow and Ohm's Law in the Rotating Wall Machine

    NASA Astrophysics Data System (ADS)

    Hannum, David; Brookhart, M.; Forest, C. B.; Kendrick, R.; Mengin, G.; Paz-Soldan, C.

    2010-11-01

    The rotating wall machine is a linear screw-pinch built to study the role of different electromagnetic boundary conditions on the Resistive Wall Mode (RWM). Its plasma is created by an array of electrostatic washer guns which can be biased to discharge up to 1 kA of current each. Individual flux ropes from the guns shear, merge, and expand into a 20 cm diameter, ˜1 m long plasma column. Langmuir (singletip) and tri-axial B-dot probes move throughout the column to measure radial and axial profiles of key plasma parameters. As the plasma current increases, more H2 fuel is ionized, raising ne to 5 x10^20 m-3 while Te stays at a constant 3 eV. The electron density expands to the wall while the current density (Jz) stays pinched to the central axis. E xB and diamagnetic drifts create radially and axially sheared plasma rotation. Plasma resistivity follows the Spitzer model in the core while exceeding it at the edge. These measurements improve the model used to predict the RWM growth rate.

  7. Suppressing magnetic island growth by resonant magnetic perturbation

    NASA Astrophysics Data System (ADS)

    Yu, Q.; Günter, S.; Lackner, K.

    2018-05-01

    The effect of externally applied resonant magnetic perturbations (RMPs) on the growth of magnetic islands is investigated based on two-fluid equations. It is found that if the local bi-normal electron fluid velocity at the resonant surface is sufficiently large, static RMPs of the same helicity and of moderate amplitude can suppress the growth of magnetic islands in high-temperature plasmas. These islands will otherwise grow, driven by an unfavorable plasma current density profile and bootstrap current perturbation. These results indicate that the error field can stabilize island growth, if the error field amplitude is not too large and the local bi-normal electron fluid velocity is not too low. They also indicate that applied rotating RMPs with an appropriate frequency can be utilized to suppress island growth in high-temperature plasmas, even for a low bi-normal electron fluid velocity. A significant change in the local equilibrium plasma current density gradient by small amplitude RMPs is found for realistic plasma parameters, which are important for the island stability and are expected to be more important for fusion reactors with low plasma resistivity.

  8. Non-inductive current drive and transport in high βN plasmas in JET

    NASA Astrophysics Data System (ADS)

    Voitsekhovitch, I.; Alper, B.; Brix, M.; Budny, R. V.; Buratti, P.; Challis, C. D.; Ferron, J.; Giroud, C.; Joffrin, E.; Laborde, L.; Luce, T. C.; McCune, D.; Menard, J.; Murakami, M.; Park, J. M.; JET-EFDA contributors

    2009-05-01

    A route to stationary MHD stable operation at high βN has been explored at the Joint European Torus (JET) by optimizing the current ramp-up, heating start time and the waveform of neutral beam injection (NBI) power. In these scenarios the current ramp-up has been accompanied by plasma pre-heat (or the NBI has been started before the current flat-top) and NBI power up to 22 MW has been applied during the current flat-top. In the discharges considered transient total βN ≈ 3.3 and stationary (during high power phase) βN ≈ 3 have been achieved by applying the feedback control of βN with the NBI power in configurations with monotonic or flat core safety factor profile and without an internal transport barrier (ITB). The transport and current drive in this scenario is analysed here by using the TRANSP and ASTRA codes. The interpretative analysis performed with TRANSP shows that 50-70% of current is driven non-inductively; half of this current is due to the bootstrap current which has a broad profile since an ITB was deliberately avoided. The GLF23 transport model predicts the temperature profiles within a ±22% discrepancy with the measurements over the explored parameter space. Predictive simulations with this model show that the E × B rotational shear plays an important role for thermal ion transport in this scenario, producing up to a 40% increase of the ion temperature. By applying transport and current drive models validated in self-consistent simulations of given reference scenarios in a wider parameter space, the requirements for fully non-inductive stationary operation at JET are estimated. It is shown that the strong stiffness of the temperature profiles predicted by the GLF23 model restricts the bootstrap current at larger heating power. In this situation full non-inductive operation without an ITB can be rather expensive strongly relying on the external non-inductive current drive sources.

  9. Kink modes and surface currents associated with vertical displacement events

    NASA Astrophysics Data System (ADS)

    Manickam, Janardhan; Boozer, Allen; Gerhardt, Stefan

    2012-08-01

    The fast termination phase of a vertical displacement event (VDE) in a tokamak is modeled as a sequence of shrinking equilibria, where the core current profile remains constant so that the safety-factor at the axis, qaxis, remains fixed and the qedge systematically decreases. At some point, the n = 1 kink mode is destabilized. Kink modes distort the magnetic field lines outside the plasma, and surface currents are required to nullify the normal component of the B-field at the plasma boundary and maintain equilibrium at finite pressure. If the plasma touches a conductor, the current can be transferred to the conductor, and may be measurable by the halo current monitors. This report describes a practical method to model the plasma as it evolves during a VDE, and determine the surface currents, needed to maintain equilibrium. The main results are that the onset conditions for the disruption are that the growth-rate of the n = 1 kink exceeds half the Alfven time and the associated surface current needed to maintain equilibrium exceeds one half of the core plasma current. This occurs when qedge drops below a low integer, usually 2. Application to NSTX provides favorable comparison with non-axisymmetric halo-current measurements. The model is also applied to ITER and shows that the 2/1 mode is projected to be the most likely cause of the final disruption.

  10. Preface to Special Topic: Advances in Radio Frequency Physics in Fusion Plasmas

    NASA Astrophysics Data System (ADS)

    Tuccillo, Angelo A.; Phillips, Cynthia K.; Ceccuzzi, Silvio

    2014-06-01

    It has long been recognized that auxiliary plasma heating will be required to achieve the high temperature, high density conditions within a magnetically confined plasma in which a fusion "burn" may be sustained by copious fusion reactions. Consequently, the application of radio and microwave frequency electromagnetic waves to magnetically confined plasma, commonly referred to as RF, has been a major part of the program almost since its inception in the 1950s. These RF waves provide heating, current drive, plasma profile control, and Magnetohydrodynamics (MHD) stabilization. Fusion experiments employ electromagnetic radiation in a wide range of frequencies, from tens of MHz to hundreds of GHz. The fusion devices containing the plasma are typically tori, axisymmetric or non, in which the equilibrium magnetic fields are composed of a strong toroidal magnetic field generated by external coils, and a poloidal field created, at least in the symmetric configurations, by currents flowing in the plasma. The waves are excited in the peripheral regions of the plasma, by specially designed launching structures, and subsequently propagate into the core regions, where resonant wave-plasma interactions produce localized heating or other modification of the local equilibrium profiles. Experimental studies coupled with the development of theoretical models and advanced simulation codes over the past 40+ years have led to an unprecedented understanding of the physics of RF heating and current drive in the core of magnetic fusion devices. Nevertheless, there are serious gaps in our knowledge base that continue to have a negative impact on the success of ongoing experiments and that must be resolved as the program progresses to the next generation devices and ultimately to "demo" and "fusion power plant." A serious gap, at least in the ion cyclotron (IC) range of frequencies and partially in the lower hybrid frequency ranges, is the difficulty in coupling large amount of power to the plasma while minimizing the interaction between the plasma and launching structures. These potentially harmful interactions between the plasma and the vessel and launching structures are challenging: (i) significant and variable loss of power in the edge regions of confined plasmas and surrounding vessel structures adversely affect the core plasma performance and lifetime of a device; (ii) the launcher design is partly "trial and error," with the consequence that launchers may have to be reconfigured after initial tests in a given device, at an additional cost. Over the broader frequency range, another serious gap is a quantitative lack of understanding of the combined effects of nonlinear wave-plasma processes, energetic particle interactions and non-axisymmetric equilibrium effects on determining the overall efficiency of plasma equilibrium and stability profile control techniques using RF waves. This is complicated by a corresponding lack of predictive understanding of the time evolution of transport and stability processes in fusion plasmas.

  11. Sawtooth oscillations in shaped plasmas

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lazarus, E. A.; Luce, T. C.; Burrell, K. H.

    The role of interchange and internal kink modes in the sawtooth oscillations is explored by comparing bean- and oval-shaped plasmas. The n=1 instability that results in the collapse of the sawtooth has been identified as a quasi-interchange in the oval cases and the internal kink in the bean shape. The ion and electron temperature profiles are followed in detail through the sawtooth ramp. It is found that electron energy transport rates are very high in the oval and quite low in the bean shape. Ion energy confinement in the oval is excellent and the sawtooth amplitude ({delta}T/T) in the ionmore » temperature is much larger than that of the electrons. The sawtooth amplitudes for ions and electrons are comparable in the bean shape. The measured q profiles in the bean and oval shapes are found to be consistent with neoclassical current diffusion of the toroidal current, and the observed differences in q largely result from the severe differences in electron energy transport. For both shapes the collapse flattens the q profile and after the collapse return to q{sub 0} > or approx. 1. Recent results on intermediate shapes are reported. These shapes show that the electron energy transport improves gradually as the plasma triangularity is increased.« less

  12. Plasma response to sustainment with imposed-dynamo current drive in HIT-SI and HIT-SI3

    NASA Astrophysics Data System (ADS)

    Hossack, A. C.; Jarboe, T. R.; Chandra, R. N.; Morgan, K. D.; Sutherland, D. A.; Penna, J. M.; Everson, C. J.; Nelson, B. A.

    2017-07-01

    The helicity injected torus—steady inductive (HIT-SI) program studies efficient, steady-state current drive for magnetic confinement plasmas using a novel experimental method. Stable, high-beta spheromaks have been sustained using steady, inductive current drive. Externally induced loop voltage and magnetic flux are oscillated together so that helicity and power injection are always positive, sustaining the edge plasma current indefinitely. Imposed-dynamo current drive (IDCD) theory further shows that the entire plasma current is sustained. The method is ideal for low aspect ratio, toroidal geometries with closed flux surfaces. Experimental studies of spheromak plasmas sustained with IDCD have shown stable magnetic profiles with evidence of pressure confinement. New measurements show coherent motion of a stable spheromak in response to the imposed perturbations. On the original device two helicity injectors were mounted on either side of the spheromak and the injected mode spectrum was predominantly n  =  1. Coherent, rigid motion indicates that the spheromak is stable and a lack of plasma-generated n  =  1 energy indicates that the maximum q is maintained below 1 during sustainment. Results from the HIT-SI3 device are also presented. Three inductive helicity injectors are mounted on one side of the spheromak flux conserver. Varying the relative injector phasing changes the injected mode spectrum which includes n  =  2, 3, and higher modes.

  13. Experimental investigation of plasma sheaths in magnetic mirror and cusp configurations

    NASA Astrophysics Data System (ADS)

    Jiang, Zhengqi; Wei, Zi-an; Ma, J. X.

    2017-11-01

    Sheath structures near a metal plate in a magnetized plasma were experimentally investigated in magnetic mirror and cusp configurations. Plasma parameters and the sheath potential distributions were probed by a planar and an emissive probe, respectively. The measured sheath profiles in the mirror configuration show that the sheath thickness first decreases and then increases when the magnetic strength is raised. A magnetic flux-tube model was used to explain this result. In the cusp configuration, the measured sheath thickness decreases with the increase of the coil current creating the magnetic cusp. However, when normalized by the electron Debye length, the dependence of the sheath thickness on the coil current is reversed.

  14. Investigation of MHD instabilities and control in KSTAR preparing for high beta operation

    NASA Astrophysics Data System (ADS)

    Park, Y. S.; Sabbagh, S. A.; Bialek, J. M.; Berkery, J. W.; Lee, S. G.; Ko, W. H.; Bak, J. G.; Jeon, Y. M.; Park, J. K.; Kim, J.; Hahn, S. H.; Ahn, J.-W.; Yoon, S. W.; Lee, K. D.; Choi, M. J.; Yun, G. S.; Park, H. K.; You, K.-I.; Bae, Y. S.; Oh, Y. K.; Kim, W.-C.; Kwak, J. G.

    2013-08-01

    Initial H-mode operation of the Korea Superconducting Tokamak Advanced Research (KSTAR) is expanded to higher normalized beta and lower plasma internal inductance moving towards design target operation. As a key supporting device for ITER, an important goal for KSTAR is to produce physics understanding of MHD instabilities at long pulse with steady-state profiles, at high normalized beta, and over a wide range of plasma rotation profiles. An advance from initial plasma operation is a significant increase in plasma stored energy and normalized beta, with Wtot = 340 kJ, βN = 1.9, which is 75% of the level required to reach the computed ideal n = 1 no-wall stability limit. The internal inductance was lowered to 0.9 at sustained H-mode duration up to 5 s. In ohmically heated plasmas, the plasma current reached 1 MA with prolonged pulse length up to 12 s. Rotating MHD modes are observed in the device with perturbations having tearing rather than ideal parity. Modes with m/n = 3/2 are triggered during the H-mode phase but are relatively weak and do not substantially reduce Wtot. In contrast, 2/1 modes to date only appear when the plasma rotation profiles are lowered after H-L back-transition. Subsequent 2/1 mode locking creates a repetitive collapse of βN by more than 50%. Onset behaviour suggests the 3/2 mode is close to being neoclassically unstable. A correlation between the 2/1 mode amplitude and local rotation shear from an x-ray imaging crystal spectrometer suggests that the rotation shear at the mode rational surface is stabilizing. As a method to access the ITER-relevant low plasma rotation regime, plasma rotation alteration by n = 1, 2 applied fields and associated neoclassical toroidal viscosity (NTV) induced torque is presently investigated. The net rotation profile change measured by a charge exchange recombination diagnostic with proper compensation of plasma boundary movement shows initial evidence of non-resonant rotation damping by the n = 1, 2 applied field configurations. The result addresses perspective on access to low rotation regimes for MHD instability studies applicable to ITER. Computation of active RWM control using the VALEN-3D code examines control performance using midplane locked mode detection sensors. The LM sensors are found to be strongly affected by mode and control coil-induced vessel current, and consequently lead to limited control performance theoretically.

  15. Production of Internal Transport Barriers via self-generated flows in Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Fiore, Catherine L.

    2011-10-01

    New results suggest that changes observed in the intrinsic toroidal rotation influence ITB formation in Alcator C-Mod that arise when the resonance for ICRF minority heating is positioned off-axis at or outside of the plasma half-radius. These ITBs form in a reactor relevant regime, without particle or momentum injection, with Ti ~Te, and with monotonic q profiles (qmin < 1). C-Mod H-mode plasmas exhibit strong intrinsic co-current rotation that increases with increasing stored energy without external drive. With the resonance position off-axis, the rotation decreases in the center of the plasma resulting in a radial rotation profile with a central well which deepens and moves farther off-axis when the ICRF resonance is at the plasma half-radius. This profile results in strong ExB shear (>1.5x105 Rad/sec) in the region where the ITB foot is observed. The self generated ExB shearing increases rapidly after the H-mode transition in off-axis ICRF heated discharges, before other profile changes are observed. Gyrokinetic analyses indicate that this spontaneous shearing rate is comparable to the linear ITG growth rate at the ITB location and may be responsible for stabilizing the underlying turbulence. Detailed measurement of the ion temperature demonstrates that the radial profile also flattens as the ICRF resonance position moves off axis. This decreases R/LTi in the barrier region, lessening the drive for the ITG turbulence and the resulting particle transport. The reduction in particle transport resulting from increase in core stability allows the neoclassical pinch to peak the density and pressure on axis. This suggests that spontaneous rotation is a potential tool for plasma profile control in reactor plasmas. The experimental results and corresponding gyrokinetic study will be presented. US-DoE DE-FC02-99ER54512 and DE-FG03-96ER54373.

  16. Overview of MST Research

    NASA Astrophysics Data System (ADS)

    Sarff, J. S.; MST Team

    2011-10-01

    MST progress in advancing the RFP for (1) fusion plasma confinement with minimal external magnetization, (2) toroidal confinement physics, and (3) basic plasma physics is summarized. New tools and diagnostics are accessing physics barely studied in the RFP. Several diagnostic advances are important for ITER/burning plasma. A 1 MW neutral beam injector operates routinely for fast ion, heating, and transport investigations. Energetic ions are also created spontaneously by tearing mode reconnection, reminiscent of astrophysical plasmas. Classical confinement of impurity ions is measured in reduced-tearing plasmas. Fast ion slowing-down is also classical. Alfven-eigenmode-like activity occurs with NBI, but apparently not TAE. Stellarator-like helical structure appears in the core of high current plasmas, with improved confinement characteristics. FIR interferometry, Thomson scattering, and HIBP diagnostics are beginning to explore microturbulence scales, an opportunity to exploit the RFP's high beta and strong magnetic shear parameter space. A programmable power supply for the toroidal field flexibly explores scenarios from advanced inductive profile control to low current tokamak operation. A 1 MW 5.5 GHz source for electron Bernstein wave injection is nearly complete to investigate heating and current drive in over-dense plasmas. Supported by DOE and NSF.

  17. Development of Long-Pulse Heating and Current Drive Actuators and Operational Techniques Compatible with a High-Z Divertor and First Wall

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Guiding

    Accurate measurement of the edge electron density profile is essential to optimizing antenna coupling and assessment of impurity contamination in studying long-pulse plasma heating and current drive in fusion devices. Measurement of the edge density profile has been demonstrated on the US fusion devices such as C-Mod, DIII-D, and TFTR amongst many devices, and has been used for RF loading and impurity modeling calculations for many years. University of Science and Technology of China (USTC) has recently installed a density profile reflectometer system on the EAST fusion device at the Institute of Plasma Physics, Chinese Academy of Sciences in Chinamore » based on the University of California Los Angeles (UCLA)-designed reflectometer system on the DIII-D fusion device at General Atomics Company in San Diego, California. UCLA has been working with USTC to optimize the existing microwave antenna, waveguide system, microwave electronics, and data analysis to produce reliable edge density profiles. During the past budget year, progress has been made in all three major areas: effort to achieve reliable system operations under various EAST operational conditions, effort to optimize system performance, and effort to provide quality density profiles into EAST’s database routinely.« less

  18. Effects of low central fuelling on density and ion temperature profiles in reversed shear plasmas on JT-60U

    NASA Astrophysics Data System (ADS)

    Takenaga, H.; Ide, S.; Sakamoto, Y.; Fujita, T.; JT-60 Team

    2008-07-01

    Effects of low central fuelling on density and ion temperature profiles have been investigated using negative ion based neutral beam injection and electron cyclotron heating (ECH) in reversed shear plasmas on JT-60U. Strong internal transport barrier (ITB) was maintained in density and ion temperature profiles, when central fuelling was decreased by switching positive ion based neutral beam injection to ECH after the strong ITB formation. Similar density and ion temperature ITBs were formed for the low and high central fuelling cases during the plasma current ramp-up phase. Strong correlation between the density gradient and the ion temperature gradient was observed, indicating that particle transport and ion thermal transport are strongly coupled or the density gradient assists the ion temperature ITB formation through suppression of drift wave instabilities such as ion temperature gradient mode. These results support that the density and ion temperature ITBs can be formed under reactor relevant conditions.

  19. Fluctuation reduction and enhanced confinement in the MST reversed-field pinch

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chapman, Brett Edward

    1997-10-01

    Plasmas with a factor of ≥3 improvement in energy confinement have been achieved in the MST reversed-field pinch (RFP). These plasmas occur spontaneously, following sawtooth crashes, subject to constraints on, eg, toroidal magnetic field reversal and wall conditioning. Possible contributors to the improved confinement include a reduction of core-resonant, global magnetic fluctuations and a reduction of electrostatic fluctuations over the entire plasma edge. One feature of these plasmas is a region of strong ExB flow shear in the edge. Never before observed in conjunction with enhanced confinement in the RFP, such shear is common in enhanced confinement discharges in tokamaks and stellarators. Another feature of these plasmas is a new type of discrete dynamo event. Like sawtooth crashes, a common form of discrete dynamo, these events correspond to bursts of edge parallel current. The reduction of electrostatic fluctuations in these plasmas occurs within and beyond the region of strong ExB flow shear, similar to what is observed in tokamaks and stellarators. However, the reductions in the MST include fluctuations whose correlation lengths are larger than the width of the shear region. The reduction of the global magnetic fluctuations is most likely due to flattening of the μ=μ 0more » $$\\vec{J}$$∙$$\\vec{B}$$/B 2 profile. Flattening can occur, eg, due to the new type of discrete dynamo event and reduced edge resistivity. Enhanced confinement plasmas are also achieved in the MST when auxiliary current is applied to flatten the μ profile and reduce magnetic fluctuations. Unexpectedly, these plasmas also exhibit a region (broader than in the case above) of strong ExB flow shear in the edge, an edge-wide reduction of electrostatic fluctuations, and the new type of discrete dynamo event. Auxiliary current drive has historically been viewed as the principal route to fusion reactor viability for the RFP.« less

  20. Excitation of a global plasma mode by an intense electron beam in a dc discharge

    DOE PAGES

    Sydorenko, D.; Kaganovich, I. D.; Ventzek, P. L. G.; ...

    2018-01-01

    The interaction of an intense electron beam with a finite-length, inhomogeneous plasma is investigated numerically. The plasma density profile is maximal in the middle and decays towards the plasma edges. Two regimes of the two-stream instability are observed. In one regime, the frequency of the instability is the plasma frequency at the density maximum and plasma waves are excited in the middle of the plasma. In the other regime, the frequency of the instability matches the local plasma frequency near the edges of the plasma and the intense plasma oscillations occur near plasma boundaries. The latter regime appears sporadically andmore » only for strong electron beam currents. This instability generates a copious amount of suprathermal electrons. Finally, the energy transfer to suprathermal electrons is the saturation mechanism of the instability.« less

  1. Excitation of a global plasma mode by an intense electron beam in a dc discharge

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sydorenko, D.; Kaganovich, I. D.; Ventzek, P. L. G.

    The interaction of an intense electron beam with a finite-length, inhomogeneous plasma is investigated numerically. The plasma density profile is maximal in the middle and decays towards the plasma edges. Two regimes of the two-stream instability are observed. In one regime, the frequency of the instability is the plasma frequency at the density maximum and plasma waves are excited in the middle of the plasma. In the other regime, the frequency of the instability matches the local plasma frequency near the edges of the plasma and the intense plasma oscillations occur near plasma boundaries. The latter regime appears sporadically andmore » only for strong electron beam currents. This instability generates a copious amount of suprathermal electrons. Finally, the energy transfer to suprathermal electrons is the saturation mechanism of the instability.« less

  2. Effects of current on droplet generation and arc plasma in gas metal arc welding

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hu, J.; Tsai, H. L.

    2006-09-01

    In gas metal arc welding (GMAW), a technology using pulsed currents has been employed to achieve the one-droplet-per-pulse (ODPP) metal transfer mode with the advantages of low average currents, a stable and controllable droplet generation, and reduced spatter. In this paper, a comprehensive model was developed to study the effects of different current profiles on the droplet formation, plasma generation, metal transfer, and weld pool dynamics in GMAW. Five types of welding currents were studied, including two constant currents and three wave form currents. In each type, the transient temperature and velocity distributions of the arc plasma and the moltenmore » metal, and the shapes of the droplet and the weld pool were calculated. The results showed that a higher current generates smaller droplets, higher droplet frequency, and higher electromagnetic force that becomes the dominant factor detaching the droplet from the electrode tip. The model has demonstrated that a stable ODPP metal transfer mode can be achieved by choosing a current with proper wave form for given welding conditions.« less

  3. Impact of ideal MHD stability limits on high-beta hybrid operation

    NASA Astrophysics Data System (ADS)

    Piovesan, P.; Igochine, V.; Turco, F.; Ryan, D. A.; Cianciosa, M. R.; Liu, Y. Q.; Marrelli, L.; Terranova, D.; Wilcox, R. S.; Wingen, A.; Angioni, C.; Bock, A.; Chrystal, C.; Classen, I.; Dunne, M.; Ferraro, N. M.; Fischer, R.; Gude, A.; Holcomb, C. T.; Lebschy, A.; Luce, T. C.; Maraschek, M.; McDermott, R.; Odstrčil, T.; Paz-Soldan, C.; Reich, M.; Sertoli, M.; Suttrop, W.; Taylor, N. Z.; Weiland, M.; Willensdorfer, M.; The ASDEX Upgrade Team; The DIII-D Team; The EUROfusion MST1 Team

    2017-01-01

    The hybrid scenario is a candidate for stationary high-fusion gain tokamak operation in ITER and DEMO. To obtain such performance, the energy confinement and the normalized pressure {βN} must be maximized, which requires operating near or above ideal MHD no-wall limits. New experimental findings show how these limits can affect hybrid operation. Even if hybrids are mainly limited by tearing modes, proximity to the no-wall limit leads to 3D field amplification that affects plasma profiles, e.g. rotation braking is observed in ASDEX Upgrade throughout the plasma and peaks in the core. As a result, even the small ASDEX Upgrade error fields are amplified and their effects become visible. To quantify such effects, ASDEX Upgrade measured the response to 3D fields applied by 8× 2 non-axisymmetric coils as {βN} approaches the no-wall limit. The full n  =  1 response profile and poloidal structure were measured by a suite of diagnostics and compared with linear MHD simulations, revealing a characteristic feature of hybrids: the n  =  1 response is due to a global, marginally-stable n  =  1 kink characterized by a large m  =  1, n  =  1 core harmonic due to q min being just above 1. A helical core distortion of a few cm forms and affects various core quantities, including plasma rotation, electron and ion temperature, and intrinsic W density. In similar experiments, DIII-D also measured the effect of this helical core on the internal current profile, providing information useful to understanding of the physics of magnetic flux pumping, i.e. anomalous current redistribution by MHD modes that keeps {{q}\\text{min}}>1 . Thanks to flux pumping, a broad current profile is maintained in DIII-D even with large on-axis current drive, enabling fully non-inductive operation at high {βN} up to 3.5-4.

  4. Impact of ideal MHD stability limits on high-beta hybrid operation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Piovesan, Paolo; Igochine, V.; Turco, F.

    Here, the hybrid scenario is a candidate for stationary high-fusion gain tokamak operation in ITER and DEMO. To obtain such performance, the energy confinement and the normalized pressuremore » $${{\\beta}_{N}}$$ must be maximized, which requires operating near or above ideal MHD no-wall limits. New experimental findings show how these limits can affect hybrid operation. Even if hybrids are mainly limited by tearing modes, proximity to the no-wall limit leads to 3D field amplification that affects plasma profiles, e.g. rotation braking is observed in ASDEX Upgrade throughout the plasma and peaks in the core. As a result, even the small ASDEX Upgrade error fields are amplified and their effects become visible. To quantify such effects, ASDEX Upgrade measured the response to 3D fields applied by $$8\\times 2$$ non-axisymmetric coils as $${{\\beta}_{N}}$$ approaches the no-wall limit. The full n = 1 response profile and poloidal structure were measured by a suite of diagnostics and compared with linear MHD simulations, revealing a characteristic feature of hybrids: the n = 1 response is due to a global, marginally-stable n = 1 kink characterized by a large m = 1, n = 1 core harmonic due to q min being just above 1. A helical core distortion of a few cm forms and affects various core quantities, including plasma rotation, electron and ion temperature, and intrinsic W density. In similar experiments, DIII-D also measured the effect of this helical core on the internal current profile, providing information useful to understanding of the physics of magnetic flux pumping, i.e. anomalous current redistribution by MHD modes that keeps $${{q}_{\\text{min}}}>1$$ . Thanks to flux pumping, a broad current profile is maintained in DIII-D even with large on-axis current drive, enabling fully non-inductive operation at high $${{\\beta}_{N}}$$ up to 3.5–4.« less

  5. Impact of ideal MHD stability limits on high-beta hybrid operation

    DOE PAGES

    Piovesan, Paolo; Igochine, V.; Turco, F.; ...

    2016-10-27

    Here, the hybrid scenario is a candidate for stationary high-fusion gain tokamak operation in ITER and DEMO. To obtain such performance, the energy confinement and the normalized pressuremore » $${{\\beta}_{N}}$$ must be maximized, which requires operating near or above ideal MHD no-wall limits. New experimental findings show how these limits can affect hybrid operation. Even if hybrids are mainly limited by tearing modes, proximity to the no-wall limit leads to 3D field amplification that affects plasma profiles, e.g. rotation braking is observed in ASDEX Upgrade throughout the plasma and peaks in the core. As a result, even the small ASDEX Upgrade error fields are amplified and their effects become visible. To quantify such effects, ASDEX Upgrade measured the response to 3D fields applied by $$8\\times 2$$ non-axisymmetric coils as $${{\\beta}_{N}}$$ approaches the no-wall limit. The full n = 1 response profile and poloidal structure were measured by a suite of diagnostics and compared with linear MHD simulations, revealing a characteristic feature of hybrids: the n = 1 response is due to a global, marginally-stable n = 1 kink characterized by a large m = 1, n = 1 core harmonic due to q min being just above 1. A helical core distortion of a few cm forms and affects various core quantities, including plasma rotation, electron and ion temperature, and intrinsic W density. In similar experiments, DIII-D also measured the effect of this helical core on the internal current profile, providing information useful to understanding of the physics of magnetic flux pumping, i.e. anomalous current redistribution by MHD modes that keeps $${{q}_{\\text{min}}}>1$$ . Thanks to flux pumping, a broad current profile is maintained in DIII-D even with large on-axis current drive, enabling fully non-inductive operation at high $${{\\beta}_{N}}$$ up to 3.5–4.« less

  6. Suppression of energetic particle driven instabilities with HHFW heating

    DOE PAGES

    Fredrickson, E. D.; Taylor, G.; Bertelli, N.; ...

    2015-01-01

    In plasmas in the National Spherical Torus Experiment (NSTX) [Ono et al., Nucl. Fusion 40 (2000) 557] heated with neutral beams, the beam ions typically excite Energetic Particle Modes (EPMs or fishbones), and Toroidal, Global or Compressional Alfvén Eigenmodes (TAE, GAE, CAE). These modes can redistribute the energetic beam ions, altering the beam driven current profile and the plasma heating profile, or they may affect electron thermal transport or cause losses of the beam ions. In this paper we present experimental results where these instabilities, driven by the super-thermal beam ions, are suppressed with the application of High Harmonic Fastmore » Wave heating.« less

  7. Veff Scaling of Te and ne Measurements During Local Helicity Injection on the Pegasus Toroidal Experiment

    NASA Astrophysics Data System (ADS)

    Bodner, G. M.; Bongard, M. W.; Fonck, R. J.; Perry, J. M.; Reusch, J. A.; Rodriguez Sanchez, C.

    2017-10-01

    Understanding the electron confinement of local helicity injection (LHI) is critical in order to evaluate its scalability as a startup technique to MA-class devices. Electron confinement in the Pegasus Toroidal Experiment is investigated using multi-point Thomson scattering (TS). The Pegasus TS system utilizes a set of high-throughput transmission gratings and intensified CCDs to measure Te and ne profiles. Previous TS measurements indicated peaked Te profiles 120 eV in outboard injector discharges characterized by strong inductive drive and low LHI drive. Injectors designed to have dominant non-inductive drive have recently been installed in the divertor region of Pegasus to understand the relationship between effective drive voltage, Veff, and plasma performance. At low Veff and reduced plasma current, Ip 60 kA, TS measurements reveal a flat Te profile 50 eV, with a peaked ne profile 1 ×1019 m-3, resulting in a slightly peaked pe profile. As current drive is increased, the Te profiles become hollow with a core Te 50 eV and an edge Te 120 -150 eV. These hollow profiles appear after the start of the Ip flattop and are sustained until the discharge terminates. The ne profiles drop in magnitude to < 1 ×1019 m-3 but remain somewhat peaked. Initial results suggest a weak scaling between input power and core Te. Additional studies are planned to identify the mechanisms behind the anomalous profile features. Work supported by US DOE Grant DE-FG02-96ER54375.

  8. Quasi-linear modeling of lower hybrid current drive in ITER and DEMO

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cardinali, A., E-mail: alessandro.cardinali@enea.it; Cesario, R.; Panaccione, L.

    2015-12-10

    First pass absorption of the Lower Hybrid waves in thermonuclear devices like ITER and DEMO is modeled by coupling the ray tracing equations with the quasi-linear evolution of the electron distribution function in 2D velocity space. As usually assumed, the Lower Hybrid Current Drive is not effective in a plasma of a tokamak fusion reactor, owing to the accessibility condition which, depending on the density, restricts the parallel wavenumber to values greater than n{sub ∥crit} and, at the same time, to the high electron temperature that would enhance the wave absorption and then restricts the RF power deposition to themore » very periphery of the plasma column (near the separatrix). In this work, by extensively using the “ray{sup star}” code, a parametric study of the propagation and absorption of the LH wave as function of the coupled wave spectrum (as its width, and peak value), has been performed very accurately. Such a careful investigation aims at controlling the power deposition layer possibly in the external half radius of the plasma, thus providing a valuable aid to the solution of how to control the plasma current profile in a toroidal magnetic configuration, and how to help the suppression of MHD mode that can develop in the outer part of the plasma. This analysis is useful not only for exploring the possibility of profile control of a pulsed operation reactor as well as the tearing mode stabilization, but also in order to reconsider the feasibility of steady state regime for DEMO.« less

  9. Spectroscopic investigation of the high-current phase of a pulsed GMAW process

    NASA Astrophysics Data System (ADS)

    Rouffet, M. E.; Wendt, M.; Goett, G.; Kozakov, R.; Schoepp, H.; Weltmann, K. D.; Uhrlandt, D.

    2010-11-01

    While metal vapours have an important impact on the efficiency of the pulsed gas metal arc welding process, only a few papers are focused on this effect. In this paper, methods based on emission spectroscopy are performed to improve the understanding of the physical phenomena occurring during the high-current pulse. Boltzmann plots applied to iron lines, the Stark broadening of the 696.5 nm argon line and composition calculations assuming local thermodynamic equilibrium are used to determine characteristic parameters of the plasma. It is observed that the central part of the arc is composed mainly of iron. The percentage of iron increases quickly at the beginning of the high-current pulse, and slowly decreases when the central part broadens. During the high-current phase the temperature profile has a minimum value of around 8000 K at the axis of the arc while the argon envelope of the central part reaches temperatures of approximately 13.000 K. The high percentage of iron and the high radiation of the plasma at the centre can explain the measured shape of the temperature profile.

  10. Study of electromagnetic wave scattering from an inhomogeneous plasma layer using Green's function volume integral equation method

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Soltanmoradi, Elmira; Shokri, Babak, E-mail: b-shokri@sbu.ac.ir; Laser and Plasma Research Institute, Shahid Beheshti University, G. C., Evin, Tehran 19839-63113

    Gigahertz electromagnetic wave scattering from an inhomogeneous collisional plasma layer with bell-like and Epstein electron density distributions is studied by the Green's function volume integral equation method to find the reflectance, transmittance, and absorbance coefficients of this inhomogeneous plasma. Also, the effects of the frequency of the electromagnetic wave, plasma parameters, such as collision frequency, electron density, and plasma thickness, and the effects of the profile of the electron density on the electromagnetic wave scattering from this plasma slab are investigated. According to the results, when the electron density, collision frequency, and plasma thickness are increased, collisional absorbance is enhanced,more » and as a result, the absorbance bandwidth of plasma is broadened. Moreover, this broadening is more evident for plasma with bell-like electron density profile. Also, the bandwidth of the frequency and the range of pressure in which plasma behaves as a good reflector are determined in this article. According to the results, the bandwidth of the frequency is decreased for thicker plasma with bell-like profile, while it does not vary for a different plasma thickness with Epstein profile. Moreover, the range of the pressure is decreased for bell-like profile in comparison with Epstein profile. Furthermore, due to the sharp inhomogeneity of the Epstein profile, the coefficients of plasma that are uniform for plasma with bell-like profile are changed for plasma with Epstein profile, and some perturbations are seen.« less

  11. Dependency of Tearing Mode Stability on Current and Pressure Profiles in DIII-D Hybrid Discharges

    NASA Astrophysics Data System (ADS)

    Kim, K.; Park, J. M.; Murakami, M.; La Haye, R. J.; Na, Y.-S.; SNU/ORAU; ORNL; Atomics, General; SNU; DIII-D Team

    2016-10-01

    Understanding the physics of the onset and evolution of tearing modes (TMs) in tokamak plasmas is important for high- β steady-state operation. Based on DIII-D steady-state hybrid experiments with accurate equilibrium reconstruction and well-measured plasma profiles, the 2/1 tearing mode can be more stable with increasing local current and pressure gradient at rational surface and with lower pressure peaking and plasma inductance. The tearing stability index Δ', estimated by the Rutherford equation with experimental mode growth rate was validated against Δ' calculated by linear eigenvalue solver (PEST3); preliminary comprehensive MHD modeling by NIMROD reproduced the TM onset reasonably well. We present a novel integrated modeling for the purpose of predicting TM onset in experiment by combining a model equilibrium reconstruction using IPS/FASTRAN, linear stability Δ' calculation using PEST3, and fitting formula for critical Δ' from NIMROD. Work supported in part by the US DoE under DE-AC05-06OR23100, DE-AC05-00OR22725, and DEFC02-04ER54698.

  12. Development And Characterization Of A Liner-On-Target Injector For Staged Z-Pinch Experiments

    NASA Astrophysics Data System (ADS)

    Valenzuela, J. C.; Conti, F.; Krasheninnikov, I.; Narkis, J.; Beg, F.; Wessel, F. J.; Rahman, H. U.

    2016-10-01

    We present the design and optimization of a liner-on-target injector for Staged Z-pinch experiments. The injector is composed of an annular high atomic number (e.g. Ar, Kr) gas-puff and an on-axis plasma gun that delivers the ionized deuterium target. The liner nozzle injector has been carefully studied using Computational Fluid Dynamics (CFD) simulations to produce a highly collimated 1 cm radius gas profile that satisfies the theoretical requirement for best performance on the 1 MA Zebra current driver. The CFD simulations produce density profiles as a function of the nozzle shape and gas. These profiles are initialized in the MHD MACH2 code to find the optimal liner density for a stable, uniform implosion. We use a simple Snowplow model to study the plasma sheath acceleration in a coaxial plasma gun to help us properly design the target injector. We have performed line-integrated density measurements using a CW He-Ne laser to characterize the liner gas and the plasma gun density as a function of time. The measurements are compared with models and calculations and benchmarked accordingly. Advanced Research Projects Agency - Energy, DE-AR0000569.

  13. High performance advanced tokamak regimes in DIII-D for next-step experiments

    NASA Astrophysics Data System (ADS)

    Greenfield, C. M.; Murakami, M.; Ferron, J. R.; Wade, M. R.; Luce, T. C.; Petty, C. C.; Menard, J. E.; Petrie, T. W.; Allen, S. L.; Burrell, K. H.; Casper, T. A.; DeBoo, J. C.; Doyle, E. J.; Garofalo, A. M.; Gorelov, I. A.; Groebner, R. J.; Hobirk, J.; Hyatt, A. W.; Jayakumar, R. J.; Kessel, C. E.; La Haye, R. J.; Jackson, G. L.; Lohr, J.; Makowski, M. A.; Pinsker, R. I.; Politzer, P. A.; Prater, R.; Strait, E. J.; Taylor, T. S.; West, W. P.; DIII-D Team

    2004-05-01

    Advanced Tokamak (AT) research in DIII-D [K. H. Burrell for the DIII-D Team, in Proceedings of the 19th Fusion Energy Conference, Lyon, France, 2002 (International Atomic Energy Agency, Vienna, 2002) published on CD-ROM] seeks to provide a scientific basis for steady-state high performance operation in future devices. These regimes require high toroidal beta to maximize fusion output and poloidal beta to maximize the self-driven bootstrap current. Achieving these conditions requires integrated, simultaneous control of the current and pressure profiles, and active magnetohydrodynamic stability control. The building blocks for AT operation are in hand. Resistive wall mode stabilization via plasma rotation and active feedback with nonaxisymmetric coils allows routine operation above the no-wall beta limit. Neoclassical tearing modes are stabilized by active feedback control of localized electron cyclotron current drive (ECCD). Plasma shaping and profile control provide further improvements. Under these conditions, bootstrap supplies most of the current. Steady-state operation requires replacing the remaining Ohmic current, mostly located near the half radius, with noninductive external sources. In DIII-D this current is provided by ECCD, and nearly stationary AT discharges have been sustained with little remaining Ohmic current. Fast wave current drive is being developed to control the central magnetic shear. Density control, with divertor cryopumps, of AT discharges with edge localized moding H-mode edges facilitates high current drive efficiency at reactor relevant collisionalities. A sophisticated plasma control system allows integrated control of these elements. Close coupling between modeling and experiment is key to understanding the separate elements, their complex nonlinear interactions, and their integration into self-consistent high performance scenarios. Progress on this development, and its implications for next-step devices, will be illustrated by results of recent experiment and simulation efforts.

  14. Stability analysis of the high poloidal bet scenario on DIII-Dtowards operation athigher plasma current

    NASA Astrophysics Data System (ADS)

    Guo, W. F.; Gong, X. Z.; Huang, J.; Ren, Q. L.; Qian, J. P.; Ding, S. Y.; Pan, C. K.; Li, G. Q.; Xia, T. Y.; Garofalo, A. M.; Lao, L.; Hyatt, A.; Ferron, J.; Meneghini, O.; Liu, Y. Q.; McClenaghan, J.; Holcomb, C. T.

    2017-10-01

    The high poloidal beta scenario with plasma current IP 600 kA and large-radius internal transport barrier (ITB) on DIII-D is subject to n =1 MHD kink modes when the current profile becomes very broad at internal inductance values li 0.5-0.6. It is desirable to extend this scenario to higer plasma current ( 1 MA) for highernormalized fusionperformance. However, higher current at constant normalized beta, ?N 3, would reducethe poloidal bet, ?P, below the threshold for ITB sustainment, observed at ?P 1.9. Thus, to avoid loss of the IT, ?N?? must be increased together with IP while avoiding the kink instability. MHD analysis is presented that explains possible paths to high ?N stability limit for the kink mode in tis scenario. Work supported by National Magnetic Confinement Fusion Program of Chin under 2015GB110001 and 2015GB102000 - National Natural Science Foundation of China under Grant No. 1147521 and by US DOE under DE-FC02-04ER54698.

  15. Core transport properties in JT-60U and JET identity plasmas

    NASA Astrophysics Data System (ADS)

    Litaudon, X.; Sakamoto, Y.; de Vries, P. C.; Salmi, A.; Tala, T.; Angioni, C.; Benkadda, S.; Beurskens, M. N. A.; Bourdelle, C.; Brix, M.; Crombé, K.; Fujita, T.; Futatani, S.; Garbet, X.; Giroud, C.; Hawkes, N. C.; Hayashi, N.; Hoang, G. T.; Hogeweij, G. M. D.; Matsunaga, G.; Nakano, T.; Oyama, N.; Parail, V.; Shinohara, K.; Suzuki, T.; Takechi, M.; Takenaga, H.; Takizuka, T.; Urano, H.; Voitsekhovitch, I.; Yoshida, M.; ITPA Transport Group; JT-60 Team; EFDA contributors, JET

    2011-07-01

    The paper compares the transport properties of a set of dimensionless identity experiments performed between JET and JT-60U in the advanced tokamak regime with internal transport barrier, ITB. These International Tokamak Physics Activity, ITPA, joint experiments were carried out with the same plasma shape, toroidal magnetic field ripple and dimensionless profiles as close as possible during the ITB triggering phase in terms of safety factor, normalized Larmor radius, normalized collision frequency, thermal beta, ratio of ion to electron temperatures. Similarities in the ITB triggering mechanisms and sustainment were observed when a good match was achieved of the most relevant normalized profiles except the toroidal Mach number. Similar thermal ion transport levels in the two devices have been measured in either monotonic or non-monotonic q-profiles. In contrast, differences between JET and JT-60U were observed on the electron thermal and particle confinement in reversed magnetic shear configurations. It was found that the larger shear reversal in the very centre (inside normalized radius of 0.2) of JT-60U plasmas allowed the sustainment of stronger electron density ITBs compared with JET. As a consequence of peaked density profile, the core bootstrap current density is more than five times higher in JT-60U compared with JET. Thanks to the bootstrap effect and the slightly broader neutral beam deposition, reversed magnetic shear configurations are self-sustained in JT-60U scenarios. Analyses of similarities and differences between the two devices address key questions on the validity of the usual assumptions made in ITER steady scenario modelling, e.g. a flat density profile in the core with thermal transport barrier? Such assumptions have consequences on the prediction of fusion performance, bootstrap current and on the sustainment of the scenario.

  16. Current profile control experiments in EXTRAP T2R

    NASA Astrophysics Data System (ADS)

    Brunsell, P.; Cecconello, M.; Drake, J.; Franz, P.; Malmberg, J. A.; Marrelli, L.; Martin, P.; Spizzo, G.

    2002-11-01

    EXTRAP T2R is a high aspect ratio (R=1.24 m, a = 0.183 m) reversed-field pinch device, characterised by a double, thin shell system. The simultaneous presence of many m=1, |n| > 11 tearing modes is responsible for a magnetic field turbulence, which is believed to produce the rather high energy and particle transport that is observed in this type of magnetic configuration. In this paper first results from current profile control experiments (PPCD) in a thin shell device are shown. When an edge poloidal electric field is transiently applied, an increase of the electron temperature and of the electron density is seen, which is consistent with an increase of the thermal content of the plasma. At the same time, the soft x-ray emission, measured with a newly installed miniaturised camera, shows a peaking of the profile in the core. Furthermore, the amplitudes of the m=1 tearing modes are reduced and and the rotation velocities increase during PPCD, which is also consistent with a reduction of magnetic turbulence and a heating of the plasma

  17. Exploration of High Harmonic Fast Wave Heating on the National Spherical Torus Experiment

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    J.R. Wilson; R.E. Bell; S. Bernabei

    2003-02-11

    High Harmonic Fast Wave (HHFW) heating has been proposed as a particularly attractive means for plasma heating and current drive in the high-beta plasmas that are achievable in spherical torus (ST) devices. The National Spherical Torus Experiment (NSTX) [Ono, M., Kaye, S.M., Neumeyer, S., et al., Proceedings, 18th IEEE/NPSS Symposium on Fusion Engineering, Albuquerque, 1999, (IEEE, Piscataway, NJ (1999), p. 53.)] is such a device. An radio-frequency (rf) heating system has been installed on NSTX to explore the physics of HHFW heating, current drive via rf waves and for use as a tool to demonstrate the attractiveness of the STmore » concept as a fusion device. To date, experiments have demonstrated many of the theoretical predictions for HHFW. In particular, strong wave absorption on electrons over a wide range of plasma parameters and wave parallel phase velocities, wave acceleration of energetic ions, and indications of current drive for directed wave spectra have been observed. In addition HHFW heating has been used to explore the energy transport properties of NSTX plasmas, to create H-mode (high-confinement mode) discharges with a large fraction of bootstrap current and to control the plasma current profile during the early stages of the discharge.« less

  18. DOE Office of Scientific and Technical Information (OSTI.GOV)

    Spong, D.A.; Hirshman, S.P.; Whitson, J.C.

    A new class of low aspect ratio toroidal hybrid stellarators is found using more general plasma confinement optimization criterion than quasi-symmetrization. The plasma current profile and shape of the outer magnetic flux surface are used as control variables to achieve near constancy of the longitudinal invariant J* on internal flux surfaces (quasi-omnigeneity), in addition to a number of other desirable physics target properties. We find that a range of compact (small aspect ratio A), high {beta} (ratio of thermal energy to magnetic field energy), low plasma current devices exist which have significantly improved confinement both for thermal as well asmore » energetic (collisionless) particle components. With reasonable increases in magnetic field and geometric size, such devices can also be scaled to confine 3.5 MeV alpha particle orbits.« less

  19. Development of a high current 60 keV neutral lithium beam injector for beam emission spectroscopy measurements on fusion experiments.

    PubMed

    Anda, G; Dunai, D; Lampert, M; Krizsanóczi, T; Németh, J; Bató, S; Nam, Y U; Hu, G H; Zoletnik, S

    2018-01-01

    A 60 keV neutral lithium beam system was designed and built up for beam emission spectroscopy measurement of edge plasma on the KSTAR and EAST tokamaks. The electron density profile and its fluctuation can be measured using the accelerated lithium beam-based emission spectroscopy system. A thermionic ion source was developed with a SiC heater to emit around 4-5 mA ion current from a 14 mm diameter surface. The ion optic is following the 2 step design used on other devices with small modifications to reach about 2-3 cm beam diameter in the plasma at about 4 m from the ion source. A newly developed recirculating sodium vapour neutralizer neutralizes the accelerated ion beam at around 260-280 °C even during long (<20 s) discharges. A set of new beam diagnostic and manipulation techniques are applied to allow optimization, aiming, cleaning, and beam modulation. The maximum 60 keV beam energy with 4 mA ion current was successfully reached at KSTAR and at EAST. Combined with an efficient observation system, the Li-beam diagnostic enables the measurement of the density profile and fluctuations on the plasma turbulence time scale.

  20. Development of a high current 60 keV neutral lithium beam injector for beam emission spectroscopy measurements on fusion experiments

    NASA Astrophysics Data System (ADS)

    Anda, G.; Dunai, D.; Lampert, M.; Krizsanóczi, T.; Németh, J.; Bató, S.; Nam, Y. U.; Hu, G. H.; Zoletnik, S.

    2018-01-01

    A 60 keV neutral lithium beam system was designed and built up for beam emission spectroscopy measurement of edge plasma on the KSTAR and EAST tokamaks. The electron density profile and its fluctuation can be measured using the accelerated lithium beam-based emission spectroscopy system. A thermionic ion source was developed with a SiC heater to emit around 4-5 mA ion current from a 14 mm diameter surface. The ion optic is following the 2 step design used on other devices with small modifications to reach about 2-3 cm beam diameter in the plasma at about 4 m from the ion source. A newly developed recirculating sodium vapour neutralizer neutralizes the accelerated ion beam at around 260-280 °C even during long (<20 s) discharges. A set of new beam diagnostic and manipulation techniques are applied to allow optimization, aiming, cleaning, and beam modulation. The maximum 60 keV beam energy with 4 mA ion current was successfully reached at KSTAR and at EAST. Combined with an efficient observation system, the Li-beam diagnostic enables the measurement of the density profile and fluctuations on the plasma turbulence time scale.

  1. a Vacuum Ultraviolet Study of the Alcator C Tokamak Plasma Using a High Resolution, One-Dimensional Photon Counting Detector.

    NASA Astrophysics Data System (ADS)

    Benjamin, Russell D.

    A photon counting detector based on an image intensified photodiode array was developed to meet the needs of one particular area of spectroscopic study, the determination of the kinetic temperature of impurity species. The image intensifier incorporates 3 high strip current ( ~300 muA) microchannel plates in a 'Z' configuration to achieve the gain required for the detection of single photon events. The design, construction, and laboratory testing of this system to determine its suitability for fusion plasma diagnostics is described, in particular, the ability to measure emission line profiles in order to determine the kinetic temperature of the emitting species. The photon counting detector, mounted on the exit plane of a 1m Ebert-Fastie spectrometer, was used to make spectroscopic measurements of the local ion temperature in Alcator C plasmas using impurity emission lines. Alcator experiments on one particular method of RF heating in a tokamak plasma, the launching of Ion Bernstein waves (IBW), are discussed. The O V kinetic temperature increases during IBW injection as the pre-RF plasma density is raised (on a shot-to-shot basis) above the region in which significant increases in the central ion temperature are observed. In addition, ion temperature profiles were measured during Ion Bernstein wave experiments by combining this point derived from the fit to the emission line of O VII with neutral particle analyzer data. The incorporation of the O VII temperature point in the determination of the pre-RF ion temperature profile results in a significant reduction (~0.4 cm) in the characteristic width of this profile. The high resolution and geometric stability of the photon counting detector made possible the measurement of small wavelength shifts (Deltalambda ~ 0.01 A) and, therefore, the determination of small bulk plasma motions (in this case, poloidal rotation of the plasma) through the Doppler shift of impurity emission lines. The Zeeman effect makes a significant contribution to the measured line profile in high field tokamaks, even in the ultraviolet. Modelling of the Zeeman effect is discussed and applied to the impurity species observed in Alcator C plasmas. (Abstract shortened with permission of author.).

  2. Design of a portable optical emission tomography system for microwave induced compact plasma for visible to near-infrared emission lines

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rathore, Kavita, E-mail: kavira@iitk.ac.in, E-mail: pmunshi@iitk.ac.in, E-mail: sudeepb@iitk.ac.in; Munshi, Prabhat, E-mail: kavira@iitk.ac.in, E-mail: pmunshi@iitk.ac.in, E-mail: sudeepb@iitk.ac.in; Bhattacharjee, Sudeep, E-mail: kavira@iitk.ac.in, E-mail: pmunshi@iitk.ac.in, E-mail: sudeepb@iitk.ac.in

    A new non-invasive diagnostic system is developed for Microwave Induced Plasma (MIP) to reconstruct tomographic images of a 2D emission profile. A compact MIP system has wide application in industry as well as research application such as thrusters for space propulsion, high current ion beams, and creation of negative ions for heating of fusion plasma. Emission profile depends on two crucial parameters, namely, the electron temperature and density (over the entire spatial extent) of the plasma system. Emission tomography provides basic understanding of plasmas and it is very useful to monitor internal structure of plasma phenomena without disturbing its actualmore » processes. This paper presents development of a compact, modular, and versatile Optical Emission Tomography (OET) tool for a cylindrical, magnetically confined MIP system. It has eight slit-hole cameras and each consisting of a complementary metal–oxide–semiconductor linear image sensor for light detection. The optical noise is reduced by using aspheric lens and interference band-pass filters in each camera. The entire cylindrical plasma can be scanned with automated sliding ring mechanism arranged in fan-beam data collection geometry. The design of the camera includes a unique possibility to incorporate different filters to get the particular wavelength light from the plasma. This OET system includes selected band-pass filters for particular argon emission 750 nm, 772 nm, and 811 nm lines and hydrogen emission H{sub α} (656 nm) and H{sub β} (486 nm) lines. Convolution back projection algorithm is used to obtain the tomographic images of plasma emission line. The paper mainly focuses on (a) design of OET system in detail and (b) study of emission profile for 750 nm argon emission lines to validate the system design.« less

  3. Biasing experiments on the Advanced Toroidal Facility

    NASA Astrophysics Data System (ADS)

    Uckan, T.; Isler, R. C.; Jernigan, T. C.; Lyon, J. F.; Mioduszewski, P. K.; Murakami, M.; Rasmussen, D. A.; Wilgen, J. B.; Aceto, S. C.; Zielinski, J. J.

    1992-09-01

    Biasing experiments have been carried out in 1 T plasmas with approximately 200 kW of electron cyclotron heating (ECH) in the current-fire Advanced Toroidal Facility (ATF) torsatron. Two rail limiters, one at the top and one at the bottom of the device, located at the last closed flux surface (LCFS), are, biased at positive and negative potentials with respect to the vacuum vessel. When the limiters are positively biased at up to 300 V and the plasma density is controlled with a significantly reduced gas feed, the H(sub alpha) radiation from both the limiter and the wall drops, indicating reduced particle recycling as a result of improved particle confinement. For bias voltages around +100 V, there is almost no change of plasma stored energy W(sub p), but W(sub p) then drops with the higher biasing voltages. Positive biasing has caused the core plasma density profile to become peaked and the electric field to become more negative inside the LCFS. At the same time, edge plasma fluctuations are reduced significantly and their power spectrum becomes less broad. The propagation direction of these electrostatic fluctuations reverses to the ion diamagnetic direction, and their wavelengths become longer. The resulting fluctuation-induced particle flux is also reduced. Power deposition on the limiters is lower as a result of reduced edge plasma density and temperature. Negative biasing yields somewhat less improvement in the particle confinement while having almost no apparent effect on W(sub p) or on the core and the edge plasma density and temperature profiles. Simultaneous measurements of the plasma potential profile indicate almost no significant change. Biasing has almost no effect on the intrinsic impurity levels in the plasma.

  4. Control of linear modes in cylindrical resistive magnetohydrodynamics with a resistive wall, plasma rotation, and complex gain

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Brennan, D. P.; Finn, J. M.

    2014-10-15

    Feedback stabilization of magnetohydrodynamic (MHD) modes in a tokamak is studied in a cylindrical model with a resistive wall, plasma resistivity, viscosity, and toroidal rotation. The control is based on a linear combination of the normal and tangential components of the magnetic field just inside the resistive wall. The feedback includes complex gain, for both the normal and for the tangential components, and it is known that the imaginary part of the feedback for the former is equivalent to plasma rotation [J. M. Finn and L. Chacon, Phys. Plasmas 11, 1866 (2004)]. The work includes (1) analysis with a reducedmore » resistive MHD model for a tokamak with finite β and with stepfunction current density and pressure profiles, and (2) computations with a full compressible visco-resistive MHD model with smooth decreasing profiles of current density and pressure. The equilibria are stable for β = 0 and the marginal stability values β{sub rp,rw} < β{sub rp,iw} < β{sub ip,rw} < β{sub ip,iw} (resistive plasma, resistive wall; resistive plasma, ideal wall; ideal plasma, resistive wall; and ideal plasma, ideal wall) are computed for both models. The main results are: (a) imaginary gain with normal sensors or plasma rotation stabilizes below β{sub rp,iw} because rotation suppresses the diffusion of flux from the plasma out through the wall and, more surprisingly, (b) rotation or imaginary gain with normal sensors destabilizes above β{sub rp,iw} because it prevents the feedback flux from entering the plasma through the resistive wall to form a virtual wall. A method of using complex gain G{sub i} to optimize in the presence of rotation in this regime with β > β{sub rp,iw} is presented. The effect of imaginary gain with tangential sensors is more complicated but essentially destabilizes above and below β{sub rp,iw}.« less

  5. Calibrating ion density profile measurements in ion thruster beam plasma

    NASA Astrophysics Data System (ADS)

    Zhang, Zun; Tang, Haibin; Ren, Junxue; Zhang, Zhe; Wang, Joseph

    2016-11-01

    The ion thruster beam plasma is characterized by high directed ion velocity (104 m/s) and low plasma density (1015 m-3). Interpretation of measurements of such a plasma based on classical Langmuir probe theory can yield a large experimental error. This paper presents an indirect method to calibrate ion density determination in an ion thruster beam plasma using a Faraday probe, a retarding potential analyzer, and a Langmuir probe. This new method is applied to determine the plasma emitted from a 20-cm-diameter Kaufman ion thruster. The results show that the ion density calibrated by the new method can be as much as 40% less than that without any ion current density and ion velocity calibration.

  6. Observations of structuring in the downstream region of a large spherical model in a laboratory simulated solar wind plasma

    NASA Technical Reports Server (NTRS)

    Intriligator, D. S.; Steele, G. R.

    1982-01-01

    The effects of inserting a spherical conducting model, large in comparison with the Debye length, into a free streaming high-energy 1 kV) unmagnetized hydrogen plasma are investigated in order to measure energies and compositions directly relevant to solar wind and astrophysical plasma phenomena. Holding the incident plasma parameters constant, transverse profiles of the net Langmuir probe current are plotted at various locations downstream in the model wake and are divided into three regions (the shadow, transition, and boundary). Results attributable to the use of a high-energy plasma show that enhancements in the shadow exist at downstream locations where the Mach ratio is less than one, and turbulence exists in the transition region on the shadow edges and outside in the boundary region. In addition, a small current enhancement is found in the boundary and can be attributed to the plasma/model interaction. It is concluded that many similar features observed by spacecraft downstream from planetary bodies are relatively permanent and are due to the intrinsic nature of the interaction between the solar wind plasma and the obstacle.

  7. From Lawson to Burning Plasmas: a Multi-Fluid Approach

    NASA Astrophysics Data System (ADS)

    Guazzotto, Luca; Betti, Riccardo

    2017-10-01

    The Lawson criterion, easily compared to experimental parameters, gives the value for the triple product of plasma density, temperature and energy confinement time needed for the plasma to ignite. Lawson's inaccurate assumptions of 0D geometry and single-fluid plasma model were improved in recent work, where 1D geometry and multi-fluid (ions, electrons and alphas) physics were included in the model, accounting for physical equilibration times and different energy confinement times between species. A much more meaningful analysis than Lawson's for current and future experiment would be expressed in terms of burning plasma state (Q=5, where Q is the ratio between fusion power and heating power). Minimum parameters for reaching Q=5 are calculated based on experimental profiles for density and temperatures and can immediately be compared with experimental performance by defining a no-alpha pressure. This is done in terms of the pressure that the plasma needs to reach for breakeven once the alpha heating has been subtracted from the energy balance. These calculations can be applied to current experiments and future burning-plasma devices. DE-FG02-93ER54215.

  8. Compression dynamics of quasi-spherical wire arrays with different linear mass profiles

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mitrofanov, K. N., E-mail: mitrofan@triniti.ru; Aleksandrov, V. V.; Gritsuk, A. N.

    Results of experimental studies of the implosion of quasi-spherical wire (or metalized fiber) arrays are presented. The goal of the experiments was to achieve synchronous three-dimensional compression of the plasma produced in different regions of a quasi-spherical array into its geometrical center. To search for optimal synchronization conditions, quasi-spherical arrays with different initial profiles of the linear mass were used. The following dependences of the linear mass on the poloidal angle were used: m{sub l}(θ) ∝ sin{sup –1}θ and m{sub l}(θ) ∝ sin{sup –2}θ. The compression dynamics of such arrays was compared with that of quasi-spherical arrays without linear massmore » profiling, m{sub l}(θ) = const. To verify the experimental data, the spatiotemporal dynamics of plasma compression in quasi-spherical arrays was studied using various diagnostics. The experiments on three-dimensional implosion of quasi-spherical arrays made it possible to study how the frozen-in magnetic field of the discharge current penetrates into the array. By measuring the magnetic field in the plasma of a quasi-spherical array, information is obtained on the processes of plasma production and formation of plasma flows from the wire/fiber regions with and without an additionally deposited mass. It is found that penetration of the magnetic flux depends on the initial linear mass profile m{sub l}(θ) of the quasi-spherical array. From space-resolved spectral measurements and frame imaging of plasma X-ray emission, information is obtained on the dimensions and shape of the X-ray source formed during the implosion of a quasi-spherical array. The intensity of this source is estimated and compared with that of the Z-pinch formed during the implosion of a cylindrical array.« less

  9. Characterization of potential plasma biomarkers related to cognitive impairment by untargeted profiling of phospholipids using the HILIC-ESI-IT-TOF-MS system.

    PubMed

    Song, Shuang; Cheong, Ling-Zhi; Man, Qing-Qing; Pang, Shao-Jie; Li, Yue-Qi; Ren, Biao; Zhang, Jian

    2018-05-01

    Early diagnosis of neural changes causing cognitive impairment is critical for development of preventive therapies for dementia. Biomarkers currently characterized cannot be extensively applied due to the invasive sampling of cerebrospinal fluid. The other imaging approaches are either expensive or require a high technique. Phospholipids (PLs), which are basic constituents of neurons, might be a key variable in the pathogenesis of cognitive impairment. Changes in plasma PL provide the possibility for development of novel biomarkers with minimal invasion and high patient acceptance. In this work, a HILIC-ESI-IT-TOF-MS system was introduced for untargeted profiling of plasma PLs to investigate the relationship between changes of plasma PL profiles and cognitive impairment. A total of 272 types of PL molecular structures were characterized in human plasma and quantified through the internal standard method. Univariate analysis shows 29 PLs were significantly different between the control (n = 41) and the cognitive impairment (CI) group (n = 41). Multivariate analysis (PCA and OPLS-DA) was conducted based on these 29 potential PL biomarkers. Both univariate and multivariate analyses show abnormality of PL metabolism in the CI group, and the downregulation of ethanolamine plasmalogen (pPE) supply, especially those with PUFAs, in the circulation system should be strongly associated with neurodegeneration. A discriminative model was established with satisfied fit (R2) and prediction (Q2) abilities, and the classification test showed better recognition of the CI group than the control group indicating that this model of PL biomarkers could be used as indicators for screening of CI. Graphical abstract Characterization of potential plasma biomarkers related to cognitive impairment by untargeted profiling of phospholipids.

  10. High beta-N experiments at JET

    NASA Astrophysics Data System (ADS)

    Challis, Clive

    2007-11-01

    JET has investigated the performance potential and limitations of highly triangular plasmas relevant to fully non-inductive tokamak operation. The q-profile shape has been varied from cases with highly negative core magnetic shear to low shear with q0 close to 1, allowing the effect on confinement and stability to be studied. Operation with beta-N above the no-wall `limit' has been demonstrated for durations comparable with the resistive time and direct measurements of the no-wall beta have been developed as a tool for systematic performance optimization. Regimes have been developed with ITBs at reduced plasma current and toroidal field (1.2-1.5MA/2.3-2.7T) to obtain high values of beta-N and beta-P with either impurity seeding or quasi-double-null plasma configurations used to mitigate ELMs. The importance of the q-profile shape for performance optimization has been demonstrated in plasmas without ITBs (1.2MA/1.8T) with low values of minimum q (1-2) providing access to the highest beta-N (above 3).

  11. The real time multi point Thomson scattering diagnostic at NSTX-U

    NASA Astrophysics Data System (ADS)

    Laggner, Florian; Kolemen, Egemen; Diallo, Ahmed; Leblanc, Benoit; Rozenblat, Roman; Tchilinguirian, Greg; NSTX-U Team Team

    2017-10-01

    This contribution presents the upgrade of the multi point Thomson scattering (MPTS) diagnostic for real time application. As a key diagnostic at NSTX-U, the MPTS diagnostic simultaneously measures the electron density (ne) and electron temperature (Te) profiles of a plasma discharge. Therefore, this powerful diagnostic can directly access the electron pressure of the plasma. Currently, only post-discharge evaluation of the data is available, however, since the plasma pressure is one important drive for instabilities, real time measurements of this quantities would be beneficial for plasma control. In a first step, ten MPTS channels were equipped with real time electronics, which improve the data acquisition rate by five orders of magnitude. The commissioning of the system is ongoing and first benchmarks of the real time evaluation routines against the standard, post-discharge evaluation show promising results: The Te as well as ne profiles of both types of analyses agree within their uncertainties. This work was supported by the US Department of Energy under DE-SC0015878 and DE-SC0015480.

  12. A novel feedback algorithm for simulating controlled dynamics and confinement in the advanced reversed-field pinch

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dahlin, J.-E.; Scheffel, J.

    2005-06-15

    In the advanced reversed-field pinch (RFP), the current density profile is externally controlled to diminish tearing instabilities. Thus the scaling of energy confinement time with plasma current and density is improved substantially as compared to the conventional RFP. This may be numerically simulated by introducing an ad hoc electric field, adjusted to generate a tearing mode stable parallel current density profile. In the present work a current profile control algorithm, based on feedback of the fluctuating electric field in Ohm's law, is introduced into the resistive magnetohydrodynamic code DEBSP [D. D. Schnack and D. C. Baxter, J. Comput. Phys. 55,more » 485 (1984); D. D. Schnack, D. C. Barnes, Z. Mikic, D. S. Marneal, E. J. Caramana, and R. A. Nebel, Comput. Phys. Commun. 43, 17 (1986)]. The resulting radial magnetic field is decreased considerably, causing an increase in energy confinement time and poloidal {beta}. It is found that the parallel current density profile spontaneously becomes hollow, and that a formation, being related to persisting resistive g modes, appears close to the reversal surface.« less

  13. An investigation of transient pressures and plasma properties in a pinched plasma column. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Stover, E. K.; York, T. M.

    1971-01-01

    The transient pinched plasma column generated in a linear Z-pinch was studied experimentally and analytically. The plasma column was investigated experimentally with several plasma diagnostics; they were: a rapid response pressure transducer, a magnetic field probe, a voltage probe, and discharge luminosity. Axial pressure profiles on the discharge chamber axis were used to identify three characteristic regions of plasma column behavior: (1) strong axial pressure asymmetry noted early in plasma column lifetime, (2) followed by plasma heating in which there is a rapid rise in static pressure, and (3) a slight decrease static pressure before plasma column breakup. Plasma column lifetime was approximately 5 microseconds. The axial pressure asymmetry was attributed to nonsimultaneous pinching of the imploding current sheet along the discharge chamber axis. The rapid heating could be attributed in part to viscous effects introduced by radial gradients in the axial streaming velocity.

  14. Production of internal transport barriers via self-generated mean flows in Alcator C-Moda)

    NASA Astrophysics Data System (ADS)

    Fiore, C. L.; Ernst, D. R.; Podpaly, Y. A.; Mikkelsen, D.; Howard, N. T.; Lee, Jungpyo; Reinke, M. L.; Rice, J. E.; Hughes, J. W.; Ma, Y.; Rowan, W. L.; Bespamyatnov, I.

    2012-05-01

    New results suggest that changes observed in the intrinsic toroidal rotation influence the internal transport barrier (ITB) formation in the Alcator C-Mod tokamak [E. S. Marmar and Alcator C-Mod group, Fusion Sci. Technol. 51, 261 (2007)]. These arise when the resonance for ion cyclotron range of frequencies (ICRF) minority heating is positioned off-axis at or outside of the plasma half-radius. These ITBs form in a reactor relevant regime, without particle or momentum injection, with Ti ≈ Te, and with monotonic q profiles (qmin < 1). C-Mod H-mode plasmas exhibit strong intrinsic co-current rotation that increases with increasing stored energy without external drive. When the resonance position is moved off-axis, the rotation decreases in the center of the plasma resulting in a radial toroidal rotation profile with a central well which deepens and moves farther off-axis when the ICRF resonance location reaches the plasma half-radius. This profile results in strong E × B shear (>1.5 × 105 rad/s) in the region where the ITB foot is observed. Gyrokinetic analyses indicate that this spontaneous shearing rate is comparable to the linear ion temperature gradient (ITG) growth rate at the ITB location and is sufficient to reduce the turbulent particle and energy transport. New and detailed measurement of the ion temperature demonstrates that the radial profile flattens as the ICRF resonance position moves off axis, decreasing the drive for the ITG the instability as well. These results are the first evidence that intrinsic rotation can affect confinement in ITB plasmas.

  15. Plasma fuelling with cryogenic pellets in the stellarator TJ-II

    NASA Astrophysics Data System (ADS)

    McCarthy, K. J.; Panadero, N.; Velasco, J. L.; Combs, S. K.; Caughman, J. B. O.; Fontdecaba, J. M.; Foust, C.; García, R.; Hernández Sánchez, J.; Navarro, M.; Pastor, I.; Soleto, A.; the TJ-II Team

    2017-05-01

    Cryogenic pellet injection is a widely used technique for delivering fuel to the core of magnetically confined plasmas. Indeed, such systems are currently functioning on many tokamak, reversed field pinch and stellarator devices. A pipe-gun-type pellet injector is now operated on the TJ-II, a low-magnetic shear stellarator of the heliac type. Cryogenic hydrogen pellets, containing between 3  ×  1018 and 4  ×  1019 atoms, are injected at velocities between 800 and 1200 m s-1 from its low-field side into plasmas created and/or maintained in this device by electron cyclotron resonance and/or neutral beam injection heating. In this paper, the first systematic study of pellet ablation, particle deposition and fuelling efficiency is presented for TJ-II. From this, light-emission profiles from ablating pellets are found to be in reasonable agreement with simulated pellet ablation profiles (created using a neutral gas shielding-based code) for both heating scenarios. In addition, radial offsets between recorded light-emission profiles and particle deposition profiles provide evidence for rapid outward drifting of ablated material that leads to pellet particle loss from the plasma. Finally, fuelling efficiencies are documented for a range of target plasma densities (~4  ×  1018-  ~2  ×  1019 m-3). These range from ~20%-  ~85% and are determined to be sensitive to pellet penetration depth. Additional observations, such as enhanced core ablation, are discussed and planned future work is outlined.

  16. Generation and Sustainment of Plasma Rotation by ICRF Heating

    NASA Astrophysics Data System (ADS)

    Perkins, F. W.

    2000-10-01

    When tokamak plasmas are heated by the fundamental minority ion-cyclotron process, they are observed to rotate toroidally, even though this heating process introduces negligable angular momentum. This work proposes and evaluates a physics mechanism which resolves this apparent conflict. The argument has two elements. First, it is assumed that angular momentum transport is governed by a diffusion equation with a v_tor = 0 boundary condition at the plasma surface and a torque-density source. When the source consists of separated regions of positive and negative torque density, a finite central rotation velocity results, even though the volume integrated torque density - the angular momentum input - vanishes. Secondly, ions energized by the ICRF process can generate separated regions of positive and negative torque density. Heating increases their banana widths which leads to radial energetic-particle transport that must be balanced by neutralizing radial currents and a j_rB_pR torque density in the bulk plasma. Additional, comparable torque density results from collisional transfer of mechanical angular momentum from energetic particles to the bulk plasma and particle loss through banana particles impacting the wall. Monte-Carlo calculations utilizing the ORBIT code evaluate all sources of torque density and rigorously assure that no net angular momentum is introduced. Two models of ICRF heating, diffusive and instantaneous, give similar results. When the resonance location is on the LFS, the calculated rotation has the magnitude, profile, and co-current sense of Alcator C-Mod observations. For HFS resonance locations, the model predicts counter-current rotation. Scans of rotational profiles vs. resonance location, initial energy, particle loss, pitch, and qm will be presented as will the location of the velocity shear layer its scaling to a reactor.

  17. Effects of energetic particle phase space modifications by instabilities on integrated modeling

    NASA Astrophysics Data System (ADS)

    Podestà, M.; Gorelenkova, M.; Fredrickson, E. D.; Gorelenkov, N. N.; White, R. B.

    2016-11-01

    Tokamak plasmas can feature a large population of energetic particles (EP) from neutral beam injection or fusion reactions. In turn, energetic particles can drive instabilities, which affect the driving EP population leading to a distortion of the original EP distribution function and of quantities that depend on it. The latter include, for example, neutral beam (NB) current drive and plasma heating through EP thermalization. Those effects must be taken into account to enable reliable and quantitative simulations of discharges for present devices as well as predictions for future burning plasmas. Reduced models for EP transport are emerging as an effective tool for long time-scale integrated simulations of tokamak plasmas, possibly including the effects of instabilities on EP dynamics. Available models differ in how EP distribution properties are modified by instabilities, e.g. in terms of gradients in real or phase space. It is therefore crucial to assess to what extent different assumptions in the transport models affect predicted quantities such as EP profile, energy distribution, NB driven current and energy/momentum transfer to the thermal populations. A newly developed kick model, which includes modifications of the EP distribution by instabilities in both real and velocity space, is used in this work to investigate these issues. Coupled to TRANSP simulations, the kick model is used to analyze NB-heated NSTX and DIII-D discharges featuring unstable Alfvén eigenmodes (AEs). Results show that instabilities can strongly affect the EP distribution function, and modifications propagate to macroscopic quantities such as NB-driven current profile and NB power transferred to the thermal plasma species. Those important aspects are only qualitatively captured by simpler fast ion transport models that are based on radial diffusion of energetic ions only.

  18. Effects of energetic particle phase space modifications by instabilities on integrated modeling

    DOE PAGES

    Podesta, M.; Gorelenkova, M.; Fredrickson, E. D.; ...

    2016-07-22

    Tokamak plasmas can feature a large population of energetic particles (EP) from neutral beam injection or fusion reactions. In turn, energetic particles can drive instabilities, which affect the driving EP population leading to a distortion of the original EP distribution function and of quantities that depend on it. The latter include, for example, neutral beam (NB) current drive and plasma heating through EP thermalization. Those effects must be taken into account to enable reliable and quantitative simulations of discharges for present devices as well as predictions for future burning plasmas. Reduced models for EP transport are emerging as an effectivemore » tool for long time-scale integrated simulations of tokamak plasmas, possibly including the effects of instabilities on EP dynamics. Available models differ in how EP distribution properties are modified by instabilities, e.g. in terms of gradients in real or phase space. It is therefore crucial to assess to what extent different assumptions in the transport models affect predicted quantities such as EP profile, energy distribution, NB driven current and energy/momentum transfer to the thermal populations. A newly developed kick model, which includes modifications of the EP distribution by instabilities in both real and velocity space, is used in this work to investigate these issues. Coupled to TRANSP simulations, the kick model is used to analyze NB-heated NSTX and DIII-D discharges featuring unstable Alfvén eigenmodes (AEs). Results show that instabilities can strongly affect the EP distribution function, and modifications propagate to macroscopic quantities such as NB-driven current profile and NB power transferred to the thermal plasma species. Furthermore, those important aspects are only qualitatively captured by simpler fast ion transport models that are based on radial diffusion of energetic ions only.« less

  19. Imaging of turbulent structures and tomographic reconstruction of TORPEX plasma emissivity

    NASA Astrophysics Data System (ADS)

    Iraji, D.; Furno, I.; Fasoli, A.; Theiler, C.

    2010-12-01

    In the TORPEX [A. Fasoli et al., Phys. Plasmas 13, 055902 (2006)], a simple magnetized plasma device, low frequency electrostatic fluctuations associated with interchange waves, are routinely measured by means of extensive sets of Langmuir probes. To complement the electrostatic probe measurements of plasma turbulence and study of plasma structures smaller than the spatial resolution of probes array, a nonperturbative direct imaging system has been developed on TORPEX, including a fast framing Photron-APX-RS camera and an image intensifier unit. From the line-integrated camera images, we compute the poloidal emissivity profile of the plasma by applying a tomographic reconstruction technique using a pixel method and solving an overdetermined set of equations by singular value decomposition. This allows comparing statistical, spectral, and spatial properties of visible light radiation with electrostatic fluctuations. The shape and position of the time-averaged reconstructed plasma emissivity are observed to be similar to those of the ion saturation current profile. In the core plasma, excluding the electron cyclotron and upper hybrid resonant layers, the mean value of the plasma emissivity is observed to vary with (Te)α(ne)β, in which α =0.25-0.7 and β =0.8-1.4, in agreement with collisional radiative model. The tomographic reconstruction is applied to the fast camera movie acquired with 50 kframes/s rate and 2 μs of exposure time to obtain the temporal evolutions of the emissivity fluctuations. Conditional average sampling is also applied to visualize and measure sizes of structures associated with the interchange mode. The ω-time and the two-dimensional k-space Fourier analysis of the reconstructed emissivity fluctuations show the same interchange mode that is detected in the ω and k spectra of the ion saturation current fluctuations measured by probes. Small scale turbulent plasma structures can be detected and tracked in the reconstructed emissivity movies with the spatial resolution down to 2 cm, well beyond the spatial resolution of the probe array.

  20. Geometric scalings for the electrostatically driven helical plasma state

    NASA Astrophysics Data System (ADS)

    Akçay, Cihan; Finn, John M.; Nebel, Richard A.; Barnes, Daniel C.

    2017-12-01

    A new plasma state has been investigated [Akcay et al., Phys. Plasmas 24, 052503 (2017)], with a uniform applied axial magnetic field in a periodic cylinder of length L = 2 π R , driven by helical electrodes. The drive is single helicity, depending on m θ + k z = m θ - n ζ , where ζ = z / R and k = - n / R . For strong ( m , n ) = ( 1 , 1 ) drive, the state was found to have a strong axial mean current density, with a mean-field safety factor q 0 ( r ) just above the pitch of the electrodes m / n = 1 in the interior. This state has possible applications to DC electrical transformers and tailoring of the current profile in tokamaks. We study two geometric issues of interest for these applications: (i) scaling of properties with the plasma length or aspect ratio and (ii) behavior for different helicities, specifically ( m , n ) = ( 1 , n ) for n > 1 and ( m , n ) = ( 2 , 1 ) .

  1. Characterization of plasma processing induced charging damage to MOS devices

    NASA Astrophysics Data System (ADS)

    Ma, Shawming

    1997-12-01

    Plasma processing has become an integral part of the fabrication of integrated circuits and takes at least 30% of whole process steps since it offers advantages in terms of directionality, low temperature and process convenience. However, wafer charging during plasma processes is a significant concern for both thin oxide damage and profile distortion. In this work, the factors affecting this damage will be explained by plasma issues, device structure and oxide quality. The SPORT (Stanford Plasma On-wafer Real Time) charging probe was developed to investigate the charging mechanism of different plasma processes including poly-Si etching, resist ashing and PECVD. The basic idea of this probe is that it simulates a real device structure in the plasma environment and allows measurement of plasma induced charging voltages and currents directly in real time. This measurement is fully compatible with other charging voltage measurement but it is the only one to do in real-time. Effect of magnetic field induced plasma nonuniformity on spatial dependent charging is well understood by this measurement. In addition, the plasma parameters including ion current density and electron temperature can also be extracted from the probe's plasma I-V characteristics using a dc Langmuir probe like theory. It will be shown that the MOS device tunneling current from charging, the dependence on antenna ratio and the etch uniformity can all be predicted by using this measurement. Moreover, the real-time measurement reveals transient and electrode edge effect during processing. Furthermore, high aspect ratio pattern induced electron shading effects can also be characterized by the probe. On the oxide quality issue, wafer temperature during plasma processing has been experimentally shown to be critical to charging damage. Finally, different MOS capacitor testing methods including breakdown voltage, charge-to-breakdown, gate leakage current and voltage-time at constant current bias were compared to find the optimum method for charging device reliability testing.

  2. Direct measurements of safety factor profiles with motional Stark effect for KSTAR tokamak discharges with internal transport barriers

    NASA Astrophysics Data System (ADS)

    Ko, J.; Chung, J.

    2017-06-01

    The safety factor profile evolutions have been measured from the plasma discharges with the external current drive mechanism such as the multi-ion-source neutral beam injection for the Korea Superconducting Tokamak Advanced Research (KSTAR) for the first time. This measurement has been possible by the newly installed motional Stark effect (MSE) diagnostic system that utilizes the polarized Balmer-alpha emission from the energetic neutral deuterium atoms induced by the Stark effect under the Lorentz electric field. The 25-channel KSTAR MSE diagnostic is based on the conventional photoelastic modulator approach with the spatial and temporal resolutions less than 2 cm (for the most of the channels except 2 to 3 channels inside the magnetic axis) and about 10 ms, respectively. The strong Faraday rotation imposed on the optical elements in the diagnostic system is calibrated out from a separate and well-designed polarization measurement procedure using an in-vessel reference polarizer during the toroidal-field ramp-up phase before the plasma experiment starts. The combination of the non-inductive current drive during the ramp-up and shape control enables the formation of the internal transport barrier where the pitch angle profiles indicate flat or slightly hollow profiles in the safety factor.

  3. Development of ITER non-activation phase operation scenarios

    DOE PAGES

    Kim, S. H.; Poli, F. M.; Koechl, F.; ...

    2017-06-29

    Non-activation phase operations in ITER in hydrogen (H) and helium (He) will be important for commissioning of tokamak systems, such as diagnostics, heating and current drive (HCD) systems, coils and plasma control systems, and for validation of techniques necessary for establishing operations in DT. The assessment of feasible HCD schemes at various toroidal fields (2.65–5.3 T) has revealed that the previously applied assumptions need to be refined for the ITER non-activation phase H/He operations. A study of the ranges of plasma density and profile shape using the JINTRAC suite of codes has indicated that the hydrogen pellet fuelling into Hemore » plasmas should be utilized taking the optimization of IC power absorption, neutral beam shine-through density limit and H-mode access into account. The EPED1 estimation of the edge pedestal parameters has been extended to various H operation conditions, and the combined EPED1 and SOLPS estimation has provided guidance for modelling the edge pedestal in H/He operations. The availability of ITER HCD schemes, ranges of achievable plasma density and profile shape, and estimation of the edge pedestal parameters for H/He plasmas have been integrated into various time-dependent tokamak discharge simulations. In this paper, various H/He scenarios at a wide range of plasma current (7.5–15 MA) and field (2.65–5.3 T) have been developed for the ITER non-activation phase operation, and the sensitivity of the developed scenarios to the used assumptions has been investigated to provide guidance for further development.« less

  4. Development of ITER non-activation phase operation scenarios

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kim, S. H.; Poli, F. M.; Koechl, F.

    Non-activation phase operations in ITER in hydrogen (H) and helium (He) will be important for commissioning of tokamak systems, such as diagnostics, heating and current drive (HCD) systems, coils and plasma control systems, and for validation of techniques necessary for establishing operations in DT. The assessment of feasible HCD schemes at various toroidal fields (2.65–5.3 T) has revealed that the previously applied assumptions need to be refined for the ITER non-activation phase H/He operations. A study of the ranges of plasma density and profile shape using the JINTRAC suite of codes has indicated that the hydrogen pellet fuelling into Hemore » plasmas should be utilized taking the optimization of IC power absorption, neutral beam shine-through density limit and H-mode access into account. The EPED1 estimation of the edge pedestal parameters has been extended to various H operation conditions, and the combined EPED1 and SOLPS estimation has provided guidance for modelling the edge pedestal in H/He operations. The availability of ITER HCD schemes, ranges of achievable plasma density and profile shape, and estimation of the edge pedestal parameters for H/He plasmas have been integrated into various time-dependent tokamak discharge simulations. In this paper, various H/He scenarios at a wide range of plasma current (7.5–15 MA) and field (2.65–5.3 T) have been developed for the ITER non-activation phase operation, and the sensitivity of the developed scenarios to the used assumptions has been investigated to provide guidance for further development.« less

  5. Real-time MSE measurements for current profile control on KSTAR.

    PubMed

    De Bock, M F M; Aussems, D; Huijgen, R; Scheffer, M; Chung, J

    2012-10-01

    To step up from current day fusion experiments to power producing fusion reactors, it is necessary to control long pulse, burning plasmas. Stability and confinement properties of tokamak fusion reactors are determined by the current or q profile. In order to control the q profile, it is necessary to measure it in real-time. A real-time motional Stark effect diagnostic is being developed at Korean Superconducting Tokamak for Advanced Research for this purpose. This paper focuses on 3 topics important for real-time measurements: minimize the use of ad hoc parameters, minimize external influences and a robust and fast analysis algorithm. Specifically, we have looked into extracting the retardance of the photo-elastic modulators from the signal itself, minimizing the influence of overlapping beam spectra by optimizing the optical filter design and a multi-channel, multiharmonic phase locking algorithm.

  6. Noninductive RF startup in CDX-U

    NASA Astrophysics Data System (ADS)

    Jones, B.; Majeski, R.; Efthimion, P.; Kaita, R.; Menard, J.; Munsat, T.; Takase, Y.

    1998-11-01

    For the spherical torus (ST) to prove viable as a reactor, it will be necessary to devise techniques for noninductive plasma startup. Initial studies of noninductive plasma initiation have been performed on CDX-U, using the 100 kW high harmonic fast wave (HHFW) system in combination with the 1 kW 2.45 GHz electron cyclotron heating system used for breakdown. Modest density (ne ~ 10^12 cm-3), low temperature (5 eV) plasmas were formed, but the density profile was peaked far off-axis, very near the HHFW antenna. High neutral fill pressures were also required. In upcoming experiments, up to 500 kW of low frequency RF power will utilized for heating and noninductive current drive in the mode conversion regime in a target noninductive plasma formed by a combination of 5.6 and 14 GHz ECH (40 kW total). Modeling will be presented which indicates that startup to plasma currents of 60 kA is feasible with this system.

  7. Non-axisymmetric equilibrium reconstruction on the Compact Toroidal Hybrid Experiment using external magnetic and soft x-ray inversion radius measurements

    NASA Astrophysics Data System (ADS)

    Ma, X.; Cianciosa, M.; Hanson, J. D.; Hartwell, G. J.; Knowlton, S. F.; Maurer, D. A.; Ennis, D. A.; Herfindal, J. L.

    2015-11-01

    Non-axisymmetric free-boundary equilibrium reconstructions of stellarator plasmas are performed for discharges in which the magnetic configuration is strongly modified by the driven plasma current. Studies were performed on the Compact Toroidal Hybrid device using the V3FIT reconstruction code incorporating a set of 50 magnetic diagnostics external to the plasma, combined with information from soft X-ray (SXR) arrays. With the assumption of closed magnetic flux surfaces, the reconstructions using external magnetic measurements allow accurate estimates of the net toroidal flux within the last closed flux surface, the edge safety factor, and the outer boundary of these highly non-axisymmetric plasmas. The inversion radius for sawtoothing plasmas is used to identify the location of the q = 1 surface, and thus infer the current profile near the magnetic axis. With external magnetic diagnostics alone, we find the reconstruction to be insufficiently constrained. This work is supported by US Department of Energy Grant No. DE-FG02-00ER54610.

  8. Magnetic Effects in a Moderate-Temperature, High-Beta, Toroidal Plasma Device

    NASA Astrophysics Data System (ADS)

    Edwards, W. F.; Singh, A. K.; Held, E. D.

    2011-10-01

    A small toroidal machine (STOR-1M; minor radius 4.5 cm), on loan from the University of Saskatchewan, has been modified to operate at hydrogen ionization levels ~0.1%, beta values between 0.1 and 1, electron number density ~5x1016/m3, temperature ~5 eV, and applied toroidal magnetic field ~20 gauss. Plasma is generated using magnetron-produced microwaves. Langmuir and Hall probes determine radial profiles of electron number density, temperature, and magnetic field. For most values of the externally-applied magnetic field, the internal field is the same with or without plasma, however, in a narrow window of B, diamagnetism and other effects are present. The effect is observed with no externally induced current; plasma currents are self generated through some sort of relaxation process. Beta and radius conditions correlate well with similar magnetic structures in the laboratory (eg., plasma focus, Z pinch) and in space (eg., Venus flux ropes, solar coronal loops).

  9. Fast wave experiments in LAPD: RF sheaths, convective cells and density modifications

    NASA Astrophysics Data System (ADS)

    Carter, T. A.; van Compernolle, B.; Martin, M.; Gekelman, W.; Pribyl, P.; van Eester, D.; Crombe, K.; Perkins, R.; Lau, C.; Martin, E.; Caughman, J.; Tripathi, S. K. P.; Vincena, S.

    2017-10-01

    An overview is presented of recent work on ICRF physics at the Large Plasma Device (LAPD) at UCLA. The LAPD has typical plasma parameters ne 1012 -1013 cm-3, Te 1 - 10 eV and B 1000 G. A new high-power ( 150 kW) RF system and fast wave antenna have been developed for LAPD. The source runs at a frequency of 2.4 MHz, corresponding to 1 - 7fci , depending on plasma parameters. Evidence of rectified RF sheaths is seen in large increases ( 10Te) in the plasma potential on field lines connected to the antenna. The rectified potential scales linearly with antenna current. The rectified RF sheaths set up convective cells of local E × B flows, measured indirectly by potential measurements, and measured directly with Mach probes. At high antenna powers substantial modifications of the density profile were observed. The plasma density profile initially exhibits transient low frequency oscillations (10 kHz). The amplitude of the fast wave fields in the core plasma is modulated at the same low frequency, suggesting fast wave coupling is affected by the density rearrangement. Work performed at the Basic Plasma Science Facility, supported jointly by the National Science Foundation and the Department of Energy.

  10. Comparative studies of three cholesteryl ester transfer proteins and their interactions with known inhibitors

    PubMed Central

    Wang, Ziyun; Niimi, Manabu; Ding, Qianzhi; Liu, Zhenming; Wang, Ling; Zhang, Jifeng; Xu, Jun

    2017-01-01

    Cholesteryl ester transfer protein (CETP) is a plasma protein that mediates bidirectional transfers of cholesteryl esters and triglycerides between low-density lipoproteins and high-density lipoproteins (HDL). Because low levels of plasma CETP are associated with increased plasma HDL-cholesterol, therapeutic inhibition of CETP activity is considered an attractive strategy for elevating plasma HDL-cholesterol, thereby hoping to reduce the risk of cardiovascular disease. Interestingly, only a few laboratory animals, such as rabbits, guinea pigs, and hamsters, have plasma CETP activity, whereas mice and rats do not. It is not known whether all CETPs in these laboratory animals are functionally similar to human CETP. In the current study, we compared plasma CETP activity and characterized the plasma lipoprotein profiles of these animals. Furthermore, we studied the three CETP molecular structures, physicochemical characteristics, and binding properties with known CETP inhibitors in silico. Our results showed that rabbits exhibited higher CETP activity than guinea pigs and hamsters, while these animals had different lipoprotein profiles. CETP inhibitors can inhibit rabbit and hamster CETP activity in a similar manner to human CETP. Analysis of CETP molecules in silico revealed that rabbit and hamster CETP showed many features that are similar to human CETP. These results provide novel insights into understanding CETP functions and molecular properties. PMID:28767652

  11. Transport and Performance in DIII--D Discharges with Weak or Negative Central Magnetic Shear

    NASA Astrophysics Data System (ADS)

    Greenfield, C. M.

    1996-11-01

    The previously reported [B.W. Rice et al., Phys. Plasmas 3, 1983 (1996)] improved performance in DIII-D plasmas with weak or negative central magnetic shear has been additionally enhanced in recent experiments where controlled L-H transitions were used to further broaden the pressure profile and delay detrimental MHD activity [E.A. Lazarus et al., submitted to Phys. Rev. Letters]. These discharges exhibit the highest plasma energy (>=4 MJ) and fusion reactivity (R_DD <= 4.8 × 10^16 s-1, Q_DD <= 0.00146, equivalent Q_DT <= 0.32) yet realized in DIII-D. In such discharges, the core magnetic shear is reversed by tailoring the current profile through application of early, low power, neutral beam injection. These plasmas often undergo a transition to a high performance state, usually following an increase in the applied heating power. At the transition time, we observe the formation of an internal transport barrier near the location of the minimum safety factor, q_min. Formation of this barrier, which can result in central peaking of the temperature and density profiles, is consistent with suppression of turbulence by locally enhanced E×B flow shear. Beam emission spectroscopy and far infrared scattering measurements made in the vicinity of the barrier show that at the time of transition to high performance, fluctuation levels are reduced to below the threshold of detection (tilden/n <= 0.1%). Analysis with the ONETWO and TRANSP transport codes indicates concomitant reductions in the core ion thermal diffusivity to levels at or below Chang-Hinton neoclassical. Smaller reductions are indicated for the electrons. An L-H transition is programmed shortly before the plasma would become MHD unstable in order to broaden the profiles and delay the onset of instabilities. In the resulting state, the region exhibiting ion diffusivities at or below neoclassical is extended to nearly the entire plasma. Analysis to date suggests that the effect of strongly negative vs. weak magnetic shear on transport is negligible, although there is a significant effect on stability. A comparison of transport in strong and weakly sheared discharges will be shown, both in L- (peaked profiles) and H-mode (broadened profiles).

  12. Understanding the stability of the low torque ITER Baseline Scenario in DIII-D

    NASA Astrophysics Data System (ADS)

    Turco, Francesca

    2017-10-01

    Analysis of the evolving current density (J), pedestal and rotation profiles in a database of 200 ITER Baseline Scenario discharges in the DIII-D tokamak sheds light on the cause of the disruptive instability limiting both high and low torque operation of these plasmas. The m =2/n =1 tearing modes, occurring after several pressure-relaxation times, are related to the shape of the current profile in the outer region of the plasma. The q =2 surface is located just inside the current pedestal, near a minimum in J. This well in J deepens at constant betaN and at lower rotation, causing the equilibrium to evolve towards a classically unstable state. Lack of core-edge differential rotation likely biases the marginal point towards instability during the secular trend in J. New results from the 2017 experimental campaign establish the first reproducible, stable operation at T =0 Nm for this scenario. A new ramp-up recipe with delayed heating keeps the discharges stable without the need for ECCD stabilization. The J profile shape in the new shots is consistent with an expansion of the previous ``shallow well'' stable operational space. Realtime Active MHD Spectroscopy (AMS) has been applied to IBS plasmas for the first time, and the plasma response measurements show that the AMS can help sense the approach to instability during the discharges. The AMS data shows the trend towards instability at low rotation, and MARS-K modelling partially reproduces the experimental trend if collisionality and resistivity are included. The modelling results are sensitive to the edge resistivity, and this can indicate that the AMS is measuring the changes in ideal (kink) stability, to which the tearing stability index delta' is correlated. Together these results constitute a crucial step to acquire physical understanding and sensing capability for the MHD stability in the Q =10 ITER scenario. Work supported by US DOE under DE-FC02-04ER54698 and DE-FG02-04ER54761.

  13. An Overview of NSTX Research Facility and Recent Experimental Results

    NASA Astrophysics Data System (ADS)

    Ono, Masayuki

    2006-10-01

    The 2006 NSTX experimental campaign yielded significant new experimental results in many areas. Improved plasma control achieved the highest elongation of 2.9 and plasma shape factor q95Ip/aBT = 42 MA/m.T. Active feedback correction of error fields sustained the plasma rotation and increased the pulse length of high beta discharges. Active feedback stabilization of the resistive wall mode in high-beta, low-rotation plasmas was demonstrated for ˜100 resistive wall times. Operation at higher toroidal field showed favorable plasma confinement and HHFW heating efficiency trends with the field. A broader current profile, measured by the 12-channel MSE diagnostic in high beta discharges revealed an outward anomalous diffusivity of energetic ions due to the n=1 MHD modes. A tangential microwave scattering diagnostic measured localized electron gyro-scale fluctuations in L-mode, H-mode and reversed-shear plasmas. Evaporation of lithium onto plasma facing surfaces yielded lower density, higher temperature and improved confinement. A strong dependence of the divertor heat load and ELM behavior on the plasma triangularity was observed. Coaxial helicity injection produced a start-up current of 160 kA on closed flux surfaces.

  14. Comparison of Measurement And Modeling Of Current Profile Changes Due To Neutral Bean Ion Redistribution During TAE Avalanches in NSTX

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Darrow, Douglas

    Brief "avalanches" of toroidal Alfven eigenmodes (TAEs) are observed in NSTX plasmas with several different n numbers simultaneously present. These affect the neutral beam ion distribution as evidenced by a concurrent drop in the neutron rate and, sometimes, beam ion loss. Guiding center orbit modeling has shown that the modes can transiently render portions of the beam ion phase space stochastic. The resulting redistribution of beam ions can also create a broader beam-driven current profile and produce other changes in the beam ion distribution function

  15. Continuous, edge localized ion heating during non-solenoidal plasma startup and sustainment in a low aspect ratio tokamak

    NASA Astrophysics Data System (ADS)

    Burke, M. G.; Barr, J. L.; Bongard, M. W.; Fonck, R. J.; Hinson, E. T.; Perry, J. M.; Reusch, J. A.; Schlossberg, D. J.

    2017-07-01

    Plasmas in the Pegasus spherical tokamak are initiated and grown by the non-solenoidal local helicity injection (LHI) current drive technique. The LHI system consists of three adjacent electron current sources that inject multiple helical current filaments that can reconnect with each other. Anomalously high impurity ion temperatures are observed during LHI with T i,OV  ⩽  650 eV, which is in contrast to T i,OV  ⩽  70 eV from Ohmic heating alone. Spatial profiles of T i,OV indicate an edge localized heating source, with T i,OV ~ 650 eV near the outboard major radius of the injectors and dropping to ~150 eV near the plasma magnetic axis. Experiments without a background tokamak plasma indicate the ion heating results from magnetic reconnection between adjacent injected current filaments. In these experiments, the HeII T i perpendicular to the magnetic field is found to scale with the reconnecting field strength, local density, and guide field, while {{T}\\text{i,\\parallel}} experiences little change, in agreement with two-fluid reconnection theory. This ion heating is not expected to significantly impact the LHI plasma performance in Pegasus, as it does not contribute significantly to the electron heating. However, estimates of the power transfer to the bulk ion are quite large, and thus LHI current drive provides an auxiliary ion heating mechanism to the tokamak plasma.

  16. Continuous, edge localized ion heating during non-solenoidal plasma startup and sustainment in a low aspect ratio tokamak

    DOE PAGES

    Burke, Marcus G.; Barr, Jayson L.; Bongard, Michael W.; ...

    2017-05-16

    Plasmas in the Pegasus spherical tokamak are initiated and grown by the non-solenoidal local helicity injection (LHI) current drive technique. The LHI system consists of three adjacent electron current sources that inject multiple helical current filaments that can reconnect with each other. Anomalously high impurity ion temperatures are observed during LHI with T i,OV ≤ 650 eV, which is in contrast to T i,OV ≤ 70 eV from Ohmic heating alone. Spatial profiles of T i,OV indicate an edge localized heating source, with T i,OV ~ 650 eV near the outboard major radius of the injectors and dropping to ~150 eV near the plasma magnetic axis. Experiments without a background tokamak plasma indicate the ion heating results from magnetic reconnection between adjacent injected current filaments. In these experiments, the HeII T i perpendicular to the magnetic field is found to scale with the reconnecting field strength, local density, and guide field, whilemore » $${{T}_{\\text{i},\\parallel}}$$ experiences little change, in agreement with two-fluid reconnection theory. In conclusion, this ion heating is not expected to significantly impact the LHI plasma performance in Pegasus, as it does not contribute significantly to the electron heating. However, estimates of the power transfer to the bulk ion are quite large, and thus LHI current drive provides an auxiliary ion heating mechanism to the tokamak plasma.« less

  17. Optimized ECR plasma apparatus with varied microwave window thickness

    DOEpatents

    Berry, Lee A.

    1995-01-01

    The present invention describes a technique to control the radial profile of microwave power in an ECR plasma discharge. In order to provide for a uniform plasma density to a specimen, uniform energy absorption by the plasma is desired. By controlling the radial profile of the microwave power transmitted through the microwave window of a reactor, the profile of the transmitted energy to the plasma can be controlled in order to have uniform energy absorption by the plasma. An advantage of controlling the profile using the window transmission characteristics is that variations to the radial profile of microwave power can be made without changing the microwave coupler or reactor design.

  18. High energy density Z-pinch plasmas using flow stabilization

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shumlak, U., E-mail: shumlak@uw.edu; Golingo, R. P., E-mail: shumlak@uw.edu; Nelson, B. A., E-mail: shumlak@uw.edu

    The ZaP Flow Z-Pinch research project[1] at the University of Washington investigates the effect of sheared flows on MHD instabilities. Axially flowing Z-pinch plasmas are produced that are 100 cm long with a 1 cm radius. The plasma remains quiescent for many radial Alfvén times and axial flow times. The quiescent periods are characterized by low magnetic mode activity measured at several locations along the plasma column and by stationary visible plasma emission. Plasma evolution is modeled with high-resolution simulation codes – Mach2, WARPX, NIMROD, and HiFi. Plasma flow profiles are experimentally measured with a multi-chord ion Doppler spectrometer. Amore » sheared flow profile is observed to be coincident with the quiescent period, and is consistent with classical plasma viscosity. Equilibrium is determined by diagnostic measurements: interferometry for density; spectroscopy for ion temperature, plasma flow, and density[2]; Thomson scattering for electron temperature; Zeeman splitting for internal magnetic field measurements[3]; and fast framing photography for global structure. Wall stabilization has been investigated computationally and experimentally by removing 70% of the surrounding conducting wall to demonstrate no change in stability behavior.[4] Experimental evidence suggests that the plasma lifetime is only limited by plasma supply and current waveform. The flow Z-pinch concept provides an approach to achieve high energy density plasmas,[5] which are large, easy to diagnose, and persist for extended durations. A new experiment, ZaP-HD, has been built to investigate this approach by separating the flow Z-pinch formation from the radial compression using a triaxial-electrode configuration. This innovation allows more detailed investigations of the sheared flow stabilizing effect, and it allows compression to much higher densities than previously achieved on ZaP by reducing the linear density and increasing the pinch current. Experimental results and scaling analyses will be presented. In addition to studying fundamental plasma science and high energy density physics, the ZaP and ZaP-HD experiments can be applied to laboratory astrophysics.« less

  19. Space-plasma campaign on UCLA's Large Plasma Device (LAPD)

    NASA Astrophysics Data System (ADS)

    Koepke, M. E.; Finnegan, S. M.; Knudsen, D. J.; Vincena, S.

    2007-05-01

    Knudsen [JGR, 1996] describes a potential role for stationary Alfvén (StA) waves in auroral arcs' frequency dependence. Magnetized plasmas are predicted to support electromagnetic perturbations that are static in a fixed frame if there is uniform background plasma convection. These stationary waves should not be confused with standing waves that oscillate in time with a fixed, spatially varying envelope. Stationary waves have no time variation in the fixed frame. In the drifting frame, there is an apparent time dependence as plasma convects past fixed electromagnetic structures. We describe early results from an experimental campaign to reproduce in the lab the basic conditions necessary for the creation of StA waves, namely quasi-steady-state convection across magnetic field-aligned current channels. We show that an off-axis, fixed channel of electron current (and depleted density) is created in the Large Plasma Device Upgrade (LAPD) at UCLA, using a small, heated, oxide-coated electrode at one plasma-column end and we show that the larger plasma column rotates about its cylindrical axis from a radial electric field imposed by a special termination electrode on the same end. Initial experimentation with plasma-rotation-inducing termination electrodes began in May 2006 in the West Virginia Q Machine, leading to two designs that, in January 2007, were tested in LAPD. The radial profile of azimuthal velocity was consistent with predictions of rigid-body rotation. Current-channel experiments in LAPD, in August 2006, showed that inertial Alfvén waves could be concentrated in an off-axis channel of electron current and depleted plasma density. These experimental results will be presented and discussed. This research is supported by DOE and NSF.

  20. Assessment of quasi-linear effect of RF power spectrum for enabling lower hybrid current drive in reactor plasmas

    NASA Astrophysics Data System (ADS)

    Cesario, Roberto; Cardinali, Alessandro; Castaldo, Carmine; Amicucci, Luca; Ceccuzzi, Silvio; Galli, Alessandro; Napoli, Francesco; Panaccione, Luigi; Santini, Franco; Schettini, Giuseppe; Tuccillo, Angelo Antonio

    2017-10-01

    The main research on the energy from thermonuclear fusion uses deuterium plasmas magnetically trapped in toroidal devices. To suppress the turbulent eddies that impair thermal insulation and pressure tight of the plasma, current drive (CD) is necessary, but tools envisaged so far are unable accomplishing this task while efficiently and flexibly matching the natural current profiles self-generated at large radii of the plasma column [1-5]. The lower hybrid current drive (LHCD) [6] can satisfy this important need of a reactor [1], but the LHCD system has been unexpectedly mothballed on JET. The problematic extrapolation of the LHCD tool at reactor graded high values of, respectively, density and temperatures of plasma has been now solved. The high density problem is solved by the FTU (Frascati Tokamak Upgrade) method [7], and solution of the high temperature one is presented here. Model results based on quasi-linear (QL) theory evidence the capability, w.r.t linear theory, of suitable operating parameters of reducing the wave damping in hot reactor plasmas. Namely, using higher RF power densities [8], or a narrower antenna power spectrum in refractive index [9,10], the obstacle for LHCD represented by too high temperature of reactor plasmas should be overcome. The former method cannot be used for routinely, safe antenna operations, Thus, only the latter key is really exploitable in a reactor. The proposed solutions are ultimately necessary for viability of an economic reactor.

  1. Observations of Rotation Reversal and Fluctuation Hysteresis in Alcator C-Mod L-Mode Plasmas

    NASA Astrophysics Data System (ADS)

    Cao, N. M.; Rice, J. E.; White, A. E.; Baek, S. G.; Creely, A. J.; Ennever, P. C.; Hubbard, A. E.; Hughes, J. W.; Irby, J.; Rodriguez-Fernandez, P.; Chilenski, M. A.; Diamond, P. H.; Reinke, M. L.; Alcator C-Mod Team

    2017-10-01

    Intrinsic core toroidal rotation in Alcator C-Mod L-mode plasmas has been observed to spontaneously reverse direction when the minimum value of the normalized collisionality ν*, crosses around 0.4. In Ohmic plasmas, the rotation is co-current in the low density linear Ohmic confinement (LOC) regime and counter-current in the higher density saturated Ohmic confinement (SOC) regime. The reversal manifests a hysteresis loop in ν*, where the critical collisionalities for the forward and reverse transitions differ by 10-15%. Temperature and density profiles of the two rotation states are observed to be indistinguishable to within experimental error estimated with Gaussian process regression. However, qualitative differences between the two rotation states are observed in fluctuation spectra, including the broadening of reflectometry spectra and, under certain conditions, the appearance of high-k features in phase contrast imaging (PCI) spectra (kθρs up to 1). These results suggest that the turbulent state can decouple from local profiles, and that turbulent self-regulation may play a role in the LOC/SOC transition. This work is supported by the US DOE under Grant DE-FC02-99ER54512 (C-Mod).

  2. Characterizing the plasma of the Rotating Wall Machine

    NASA Astrophysics Data System (ADS)

    Hannum, David A.

    The Rotating Wall Machine (RoWM) is a line-tied linear screw pinch built to study current-driven external kink modes. The plasma column is formed by an array of seven electrostatic washer guns which can also be biased to drive plasma current. The array allows independent control over the electron density ne and current density Jz profiles of the column. Internal measurements of the plasma have been made with singletip Langmuir and magnetic induction ("B-dot") probes for a range of bias currents (Ib = 0, 300, 500 A/gun). Streams from the individual guns are seen to merge at a distance of z ≈ 36 cm from the guns; the exact distance depends on the value of Ib. The density of the column is directly proportional to the Ohmic dissipation power, but the temperature stays at a low, uniform value (Te ≈ 3.5 eV) for each bias level. Electron densities are on the order of ne ˜10 20 m-3. The electron density expands radially (across the Bz guide field) as the plasma moves along the column, though the current density Jz mainly stays parallel to the field lines. The singletip Langmuir probe diagnostic is difficult to analyze for Ib = 500 A/gun plasmas and fails as Ib is raised beyond this level. Spectrographic analysis of the Halpha line indicates that the hydrogen plasmas are nearly fully ionized at each bias level. Azimuthal E x B rotation is axially and radially sheared; rotation slows as the plasma reaches the anode. Perpendicular diffusivity is consistent with the classical value, D⊥ ≈ 5 m2/sec, while parallel resistivity is seen to be twice the classical Spitzer value, 2 x 10-4 O m.

  3. Overview of ASDEX Upgrade results

    NASA Astrophysics Data System (ADS)

    A. Kallenbachthe ASDEX Upgrade Team; the EUROfusion MST1 Team

    2017-10-01

    The ASDEX Upgrade (AUG) programme is directed towards physics input to critical elements of the ITER design and the preparation of ITER operation, as well as addressing physics issues for a future DEMO design. Since 2015, AUG is equipped with a new pair of 3-strap ICRF antennas, which were designed for a reduction of tungsten release during ICRF operation. As predicted, a factor two reduction on the ICRF-induced W plasma content could be achieved by the reduction of the sheath voltage at the antenna limiters via the compensation of the image currents of the central and side straps in the antenna frame. There are two main operational scenario lines in AUG. Experiments with low collisionality, which comprise current drive, ELM mitigation/suppression and fast ion physics, are mainly done with freshly boronized walls to reduce the tungsten influx at these high edge temperature conditions. Full ELM suppression and non-inductive operation up to a plasma current of {{I}\\text{p}}=0.8 MA could be obtained at low plasma density. Plasma exhaust is studied under conditions of high neutral divertor pressure and separatrix electron density, where a fresh boronization is not required. Substantial progress could be achieved for the understanding of the confinement degradation by strong D puffing and the improvement with nitrogen or carbon seeding. Inward/outward shifts of the electron density profile relative to the temperature profile effect the edge stability via the pressure profile changes and lead to improved/decreased pedestal performance. Seeding and D gas puffing are found to effect the core fueling via changes in a region of high density on the high field side (HFSHD). The integration of all above mentioned operational scenarios will be feasible and naturally obtained in a large device where the edge is more opaque for neutrals and higher plasma temperatures provide a lower collisionality. The combination of exhaust control with pellet fueling has been successfully demonstrated. High divertor enrichment values of nitrogen {{E}\\text{N}}≥slant 10 have been obtained during pellet injection, which is a prerequisite for the simultaneous achievement of good core plasma purity and high divertor radiation levels. Impurity accumulation observed in the all-metal AUG device caused by the strong neoclassical inward transport of tungsten in the pedestal is expected to be relieved by the higher neoclassical temperature screening in larger devices.

  4. Identity physics experiment on internal transport barriers in JT-60U and JET

    NASA Astrophysics Data System (ADS)

    de Vries, P. C.; Sakamoto, Y.; Litaudon, X.; Beurskens, M. N. A.; Brix, M.; Crombé, K.; Fujita, T.; Giroud, C.; Hawkes, N. C.; Hayashi, N.; Joffrin, E.; Mantica, P.; Matsunaga, G.; Oyama, N.; Parail, V.; Salmi, A.; Shinohara, K.; Strintzi, D.; Suzuki, T.; Takechi, M.; Takenaga, H.; Tala, T.; Tsalas, M.; Urano, H.; Voitsekhovitch, I.; Yoshida, M.; EFDA contributors, JET; JT-60 Team

    2009-12-01

    A series of experiments have been carried out in 2008 at JT-60U and JET to find common characteristics and explain differences between internal transport barriers (ITBs). The identity experiments succeeded in matching the profiles of most dimensionless parameters at the time ITBs were triggered. Thereafter the q-profile development deviated due to differences in non-inductive current density profile, affecting the ITB. Furthermore, the ITBs in JET were more strongly influenced by the H-mode pedestal or edge localized modes. It was found to be difficult to match the plasma rotation characteristics in both devices. However, the wide range of Mach numbers obtained in these experiments shows that the rotation has little effect on the triggering of ITBs in plasmas with reversed magnetic shear. On the other hand the toroidal rotation and more specifically the rotational shear had an impact on the subsequent growth and allowed the formation of strong ITBs.

  5. Onset of magnetic reconnection in a weakly collisional, high- β plasma

    NASA Astrophysics Data System (ADS)

    Alt, Andrew; Kunz, Matthew

    2017-10-01

    In a magnetized, weakly collisional plasma, the magnetic moment of the constituent particles is an adiabatic invariant. An increase of the magnetic-field strength in such a plasma thus leads to an increase in the thermal pressure perpendicular to the field lines. Above a β-dependent threshold, this pressure anisotropy drives the mirror instability, which produces strong distortions in the field lines and traps particles on ion-Larmor scales. The impact of this instability on magnetic reconnection is investigated using simple analytical and numerical models for the formation of a current sheet and the associated production of pressure anisotropy. The difficulty in maintaining an isotropic, Maxwellian particle distribution during the formation and subsequent thinning of a current sheet in a weakly collisional plasma, coupled with the low threshold for the mirror instability in a high- β plasma, imply that the topology of reconnecting magnetic fields can radically differ from the standard Harris-sheet profile often used in kinetic simulations of collisionless reconnection. Depending on the rate of current-sheet formation, this mirror-induced disruption may occur before standard tearing modes are able to develop. This work was supported by U.S. DOE contract DE-AC02-09CH11466.

  6. HIGH-THROUGHPUT CHEMICAL SCREENING USING PROTEIN PROFILING OF FISH PLASMA

    EPA Science Inventory

    Compounds that affect the hormone system, referred to as "endocrine-disrupting chemicals" (EDCs), cause human and animal health problems. It is necessary to test putative EDC chemicals for such deleterious effects, though current testing methodologies are time/animal intensive an...

  7. Progress In Plasma Accelerator Development for Dynamic Formation of Plasma Liners

    NASA Technical Reports Server (NTRS)

    Thio, Y. C. Francis; Eskridge, Richard; Martin, Adam; Smith, James; Lee, Michael; Cassibry, Jason T.; Griffin, Steven; Rodgers, Stephen L. (Technical Monitor)

    2002-01-01

    An experimental plasma accelerator for magnetic target fusion (MTF) applications under development at the NASA Marshall Space Flight Center is described. The accelerator is a coaxial pulsed plasma thruster (Figure 1). It has been tested experimentally and plasma jet velocities of approx.50 km/sec have been obtained. The plasma jet has been photographed with 10-ns exposure times to reveal a stable and repeatable plasma structure (Figure 2). Data for velocity profile information has been obtained using light pipes and magnetic probes embedded in the gun walls to record the plasma and current transit respectively at various barrel locations. Preliminary spatially resolved spectral data and magnetic field probe data are also presented. A high speed triggering system has been developed and tested as a means of reducing the gun "jitter". This jitter is being characterized and future work for second generation "ultra-low jitter" gun development is being identified.

  8. Observation of plasma rotation driven by static nonaxisymmetric magnetic fields in a tokamak.

    PubMed

    Garofalo, A M; Burrell, K H; DeBoo, J C; deGrassie, J S; Jackson, G L; Lanctot, M; Reimerdes, H; Schaffer, M J; Solomon, W M; Strait, E J

    2008-11-07

    We present the first evidence for the existence of a neoclassical toroidal rotation driven in a direction counter to the plasma current by nonaxisymmetric, nonresonant magnetic fields. At high beta and with large injected neutral beam momentum, the nonresonant field torque slows down the plasma toward the neoclassical "offset" rotation rate. With small injected neutral beam momentum, the toroidal rotation is accelerated toward the offset rotation, with resulting improvement in the global energy confinement time. The observed magnitude, direction, and radial profile of the offset rotation are consistent with neoclassical theory predictions.

  9. Broadband sidebands generated by parametric instability in lower hybrid current drive experiments on EAST

    NASA Astrophysics Data System (ADS)

    Amicucci, L.; Ding, B. J.; Castaldo, C.; Cesario, R.; Giovannozzi, E.; Li, M. H.; Tuccillo, A. A.

    2015-12-01

    Modern research on nuclear fusion energy, based on the tokamak concept, has strong need of tools for actively driving non-inductive current especially at the periphery of plasma column, where tools available so far have poor efficiency. This is essential for solving one of the most critical problems for thermonuclear reactor, consisting in how to achieve the figure of fusion gain in the context of sufficient stability. The lower hybrid current drive (LHCD) effect has the potential capability of driving current at large radii of reactor plasma with high efficiency [1]. Experiments recently carried out on EAST showed that a strong activity of LH sideband waves (from the RF probe spectra), accompanied by weak core penetration of the coupled LH power, is present when operating at relatively high plasma densities. Previous theoretical results, confirmed by experiments on FTU, showed that the LH sideband phenomenon is produced by parametric instability (PI), which are mitigated by higher plasma edge temperatures. This condition is thus useful for enabling the LH power propagation when operating with profiles having high plasma densities even at the edge. In the present work, we show new PI modeling of EAST plasmas data, obtained in condition of higher plasma edge temperature due to chamber lithisation. The obtained trend of the PI frequencies and growth rates is consistent with data of RF probe spectra, available in different regimes of lithisated and not lithisated vessel. Moreover, these spectra are interpreted as PI effect occurring at the periphery of plasma column, however in the low field side where the LH power is coupled.

  10. Analysis of Ignitor Discharges with Double X-point Magnetic Configurations

    NASA Astrophysics Data System (ADS)

    Airoldi, A.; Cenacchi, G.; Coppi, B.

    2008-11-01

    The Ignitor experiment was proposed and designed to achieve ignited and sub-ignited conditions in well confined deuterium-tritium plasmas. Thanks to its unique features (high magnetic field up to 13 T, high plasma current up to 11 MA, and high plasma density up to 5 x10^20 m-3), Ignitor is the only device capable of exploring plasma regimes that are relevant to a net power producing D-T reactor and are not accessible to other existing or planned machines. Double X-point scenarios with magnetic field up to 13 T and plasma current up to 9 MA are analyzed. In these configurations, the access to a high confinement state is assumed when the available plasma heating power, supported by the injected auxiliary power, is larger than the L-H threshold value, according to recent suggested scalings The H-regime is modeled by a global reduction of the thermal transport coefficients used for the L-regime. Situations in the presence and in the absence of sawtooth oscillations have been investigated. Quasi-stationary conditions can be attained when a process producing re- distribution of pressure and current profiles is active. B.Coppi, A.Airoldi, F.Bombarda, et al.,Nucl. Fusion 41, 1253 (2001) D.C. McDonald, A.J. Meakins, et al., PPCF 48, A439 (2006).

  11. Calculation of Eddy Currents In the CTH Vacuum Vessel and Coil Frame

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    A. Zolfaghari, A. Brooks, A. Michaels, J. Hanson, and G. Hartwell

    2012-09-25

    Knowledge of eddy currents in the vacuum vessel walls and nearby conducting support structures can significantly contribute to the accuracy of Magnetohydrodynamics (MHD) equilibrium reconstruction in toroidal plasmas. Moreover, the magnetic fields produced by the eddy currents could generate error fields that may give rise to islands at rational surfaces or cause field lines to become chaotic. In the Compact Toroidal Hybrid (CTH) device (R0 = 0.75 m, a = 0.29 m, B ≤ 0.7 T), the primary driver of the eddy currents during the plasma discharge is the changing flux of the ohmic heating transformer. Electromagnetic simulations are usedmore » to calculate eddy current paths and profile in the vacuum vessel and in the coil frame pieces with known time dependent currents in the ohmic heating coils. MAXWELL and SPARK codes were used for the Electromagnetic modeling and simulation. MAXWELL code was used for detailed 3D finite-element analysis of the eddy currents in the structures. SPARK code was used to calculate the eddy currents in the structures as modeled with shell/surface elements, with each element representing a current loop. In both cases current filaments representing the eddy currents were prepared for input into VMEC code for MHD equilibrium reconstruction of the plasma discharge. __________________________________________________« less

  12. Destabilization of counter-propagating TAEs by off-axis, co-current Neutral Beam Injection

    NASA Astrophysics Data System (ADS)

    Podesta', M.; Fredrickson, E.; Gorelenkova, M.

    2017-10-01

    Neutral Beam injection (NBI) is a common tool to heat the plasma and drive current non-inductively in fusion devices. Energetic particles (EP) resulting from NBI can drive instabilities that are detrimental for the performance and the predictability of plasma discharges. A broad NBI deposition profile, e.g. by off-axis injection aiming near the plasma mid-radius, is often assumed to limit those undesired effects by reducing the radial gradient of the EP density, thus reducing the ``universal'' drive for instabilities. However, this work presents new evidence that off-axis NBI can also lead to undesired effects such as the destabilization of Alfvénic instabilities, as observed in NSTX-U plasmas. Experimental observations indicate that counter propagating toroidal AEs are destabilized as the radial EP density profile becomes hollow as a result of off-axis NBI. Time-dependent analysis with the TRANSP code, augmented by a reduced fast ion transport model (known as kick model), indicates that instabilities are driven by a combination of radial and energy gradients in the EP distribution. Understanding the mechanisms for wave-particle interaction, revealed by the phase space resolved analysis, is the basis to identify strategies to mitigate or suppress the observed instabilities. Work supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences under Contract Number DE-AC02-09CH11466.

  13. Numerical calculations of non-inductive current driven by microwaves in JET

    NASA Astrophysics Data System (ADS)

    Kirov, K. K.; Baranov, Yu; Mailloux, J.; Nave, M. F. F.; Contributors, JET

    2016-12-01

    Recent studies at JET focus on analysis of the lower hybrid (LH) wave power absorption and current drive (CD) calculations by means of a new ray tracing (RT)/Fokker-Planck (FP) package. The RT code works in real 2D geometry accounting for the plasma boundary and the launcher shape. LH waves with different parallel refractive index, {{N}\\parallel} , spectra in poloidal direction can be launched thus simulating authentic antenna spectrum with rows fed by different combinations of klystrons. Various FP solvers were tested most advanced of which is a relativistic bounce averaged FP code. LH wave power deposition profiles from the new RT/FP code were compared to the experimental results from electron cyclotron emission (ECE) analysis of pulses at 3.4 T low and high density. This kind of direct comparison between power deposition profiles from experimental ECE data and numerical model were carried out for the first time for waves in the LH range of frequencies. The results were in a reasonable agreement with experimental data at lower density, line averaged values of {{n}\\text{e}}≈ 2.4× {{10}19} {{\\text{m}}-3} . At higher density, {{n}\\text{e}}≈ 3× {{10}19} {{\\text{m}}-3} , the code predicted larger on-axis LH power deposition, which is inconsistent with the experimental observations. Both calculations were unable to produce LH wave absorption at the plasma periphery, which contradicts to the analysis of the ECE data and possible sources of these discrepancies have been briefly discussed in the paper. The code was also used to calculate the LH power deposition and CD profiles for the low-density preheat phase of JET’s advanced tokamak (AT) scenario. It was found that as the density evolves from hollow to flat and then to a more peaked profile the LH power and driven current move inward i.e. towards the plasma axis. A total driven current of about 70 kA for 1 MW of launched LH power was predicted in these conditions.

  14. ECR apparatus with magnetic coil for plasma refractive index control

    DOEpatents

    Berry, L.A.

    1994-04-26

    The present invention describes a technique to control the radial profile of microwave power in an ECR plasma discharge. In order to provide for a uniform plasma density to a specimen, uniform energy absorption by the plasma is desired. By controlling the radial profile of the microwave power transmitted through the microwave window of a reactor, the profile of the transmitted energy to the plasma can be controlled in order to have uniform energy absorption by the plasma. An advantage of controlling the profile using the window transmission characteristics is that variations to the radial profile of microwave power can be made without changing the microwave coupler or reactor design. 9 figures.

  15. ECR apparatus with magnetic coil for plasma refractive index control

    DOEpatents

    Berry, Lee A.

    1994-01-01

    The present invention describes a technique to control the radial profile of microwave power in an ECR plasma discharge. In order to provide for a uniform plasma density to a specimen, uniform energy absorption by the plasma is desired. By controlling the radial profile of the microwave power transmitted through the microwave window of a reactor, the profile of the transmitted energy to the plasma can be controlled in order to have uniform energy absorption by the plasma. An advantage of controlling the profile using the window transmission characteristics is that variations to the radial profile of microwave power can be made without changing the microwave coupler or reactor design.

  16. Optimized ECR plasma apparatus with varied microwave window thickness

    DOEpatents

    Berry, L.A.

    1995-11-14

    The present invention describes a technique to control the radial profile of microwave power in an ECR plasma discharge. In order to provide for a uniform plasma density to a specimen, uniform energy absorption by the plasma is desired. By controlling the radial profile of the microwave power transmitted through the microwave window of a reactor, the profile of the transmitted energy to the plasma can be controlled in order to have uniform energy absorption by the plasma. An advantage of controlling the profile using the window transmission characteristics is that variations to the radial profile of microwave power can be made without changing the microwave coupler or reactor design. 9 figs.

  17. Experimental and modeling uncertainties in the validation of lower hybrid current drive

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Poli, F. M.; Bonoli, P. T.; Chilenski, M.

    Our work discusses sources of uncertainty in the validation of lower hybrid wave current drive simulations against experiments, by evolving self-consistently the magnetic equilibrium and the heating and current drive profiles, calculated with a combined toroidal ray tracing code and 3D Fokker–Planck solver. The simulations indicate a complex interplay of elements, where uncertainties in the input plasma parameters, in the models and in the transport solver combine and compensate each other, at times. It is concluded that ray-tracing calculations should include a realistic representation of the density and temperature in the region between the confined plasma and the wall, whichmore » is especially important in regimes where the LH waves are weakly damped and undergo multiple reflections from the plasma boundary. Uncertainties introduced in the processing of diagnostic data as well as uncertainties introduced by model approximations are assessed. We show that, by comparing the evolution of the plasma parameters in self-consistent simulations with available data, inconsistencies can be identified and limitations in the models or in the experimental data assessed.« less

  18. Experimental and modeling uncertainties in the validation of lower hybrid current drive

    DOE PAGES

    Poli, F. M.; Bonoli, P. T.; Chilenski, M.; ...

    2016-07-28

    Our work discusses sources of uncertainty in the validation of lower hybrid wave current drive simulations against experiments, by evolving self-consistently the magnetic equilibrium and the heating and current drive profiles, calculated with a combined toroidal ray tracing code and 3D Fokker–Planck solver. The simulations indicate a complex interplay of elements, where uncertainties in the input plasma parameters, in the models and in the transport solver combine and compensate each other, at times. It is concluded that ray-tracing calculations should include a realistic representation of the density and temperature in the region between the confined plasma and the wall, whichmore » is especially important in regimes where the LH waves are weakly damped and undergo multiple reflections from the plasma boundary. Uncertainties introduced in the processing of diagnostic data as well as uncertainties introduced by model approximations are assessed. We show that, by comparing the evolution of the plasma parameters in self-consistent simulations with available data, inconsistencies can be identified and limitations in the models or in the experimental data assessed.« less

  19. Measurement of bi-directional ion acceleration along a convergent-divergent magnetic nozzle

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhang, Yunchao, E-mail: yunchao.zhang@anu.edu.au; Charles, Christine; Boswell, Rod

    Bi-directional plasma expansion resulting in the formation of ion beams travelling in opposite directions is respectively measured in the converging and diverging parts of a magnetic nozzle created using a low-pressure helicon radio-frequency plasma source. The axial profile of ion saturation current along the nozzle is closely correlated to that of the magnetic flux density, and the ion “swarm” has a zero convective velocity at the magnetic throat where plasma generation is localized, thereby balancing the bi-directional particle loss. The ion beam potentials measured on both sides of the magnetic nozzle show results consistent with the maximum plasma potential measuredmore » at the throat.« less

  20. Current role of ICP-MS in clinical toxicology and forensic toxicology: a metallic profile.

    PubMed

    Goullé, Jean-Pierre; Saussereau, Elodie; Mahieu, Loïc; Guerbet, Michel

    2014-08-01

    As metal/metalloid exposure is inevitable owing to its omnipresence, it may exert toxicity in humans. Recent advances in metal/metalloid analysis have been made moving from flame atomic absorption spectrometry and electrothermal atomic absorption spectrometry to the multi-elemental inductively coupled plasma (ICP) techniques as ICP atomic emission spectrometry and ICP-MS. ICP-MS has now emerged as a major technique in inorganic analytical chemistry owing to its flexibility, high sensitivity and good reproducibility. This in depth review explores the ICP-MS metallic profile in human toxicology. It is now routinely used and of great importance, in clinical toxicology and forensic toxicology to explore biological matrices, specifically whole blood, plasma, urine, hair, nail, biopsy samples and tissues.

  1. Electron Temperature Evolution During Local Helicity Injection on the Pegasus Toroidal Experiment

    NASA Astrophysics Data System (ADS)

    Schlossberg, D. J.; Barr, J. L.; Bodner, G. M.; Bongard, M. W.; Fonck, R. J.; Perry, J. M.; Reusch, J. A.; Rodriguez Sanchez, C.

    2016-10-01

    Understanding the electron temperature (Te) evolution during local helicity injection (LHI) is critical for scaling up this non-solenoidal startup technique to MA-class devices. The first comprehensive Te measurements during LHI reveal centrally-peaked profiles with Te > 100 eV for plasma current Ip > 120 kA, toroidal field 0.15 T, and electron density ne 1019 m-3. Te rises and is sustained from just after magnetic relaxation through the plasma decoupling from edge-localized injectors. Results are presented for two injector edge locations: outboard midplane and inboard divertor. Outboard midplane injection couples LHI with inductive drive from poloidal field ramps and radial compression during inward plasma growth. Comparisons of Te at different LHI-to-inductive drive ratios show some profile flattening for higher LHI drive fraction. The latter, constant-shape discharges were necessarily lower performance, with Ip 50 kA and reduced Te , max. Inboard divertor injection achieves higher Ip using minimal inductive drive and thus isolates effects of LHI drive on Te. Initial results in this configuration show Te rising rapidly at the injector location as the discharge grows, settling to a roughly flat profile 100 eV. Thus far, both scenarios provide relatively stable discharges with moderate ne and high-Te, suitable for coupling to auxiliary current drive. Detailed studies of confinement dynamics and discharge optimization are planned for the near future. Work supported by US DOE Grant DE-FG02-96ER54375.

  2. Effect of heating scheme on SOL width in DIII-D and EAST

    DOE PAGES

    Wang, L.; Makowski, M. A.; Guo, H. Y.; ...

    2017-03-10

    Joint DIII-D/EAST experiments in the radio-frequency (RF) heated H-mode scheme with comparison to that of neutral beam (NB) heated H-mode scheme were carried out on DIII-D and EAST under similar conditions to examine the effect of heating scheme on scrape-off layer (SOL) width in H-mode plasmas for application to ITER. A dimensionally similar plasma equilibrium was used to match the EAST shape parameters. The divertor heat flux and SOL widths were measured with infra-red camera in DIII-D, while with divertor Langmuir probe array in EAST. It has been demonstrated on both DIII-D and EAST that RF-heated plasma has a broadermore » SOL than NB-heated plasma when the edge electrons are effectively heated in low plasma current and low density regime with low edge collisionality. Detailed edge and pedestal profile analysis on DIII-D suggests that the low edge collisionality and ion orbit loss effect may account for the observed broadening. Finally, the joint experiment in DIII-D has also demonstrated the strong inverse dependence of SOL width on the plasma current in electron cyclotron heated (ECH) H-mode plasmas.« less

  3. Effect of heating scheme on SOL width in DIII-D and EAST

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, L.; Makowski, M. A.; Guo, H. Y.

    Joint DIII-D/EAST experiments in the radio-frequency (RF) heated H-mode scheme with comparison to that of neutral beam (NB) heated H-mode scheme were carried out on DIII-D and EAST under similar conditions to examine the effect of heating scheme on scrape-off layer (SOL) width in H-mode plasmas for application to ITER. A dimensionally similar plasma equilibrium was used to match the EAST shape parameters. The divertor heat flux and SOL widths were measured with infra-red camera in DIII-D, while with divertor Langmuir probe array in EAST. It has been demonstrated on both DIII-D and EAST that RF-heated plasma has a broadermore » SOL than NB-heated plasma when the edge electrons are effectively heated in low plasma current and low density regime with low edge collisionality. Detailed edge and pedestal profile analysis on DIII-D suggests that the low edge collisionality and ion orbit loss effect may account for the observed broadening. Finally, the joint experiment in DIII-D has also demonstrated the strong inverse dependence of SOL width on the plasma current in electron cyclotron heated (ECH) H-mode plasmas.« less

  4. On axisymmetric resistive MHD equilibria with flow free of Pfirsch-Schlüter diffusion

    NASA Astrophysics Data System (ADS)

    Throumoulopoulos, George N.; Tasso, Henri

    2002-11-01

    The equilibrium of an axisymmetric magnetically confined plasma with anisotropic electrical conductivity and flows parallel to the magnetic field is investigated within the framework of the MHD theory by keeping the convective flow term in the momentum equation. It turns out that the stationary states are determined by a second-order partial differential equation for the poloidal magnetic flux function along with a Bernoulli equation for the density identical in form with the respective ideal MHD equations; equilibrium consistent expressions for the conductivities σ_allel and σ_⊥ parallel and perpendicular to the magnetic field are also derived from Ohm's and Faraday's laws. Unlike in the case of stationary states with isotropic conductivity and parallel flows (see [1]) the equilibrium is compatible with non-vanishing poloidal currents. For incompressible flows exact solutions of the above mentioned set of equations can be constructed with σ_allel and σ_⊥ profiles compatible with collisional conductivity profiles, i.e. profiles peaked close to the magnetic axis, vanishing on the boundary and such that σ_allel> σ_⊥. In particular, an exact equilibrium describing a toroidal plasma of arbitrary aspect ratio being contained within a perfectly conducting boundary of rectangular cross-section and peaked toroidal current density profile vanishing on the boundary is further considered. For this equilibrium in the case of vanishing flows the difference σ_allel-σ_⊥ for the reversed field pinch scaling Bp Bt (where Bp and Bt are the poloidal and toroidal magnetic field components) is nearly two times larger than that for the tokamak scaling B_p 0.1 B_t. [1] G. N. Throumoulopoulos, H. Tasso, J. Plasma Physics 64, 601 (2000).

  5. Magnetic Fluctuation-Driven Intrinsic Flow in a Toroidal Plasma

    NASA Astrophysics Data System (ADS)

    Brower, D. L.; Ding, W. X.; Lin, L.; Almagri, A. F.; den Hartog, D. J.; Sarff, J. S.

    2012-10-01

    Magnetic fluctuations have been long observed in various magnetic confinement configurations. These perturbations may arise naturally from plasma instabilities such as tearing modes and energetic particle driven modes, but they can also be externally imposed by error fields or external magnetic coils. It is commonly observed that large MHD modes lead to plasma locking (no rotation) due to torque produced by eddy currents on the wall, and it is predicted that stochastic field induces flow damping where the radial electric field is reduced. Flow generation is of great importance to fusion plasma research, especially low-torque devices like ITER, as it can act to improve performance. Here we describe new measurements in the MST reversed field pinch (RFP) showing that the coherent interaction of magnetic and particle density fluctuations can produce a turbulent fluctuation-induced kinetic force, which acts to drive intrinsic plasma rotation. Key observations include; (1) the average kinetic force resulting from density fluctuations, ˜ 0.5 N/m^3, is comparable to the intrinsic flow acceleration, and (2) between sawtooth crashes, the spatial distribution of the kinetic force is directed to create a sheared parallel flow profile that is consistent with the measured flow profile in direction and amplitude, suggesting the kinetic force is responsible for intrinsic plasma rotation.

  6. Multiprobe characterization of plasma flows for space propulsion

    NASA Astrophysics Data System (ADS)

    Damba, Julius; Argente, P.; Maldonado, P. E.; Cervone, A.; Domenech-Garret, J. L.; Conde, L.

    2018-02-01

    Plasma engines for space propulsion generate plasma jets (also denominated plasma plumes) having supersonic ion groups with typical speeds in the order of tens of kilometers per second, which lies between electron and ion thermal speeds. Studies of the stationary plasma expansion process using a four-grid retarding field energy analyzer (RFEA), an emissive probe (EP) and a Langmuir probe (LP), all mounted on a three dimensionally (3D) displaced multiprobe structure are discussed. Specifically, the determination of plasma beam properties from the RFEA current-voltage (IV) characteristic curves is presented. The experimental results show the ion energy spectra to be essentially unchanged over 300 mm along the plasma-jet expansion axis of symmetry. The measured ion velocity distribution function (IVDF) results from the superposition of different ion groups and has two dominant populations: A low-energy group constituted of ions from the background plasma is produced by the interaction of the plasma jet with the walls of the vacuum chamber. The fast-ion population is composed of ions from the plasma beam moving at supersonic speeds with respect to the low-energy ions. The decreasing spatial profiles of the plasma-jet current density are compared with those of the low-energy ion group, which are not uniform along the axis of symmetry because of the small contributions from other ion populations with intermediate speeds.

  7. Generation of multiple toroidal dust vortices by a non-monotonic density gradient in a direct current glow discharge plasma

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kaur, Manjit, E-mail: manjit@ipr.res.in; Bose, Sayak; Chattopadhyay, P. K.

    2015-09-15

    Observation of two well-separated dust vortices in an unmagnetized parallel plate DC glow discharge plasma is reported in this paper. A non-monotonic radial density profile, achieved by an especially designed cathode structure using a concentric metallic disk and ring of different radii, is observed to produce double dust tori between cathode and anode. PIV analysis of the still images of the double tori shows oppositely rotating dust structures between the central disk and the ring. Langmuir probe measurements of background plasma shows a non-uniform plasma density profile between the disk and the ring. Location and sense of rotation of themore » dust vortices coincides with the location and direction of the radial gradient in the ion drag force caused by the radial density gradient. The experimentally observed dust vorticity matches well with the calculated one using hydrodynamic formulations with shear in ion drag dominating over the dust charge gradient. These results corroborate that a radial gradient in the ion drag force directed towards cathode is the principal cause of dust rotation.« less

  8. Magnetospheric Reconnection in Modified Current-Sheet Equilibria

    NASA Astrophysics Data System (ADS)

    Newman, D. L.; Goldman, M. V.; Lapenta, G.; Markidis, S.

    2012-10-01

    Particle simulations of magnetic reconnection in Earth's magnetosphere are frequently initialized with a current-carrying Harris equilibrium superposed on a current-free uniform background plasma. The Harris equilibrium satisfies local charge neutrality, but requires that the sheet current be dominated by the hotter species -- often the ions in Earth's magnetosphere. This constraint is not necessarily consistent with observations. A modified kinetic equilibrium that relaxes this constraint on the currents was proposed by Yamada et al. [Phys. Plasmas., 7, 1781 (2000)] with no background population. These modified equilibria were characterized by an asymptotic converging or diverging electrostatic field normal to the current sheet. By reintroducing the background plasma, we have developed new families of equilibria where the asymptotic fields are suppressed by Debye shielding. Because the electrostatic potential profiles of these new equilibria contain wells and/or barriers capable of spatially isolating different populations of electrons and/or ions, these solutions can be further generalized to include classes of asymmetric kinetic equilibria. Examples of both symmetric and asymmetric equilibria will be presented. The dynamical evolution of these equilibria, when perturbed, will be further explored by means of implicit 2D PIC reconnection simulations, including comparisons with simulations employing standard Harris-equilibrium initializations.

  9. Validation of the thermal transport model used for ITER startup scenario predictions with DIII-D experimental data

    DOE PAGES

    Casper, T. A.; Meyer, W. H.; Jackson, G. L.; ...

    2010-12-08

    We are exploring characteristics of ITER startup scenarios in similarity experiments conducted on the DIII-D Tokamak. In these experiments, we have validated scenarios for the ITER current ramp up to full current and developed methods to control the plasma parameters to achieve stability. Predictive simulations of ITER startup using 2D free-boundary equilibrium and 1D transport codes rely on accurate estimates of the electron and ion temperature profiles that determine the electrical conductivity and pressure profiles during the current rise. Here we present results of validation studies that apply the transport model used by the ITER team to DIII-D discharge evolutionmore » and comparisons with data from our similarity experiments.« less

  10. The high-βN hybrid scenario for ITER and FNSF steady-state missions

    DOE PAGES

    Turco, Francesca; Petty, Clinton C.; Luce, Timothy C.; ...

    2015-05-15

    New experiments on DIII-D have demonstrated the steady-state potential of the hybrid scenario, with 1 MA of plasma current driven fully non-inductively and βN up to 3.7 sustained for ~3 s (~1.5 current diffusion time, τ R, in DIII-D), providing the basis for an attractive option for steady-state operation in ITER and FNSF. Excellent confinement is achieved (H 98y2~1.6) without performance limiting tearing modes. Furthermore, the hybrid regime overcomes the need for off-axis current drive efficiency, taking advantage of poloidal magnetic flux pumping that is believed to be the result of a saturated 3/2 tearing mode. This allows for efficientmore » current drive close to the axis, without deleterious sawtooth instabilities. In these experiments, the edge surface loop voltage is driven down to zero for >1 τ R when the poloidal β is increased above 1.9 at a plasma current of 1.0 MA and the ECH power is increased to 3.2 MW. Stationary operation of hybrid plasmas with all on-axis current drive is sustained at pressures slightly above the ideal no-wall limit, while the calculated ideal with-wall MHD limit is β N~4-4.5. Off-axis NBI power has been used to broaden the pressure and current profiles in this scenario, seeking to take advantage of higher predicted kink stability limits and lower values of the tearing stability index Δ', as calculated by the DCON and PEST3 codes. Our results are based on measured profiles that predict ideal limits at βN>4.5, 10% higher than the cases with on-axis NBI. A 0-D model, based on the present confinement, βN and shape values of the DIII-D hybrid scenario, shows that these plasmas are consistent with the ITER 9 MA, Q=5 mission and the FNSF 6.7 MA scenario with Q=3.5. With collisionality and edge safety factor values comparable to those envisioned for ITER and FNSF, the high-βN hybrid represents an attractive high performance option for the steady-state missions of these devices.« less

  11. Cigarette smoking substantially alters plasma microRNA profiles in healthy subjects

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Takahashi, Kei; Yokota, Shin-ichi; Tatsumi, Naoyuki

    Circulating microRNAs (miRNAs) are receiving attention as potential biomarkers of various diseases, including cancers, chronic obstructive pulmonary disease, and cardiovascular disease. However, it is unknown whether the levels of circulating miRNAs in a healthy subject might vary with external factors in daily life. In this study, we investigated whether cigarette smoking, a habit that has spread throughout the world and is a risk factor for various diseases, affects plasma miRNA profiles. We determined the profiles of 11 smokers and 7 non-smokers by TaqMan MicroRNA array analysis. A larger number of miRNAs were detected in smokers than in non-smokers, and themore » plasma levels of two-thirds of the detected miRNAs (43 miRNAs) were significantly higher in smokers than in non-smokers. A principal component analysis of the plasma miRNA profiles clearly separated smokers and non-smokers. Twenty-four of the miRNAs were previously reported to be potential biomarkers of disease, suggesting the possibility that smoking status might interfere with the diagnosis of disease. Interestingly, we found that quitting smoking altered the plasma miRNA profiles to resemble those of non-smokers. These results suggested that the differences in the plasma miRNA profiles between smokers and non-smokers could be attributed to cigarette smoking. In addition, we found that an acute exposure of ex-smokers to cigarette smoke (smoking one cigarette) did not cause a dramatic change in the plasma miRNA profile. In conclusion, we found that repeated cigarette smoking substantially alters the plasma miRNA profile, interfering with the diagnosis of disease or signaling potential smoking-related diseases. - Highlights: • Plasma miRNA profiles were unambiguously different between smokers and non-smokers. • Smoking status might interfere with the diagnosis of disease using plasma miRNAs. • Changes of plasma miRNA profiles may be a signal of smoking-related diseases.« less

  12. Study of runaway electrons with Hard X-ray spectrometry of tokamak plasmas

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shevelev, A.; Chugunov, I.; Khilkevitch, E.

    2014-08-21

    Hard-X-ray spectrometry is a tool widely used for diagnostic of runaway electrons in existing tokamaks. In future machines, ITER and DEMO, HXR spectrometry will be useful providing information on runaway electron energy, runaway beam current and its profile during disruption.

  13. THEMIS two‐point measurements of the cross‐tail current density: A thick bifurcated current sheet in the near‐Earth plasma sheet

    PubMed Central

    2015-01-01

    Abstract The basic properties of the near‐Earth current sheet from 8 RE to 12 RE were determined based on Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations from 2007 to 2013. Ampere's law was used to estimate the current density when the locations of two spacecraft were suitable for the calculation. A total of 3838 current density observations were obtained to study the vertical profile. For typical solar wind conditions, the current density near (off) the central plane of the current sheet ranged from 1 to 2 nA/m2 (1 to 8 nA/m2). All the high current densities appeared off the central plane of the current sheet, indicating the formation of a bifurcated current sheet structure when the current density increased above 2 nA/m2. The median profile also showed a bifurcated structure, in which the half thickness was about 3 RE. The distance between the peak of the current density and the central plane of the current sheet was 0.5 to 1 RE. High current densities above 4 nA/m2 were observed in some cases that occurred preferentially during substorms, but they also occurred in quiet times. In contrast to the commonly accepted picture, these high current densities can form without a high solar wind dynamic pressure. In addition, these high current densities can appear in two magnetic configurations: tail‐like and dipolar structures. At least two mechanisms, magnetic flux depletion and new current system formation during the expansion phase, other than plasma sheet compression are responsible for the formation of the bifurcated current sheets. PMID:27722039

  14. Properties of the electrostatically driven helical plasma state

    NASA Astrophysics Data System (ADS)

    Akçay, Cihan; Finn, John M.; Nebel, Richard A.; Barnes, Daniel C.; Martin, Neal

    2018-02-01

    A novel plasma state has been found [Akçay et al., Phys. Plasmas 24, 052503 (2017)] in the presence of a uniform applied axial magnetic field in periodic cylindrical geometry. This state is driven by external electrostatic fields provided by helical electrodes with a (m =1 ,n =1 ) (helical) symmetry where m and n represent the poloidal and axial harmonics. The resulting plasma is a function of the cylinder radius r

  15. Honeycomblike large area LaB6 plasma source for Multi-Purpose Plasma facility

    NASA Astrophysics Data System (ADS)

    Woo, Hyun-Jong; Chung, Kyu-Sun; You, Hyun-Jong; Lee, Myoung-Jae; Lho, Taihyeop; Choh, Kwon Kook; Yoon, Jung-Sik; Jung, Yong Ho; Lee, Bongju; Yoo, Suk Jae; Kwon, Myeon

    2007-10-01

    A Multi-Purpose Plasma (MP2) facility has been renovated from Hanbit mirror device [Kwon et al., Nucl. Fusion 43, 686 (2003)] by adopting the same philosophy of diversified plasma simulator (DiPS) [Chung et al., Contrib. Plasma Phys. 46, 354 (2006)] by installing two plasma sources: LaB6 (dc) and helicon (rf) plasma sources; and making three distinct simulators: divertor plasma simulator, space propulsion simulator, and astrophysics simulator. During the first renovation stage, a honeycomblike large area LaB6 (HLA-LaB6) cathode was developed for the divertor plasma simulator to improve the resistance against the thermal shock fragility for large and high density plasma generation. A HLA-LaB6 cathode is composed of the one inner cathode with 4in. diameter and the six outer cathodes with 2in. diameter along with separate graphite heaters. The first plasma is generated with Ar gas and its properties are measured by the electric probes with various discharge currents and magnetic field configurations. Plasma density at the middle of central cell reaches up to 2.6×1012 cm-3, while the electron temperature remains around 3-3.5eV at the low discharge current of less than 45A, and the magnetic field intensity of 870G. Unique features of electric property of heaters, plasma density profiles, is explained comparing with those of single LaB6 cathode with 4in. diameter in DiPS.

  16. Honeycomblike large area LaB6 plasma source for Multi-Purpose Plasma facility.

    PubMed

    Woo, Hyun-Jong; Chung, Kyu-Sun; You, Hyun-Jong; Lee, Myoung-Jae; Lho, Taihyeop; Choh, Kwon Kook; Yoon, Jung-Sik; Jung, Yong Ho; Lee, Bongju; Yoo, Suk Jae; Kwon, Myeon

    2007-10-01

    A Multi-Purpose Plasma (MP(2)) facility has been renovated from Hanbit mirror device [Kwon et al., Nucl. Fusion 43, 686 (2003)] by adopting the same philosophy of diversified plasma simulator (DiPS) [Chung et al., Contrib. Plasma Phys. 46, 354 (2006)] by installing two plasma sources: LaB(6) (dc) and helicon (rf) plasma sources; and making three distinct simulators: divertor plasma simulator, space propulsion simulator, and astrophysics simulator. During the first renovation stage, a honeycomblike large area LaB(6) (HLA-LaB(6)) cathode was developed for the divertor plasma simulator to improve the resistance against the thermal shock fragility for large and high density plasma generation. A HLA-LaB(6) cathode is composed of the one inner cathode with 4 in. diameter and the six outer cathodes with 2 in. diameter along with separate graphite heaters. The first plasma is generated with Ar gas and its properties are measured by the electric probes with various discharge currents and magnetic field configurations. Plasma density at the middle of central cell reaches up to 2.6 x 10(12) cm(-3), while the electron temperature remains around 3-3.5 eV at the low discharge current of less than 45 A, and the magnetic field intensity of 870 G. Unique features of electric property of heaters, plasma density profiles, is explained comparing with those of single LaB(6) cathode with 4 in. diameter in DiPS.

  17. Status of Electron Bernstein Wave (EBW) Research on NSTX and CDX-U

    NASA Astrophysics Data System (ADS)

    Taylor, G.; Efthimion, P. C.; Jones, B. M.; Wilson, J. R.; Wilgen, J. B.; Bell, G. L.; Bigelow, T. S.; Rasmussen, D. A.; Ram, A. K.; Bers, A.; Harvey, R. W.

    2002-11-01

    Recent studies of EBWs, via mode conversion (MC) to X-mode electromagnetic radiation on the CDX-U and NSTX spherical torus (ST) plasmas, support the use of EBWs to measure the Te profile and allow local heating and current drive in ST plasmas. An in-vessel antenna with a local adjustable limiter has successfully controlled the density scale length at the MC layer in CDX-U increasing the MC by an order of magnitude to ˜ 100%. A similar technique on NSTX has so far increased MC efficiency fivefold to ˜ 50%. Both results are in good agreement with theoretical predictions. Experiments focused on achieving >= 80% MC on NSTX are planned for the coming year. Ray tracing and Fokker-Planck modeling support the design of a ˜ 1 MW EBW heating and current drive system for NSTX that will assist plasma startup, locally heat electrons, drive non-inductive current and may suppress tearing modes or other MHD that limit high β operation.

  18. Spectroscopic characterization of H 2 and D 2 helicon plasmas generated by a resonant antenna for neutral beam applications in fusion

    NASA Astrophysics Data System (ADS)

    Marini, C.; Agnello, R.; Duval, B. P.; Furno, I.; Howling, A. A.; Jacquier, R.; Karpushov, A. N.; Plyushchev, G.; Verhaegh, K.; Guittienne, Ph.; Fantz, U.; Wünderlich, D.; Béchu, S.; Simonin, A.

    2017-03-01

    A new generation of neutral beam systems will be required in future fusion reactors, such as DEMO, able to deliver high power (up to 50 MW) with high (800 keV or higher) neutral energy. Only negative ion beams may be able to attain this performance, which has encouraged a strong research focus on negative ion production from both surface and volumetric plasma sources. A novel helicon plasma source, based on the resonant birdcage network antenna configuration, is currently under study at the Swiss Plasma Centre before installation on the Cybele negative ion source at the Institute for Magnetic Fusion Research, CEA, Cadarache, France. This source is driven by up to 10 kW at 13.56 MHz, and is being tested on a linear resonant antenna ion device. Passive spectroscopic measurements of the first three Balmer lines α, β and γ and of the Fulcher-α bands were performed with an f/2 spectrometer, for both hydrogen and deuterium. Multiple viewing lines and an absolute intensity calibration were used to determine the plasma radiance profile, with a spatial resolution  <3 mm. A minimum Fisher regularization algorithm was applied to obtain the absolute emissivity profile for each emission line for cylindrical symmetry, which was experimentally confirmed. An uncertainty estimate of the inverted profiles was performed using a Monte Carlo approach. Finally, a radiofrequency-compensated Langmuir probe was inserted to measured the electron temperature and density profiles. The absolute line emissivities are interpreted using the collisional-radiative code YACORA which estimates the degree of dissociation and the distribution of the atomic and molecular species, including the negative ion density. This paper reports the results of a power scan up to 5 kW in conditions satisfying Cybele requirements for the plasma source, namely a low neutral pressure, p≤slant 0.3 Pa and magnetic field B≤slant 150 G.

  19. Plasma Equilibria With Stochastic Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Krommes, J. A.; Reiman, A. H.

    2009-05-01

    Plasma equilibria that include regions of stochastic magnetic fields are of interest in a variety of applications, including tokamaks with ergodic limiters and high-pressure stellarators. Such equilibria are examined theoretically, and a numerical algorithm for their construction is described.^2,3 % The balance between stochastic diffusion of magnetic lines and small effects^2 omitted from the simplest MHD description can support pressure and current profiles that need not be flattened in stochastic regions. The diffusion can be described analytically by renormalizing stochastic Langevin equations for pressure and parallel current j, with particular attention being paid to the satisfaction of the periodicity constraints in toroidal configurations with sheared magnetic fields. The equilibrium field configuration can then be constructed by coupling the prediction for j to Amp'ere's law, which is solved numerically. A. Reiman et al., Pressure-induced breaking of equilibrium flux surfaces in the W7AS stellarator, Nucl. Fusion 47, 572--8 (2007). J. A. Krommes and A. H. Reiman, Plasma equilibrium in a magnetic field with stochastic regions, submitted to Phys. Plasmas. J. A. Krommes, Fundamental statistical theories of plasma turbulence in magnetic fields, Phys. Reports 360, 1--351.

  20. Gas-filled capillaries for plasma-based accelerators

    NASA Astrophysics Data System (ADS)

    Filippi, F.; Anania, M. P.; Brentegani, E.; Biagioni, A.; Cianchi, A.; Chiadroni, E.; Ferrario, M.; Pompili, R.; Romeo, S.; Zigler, A.

    2017-07-01

    Plasma Wakefield Accelerators are based on the excitation of large amplitude plasma waves excited by either a laser or a particle driver beam. The amplitude of the waves, as well as their spatial dimensions and the consequent accelerating gradient depend strongly on the background electron density along the path of the accelerated particles. The process needs stable and reliable plasma sources, whose density profile must be controlled and properly engineered to ensure the appropriate accelerating mechanism. Plasma confinement inside gas filled capillaries have been studied in the past since this technique allows to control the evolution of the plasma, ensuring a stable and repeatable plasma density distribution during the interaction with the drivers. Moreover, in a gas filled capillary plasma can be pre-ionized by a current discharge to avoid ionization losses. Different capillary geometries have been studied to allow the proper temporal and spatial evolution of the plasma along the acceleration length. Results of this analysis obtained by varying the length and the number of gas inlets will be presented.

  1. Laboratory measurements of white dwarf photospheric spectral lines: Hβ

    DOE PAGES

    Falcon, Ross Edward; Rochau, Gregory A.; Bailey, James E.; ...

    2015-06-18

    We spectroscopically measure multiple hydrogen Balmer line profiles from laboratory plasmas to investigate the theoretical line profiles used in white dwarf (WD) atmosphere models. X-ray radiation produced at the Z Pulsed Power Facility at Sandia National Laboratories initiates plasma formation in a hydrogen-filled gas cell, replicating WD photospheric conditions. We also present time-resolved measurements of Hβ and fit this line using different theoretical line profiles to diagnose electron density, n e, and n = 2 level population, n 2. Aided by synthetic tests, we characterize the validity of our diagnostic method for this experimental platform. During a single experiment, wemore » infer a continuous range of electron densities increasing from n e ~ 4 to ~30 × 10 16 cm -3 throughout a 120-ns evolution of our plasma. Also, we observe n 2 to be initially elevated with respect to local thermodynamic equilibrium (LTE); it then equilibrates within ~55 ns to become consistent with LTE. This also supports our electron-temperature determination of T e ~ 1.3 eV (~15,000 K) after this time. At n e≲ 10 17 cm -3, we find that computer-simulation-based line-profile calculations provide better fits (lower reduced χ 2) than the line profiles currently used in the WD astronomy community. The inferred conditions, however, are in good quantitative agreement. Lastly, this work establishes an experimental foundation for the future investigation of relative shapes and strengths between different hydrogen Balmer lines.« less

  2. Filamentary structures in dense plasma focus: Current filaments or vortex filaments?

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Soto, Leopoldo, E-mail: lsoto@cchen.cl; Pavez, Cristian; Moreno, José

    2014-07-15

    Recent observations of an azimuthally distributed array of sub-millimeter size sources of fusion protons and correlation between extreme ultraviolet (XUV) images of filaments with neutron yield in PF-1000 plasma focus have re-kindled interest in their significance. These filaments have been described variously in literature as current filaments and vortex filaments, with very little experimental evidence in support of either nomenclature. This paper provides, for the first time, experimental observations of filaments on a table-top plasma focus device using three techniques: framing photography of visible self-luminosity from the plasma, schlieren photography, and interferometry. Quantitative evaluation of density profile of filaments frommore » interferometry reveals that their radius closely agrees with the collision-less ion skin depth. This is a signature of relaxed state of a Hall fluid, which has significant mass flow with equipartition between kinetic and magnetic energy, supporting the “vortex filament” description. This interpretation is consistent with empirical evidence of an efficient energy concentration mechanism inferred from nuclear reaction yields.« less

  3. HSX as an example of a resilient non-resonant divertor

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bader, A.; Boozer, A. H.; Hegna, C. C.

    This study describes an initial description of the resilient divertor properties of quasi-symmetric (QS) stellarators using the HSX (Helically Symmetric eXperiment) configuration as a test-case. Divertors in high-performance QS stellarators will need to be resilient to changes in plasma configuration that arise due to evolution of plasma pressure profiles and bootstrap currents for divertor design. Resiliency is tested by examining the changes in strike point patterns from the field line following, which arise due to configurational changes. A low strike point variation with high configuration changes corresponds to high resiliency. The HSX edge displays resilient properties with configuration changes arisingmore » from the (1) wall position, (2) plasma current, and (3) external coils. The resilient behavior is lost if large edge islands intersect the wall structure. The resilient edge properties are corroborated by heat flux calculations from the fully 3-D plasma simulations using EMC3-EIRENE. Additionally, the strike point patterns are found to correspond to high curvature regions of magnetic flux surfaces.« less

  4. Electron temperature profiles in axial field 2.45 GHz ECR ion source with a ceramic chamber

    NASA Astrophysics Data System (ADS)

    Abe, K.; Tamura, R.; Kasuya, T.; Wada, M.

    2017-08-01

    An array of electrostatic probes was arranged on the plasma electrode of a 2.45 GHz microwave driven axial magnetic filter field type negative hydrogen (H-) ion source to clarify the spatial plasma distribution near the electrode. The measured spatial distribution of electron temperature indicated the lower temperature near the extraction hole of the plasma electrode corresponding to the effectiveness of the axial magnetic filter field geometry. When the ratio of electron saturation current to the ion saturation current was plotted as a function of position, the obtained distribution showed a higher ratio near the hydrogen gas inlet through which ground state hydrogen molecules are injected into the source. Though the efficiency in producing H- ions is smaller for a 2.45 GHz source than a source operated at 14 GHz, it gives more volume to measure spatial distributions of various plasma parameters to understand fundamental processes that are influential on H- production in this type of ion sources.

  5. HSX as an example of a resilient non-resonant divertor

    DOE PAGES

    Bader, A.; Boozer, A. H.; Hegna, C. C.; ...

    2017-03-16

    This study describes an initial description of the resilient divertor properties of quasi-symmetric (QS) stellarators using the HSX (Helically Symmetric eXperiment) configuration as a test-case. Divertors in high-performance QS stellarators will need to be resilient to changes in plasma configuration that arise due to evolution of plasma pressure profiles and bootstrap currents for divertor design. Resiliency is tested by examining the changes in strike point patterns from the field line following, which arise due to configurational changes. A low strike point variation with high configuration changes corresponds to high resiliency. The HSX edge displays resilient properties with configuration changes arisingmore » from the (1) wall position, (2) plasma current, and (3) external coils. The resilient behavior is lost if large edge islands intersect the wall structure. The resilient edge properties are corroborated by heat flux calculations from the fully 3-D plasma simulations using EMC3-EIRENE. Additionally, the strike point patterns are found to correspond to high curvature regions of magnetic flux surfaces.« less

  6. Characterization of the Low-Molecular-Weight Human Plasma Peptidome.

    PubMed

    Greening, David W; Simpson, Richard J

    2017-01-01

    The human plasma proteome represents an important secreted sub-proteome. Proteomic analysis of blood plasma with mass spectrometry is a challenging task. The high complexity and wide dynamic range of proteins as well as the presence of several proteins at very high concentrations complicate the profiling of the human plasma proteome. The peptidome (or low-molecular-weight fraction, LMF) of the human plasma proteome is an invaluable source of biological information, especially in the context of identifying plasma-based markers of disease. Peptides are generated by active synthesis and proteolytic processing, often yielding proteolytic fragments that mediate a variety of physiological and pathological functions. As such, degradomic studies, investigating cleavage products via peptidomics and top-down proteomics in particular, have warranted significant research interest. However, due to their molecular weight, abundance, and solubility, issues with identifying specific cleavage sites and coverage of peptide fragments remain challenging. Peptidomics is currently focused toward comprehensively studying peptides cleaved from precursor proteins by endogenous proteases. This protocol outlines a standardized rapid and reproducible procedure for peptidomic profiling of human plasma using centrifugal ultrafiltration and mass spectrometry. Ultrafiltration is a convective process that uses anisotropic semipermeable membranes to separate macromolecular species on the basis of size. We have optimized centrifugal ultrafiltration (cellulose triacetate membrane) for plasma fractionation with respect to buffer and solvent composition, centrifugal force, duration, and temperature to facilitate recovery >95% and enrichment of the human plasma peptidome. This method serves as a comprehensive and facile process to enrich and identify a key, underrepresented sub-proteome of human blood plasma.

  7. ADX - Advanced Divertor and RF Tokamak Experiment

    NASA Astrophysics Data System (ADS)

    Greenwald, Martin; Labombard, Brian; Bonoli, Paul; Irby, Jim; Terry, Jim; Wallace, Greg; Vieira, Rui; Whyte, Dennis; Wolfe, Steve; Wukitch, Steve; Marmar, Earl

    2015-11-01

    The Advanced Divertor and RF Tokamak Experiment (ADX) is a design concept for a compact high-field tokamak that would address boundary plasma and plasma-material interaction physics challenges whose solution is critical for the viability of magnetic fusion energy. This device would have two crucial missions. First, it would serve as a Divertor Test Tokamak, developing divertor geometries, materials and operational scenarios that could meet the stringent requirements imposed in a fusion power plant. By operating at high field, ADX would address this problem at a level of power loading and other plasma conditions that are essentially identical to those expected in a future reactor. Secondly, ADX would investigate the physics and engineering of high-field-side launch of RF waves for current drive and heating. Efficient current drive is an essential element for achieving steady-state in a practical, power producing fusion device and high-field launch offers the prospect of higher efficiency, better control of the current profile and survivability of the launching structures. ADX would carry out this research in integrated scenarios that simultaneously demonstrate the required boundary regimes consistent with efficient current drive and core performance.

  8. Preliminary Results Of A 600 Joules Small Plasma Focus Device

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lee, S. H.; Yap, S. L.; Wong, C. S.

    Preliminary results of a 600 J (3.7 muF, 18 kV) Mather type plasma focus device operated at low pressure will be presented. The discharge is formed between a solid anode with length of 6 cm and six symmetrically and coaxially arranged cathode rods of same lengths. The cathode base is profiled in a knife-edge design and a set of coaxial plasma gun are attached to it in order to initiate the breakdown and enhance the current sheath formation. The experiments have been performed in argon gas under a low pressure condition of several microbars. The discharge current and the voltagemore » across the electrodes during the discharge are measured with high voltage probe and current coil. The current and voltage characteristics are used to determine the possible range of operating pressure that gives good focusing action. At a narrow pressure regime of 9.0+-0.5 mubar, focusing action is observed with good reproducibility. Preliminary result of ion beam energy is presented. More work will be carried out to investigate the radiation output.« less

  9. Properties of thermal air plasma with admixing of copper and carbon

    NASA Astrophysics Data System (ADS)

    Fesenko, S.; Veklich, A.; Boretskij, V.; Cressault, Y.; Gleizes, A.; Teulet, Ph

    2014-11-01

    This paper deals with investigations of air plasma with admixing of copper and carbon. Model plasma source unit with real breaking arc was used for the simulation of real discharges, which can be occurred during sliding of Cu-C composite electrodes on copper wire at electromotive vehicles. The complex technique of plasma property studies is developed. From one hand, the radial profiles of temperature and electron density in plasma of electric arc discharge in air between Cu-C composite and copper electrodes in air flow were measured by optical spectroscopy techniques. From another hand, the radial profiles of electric conductivity of plasma mixture were calculated by solution of energy balance equation. It was assumed that the thermal conductivity of air plasma is not depending on copper or carbon vapor admixtures. The electron density is obtained from electric conductivity profiles by calculation in assumption of local thermodynamic equilibrium in plasma. Computed in such way radial profiles of electron density in plasma of electric arc discharge in air between copper electrodes were compared with experimentally measured profiles. It is concluded that developed techniques of plasma diagnostics can be reasonably used in investigations of thermal plasma with copper and carbon vapors.

  10. Impact of the plasma geometry on divertor power exhaust: experimental evidence from TCV and simulations with SolEdge2D and TOKAM3X

    NASA Astrophysics Data System (ADS)

    Gallo, A.; Fedorczak, N.; Elmore, S.; Maurizio, R.; Reimerdes, H.; Theiler, C.; Tsui, C. K.; Boedo, J. A.; Faitsch, M.; Bufferand, H.; Ciraolo, G.; Galassi, D.; Ghendrih, P.; Valentinuzzi, M.; Tamain, P.; the EUROfusion MST1 Team; the TCV Team

    2018-01-01

    A deep understanding of plasma transport at the edge of magnetically confined fusion plasmas is needed for the handling and control of heat loads on the machine first wall. Experimental observations collected on a number of tokamaks over the last three decades taught us that heat flux profiles at the divertor targets of X-point configurations can be parametrized by using two scale lengths for the scrape-off layer (SOL) transport, separately characterizing the main SOL ({λ }q) and the divertor SOL (S q ). In this work we challenge the current interpretation of these two scale lengths as well as their dependence on plasma parameters by studying the effect of divertor geometry modifications on heat exhaust in the Tokamak à Configuration Variable. In particular, a significant broadening of the heat flux profiles at the outer divertor target is diagnosed while increasing the length of the outer divertor leg in lower single null, Ohmic, L-mode discharges. Efforts to reproduce this experimental finding with both diffusive (SolEdge2D-EIRENE) and turbulent (TOKAM3X) modelling tools confirm the validity of a diffusive approach for simulating heat flux profiles in more traditional, short leg, configurations while highlighting the need of a turbulent description for modified, long leg, ones in which strongly asymmetric divertor perpendicular transport develops.

  11. Experimental and Numerical Study of Drift Alfv'en Waves in LAPD

    NASA Astrophysics Data System (ADS)

    Friedman, Brett; Popovich, P.; Carter, T. A.; Auerbach, D.; Schaffner, D.

    2009-11-01

    We present a study of drift Alfv'en waves in linear geometry using experiments in the Large Plasma Device (LAPD) at UCLA and simulations from the Boundary Turbulence code (BOUT). BOUT solves the 3D time evolution of plasma parameters and turbulence using Braginskii fluid equations. First, we present a verification study of linear drift Alfven wave physics in BOUT, which has been modified to simulate the cylindrical geometry of LAPD. Second, we present measurements of density and magnetic field fluctuations in the LAPD plasma and the correlation of these fluctuations as a function of plasma parameters, including strength of the background field and discharge current. We also compare the measurements to nonlinear BOUT calculations using experimental LAPD profiles.

  12. Imaging of turbulent structures and tomographic reconstruction of TORPEX plasma emissivity

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Iraji, D.; Furno, I.; Fasoli, A.

    In the TORPEX [A. Fasoli et al., Phys. Plasmas 13, 055902 (2006)], a simple magnetized plasma device, low frequency electrostatic fluctuations associated with interchange waves, are routinely measured by means of extensive sets of Langmuir probes. To complement the electrostatic probe measurements of plasma turbulence and study of plasma structures smaller than the spatial resolution of probes array, a nonperturbative direct imaging system has been developed on TORPEX, including a fast framing Photron-APX-RS camera and an image intensifier unit. From the line-integrated camera images, we compute the poloidal emissivity profile of the plasma by applying a tomographic reconstruction technique usingmore » a pixel method and solving an overdetermined set of equations by singular value decomposition. This allows comparing statistical, spectral, and spatial properties of visible light radiation with electrostatic fluctuations. The shape and position of the time-averaged reconstructed plasma emissivity are observed to be similar to those of the ion saturation current profile. In the core plasma, excluding the electron cyclotron and upper hybrid resonant layers, the mean value of the plasma emissivity is observed to vary with (T{sub e}){sup {alpha}}(n{sub e}){sup {beta}}, in which {alpha}=0.25-0.7 and {beta}=0.8-1.4, in agreement with collisional radiative model. The tomographic reconstruction is applied to the fast camera movie acquired with 50 kframes/s rate and 2 {mu}s of exposure time to obtain the temporal evolutions of the emissivity fluctuations. Conditional average sampling is also applied to visualize and measure sizes of structures associated with the interchange mode. The {omega}-time and the two-dimensional k-space Fourier analysis of the reconstructed emissivity fluctuations show the same interchange mode that is detected in the {omega} and k spectra of the ion saturation current fluctuations measured by probes. Small scale turbulent plasma structures can be detected and tracked in the reconstructed emissivity movies with the spatial resolution down to 2 cm, well beyond the spatial resolution of the probe array.« less

  13. Existence of three-dimensional ideal-magnetohydrodynamic equilibria with current sheets

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Loizu, J.; Princeton Plasma Physics Laboratory, PO Box 451, Princeton, New Jersey 08543; Hudson, S. R.

    2015-09-15

    We consider the linear and nonlinear ideal plasma response to a boundary perturbation in a screw pinch. We demonstrate that three-dimensional, ideal-MHD equilibria with continuously nested flux-surfaces and with discontinuous rotational-transform across the resonant rational-surfaces are well defined and can be computed both perturbatively and using fully nonlinear equilibrium calculations. This rescues the possibility of constructing MHD equilibria with current sheets and continuous, smooth pressure profiles. The results predict that, even if the plasma acts as a perfectly conducting fluid, a resonant magnetic perturbation can penetrate all the way into the center of a tokamak without being shielded at themore » resonant surface.« less

  14. Ferroelectric Plasma Sources for Ion Beam Neutralization

    NASA Astrophysics Data System (ADS)

    Stepanov, A.; Gilson, E. P.; Grisham, L. R.; Davidson, R. C.

    2014-10-01

    A 40 keV Ar+ beam with a dimensionless perveance of 4 ×10-4 is propagated through a Ferroelectric Plasma Source (FEPS) to determine the effects of charge neutralization on the transverse beam profile. Neutralization is established 5 μs after the FEPS is triggered, and lasts between 10 and 35 μs. When the beam is fully neutralized, the profile has a Gaussian shape with a half-angle divergence of 0.87°, which is attributed to ion optics. The effects of the resistance and capacitance in the pulser circuit on the FEPS discharge are studied. The electron current emitted by the FEPS is calculated from measurements of the forward and return currents in the circuit. Electron emission typically begins 0.5 μs after the driving pulse, lasting for tens of μs, which is similar to the duration of ion beam neutralization. The total emitted charge does not depend significantly on the resistance, but depends strongly on the storage capacitance. Lowering the capacitance from 141 nF to 47 nF results in a near-complete shut-off of charge emission, although the amplitude of the applied voltage pulse is as high as when high-density plasma is produced. Overall, the data suggest that ferroelectric effects are significant in the physics of the FEPS discharge.

  15. Injector design for liner-on-target gas-puff experiments

    NASA Astrophysics Data System (ADS)

    Valenzuela, J. C.; Krasheninnikov, I.; Conti, F.; Wessel, F.; Fadeev, V.; Narkis, J.; Ross, M. P.; Rahman, H. U.; Ruskov, E.; Beg, F. N.

    2017-11-01

    We present the design of a gas-puff injector for liner-on-target experiments. The injector is composed of an annular high atomic number (e.g., Ar and Kr) gas and an on-axis plasma gun that delivers an ionized deuterium target. The annular supersonic nozzle injector has been studied using Computational Fluid Dynamics (CFD) simulations to produce a highly collimated (M > 5), ˜1 cm radius gas profile that satisfies the theoretical requirement for best performance on ˜1-MA current generators. The CFD simulations allowed us to study output density profiles as a function of the nozzle shape, gas pressure, and gas composition. We have performed line-integrated density measurements using a continuous wave (CW) He-Ne laser to characterize the liner gas density. The measurements agree well with the CFD values. We have used a simple snowplow model to study the plasma sheath acceleration in a coaxial plasma gun to help us properly design the target injector.

  16. Injector design for liner-on-target gas-puff experiments.

    PubMed

    Valenzuela, J C; Krasheninnikov, I; Conti, F; Wessel, F; Fadeev, V; Narkis, J; Ross, M P; Rahman, H U; Ruskov, E; Beg, F N

    2017-11-01

    We present the design of a gas-puff injector for liner-on-target experiments. The injector is composed of an annular high atomic number (e.g., Ar and Kr) gas and an on-axis plasma gun that delivers an ionized deuterium target. The annular supersonic nozzle injector has been studied using Computational Fluid Dynamics (CFD) simulations to produce a highly collimated (M > 5), ∼1 cm radius gas profile that satisfies the theoretical requirement for best performance on ∼1-MA current generators. The CFD simulations allowed us to study output density profiles as a function of the nozzle shape, gas pressure, and gas composition. We have performed line-integrated density measurements using a continuous wave (CW) He-Ne laser to characterize the liner gas density. The measurements agree well with the CFD values. We have used a simple snowplow model to study the plasma sheath acceleration in a coaxial plasma gun to help us properly design the target injector.

  17. Minimum magnetic curvature for resilient divertors using Compact Toroidal Hybrid geometry

    NASA Astrophysics Data System (ADS)

    Bader, A.; Hegna, C. C.; Cianciosa, M.; Hartwell, G. J.

    2018-05-01

    The properties of resilient divertors are explored using equilibria derived from Compact Toroidal Hybrid (CTH) geometries. Resilience is defined here as the robustness of the strike point patterns as the plasma geometry and/or plasma profiles are changed. The addition of plasma current in the CTH configurations significantly alters the shape of the last closed flux surface and the rotational transform profile, however, it does not alter the strike point pattern on the target plates, and hence has resilient divertor features. The limits of when a configuration transforms to a resilient configuration is then explored. New CTH-like configurations are generated that vary from a perfectly circular cross section to configurations with increasing amounts of toroidal shaping. It is found that even small amounts of toroidal shaping lead to strike point localization that is similar to the standard CTH configuration. These results show that only a small degree of three-dimensional shaping is necessary to produce a resilient divertor, implying that any highly shaped optimized stellarator will possess the resilient divertor property.

  18. Magnetic flux pumping mechanism prevents sawtoothing in 3D nonlinear MHD simulations of tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Krebs, Isabel; Jardin, Stephen C.; Guenter, Sibylle; Lackner, Karl; Hoelzl, Matthias; Strumberger, Erika; Ferraro, Nate

    2017-10-01

    3D nonlinear MHD simulations of tokamak plasmas have been performed in toroidal geometry by means of the high-order finite element code M3D-C1. The simulations are set up such that the safety factor on axis (q0) is driven towards values below unity. As reported in and the resulting asymptotic states either exhibit sawtooth-like reconnection cycling or they are sawtooth-free. In the latter cases, a self-regulating magnetic flux pumping mechanism, mainly provided by a saturated quasi-interchange instability via a dynamo effect, redistributes the central current density so that the central safety factor profile is flat and q0 1 . Sawtoothing is prevented if β is sufficiently high to allow for the necessary amount of flux pumping to counterbalance the tendency of the current density profile to centrally peak. We present the results of 3D nonlinear simulations based on specific types of experimental discharges and analyze their asymptotic behavior. A set of cases is presented where aspects of the current ramp-up phase of Hybrid ASDEX Upgrade discharges are mimicked. Another set of simulations is based on low-qedge discharges in DIII-D.

  19. Electron Bernstein Wave Studies in MST

    NASA Astrophysics Data System (ADS)

    Seltzman, Andrew; Anderson, Jay; Forest, Cary; Nonn, Paul; Thomas, Mark; Reusch, Joshua; Hendries, Eric

    2013-10-01

    The overdense condition in a RFP prevents electromagnetic waves from propagating past the extreme edge. However use of the electron Bernstein wave (EBW) has the potential to heat and drive current in the plasma. MHD simulations have demonstrated that resistive tearing mode stability is very sensitive to the gradient in the edge current density profile, allowing EBW current drive to influence and potentially stabilize tearing mode activity. Coupling between the X-mode and Bernstein waves is strongly dependent on the edge density gradient. The effects on coupling of plasma density, magnetic field strength, antenna radial position and launch polarization have been examined. Coupling as high as 90% has been observed. Construction of a 450 kw RF source is complete and initial experimental results will be reported. The power and energy of this auxiliary system should be sufficient for several scientific purposes, including verifying mode conversion, EBW propagation and absorption in high beta plasmas. Target plasmas in the 300-400 kA range will be heated near the reversal surface, potentially allowing mode control, while target plasmas in the 250 kA range will allow heating near the core, allowing better observation of heating effects. Heating and heat pulse propagation experiments are planned, as well as probing the stability of parametric decay during mode conversion, at moderate injected power. Work supported by USDOE.

  20. Ions beams and ferroelectric plasma sources

    NASA Astrophysics Data System (ADS)

    Stepanov, Anton

    Near-perfect space-charge neutralization is required for the transverse compression of high perveance ion beams for ion-beam-driven warm dense matter experiments, such as the Neutralized Drift Compression eXperiment (NDCX). Neutralization can be accomplished by introducing a plasma in the beam path, which provides free electrons that compensate the positive space charge of the ion beam. In this thesis, charge neutralization of a 40 keV, perveance-dominated Ar+ beam by a Ferroelectric Plasma Source (FEPS) is investigated. First, the parameters of the ion beam, such as divergence due to the extraction optics, charge neutralization fraction, and emittance were measured. The ion beam was propagated through the FEPS plasma, and the effects of charge neutralization were inferred from time-resolved measurements of the transverse beam profile. In addition, the dependence of FEPS plasma parameters on the configuration of the driving pulser circuit was studied to optimize pulser design. An ion accelerator was constructed that produced a 30-50 keV Ar + beam with pulse duration <300 mus and dimensionless perveance Q up to 8 x 10-4. Transverse profile measurements 33 cm downstream of the ion source showed that the dependence of beam radius on Q was consistent with space charge expansion. It was concluded that the beam was perveance-dominated with a charge neutralization fraction of approximately zero in the absence of neutralizing plasma. Since beam expansion occurred primarily due to space charge, the decrease in effective perveance due to neutralization by FEPS plasma can be inferred from the reduction in beam radius. Results on propagation of the ion beam through FEPS plasma demonstrate that after the FEPS is triggered, the beam radius decreases to its neutralized value in about 5 mus. The duration of neutralization was about 10 mus at a charging voltage VFEPS = 5.5 kV and 35 mus at VFEPS = 6.5 kV. With VFEPS = 6.5 kV, the transverse current density profile 33 cm downstream of the source had a Gaussian shape with xrms =5 mm, which corresponds to a half-angle divergence of 0.87°. The measurements show that near-perfect charge neutralization with FEPS can be attained. No loss of ion beam current was detected, indicating the absence of a neutral cloud in the region of beam propagation, which would cause beam loss to charge exchange collisions. This provides evidence in favor of using FEPS in a future Heavy Ion Fusion accelerator. The FEPS discharge was investigated based on current-voltage measurements in the pulser circuit. Different values of series resistance and storage capacitance in the pulser circuit were used. The charged particle current emitted by the FEPS into vacuum was measured from the difference in forward and return currents in the driving circuit. It was found that FEPS is an emitter of negative charge, and that electron current emission begins approximately 0.5 mus after the fast-rising high voltage pulse is applied and lasts for tens of mus. The value of the series resistance in the pulser circuit was varied to change the rise time of the voltage pulse; plasma density was expected to decrease with increasing values of resistance. However, the data showed that changing the resistance had no significant effect. The average charge emitted per shot depends strongly on the value of the storage capacitance. Lowering the capacitance from 141 nF to 47 nF resulted in a near-complete shut-off of charge emission, although the amplitude of the applied voltage pulse was as high, and rise time as short, as when high-density plasma was produced. Increasing the capacitance from 141 nF to 235 nF increased the average charge emitted per shot by a factor of 2.

  1. Reynolds stress flow shear and turbulent energy transfer in reversed field pinch configuration

    NASA Astrophysics Data System (ADS)

    Vianello, Nicola; Spolaore, Monica; Serianni, Gianluigi; Regnoli, Giorgio; Spada, Emanuele; Antoni, Vanni; Bergsåker, Henric; Drake, James R.

    2003-10-01

    The role of Reynolds Stress tensor on flow generation in turbulent fluids and plasmas is still an open question and the comprehension of its behavior may assist the understanding of improved confinement scenario. It is generally believed that shear flow generation may occur by an interaction of the turbulent Reynolds stress with the shear flow. It is also generally believed that this mechanism may influence the generation of zonal flow shears. The evaluation of the complete Reynolds Stress tensor requires contemporary measurements of its electrostatic and magnetic part: this requirement is more restrictive for Reversed Field Pinch configuration where magnetic fluctuations are larger than in tokamak . A new diagnostic system which combines electrostatic and magnetic probes has been installed in the edge region of Extrap-T2R reversed field pinch. With this new probe the Reynolds stress tensor has been deduced and its radial profile has been reconstructed on a shot to shot basis exploring differen plasma conditions. These profiles have been compared with the naturally occurring velocity flow profile, in particular during Pulsed Poloidal Current Drive experiment, where a strong variation of ExB flow radial profile has been registered. The study of the temporal evolution of Reynolds stress reveals the appearance of strong localized bursts: these are considered in relation with global MHD relaxation phenomena, which naturally occur in the core of an RFP plasma sustaining its configuration.

  2. Broadening of divertor heat flux profile with increasing number of ELM filaments in NSTX

    DOE PAGES

    Ahn, J. -W.; Maingi, R.; Canik, J. M.; ...

    2014-11-13

    Edge localized modes (ELMs) represent a challenge to future fusion devices, owing to cyclical high peak heat fluxes on divertor plasma facing surfaces. One ameliorating factor has been that the heat flux characteristic profile width has been observed to broaden with the size of the ELM, as compared with the inter-ELM heat flux profile. In contrast, the heat flux profile has been observed to narrow during ELMs under certain conditions in NSTX. Here we show that the ELM heat flux profile width increases with the number of filamentary striations observed, i.e., profile narrowing is observed with zero or very fewmore » striations. Because NSTX often lies on the long wavelength current-driven mode side of ideal MHD instabilities, few filamentary structures can be expected under many conditions. Lastly, ITER is also projected to lie on the current driven low-n stability boundary, and therefore detailed projections of the unstable modes expected in ITER and the heat flux driven in ensuing filamentary structures is needed.« less

  3. Reducing and measuring fluctuations in the MST RFP: Enhancement of energy confinement and measurement of the MHD dynamo

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Den Hartog, D.J.; Almagri, A.F.; Cekic, M.

    1996-09-01

    A three- to five-fold enhancement of the energy confinement time in a reversed-field pinch (RFP) has been achieved in the Madison Symmetric Torus (MST) by reducing the amplitude of tearing mode fluctuations responsible for anomalous transport in the core of the RFP. By applying a transient poloidal inductive electric field to flatten the current density profile, the fluctuation amplitude {tilde b}/B decreases from 1.5% to 0.8%, the electron temperature T{sub e0} increases from 250 eV to 370 eV, the ohmic input power decreases from 4.5 MW to approximately 1.5 MW, the poloidal beta {beta}{sub 0} increases from 6% to 9%,more » and the energy confinement time {tau}{sub E} increases from 1 ms to {approximately}5 ms in I{sub {phi}} = 340 kA plasmas with density {tilde n} = 1 {times} 10{sup 19} m{sup -3}. Current profile control methods are being developed for the RFP in a program to eliminate transport associated with these current-gradient-driven fluctuations. In addition to controlling the amplitude of the tearing modes, we are vigorously pursuing an understanding of the physics of these fluctuations. In particular, plasma flow, both equilibrium and fluctuating, plays a critical role in a diversity of physical phenomena in MST. The key results: 1) Edge probe measurements show that the MHD dynamo is active in low collisionality plasmas, while at high collisionality a new mechanism, the `electron diamagnetic dynamo,` is observed. 2) Core spectroscopic measurements show that the toroidal velocity fluctuations of the plasma are coherent with the large-scale magnetic tearing modes; the scalar product of these two fluctuating quantities is similar to that expected for the MHD dynamo electromotive force. 3) Toroidal plasma flow in MST exhibits large radial shear and can be actively controlled, including unlocking locked discharges, by modifying E{sub r} with a robust biased probe. 24 refs.« less

  4. Numerical band structure calculations of plasma metamaterials

    NASA Astrophysics Data System (ADS)

    Pederson, Dylan; Kourtzanidis, Konstantinos; Raja, Laxminarayan

    2015-09-01

    Metamaterials (MM) are materials engineered to display negative macroscopic permittivity and permeability. These materials allow for designed control over electromagnetic energy flow, especially at frequencies where natural materials do not interact. Plasmas have recently found application in MM as a negative permittivity component. The permittivity of a plasma depends on its electron density, which can be controlled by an applied field. This means that plasmas can be used in MM to actively control the transmission or reflection of incident waves. This work focuses on a plasma MM geometry in which microplasmas are generated in perforations in a metal plate. We characterizethis material by its band structure, which describes its interaction with incident waves. The plasma-EM interactions are obtained by coupling Maxwell's equations to a simplified plasma momentum equation. A plasma density profile is prescribed, and its effect on the band structure is investigated. The band structure calculations are typically done for static structures, whereas our current density responds to the incident waves. The resulting band structures are compared with experimental results.

  5. Dust-Particle Transport in Tokamak Edge Plasmas

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pigarov, A Y; Krasheninnikov, S I; Soboleva, T K

    2005-09-12

    Dust particulates in the size range of 10nm-100{micro}m are found in all fusion devices. Such dust can be generated during tokamak operation due to strong plasma/material-surface interactions. Some recent experiments and theoretical estimates indicate that dust particles can provide an important source of impurities in the tokamak plasma. Moreover, dust can be a serious threat to the safety of next-step fusion devices. In this paper, recent experimental observations on dust in fusion devices are reviewed. A physical model for dust transport simulation, and a newly developed code DUSTT, are discussed. The DUSTT code incorporates both dust dynamics due to comprehensivemore » dust-plasma interactions as well as the effects of dust heating, charging, and evaporation. The code tracks test dust particles in realistic plasma backgrounds as provided by edge-plasma transport codes. Results are presented for dust transport in current and next-step tokamaks. The effect of dust on divertor plasma profiles and core plasma contamination is examined.« less

  6. Passive runaway electron suppression in tokamak disruptions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Smith, H. M.; Helander, P.; Boozer, A. H.

    2013-07-15

    Runaway electrons created in disruptions pose a serious problem for tokamaks with large current. It would be desirable to have a runaway electron suppression method which is passive, i.e., a method that does not rely on an uncertain disruption prediction system. One option is to let the large electric field inherent in the disruption drive helical currents in the wall. This would create ergodic regions in the plasma and increase the runaway losses. Whether these regions appear at a suitable time and place to affect the formation of the runaway beam depends on disruption parameters, such as electron temperature andmore » density. We find that it is difficult to ergodize the central plasma before a beam of runaway current has formed. However, the ergodic outer region will make the Ohmic current profile contract, which can lead to instabilities that yield large runaway electron losses.« less

  7. Electron Bernstein Wave Research on NSTX and CDX-U

    NASA Astrophysics Data System (ADS)

    Taylor, G.; Efthimion, P. C.; Jones, B.; Bell, G. L.; Bers, A.; Bigelow, T. S.; Carter, M. D.; Harvey, R. W.; Ram, A. K.; Rasmussen, D. A.; Smirnov, A. P.; Wilgen, J. B.; Wilson, J. R.

    2003-12-01

    Studies of thermally emitted electron Bernstein waves (EBWs) on CDX-U and NSTX, via mode conversion (MC) to electromagnetic radiation, support the use of EBWs to measure the Te profile and provide local electron heating and current drive (CD) in overdense spherical torus plasmas. An X-mode antenna with radially adjustable limiters successfully controlled EBW MC on CDX-U and enhanced MC efficiency to ˜ 100%. So far the X-mode MC efficiency on NSTX has been increased by a similar technique to 40-50% and future experiments are focused on achieving ⩾ 80% MC. MC efficiencies on both machines agree well with theoretical predictions. Ray tracing and Fokker-Planck modeling for NSTX equilibria are being conducted to support the design of a 3 MW, 15 GHz EBW heating and CD system for NSTX to assist non-inductive plasma startup, current ramp up, and to provide local electron heating and CD in high β NSTX plasmas.

  8. Comment on “In-depth Plasma-Wave Heating of Dense Plasma Irradiated by Short Laser Pulses”

    DOE PAGES

    Kemp, A. J.; Sentoku, Y.

    2016-04-14

    Sherlock et al. have reported on the heating of solid density targets by collisional damping of wakefields that are driven by relativistic electron bunches generated in relativistic laser matter interaction. Analyzing collisional particle-in-cell simulations they calculate the fast electron current jf inside the plasma by adding contributions from electrons with energies greater than E cut = 50 keV; time-integrating the specific resistive energy deposition η j2f they arrive at a temperature profile and compare the result to the one 'measured' in their simulation, defined as the energy of particles with E < 30 keV; the discrepancy is due to collisionalmore » damping of wake fields (CDW). Here, we disagree with their metric of fast current, which leads to false conclusions about CDW heating being a volumetric, rather than surface effect.« less

  9. Conceptual Design of the ITER Plasma Control System

    NASA Astrophysics Data System (ADS)

    Snipes, J. A.

    2013-10-01

    The conceptual design of the ITER Plasma Control System (PCS) has been approved and the preliminary design has begun for the 1st plasma PCS. This is a collaboration of many plasma control experts from existing devices to design and test plasma control techniques applicable to ITER on existing machines. The conceptual design considered all phases of plasma operation, ranging from non-active H/He plasmas through high fusion gain inductive DT plasmas to fully non-inductive steady-state operation, to ensure that the PCS control functionality and architecture can satisfy the demands of the ITER Research Plan. The PCS will control plasma equilibrium and density, plasma heat exhaust, a range of MHD instabilities (including disruption mitigation), and the non-inductive current profile required to maintain stable steady-state scenarios. The PCS architecture requires sophisticated shared actuator management and event handling systems to prioritize control goals, algorithms, and actuators according to dynamic control needs and monitor plasma and plant system events to trigger automatic changes in the control algorithms or operational scenario, depending on real-time operating limits and conditions.

  10. Active spectroscopic measurements using the ITER diagnostic system.

    PubMed

    Thomas, D M; Counsell, G; Johnson, D; Vasu, P; Zvonkov, A

    2010-10-01

    Active (beam-based) spectroscopic measurements are intended to provide a number of crucial parameters for the ITER device being built in Cadarache, France. These measurements include the determination of impurity ion temperatures, absolute densities, and velocity profiles, as well as the determination of the plasma current density profile. Because ITER will be the first experiment to study long timescale (∼1 h) fusion burn plasmas, of particular interest is the ability to study the profile of the thermalized helium ash resulting from the slowing down and confinement of the fusion alphas. These measurements will utilize both the 1 MeV heating neutral beams and a dedicated 100 keV hydrogen diagnostic neutral beam. A number of separate instruments are being designed and built by several of the ITER partners to meet the different spectroscopic measurement needs and to provide the maximum physics information. In this paper, we describe the planned measurements, the intended diagnostic ensemble, and we will discuss specific physics and engineering challenges for these measurements in ITER.

  11. Long pulse high performance plasma scenario development for the National Spherical Torus Experiment

    NASA Astrophysics Data System (ADS)

    Kessel, C. E.; Bell, R. E.; Bell, M. G.; Gates, D. A.; Kaye, S. M.; LeBlanc, B. P.; Menard, J. E.; Phillips, C. K.; Synakowski, E. J.; Taylor, G.; Wilson, R.; Harvey, R. W.; Mau, T. K.; Ryan, P. M.; Sabbagh, S. A.

    2006-05-01

    The National Spherical Torus Experiment [Ono et al., Nucl. Fusion, 44, 452 (2004)] is targeting long pulse high performance, noninductive sustained operations at low aspect ratio, and the demonstration of nonsolenoidal startup and current rampup. The modeling of these plasmas provides a framework for experimental planning and identifies the tools to access these regimes. Simulations based on neutral beam injection (NBI)-heated plasmas are made to understand the impact of various modifications and identify the requirements for (1) high elongation and triangularity, (2) density control to optimize the current drive, (3) plasma rotation and/or feedback stabilization to operate above the no-wall β limit, and (4) electron Bernstein waves (EBW) for off-axis heating/current drive (H/CD). Integrated scenarios are constructed to provide the transport evolution and H/CD source modeling, supported by rf and stability analyses. Important factors include the energy confinement, Zeff, early heating/H mode, broadening of the NBI-driven current profile, and maintaining q(0) and qmin>1.0. Simulations show that noninductive sustained plasmas can be reached at IP=800 kA, BT=0.5 T, κ≈2.5, βN⩽5, β⩽15%, fNI=92%, and q(0)>1.0 with NBI H/CD, density control, and similar global energy confinement to experiments. The noninductive sustained high β plasmas can be reached at IP=1.0 MA, BT=0.35 T, κ≈2.5, βN⩽9, β⩽43%, fNI=100%, and q(0)>1.5 with NBI H/CD and 3.0 MW of EBW H/CD, density control, and 25% higher global energy confinement than experiments. A scenario for nonsolenoidal plasma current rampup is developed using high harmonic fast wave H/CD in the early low IP and low Te phase, followed by NBI H/CD to continue the current ramp, reaching a maximum of 480 kA after 3.4 s.

  12. Cluster electric current density measurements within a magnetic flux rope in the plasma sheet

    NASA Technical Reports Server (NTRS)

    Slavin, J. A.; Lepping, R. P.; Gjerloev, J.; Goldstein, M. L.; Fairfield, D. H.; Acuna, M. H.; Balogh, A.; Dunlop, M.; Kivelson, M. G.; Khurana, K.

    2003-01-01

    On August 22, 2001 all 4 Cluster spacecraft nearly simultaneously penetrated a magnetic flux rope in the tail. The flux rope encounter took place in the central plasma sheet, Beta(sub i) approx. 1-2, near the leading edge of a bursty bulk flow. The "time-of-flight" of the flux rope across the 4 spacecraft yielded V(sub x) approx. 700 km/s and a diameter of approx.1 R(sub e). The speed at which the flux rope moved over the spacecraft is in close agreement with the Cluster plasma measurements. The magnetic field profiles measured at each spacecraft were first modeled separately using the Lepping-Burlaga force-free flux rope model. The results indicated that the center of the flux rope passed northward (above) s/c 3, but southward (below) of s/c 1, 2 and 4. The peak electric currents along the central axis of the flux rope predicted by these single-s/c models were approx.15-19 nA/sq m. The 4-spacecraft Cluster magnetic field measurements provide a second means to determine the electric current density without any assumption regarding flux rope structure. The current profile determined using the curlometer technique was qualitatively similar to those determined by modeling the individual spacecraft magnetic field observations and yielded a peak current density of 17 nA/m2 near the central axis of the rope. However, the curlometer results also showed that the flux rope was not force-free with the component of the current density perpendicular to the magnetic field exceeding the parallel component over the forward half of the rope, perhaps due to the pressure gradients generated by the collision of the BBF with the inner magnetosphere. Hence, while the single-spacecraft models are very successful in fitting flux rope magnetic field and current variations, they do not provide a stringent test of the force-free condition.

  13. Theoretical and experimental investigation into high current hollow cathode arc attachment

    NASA Astrophysics Data System (ADS)

    Downey, Ryan T.

    This research addresses several concerns of the mechanisms controlling performance and lifetime of high-current single-channel-hollow-cathodes, the central electrode and primary life-limiting component in Magnetoplasmadynamic thrusters. Specifically covered are the trends, and the theorized governing mechanisms, seen in the discharge efficiency and power, the size of the plasma attachment to the cathode (the active zone), cathode exit plume plasma density and energy, along with plasma property distributions of the internal plasma column (the IPC) of a single-channel-hollow-cathode. Both experiment and computational modeling were employed in the analysis of the cathodes. Employing Tantalum and Tungsten cathodes (of 2, 6 and 10 mm inner diameter), experiments were conducted to measure the temperature profile of operating cathodes, the width of the active zone, the discharge voltage, power, plasma arc resistance and efficiency, with mass flow rates of 50 to 300 sccm of Argon, and discharge currents of 15 to 50 Amps. Langmuir probing was used to obtain measurements for the electron temperature, plasma density and plasma potential at the cathode exit plane (down stream tip). A computational model was developed to predict the distribution of plasma inside the cathode, based upon experimentally determined boundary conditions. It was determined that the peak cathode temperature is a function of both interior cathode density and discharge current, though the location of the peak temperature is controlled gas density but not discharge current. The active zone width was found to be an increasing function of the discharge current, but a decreasing function of the mass flow rate. The width of the active zone was found to not be controlled by the magnitude of the peak cathode wall temperature. The discharge power consumed per unit of mass throughput is seen as a decreasing function of the mass flow rate, showing the increasing efficiency of the cathode. Finally, this new understanding of the mechanisms of the plasma attachment phenomena of a single-channel-hollow-cathode were extrapolated to the multi-channel-hollow-cathode environment, to explain performance characteristics of these devices seen in previous research.

  14. Influence of the Doppler effect on radiative transfer in a spherical plasma under macroscopic motion of substance

    NASA Astrophysics Data System (ADS)

    Kosarev, N. I.

    2018-03-01

    The non-LTE radiative transfer in spherical plasma containing resonantly absorbing light ions has been studied numerically under conditions of macroscopic motion of substance. Two types of macroscopic motion were simulated: radial expansion and compression (pulsation) of spherical plasma; rotation of plasma relative to an axis of symmetry. The calculations of absorption line profile of transmitted broadband radiation and the emission line profile were performed for the optically dense plasma of calcium ions on the resonance transition with wavelength 397 nm. Numerical results predict frequency shifts in the emission line profile to red wing of the spectrum for radial expansion of the plasma and to blue wing of the spectrum for the plasma compression at an average velocity of ions along the ray of sight equal to zero. The width of the emission line profile of a rotating plasma considerably exceeds the width of the profile of the static plasma, and the shift of the central frequency of resonance transition from the resonance frequency of the static plasma gives a linear velocity of ion motion along a given ray trajectory in units of thermal velocity. Knowledge of the linear radial velocity of ions can be useful for diagnostic purposes in determining the frequency and period of rotation of optically dense plasmas.

  15. Two C-C Family Chemokines, Eotaxin and RANTES, Are Novel Independent Plasma Biomarkers for Abdominal Aortic Aneurysm.

    PubMed

    Jones, Gregory T; Phillips, L Victoria; Williams, Michael J A; van Rij, Andre M; Kabir, Tasnuva D

    2016-04-28

    Inflammation of the aortic wall is recognised as a key pathogenesis of abdominal aortic aneurysm (AAA). This study was undertaken to determine whether inflammatory cytokines could be used as biomarkers for the presence of AAA. Tissue profiles of 27 inflammatory cytokine were examined in AAA (n=14) and nonaneurysmal (n=14) aortic tissues. Three cytokines, regulated upon activation normally T-cell expressed and secreted (RANTES), eotaxin, and macrophage inflammatory protein 1 beta (MIP-1b), had increased expression in AAA, particularly within the adventitial layer of the aortic wall. Basic fibroblast growth factor (bFGF) had reduced expression in all layers of the AAA wall. Examination of the circulating plasma profiles of AAA (n=442) and AAA-free controls (n=970) suggested a (risk factor adjusted) AAA-association with eotaxin, RANTES, and high sensitivity C-reactive protein (hsCRP). A plasma inflammatory cytokine score, calculated using these three markers, suggested a strong risk association with AAA (odds ratio, 4.8; 95% CI, 3.5-6.7; P<0.0001), independent of age, sex, history of ischemic heart disease, and smoking. Contrary to reports suggesting a distinct T helper 2-associated inflammatory profile in AAA, this current study suggests a more-generalized pattern of inflammation, albeit with some potentially distinct features, including elevated plasma eotaxin and decreased plasma RANTES. In combination with hsCRP, these markers may have potential utility as AAA biomarkers. © 2016 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

  16. Space and surface charge behavior analysis of charge-eliminated polymer films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Oda, Tetsuji; Takashima, Kazunori; Ichiyama, Shinichiro

    1995-12-31

    Charge behavior of corona-charged or charge eliminated polymer films being dipped in the city water were studied. They were polytetrafluoroethylene (PTFE teflon{trademark}), polypropylene (PP), low density or high density polyethylene (LDPE or HDPE) thin films which are as grown (native) or plasma-processed. The plasma processing at low pressure was tested as antistatic processing. Charge elimination was done by being dipped in alcohol or city water. TSDC analysis and surface charge profile measurement were done for both charged and charge eliminated polymer films. Surface charge density of plasma processed polymer films just after corona charging is roughly the same as thatmore » of an original film. There is little difference between surface charge density profile of a native film and that of a plasma processed film. A large hetero current peak of TSDC was observed at room temperature for a processed film. It was found that the hetero peak disappears after charge elimination process. A pressure pulse wave method by using a pulse-driven piezoelectric PVDF polymer film as a piezoelectric actuator was newly developed to observe real space charge distribution. A little difference of internal space charge distribution between the plasma processed film and the native one after corona charging is found.« less

  17. Role of a continuous MHD dynamo in the formation of 3D equilibria in fusion plasmas

    NASA Astrophysics Data System (ADS)

    Piovesan, P.; Bonfiglio, D.; Cianciosa, M.; Luce, T. C.; Taylor, N. Z.; Terranova, D.; Turco, F.; Wilcox, R. S.; Wingen, A.; Cappello, S.; Chrystal, C.; Escande, D. F.; Holcomb, C. T.; Marrelli, L.; Paz-Soldan, C.; Piron, L.; Predebon, I.; Zaniol, B.; DIII-D, The; RFX-Mod Teams

    2017-07-01

    Stationary 3D equilibria can form in fusion plasmas via saturation of magnetohydrodynamic (MHD) instabilities or stimulated by external 3D fields. In these cases the current profile is anomalously broad due to magnetic flux pumping produced by the MHD modes. Flux pumping plays an important role in hybrid tokamak plasmas, maintaining the minimum safety factor above unity and thus removing sawteeth. It also enables steady-state hybrid operation, by redistributing non-inductive current driven near the center by electron cyclotron waves. A validated flux pumping model is not yet available, but it would be necessary to extrapolate hybrid operation to future devices. In this work flux pumping physics is investigated for helical core equilibria stimulated by external 3D fields in DIII-D hybrid plasmas. We show that flux pumping can be produced in a continuous way by an MHD dynamo emf. The same effect maintains helical equilibria in reversed-field pinch (RFP) plasmas. The effective MHD dynamo loop voltage is calculated for experimental 3D equilibrium reconstructions, by balancing Ohm’s law over helical flux surfaces, and is consistent with the expected current redistribution. Similar results are also obtained with more sophisticated nonlinear MHD simulations. The same modelling approach is applied to helical RFP states forming spontaneously in RFX-mod as the plasma current is raised above 0.8-1 MA. This comparison allows to identify the underlying physics common to tokamak and RFP: a helical core displacement modulates parallel current density along flux tubes, which requires a helical electrostatic potential to build up, giving rise to a helical MHD dynamo flow.

  18. Role of a continuous MHD dynamo in the formation of 3D equilibria in fusion plasmas

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Piovesan, P.; Bonfiglio, D.; Cianciosa, M.

    Stationary 3D equilibria can form in fusion plasmas via saturation of magnetohydrodynamic (MHD) instabilities or stimulated by external 3D fields. In these cases the current profile is anomalously broad due to magnetic flux pumping produced by the MHD modes. Flux pumping plays an important role in hybrid tokamak plasmas, maintaining the minimum safety factor above unity and thus removing sawteeth. It also enables steady-state hybrid operation, by redistributing non-inductive current driven near the center by electron cyclotron waves. A validated flux pumping model is not yet available, but it would be necessary to extrapolate hybrid operation to future devices. Inmore » this work flux pumping physics is investigated for helical core equilibria stimulated by external 3D fields in DIII-D hybrid plasmas. We show that flux pumping can be produced in a continuous way by an MHD dynamo emf. The same effect maintains helical equilibria in reversed-field pinch (RFP) plasmas. The effective MHD dynamo loop voltage is calculated for experimental 3D equilibrium reconstructions, by balancing Ohm’s law over helical flux surfaces, and is consistent with the expected current redistribution. Similar results are also obtained with more sophisticated nonlinear MHD simulations. The same modelling approach is applied to helical RFP states forming spontaneously in RFX-mod as the plasma current is raised above 0.8–1 MA. This comparison allows to identify the underlying physics common to tokamak and RFP: a helical core displacement modulates parallel current density along flux tubes, which requires a helical electrostatic potential to build up, giving rise to a helical MHD dynamo flow.« less

  19. Role of a continuous MHD dynamo in the formation of 3D equilibria in fusion plasmas

    DOE PAGES

    Piovesan, P.; Bonfiglio, D.; Cianciosa, M.; ...

    2017-04-28

    Stationary 3D equilibria can form in fusion plasmas via saturation of magnetohydrodynamic (MHD) instabilities or stimulated by external 3D fields. In these cases the current profile is anomalously broad due to magnetic flux pumping produced by the MHD modes. Flux pumping plays an important role in hybrid tokamak plasmas, maintaining the minimum safety factor above unity and thus removing sawteeth. It also enables steady-state hybrid operation, by redistributing non-inductive current driven near the center by electron cyclotron waves. A validated flux pumping model is not yet available, but it would be necessary to extrapolate hybrid operation to future devices. Inmore » this work flux pumping physics is investigated for helical core equilibria stimulated by external 3D fields in DIII-D hybrid plasmas. We show that flux pumping can be produced in a continuous way by an MHD dynamo emf. The same effect maintains helical equilibria in reversed-field pinch (RFP) plasmas. The effective MHD dynamo loop voltage is calculated for experimental 3D equilibrium reconstructions, by balancing Ohm’s law over helical flux surfaces, and is consistent with the expected current redistribution. Similar results are also obtained with more sophisticated nonlinear MHD simulations. The same modelling approach is applied to helical RFP states forming spontaneously in RFX-mod as the plasma current is raised above 0.8–1 MA. This comparison allows to identify the underlying physics common to tokamak and RFP: a helical core displacement modulates parallel current density along flux tubes, which requires a helical electrostatic potential to build up, giving rise to a helical MHD dynamo flow.« less

  20. Thermo-Rotational Instability in Plasma Disks Around Compact Objects*

    NASA Astrophysics Data System (ADS)

    Coppi, Bruno

    2008-04-01

    Differentially rotating plasma disks, around compact objects, that are imbedded in a ``seed'' magnetic field are shown to develop vertically localized ballooning modes that are driven by the combined radial gradient of the rotation frequency and the vertical gradients of the plasma density and temperature [1]. When the electron mean free path is shorter than the disk height and the (vertical) thermal conductivity can be neglected, the vertical particle flows produced by of these modes have the effect to drive the density and temperature profiles toward the ``adiabatic condition'' where ηT≡(dlnT/dz/(dlnn/dz)=2/3. Here T is the plasma temperature and n the particle density. The faster growth rates correspond to steeper temperature profiles (ηT>2/3) such as those produced by an internal (e.g. viscous) heating process. In the end, ballooning modes excited for various values of ηT can lead to the evolution of the disk into a different current carrying configuration such as a sequence of plasma rings[2].*Sponsored in part by the U.S. Department of Energy[1]B. Coppi, M.I.T. (LNS) Report HEP, 07/02, Cambridge, MA (2007), Invited Paper at the International Symposium on ``Momentum Transport in Jets, Disks and Laboratory Plasmas'', Alba, Piedmont, September 2007, to be published in Europhysical Letters (EPL, IOP)[2]B. Coppi andF. Rousseau, Ap. J., 641, 458, (2006)

  1. Prediction of plasma-facing ICRH antenna behavior via a Finite-Element solution of coupled Integral Equations

    NASA Astrophysics Data System (ADS)

    Lancellotti, V.; Milanesio, D.; Maggiora, R.; Vecchi, G.; Kyrytsya, V.

    2005-09-01

    The demand for a predictive tool to help designing ICRH antennas for fusion experiments has driven the development of codes like ICANT, RANT3D, and the early developments and further upgrades of TOPICA code. Currently, TOPICA handles the actual geometry of ICRH antennas (with their housing, etc.) as well as a realistic plasma model, including density and temperature profiles and FLR effects. Both goals have been attained by formally splitting the problem into two parts: the vacuum region around the antenna, and the plasma region inside the toroidal chamber. Field continuity and boundary conditions allow writing a set of coupled integral equations for the unknown equivalent (current) sources; finite elements are used on a triangular-cell mesh and a linear system is obtained on application of the weighted-residual solution scheme. In the vacuum region calculations are done in the spatial domain, whereas in the plasma region a spectral (wavenumber) representation of fields and currents is adopted, thus allowing a description of the plasma by a surface impedance matrix. Thanks to this approach, any plasma model can be used in principle, and at present Brambilla's FELICE code has been employed. The natural outputs of TOPICA are the induced currents on the conductors and the electric field in front of the plasma, whence the antenna circuit parameters (impedance/scattering matrices), the radiated power and the fields (at locations other than the chamber aperture) are then obtained. An accurate model of the feeding coaxial lines is also included. This paper is precisely devoted to the description of TOPICA, whereas examples of results for real-life antennas are reported in a companion paper [1] in this proceedings.

  2. Prediction of plasma-facing ICRH antenna behavior via a Finite-Element solution of coupled Integral Equations

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lancellotti, V.; Milanesio, D.; Maggiora, R.

    2005-09-26

    The demand for a predictive tool to help designing ICRH antennas for fusion experiments has driven the development of codes like ICANT, RANT3D, and the early developments and further upgrades of TOPICA code. Currently, TOPICA handles the actual geometry of ICRH antennas (with their housing, etc.) as well as a realistic plasma model, including density and temperature profiles and FLR effects. Both goals have been attained by formally splitting the problem into two parts: the vacuum region around the antenna, and the plasma region inside the toroidal chamber. Field continuity and boundary conditions allow writing a set of coupled integralmore » equations for the unknown equivalent (current) sources; finite elements are used on a triangular-cell mesh and a linear system is obtained on application of the weighted-residual solution scheme. In the vacuum region calculations are done in the spatial domain, whereas in the plasma region a spectral (wavenumber) representation of fields and currents is adopted, thus allowing a description of the plasma by a surface impedance matrix. Thanks to this approach, any plasma model can be used in principle, and at present Brambilla's FELICE code has been employed. The natural outputs of TOPICA are the induced currents on the conductors and the electric field in front of the plasma, whence the antenna circuit parameters (impedance/scattering matrices), the radiated power and the fields (at locations other than the chamber aperture) are then obtained. An accurate model of the feeding coaxial lines is also included. This paper is precisely devoted to the description of TOPICA, whereas examples of results for real-life antennas are reported in a companion paper in this proceedings.« less

  3. Gyrokinetic neoclassical study of the bootstrap current in the tokamak edge pedestal with fully non-linear Coulomb collisions

    DOE PAGES

    Hager, Robert; Chang, C. S.

    2016-04-08

    As a follow-up on the drift-kinetic study of the non-local bootstrap current in the steep edge pedestal of tokamak plasma by Koh et al. [Phys. Plasmas 19, 072505 (2012)], a gyrokinetic neoclassical study is performed with gyrokinetic ions and drift-kinetic electrons. Besides the gyrokinetic improvement of ion physics from the drift-kinetic treatment, a fully non-linear Fokker-Planck collision operator—that conserves mass, momentum, and energy—is used instead of Koh et al.'s linearized collision operator in consideration of the possibility that the ion distribution function is non-Maxwellian in the steep pedestal. An inaccuracy in Koh et al.'s result is found in the steepmore » edge pedestal that originated from a small error in the collisional momentum conservation. The present study concludes that (1) the bootstrap current in the steep edge pedestal is generally smaller than what has been predicted from the small banana-width (local) approximation [e.g., Sauter et al., Phys. Plasmas 6, 2834 (1999) and Belli et al., Plasma Phys. Controlled Fusion 50, 095010 (2008)], (2) the plasma flow evaluated from the local approximation can significantly deviate from the non-local results, and (3) the bootstrap current in the edge pedestal, where the passing particle region is small, can be dominantly carried by the trapped particles in a broad trapped boundary layer. In conclusion, a new analytic formula based on numerous gyrokinetic simulations using various magnetic equilibria and plasma profiles with self-consistent Grad-Shafranov solutions is constructed.« less

  4. Gyrokinetic neoclassical study of the bootstrap current in the tokamak edge pedestal with fully non-linear Coulomb collisions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hager, Robert; Chang, C. S.

    As a follow-up on the drift-kinetic study of the non-local bootstrap current in the steep edge pedestal of tokamak plasma by Koh et al. [Phys. Plasmas 19, 072505 (2012)], a gyrokinetic neoclassical study is performed with gyrokinetic ions and drift-kinetic electrons. Besides the gyrokinetic improvement of ion physics from the drift-kinetic treatment, a fully non-linear Fokker-Planck collision operator—that conserves mass, momentum, and energy—is used instead of Koh et al.'s linearized collision operator in consideration of the possibility that the ion distribution function is non-Maxwellian in the steep pedestal. An inaccuracy in Koh et al.'s result is found in the steepmore » edge pedestal that originated from a small error in the collisional momentum conservation. The present study concludes that (1) the bootstrap current in the steep edge pedestal is generally smaller than what has been predicted from the small banana-width (local) approximation [e.g., Sauter et al., Phys. Plasmas 6, 2834 (1999) and Belli et al., Plasma Phys. Controlled Fusion 50, 095010 (2008)], (2) the plasma flow evaluated from the local approximation can significantly deviate from the non-local results, and (3) the bootstrap current in the edge pedestal, where the passing particle region is small, can be dominantly carried by the trapped particles in a broad trapped boundary layer. In conclusion, a new analytic formula based on numerous gyrokinetic simulations using various magnetic equilibria and plasma profiles with self-consistent Grad-Shafranov solutions is constructed.« less

  5. Gyrokinetic neoclassical study of the bootstrap current in the tokamak edge pedestal with fully non-linear Coulomb collisions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hager, Robert, E-mail: rhager@pppl.gov; Chang, C. S., E-mail: cschang@pppl.gov

    As a follow-up on the drift-kinetic study of the non-local bootstrap current in the steep edge pedestal of tokamak plasma by Koh et al. [Phys. Plasmas 19, 072505 (2012)], a gyrokinetic neoclassical study is performed with gyrokinetic ions and drift-kinetic electrons. Besides the gyrokinetic improvement of ion physics from the drift-kinetic treatment, a fully non-linear Fokker-Planck collision operator—that conserves mass, momentum, and energy—is used instead of Koh et al.'s linearized collision operator in consideration of the possibility that the ion distribution function is non-Maxwellian in the steep pedestal. An inaccuracy in Koh et al.'s result is found in the steepmore » edge pedestal that originated from a small error in the collisional momentum conservation. The present study concludes that (1) the bootstrap current in the steep edge pedestal is generally smaller than what has been predicted from the small banana-width (local) approximation [e.g., Sauter et al., Phys. Plasmas 6, 2834 (1999) and Belli et al., Plasma Phys. Controlled Fusion 50, 095010 (2008)], (2) the plasma flow evaluated from the local approximation can significantly deviate from the non-local results, and (3) the bootstrap current in the edge pedestal, where the passing particle region is small, can be dominantly carried by the trapped particles in a broad trapped boundary layer. A new analytic formula based on numerous gyrokinetic simulations using various magnetic equilibria and plasma profiles with self-consistent Grad-Shafranov solutions is constructed.« less

  6. Evaluation of Plume Divergence and Facility Effects on Far-Field Faraday Probe Current Density Profiles

    DTIC Science & Technology

    2009-09-01

    elevated background pressure, compared nude Faraday probe designs, and evaluated design modifications to minimize uncertainty due to charge exchange...evaluated Faraday probe design and facility background pressure on collected ion current. A comparison of two nude Faraday probe designs concluded...140.5 Plasma potential in the region surrounding a nude Faraday probe has been measured to study the possibility of probe bias voltage acting as a

  7. Pressure profiles of plasmas confined in the field of a dipole magnet

    NASA Astrophysics Data System (ADS)

    Davis, Matthew Stiles

    Understanding the maintenance and stability of plasma pressure confined by a strong magnetic field is a fundamental challenge in both laboratory and space plasma physics. Using magnetic and X-ray measurements on the Levitated Dipole Experiment (LDX), the equilibrium plasma pressure has been reconstructed, and variations of the plasma pressure for different plasma conditions have been examined. The relationship of these profiles to the magnetohydrodynamic (MHD) stability limit, and to the enhanced stability limit that results from a fraction of energetic trapped electrons, has been analyzed. In each case, the measured pressure profiles and the estimated fractional densities of energetic electrons were qualitatively consistent with expectations of plasma stability. LDX confines high temperature and high pressure plasma in the field of a superconducting dipole magnet. The strong dipole magnet can be either mechanically supported or magnetically levitated. When the dipole was mechanically supported, the plasma density profile was generally uniform while the plasma pressure was highly peaked. The uniform density was attributed to the thermal plasma being rapidly lost along the field to the mechanical supports. In contrast, the strongly peaked plasma pressure resulted from a fraction of energetic, mirror trapped electrons created by microwave heating at the electron cyclotron resonance (ECRH). These hot electrons are known to be gyrokinetically stabilized by the background plasma and can adopt pressure profiles steeper than the MHD limit. X-ray measurements indicated that this hot electron population could be described by an energy distribution in the range 50-100 keV. Combining information from the magnetic reconstruction of the pressure profile, multi-chord interferometer measurements of the electron density profile, and X-ray measurements of the hot electron energy distribution, the fraction of energetic electrons at the pressure peak was estimated to be ˜ 35% of the total electron population. When the dipole was magnetically levitated the plasma density increased substantially because particle losses to the mechanical supports were eliminated so particles could only be lost via slower cross-field transport processes. The pressure profile was observed to be broader during levitated operation than it was during supported operation, and the pressure appeared to be contained in both a thermal population and an energetic electron population. X-ray spectra indicated that the X-rays came from a similar hot electron population during levitated and supported operation; however, the hot electron fraction was an order of magnitude smaller during levitated operation (<3% of the total electron population). Pressure gradients for both supported and levitated plasmas were compared to the MHD limit. Levitated plasmas had pressure profiles that were (i) steeper than, (ii) shallower than, or (iii) near the MHD limit dependent on plasma conditions. However, those profiles that exceeded the MHD limit were observed to have larger fractions of energetic electrons. When the dipole magnet was supported, high pressure plasmas always had profiles that exceeded the MHD interchange stability limit, but the high pressure in these plasmas appeared to arise entirely from a population of energetic trapped electrons.

  8. Radial profile of pressure in a storm ring current as a function of D st

    NASA Astrophysics Data System (ADS)

    Kovtyukh, A. S.

    2010-06-01

    Using satellite data obtained near the equatorial plane during 12 magnetic storms with amplitudes from -61 down to -422 nT, the dependences of maximum in L-profile of pressure ( L m) of the ring current (RC) on the current value of D st are constructed, and their analytical approximations are derived. It is established that function L m( D st ) is steeper on the phase of recovery than during the storm’s main phase. The form of the outer edge of experimental radial profiles of RC pressure is studied, and it is demonstrated to correspond to exponential growth of the total energy of RC particles on a given L shell with decreasing L. It is shown that during the storms’ main phase the ratio of plasma and magnetic field pressures at the RC maximum does not practically depend on the storm strength and L m value. This fact reflects resistance of the Earth’s magnetic field to RC expansion, and testifies that during storms the possibilities of injection to small L are limited for RC particles. During the storms’ recovery phase this ratio quickly increases with increasing L m, which reflects an increased fraction of plasma in the total pressure balance. It is demonstrated that function L m( D st ) is derived for the main phase of storms from the equations of drift motion of RC ions in electrical and magnetic fields, reflecting the dipole character of magnetic field and scale invariance of the pattern of particle convection near the RC maximum. For the recovery phase it is obtained from the Dessler-Parker-Sckopke relationship. The obtained regularities allow one to judge about the radial profile of RC pressure from ground-based magnetic measurements (data on the D st variation).

  9. Nontargeted LC-MS Metabolomics Approach for Metabolic Profiling of Plasma and Urine from Pigs Fed Branched Chain Amino Acids for Maximum Growth Performance.

    PubMed

    Soumeh, Elham A; Hedemann, Mette S; Poulsen, Hanne D; Corrent, Etienne; van Milgen, Jacob; Nørgaard, Jan V

    2016-12-02

    The metabolic response in plasma and urine of pigs when feeding an optimum level of branched chain amino acids (BCAAs) for best growth performance is unknown. The objective of the current study was to identify the metabolic phenotype associated with the BCAAs intake level that could be linked to the animal growth performance. Three dose-response studies were carried out to collect blood and urine samples from pigs fed increasing levels of Ile, Val, or Leu followed by a nontargeted LC-MS approach to characterize the metabolic profile of biofluids when dietary BCAAs are optimum for animal growth. Results showed that concentrations of plasma hypoxanthine and tyrosine (Tyr) were higher while concentrations of glycocholic acid, tauroursodeoxycholic acid, and taurocholic acid were lower when the dietary Ile was optimum. Plasma 3-methyl-2-oxovaleric acid and creatine were lower when dietary Leu was optimum. The optimum dietary Leu resulted in increased urinary excretion of ascorbic acid and choline and relatively decreased excretion of 2-aminoadipic acid, acetyl-dl-valine, Ile, 2-methylbutyrylglycine, and Tyr. In conclusion, plasma glycocholic acid and taurocholic acid were discriminating metabolites to the optimum dietary Ile. The optimum dietary Leu was associated with reduced plasma creatine and urinary 2-aminoadipic acid and elevated urinary excretion of ascorbic acid and choline. The optimum dietary Val had a less pronounced metabolic response reflected in plasma or urine than other BCAA.

  10. Spatial Concentrations of Silicon Atoms in RF Discharges of Silane.

    DTIC Science & Technology

    1985-02-18

    regions. These profiles were much more sensitive to plasma chemistry changes than profiles obtained from plasma emission. Experiments with nitrogen...addition demonstrated significant changes in the silicon atom profiles near the sheath boundary. Originator supplied keywords include: rf discharge, silane, plasma chemistry , silicon atom, laser-induced fluorescence.

  11. Effect of the resonant magnetic perturbation on the plasma parameters in COMPASS tokamak’s divertor region

    NASA Astrophysics Data System (ADS)

    Dimitrova, M.; Cahyna, P.; Peterka, M.; Hasan, E.; Popov, Tsv K.; Ivanova, P.; Vasileva, E.; Panek, R.; Cavalier, J.; Seidl, J.; Markovic, T.; Havlicek, J.; Dejarnac, R.; Weinzettl, V.; Hacek, P.; Tomes, M.; the COMPASS Team; the EUROfusion MST1 Team

    2018-02-01

    The resonant magnetic perturbation (RMP) has proven to be a useful way to suppress edge-localized modes that under certain conditions can damage the device by the large power fluxes carried from the bulk plasma to the wall. The effect of RMP on the L-mode plasma parameters in the divertor region of the COMPASS tokamak was studied using the array of 39 Langmuir probes embedded into the divertor target. The current-voltage (IV) probe characteristics were processed by the first-derivative probe technique to obtain the plasma potential and the electron energy distribution function (EEDF) which was approximated by a bi-Maxwellian EEDF with a low-energy (4-6 eV) fraction and a high-energy (11-35 eV) one, the both factions having similar electron density. Clear splitting was observed during the RMP pulse in the low-field-side scrape-off-layer profiles of the floating potential U fl and the ion saturation current density J sat; these two quantities were obtained both by direct continuous measurement and by evaluation of the IV characteristics of probes with swept bias. The negative peaks of U fl induced by RMP spatially overlaps with the local minima of J sat (and n e) rather than with its local maxima which is partly caused by the spatial variation of the plasma potential and partly by the changed shape of the EEDF. The effective temperature of the whole EEDF is not correlated with the negative peaks of U fl, and the profile of the parallel power flux density shows secondary maxima due to RMP which mimic those of J sat.

  12. Spectroscopic Diagnostics of Electric Fields in the Plasma of Current Sheets

    NASA Astrophysics Data System (ADS)

    Gavrilenko, Valeri; Kyrie, Natalya P.; Frank, Anna G.; Oks, Eugene

    2004-11-01

    Spectroscopic measurements of electric fields (EFs) in current sheet plasmas were performed in the CS-3D device. The device is intended to study the evolution of current sheets and the magnetic reconnection phenomena. We used the broadening of spectral lines (SLs) of HeII ions for diagnostics of EFs in the current sheet middle plane, and the broadening of SLs of HeI atoms for detection of EFs in the current sheet peripheral regions. For detection of EFs in current sheet plasma, we used SLs of HeII ions at 468.6; 320.3 and 656.0 nm, as well as SLs of HeI atoms at 667.8; 587.6; 492.2 and 447.1 nm. The latter two lines are of a special interest since their profiles include the dipole-forbidden components along with the allowed components. The experimental data have been analyzed by using the numerical calculations based on the Model Microfield Method. The maximum plasma density in the middle of the sheet was in the range (2-8) × 10^16 cm-3, the density in the peripheral regions was (1-2)×10^15 cm-3, and the strength of the quasi-one-dimensional anomalous electric fields in the peripheral regions reached the value of 100 kV/cm. Supported by CRDF, grant RU-P1-2594-MO-04; by the RFBR, grant 03-02-17282; and by the ISTC, project 2098.

  13. External heating and current drive source requirements towards steady-state operation in ITER

    NASA Astrophysics Data System (ADS)

    Poli, F. M.; Kessel, C. E.; Bonoli, P. T.; Batchelor, D. B.; Harvey, R. W.; Snyder, P. B.

    2014-07-01

    Steady state scenarios envisaged for ITER aim at optimizing the bootstrap current, while maintaining sufficient confinement and stability to provide the necessary fusion yield. Non-inductive scenarios will need to operate with internal transport barriers (ITBs) in order to reach adequate fusion gain at typical currents of 9 MA. However, the large pressure gradients associated with ITBs in regions of weak or negative magnetic shear can be conducive to ideal MHD instabilities, reducing the no-wall limit. The E × B flow shear from toroidal plasma rotation is expected to be low in ITER, with a major role in the ITB dynamics being played by magnetic geometry. Combinations of heating and current drive (H/CD) sources that sustain reversed magnetic shear profiles throughout the discharge are the focus of this work. Time-dependent transport simulations indicate that a combination of electron cyclotron (EC) and lower hybrid (LH) waves is a promising route towards steady state operation in ITER. The LH forms and sustains expanded barriers and the EC deposition at mid-radius freezes the bootstrap current profile stabilizing the barrier and leading to confinement levels 50% higher than typical H-mode energy confinement times. Using LH spectra with spectrum centred on parallel refractive index of 1.75-1.85, the performance of these plasma scenarios is close to the ITER target of 9 MA non-inductive current, global confinement gain H98 = 1.6 and fusion gain Q = 5.

  14. Multi-channel retarding field analyzer for EAST

    NASA Astrophysics Data System (ADS)

    M, HENKEL; D, HÖSCHEN; Y, LIANG; Y, LI; S, C. LIU; D, NICOLAI; N, SANDRI; G, SATHEESWARAN; N, YAN; H, X. ZHANG; the EAST, team2

    2018-05-01

    A multi-channel retarding field analyzer (MC-RFA) including two RFA modules and two Langmuir probes to measure the ion and electron temperature profiles within the scrape-off layer was developed for investigations of the interplay between magnetic topology and plasma transport at the plasma boundary. The MC-RFA probe for the stellarator W7-X and first measurements at the tokamak EAST was designed. The probe head allows simultaneous multi-channel ion temperature as well as for electron temperature measurements. The usability for radial correlation measurements of the measured ion currents is also given.

  15. Evaluation of a dried blood and plasma collection device, SampleTanker(®), for HIV type 1 drug resistance genotyping in patients receiving antiretroviral therapy.

    PubMed

    Diallo, Karidia; Lehotzky, Erica; Zhang, Jing; Zhou, Zhiyong; de Rivera, Ivette Lorenzana; Murillo, Wendy E; Nkengasong, John; Sabatier, Jennifer; Zhang, Guoqing; Yang, Chunfu

    2014-01-01

    Whatman 903 filter paper is the only filter paper that has been used for HIV drug resistance (HIVDR) genotyping in resource-limited settings. In this study, we evaluated another dried blood specimen collection device, termed SampleTanker(®) (ST), for HIVDR genotyping. Blood specimens from 123 antiretroviral therapy (ART)-experienced patients were used to prepare ST whole blood and ST plasma specimens; they were then stored at ambient temperature for 2 or 4 weeks. The remaining plasma specimens were stored at -80°C and used as frozen plasma controls. Frozen plasma viral load (VL) was determined using the Roche Amplicor HIV-1 Monitor test, v.1.5 and 50 specimens with VL ≥3.00 log10 copies/ml were genotyped using the broadly sensitive genotyping assay. The medium VL for the 50 frozen plasma specimens with VL ≥3.00 log10 was 3.58 log10 copies/ml (IQR: 3.32-4.11) and 96.0% (48/50) of them were genotyped. Comparing to frozen plasma specimens, significantly lower genotyping rates were obtained from ST whole blood (48.98% and 42.85%) and ST plasma specimens (36.0% and 36.0%) stored at ambient temperature for 2 and 4 weeks, respectively (p<0.001). Nucleotide sequence identity and resistance profile analyses between the matched frozen plasma and ST whole blood or ST plasma specimens revealed high nucleotide sequence identities and concordant resistance profiles (98.1% and 99.0%, and 96.6% and 98.9%, respectively). Our results indicate that with the current design, the ST may not be the ideal dried blood specimen collection device for HIVDR monitoring for ART patients in resource-limited settings.

  16. Simulation of the Plasma Density Evolution during Electron Cyclotron Resonance Heating at the T-10 Tokamak

    NASA Astrophysics Data System (ADS)

    Dnestrovskij, Yu. N.; Vershkov, V. A.; Danilov, A. V.; Dnestrovskij, A. Yu.; Zenin, V. N.; Lysenko, S. E.; Melnikov, A. V.; Shelukhin, D. A.; Subbotin, G. F.; Cherkasov, S. V.

    2018-01-01

    In ohmically heated (OH) plasma with low recycling, an improved particle confinement (IPC) mode is established during gas puffing. However, after gas puffing is switched off, this mode is retained only for about 100 ms, after which an abrupt phase transition into the low particle confinement (LPC) mode occurs in the entire plasma cross section. During such a transition, energy transport due to heat conduction does not change. The phase transition in OH plasma is similar to the effect of density pump-out from the plasma core, which occurs after electron cyclotron heating (ECH) is switched on. Analysis of the measured plasma pressure profiles in the T-10 tokamak shows that, after gas puffing in the OH mode is switched off, the plasma pressure profile in the IPC stage becomes more peaked and, after the peakedness exceeds a certain critical value, the IPC-LPC transition occurs. Similar processes are also observed during ECH. If the pressure profile is insufficiently peaked during ECH, then the density pump-out effect comes into play only after the critical peakedness of the pressure profile is reached. In the plasma core, the density and pressure profiles are close to the corresponding canonical profiles. This allows one to derive an expression for the particle flux within the canonical profile model and formulate a criterion for the IPC-LPC transition. The time evolution of the plasma density profile during phase transitions was simulated for a number of T-10 shots with ECH and high recycling. The particle transport coefficients in the IPC and LPC phases, as well as the dependences of these coefficients on the ECH power, are determined.

  17. LABORATORY MEASUREMENTS OF WHITE DWARF PHOTOSPHERIC SPECTRAL LINES: Hβ

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Falcon, Ross E.; Gomez, T. A.; Montgomery, M. H.

    2015-06-20

    We spectroscopically measure multiple hydrogen Balmer line profiles from laboratory plasmas to investigate the theoretical line profiles used in white dwarf (WD) atmosphere models. X-ray radiation produced at the Z Pulsed Power Facility at Sandia National Laboratories initiates plasma formation in a hydrogen-filled gas cell, replicating WD photospheric conditions. Here we present time-resolved measurements of Hβ and fit this line using different theoretical line profiles to diagnose electron density, n{sub e}, and n = 2 level population, n{sub 2}. Aided by synthetic tests, we characterize the validity of our diagnostic method for this experimental platform. During a single experiment, wemore » infer a continuous range of electron densities increasing from n{sub e} ∼ 4 to ∼30 × 10{sup 16} cm{sup −3} throughout a 120-ns evolution of our plasma. Also, we observe n{sub 2} to be initially elevated with respect to local thermodynamic equilibrium (LTE); it then equilibrates within ∼55 ns to become consistent with LTE. This supports our electron-temperature determination of T{sub e} ∼ 1.3 eV (∼15,000 K) after this time. At n{sub e} ≳ 10{sup 17} cm{sup −3}, we find that computer-simulation-based line-profile calculations provide better fits (lower reduced χ{sup 2}) than the line profiles currently used in the WD astronomy community. The inferred conditions, however, are in good quantitative agreement. This work establishes an experimental foundation for the future investigation of relative shapes and strengths between different hydrogen Balmer lines.« less

  18. Orchestrating TRANSP Simulations for Interpretative and Predictive Tokamak Modeling with OMFIT

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Grierson, B. A.; Yuan, X.; Gorelenkova, M.

    TRANSP simulations are being used in the OMFIT work- flow manager to enable a machine independent means of experimental analysis, postdictive validation, and predictive time dependent simulations on the DIII-D, NSTX, JET and C-MOD tokamaks. The procedures for preparing the input data from plasma profile diagnostics and equilibrium reconstruction, as well as processing of the time-dependent heating and current drive sources and assumptions about the neutral recycling, vary across machines, but are streamlined by using a common workflow manager. Settings for TRANSP simulation fidelity are incorporated into the OMFIT framework, contrasting between-shot analysis, power balance, and fast-particle simulations. A previouslymore » established series of data consistency metrics are computed such as comparison of experimental vs. calculated neutron rate, equilibrium stored energy vs. total stored energy from profile and fast-ion pressure, and experimental vs. computed surface loop voltage. Discrepancies between data consistency metrics can indicate errors in input quantities such as electron density profile or Zeff, or indicate anomalous fast-particle transport. Measures to assess the sensitivity of the verification metrics to input quantities are provided by OMFIT, including scans of the input profiles and standardized post-processing visualizations. For predictive simulations, TRANSP uses GLF23 or TGLF to predict core plasma profiles, with user defined boundary conditions in the outer region of the plasma. ITPA validation metrics are provided in post-processing to assess the transport model validity. By using OMFIT to orchestrate the steps for experimental data preparation, selection of operating mode, submission, post-processing and visualization, we have streamlined and standardized the usage of TRANSP.« less

  19. Orchestrating TRANSP Simulations for Interpretative and Predictive Tokamak Modeling with OMFIT

    DOE PAGES

    Grierson, B. A.; Yuan, X.; Gorelenkova, M.; ...

    2018-02-21

    TRANSP simulations are being used in the OMFIT work- flow manager to enable a machine independent means of experimental analysis, postdictive validation, and predictive time dependent simulations on the DIII-D, NSTX, JET and C-MOD tokamaks. The procedures for preparing the input data from plasma profile diagnostics and equilibrium reconstruction, as well as processing of the time-dependent heating and current drive sources and assumptions about the neutral recycling, vary across machines, but are streamlined by using a common workflow manager. Settings for TRANSP simulation fidelity are incorporated into the OMFIT framework, contrasting between-shot analysis, power balance, and fast-particle simulations. A previouslymore » established series of data consistency metrics are computed such as comparison of experimental vs. calculated neutron rate, equilibrium stored energy vs. total stored energy from profile and fast-ion pressure, and experimental vs. computed surface loop voltage. Discrepancies between data consistency metrics can indicate errors in input quantities such as electron density profile or Zeff, or indicate anomalous fast-particle transport. Measures to assess the sensitivity of the verification metrics to input quantities are provided by OMFIT, including scans of the input profiles and standardized post-processing visualizations. For predictive simulations, TRANSP uses GLF23 or TGLF to predict core plasma profiles, with user defined boundary conditions in the outer region of the plasma. ITPA validation metrics are provided in post-processing to assess the transport model validity. By using OMFIT to orchestrate the steps for experimental data preparation, selection of operating mode, submission, post-processing and visualization, we have streamlined and standardized the usage of TRANSP.« less

  20. Experimental Analysis of Pseudospark Sourced Electron Beam

    NASA Astrophysics Data System (ADS)

    Kumar, Niraj; Pal, U. N.; Verma, D. K.; Prajapati, J.; Kumar, M.; Meena, B. L.; Tyagi, M. S.; Srivastava, V.

    2011-12-01

    The pseudospark (PS) discharge has been shown to be a promising source of high brightness, high intensity electron beam pulses. The PS discharge sourced electron beam has potential applications in plasma filled microwave sources where normal material cathode cannot be used. Analysis of the electron beam profile has been done experimentally for different applied voltages. The investigation has been carried out at different axial and radial location inside the drift space in argon atmosphere. This paper represents experimentally found axial and radial variation of the beam current inside the drift tube of PS discharge based plasma cathode electron (PCE) gun. With the help of current density estimation the focusing and defocusing point of electron beam in axial direction can be analyzed.

  1. Plasma oscillations in spherical Gaussian shaped ultracold neutral plasma

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chen, Tianxing; Lu, Ronghua, E-mail: lurh@siom.ac.cn; Guo, Li

    2016-04-15

    The collective plasma oscillations are investigated in ultracold neutral plasma with a non-uniform density profile. Instead of the plane configuration widely used, we derive the plasma oscillation equations with spherically symmetric distribution and Gaussian density profile. The damping of radial oscillation is found. The Tonks–Dattner resonances of the ultracold neutral plasma with an applied RF field are also calculated.

  2. Three-dimensional simulations of plasma turbulence in the RFX-mod scrape-off layer and comparison with experimental measurements

    NASA Astrophysics Data System (ADS)

    Riva, Fabio; Vianello, Nicola; Spolaore, Monica; Ricci, Paolo; Cavazzana, Roberto; Marrelli, Lionello; Spagnolo, Silvia

    2018-02-01

    The tokamak scrape-off layer (SOL) plasma dynamics is investigated in a circular limiter configuration with a low edge safety factor. Focusing on the experimental parameters of two ohmic tokamak inner-wall limited plasma discharges in RFX-mod [Sonato et al., Fusion Eng. Des. 74, 97 (2005)], nonlinear SOL plasma simulations are performed with the GBS code [Ricci et al., Plasma Phys. Controlled Fusion 54, 124047 (2012)]. The numerical results are compared with the experimental measurements, assessing the reliability of the GBS model in describing the RFX-mod SOL plasma dynamics. It is found that the simulations are able to quantitatively reproduce the RFX-mod experimental measurements of the electron plasma density, electron temperature, and ion saturation current density (jsat) equilibrium profiles. Moreover, there are indications that the turbulent transport is driven by the same instability in the simulations and in the experiment, with coherent structures having similar statistical properties. On the other hand, it is found that the simulation results are not able to correctly reproduce the floating potential equilibrium profile and the jsat fluctuation level. It is likely that these discrepancies are, at least in part, related to simulating only the tokamak SOL region, without including the plasma dynamics inside the last close flux surface, and to the limits of applicability of the drift approximation. The turbulence drive is then identified from the nonlinear simulations and with the linear theory. It results that the inertial drift wave is the instability driving most of the turbulent transport in the considered discharges.

  3. Total Extracellular Small RNA Profiles from Plasma, Saliva, and Urine of Healthy Subjects

    PubMed Central

    Yeri, Ashish; Courtright, Amanda; Reiman, Rebecca; Carlson, Elizabeth; Beecroft, Taylor; Janss, Alex; Siniard, Ashley; Richholt, Ryan; Balak, Chris; Rozowsky, Joel; Kitchen, Robert; Hutchins, Elizabeth; Winarta, Joseph; McCoy, Roger; Anastasi, Matthew; Kim, Seungchan; Huentelman, Matthew; Van Keuren-Jensen, Kendall

    2017-01-01

    Interest in circulating RNAs for monitoring and diagnosing human health has grown significantly. There are few datasets describing baseline expression levels for total cell-free circulating RNA from healthy control subjects. In this study, total extracellular RNA (exRNA) was isolated and sequenced from 183 plasma samples, 204 urine samples and 46 saliva samples from 55 male college athletes ages 18–25 years. Many participants provided more than one sample, allowing us to investigate variability in an individual’s exRNA expression levels over time. Here we provide a systematic analysis of small exRNAs present in each biofluid, as well as an analysis of exogenous RNAs. The small RNA profile of each biofluid is distinct. We find that a large number of RNA fragments in plasma (63%) and urine (54%) have sequences that are assigned to YRNA and tRNA fragments respectively. Surprisingly, while many miRNAs can be detected, there are few miRNAs that are consistently detected in all samples from a single biofluid, and profiles of miRNA are different for each biofluid. Not unexpectedly, saliva samples have high levels of exogenous sequence that can be traced to bacteria. These data significantly contribute to the current number of sequenced exRNA samples from normal healthy individuals. PMID:28303895

  4. Temporal expression profiling of plasma proteins reveals oxidative stress in early stages of Type 1 Diabetes progression

    DOE PAGES

    Liu, Chih-Wei; Bramer, Lisa; Webb-Robertson, Bobbie-Jo; ...

    2017-10-07

    We report that blood markers other than islet autoantibodies are greatly needed to indicate the pancreatic beta cell destruction process as early as possible, and more accurately reflect the progression of Type 1 Diabetes Mellitus (T1D). To this end, a longitudinal proteomic profiling of human plasma using TMT-10plex-based LC-MS/MS analysis was performed to track temporal proteomic changes of T1D patients (n = 11) across 9 serial time points, spanning the period of T1D natural progression, in comparison with those of the matching healthy controls (n = 10). To our knowledge, the current study represents the largest (> 2000 proteins measured)more » longitudinal expression profiles of human plasma proteome in T1D research. By applying statistical trend analysis on the temporal expression patterns between T1D and controls, and Benjamini-Hochberg procedure for multiple-testing correction, 13 protein groups were regarded as having statistically significant differences during the entire follow-up period. Moreover, 16 protein groups, which play pivotal roles in response to oxidative stress, have consistently abnormal expression trend before seroconversion to islet autoimmunity. Importantly, the expression trends of two key reactive oxygen species-decomposing enzymes, Catalase and Superoxide dismutase were verified independently by ELISA.« less

  5. Temporal expression profiling of plasma proteins reveals oxidative stress in early stages of Type 1 Diabetes progression

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Liu, Chih-Wei; Bramer, Lisa; Webb-Robertson, Bobbie-Jo

    We report that blood markers other than islet autoantibodies are greatly needed to indicate the pancreatic beta cell destruction process as early as possible, and more accurately reflect the progression of Type 1 Diabetes Mellitus (T1D). To this end, a longitudinal proteomic profiling of human plasma using TMT-10plex-based LC-MS/MS analysis was performed to track temporal proteomic changes of T1D patients (n = 11) across 9 serial time points, spanning the period of T1D natural progression, in comparison with those of the matching healthy controls (n = 10). To our knowledge, the current study represents the largest (> 2000 proteins measured)more » longitudinal expression profiles of human plasma proteome in T1D research. By applying statistical trend analysis on the temporal expression patterns between T1D and controls, and Benjamini-Hochberg procedure for multiple-testing correction, 13 protein groups were regarded as having statistically significant differences during the entire follow-up period. Moreover, 16 protein groups, which play pivotal roles in response to oxidative stress, have consistently abnormal expression trend before seroconversion to islet autoimmunity. Importantly, the expression trends of two key reactive oxygen species-decomposing enzymes, Catalase and Superoxide dismutase were verified independently by ELISA.« less

  6. Optimal design of reflectometer density profile measurements using a radar systems approach (invited) (abstract)

    NASA Astrophysics Data System (ADS)

    Doyle, E. J.; Kim, K. W.; Peebles, W. A.; Rhodes, T. L.

    1997-01-01

    Reflectometry is an attractive and versatile diagnostic technique that can address a wide range of measurement needs on fusion devices. However, progress in the area of profile measurement has been hampered by the lack of a well-understood basis for the optimum design and implementation of such systems. Such a design basis is provided by the realization that reflectometer systems utilized for density profile measurements are in fact specialized forms of radar systems. In this article five criteria are introduced by which reflectometer systems can be systematically designed for optimal performance: range resolution, spatial sampling, turbulence immunity, bandwidth optimization, and the need for adaptive data processing. Many of these criteria are familiar from radar systems analysis, and are applicable to reflectometry after allowance is made for differences stemming from the nature of the plasma target. These criteria are utilized to critically evaluate current reflectometer density profile techniques and indicate improvements that can impact current and next step devices, such as ITER.

  7. Current profile redistribution driven by neutral beam injection in a reversed-field pinch

    NASA Astrophysics Data System (ADS)

    Parke, E.; Anderson, J. K.; Brower, D. L.; Den Hartog, D. J.; Ding, W. X.; Johnson, C. A.; Lin, L.

    2016-05-01

    Neutral beam injection in reversed-field pinch (RFP) plasmas on the Madison Symmetric Torus [Dexter et al., Fusion Sci. Technol. 19, 131 (1991)] drives current redistribution with increased on-axis current density but negligible net current drive. Internal fluctuations correlated with tearing modes are observed on multiple diagnostics; the behavior of tearing mode correlated structures is consistent with flattening of the safety factor profile. The first application of a parametrized model for island flattening to temperature fluctuations in an RFP allows inferrence of rational surface locations for multiple tearing modes. The m = 1, n = 6 mode is observed to shift inward by 1.1 ± 0.6 cm with neutral beam injection. Tearing mode rational surface measurements provide a strong constraint for equilibrium reconstruction, with an estimated reduction of q0 by 5% and an increase in on-axis current density of 8% ± 5%. The inferred on-axis current drive is consistent with estimates of fast ion density using TRANSP [Goldston et al., J. Comput. Phys. 43, 61 (1981)].

  8. Non-Inductively Driven Tokamak Plasmas at Near-Unity Toroidal Beta in the Pegasus Toroidal Experiment

    NASA Astrophysics Data System (ADS)

    Reusch, Joshua

    2017-10-01

    A major goal of the spherical tokamak research program is accessing a state of low internal inductance li, high elongation κ, high toroidal and normalized beta (βt and βN) , and low collisionality without solenoidal current drive. A new local helicity injection (LHI) system in the lower divertor region of the ultra-low aspect ratio Pegasus ST provides non-solenoidally driven plasmas that exhibit most of these characteristics. LHI utilizes compact, edge-localized current sources (Ainj 4 cm2, Iinj 8 kA, Vinj 1.5 kV) for plasma startup and sustainment, and can sustain more than 200 kA of plasma current. Plasma growth via LHI is enhanced by a transition from a regime of high kink-like MHD activity to one of reduced MHD activity at higher frequencies and presumably shorter wavelengths. The strong edge current drive provided by LHI results in a hollow current density profile with low li. The low aspect ratio (R0 / a 1.2) of Pegasus allows ready access to high κ and MHD stable operation at very high normalized plasma currents (IN =Ip /aBT> 15). Thomson scattering measurements indicate Te 100 eV and ne 1 ×19 m-3. The impurity Ti evolution is correlated in time with high frequency magnetic fluctuations, implying substantial reconnection ion heating is driven by the applied helicity injection. Doppler spectroscopy indicates Ti >=Te and that the anomalous ion heating scales consistently with two fluid reconnection theory. Taken together, these features provide access to very high βt plasmas. Equilibrium analyses indicate βt up to 100% and βN 6.5 is achieved. At increasingly low BT, the discharge disrupts at the no-wall ideal stability limit. In these high βt discharges, a minimum |B| well forms over 50% of the plasma volume. This unique magnetic configuration may be of interest for testing predictions of stabilizing drift wave turbulence and/or improving energetic particle confinement. This work supported by US DOE Grants DE-FG02-96ER54375 and DE-SC0006928.

  9. Te and H_α Measurements on the HT-7 Tokamak: A Collaboration between the Fusion Research Center and the Institute of Plasma Physics

    NASA Astrophysics Data System (ADS)

    Winslow, D. L.; Carter, K. R.; Chatterjee, R.; Huang, H.; Phillips, P. E.; Rowan, W. L.; Kuang, G. L.; Li, J. G.; Luo, J. R.; Wan, B. N.; Wan, Y. X.; Xie, J. K.

    1998-11-01

    A team from the Fusion Research Center at the University of Texas at Austin visited the HT-7 Tokamak at the Institute of Plasma Physics at the Chinese Academy of Sciences in Hefei, Anhui, China to study the effects of lower hybrid current drive (LHCD) in the HT-7 plasma. HT-7(HT-7 Group, Fusion Energy 1996 Vol. 1, 685 (1997).) is a medium-sized (R = 1.22 m) tokamak with superconducting toroidal field coils and long--pulse capabilities utilizing LHCD to assist ohmic current drive. Core and edge diagnostics supported by a stand-alone data acquisition system were installed for the spring 1998 campaign. The diagnostics included an ECE radiometer which allows determination of both electron temperature profiles and fluctuation levels in the core plasma and an H_α array detector for measurement of turbulence in regions not easily accessible to probes. In addition, a reciprocating Langmuir probe system was developed for use on HT-7 and should be available for the next campaign. The effects of LHCD upon fluctuation levels in the plasma will be discussed.

  10. Studies on impact of electron cyclotron wave injection on the internal transport barriers in JT-60U weak shear plasmas

    NASA Astrophysics Data System (ADS)

    Ide, S.; Takenaga, H.; Isayama, A.; Sakamoto, Y.; Yoshida, M.; Gormezano, C.

    2007-11-01

    Impact of the electron cyclotron range of frequency wave (ECRF) on the internal transport barriers (ITBs) in a weak shear (WS) plasma has been investigated in JT-60U. The fundamental O-mode ECRF of 110 GHz injected obliquely (co-current drive) from the low field side is used. It is observed that the ion temperature (Ti) ITB in a WS plasma can be degraded by ECRF. It is clarified for the first time that the degradation depends increasingly on the EC power (PEC) but decreasingly on the plasma current (Ip). Moreover it is confirmed that ECRF affects the toroidal rotation (Vt) indirectly and results in the flattening of Vt(ρ) and therefore the radial electric field (Er) profiles regardless of the direction of the target Vt(ρ), peaking co or counter direction (relative to the Ip direction). Furthermore, it is recently found that Ti and Vt in the whole ITB region are affected with almost no delay from the EC onset even with off-axis EC deposition. These results indicate that EC injection unveiled a semi-global structure that characterizes Ti ITB in a WS plasma.

  11. Experimental Study of RF Sheaths due to Shear Alfv'en Waves in the LAPD

    NASA Astrophysics Data System (ADS)

    Martin, Michael; van Compernolle, Bart; Carter, Troy; Gekelman, Walter; Pribyl, Patrick; D'Ippolito, Daniel A.; Myra, James R.

    2012-10-01

    Ion cyclotron resonance frequency (ICRF) heating is an important tool in current fusion experiments and will be an essential part of the heating power in ITER. A current limitation of ICRF heating is impurity generation through the formation of radiofrequency (RF) sheaths, both near-field (at the antenna) and far-field (e.g. in the divertor region). Far-field sheaths are thought to be generated through the direct launch of or mode conversion to shear Alfv'en waves. Shear Alfv'en waves have an electric field component parallel to the background magnetic field near the wall that drives an RF sheath.footnotetextD. A. D'Ippolito and J. R. Myra, Phys. Plasmas 19, 034504 (2012) In this study we directly launch the shear Alfv'en wave and measure the plasma potential oscillations and DC potential in the bulk plasma of the LAPD using emissive and Langmuir probes. Measured changes in the DC plasma potential can serve as an indirect measurement of the formation of an RF sheath because of rectification. These measurements will be useful in guiding future experiments to measure the plasma potential profile inside RF sheaths as part of an ongoing campaign.

  12. Electron diamagnetic effect in a magnetic nozzle on a helicon plasma thruster performance

    NASA Astrophysics Data System (ADS)

    Takahashi, Kazunori; Lafleur, Trevor; Charles, Christine; Alexander, Peter; Boswell, Rod

    2012-10-01

    The axial force, which is called thrust sometimes, imparted from a magnetically expanding helicon plasma thruster is directly measured and the results are compared with a two-dimensional fluid theory. The force component solely transmitted to the expanding field is directly measured and identified as an axial force produced by the azimuthal current due to an electron diamagnetic drift and the radial component of the applied magnetic field. In this type of configuration, plasma diffusion in magnetic field affects a spatial profile of the plasma density and the resultant axial force onto the magnetic field. It is observed that the force component onto the magnetic field increases with an increase in the magnetic field strength, simultaneously with an increase in the plasma density downstream of the source exit, which could be due to suppression of the cross field diffusion in the magnetic nozzle.

  13. A Critical Fast Ion Beta in the Madison Symmetric Torus Reversed Field Pinch

    NASA Astrophysics Data System (ADS)

    Capecchi, William J.

    The first fast-ion profile measurements have been made in a reversed-field pinch (RFP) plasma. A large population of fast-ions are deposited in the core of the Madison Symmetric Torus (MST) through use of a 1 MW neutral beam injector (NBI) giving rise to a variety of beam-driven instabilities. One such mode, the energetic-particle mode (EPM) has been shown to reduce fast-ion content in MST, evident through drops in signal levels of the advanced neutral particle analyzer (ANPA). EPMs in MST appear as bursts of magnetic fluctuations at a lab frequency of ˜100 kHz reaching peak amplitude and decaying away within 100 microseconds. A burst ensemble of the neutron data does not reveal a drop in neutron emission across a burst, implying the population of fast-ions transported by a burst constitute a small fraction of the total. The burst may also pitch-angle scatter out of the ANPA phase space or be transported to mid-radius where charge-exchange with the background neutrals or fast-ion orbit stochasticity may reduce fast-ion confinement. Data gathered from the expanded neutron diagnostic suite including a new collimated neutron detector (CiNDe) was used to reconstruct the fast-ion profile in MST and measure critical fast-ion beta quantities. Measurements were made in plasma conditions with varying magnetic field strength in order to investigate the interplay between the energetic particle (EP) drive and Alfven continuum damping. The measured values of the core fast-ion beta (7.5% (1.2%) in 300 (500) kA plasmas) are reduced from classical predictions (TRANSP predicts up to 10% core value) due to EPM activity. The frequency, magnitude, and rate of occurrence of the bursts depends on the tearing mode amplitude, Alfven continuum damping rate, fast-ion profile shape, and resonant orbit dynamics. Marginal stability was reached in both moderate- (300 kA) and high- (500 kA) current discharges, marked by sustained EPM activity and a saturated global neutron signal during NBI. The difference in profile shape is interpreted to be related to the core-most resonant tearing mode amplitude, as a larger core magnetic island moves the location of steepest fast-ion gradient further out in radius, resulting in lower confinement of the fast-ions. The reconstructed profile is more strongly peaked at lower current, consistent with a lower measured core-most tearing mode amplitude. A larger dataset at lower current gives enough temporal resolution to investigate the evolution of the fast-ion profile. The suppression of the core-most tearing mode amplitude during NBI results in a rapid and dynamically evolving fast-ion profile at the beginning of the NBI discharge and results in an initially broader profile early evolving into a more strongly peaked profile later in the NBI discharge.

  14. Observations of Intrinsic Rotation Reversal Hysteresis in Alcator C-Mod Plasmas

    NASA Astrophysics Data System (ADS)

    Cao, Norman; Rice, John; White, Anne; Baek, Seung; Chilenski, Mark; Creely, Alexander; Ennever, Paul; Hubbard, Amanda; Hughes, Jerry; Irby, Jim; Rodriguez-Fernandez, Pablo; Reinke, Matthew; Diamond, Patrick; Alcator C-Mod Team

    2016-10-01

    Intrinsic core toroidal rotation in Alcator C-Mod L-mode plasmas has been observed to spontaneously reverse direction when the normalized collisionality ν*, evaluated at the profile minimum, passes through a critical value around 0.4. In Ohmic plasmas, the low density linear Ohmic confinement regime exhibits co-current toroidal rotation, and the higher density saturated Ohmic confinement regime exhibits counter-current rotation. The reversal manifests a hysteresis loop in ν*, where the critical collisionalities for the forward and reverse transitions differ by 10-15%. There appears to be memory associated with the rotation state, since reversals which do not begin from fully saturated rotation states do not manifest this hysteresis. In addition, high-k PCI fluctuation ``wings'' (kθρs up to 1) at low density and high current appear only in the co-current rotation state, while density peaking and ``non-local'' heat transport behavior do not appear to change significantly with the rotation state. Results from fluctuation measurements and preliminary transport and stability analyses will also be presented. This work is supported by the US DOE under Grant DE-FC02-99ER54512 (C-Mod).

  15. Spheromaks, solar prominences, and Alfvén instability of current sheets

    NASA Astrophysics Data System (ADS)

    Bellan, P. M.; Yee, J.; Hansen, J. F.

    2001-06-01

    Three related efforts underway at Caltech are discussed: experimental studies of spheromak formation, experimental simulation of solar prominences, and Alfvén wave instability of current sheets. Spheromak formation has been studied by using a coaxial magnetized plasma gun to inject helicity-bearing plasma into a very large vacuum chamber. The spheromak is formed without a flux conserver and internal λ profiles have been measured. Spheromak-based technology has been used to make laboratory plasmas having the topology and dynamics of solar prominences. The physics of these structures is closely related to spheromaks (low β, force-free, relaxed state equilibrium) but the boundary conditions and symmetry are different. Like spheromaks, the equilibrium involves a balance between hoop forces, pinch forces, and magnetic tension. It is shown theoretically that if a current sheet becomes sufficiently thin (of the order of the ion skin depth or smaller), it becomes kinetically unstable with respect to the emission of Alfvén waves and it is proposed that this wave emission is an important aspect of the dynamics of collisionless reconnection.

  16. Comparison of resistive MHD simulations and experimental CHI discharges in NSTX

    NASA Astrophysics Data System (ADS)

    Hooper, E. B.; Sovinec, C. R.; Raman, R.; Fatima, F.

    2013-10-01

    Resistive MHD simulations using NIMROD simulate CHI discharges for NSTX startup plasmas. Quantitative comparison with experiment ensures that the simulation physics includes a minimal physics set needed to extend the simulations to new experiments, e.g. NSTX-U. Important are time-varying vacuum magnetic field, ohmic heating, thermal transport, impurity radiation, and spatially-varying plasma parameters including density. Equilibria are compared with experimental injector currents, voltages and parameters including toroidal current, photographs of emitted light and measurements of midplane temperature profiles, radiation and surface heating. Initial results demonstrate that adjusting impurity radiation and cross-field transport yields temperatures and injected-current channel widths similar to experiment. These determine the plasma resistance, feeding back to the impedance on the injector power supply. Work performed under the auspices of the U.S. Department of Energy under contracts DE-AC52-07NA27344 at LLNL and DE-AC02-09CH11466 at PPPL, and grants DE-FC02-05ER54813 at PSI Center (U. Wisc.) and DOE-FG02-12ER55115 (at Princeton U.).

  17. Observation of Trapped-Electron Mode Microturbulence in Improved Confinement Reversed-Field Pinch Plasmas

    NASA Astrophysics Data System (ADS)

    Duff, James R.

    This is a dissertation for the completion of a Doctorate of Philosophy in Physics degree granted at the University of Wisconsin-Madison. Density fluctuations in the large-density-gradient region of improved confinement Madison Sym- metric Torus (MST) RFP plasmas exhibit multiple features that are characteristic of the trapped- electron mode (TEM). In fusion relevant plasmas, thermal transport is a key avenue of research in order to achieve a burning plasma. In the reversed field pinch (RFP) magnetic geometry, the dy- namics of conventional plasma discharges are primarily governed by magnetic stochasticity stem- ming from multiple long-wavelength tearing modes, that sustain the RFP discharge but have an adverse effect on the plasma confinement. Using inductive current profile control, these tearing modes are reduced, and global confinement is increased to that expected for comparable tokamak plasma. Under these conditions with certain plasma equilibria, new short-wavelength fluctuations distinct from global tearing modes appear in the spectrum at frequencies f 50 kHz that have normalized perpendicular wavenumbers k⊥rhos ≤ 0.2, and propagate in the electron diamagnetic drift direction. By adjusting the plasma current or the inductive suppression, there are observable variations in the spectral features. They exhibit a critical-gradient threshold, and the fluctuation amplitude increases with a local density gradient dependent parameter. These characteristics are consistent with the predictions of unstable TEMs based on gyrokinetic analysis using the GENE code. This thesis represents the first observation and description of TEM-like instabilities in the RFP geometry.

  18. Three-dimensional magnetohydrodynamic equilibrium of quiescent H-modes in tokamak systems

    NASA Astrophysics Data System (ADS)

    Cooper, W. A.; Graves, J. P.; Duval, B. P.; Sauter, O.; Faustin, J. M.; Kleiner, A.; Lanthaler, S.; Patten, H.; Raghunathan, M.; Tran, T.-M.; Chapman, I. T.; Ham, C. J.

    2016-06-01

    Three dimensional free boundary magnetohydrodynamic equilibria that recover saturated ideal kink/peeling structures are obtained numerically. Simulations that model the JET tokamak at fixed < β > =1.7% with a large edge bootstrap current that flattens the q-profile near the plasma boundary demonstrate that a radial parallel current density ribbon with a dominant m /n  =  5/1 Fourier component at {{I}\\text{t}}=2.2 MA develops into a broadband spectrum when the toroidal current I t is increased to 2.5 MA.

  19. Plasma Profile Measurements for Laser Fusion Research with the Nike KrF Laser

    NASA Astrophysics Data System (ADS)

    Oh, Jaechul; Weaver, J. L.; Serlin, V.; Obenschain, S. P.

    2015-11-01

    The grid image refractometer of the Nike laser facility (Nike-GIR) has demonstrated the capability of simultaneously measuring electron density (ne) and temperature (Te) profiles of coronal plasma. For laser plasma instability (LPI) research, the first Nike-GIR experiment successfully measured the plasma profiles in density regions up to ne ~ 4 ×1021 cm-3 (22% of the critical density for 248 nm light of Nike) using an ultraviolet probe laser (λp = 263 nm). The probe laser has been recently replaced with a shorter wavelength laser (λp = 213 nm, a 5th harmonic of the Nd:YAG laser) to diagnose a higher density region. The Nike-GIR system is being further extended to measure plasma profiles in the on-going experiment using 135°-separated Nike beam arrays for the cross-beam energy transfer (CBET) studies. We present an overview of the extended Nike-GIR arrangements and a new numerical algorithm to extract self-consistant plasma profiles with the measured quantities. Work supported by DoE/NNSA.

  20. Effect of Selenium Supplementation on Glycemic Control and Lipid Profiles in Patients with Diabetic Nephropathy.

    PubMed

    Bahmani, Fereshteh; Kia, Mahsa; Soleimani, Alireza; Asemi, Zatollah; Esmaillzadeh, Ahmad

    2016-08-01

    To our knowledge, data on the effects of selenium supplementation on glycemic control and lipid concentrations in patients with diabetic nephropathy (DN) are scarce. The current study was done to determine the effects of selenium supplementation on glycemic control and lipid concentrations in patients with DN. This was a randomized double-blind placebo-controlled clinical trial in which 60 patients with DN were randomly allocated into two groups to receive either 200 μg of selenium supplements (n = 30) or placebo (n = 30) daily for 12 weeks. Blood sampling was performed for the quantification of glycemic indicators and lipid profiles at the onset of the study and after 12 weeks of intervention. Selenium supplementation for 12 weeks resulted in a significant decrease in serum insulin levels (P = 0.01), homeostasis model of assessment-estimated insulin resistance (HOMA-IR) (P = 0.02), homeostasis model of assessment-estimated B cell function (HOMA-B) (P = 0.009) and a significant rise in plasma glutathione peroxidase (GPx) (P = 0.001) compared with the placebo. Taking selenium supplements had no significant effects on fasting plasma glucose (FPG), quantitative insulin sensitivity check index (QUICKI) and lipid profiles compared with the placebo. Overall, our study demonstrated that selenium supplementation for 12 weeks among patients with DN had beneficial effects on plasma GPx, serum insulin levels, HOMA-IR, and HOMA-B, while it did not affect FPG, QUICKI, and lipid profiles.

  1. Cusped magnetic field mercury ion thruster. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Beattie, J. R.

    1976-01-01

    The importance of a uniform current density profile in the exhaust beam of an electrostatic ion thruster is discussed in terms of thrust level and accelerator system lifetime. A residence time approach is used to explain the nonuniform beam current density profile of the divergent magnetic field thruster. Mathematical expressions are derived which relate the thruster discharge power loss, propellant utilization, and double to single ion density ratio to the geometry and plasma properties of the discharge chamber. These relationships are applied to a cylindrical discharge chamber model of the thruster. Experimental results are presented for a wide range of the discharge chamber length. The thruster designed for this investigation was operated with a cusped magnetic field as well as a divergent field geometry, and the cusped field geometry is shown to be superior from the standpoint of beam profile uniformity, performance, and double ion population.

  2. The front end test stand high performance H- ion source at Rutherford Appleton Laboratory.

    PubMed

    Faircloth, D C; Lawrie, S; Letchford, A P; Gabor, C; Wise, P; Whitehead, M; Wood, T; Westall, M; Findlay, D; Perkins, M; Savage, P J; Lee, D A; Pozimski, J K

    2010-02-01

    The aim of the front end test stand (FETS) project is to demonstrate that chopped low energy beams of high quality can be produced. FETS consists of a 60 mA Penning Surface Plasma Ion Source, a three solenoid low energy beam transport, a 3 MeV radio frequency quadrupole, a chopper, and a comprehensive suite of diagnostics. This paper details the design and initial performance of the ion source and the laser profile measurement system. Beam current, profile, and emittance measurements are shown for different operating conditions.

  3. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Steepening of the density profile under the action of a ponderomotive force during isothermal planar plasma expansion

    NASA Astrophysics Data System (ADS)

    Garanin, Sergey G.; Kir'yanov, Yu F.; Kochemasov, G. G.

    1990-06-01

    A theoretical investigation is reported of the deformation of the density profile of a plasma by a ponderomotive force under transient conditions. Initially, the structure of the density profile near the critical point coincides exactly with the solution of the steady-state problem. Plasma expansion is accompanied by growth of a spiky instability in the form of stimulated Brillouin scattering.

  4. Recent results from the electron cyclotron heated plasmas in Tokamak à Configuration Variable (TCV)

    NASA Astrophysics Data System (ADS)

    Henderson, M. A.; Alberti, S.; Angioni, C.; Arnoux, G.; Behn, R.; Blanchard, P.; Bosshard, P.; Camenen, Y.; Coda, S.; Condrea, I.; Goodman, T. P.; Hofmann, F.; Hogge, J.-Ph.; Karpushov, A.; Manini, A.; Martynov, An.; Moret, J.-M.; Nikkola, P.; Nelson-Melby, E.; Pochelon, A.; Porte, L.; Sauter, O.; Ahmed, S. M.; Andrèbe, Y.; Appert, K.; Chavan, R.; Degeling, A.; Duval, B. P.; Etienne, P.; Fasel, D.; Fasoli, A.; Favez, J.-Y.; Furno, I.; Horacek, J.; Isoz, P.; Joye, B.; Klimanov, I.; Lavanchy, P.; Lister, J. B.; Llobet, X.; Magnin, J.-C.; Marlétaz, B.; Marmillod, P.; Martin, Y.; Mayor, J.-M.; Mylnar, J.; Paris, P. J.; Perez, A.; Peysson, Y.; Pitts, R. A.; Raju, D.; Reimerdes, H.; Scarabosio, A.; Scavino, E.; Seo, S. H.; Siravo, U.; Sushkov, A.; Tonetti, G.; Tran, M. Q.; Weisen, H.; Wischmeier, M.; Zabolotsky, A.; Yhuang, G.

    2003-05-01

    In noninductively driven discharges, 0.9 MW second harmonic (X2) off-axis co-electron cyclotron current drive deposition is combined with 0.45 MW X2 central heating to create an electron internal transport barrier (eITB) in steady plasma conditions resulting in a 1.6-fold increase of the confinement time (τEe) over ITER-98L-mode scaling. The eITB is associated with a reversed shear current profile enhanced by a large bootstrap current fraction (up to 80%) and is sustained for up to 10 current redistribution times. A linear dependence of the confinement improvement on the product of the global shear reversal factor (q0/qmin) and the reversed shear volume (ρq-min2) is shown. In other discharges heated with X2 the sawteeth are destabilized (respectively stabilized) when heating just inside (respectively outside) the q=1 surface. Control of the sawteeth may allow the avoidance of neoclassical tearing modes that can be seeded by the sawtooth instability. Results on H-mode and highly elongated plasmas using the newly completed third harmonic (X3) system and achieving up to 100% absorption are also discussed, along with comparison of experimental results with the TORAY-GA ray tracing code [K. Matsuda, IEEE Trans. Plasma Sci. PS-17, 6 (1989); R. H. Cohen, Phys. Fluids 30, 2442 (1987)].

  5. Carbon impurities behavior and its impact on ion thermal confinement in high-ion-temperature deuterium discharges on the Large Helical Device

    NASA Astrophysics Data System (ADS)

    Mukai, K.; Nagaoka, K.; Takahashi, H.; Yokoyama, M.; Murakami, S.; Nakano, H.; Ida, K.; Yoshinuma, M.; Seki, R.; Kamio, S.; Fujiwara, Y.; Oishi, T.; Goto, M.; Morita, S.; Morisaki, T.; Osakabe, M.; LHD Experiment Group1, the

    2018-07-01

    The behavior of carbon impurities in deuterium plasmas and its impact on thermal confinement were investigated in comparison with hydrogen plasmas in the Large Helical Device (LHD). Deuterium plasma experiments have been started in the LHD and high-ion-temperature plasmas with central ion temperature (T i) of 10 keV were successfully obtained. The thermal confinement improvement could be sustained for a longer time compared with hydrogen plasmas. An isotope effect was observed in the time evolution of the carbon density profiles. A transiently peaked profile was observed in the deuterium plasmas due to the smaller carbon convection velocity and diffusivity in the deuterium plasmas compared with the hydrogen plasmas. The peaked carbon density profile was strongly correlated to the ion thermal confinement improvement. The peaking of the carbon density profile will be one of the clues to clarify the unexplained mechanisms for the formations of ion internal transport barrier and impurity hole on LHD. These results could also lead to a better understanding of the isotope effect in the thermal confinement in torus plasma.

  6. Non-stationary self-focusing of intense laser beam in plasma using ramp density profile

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Habibi, M.; Ghamari, F.

    2011-10-15

    The non-stationary self-focusing of high intense laser beam in under-dense plasma with upward increasing density ramp is investigated. The obtained results show that slowly increasing plasma density ramp is very important in enhancing laser self-focusing. Also, the spot size oscillations of laser beam in front and rear of the pulse for two different density profiles are shown. We have selected density profiles that already were used by Sadighi-Bonabi et al.[Phys. Plasmas 16, 083105 (2009)]. Ramp density profile causes the laser beam to become more focused and penetrations deeps into the plasma by reduction of diffraction effects. Our computations show moremore » reliable results in comparison to the previous works.« less

  7. Lower Hybrid Wave Induced SOL Emissivity Variation at High Density on the Alcator C-Mod Tokamak

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Faust, I.; Terry, J. L.; Reinke, M. L.

    Lower Hybrid Current Drive (LHCD) in the Alcator C-Mod tokamak provides current profile control for the generation of Advanced Tokamak (AT) plasmas. Non-thermal electron bremsstrahlung emission decreases dramatically at n-bar{sub e}>1{center_dot}10{sup 20}[m{sup -3}] for diverted discharges, indicating low current drive efficiency. It is suggested that Scrape-Off-Layer (SOL) collisional absorption of LH waves is the cause for the absence of non-thermal electrons at high density. VUV and visible spectroscopy in the SOL provide direct information on collision excitation processes. Deuterium Balmer-, Lyman- and He-I transition emission measurements were used for initial characterization of SOL electron-neutral collisional absorption. Data from Helium andmore » Deuterium LHCD discharges were characterized by an overall increase in the emissivity as well as an outward radial shift in the emissivity profile with increasing plasma density and applied LHCD power. High-temperature, high-field (T{sub e} = 5keV,B{sub t} = 8T) helium discharges at high density display increased non-thermal signatures as well as reduced SOL emissivity. Variations in emissivity due to LHCD were seen in SOL regions not magnetically connected to the LH Launcher, indicating global SOL effects due to LHCD.« less

  8. O-regime dynamics and modeling in Tore Supra

    NASA Astrophysics Data System (ADS)

    Turco, F.; Giruzzi, G.; Imbeaux, F.; Udintsev, V. S.; Artaud, J. F.; Barana, O.; Dumont, R.; Mazon, D.; Ségui, J.-L.

    2009-06-01

    The regime of nonlinear temperature oscillations (O-regime), characteristic of noninductive discharges on Tore Supra [Équipe Tore Supra, Proceedings of the 12th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Nice, France, 1988 (International Atomic Energy Agency, Vienna, 1989), Vol. 1, p. 9], is investigated in its triggering and suppressing mechanism. This regime can be described by two nonlinearly coupled equations for the current density j(r ) and the electron temperature Te(r) where the equation coefficients are functions of j and Te themselves. Both the integrated modeling code CRONOS [V. Basiuk et al., Nucl. Fusion 43, 822 (2003)] and a two-patch predator-prey system with diffusion and noise have been used and results have been compared to the experimental observations of the O-regime. A database of discharges is analyzed which features monotonic, flat, and reversed safety factor (q) profiles in order to characterize the action of external actuators on the regime dynamics with the widest generality. Electron cyclotron current drive and neutral beam injections have been used in order to induce localized perturbations in the total current profile j(r ) as well as to change the plasma confinement conditions in the central region. Magnetic shear perturbations and modifications of the heat transport turn out to be the central parameters governing the dynamics of the O-regime.

  9. M = +1, ± 1 and ± 2 mode helicon wave excitation.

    NASA Astrophysics Data System (ADS)

    Kim, J.-H.; Yun, S.-M.; Chang, H.-Y.

    1996-11-01

    The characteristics of M=+1, ± 1 and ± 2 modes helicon wave excited using a solenoid antenna, Nagoya type III and quadrupole antenna respectively are first investigated. The solenoid antenna is constructed by winding a copper cable on a quartz discharge tube. Two dimensional cross-field measurements of ArII optical emission induced by hot electrons are made to investigate RF power deposition: Components of the wave magnetic field measured with a single-turn, coaxial magnetic probe were compared with the field patterns computed for M=+1, ± 1 and ± 2 modes. The M=+1 mode plasma produced by the solenoid antenna has a cylindrical high intensity plasma column, which center is empty. This cylindrical high intensity column results from the rotation of the cross-sectional electric field pattern (right hand circularly polarization). The radial plasma density profile has a peak at r=2.5cm with axisymmetry. It has been found that the radial profile of the plasma density is in good agreement with the computed power deposition profile. The radial profiles of the wave magnetic field are in good agreement with computations. The plasma excited by Nagoya type III antenna has two high intensity columns which results from the linear combination of M=+1 and -1 modes (i.e. plane polarization). The radial plasma density profile is in good agreement with emission intensity profile of ArII line (488nm). The plasma excited by quadrupole antenna has four high intensity columns which results from the linear combination of M=+2 and -2 modes (i.e. plane polarization). In the M=± 2 modes, the radial plasma density profile is also in good agreement with emission intensity profile of ArII line.

  10. Eigenmode electric field profiles in cylindrical plasmas

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Litwin, C.; Hershkowitz, N.

    Electric field profiles of plasma column eigenmodes in the ion-cyclotron range of frequencies are discussed. Step and parabolic density profiles are compared. The role of temperature and Alfven resonance is analyzed.

  11. Overview of MST Results and Plans

    NASA Astrophysics Data System (ADS)

    Sarff, J. S.

    2008-11-01

    Improved confinement with high beta has been established in MST over its full range of plasma current capability using transient inductive current profile control. Both thermal electron and ion confinement are increased, and energetic electrons are observed to 100 keV. The global energy confinement time is 12 ms at high current and high temperature (Te=2 keV, Ti =1 keV), with βtot=10% (only Ohmic heating). Maximum βtot=26% is attained at lower current and temperature with D2 pellet injection, without evidence of hard-beta-limit phenomena. Momentum transport associated with MHD tearing shows the fascinating behavior that the Maxwell and Reynolds turbulent stresses are both large but oppositely directed in sawtooth magnetic relaxation events. Momentum is transported rapidly in these events, presumably through the imbalance in the stresses. Electron temperature fluctuations associated with MHD tearing are measured using a multi-point, multi-pulse Thomson scattering diagnostic. A 5-250 kHz pulse-burst laser is under construction to extend the Thomson capability to high frequency. Lower hybrid and electron Bernstein wave injection are under development to provide more sustained current profile control and heating. X-ray emission from the plasma is observed for both waves at 175 kW injected power. Substantial new experimental capability will be provided by a recently installed programmable power supply for the toroidal field, a new 1 MW, 20 ms neutral beam injection system, and upgraded OFCD system. Supported by U.S. DoE and NSF.

  12. Plasma chemistry study of PLAD processes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Qin Shu; Brumfield, Kyle; Liu, Lequn Jennifer

    2012-11-06

    Plasma doping (PLAD) shows very different impurity profiles compared to the conventional beam-line-based ion implantations due to its non-mass separation property and plasma environment. There is no simulation for PLAD process so far due to a lack of a dopant profile model. Several factors determine impurity profiles of PLAD process. The most significant factors are: plasma chemistry and deposition/etching characteristics of multi-ion species plasmas. In this paper, we present plasma chemistry and deposition/etching characteristics of PLAD processes versus co-gas dilutions. Four dopant plasmas including B{sub 2}H{sub 6}, BF{sub 3}, AsH{sub 3}, and PH{sub 3}, and two non-dopant plasmas including CH{submore » 4} and GeH{sub 4} are studied and demonstrated.« less

  13. The Mochi LabJet Experiment for Measurements of Canonical Helicity Injection in a Laboratory Astrophysical Jet

    NASA Astrophysics Data System (ADS)

    You, Setthivoine; von der Linden, Jens; Sander Lavine, Eric; Carroll, Evan Grant; Card, Alexander; Quinley, Morgan; Azuara-Rosales, Manuel

    2018-06-01

    The Mochi device is a new pulsed power plasma experiment designed to produce long, collimated, stable, magnetized plasma jets when set up in the LabJet configuration. The LabJet configuration aims to simulate an astrophysical jet in the laboratory by mimicking an accretion disk threaded by a poloidal magnetic field with concentric planar electrodes in front of a solenoidal coil. The unique setup consists of three electrodes, each with azimuthally symmetric gas slits. Two of the electrodes are biased independently with respect to the third electrode to control the radial electric field profile across the poloidal bias magnetic field. This design approximates a shear azimuthal rotation profile in an accretion disk. The azimuthally symmetric gas slits provide a continuously symmetric mass source at the footpoint of the plasma jet, so any azimuthal rotation of the plasma jet is not hindered by a discrete number of gas holes. The initial set of diagnostics consists of current Rogowski coils, voltage probes, magnetic field probe arrays, an interferometer and ion Doppler spectroscopy, supplemented by a fast ion gauge and a retarding grid energy analyzer. The measured parameters of the first plasmas are ∼1022 m‑3, ∼0.4 T, and 5–25 eV, with velocities of ∼20–80 km s‑1. The combination of a controllable electric field profile, a flared poloidal magnetic field, and azimuthally symmetric mass sources in the experiment successfully produces short-lived (∼10 μs, ≳5 Alfvén times) collimated magnetic jets with a ∼10:1 aspect ratio and long-lived (∼100 μs, ≳40 Alfvén times) flow-stabilized, collimated, magnetic jets with a ∼30:1 aspect ratio.

  14. Producing High-Performance, Stable, Sheared-Flow Z-Pinches in the FuZE project

    NASA Astrophysics Data System (ADS)

    Golingo, R. P.; Shumlak, U.,; Nelson, B. A.; Claveau, E. L.; Forbes, E. G.; Stepanov, A. D.; Weber, T. R.; Zhang, Y.; McLean, H. S.; Tummel, K. K.; Higginson, D. P.; Schmidt, A. E.; University of Washington (UW) Collaboration; Lawrence Livermore National Laboratory (LLNL) Collaboration

    2017-10-01

    The Fusion Z-Pinch Experiment (FuZE) has made significant strides towards generating high-performance, stable Z-pinch plasmas with goals of ne = 1018 cm-3 and T =1 keV. The Z-pinch plasmas are stabilized with a sheared axial flow that is driven by a coaxial accelerator. The new FuZE device has been constructed and reproduces the major scientific achievements the ZaP project at the University of Washington; ne = 1016 cm-3,T = 100 eV, r<1 cm, and tstable >20 μs. These parameters are measured with an array of magnetic field probes, spectroscopy, and fast framing cameras. The plasma parameters are achieved using a small fraction of the maximum energy storage and gas injection capability of the FuZE device. Higher density, ne = 5×1017 cm-3, and temperature, T = 500 eV, Z-pinch plasmas are formed by increasing the pinch current. At the higher voltages and currents, the ionization rates in the accelerator increase. By modifying the neutral gas profile in the accelerator, the plasma flow from the accelerator is maintained, driving the flow shear. Formation and sustainment of the sheared-flow Z-pinch plasma will be discussed. Experimental data demonstrating high performance plasmas in a stable Z-pinches will be shown. This work is supported by an award from US ARPA-E.

  15. Weight loss is associated with plasma free amino acid alterations in subjects with metabolic syndrome

    PubMed Central

    Tochikubo, O; Nakamura, H; Jinzu, H; Nagao, K; Yoshida, H; Kageyama, N; Miyano, H

    2016-01-01

    Objectives: The prevalence of metabolic syndrome is increasing worldwide, especially in Asian populations. Early detection and effective intervention are vital. Plasma free amino acid profile is a potential biomarker for the early detection for lifestyle-related diseases. However, little is known about whether the altered plasma free amino acid profiles in subjects with metabolic syndrome are related to the effectiveness of dietary and exercise interventions. Methods: Eighty-five Japanese subjects who fulfilled the Japanese diagnostic criteria for metabolic syndrome were enrolled in a 3-month diet and exercise intervention. The plasma free amino acid concentrations and metabolic variables were measured, and the relationships between plasma free amino acid profiles, metabolic variables and the extent of body weight reduction were investigated. Those who lost more than 3% of body weight were compared with those who lost less than 3%. Results: Baseline levels of most amino acids in the subset that went on to lose <3% body weight were markedly lower compared with the counterpart, although both groups showed similar proportional pattern of plasma amino acid profiles. The weight loss induced by the diet and exercise intervention normalized plasma free amino acid profiles. For those with a high degree of weight loss, those changes were also associated with improvement in blood pressure, triglyceride and hemoglobin A1c levels. Conclusions: These data suggest that among Japanese adults meeting the criteria for metabolic syndrome, baseline plasma free amino acid profiles may differ in ways that predict who will be more vs less beneficially responsive to a standard diet and exercise program. Plasma free amino acid profiles may also be useful as markers for monitoring the risks of developing lifestyle-related diseases and measuring improvement in physiological states. PMID:26926588

  16. Some diagnostic interpretations from railgun plasma profile experiments

    NASA Astrophysics Data System (ADS)

    Stainsby, D. F.; Bedford, A. J.

    1984-03-01

    Some aspects of a railgun experimental series to investigate plasma profiles are reviewed. Certain diagnostic records clearly show plasma leakage past the projectile, and correspondence between various in-bore events and muzzle voltage. A muzzle flash detector is shown to have a useful role as a plasma diagnostic tool.

  17. Temperature profile determination in an absorbing plasma.

    NASA Technical Reports Server (NTRS)

    Usher, J. L.; Campbell, H. D.

    1972-01-01

    A new method has been developed to determine the temperature profile of an optically-non-thin plasma. The technique is essentially an extension of the brightness-emissivity method to the case of a cylindrically-symmetric plasma.

  18. Theory-based transport simulations of TFTR L-mode temperature profiles

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bateman, G.

    1992-03-01

    The temperature profiles from a selection of Tokamak Fusion Test Reactor (TFTR) L-mode discharges (17{ital th} {ital European} {ital Conference} {ital on} {ital Controlled} {ital Fusion} {ital and} {ital Plasma} {ital Heating}, Amsterdam, 1990 (EPS, Petit-Lancy, Switzerland, 1990, p. 114)) are simulated with the 1 (1)/(2) -D baldur transport code (Comput. Phys. Commun. {bold 49}, 275 (1988)) using a combination of theoretically derived transport models, called the Multi-Mode Model (Comments Plasma Phys. Controlled Fusion {bold 11}, 165 (1988)). The present version of the Multi-Mode Model consists of effective thermal diffusivities resulting from trapped electron modes and ion temperature gradient ({eta}{submore » {ital i}}) modes, which dominate in the core of the plasma, together with resistive ballooning modes, which dominate in the periphery. Within the context of this transport model and the TFTR simulations reported here, the scaling of confinement with heating power comes from the temperature dependence of the {eta}{sub {ital i}} and trapped electron modes, while the scaling with current comes mostly from resistive ballooning modes.« less

  19. Minimum magnetic curvature for resilient divertors using Compact Toroidal Hybrid geometry

    DOE PAGES

    Bader, Aaron; Hegna, C. C.; Cianciosa, Mark R.; ...

    2018-03-16

    The properties of resilient divertors are explored using equilibria derived from Compact Toroidal Hybrid (CTH) geometries. Resilience is defined here as the robustness of the strike point patterns as the plasma geometry and/or plasma profiles are changed. The addition of plasma current in the CTH configurations significantly alters the shape of the last closed flux surface and the rotational transform profile, however, it does not alter the strike point pattern on the target plates, and hence has resilient divertor features. The limits of when a configuration transforms to a resilient configuration is then explored. New CTH-like configurations are generated thatmore » vary from a perfectly circular cross section to configurations with increasing amounts of toroidal shaping. It is found that even small amounts of toroidal shaping lead to strike point localization that is similar to the standard CTH configuration. Lastly, these results show that only a small degree of three-dimensional shaping is necessary to produce a resilient divertor, implying that any highly shaped optimized stellarator will possess the resilient divertor property.« less

  20. Increased confinement and beta by inductive poloidal current drive in the RFP

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sarff, J.S.; Lanier, N.E.; Prager, S.C.

    1996-10-01

    Progress in understanding magnetic-fluctuation-induced transport in the reversed field pinch (RFP) has led to the idea of current profile control to reduce fluctuations and transport. With the addition of inductive poloidal current drive in the Madison Symmetric Torus (MST), the magnetic fluctuation amplitude is halved, leading to a four- to five-fold increase in the energy confinement time to {tau}{sub E}{approximately}5 ms as a result of both decreased plasma resistance and increased stored thermal energy. The record low fluctuation amplitude coincides with a record high electron temperature of {approximately}600 eV (for MST), and beta {beta} = 2{mu}{sub 0} / B(a){sup 2}more » increases from 6% to 8% compared with conventional MST RFP plasmas. Other improvements include increased particle confinement and impurity reduction. 19 refs., 4 figs., 1 tab.« less

  1. Magnetohydrodynamic simulations of noninductive helicity injection in the reversed-field pinch and tokamak

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sovinec, Carl R.

    1995-11-01

    Numerical computation is used to investigate resistive magnetohydrodynamic (MHD) fluctuations in the reversed-field pinch (RFP) and in tokamak-like configurations driven solely by direct current (DC) helicity injection. A Lundquist number (S) scan of RFP turbulence without plasma pressure produces the weak scaling of S -0.18 for the root-mean-square magnetic fluctuation level for 2.5x10 3≤S≤4x10 4. The temporal behavior of fluctuations and the reversal parameter becomes more regular as S is increased, acquiring a "sawtooth" shape at the largest value of S. Simulations with plasma pressure and anisotropic thermal conduction demonstrate energy transport resulting from parallel heat fluctuations. To investigate meansmore » of improving RFP energy confinement, three forms of current profile modification are tested. Radio frequency (RF) current drive is modeled with an auxiliary electron force, and linear stability calculations are used.« less

  2. Scrape-off-layer characterization and current-control of kink modes in HBT-EP

    NASA Astrophysics Data System (ADS)

    Brooks, John; Stewart, Ian; Levesque, Jeffrey; Mauel, Mike; Navratil, Gerald

    2017-10-01

    Scrape-off layer (SOL) currents and their paths through tokamaks are not well understood, but their control may prove crucial to the success of ITER and future fusion energy devices. We extend Columbia University's High Beta Tokamak-Extended Pulse (HBT-EP) experiment and active GPU feedback system to study the SOL and control MHD kink instabilities by actively controlling these currents. First, the radial plasma profiles and the edge structure of kink instabilities are measured with two triple probes. Second, we use active feedback control of a radially adjustable biased electrode to change the rotation and magnitude of slowly growing kink instabilities. By changing the phase between the probe's voltage and the edge instability with active feedback, we study its ability to influence and control plasma MHD structures. This work is in preparation for a planned 2018 multi-electrode SOL control upgrade. Supported by U.S. DOE Grant DE-FG02-86ER53222.

  3. The effect of safety factor profile on transport in steady-state, high-performance scenarios

    DOE PAGES

    Holcomb, C. T.; Ferron, J. R.; Luce, T. C.; ...

    2012-03-09

    In this study, an analysis of the dependence of transport on the safety factor profile in high-performance, steady-state scenario discharges is presented. This is based on experimental scans of q 95 and q min taken with fixed β N, toroidal field, double-null plasma shape, divertor pumping, and electron cyclotron current drive input. The temperature and thermal diffusivity profiles were found to vary considerably with the q-profile, and these variations were significantly different for electrons and ions. With fixed q 95, both temperature profiles increase and broaden as q min is increased and the magnetic shear becomes low or negative inmore » the inner half radius, but these temperature profile changes are stronger for the electrons. Power balance calculations show the peak in the ion thermal diffusivity (χ i) at ρ – 0.6 – 0.8 increases with q 95 or q min.« less

  4. Laser beat wave excitation of terahertz radiation in a plasma slab

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chauhan, Santosh; Parashar, Jetendra, E-mail: j.p.parashar@gmail.com

    2014-10-15

    Terahertz (THz) radiation generation by nonlinear mixing of lasers, obliquely incident on a plasma slab is investigated. Two cases are considered: (i) electron density profile is parabolic but density peak is below the critical density corresponding to the beat frequency, (ii) plasma boundaries are sharp and density is uniform. In both cases, nonlinearity arises through the ponderomotive force that gives rise to electron drift at the beat frequency. In the case of inhomogeneous plasma, non zero curl of the nonlinear current density gives rise to electromagnetic THz generation. In case of uniform plasma, the sharp density variation at the plasmamore » boundaries leads to radiation generation. In a slab width of less than a terahertz wavelength, plasma density one fourth of terahertz critical density, laser intensities ∼10{sup 17 }W/cm{sup 2} at 1 μm, one obtains the THz intensity ∼1 GW/cm{sup 2} at 3 THz radiation frequency.« less

  5. DOE Office of Scientific and Technical Information (OSTI.GOV)

    Thompson, M. C., E-mail: mthompson@trialphaenergy.com; Gota, H.; Putvinski, S.

    The C-2U experiment at Tri Alpha Energy studies the evolution of field-reversed configuration (FRC) plasmas sustained by neutral beam injection. Data on the FRC plasma performance are provided by a comprehensive suite of diagnostics that includes magnetic sensors, interferometry, Thomson scattering, spectroscopy, bolometry, reflectometry, neutral particle analyzers, and fusion product detectors. While many of these diagnostic systems were inherited from the preceding experiment C-2, C-2U has a variety of new and upgraded diagnostic systems: multi-chord far-infrared polarimetry, multiple fast imaging cameras with selectable atomic line filters, proton detector arrays, and 100 channel bolometer units capable of observing multiple regions ofmore » the spectrum simultaneously. In addition, extensive ongoing work focuses on advanced methods of measuring separatrix shape and plasma current profile that will facilitate equilibrium reconstruction and active control of the FRC plasma.« less

  6. Confinement in Wendelstein 7-X Limiter Plasmas

    DOE PAGES

    Hirsch, M.; Dinklage, A.; Alonso, A.; ...

    2017-06-14

    Observations on confinement in the first experimental campaign on the optimized Stellarator Wendelstein 7-X are summarized. In this phase W7-X was equipped with five inboard limiters only and thus the discharge length restricted to avoid local overheating. Stationary plasmas are limited to low densities <2–3 centerdot 10 19 m -3. With the available 4.3 MW ECR Heating core T e ~ 8 keV, T i ~ 1–2 keV are achieved routinely resulting in energy confinement time τ E between 80 ms to 150 ms. For these conditions the plasmas show characteristics of core electron root confinement with peaked T e-profilesmore » and positive E r up to about half of the minor radius. Lastly, profiles and plasma currents respond to on- and off-axis heating and co- and counter ECCD respectively.« less

  7. Improved H mode with flat central q profile on EAST

    NASA Astrophysics Data System (ADS)

    Liu, Haiqing; Yang, Yao; Gao, Xiang; Zeng, Long; Qian, Jinping; Gong, Xianzu; Wan, Baonian; Ding, Weixing; Brower, David Lyn; EAST Team

    2017-10-01

    High betaN ( 1.8) plasma with good confinement (H98y2 1.1) on EAST tokamak has been reported recently. These ELMy H-mode plasmas with Bt = 1.6T, Ip = 400 kA and q95 4.5 were heated by lower hybrid wave and neutral beam injection. The internal transport barrier (ITB) and edge transport barrier (ETB) are both observed with m/n =1/1 fishbone, which were identified to clamp central q at values close to unity. Implying an improved H-mode with flat central q profile and absence of sawteeth, like other devices. Accurate q profile, key profile for developing scenarios aim at high performance H mode, were derived by Polarimeter-interferometer (POINT) measurement as constraint. Base on the optimized current profile, better confinement (H98y2 1.4) with an electron ITB was obtained also with flat central q profile and absence of sawteeth at high betaP ( 2) regime with Bt = 2.5T, Ip = 400 kA. Both high betaN regime and high betaP regime H mode, are characterized by a stationary flat central q profile q0 >=1, but typically close to 1, absence of sawteeth, H98(y,2) >1 and simultaneously, with ITB. This work is supported by the National Magnetic Confinement Fusion Program of China with Contract No. 2014GB106002 and partly supported by the US D.O.E. contract DESC0010469.

  8. Impact in Plasma Metabolome as Effect of Lifestyle Intervention for Weight-Loss Reveals Metabolic Benefits in Metabolically Healthy Obese Women.

    PubMed

    Almanza-Aguilera, Enrique; Brunius, Carl; Bernal-Lopez, M Rosa; Garcia-Aloy, Mar; Madrid-Gambin, Francisco; Tinahones, Francisco J; Gómez-Huelgas, Ricardo; Landberg, Rikard; Andres-Lacueva, Cristina

    2018-06-28

    Little is known regarding metabolic benefits of weight loss (WL) on the metabolically healthy obese (MHO) patients. We aimed to examine the impact of a lifestyle weight loss (LWL) treatment on the plasma metabolomic profile in MHO individuals. Plasma samples from 57 MHO women allocated to an intensive LWL treatment group (TG, hypocaloric Mediterranean diet and regular physical activity, n = 30) or to a control group (CG, general recommendations of a healthy diet and physical activity, n = 27) were analyzed using an untargeted 1 H NMR metabolomics approach at baseline, after 3 months (intervention), and 12 months (follow-up). The impact of the LWL intervention on plasma metabolome was statistically significant at 3 months but not at follow-up and included higher levels of formate and phosphocreatine and lower levels of LDL/VLDL (signals) and trimethylamine in the TG. These metabolites were also correlated with WL. Higher myo-inositol, methylguanidine, and 3-hydroxybutyrate, and lower proline, were also found in the TG; higher levels of hippurate and asparagine, and lower levels of 2-hydroxybutyrate and creatine, were associated with WL. The current findings suggest that an intensive LWL treatment, and the consequent WL, leads to an improved plasma metabolic profile in MHO women through its impact on energy, amino acid, lipoprotein, and microbial metabolism.

  9. Effects of the plasma profiles on photon and pair production in ultrahigh intensity laser solid interaction

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tian, Y. X.; Jin, X. L., E-mail: jinxiaolin@uestc.edu.cn; Yan, W. Z.

    The model of photon and pair production in strong field quantum electrodynamics is implemented into our 1D3V particle-in-cell code with Monte Carlo algorithm. Using this code, the evolution of the particles in ultrahigh intensity laser (∼10{sup 23} W/cm{sup 2}) interaction with aluminum foil target is observed. Four different initial plasma profiles are considered in the simulations. The effects of initial plasma profiles on photon and pair production, energy spectra, and energy evolution are analyzed. The results imply that one can set an optimal initial plasma profile to obtain the desired photon distributions.

  10. Clinical features and hormonal profiles of cloprostenol-induced early abortions in heifers monitored by ultrasonography

    PubMed Central

    Lobago, Fikre; Gustafsson, Hans; Bekana, Merga; Beckers, Jean-François; Kindahl, Hans

    2006-01-01

    Background The present study describes the clinical features and plasma profiles of bovine pregnancy-associated glycoprotein 1 (bPAG1), the main metabolite of prostaglandin F2α (PG metabolite) and progesterone (P4) in heifers in which early abortions were induced. Methods Early abortions were induced in four heifers with cloprostenol and monitored by ultrasonography. Blood samples were collected and the plasma were analyzed for bPAG 1, P4 and PG metabolite. Results The foetal heartbeat rates varied from 170–186 beats per minute for all foetuses up to the date of cloprostenol treatment. Foetal death was confirmed within two days after cloprostenol treatment. Prior to cloprostenol injection, blood plasma concentrations of bPAG1, PG metabolite and P4 varied from 8.4 – 40.0 ng/mL, 158 – 275 pmol/L and 20.7 – 46.9 nmol/L, respectively. After the foetus expelled, the plasma level of bPAG1 began to decrease but the decrease was small and gradual. The estimated half-life of bPAG1 was 1.8 – 6.6 days. The plasma level of the PG metabolite started to have short lasting peaks (above 300 pmol/L) within three hours after cloprostenol treatment. The plasma concentrations of P4 dropped sharply to less than 4 nmol/L after 24 hours of cloprostenol injection. Conclusion The current findings indicated that after early closprostenol-induced foetal death, the plasma concentration of bPAG1 decreased gradually and showed a tendency of variation with the stages of pregnancy. PMID:17121683

  11. Electric currents in the subsolar region of the Venus lower ionosphere

    NASA Technical Reports Server (NTRS)

    Cole, K. D.; Hoegy, W. R.

    1994-01-01

    The ion and electron momentum equations, along with Ampere's law, are solved for the ion and electron drift velocities and the electric field in the subsolar Venus ionosphere, assuming a partially ionized gas and a single ion species having the ion mean mass. All collision terms among the ions, electrons and neutral particles are retained in the equations. A general expression for the evolution of the magnetic field is derived and compared with earlier expressions. Subsolar region data in the altitude range 150-300 km from the Pioneer Venus Orbiter are used to calculate altitude profiles of the components of the current due to the electric field, gradients of pressure, and gravity. Altitude profiles of the ion and electron velocities as well as the electric field, electrodynamic heating, and the energy density are determined. Only orbits having a complete set of measured plasma temperatures and densities, neutral densities, and magnetic field were considered for analysis; the results are shown only for orbit 202. The vertical velocity at altitudes above 220 km is upgoing for orbit 202. This result is consistent with observations of molecular ions at high altitudes and of plasma flow to the nightside, both of which require upward velocity of ions from the dayside ionosphere. Above about 230 km the momentum equations are extremely sensitive to the altitude profiles of density, temperature, and magnetic field.

  12. Structure of micro-instabilities in tokamak plasmas: Stiff transport or plasma eruptions?

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dickinson, D., E-mail: dd502@york.ac.uk; EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxon OX14 3DB; Roach, C. M.

    2014-01-15

    Solutions to a model 2D eigenmode equation describing micro-instabilities in tokamak plasmas are presented that demonstrate a sensitivity of the mode structure and stability to plasma profiles. In narrow regions of parameter space, with special plasma profiles, a maximally unstable mode is found that balloons on the outboard side of the tokamak. This corresponds to the conventional picture of a ballooning mode. However, for most profiles, this mode cannot exist, and instead, a more stable mode is found that balloons closer to the top or bottom of the plasma. Good quantitative agreement with a 1D ballooning analysis is found, providedmore » the constraints associated with higher order profile effects, often neglected, are taken into account. A sudden transition from this general mode to the more unstable ballooning mode can occur for a critical flow shear, providing a candidate model for why some experiments observe small plasma eruptions (Edge Localised Modes, or ELMs) in place of large Type I ELMs.« less

  13. Time-and-space resolved comparison of plasma expansion velocities in high-power diodes with velvet cathodes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yang Jie; Shu Ting; Fan Yuwei

    2013-01-28

    Time-and-space resolved comparison of the expansion velocities of plasmas in the planar diode with cathodes made of carbon velvet and polymer velvet has been performed. The diode was powered by a 200 kV, 110 ns pulse, and the peak current density was nearly 477 A/cm{sup 2}. A four-channel high speed framing camera (HSFC) was used to observe the formation and subsequent movement of the cathode plasmas. More accurate and valuable information about the two-dimensional (radial and axial) velocity components of the cathode plasmas was also acquired by utilizing the digital image processing methods. Additionally, the perveance model based on themore » Child-Langmuir law was used to calculate the expansion velocities of the diode plasmas from voltage and current profiles. Results from the two diagnostics were compared. Comparing the average values of the radial and axial velocity components indicated that the former was much larger than the latter during the initial period of the current. It was also found that the radial velocity of the carbon velvet cathode (190 cm/{mu}s) was much larger than that (90 cm/{mu}s) of the polymer velvet cathode. Moreover, the average values of both the radial and axial velocity components of the carbon velvet cathode were typically in the range of 2.5 {+-} 1.5 cm/{mu}s, which were smaller than that of the polymer velvet cathode during the current flattop. These results, together with the comparison of calculated values from the perveance model, indicated that the diode with carbon velvet cathode was more robust as compared with the polymer velvet cathode for the same electron current densities.« less

  14. Field Aligned Currents Derived from Pressure Profiles Obtained from TWINS ENA Images

    NASA Astrophysics Data System (ADS)

    Wood, K.; Perez, J. D.; McComas, D. J.; Goldstein, J.; Valek, P. W.

    2015-12-01

    Field aligned currents (FACs) that flow from the Earth's magnetosphere into the ionosphere are an important coupling mechanism in the interaction of the solar wind with the Earth's magnetosphere. Assuming pressure balance along with charge conservation yields an expression for the FACs in terms of plasma pressure gradients and pressure anisotropy. The Two Wide-Angle Imaging Neutral Atom Spectrometers (TWINS) mission, the first stereoscopic ENA magnetospheric imager, provides global images of the inner magnetosphere from which ion pressure distributions and pressure anisotropies can be obtained. Following the formulations in Heineman [1990] and using results from TWINS observations, we calculate the distribution of field aligned currents for the 17-18 March 2015 geomagnetic storm in which extended ionospheric precipitation was observed. Initial results for the field aligned currents will be generated assuming an isotropic pitch angle distribution. Global maps of field aligned currents during the main and recovery phase of the storm will be presented. Heinemann, H. (1990), Representations of Currents and Magnetic Fields in Anisotropic Magnetohydrostatic Plasma, J. Geophys. Res., 95, 7789.

  15. Reduced levels of potential circulating biomarkers of cardiovascular diseases in apparently healthy vegetarian men.

    PubMed

    Navarro, Julio Acosta; de Gouveia, Luiza Antoniazzi; Rocha-Penha, Lilliam; Cinegaglia, Naiara; Belo, Vanessa; Castro, Michele Mazzaron de; Sandrim, Valeria Cristina

    2016-10-01

    Several evidences report that a vegetarian diet is protector against cardiovascular diseases. Few studies have demonstrated the circulating profile of cardiovascular biomarkers in vegetarians. Therefore, the aims of the current study were compared the plasma concentrations of myeloperoxidase (MPO), metalloproteinase (MMP)-9, MMP-2, tissue inhibitor of MMP (TIMP)-1 and TIMP-2 between healthy vegetarian (Veg) and healthy omnivorous (Omn). Using ELISA and multiplexed bead immunoassay, we measured in plasma from 43 Veg and 41 Omn the cardiovascular biomarkers concentrations cited above. We found significant lower concentrations of MPO, MMP-9, MMP-2 and MMP-9/TIMP-1 ratio in Veg compared to Omn (all P<0.05). Moreover, MMP-9 concentrations were correlated positively with leukocytes and neutrophils count in both groups (all P<0.05). A vegetarian diet is associated with a healthier profile of cardiovascular biomarkers compared to omnivorous. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Acceleration processes in the quasi-steady magnetoplasmadynamic discharge. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Boyle, M. J.

    1974-01-01

    The flow field characteristics within the discharge chamber and exhaust of a quasi-steady magnetoplasmadynamic (MPD) arcjet were examined to clarify the nature of the plasma acceleration process. The observation of discharge characteristics unperturbed by insulator ablation and terminal voltage fluctuations, first requires the satisfaction of three criteria: the use of refractory insulator materials; a mass injection geometry tailored to provide propellant to both electrode regions of the discharge; and a cathode of sufficient surface area to permit nominal MPD arcjet operation for given combinations of arc current and total mass flow. The axial velocity profile and electromagnetic discharge structure were measured for an arcjet configuration which functions nominally at 15.3 kA and 6 g/sec argon mass flow. An empirical two-flow plasma acceleration model is advanced which delineates inner and outer flow regions and accounts for the observed velocity profile and calculated thrust of the accelerator.

  17. Impact of impurities on zonal flow driven by trapped electron mode turbulence

    NASA Astrophysics Data System (ADS)

    Guo, Weixin; Wang, Lu; Zhuang, Ge

    2017-12-01

    The impact of impurities on the generation of zonal flow (ZF) driven by collisonless trapped electron mode turbulence in deuterium (D)-tritium (T) plasmas is investigated. An expression for ZF growth rate with impurities is derived by balancing the ZF potential shielded by polarization effects and the ZF modulated radial turbulent current. Then, it is shown that the maximum normalized ZF growth rate is reduced by the presence of fully ionized non-trace light impurities with relatively flat density profile, and slightly reduced by highly ionized trace tungsten, while the maximum normalized ZF growth rate can be enhanced by fully ionized non-trace light impurities with relatively steep density profile. In particular, the effects of high temperature helium from D-T reaction on ZF depend on the temperature ratio between electrons and high temperature helium. The possible relevance of our findings to recent experimental results and future burning plasmas is also discussed.

  18. Velocity shear, turbulent saturation, and steep plasma gradients in the scrape-off layer of inner-wall limited tokamaks

    DOE PAGES

    Halpern, Federico D.; Ricci, Paolo

    2016-12-19

    The narrow power decay-length (λ q), recently found in the scrape-off layer (SOL) of inner wall limited (IWL) discharges in tokamaks, is studied using 3D, flux-driven, global two fluid turbulence simulations. The formation of the steep plasma profiles is found to arise due to radially sheared E×B poloidal flows. A complex interaction between sheared flows and parallel plasma currents outflowing into the sheath regulates the turbulent saturation, determining the transport levels. We quantify the effects of sheared flows, obtaining theoretical estimates in agreement with our non-linear simulations. As a result, analytical calculations suggest that the IWL λ q is roughlymore » equal to the turbulent correlation length.« less

  19. The segmented non-uniform dielectric module design for uniformity control of plasma profile in a capacitively coupled plasma chamber

    NASA Astrophysics Data System (ADS)

    Xia, Huanxiong; Xiang, Dong; Yang, Wang; Mou, Peng

    2014-12-01

    Low-temperature plasma technique is one of the critical techniques in IC manufacturing process, such as etching and thin-film deposition, and the uniformity greatly impacts the process quality, so the design for the plasma uniformity control is very important but difficult. It is hard to finely and flexibly regulate the spatial distribution of the plasma in the chamber via controlling the discharge parameters or modifying the structure in zero-dimensional space, and it just can adjust the overall level of the process factors. In the view of this problem, a segmented non-uniform dielectric module design solution is proposed for the regulation of the plasma profile in a CCP chamber. The solution achieves refined and flexible regulation of the plasma profile in the radial direction via configuring the relative permittivity and the width of each segment. In order to solve this design problem, a novel simulation-based auto-design approach is proposed, which can automatically design the positional sequence with multi independent variables to make the output target profile in the parameterized simulation model approximate the one that users preset. This approach employs an idea of quasi-closed-loop control system, and works in an iterative mode. It starts from initial values of the design variable sequences, and predicts better sequences via the feedback of the profile error between the output target profile and the expected one. It never stops until the profile error is narrowed in the preset tolerance.

  20. Proteomic plasma profile of psoriatic patients.

    PubMed

    Gęgotek, Agnieszka; Domingues, Pedro; Wroński, Adam; Wójcik, Piotr; Skrzydlewska, Elżbieta

    2018-06-05

    Psoriasis is a chronic, immune-mediated inflammatory skin disease with severe consequences for the whole organism. The lack of complete knowledge of the main factors predisposing an individual to the appearance of psoriatic lesions, has recently led to the search for modifications in biochemical pathways participating in the development of this disease. We therefore aimed to investigate changes in the plasma proteomic profile of patients with psoriasis. A proteomics approach was used to analyze the expression of proteins in plasma from psoriatic patients and healthy controls (sex- and age-matched individuals). The analysis was performed using gel electrophoresis, followed by nanoflow LC-MS/MS using a Q-Exactive OrbiTrap mass spectrometer. Proteomic data indicated a significant decrease in the level of proteins involved in lipid metabolism, such as apolipoprotein M, and proteins involved in the management of vitamin D levels in psoriatic patients' plasma. These changes were accompanied by the expression of proteins involved in immune response and signal transduction. This was particularly evident by the level of transcriptional factors, including AT motif binding factor 1, which regulates excessive cellular proliferation and differentiation. It was also suggested that psoriasis development was associated with increased expression of proteins directly involved in signaling molecule secretion [biotinidase and BAI1-associated protein 3]. In addition, the lipid peroxidation product - 4-hydroxynonenal (4-HNE) generates higher level of adducts with proteins in the plasma of psoriatic patients. Moreover, plasma proteins from healthy subjects creating with 4-HNE adducts were mainly characterized as structural, while in the plasma of psoriatic patients, increased levels of 4-HNE-protein adducts with catalytic activity were observed. The results presented herein confirm the current knowledge about the profile of proteins responsible for the immune response and management of vitamin D in the plasma of psoriatic patients. However, several new proteins were also identified, which are involved in signal transduction and lipid metabolism as well as catalytic activity. The expression or structure of these proteins was shown to change through the course of the development of psoriasis. This knowledge may help contribute to the design of more specific pharmacotherapy. Copyright © 2018 Elsevier B.V. All rights reserved.

  1. Incorporating a Generic Model of Subcutaneous Insulin Absorption into the AIDA v4 Diabetes Simulator 3. Early Plasma Insulin Determinations

    PubMed Central

    Lehmann, Eldon D.; Tarín, Cristina; Bondia, Jorge; Teufel, Edgar; Deutsch, Tibor

    2009-01-01

    Introduction AIDA is an interactive educational diabetes simulator that has been available without charge via the Internet for over 12 years. Recent articles have described the incorporation of a novel generic model of insulin absorption into AIDA as a way of enhancing its capabilities. The basic model components to be integrated have been overviewed, with the aim being to provide simulations of regimens utilizing insulin analogues, as well as insulin doses greater than 40 IU (the current upper limit within the latest release of AIDA [v4.3a]). Some preliminary calculated insulin absorption results have also recently been described. Methods This article presents the first simulated plasma insulin profiles from the integration of the generic subcutaneous insulin absorption model, and the currently implemented model in AIDA for insulin disposition. Insulin absorption has been described by the physiologically based model of Tarín and colleagues. A single compartment modeling approach has been used to specify how absorbed insulin is distributed in, and eliminated from, the human body. To enable a numerical solution of the absorption model, a spherical subcutaneous depot for the injected insulin dose has been assumed and spatially discretized into shell compartments with homogeneous concentrations, having as its center the injection site. The number of these compartments will depend on the dose and type of insulin. Insulin inflow arises as the sum of contributions to the different shells. For this report the first bench testing of plasma insulin determinations has been done. Results Simulated plasma insulin profiles are provided for currently available insulin preparations, including a rapidly acting insulin analogue (e.g., lispro/Humalog or aspart/Novolog), a short-acting (regular) insulin preparation (e.g., Actrapid), intermediate-acting insulins (both Semilente and neutral protamine Hagedorn types), and a very long-acting insulin analogue (e.g., glargine/Lantus), as well as for insulin doses up to 50 IU. Discussion The methodology to be adopted for implementing the generic absorption model within AIDA has been overviewed, and the first plasma insulin profiles based on this approach have been demonstrated. Ideas for future work and development are discussed. It is expected that an updated release of AIDA (v4.5), based on this collaborative approach, will become available for free—in due course—via the www.2aida.org Web site. Readers who wish to be informed when the new software is launched can join the very low volume AIDA announcement list by sending a blank email note to subscribe@2aida.org. PMID:20046665

  2. Simulation of the electric potential and plasma generation coupling in magnetron sputtering discharges

    NASA Astrophysics Data System (ADS)

    Trieschmann, Jan; Krueger, Dennis; Schmidt, Frederik; Brinkmann, Ralf Peter; Mussenbrock, Thomas

    2016-09-01

    Magnetron sputtering typically operated at low pressures below 1 Pa is a widely applied deposition technique. For both, high power impulse magnetron sputtering (HiPIMS) as well as direct current magnetron sputtering (dcMS) the phenomenon of rotating ionization zones (also referred to as spokes) has been observed. A distinct spatial profile of the electric potential has been associated with the latter, giving rise to low, mid, and high energy groups of ions observed at the substrate. The adherent question of which mechanism drives this process is still not fully understood. This query is approached using Monte Carlo simulations of the heavy particle (i.e., ions and neutrals) transport consistently coupled to a pre-specified electron density profile via the intrinsic electric field. The coupling between the plasma generation and the electric potential, which establishes correspondingly, is investigated. While the system is observed to strive towards quasi-neutrality, distinct mechanisms governing the shape of the electric potential profile are identified. This work is supported by the German Research Foundation (DFG) in the frame of the transregional collaborative research centre TRR 87.

  3. Plasma IL-8 signature correlates with pain and depressive symptomatology in patients with burning mouth syndrome: Results from a pilot study.

    PubMed

    Barry, Alison; O'Halloran, Ken D; McKenna, Joseph P; McCreary, Christine; Downer, Eric J

    2018-02-01

    Burning mouth syndrome (BMS) is a neuropathic orofacial pain condition of unknown aetiology that encompasses intra-oral burning pain without abnormal clinical findings. Psychological, neural and inflammatory processes are associated with BMS pathogenesis. Currently, studies characterising plasma cytokine/chemokine profiles with pain and depression in patients with BMS are lacking. Considering that inflammation is associated with the pathophysiology of BMS, and that inflammation is closely associated with pain and depression, we aimed to correlate depressive symptomatology and oral cavity pain with plasma cytokine/chemokine signatures in a cohort of patients with BMS. In this study, plasma protein levels of Th1 cytokines (IFN-γ, IL-2, IL-12p70, TNF-α), Th2 cytokines (IL-4, IL-10, IL-6, IL-13) and the chemokine IL-8 were assessed in patients with BMS (n = 10) and healthy volunteers (n = 10), using pro-inflammatory-10-plex assays. Clinical histories, alongside self-rated oral cavity pain intensities and depressive symptomatology were assessed using a visual analogue scale and the 16-item Quick Inventory of Depressive Symptomatology questionnaires, respectively. We present evidence that BMS is associated with increased depressive symptomatology and enhanced oral cavity pain. Plasma isolated from BMS patients display enhanced expression of the pro-inflammatory chemokine IL-8, when compared to plasma from healthy individuals. Plasma IL-8 signature correlates with pain and depressive symptomatology in the study cohort. Overall, these findings indicate that plasma IL-8 profiles are dysregulated in BMS and that modulation of IL-8 production in the disorder may be a tool in the management of BMS symptomatology. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  4. The high-β{sub N} hybrid scenario for ITER and FNSF steady-state missions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Turco, F.; Petty, C. C.; Luce, T. C.

    2015-05-15

    New experiments on DIII-D have demonstrated the steady-state potential of the hybrid scenario, with 1 MA of plasma current driven fully non-inductively and β{sub N} up to 3.7 sustained for ∼3 s (∼1.5 current diffusion time, τ{sub R}, in DIII-D), providing the basis for an attractive option for steady-state operation in ITER and FNSF. Excellent confinement is achieved (H{sub 98y2} ∼ 1.6) without performance limiting tearing modes. The hybrid regime overcomes the need for off-axis current drive efficiency, taking advantage of poloidal magnetic flux pumping that is believed to be the result of a saturated 3/2 tearing mode. This allows for efficient currentmore » drive close to the axis, without deleterious sawtooth instabilities. In these experiments, the edge surface loop voltage is driven down to zero for >1 τ{sub R} when the poloidal β is increased above 1.9 at a plasma current of 1.0 MA and the ECH power is increased to 3.2 MW. Stationary operation of hybrid plasmas with all on-axis current drive is sustained at pressures slightly above the ideal no-wall limit, while the calculated ideal with-wall MHD limit is β{sub N} ∼ 4–4.5. Off-axis Neutral Beam Injection (NBI) power has been used to broaden the pressure and current profiles in this scenario, seeking to take advantage of higher predicted kink stability limits and lower values of the tearing stability index Δ′, as calculated by the DCON and PEST3 codes. Results based on measured profiles predict ideal limits at β{sub N} > 4.5, 10% higher than the cases with on-axis NBI. A 0-D model, based on the present confinement, β{sub N} and shape values of the DIII-D hybrid scenario, shows that these plasmas are consistent with the ITER 9 MA, Q = 5 mission and the FNSF 6.7 MA scenario with Q = 3.5. With collisionality and edge safety factor values comparable to those envisioned for ITER and FNSF, the high-β{sub N} hybrid represents an attractive high performance option for the steady-state missions of these devices.« less

  5. Characterization of onset of parametric decay instability of lower hybrid waves

    NASA Astrophysics Data System (ADS)

    Baek, S. G.; Bonoli, P. T.; Parker, R. R.; Shiraiwa, S.; Wallace, G. M.; Porkolab, M.; Takase, Y.; Brunner, D.; Faust, I. C.; Hubbard, A. E.; LaBombard, B. L.; Lau, C.

    2014-02-01

    The goal of the lower hybrid current drive (LHCD) program on Alcator C-Mod is to develop and optimize ITER-relevant steady-state plasmas by controlling the current density profile. Using a 4×16 waveguide array, over 1 MW of LH power at 4.6 GHz has been successfully coupled to the plasmas. However, current drive efficiency precipitously drops as the line averaged density (n¯e) increases above 1020m-3. Previous numerical work shows that the observed loss of current drive efficiency in high density plasmas stems from the interactions of LH waves with edge/scrape-off layer (SOL) plasmas [Wallace et al., Physics of Plasmas 19, 062505 (2012)]. Recent observations of parametric decay instability (PDI) suggest that non-linear effects should be also taken into account to fully characterize the parasitic loss mechanisms [Baek et al., Plasma Phys. Control Fusion 55, 052001 (2013)]. In particular, magnetic configuration dependent ion cyclotron PDIs are observed using the probes near n¯e≈1.2×1020m-3. In upper single null plasmas, ion cyclotron PDI is excited near the low field side separatrix with no apparent indications of pump depletion. The observed ion cyclotron PDI becomes weaker in inner wall limited plasmas, which exhibit enhanced current drive effects. In lower single null plasmas, the dominant ion cyclotron PDI is excited near the high field side (HFS) separatrix. In this case, the onset of PDI is correlated with the decrease in pump power, indicating that pump wave power propagates to the HFS and is absorbed locally near the HFS separatrix. Comparing the observed spectra with the homogeneous growth rate calculation indicates that the observed ion cyclotron instability is excited near the plasma periphery. The incident pump power density is high enough to overcome the collisional homogeneous threshold. For C-Mod plasma parameters, the growth rate of ion sound quasi-modes is found to be typically smaller by an order of magnitude than that of ion cyclotron quasi-modes. When considering the convective threshold near the plasma edge, convective growth due to parallel coupling rather than perpendicular coupling is likely to be responsible for the observed strength of the sidebands. To demonstrate the improved LHCD efficiency in high density plasmas, an additional launcher has been designed. In conjunction with the existing launcher, this new launcher will allow access to an ITER-like high single pass absorption regime, replicating the JLH(r) expected in ITER. The predictions from the time domain discharge scenarios, in which the two launchers are used, will be also presented.

  6. Prospects for Off-axis Current Drive via High Field Side Lower Hybrid Current Drive in DIII-D

    NASA Astrophysics Data System (ADS)

    Wukitch, S. J.; Shiraiwa, S.; Wallace, G. M.; Bonoli, P. T.; Holcomb, C.; Park, J. M.; Pinsker, R. I.

    2017-10-01

    An outstanding challenge for an economical, steady state tokamak is efficient off-axis current drive scalable to reactors. Previous studies have focused on high field side (HFS) launch of lower hybrid waves for current drive (LHCD) in double null configurations in reactor grade plasmas. The goal of this work is to find a HFS LHCD scenario for DIII-D that balances coupling, power penetration and damping. The higher magnetic field on the HFS improves wave accessibility, which allows for lower n||waves to be launched. These waves penetrate farther into the plasma core before damping at higher Te yielding a higher current drive efficiency. Utilizing advanced ray tracing and Fokker Planck simulation tools (GENRAY+CQL3D), wave penetration, absorption and drive current profiles in high performance DIII-D H-Mode plasmas were investigated. We found LH scenarios with single pass absorption, excellent wave penetration to r/a 0.6-0.8, FWHM r/a=0.2 and driven current up to 0.37 MA/MW coupled. These simulations indicate that HFS LHCD has potential to achieve efficient off-axis current drive in DIII-D and the latest results will be presented. Work supported by U.S. Dept. of Energy, Office of Science, Office of Fusion Energy Sciences, using User Facility DIII-D, under Award No. DE-FC02-04ER54698 and Contract No. DE-FC02-01ER54648 under Scientific Discovery through Advanced Computing Initiative.

  7. Extended MHD Modeling of Tearing-Driven Magnetic Relaxation

    NASA Astrophysics Data System (ADS)

    Sauppe, Joshua

    2016-10-01

    Driven plasma pinch configurations are characterized by the gradual accumulation and episodic release of free energy in discrete relaxation events. The hallmark of this relaxation in a reversed-field pinch (RFP) plasma is flattening of the parallel current density profile effected by a fluctuation-induced dynamo emf in Ohm's law. Nonlinear two-fluid modeling of macroscopic RFP dynamics has shown appreciable coupling of magnetic relaxation and the evolution of plasma flow. Accurate modeling of RFP dynamics requires the Hall effect in Ohm's law as well as first order ion finite Larmor radius (FLR) effects, represented by the Braginskii ion gyroviscous stress tensor. New results find that the Hall dynamo effect from < J × B > / ne can counter the MHD effect from - < V × B > in some of the relaxation events. The MHD effect dominates these events and relaxes the current profile toward the Taylor state, but the opposition of the two dynamos generates plasma flow in the direction of equilibrium current density, consistent with experimental measurements. Detailed experimental measurements of the MHD and Hall emf terms are compared to these extended MHD predictions. Tracking the evolution of magnetic energy, helicity, and hybrid helicity during relaxation identifies the most important contributions in single-fluid and two-fluid models. Magnetic helicity is well conserved relative to the magnetic energy during relaxation. The hybrid helicity is dominated by magnetic helicity in realistic low-beta pinch conditions and is also well conserved. Differences of less than 1 % between magnetic helicity and hybrid helicity are observed with two-fluid modeling and result from cross helicity evolution through ion FLR effects, which have not been included in contemporary relaxation theories. The kinetic energy driven by relaxation in the computations is dominated by velocity components perpendicular to the magnetic field, an effect that had not been predicted. Work performed at University of Wisconsin-Madison. LA-UR-16-24727.

  8. Hybrid simulations of solenoidal radio-frequency inductively coupled hydrogen discharges at low pressures

    NASA Astrophysics Data System (ADS)

    Yang, Wei; Li, Hong; Gao, Fei; Wang, You-Nian

    2016-12-01

    In this article, we have described a radio-frequency (RF) inductively coupled H2 plasma using a hybrid computational model, incorporating the Maxwell equations and the linear part of the electron Boltzmann equation into global model equations. This report focuses on the effects of RF frequency, gas pressure, and coil current on the spatial profiles of the induced electric field and plasma absorption power density. The plasma parameters, i.e., plasma density, electron temperature, density of negative ion, electronegativity, densities of neutral species, and dissociation degree of H2, as a function of absorption power, are evaluated at different gas pressures. The simulation results show that the utilization efficiency of the RF source characterized by the coupling efficiency of the RF electric field and power to the plasma can be significantly improved at the low RF frequency, gas pressure, and coil current, due to a low plasma density in these cases. The densities of vibrational states of H2 first rapidly increase with increasing absorption power and then tend to saturate. This is because the rapidly increased dissociation degree of H2 with increasing absorption power somewhat suppresses the increase of the vibrational states of H2, thus inhibiting the increase of the H-. The effects of absorption power on the utilization efficiency of the RF source and the production of the vibrational states of H2 should be considered when setting a value of the coil current. To validate the model simulations, the calculated electron density and temperature are compared with experimental measurements, and a reasonable agreement is achieved.

  9. Overview of KSTAR initial operation

    NASA Astrophysics Data System (ADS)

    Kwon, M.; Oh, Y. K.; Yang, H. L.; Na, H. K.; Kim, Y. S.; Kwak, J. G.; Kim, W. C.; Kim, J. Y.; Ahn, J. W.; Bae, Y. S.; Baek, S. H.; Bak, J. G.; Bang, E. N.; Chang, C. S.; Chang, D. H.; Chavdarovski, I.; Chen, Z. Y.; Cho, K. W.; Cho, M. H.; Choe, W.; Choi, J. H.; Chu, Y.; Chung, K. S.; Diamond, P.; Do, H. J.; Eidietis, N.; England, A. C.; Grisham, L.; Hahm, T. S.; Hahn, S. H.; Han, W. S.; Hatae, T.; Hillis, D.; Hong, J. S.; Hong, S. H.; Hong, S. R.; Humphrey, D.; Hwang, Y. S.; Hyatt, A.; In, Y. K.; Jackson, G. L.; Jang, Y. B.; Jeon, Y. M.; Jeong, J. I.; Jeong, N. Y.; Jeong, S. H.; Jhang, H. G.; Jin, J. K.; Joung, M.; Ju, J.; Kawahata, K.; Kim, C. H.; Kim, D. H.; Kim, Hee-Su; Kim, H. S.; Kim, H. K.; Kim, H. T.; Kim, J. H.; Kim, J. C.; Kim, Jong-Su; Kim, Jung-Su; Kim, Kyung-Min; Kim, K. M.; Kim, K. P.; Kim, M. K.; Kim, S. H.; Kim, S. S.; Kim, S. T.; Kim, S. W.; Kim, Y. J.; Kim, Y. K.; Kim, Y. O.; Ko, W. H.; Kogi, Y.; Kong, J. D.; Kubo, S.; Kumazawa, R.; Kwak, S. W.; Kwon, J. M.; Kwon, O. J.; LeConte, M.; Lee, D. G.; Lee, D. K.; Lee, D. R.; Lee, D. S.; Lee, H. J.; Lee, J. H.; Lee, K. D.; Lee, K. S.; Lee, S. G.; Lee, S. H.; Lee, S. I.; Lee, S. M.; Lee, T. G.; Lee, W. C.; Lee, W. L.; Leur, J.; Lim, D. S.; Lohr, J.; Mase, A.; Mueller, D.; Moon, K. M.; Mutoh, T.; Na, Y. S.; Nagayama, Y.; Nam, Y. U.; Namkung, W.; Oh, B. H.; Oh, S. G.; Oh, S. T.; Park, B. H.; Park, D. S.; Park, H.; Park, H. T.; Park, J. K.; Park, J. S.; Park, K. R.; Park, M. K.; Park, S. H.; Park, S. I.; Park, Y. M.; Park, Y. S.; Patterson, B.; Sabbagh, S.; Saito, K.; Sajjad, S.; Sakamoto, K.; Seo, D. C.; Seo, S. H.; Seol, J. C.; Shi, Y.; Song, N. H.; Sun, H. J.; Terzolo, L.; Walker, M.; Wang, S. J.; Watanabe, K.; Welander, A. S.; Woo, H. J.; Woo, I. S.; Yagi, M.; Yaowei, Y.; Yonekawa, Y.; Yoo, K. I.; Yoo, J. W.; Yoon, G. S.; Yoon, S. W.; KSTAR Team

    2011-09-01

    Since the successful first plasma generation in the middle of 2008, three experimental campaigns were successfully made for the KSTAR device, accompanied with a necessary upgrade in the power supply, heating, wall-conditioning and diagnostic systems. KSTAR was operated with the toroidal magnetic field up to 3.6 T and the circular and shaped plasmas with current up to 700 kA and pulse length of 7 s, have been achieved with limited capacity of PF magnet power supplies. The mission of the KSTAR experimental program is to achieve steady-state operations with high performance plasmas relevant to ITER and future reactors. The first phase (2008-2012) of operation of KSTAR is dedicated to the development of operational capabilities for a super-conducting device with relatively short pulse. Development of start-up scenario for a super-conducting tokamak and the understanding of magnetic field errors on start-up are one of the important issues to be resolved. Some specific operation techniques for a super-conducting device are also developed and tested. The second harmonic pre-ionization with 84 and 110 GHz gyrotrons is an example. Various parameters have been scanned to optimize the pre-ionization. Another example is the ICRF wall conditioning (ICWC), which was routinely applied during the shot to shot interval. The plasma operation window has been extended in terms of plasma beta and stability boundary. The achievement of high confinement mode was made in the last campaign with the first neutral beam injector and good wall conditioning. Plasma control has been applied in shape and position control and now a preliminary kinetic control scheme is being applied including plasma current and density. Advanced control schemes will be developed and tested in future operations including active profiles, heating and current drives and control coil-driven magnetic perturbation.

  10. Effect of advice to increase carbohydrate and reduce fat intake on dietary profile and plasma lipid concentrations in healthy postmenopausal women.

    PubMed

    Arefhosseini, S R; Edwards, C A; Malkova, D; Higgins, S

    2009-01-01

    The current dietary guidelines advise an increase in carbohydrate intake. However, there is concern regarding the effect this may have on coronary heart disease (CHD) risk, in particular in postmenopausal women, in light of the knowledge that raised triacylglycerol (TAG) may pose a stronger risk for CHD in this group. To evaluate the effect of advice to increase carbohydrate intake to 50% of energy intake as part of advice to follow current dietary guidelines on the dietary profile, including dietary glycaemic index (GI) and plasma lipids in healthy postmenopausal women. Twelve healthy postmenopausal women (56 +/- 6.5 years) took part in the study. Habitual diet was assessed by a 7-day weighed intake. On the basis of the results, subjects were advised to increase their carbohydrate intake to comply with the current dietary guidelines. Subjects were asked to follow this diet for 4 weeks, in a free-living situation. Fasting blood samples were obtained at baseline and after 1 and 4 weeks. There was a significant decrease in body mass index (BMI; p < 0.05) after 4 weeks. There was a significant increase in fasting TAG concentrations after 1 week (p < 0.05), and the high-density lipoprotein (HDL) cholesterol concentration was significantly decreased (p < 0.05) after 1 and 4 weeks. The subjects significantly increased their percentage of energy from carbohydrates and starch (p < 0.05 and p < 0.01, respectively) after 1 week, and their percentage of energy from starch after 4 weeks (p < 0.05). Dietary GI was significantly increased (p < 0.05) after 1 and 4 weeks. Fruit and vegetable intake was significantly increased after 1 week (p < 0.01), as was fruit intake alone (p < 0.05), and there was a significant increase (p < 0.05) in the 'antioxidant power' as measured by the ferric reducing ability of plasma assay. In postmenopausal women, following the UK dietary guidelines resulted in changes in the lipid profile that were more likely to favour an increased risk of CHD, as TAG concentrations were increased and HDL cholesterol concentrations were reduced. However, in addition, we found a significant reduction in BMI and a significant increase in the 'antioxidant power' of plasma, which should benefit health. 2009 S. Karger AG, Basel.

  11. Characterization of long-scale-length plasmas produced from plastic foam targets for laser plasma instability (LPI) research

    NASA Astrophysics Data System (ADS)

    Oh, Jaechul; Weaver, J. L.; Serlin, V.; Obenschain, S. P.

    2017-10-01

    We report on an experimental effort to produce plasmas with long scale lengths for the study of parametric instabilities, such as two plasmon decay (TPD) and stimulated Raman scattering (SRS), under conditions relevant to fusion plasma. In the current experiment, plasmas are formed from low density (10-100 mg/cc) CH foam targets irradiated by Nike krypton fluoride laser pulses (λ = 248 nm, 1 nsec FWHM) with energies up to 1 kJ. This experiment is conducted with two primary diagnostics: the grid image refractometer (Nike-GIR) to measure electron density and temperature profiles of the coronas, and time-resolved spectrometers with absolute intensity calibration to examine scattered light features of TPD or SRS. Nike-GIR was recently upgraded with a 5th harmonic probe laser (λ = 213 nm) to access plasma regions near quarter critical density of 248 nm light (4.5 ×1021 cm-3). The results will be discussed with data obtained from 120 μm scale-length plasmas created on solid CH targets in previous LPI experiments at Nike. Work supported by DoE/NNSA.

  12. First Results From the Alcator C-Mod Lower Hybrid Experiment

    NASA Astrophysics Data System (ADS)

    Parker, Ronald; Bernabei, Stefano; Grimes, Montgomery; Hosea, Joel; Johnson, David; Wilson, Randy

    2005-10-01

    A lower hybrid system operating at 4.6 GHz and capable of 3 MW source power has been installed on Alcator C-Mod. The grill facing the plasma consists of 4 rows of 24 waveguides. Electronic control of the amplitude and phase of the 12 klystrons supplying the RF power enables the launcher's n|| spectrum to be dynamically controlled over a wide range with a time response of 1 ms. Since the deposition of current depends on n|| as well as the temperature profile, the spatial distribution of the driven current can be varied with the same time response. Detection of fast electron Bremsstrahlung is the primary means of monitoring the driven current profile. Initial measurements at the 100 kW power level show that reflection coefficients as low as 7% are obtained at optimal phasing and density at the grill mouth. Comparison of these results with modeling predictions will be presented in a companion paper.

  13. Current profile modification experiments in EXTRAP T2R

    NASA Astrophysics Data System (ADS)

    Cecconello, M.; Malmberg, J.-A.; Spizzo, G.; Chapman, B. E.; Gravestjin, R. M.; Franz, P.; Piovesan, P.; Martin, P.; Drake, J. R.

    2004-01-01

    Pulsed poloidal current drive (PPCD) experiments have been conducted in the resistive shell EXTRAP T2R reversed-field pinch experiment. During the current profile modification phase, the fluctuation level of the m = 1 internally resonant tearing modes decreases, and the velocity of these modes increases. The m = 0 modes are not affected during PPCD, although termination occurs with a burst in the m = 0 amplitude. The PPCD phase is characterized by an increase in the central electron temperature (up to 380 eV) and in the soft x-ray signal. Spectroscopic observations confirm an increase in the central electron temperature. During PPCD, the plasma poloidal beta increases to 14%, and the estimated energy confinement time doubles, reaching 380 µs. The reduction in the fluctuation level and the corresponding increase in the energy confinement time are qualitatively consistent with a reduction in parallel transport along stochastic magnetic field lines.

  14. Multi-Frequency Microwaves Plasma Production for Active Profile Control of Ion Beams on a Large Bore ECR Ion Source with Permanent Magnets

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sakamoto, Naoki; Kato, Yushi; Kiriyama, Ryutaro

    2011-01-07

    A new concept on magnetic field of plasma production and confinement by using permanent magnets, i.e. cylindrically comb-shaped magnets, has been proposed to enhance efficiency of an electron cyclotron resonance (ECR) plasma for broad and dense ion beam source under the low pressure and also the low microwave power. The resonance zones corresponding to the fundamental ECR for 2.45 GHz and 11-13 GHz frequency are constructed at different positions. The profiles of the plasma parameters in the ECR ion source are different from each frequency of microwave. Large bore extractor is set at the opposite side against the microwave feeds.more » It is found that differences of their profiles also appear at those of ion beam profiles. We conducted to launch simultaneously multiplex frequency microwaves controlled individually, and tried to control the profiles of the plasma parameters and then those of extracted ion beam.« less

  15. Implementation of the new multichannel X-mode edge density profile reflectometer for the ICRF antenna on ASDEX Upgrade

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Aguiam, D. E., E-mail: daguiam@ipfn.tecnico.ulisboa.pt; Silva, A.; Carvalho, P. J.

    A new multichannel frequency modulated continuous-wave reflectometry diagnostic has been successfully installed and commissioned on ASDEX Upgrade to measure the plasma edge electron density profile evolution in front of the Ion Cyclotron Range of Frequencies (ICRF) antenna. The design of the new three-strap ICRF antenna integrates ten pairs (sending and receiving) of microwave reflectometry antennas. The multichannel reflectometer can use three of these to measure the edge electron density profiles up to 2 × 10{sup 19} m{sup −3}, at different poloidal locations, allowing the direct study of the local plasma layers in front of the ICRF antenna. ICRF power coupling,more » operational effects, and poloidal variations of the plasma density profile can be consistently studied for the first time. In this work the diagnostic hardware architecture is described and the obtained density profile measurements were used to track outer radial plasma position and plasma shape.« less

  16. Microwave produced plasma in a Toroidal Device

    NASA Astrophysics Data System (ADS)

    Singh, A. K.; Edwards, W. F.; Held, E. D.

    2010-11-01

    A currentless toroidal plasma device exhibits a large range of interesting basic plasma physics phenomena. Such a device is not in equilibrium in a strict magneto hydrodynamic sense. There are many sources of free energy in the form of gradients in plasma density, temperature, the background magnetic field and the curvature of the magnetic field. These free energy sources excite waves and instabilities which have been the focus of studies in several devices in last two decades. A full understanding of these simple plasmas is far from complete. At Utah State University we have recently designed and installed a microwave plasma generation system on a small tokamak borrowed from the University of Saskatchewan, Saskatoon, Canada. Microwaves are generated at 2.45 GHz in a pulsed dc mode using a magnetron from a commercial kitchen microwave oven. The device is equipped with horizontal and vertical magnetic fields and a transformer to impose a toroidal electric field for current drive. Plasmas can be obtained over a wide range of pressure with and without magnetic fields. We present some preliminary measurements of plasma density and potential profiles. Measurements of plasma temperature at different operating conditions are also presented.

  17. Parametric Instabilities During High Power Helicon Wave Injection on DIII-D

    NASA Astrophysics Data System (ADS)

    Porkolab, M.; Pinsker, R. I.

    2017-10-01

    High power helicon (whistler) waves at a frequency of 0.47 GHz are being considered for efficient off-axis current generation in high performance DIII-D plasmas and in K-Star [3]. The need for deploying helicon waves for current profile control has been noted in previous publications since penetration to the core of reactor grade plasmas is easier than with lower hybrid slow waves (LHCD) which suffer from accessibility limitations and strong electron Landau absorption in fusion grade high temperature plasmas. In this work we show that under typical experimental conditions in present day tokamaks with 1 MW of RF power coupled per antenna, the associated perpendicular electric fields of the order of 40 kV/m can drive strong parametric decay instabilities near the lower hybrid layer. The EXB and polarization drift velocities which are the dominant driver of the PDI can be comparable to the speed of sound in the outer plasma layers, a key measure of driving PDI instabilities. Here we calculate growth rates and convective thresholds for PDIs, and we find that decay waves into hot ion lower hybrid waves and ion cyclotron quasi modes dominate in the vicinity of the lower hybrid layer, possibly leading to pump depletion. Such instabilities in future reactor grade high temperature plasmas are less likely.

  18. Numerical simulation of current-free double layers created in a helicon plasma device

    NASA Astrophysics Data System (ADS)

    Rao, Sathyanarayan; Singh, Nagendra

    2012-09-01

    Two-dimensional simulations reveal that when radially confined source plasma with magnetized electrons and unmagnetized ions expands into diverging magnetic field B, a current-free double layer (CFDL) embedded in a conical density structure forms, as experimentally measured in the Australian helicon plasma device (HPD). The magnetized electrons follow the diverging B while the unmagnetized ions tend to flow directly downstream of the source, resulting in a radial electric field (E⊥) structure, which couples the ion and electron flows. Ions are transversely (radially) accelerated by E⊥ on the high potential side of the double layer in the CFDL. The accelerated ions are trapped near the conical surface, where E⊥ reverses direction. The potential structure of the CFDL is U-shaped and the plasma density is enhanced on the conical surface. The plasma density is severely depleted downstream of the parallel potential drop (φ||o) in the CFDL; the density depletion and the potential drop are related by quasi-neutrality condition, including the divergence in the magnetic field and in the plasma flow in the conical structure. The potential and density structures, the CFDL spatial size, its electric field strengths and the electron and ion velocities and energy distributions in the CFDL are found to be in good agreements with those measured in the Australian experiment. The applicability of our results to measured axial potential profiles in magnetic nozzle experiments in HPDs is discussed.

  19. Creating Hybrid Plasmas With Off-Axis ECCD for Radiating Divertor Studies in DIII-D

    NASA Astrophysics Data System (ADS)

    Petty, C. C.; Ferron, J. R.; Luce, T. C.; Osborne, T. H.; Petrie, T. W.; Turco, F.; Holcomb, C. T.; Thome, K. E.

    2017-10-01

    A long duration, high density, high power hybrid scenario has been developed for use in radiative divertor studies in DIII-D. Using 11.2 MW of co-NBI power and 3.4 MW of ECCD, with a total injected energy of up to 56 MJ, high performance hybrid plasmas with βN = 3.7 and H98y2 = 1.5 were created. The hybrid plasmas were fully non-inductive at densities of n 4.2 ×1019 m-3 with central ECCD, but the EC deposition needed to be moved to ρ = 0.45 to avoid the right-hand cutoff when the density was raised to n 5.8 ×1019 m-3 for radiative divertor studies. Although moving the EC deposition to ρ = 0.45 had the effect of dropping τE by 10%, the energy confinement time increased with higher density like τE n0.4, allowing high beta to be maintained. While the plasma current profile displays the usual self-organizing properties of hybrids - an anomalously broad profile with qmin >1 - local current drive can still have a measurable effect on stability, either positively or negatively. For example, hybrid discharges with radial ECH deposited at ρ = 0.45 proved to be more robustly stable to n = 1 modes (can be either a 1/1 or 2/1 mode) than similar discharges with co-ECCD at the same location. Interestingly, the large 1/1 mode had almost no effect on energy confinement but strongly degraded particle confinement; thus this mode needed to be suppressed to achieve the high pedestal densities required for radiative divertor studies. Work supported by USDOE under DE-FC02-04ER54698.

  20. Onset of fast "ideal" tearing in thin current sheets: Dependence on the equilibrium current profile

    NASA Astrophysics Data System (ADS)

    Pucci, F.; Velli, M.; Tenerani, A.; Del Sarto, D.

    2018-03-01

    In this paper, we study the scaling relations for the triggering of the fast, or "ideal," tearing instability starting from equilibrium configurations relevant to astrophysical as well as laboratory plasmas that differ from the simple Harris current sheet configuration. We present the linear tearing instability analysis for equilibrium magnetic fields which (a) go to zero at the boundary of the domain and (b) contain a double current sheet system (the latter previously studied as a Cartesian proxy for the m = 1 kink mode in cylindrical plasmas). More generally, we discuss the critical aspect ratio scalings at which the growth rates become independent of the Lundquist number S, in terms of the dependence of the Δ' parameter on the wavenumber k of unstable modes. The scaling Δ'(k) with k at small k is found to categorize different equilibria broadly: the critical aspect ratios may be even smaller than L/a ˜ Sα with α = 1/3 originally found for the Harris current sheet, but there exists a general lower bound α ≥ 1/4.

  1. Cathode fall model and current-voltage characteristics of field emission driven direct current microplasmas

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Venkattraman, Ayyaswamy

    2013-11-15

    The post-breakdown characteristics of field emission driven microplasma are studied theoretically and numerically. A cathode fall model assuming a linearly varying electric field is used to obtain equations governing the operation of steady state field emission driven microplasmas. The results obtained from the model by solving these equations are compared with particle-in-cell with Monte Carlo collisions simulation results for parameters including the plasma potential, cathode fall thickness, ion number density in the cathode fall, and current density vs voltage curves. The model shows good overall agreement with the simulations but results in slightly overpredicted values for the plasma potential andmore » the cathode fall thickness attributed to the assumed electric field profile. The current density vs voltage curves obtained show an arc region characterized by negative slope as well as an abnormal glow discharge characterized by a positive slope in gaps as small as 10 μm operating at atmospheric pressure. The model also retrieves the traditional macroscale current vs voltage theory in the absence of field emission.« less

  2. Sheared E×B flow and plasma turbulence viscosity in a Reversed Field Pinch

    NASA Astrophysics Data System (ADS)

    Vianello, N.; Antoni, V.; Spada, E.; Spolaore, M.; Serianni, G.; Regnoli, G.; Zuin, M.; Cavazzana, R.; Bergsåker, H.; Cecconello, M.; Drake, J. R.

    2004-11-01

    The relationship between electromagnetic turbulence and sheared plasma flow in Reversed Field Pinch configuration is addressed. The momentum balance equation for a compressible plasma is considered and the terms involved are measured in the outer region of Extrap-T2R RFP device. It results that electrostatic fluctuations determine the plasma flow through the electrostatic component of Reynolds Stress tensor. This term involves spatial and temporal scales comparable to those of MHD activity. The derived experimental perpendicular viscosity is consistent with anomalous diffusion, the latter being discussed in terms of electrostatic turbulence background and coherent structures emerging from fluctuations. The results indicate a dynamical interplay between turbulence, anomalous transport and mean E×B profiles. The momentum balance has been studied also in non-stationary condition during the application of Pulsed Poloidal Current Drive, which is known to reduce the amplitude of MHD modes.

  3. Simulations of Atmospheric Plasma Arcs

    NASA Astrophysics Data System (ADS)

    Pearcy, Jacob; Chopra, Nirbhav; Jaworski, Michael

    2017-10-01

    We present the results of computer simulation of cylindrical plasma arcs with characteristics similar to those predicted to be relevant in magnetohydrodynamic (MHD) power conversion systems. These arcs, with core temperatures on the order of 1 eV, place stringent limitations on the lifetime of conventional electrodes used in such systems, suggesting that a detailed analysis of arc characteristics will be crucial in designing more robust electrode systems. Simulations utilize results from NASA's Chemical Equilibrium with Applications (CEA) program to solve the Elenbaas-Heller equation in a variety of plasma compositions, including approximations of coal-burning plasmas as well as pure gas discharges. The effect of carbon dioxide injection on arc characteristics, emulating discharges from molten carbonate salt electrodes, is also analyzed. Results include radial temperature profiles, composition maps, and current-voltage (IV) characteristics of these arcs. Work supported by DOE contract DE-AC02-09CH11466.

  4. Current profile redistribution driven by neutral beam injection in a reversed-field pinch

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Parke, E.; Department of Physics, University of Wisconsin-Madison 1150 University Ave., Madison, Wisconsin 53706; Anderson, J. K.

    2016-05-15

    Neutral beam injection in reversed-field pinch (RFP) plasmas on the Madison Symmetric Torus [Dexter et al., Fusion Sci. Technol. 19, 131 (1991)] drives current redistribution with increased on-axis current density but negligible net current drive. Internal fluctuations correlated with tearing modes are observed on multiple diagnostics; the behavior of tearing mode correlated structures is consistent with flattening of the safety factor profile. The first application of a parametrized model for island flattening to temperature fluctuations in an RFP allows inferrence of rational surface locations for multiple tearing modes. The m = 1, n = 6 mode is observed to shift inward by 1.1 ± 0.6 cm withmore » neutral beam injection. Tearing mode rational surface measurements provide a strong constraint for equilibrium reconstruction, with an estimated reduction of q{sub 0} by 5% and an increase in on-axis current density of 8% ± 5%. The inferred on-axis current drive is consistent with estimates of fast ion density using TRANSP [Goldston et al., J. Comput. Phys. 43, 61 (1981)].« less

  5. Farfield Ion Current Density Measurements before and after the NASA HiVHAc EDU2 Vibration Test

    NASA Technical Reports Server (NTRS)

    Huang, Wensheng; Kamhawi, Hani; Shastry, Rohit

    2012-01-01

    There is an increasing need to characterize the plasma plume of the NASA HiVHAc thruster in order to better understand the plasma physics and to obtain data for spacecraft interaction studies. To address this need, the HiVHAc research team is in the process of developing a number of plume diagnostic systems. This paper presents the initial results of the farfield current density probe diagnostic system. Farfield current density measurements were carried out before and after a vibration test of the HiVHAc engineering development unit 2 that simulate typical launch conditions. The main purposes of the current density measurements were to evaluate the thruster plume divergence and to investigate any changes in the plasma plume that may occur as a result of the vibration test. Radial sweeps, as opposed to the traditional polar sweeps, were performed during these tests. The charged-weighted divergence angles were found to vary from 16 to 28 degrees. Charge density profiles measured pre- and post-vibration-test were found to be in excellent agreement. This result, alongside thrust measurements reported in a companion paper, confirm that the operation of the HiVHAc engineering development unit 2 were not altered by full-level/random vibration testing.

  6. Parasitic momentum flux in the tokamak core

    NASA Astrophysics Data System (ADS)

    Stoltzfus-Dueck, T.

    2017-10-01

    Tokamak plasmas rotate spontaneously without applied torque. This intrinsic rotation is important for future low-torque devices such as ITER, since rotation stabilizes certain instabilities. In the mid-radius `gradient region,' which reaches from the sawtooth inversion radius out to the pedestal top, intrinsic rotation profiles may be either flat or hollow, and can transition suddenly between these two states, an unexplained phenomenon referred to as rotation reversal. Theoretical efforts to explain the mid-radius rotation shear have largely focused on quasilinear models, in which the phase relationships of some selected instability result in a nondiffusive momentum flux (``residual stress''). In contrast, the present work demonstrates the existence of a robust, fully nonlinear symmetry-breaking momentum flux that follows from the free-energy flow in phase space and does not depend on any assumed linear eigenmode structure. The physical origin is an often-neglected portion of the radial ExB drift, which is shown to drive a symmetry-breaking outward flux of co-current momentum whenever free energy is transferred from the electrostatic potential to ion parallel flows. The fully nonlinear derivation relies only on conservation properties and symmetry, thus retaining the important contribution of damped modes. The resulting rotation peaking is counter-current and scales as temperature over plasma current. As first demonstrated by Landau, this free-energy transfer (thus also the corresponding residual stress) becomes inactive when frequencies are much higher than the ion transit frequency, which allows sudden transitions between hollow and flat profiles. Simple estimates suggest that this mechanism may be consistent with experimental observations. This work was funded in part by the Max-Planck/Princeton Center for Plasma Physics and in part by the U.S. Dept. of Energy, Office of Science, Contract No. DE-AC02-09CH11466.

  7. Final Scientific Report: Experimental Investigation of Reconnection in a Line-tied Plasma

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Forest, Cary

    This grant used funding from the NSF/DoE Partnership on Plasma Science to investigate magnetic reconnection phenomena in a line-tied pinch experiment. The experiment was upgraded from a previous device intended to study fusion plasma-related instabilities to a new configuration capable of studying a number of new, previously unstudied configurations. A high spatial and time resolution array of magnetic probes was constructed to measure time evolving structures present as instability and turbulence developed. The most important new equilibrium made possible by this grant was a Zero-Net-Current equilibrium that models the footpoint twisting of solar flux tubes that occurs prior to solarmore » eruptions (flares and coronal mass ejections). This new equilibrium was successfully created in the lab, and it exhibited a host of instabilities. In particular, at low current when the equilibrium was not overly stressed, a saturated internal kink mode oscillation was observed. At high current, 2 D magnetic turbulence developed which we attribute to the lack of a equilibrium brought about by a subcritical transition to turbulence. A second set of experiments involved the turbulent interactions of a collection of flux tubes all being twisted independently, a problem known as the Parker Problem. Current profiles consisting of 2, 3 and 4 guns were used to impose a fine scale drive, and resulted in a new experimental platform in which the injection scale of the magnetic turbulence could be controlled. First experiments in this configuration support the conclusion that an inverse cascade of magnetic energy occurred which self-organized the plasma into a nearly axisymmetric current distribution.« less

  8. H-mode plasmas at very low aspect ratio on the Pegasus Toroidal Experiment

    DOE PAGES

    Thome, Kathleen E.; Bongard, Michael W.; Barr, Jayson L.; ...

    2016-09-30

    H-mode is obtained atmore » $$A\\sim 1.2$$ in the Pegasus Toroidal Experiment via Ohmic heating, high-field-side fueling, and low edge recycling in both limited and diverted magnetic topologies. These H-mode plasmas show the formation of edge current and pressure pedestals and a doubling of the energy confinement time to $${{H}_{98y,2}}\\sim 1$$ . The L–H power threshold $${{P}_{\\text{LH}}}$$ increases with density, and there is no $${{P}_{\\text{LH}}}$$ minimum observed in the attainable density space. The power threshold is equivalent in limited and diverted plasmas, consistent with the FM3 model. However, the measured $${{P}_{\\text{LH}}}$$ is $$\\sim 15\\,\\,\\times $$ higher than that predicted by conventional International Tokamak Physics Activity (ITPA) scalings, and $${{P}_{\\text{LH}}}/{{P}_{\\text{ITPA}08}}$$ increases as $$A\\to 1$$ . Small ELMs are present at low input power $${{P}_{\\text{IN}}}\\sim {{P}_{\\text{LH}}}$$ , with toroidal mode number $$n\\leqslant 4$$ . At $${{P}_{\\text{IN}}}\\gg {{P}_{\\text{LH}}}$$ , they transition to large ELMs with intermediate 5 < n < 15. The dominant-n component of a large ELM grows exponentially, while other components evolve nonlinearly and can damp prior to the crash. Direct measurements of the current profile in the pedestal region show that both ELM types exhibit a generation of a current-hole, followed by a pedestal recovery. Large ELMs are shown to further expel a current-carrying filament. Small ELM suppression via injection of low levels of helical current into the edge plasma region is also indicated.« less

  9. Digital holographic interferometry employing Fresnel transform reconstruction for the study of flow shear stabilized Z-pinch plasmas.

    PubMed

    Ross, M P; Shumlak, U

    2016-10-01

    The ZaP-HD flow Z-pinch project provides a platform to explore how shear flow stabilized Z-pinches could scale to high-energy-density plasma (plasma with pressures exceeding 1 Mbar) and fusion reactor conditions. The Z-pinch is a linear plasma confinement geometry in which the plasma carries axial electric current and is confined by its self-induced magnetic field. ZaP-HD generates shear stabilized, axisymmetric Z-pinches with stable lifetimes approaching 60 μs. The goal of the project is to increase the plasma density and temperature compared to the previous ZaP project by compressing the plasma to smaller radii (≈1 mm). Radial and axial plasma electron density structure is measured using digital holographic interferometry (DHI), which provides the necessary fine spatial resolution. ZaP-HD's DHI system uses a 2 ns Nd:YAG laser pulse with a second harmonic generator (λ = 532 nm) to produce holograms recorded by a Nikon D3200 digital camera. The holograms are numerically reconstructed with the Fresnel transform reconstruction method to obtain the phase shift caused by the interaction of the laser beam with the plasma. This provides a two-dimensional map of line-integrated electron density, which can be Abel inverted to determine the local number density. The DHI resolves line-integrated densities down to 3 × 10 20 m -2 with spatial resolution near 10 μm. This paper presents the first application of Fresnel transform reconstruction as an analysis technique for a plasma diagnostic, and it analyzes the method's accuracy through study of synthetic data. It then presents an Abel inversion procedure that utilizes data on both sides of a Z-pinch local number density profile to maximize profile symmetry. Error estimation and Abel inversion are applied to the measured data.

  10. Self-consistent discharge growing model of helicon plasma

    NASA Astrophysics Data System (ADS)

    Isayama, Shogo; Hada, Tohru; Shinohara, Shunjiro; Tanikawa, Takao

    2015-11-01

    Helicon plasma is a high-density and low-temperature plasma generated by the electromagnetic (Helicon) wave excited in the plasma. It is thought to be useful for various applications including electric thrusters. Physics of helicon plasma production involves such fundamental processes as the wave propagation (dispersion relation), collisional and non-collisional wave damping, plasma heating, ionization/recombination of neutral particles, and modification of the dispersion relation by newly ionized plasma. There remain a number of unsolved physical issues such as, how the Helicon and the TG modes influence the plasma density, electron temperature and their spatial profiles. While the Helicon mode is absorbed in the bulk plasma, the TG mode is mostly absorbed near the edge of the plasma. The local power deposition in the helicon plasma is mostly balanced by collisional loss. This local power balance can give rise to the inhomogeneous electron temperature profile that leads to time evolution of density profile and dispersion relation. In our study, we construct a self-consistent model of the discharge evolution that includes the wave excitation, electron heat transfer, and diffusion of charged particles.

  11. Experimental Investigation of Pseudospark generated electron beam

    NASA Astrophysics Data System (ADS)

    Kumar, Niraj; Verma, D. K.; Prajapati, J.; Kumar, M.; Meena, B. L.; Tyagi, M. S.; Srivastava, V.; Pal, U. N.

    2012-11-01

    The pseudospark (PS) discharge is, however, more recently recognized as a different type of discharge which is capable of generating electron beams with the highest combined current density and brightness of any known type of electron source. PS discharge is a specific type of gas discharge, which operates on the left-hand side of the hollow cathode analogy to the Paschen curve with axially symmetric parallel electrodes and central holes on the electrodes. The PS discharge generated electron beam has tremendous applications in plasma filled microwave sources where normal material cathode cannot be used. Analysis of the electron beam profile has been carried out experimentally for different applied voltages. The investigation has been done at different axial and radial location inside the drift tube in argon atmosphere. This paper represents experimentally derived axial and radial variation of the beam current inside the plasma filled drift tube of PS discharge based plasma cathode electron (PCE) gun. With the help of current density estimation the focusing and defocusing point of electron beam in axial direction can be analyzed. It has been further confirmed the successful propagation of electron beam in confined manner without any assistance of external magnetic field.

  12. Plasma boundary shape control and real-time equilibrium reconstruction on NSTX-U

    DOE PAGES

    Boyer, M. D.; Battaglia, D. J.; Mueller, D.; ...

    2018-01-25

    Here, the upgrade to the National Spherical Torus eXperiment (NSTX-U) included two main improvements: a larger center-stack, enabling higher toroidal field and longer pulse duration, and the addition of three new tangentially aimed neutral beam sources, which increase available heating and current drive, and allow for flexibility in shaping power, torque, current, and particle deposition profiles. To best use these new capabilities and meet the high-performance operational goals of NSTX-U, major upgrades to the NSTX-U control system (NCS) hardware and software have been made. Several control algorithms, including those used for real-time equilibrium reconstruction and shape control, have been upgradedmore » to improve and extend plasma control capabilities. As part of the commissioning phase of first plasma operations, the shape control system was tuned to control the boundary in both inner-wall limited and diverted discharges. It has been used to accurately track the requested evolution of the boundary (including the size of the inner gap between the plasma and central solenoid, which is a challenge for the ST configuration), X-point locations, and strike point locations, enabling repeatable discharge evolutions for scenario development and diagnostic commissioning.« less

  13. Plasma boundary shape control and real-time equilibrium reconstruction on NSTX-U

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Boyer, M. D.; Battaglia, D. J.; Mueller, D.

    Here, the upgrade to the National Spherical Torus eXperiment (NSTX-U) included two main improvements: a larger center-stack, enabling higher toroidal field and longer pulse duration, and the addition of three new tangentially aimed neutral beam sources, which increase available heating and current drive, and allow for flexibility in shaping power, torque, current, and particle deposition profiles. To best use these new capabilities and meet the high-performance operational goals of NSTX-U, major upgrades to the NSTX-U control system (NCS) hardware and software have been made. Several control algorithms, including those used for real-time equilibrium reconstruction and shape control, have been upgradedmore » to improve and extend plasma control capabilities. As part of the commissioning phase of first plasma operations, the shape control system was tuned to control the boundary in both inner-wall limited and diverted discharges. It has been used to accurately track the requested evolution of the boundary (including the size of the inner gap between the plasma and central solenoid, which is a challenge for the ST configuration), X-point locations, and strike point locations, enabling repeatable discharge evolutions for scenario development and diagnostic commissioning.« less

  14. Improved long-term electrical stability of pulsed high-power diodes using dense carbon fiber velvet cathodes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yang Jie; Shu Ting; Wang Hui

    2012-07-15

    The influence of fibrous velvet cathodes on the electrical stability of a planar high-power diode powered by a {approx}230 kV, {approx}110 ns pulse has been investigated. The current density was on the order of {approx}123 A/cm{sup 2}. A combination of time-resolved electrical and optical diagnostics has been employed to study the basic phenomenology of the temporal and spatial evolution of the diode plasmas. Additionally, an impedance model was used to extract information about this plasma from voltage and current profiles. The results from the two diagnostics were compared. By comparison with commercial polymer velvet cathode, the dense carbon fiber velvetmore » cathode showed superior long-term electrical stability as judged by the change in cathode turn-on field, ignition delays, diode impedance, and surface plasma characteristics during the voltage flattop, a promising result for applications where reliable operation at high power is required. Finally, it was shown that the interaction of the electron beam with the stainless steel anode did not lead to the formation of anode plasma. These results may be of interest to the high power microwave systems with cold cathodes.« less

  15. Plasma boundary shape control and real-time equilibrium reconstruction on NSTX-U

    NASA Astrophysics Data System (ADS)

    Boyer, M. D.; Battaglia, D. J.; Mueller, D.; Eidietis, N.; Erickson, K.; Ferron, J.; Gates, D. A.; Gerhardt, S.; Johnson, R.; Kolemen, E.; Menard, J.; Myers, C. E.; Sabbagh, S. A.; Scotti, F.; Vail, P.

    2018-03-01

    The upgrade to the National Spherical Torus eXperiment (NSTX-U) included two main improvements: a larger center-stack, enabling higher toroidal field and longer pulse duration, and the addition of three new tangentially aimed neutral beam sources, which increase available heating and current drive, and allow for flexibility in shaping power, torque, current, and particle deposition profiles. To best use these new capabilities and meet the high-performance operational goals of NSTX-U, major upgrades to the NSTX-U control system (NCS) hardware and software have been made. Several control algorithms, including those used for real-time equilibrium reconstruction and shape control, have been upgraded to improve and extend plasma control capabilities. As part of the commissioning phase of first plasma operations, the shape control system was tuned to control the boundary in both inner-wall limited and diverted discharges. It has been used to accurately track the requested evolution of the boundary (including the size of the inner gap between the plasma and central solenoid, which is a challenge for the ST configuration), X-point locations, and strike point locations, enabling repeatable discharge evolutions for scenario development and diagnostic commissioning.

  16. Dependence of Edge Profiles and Stability on Neutral Beam Power in NSTX

    NASA Astrophysics Data System (ADS)

    Travis, P.; Canal, G. P.; Osborne, T. H.; Maingi, R.; Sabbagh, S. A.; NSTX-U Team

    2016-10-01

    Studying the effect of neutral beam injected (NBI) power on edge plasma profiles and magnetohydrodynamic (MHD) stability is central to the understanding of edge-localized modes (ELMs). Higher heating power should quicken the development of pressure and current-driven peeling-ballooning modes. NSTX ELMy H-mode discharges with NBI power of 4, 5 and 6 MW were analyzed with a python-based set of analysis tools that fit plasma profiles, compute kinetic equilibria, and evaluate the MHD stability with the code ELITE. Electron density and temperature from Thomson scattering measurements, and ion density, temperature, and rotation from Charge Exchange Recombination Spectroscopy were inputs to the kinetic equilibrium fits. The power scan provides an opportunity to compare the stability calculations from the ELITE (ideal) and M3D-C1 (resistive) codes. Preliminary analysis shows that edge pressure profiles for the 5 and 6 MW discharges are comparable, suggesting they both reach a stability boundary. The 4 MW case shows lower edge pressure, which is likely limited by edge transport below the edge stability boundary. This work was supported in part by the U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists (WDTS) under the Science Undergraduate Laboratory Internship (SULI) program.

  17. Separation of the principal HDL subclasses by iodixanol ultracentrifugation

    PubMed Central

    Harman, Nicola L.; Griffin, Bruce A.; Davies, Ian G.

    2013-01-01

    HDL subclasses detection, in cardiovascular risk, has been limited due to the time-consuming nature of current techniques. We have developed a time-saving and reliable separation of the principal HDL subclasses employing iodixanol density gradient ultracentrifugation (IxDGUC) combined with digital photography. HDL subclasses were separated in 2.5 h from prestained plasma on a three-step iodixanol gradient. HDL subclass profiles were generated by digital photography and gel scan software. Plasma samples (n = 46) were used to optimize the gradient for the resolution of HDL heterogeneity and to compare profiles generated by IxDGUC with gradient gel electrophoresis (GGE); further characterization from participants (n = 548) with a range of lipid profiles was also performed. HDL subclass profiles generated by IxDGUC were comparable to those separated by GGE as indicated by a significant association between areas under the curve for both HDL2 and HDL3 (HDL2, r = 0.896, P < 0.01; HDL3, r = 0.894, P < 0.01). The method was highly reproducible, with intra- and interassay coefficient of variation percentage < 5 for percentage area under the curve HDL2 and HDL3, and < 1% for peak Rf and peak density. The method provides time-saving and cost-effective detection and preparation of the principal HDL subclasses. PMID:23690506

  18. Characterization of magnetic field profiles at RFX-mod by Faraday rotation measurements

    NASA Astrophysics Data System (ADS)

    Auriemma, Fulvio; Brombin, Matteo; Canton, Alessandra; Giudicotti, Leonardo; Innocente, Paolo; Zilli, Enrico

    2009-11-01

    A multichannel far-infrared (FIR, λ=118.8 μm) polarimeter has been recently upgraded and re-installed on RFX-mod to measure the Faraday rotation angle along five vertical chords. Polarimetric data, associated with electron density profile, allow the reconstruction of the poloidal magnetic field profile. In this work the setup of the diagnostic is presented and the first Faraday rotation measurements are analyzed. The measurements have been performed at plasma current above 1.2 MA and electron density between 2 and 6x10^19 m-3. The actual S/N ratio is slightly lower than the expected one, due to electromagnetic coupling of the detectors with the saddle coils close to the polarimeter position. Due to this limit, only average information in the flat-top phase of the discharge could be so far obtained. The experimental data have been compared with the result of the μ&p equilibrium model [1], showing a good agreement between experiment and model, whereas the main differences are in the external region of the plasma. A different parameterization of the μ=μ0 J.B/B^2 profile has been proposed to enhance the agreement between model and experiment. [0pt] [1] Ortolani and Snack, World Scientific (1993) Singapore

  19. Powder free PECVD epitaxial silicon by plasma pulsing or increasing the growth temperature

    NASA Astrophysics Data System (ADS)

    Chen, Wanghua; Maurice, Jean-Luc; Vanel, Jean-Charles; Cabarrocas, Pere Roca i.

    2018-06-01

    Crystalline silicon thin films are promising candidates for low cost and flexible photovoltaics. Among various synthesis techniques, epitaxial growth via low temperature plasma-enhanced chemical vapor deposition is an interesting choice because of two low temperature related benefits: low thermal budget and better doping profile control. However, increasing the growth rate is a tricky issue because the agglomeration of clusters required for epitaxy leads to powder formation in the plasma. In this work, we have measured precisely the time evolution of the self-bias voltage in silane/hydrogen plasmas at millisecond time scale, for different values of the direct-current bias voltage applied to the radio frequency (RF) electrode and growth temperatures. We demonstrate that the decisive factor to increase the epitaxial growth rate, i.e. the inhibition of the agglomeration of plasma-born clusters, can be obtained by decreasing the RF OFF time or increasing the growth temperature. The influence of these two parameters on the growth rate and epitaxial film quality is also presented.

  20. Dynamic optimization of open-loop input signals for ramp-up current profiles in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Ren, Zhigang; Xu, Chao; Lin, Qun; Loxton, Ryan; Teo, Kok Lay

    2016-03-01

    Establishing a good current spatial profile in tokamak fusion reactors is crucial to effective steady-state operation. The evolution of the current spatial profile is related to the evolution of the poloidal magnetic flux, which can be modeled in the normalized cylindrical coordinates using a parabolic partial differential equation (PDE) called the magnetic diffusion equation. In this paper, we consider the dynamic optimization problem of attaining the best possible current spatial profile during the ramp-up phase of the tokamak. We first use the Galerkin method to obtain a finite-dimensional ordinary differential equation (ODE) model based on the original magnetic diffusion PDE. Then, we combine the control parameterization method with a novel time-scaling transformation to obtain an approximate optimal parameter selection problem, which can be solved using gradient-based optimization techniques such as sequential quadratic programming (SQP). This control parameterization approach involves approximating the tokamak input signals by piecewise-linear functions whose slopes and break-points are decision variables to be optimized. We show that the gradient of the objective function with respect to the decision variables can be computed by solving an auxiliary dynamic system governing the state sensitivity matrix. Finally, we conclude the paper with simulation results for an example problem based on experimental data from the DIII-D tokamak in San Diego, California.

  1. Recent RF Experiments and Application of RF Waves to Real-Time Control of Safety Factor Profile in JT-60U

    NASA Astrophysics Data System (ADS)

    Suzuki, T.; Isayama, A.; Ide, S.; Fujita, T.; Oikawa, T.; Sakata, S.; Sueoka, M.; Hosoyama, H.; JT-60 Team

    2005-09-01

    Two topics of applications of RF waves to current profile control in JT-60U are presented; application of lower-hybrid (LH) waves to safety factor profile control and electron cyclotron (EC) waves to neo-classical tearing mode (NTM) control. A real-time control system of safety factor (q) profile was developed. This system, for the first time, enables 1) real time evaluation of q profile using local magnetic pitch angle measurement by motional Stark effect (MSE) diagnostic and 2) control of current drive (CD) location (ρCD) by controlling the parallel refractive index N∥ of LH waves through control of phase difference (Δφ) of LH waves between multi-junction launcher modules. The method for real-time q profile evaluation was newly developed, without time-consuming reconstruction of equilibrium, so that the method requires less computational time. Safety factor profile by the real-time calculation agrees well with that by equilibrium reconstruction with MSE. The control system controls ρCD through Δφ in such a way to decrease the largest residual between the real-time evaluated q profile q(r) and its reference profile qref(r). The real-time control system was applied to a positive shear plasma (q(0)˜1). The reference q profile was set to monotonic positive shear profile having qref(0)=1.3. The real-time q profile approached to the qref(r) during application of real-time control, and was sustained for 3s, which was limited by the duration of the injected LH power. Temporal evolution of current profile was consistent with relaxation of inductive electric field induced by theoretical LH driven current. An m/n=3/2 NTM that appeared at βN˜3 was completely stabilized by ECCD applied to a fully-developed NTM. Precise ECCD at NTM island was essential for the stabilization. ECCD that was applied to resonant rational surface (q=3/2) before an NTM onset suppressed appearance of NTM. In order to keep NTM intensity below a level, ECCD before the mode onset was more effective than that after mode saturation.

  2. Hemostatic properties and protein expression profile of therapeutic apheresis plasma treated with amotosalen and ultraviolet A for pathogen inactivation.

    PubMed

    Ohlmann, Philippe; Hechler, Béatrice; Chafey, Philippe; Ravanat, Catherine; Isola, Hervé; Wiesel, Marie-Louise; Cazenave, Jean-Pierre; Gachet, Christian

    2016-09-01

    The INTERCEPT Blood System (IBS) using amotosalen-HCl and ultraviolet (UV)A inactivates a large spectrum of microbial pathogens and white blood cells in therapeutic plasma. Our aim was to evaluate to what extent IBS modifies the capacity of plasma to generate thrombin and induces qualitative or quantitative modifications of plasma proteins. Plasma units from four donors were collected by apheresis. Samples were taken before (control [CTRL]) and after IBS treatment and stored at -80°C until use. The activities of plasma coagulation factors and inhibitors and the thrombin generation potential were determined using assays measuring clotting times and the calibrated automated thrombogram (CAT), respectively. The proteomic profile of plasma proteins was examined using a two-dimensional differential in-gel electrophoresis (2D-DIGE) method. Nearly all of the procoagulant and antithrombotic factors tested retained at least 78% of their initial pre-IBS activity. Only FVII and FVIII displayed a lower level of conservation (67%), which nevertheless remained within the reference range for conventional plasma coagulation factors. The thrombin generation profile of plasma was conserved after IBS treatment. Among the 1331 protein spots revealed by 2D-DIGE analysis, only four were differentially expressed in IBS plasma compared to CTRL plasma and two were identified by mass spectrometric analysis as transthyretin and apolipoprotein A1. The IBS technique for plasma moderately decreases the activities of plasma coagulation factors and antithrombotic proteins, with no impact on the thrombin generation potential of plasma and very limited modifications of the proteomic profile. © 2016 AABB.

  3. Impact of Te and ne on edge current density profiles in ELM mitigated regimes on ASDEX Upgrade

    NASA Astrophysics Data System (ADS)

    Dunne, M. G.; Rathgeber, S.; Burckhart, A.; Fischer, R.; Giannone, L.; McCarthy, P. J.; Schneider, P. A.; Wolfrum, E.; the ASDEX Upgrade Team

    2015-01-01

    ELM resolved edge current density profiles are reconstructed using the CLISTE equilibrium code. As input, highly spatially and temporally resolved edge electron temperature and density profiles are used in addition to data from the extensive set of external poloidal field measurements available at ASDEX Upgrade, flux loop difference measurements, and current measurements in the scrape-off layer. Both the local and flux surface averaged current density profiles are analysed for several ELM mitigation regimes. The focus throughout is on the impact of altered temperature and density profiles on the current density. In particular, many ELM mitigation regimes rely on operation at high density. Two reference plasmas with type-I ELMs are analysed, one with a deuterium gas puff and one without, in order to provide a reference for the behaviour in type-II ELMy regimes and high density ELM mitigation with external magnetic perturbations at ASDEX Upgrade. For type-II ELMs it is found that while a similar pedestal top pressure is sustained at the higher density, the temperature gradient decreases in the pedestal. This results in lower local and flux surface averaged current densities in these phases, which reduces the drive for the peeling mode. No significant differences between the current density measured in the type-I phase and ELM mitigated phase is seen when external perturbations are applied, though the pedestal top density was increased. Finally, ELMs during the nitrogen seeded phase of a high performance discharge are analysed and compared to ELMs in the reference phase. An increased pedestal pressure gradient, which is the source of confinement improvement in impurity seeded discharges, causes a local current density increase. However, the increased Zeff in the pedestal acts to reduce the flux surface averaged current density. This dichotomy, which is not observed in other mitigation regimes, could act to stabilize both the ballooning mode and the peeling mode at the same time.

  4. Rotation in a reversed field pinch with active feedback stabilization of resistive wall modes

    NASA Astrophysics Data System (ADS)

    Cecconello, M.; Menmuir, S.; Brunsell, P. R.; Kuldkepp, M.

    2006-09-01

    Active feedback stabilization of multiple resistive wall modes (RWMs) has been successfully proven in the EXTRAP T2R reversed field pinch. One of the features of plasma discharges operated with active feedback stabilization, in addition to the prolongation of the plasma discharge, is the sustainment of the plasma rotation. Sustained rotation is observed both for the internally resonant tearing modes (TMs) and the intrinsic impurity oxygen ions. Good quantitative agreement between the toroidal rotation velocities of both is found: the toroidal rotation is characterized by an acceleration phase followed, after one wall time, by a deceleration phase that is slower than in standard discharges. The TMs and the impurity ions rotate in the same poloidal direction with also similar velocities. Poloidal and toroidal velocities have comparable amplitudes and a simple model of their radial profile reproduces the main features of the helical angular phase velocity. RWMs feedback does not qualitatively change the TMs behaviour and typical phenomena such as the dynamo and the 'slinky' are still observed. The improved sustainment of the plasma and TMs rotation occurs also when feedback only acts on internally non-resonant RWMs. This may be due to an indirect positive effect, through non-linear coupling between TMs and RWMs, of feedback on the TMs or to a reduced plasma-wall interaction affecting the plasma flow rotation. Electromagnetic torque calculations show that with active feedback stabilization the TMs amplitude remains well below the locking threshold condition for a thick shell. Finally, it is suggested that active feedback stabilization of RWMs and current profile control techniques can be employed simultaneously thus improving both the plasma duration and its confinement properties.

  5. Joint DIII-D/EAST research on the development of a high poloidal beta scenario for the steady state missions of ITER and CFETR

    NASA Astrophysics Data System (ADS)

    Garofalo, A. M.; Gong, X. Z.; Ding, S. Y.; Huang, J.; McClenaghan, J.; Pan, C. K.; Qian, J.; Ren, Q. L.; Staebler, G. M.; Chen, J.; Cui, L.; Grierson, B. A.; Hanson, J. M.; Holcomb, C. T.; Jian, X.; Li, G.; Li, M.; Pankin, A. Y.; Peysson, Y.; Zhai, X.; Bonoli, P.; Brower, D.; Ding, W. X.; Ferron, J. R.; Guo, W.; Lao, L. L.; Li, K.; Liu, H.; Lyv, B.; Xu, G.; Zang, Q.

    2018-01-01

    Experimental and modeling investigations on the DIII-D and EAST tokamaks show the attractive transport and stability properties of fully noninductive, high poloidal-beta (β P ) plasmas, and their suitability for steady-state operating scenarios in ITER and CFETR. A key feature of the high-β P regime is the large-radius (ρ > 0.6) internal transport barrier (ITB), often observed in all channels (ne, Te, Ti, rotation), and responsible for both excellent energy confinement quality and excellent stability properties. Experiments on DIII-D have shown that, with a large-radius ITB, very high β N and β P values (both ≥ 4) can be reached by taking advantage of the stabilizing effect of a nearby conducting wall. Synergistically, higher plasma pressure provides turbulence suppression by Shafranov shift, leading to ITB sustainment independent of the plasma rotation. Experiments on EAST have been used to assess the long pulse potential of the high-β P regime. Using RF-only heating and current drive, EAST achieved minute-long fully noninductive steady state H-mode operation with strike points on an ITER-like tungsten divertor. Improved confinement (relative to standard H-mode) and steady state ITB features are observed with a monotonic q-profile with q min ˜ 1.5. Separately, experiments have shown that increasing the density in plasmas driven by lower hybrid wave broadens the q-profile, a technique that could enable a large radius ITB. These experimental results have been used to validate MHD, current drive, and turbulent transport models, and to project the high-β P regime to a burning plasma. These projections suggest the Shafranov shift alone will not suffice to provide improved confinement (over standard H-mode) without rotation and rotation shear. However, increasing the negative magnetic shear (higher q on axis) provides a similar turbulence suppression mechanism to Shafranov shift, and can help devices such as ITER and CFETR achieve their steady-state fusion goals.

  6. Intrinsic Flow and Momentum Transport during Improved Confinement in MST

    NASA Astrophysics Data System (ADS)

    Craig, D.; Tan, E.; Schott, B.; Anderson, J. K.; Boguski, J.; Nornberg, M. D.; Xing, Z. A.

    2017-10-01

    Progress in absolute wavelength calibration of the Charge Exchange Recombination Spectroscopy (CHERS) system on MST has enabled new observations and analysis of intrinsic flow and momentum transport. Localized toroidal and poloidal flow measurements with systematic accuracy of +/- 3 km/s have been obtained during improved confinement Pulsed Parallel Current Drive (PPCD) plasmas at high plasma current (400-500 kA). The magnetic activity prior to and during the transition to improved confinement tends to increase the flow and sets the initial condition for the momentum profile evolution during improved confinement where intrinsic flow drive appears to weaken. Inboard flows change in time during PPCD, consistent with changes in the core-resonant m =1, n =6 tearing mode phase velocity. Outboard flows near the magnetic axis are time-independent, resulting in the development of a strongly sheared toroidal flow in the core and asymmetry in the poloidal flow profile. The deceleration of the n =6 mode during the period of improved confinement correlates well with the n =6 mode amplitude and is roughly consistent with the expected torque from eddy currents in the conducting shell. The level of Dα emission and secondary mode amplitudes (n =7-10) do not correlate with the mode deceleration suggesting that the momentum loss from charge exchange with neutrals and diffusion due to residual magnetic stochasticity are not significant in PPCD. This work has been supported by the U.S.D.O.E.

  7. Thomson scattering diagnostics of steady state and pulsed welding processes without and with metal vapor

    NASA Astrophysics Data System (ADS)

    Kühn-Kauffeldt, M.; Marqués, J.-L.; Schein, J.

    2015-01-01

    Thomson scattering is applied to measure temperature and density of electrons in the arc plasma of the direct current gas tungsten arc welding (GTAW) process and pulsed gas metal arc welding (GMAW) process. This diagnostic technique allows to determine these plasma parameters independent from the gas composition and heavy particles temperature. The experimental setup is adapted to perform measurements on stationary as well as transient processes. Spatial and temporal electron temperature and density profiles of a pure argon arc in the case of the GTAW process and argon arc with the presence of aluminum metal vapor in the case of the GMAW process were obtained. Additionally the data is used to estimate the concentration of the metal vapor in the GMAW plasma.

  8. Understanding rotation profile structures in ECH-heated plasmas using nonlinear gyrokinetic simulations

    NASA Astrophysics Data System (ADS)

    Wang, Weixing; Brian, B.; Ethier, S.; Chen, J.; Startsev, E.; Diamond, P. H.; Lu, Z.

    2015-11-01

    A non-diffusive momentum flux connecting edge momentum sources/sinks and core plasma flow is required to establish the off-axis peaked ion rotation profile typically observed in ECH-heated DIII-D plasmas without explicit external momentum input. The understanding of the formation of such profile structures provides an outstanding opportunity to test the physics of turbulence driving intrinsic rotation, and validate first-principles-based gyrokinetic simulation models. Nonlinear, global gyrokinetic simulations of DIII-D ECH plasmas indicate a substantial ITG fluctuation-induced residual stress generated around the region of peaked toroidal rotation, along with a diffusive momentum flux. The residual stress profile shows an anti-gradient, dipole structure, which is critical for accounting for the formation of the peaked rotation profile. It is showed that both turbulence intensity gradient and zonal flow ExB shear contribute to the generation of k// asymmetry needed for residual stress generation. By balancing the simulated residual stress and the momentum diffusion, a rotation profile is calculated. In general, the radial structure of core rotation profile is largely determined by the residual stress profile, while the amplitude of core rotation depends on the edge toroidal rotation velocity, which is determined by edge physics and used as a boundary condition in our model. The calculated core rotation profile is consistent with the experimental measurements. Also discussed is the modification of turbulence-generated Reynolds stress on poloidal rotation in those plasmas. Work supported by U.S. DOE Contract DE-AC02-09-CH11466.

  9. Control of plasma profiles and stability through localised Electron Cyclotron Current Drive

    NASA Astrophysics Data System (ADS)

    Merkulov, Oleksiy

    2006-06-01

    The work presented in this thesis addresses several topics from the physics of the magnetically confined plasma inside a tokamak. At the moment, the tokamak is the most successful concept for becoming a future thermonuclear reactor. However, there are plenty of physics and engineering problems to surpass before the prototype can become an economically and environmentally feasible device. The plasma in the tokamak experiences periodic oscillations of the central temperature and density when the safety factor, q, drops below unity on-axis. These oscillations are called the sawtooth instability and are the subject of the first part of this thesis. The sawtooth oscillations are characterised by the relatively slow rise phase, when the central temperature increases, and a following crash phase, when the central temperature drops. The energy, particles and plasma current are redistributed during the sawtooth crash. Obviously, this leads to a confinement degradation and moreover, the sawtooth instability can trigger potentially other more dangerous instabilities, such as a neoclassical tearing mode. The sawtooth period control is realised on the basis of the sawtooth trigger model, derived by Porcelli. The main idea of this model is that the sawtooth crash is triggered when the magnetic shear at the q=1 surface, s1, reaches a critical value which depends on the local plasma parameters. The magnetic shear, s, is a measure for the rate of change in the direction of the field line as a function of the position in the plasma. The sawtooth period can be changed by affecting the evolution of s1. The effects of the electron cyclotron current drive (ECCD) on the shear evolution are studied with a simple model for the poloidal field evolution. The results of the model are summarised in a form of a criterion for the amount of the non-inductive current drive required for sawtooth period control. The effects of the ECCD have been studied in the TEXTOR tokamak in order to confirm the outcome of the model. The observations are complicated by the unavoidable presence of concurrent heating, which also affects the sawtooth period. The effects of additional heating have been separated from the effects of current drive by normalising the sawtooth period, as a function of the power deposition radius, to a case with heating only. The results are in qualitative agreement with the predictions of the theory and confirm that the shear around the q=1 surface determines the moment of the sawtooth crash. The next topic addresses the current diffusion in the presence of the ECCD. It is known that the synergy between non-inductively driven current and the ohmic current can affect the current penetration. However, the standard method of calculations, which assumes neoclassical plasma resistivity, cannot describe the synergistic effects. We propose a model which combines a Fokker-Planck code and magnetic diffusion calculation in a self-consistent manner; where the plasma resistivity is approximated from the Fokker-Planck code at every time step. In this way the parallel electric field is no longer a constant input profile for the Fokker-Planck code, but is a result of calculations of the magnetic diffusion. This model allowed us to identify situations where the synergy between the driven and the ohmic currents becomes significant and affects the current penetration. Both the ECCD power and the electron density have been varied over a wide range of parameters, thus changing the well known non-linearity criterion for ECCD after Harvey. This criterion indicates the non-linear behaviour of the current drive efficiency and also appears to be a good predictor for the synergistic effects. The results are compared with the standard method of calculations which were supplied by the ASTRA transport code. The standard method and the Fokker-Planck code with the self-consistent electric field show similar results in the absence of the synergy and therefore for low values of the Harvey parameter. For co-ECCD and high values of the Harvey parameter substantial synergy between ECCD and the ohmic current is observed and leads to the generation of a large population of suprathermal electrons and slows down the current penetration. The synergy between counter-ECCD and the inductive current results in a decrease of the total driven current and a much smaller population of suprathermal electrons. Another plasma stability problem has been studied during the current ramp-up phase. Quiet and MHD free current ramp-up is a necessary requirement for a long and efficient flat-top phase. The current penetration in the plasma scenarios with various plasma ramp-up rates has been modelled with the ASTRA transport code. It is shown that in the absence of MHD activity the predictions of the ASTRA code are in a agreement with the experimental results.

  10. Balance of the stored energies sustained by the internal and edge transport barriers and effects of ELMs and L-H transitions in JT-60U

    NASA Astrophysics Data System (ADS)

    Kamada, Y.; Yoshida, M.; Sakamoto, Y.; Koide, Y.; Oyama, N.; Urano, H.; Kamiya, K.; Suzuki, T.; Isayama, A.; JT-60 Team

    2009-09-01

    To understand key physics processes determining radial profiles of the kinetic plasma parameters in the advanced tokamak operation scenarios, correlations between the edge transport barrier (ETB) and the internal transport barrier (ITB) have been studied in the JT-60U tokamak device. It has been found that the edge pedestal poloidal beta, βp-ped, increases almost linearly with the total poloidal beta, βp-tot, over a wide range of the plasma current for type I ELMing H-mode plasmas, and this dependence becomes stronger with increasing triangularity. This dependence is not due to the profile stiffness, since the dependence is the same regardless of the existence of ITB. As the stored energy inside the ITB-foot radius (WITB) increases, the total thermal stored energy (Wth) increases and then the pedestal stored energy (Wped) increases. On the other hand, as Wped increases, the ELM penetration expands more inwards and finally reaches the ITB-foot radius. At this situation, the ITB-foot radius cannot move outwards because of the erosion by ELMs. Then the fractions of WITB/Wth and Wped/Wth become almost constant. It has also been found that the type I ELM expels/decreases the edge toroidal momentum larger than the edge ion thermal energy. The ELM penetration for the toroidal rotation tends to be deeper than that for the ion temperature and can exceed the ITB-foot radius. The ELM penetration is deeper for CO-rotating plasmas than CTR rotating plasmas. In both cases, the ELM penetration is deeper in the order of the toroidal rotation (Vt), the ion temperature (Ti) and then the electron temperature (Te). The L-H transition also changes the Vt profile more significantly than the Ti profile. At the L-H transition, the pedestal Vt shifts into the CTR-direction deeply and suddenly without a change in Ti, and then the pedestal Vt grows further together with a growth of the pedestal Ti in a slower timescale. Such changes in Vt by ELMs and L-H transitions may affect degradation/evolution of ITBs.

  11. DOE Office of Scientific and Technical Information (OSTI.GOV)

    Groth, M; Ellis, R; Brooks, N

    A video camera system is described that measures the spatial distribution of visible line emission emitted from the main scrape-off layer (SOL) of plasmas in the DIII-D tokamak. A wide-angle lens installed on an equatorial port and an in-vessel mirror which intercepts part of the lens view provide simultaneous tangential views of the SOL on the low-field and high-field sides of the plasma's equatorial plane. Tomographic reconstruction techniques are used to calculate the 2-D poloidal profiles from the raw data, and 1-D poloidal profiles simulating chordal views of other optical diagnostics from the 2-D profiles. The 2-D profiles can bemore » compared with SOL plasma simulations; the 1-D profiles with measurements from spectroscopic diagnostics. Sample results are presented which elucidate carbon transport in plasmas with toroidally uniform injection of methane and argon transport in disruption mitigation experiments with massive gas jet injection.« less

  12. Tomography of a simply magnetized toroidal plasma

    NASA Astrophysics Data System (ADS)

    Ruggero, BARNI; Stefano, CALDIROLA; Luca, FATTORINI; Claudia, RICCARDI

    2018-02-01

    Optical emission spectroscopy is a passive diagnostic technique, which does not perturb the plasma state. In particular, in a hydrogen plasma, Balmer-alpha (H α ) emission can be easily measured in the visible range along a line of sight from outside the plasma vessel. Other emission lines in the visible spectral range from hydrogen atoms and molecules can be exploited too, in order to gather complementary pieces of information on the plasma state. Tomography allows us to capture bi-dimensional structures. We propose to adopt an emission spectroscopy tomography for studying the transverse profiles of magnetized plasmas when Abel inversion is not exploitable. An experimental campaign was carried out at the Thorello device, a simple magnetized torus. The characteristics of the profile extraction method, which we implemented for this purpose are discussed, together with a few results concerning the plasma profiles in a simply magnetized torus configuration.

  13. Effects of applied dc radial electric fields on particle transport in a bumpy torus plasma

    NASA Technical Reports Server (NTRS)

    Roth, J. R.

    1978-01-01

    The influence of applied dc radial electric fields on particle transport in a bumpy torus plasma is studied. The plasma, magnetic field, and ion heating mechanism are operated in steady state. Ion kinetic temperature is more than a factor of ten higher than electron temperature. The electric fields raise the ions to energies on the order of kilovolts and then point radially inward or outward. Plasma number density profiles are flat or triangular across the plasma diameter. It is suggested that the radial transport processes are nondiffusional and dominated by strong radial electric fields. These characteristics are caused by the absence of a second derivative in the density profile and the flat electron temperature profiles. If the electric field acting on the minor radius of the toroidal plasma points inward, plasma number density and confinement time are increased.

  14. Probing a dusty magnetized plasma with self-excited dust-density waves

    NASA Astrophysics Data System (ADS)

    Tadsen, Benjamin; Greiner, Franko; Piel, Alexander

    2018-03-01

    A cloud of nanodust particles is created in a reactive argon-acetylene plasma. It is then transformed into a dusty magnetized argon plasma. Plasma parameters are obtained with the dust-density wave diagnostic introduced by Tadsen et al. [Phys. Plasmas 22, 113701 (2015), 10.1063/1.4934927]. A change from an open to a cylindrically enclosed nanodust cloud, which was observed earlier, can now be explained by a stronger electric confinement if a vertical magnetic field is present. Using two-dimensional extinction measurements and the inverse Abel transform to determine the dust density, a redistribution of the dust with increasing magnetic induction is found. The dust-density profile changes from being peaked around the central void to being peaked at an outer torus ring resulting in a hollow profile. As the plasma parameters cannot explain this behavior, we propose a rotation of the nanodust cloud in the magnetized plasma as the origin of the modified profile.

  15. Recent Heating and Current Drive results on JET

    NASA Astrophysics Data System (ADS)

    Tuccillo, A. A.; Baranov, Y.; Barbato, E.; Bibet, Ph.; Castaldo, C.; Cesario, R.; Cocilovo, V.; Crisanti, F.; De Angelis, R.; Ekedahl, A. C.; Figueiredo, A.; Graham, M.; Granucci, G.; Hartmann, D.; Heikkinen, J.; Hellsten, T.; Imbeaux, F.; Jones, T. T. H.; Johnson, T.; Kirov, K. V.; Lamalle, P.; Laxaback, M.; Leuterer, F.; Litaudon, X.; Maget, P.; Mailloux, J.; Mantsinen, M. J.; Mayoral, M. L.; Meo, F.; Monakhov, I.; Nguyen, F.; Noterdaeme, J.-M.; Pericoli-Ridolfini, V.; Podda, S.; Panaccione, L.; Righi, E.; Rimini, F.; Sarazin, Y.; Sibley, A.; Staebler, A.; Tala, T.; Van Eester, D.

    2001-10-01

    An overview is presented of the results obtained on JET by the Heating and Current Drive Task Force (TF-H) in the period May 2000—March 2001. A strongly improved Lower Hybrid (LH) coupling was achieved by optimizing the plasma shape and by controlling the local edge density via the injection of CD4. Up to 4 MW have been coupled in type III ELMy H-mode and/or on Internal Transport Barrier (ITB) plasmas with reflection coefficients as low as 4%. Long lasting quasi steady-state ITBs have been obtained by adding the LH current to the bootstrap and beam driven components. Furthermore the use of LH in the pre-heat phase results in electron temperature in excess of 10 keV, deep negative magnetic shear and strongly reduced power threshold for ITB formation. Preliminary results on ICRF coupling are reported including the effect of CD4 injection and the commissioning of the wide band matching system on ELMy plasmas. IC CD scenarios have been studied in H and 3He minority and used to modify the stability of the sawtooth to influence the formation of seed islands for the appearance of NTM. Up to 3 MW of IC power was coupled in the high magnetic field fast wave CD scenario. Preliminary MSE measurements indicate differences in the current profiles between -90° and +90° phasing. Careful measurements of the toroidal rotation, in plasmas heated by ICRF only show some dependence on the position of the resonance layer. Finally the use of ICRF minority heating under real-time control, in response to measured plasma parameters to simulate the effect of alpha particles, is presented. ICRF heating results in ITER non-activated scenarios are reported in a companion paper.

  16. Performance improvement of doped TFET by using plasma formation concept

    NASA Astrophysics Data System (ADS)

    Soni, Deepak; Sharma, Dheeraj; Yadav, Shivendra; Aslam, Mohd.; Sharma, Neeraj

    2018-01-01

    Formation of abrupt doping profile at tunneling junction for the nanoscale tunnel field effect transistor (TFET) is a critical issue for attaining improved electrical behaviour. The realization of abrupt doping profile is more difficult in the case of physically doped TFETs due to material solubility limit. In this concern, we propose a novel design of TFET. For this, P+ (source)-I (channel)-N (drain) type structure has been considered, wherein a metal electrode is deposited over the source region. In addition to this, a negative voltage is applied to the source electrode (SE). It induces the surface plasma layer of holes in the source region, which is responsible for steepness in the bands at source/channel junction and provides the advantage of higher doping in source region without any addition of the physical impurity. The proposed modification is helpful for achieving steeper band bending at the source/channel interface, which enables higher tunneling generation rate of charge carriers at this interface and overcomes the issue of low ON-state current. Thus, the proposed device shows the increment of 2 decades in drain current and 252 mV reduction in threshold voltage compared with conventional device. The optimization of spacer length (LSG) between source/gate (LSG) and applied negative voltage (Vpg) over source electrode have been performed to obtain optimum drain current and threshold voltage (Vth). Further, for the suppression of ambipolar current, drain region is kept lightly doped, which reduces the ambipolar current up to level of Off state current. Moreover, in the proposed device gate electrode is underlapped for improving RF performance. It also reduces gate to drain capacitances (Cgd) and increases cut-off-frequency (fT), fmax, GBP, TFP. In addition to these, linearity analysis has been performed to validate the applicability of the device.

  17. Prediction of Human Pharmacokinetic Profile After Transdermal Drug Application Using Excised Human Skin.

    PubMed

    Yamamoto, Syunsuke; Karashima, Masatoshi; Arai, Yuta; Tohyama, Kimio; Amano, Nobuyuki

    2017-09-01

    Although several mathematical models have been reported for the estimation of human plasma concentration profiles of drug substances after dermal application, the successful cases that can predict human pharmacokinetic profiles are limited. Therefore, the aim of this study is to investigate the prediction of human plasma concentrations after dermal application using in vitro permeation parameters obtained from excised human skin. The in vitro skin permeability of 7 marketed drug products was evaluated. The plasma concentration-time profiles of the drug substances in humans after their dermal application were simulated using compartment models and the clinical pharmacokinetic parameters. The transdermal process was simulated using the in vitro skin permeation rate and lag time assuming a zero-order absorption. These simulated plasma concentration profiles were compared with the clinical data. The result revealed that the steady-state plasma concentration of diclofenac and the maximum concentrations of nicotine, bisoprolol, rivastigmine, and lidocaine after topical application were within 2-fold of the clinical data. Furthermore, the simulated concentration profiles of bisoprolol, nicotine, and rivastigmine reproduced the decrease in absorption due to drug depletion from the formulation. In conclusion, this simple compartment model using in vitro human skin permeation parameters as zero-order absorption predicted the human plasma concentrations accurately. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

  18. Characterization of pulsed metallic hydride vacuum arc discharge plasmas by optical emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Tang, Jian; Deng, Chunfeng; Wu, Chunlei; Lu, Biao; Hu, Yonghong

    2017-12-01

    The characteristics of plasmas in a titanium hydride vacuum arc ion source were experimentally investigated by a temporally- and spatially-integrated optical emission spectroscopy method. A plasma emission spectral fitting model was developed to calculate the plasmas temperature and relative density of each particle component, assuming plasmas were in local thermodynamic equilibrium state and optical thin in this study. The good agreement was founded between the predicted and measured spectra in the interesting regions of 330-340 nm and 498-503 nm for Ti+ ion and Ti atom respectively, while varying the plasma temperature and density. Compared with conventional Boltzmann plot method, this method, therefore, made a significant improvement on the plasma diagnosis in dealing with the spectral profile with many lines overlapped. At the same time, to understand the mechanism of the occluded-gas vacuum arc discharge plasmas, the plasmas emission spectra, ion relative density, and temperature with different discharge conditions were studied. The results indicated that the rate of Ti metal evaporation and H desorption from the electrode would be enhanced with arc current, and the ionization temperature increased with the feed-in power of arc discharge, leading more H+ and Ti+ ions, but reducing the H+ proportion in arc discharged plasmas.

  19. Predictions of high QDT in ITER H-mode plasmas

    NASA Astrophysics Data System (ADS)

    Budny, Robert

    2009-05-01

    Time-dependent integrated predictions of performance metrics such as the fusion power PDT, QDT≡ PDT/Pext, and alpha profiles are presented. The PTRANSP code (see R.V. Budny, R. Andre, G. Bateman, F. Halpern, C.E. Kessel, A. Kritz, and D. McCune, Nuclear Fusion 48 075005, and F. Halpern, A. Kritz, G. Bateman, R.V. Budny, and D. McCune, Phys. Plasmas 15 062505) is used, along with GLF23 to predict plasma profiles, NUBEAM for NNBI and alpha heating, TORIC for ICRH, and TORAY for ECRH. Effects of sawteeth mixing, beam steering, beam shine-through, radiation loss, ash accumulation, and toroidal rotation are included. A total heating of Pext=73MW is assumed to achieve H-mode during the density and current ramp-up phase. Various mixes of NNBI, ICRH, and ECRH heating schemes are compared. After steady state conditions are achieved, Pext is stepped down to lower values to explore high QDT. Physics and computation uncertainties lead to ranges in predictions for PDT and QDT. Physics uncertainties include the L->H and H->L threshold powers, pedestal height, impurity and ash transport, and recycling. There are considerably more uncertainties predicting the peak value for QDT than for PDT.

  20. Laser-heated emissive plasma probe.

    PubMed

    Schrittwieser, Roman; Ionita, Codrina; Balan, Petru; Gstrein, Ramona; Grulke, Olaf; Windisch, Thomas; Brandt, Christian; Klinger, Thomas; Madani, Ramin; Amarandei, George; Sarma, Arun K

    2008-08-01

    Emissive probes are standard tools in laboratory plasmas for the direct determination of the plasma potential. Usually they consist of a loop of refractory wire heated by an electric current until sufficient electron emission. Recently emissive probes were used also for measuring the radial fluctuation-induced particle flux and other essential parameters of edge turbulence in magnetized toroidal hot plasmas [R. Schrittwieser et al., Plasma Phys. Controlled Fusion 50, 055004 (2008)]. We have developed and investigated various types of emissive probes, which were heated by a focused infrared laser beam. Such a probe has several advantages: higher probe temperature without evaporation or melting and thus higher emissivity and longer lifetime, no deformation of the probe in a magnetic field, no potential drop along the probe wire, and faster time response. The probes are heated by an infrared diode laser with 808 nm wavelength and an output power up to 50 W. One probe was mounted together with the lens system on a radially movable probe shaft, and radial profiles of the plasma potential and of its oscillations were measured in a linear helicon discharge.

  1. Edge Ohmic Heating Experiment on HT-6M Tokamak

    NASA Astrophysics Data System (ADS)

    Gao, Xiang; Fan, Shuping; Li, Jian'gang; Meng, Yuedong; Luo, Jiarong; Yin, Fuxian; Zeng, Lei; Ding, Liancheng; Lin, Bili; Zhang, Wei; Han, Yuqing; Tong, Xingde; Luo, Lanchang; Gong, Xianzu; Jiang, Jiaguang; Wu, Mingjun; Yin, Fei

    1994-03-01

    An improved ohmic confinement has been achieved on HT-6M tokamak after application of edge ohmic heating pulse which makes plasma current rapidly ramp up (0.4 ms) in a ramp rate of 12 Ma/s. The improved ohmic confinement phase is characterized by (a) energy and particle confinement time increase, (b) non-symmetric increased density ne, (c) reduced Hα radiation, (d) increased Te and steeper Te, ne profile at the edge. The results from soft x-ray sawteeth inversion radius and βp + li/2 implied the anomalous current penetration.

  2. Accaleration of Electrons of the Outer Electron Radiation Belt and Auroral Oval Dynamics

    NASA Astrophysics Data System (ADS)

    Antonova, Elizaveta; Ovchinnikov, Ilya; Riazantseva, Maria; Znatkova, Svetlana; Pulinets, Maria; Vorobjev, Viachislav; Yagodkina, Oksana; Stepanova, Marina

    2016-07-01

    We summarize the results of experimental observations demonstrating the role of auroral processes in the formation of the outer electron radiation belt and magnetic field distortion during magnetic storms. We show that the auroral oval does not mapped to the plasma sheet proper (region with magnetic field lines stretched in the tailward direction). It is mapped to the surrounding the Earth plasma ring in which transverse currents are closed inside the magnetosphere. Such currents constitute the high latitude continuation of the ordinary ring current. Mapping of the auroral oval to the region of high latitude continuation of the ordinary ring current explains the ring like shape of the auroral oval with finite thickness near noon and auroral oval dynamics during magnetic storms. The auroral oval shift to low latitudes during storms. The development of the ring current produce great distortion of the Earth's magnetic field and corresponding adiabatic variations of relativistic electron fluxes. Development of the asymmetric ring current produce the dawn-dusk asymmetry of such fluxes. We analyze main features of the observed processes including formation of sharp plasma pressure profiles during storms. The nature of observed pressure peak is analyzed. It is shown that the observed sharp pressure peak is directly connected with the creation of the seed population of relativistic electrons. The possibility to predict the position of new radiation belt during recovery phase of the magnetic storm using data of low orbiting and ground based observations is demonstrated.

  3. Investigation of non-stationary self-focusing of intense laser pulse in cold quantum plasma using ramp density profile

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Habibi, M.; Ghamari, F.

    2012-11-15

    The authors have investigated the non-stationary self-focusing of Gaussian laser pulse in cold quantum plasma. In case of high dense plasma, the nonlinearity in the dielectric constant is mainly due to relativistic high intense interactions and quantum effects. In this paper, we have introduced a ramp density profile for plasma and presented graphically the behavior of spot size oscillations of pulse at rear and front portions of the pulse. It is observed that the ramp density profile and quantum effects play a vital role in stronger and better focusing at the rear of the pulse than at the front inmore » cold quantum plasmas.« less

  4. Radiated Power and Impurity Concentrations in the EXTRAP-T2R Reversed-Field Pinch

    NASA Astrophysics Data System (ADS)

    Corre, Y.; Rachlew, E.; Cecconello, M.; Gravestijn, R. M.; Hedqvist, A.; Pégourié, B.; Schunke, B.; Stancalie, V.

    2005-01-01

    A numerical and experimental study of the impurity concentration and radiation in the EXTRAP-T2R device is reported. The experimental setup consists of an 8-chord bolometer system providing the plasma radiated power and a vacuum-ultraviolet spectrometer providing information on the plasma impurity content. The plasma emissivity profile as measured by the bolometric system is peaked in the plasma centre. A one dimensional Onion Skin Collisional-Radiative model (OSCR) has been developed to compute the density and radiation distributions of the main impurities. The observed centrally peaked emissivity profile can be reproduced by OSCR simulations only if finite particle confinement time and charge-exchange processes between plasma impurities and neutral hydrogen are taken into account. The neutral hydrogen density profile is computed with a recycling code. Simulations show that recycling on metal first wall such as in EXTRAP-T2R (stainless steel vacuum vessel and molybdenum limiters) is compatible with a rather high neutral hydrogen density in the plasma centre. Assuming an impurity concentration of 10% for oxygen and 3% for carbon compared with the electron density, the OSCR calculation including lines and continuum emission reproduces about 60% of the total radiated power with a similarly centrally peaked emissivity profile. The centrally peaked emissivity profile is due to low ionisation stages and strongly radiating species in the plasma core, mainly O4+ (Be-like) and C3+ Li-like.

  5. Equator and High-Latitude Ionosphere-to-Magnetosphere Research

    DTIC Science & Technology

    2010-12-04

    characterizing plasma velocity profile in the heated region above HAARP has been clearly established. Specification of D region absorption from Digisonde...Electron density profile, Ground truth, Cal/Val, Doppler skymap, HAARP , Plasma velocity profile, Ionogram autoscaling, D region absorption...2  3  HAARP INVESTIGATIONS ............................................................................ 5  3.1

  6. The Physics of Local Helicity Injection Non-Solenoidal Tokamak Startup

    NASA Astrophysics Data System (ADS)

    Redd, A. J.; Barr, J. L.; Bongard, M. W.; Fonck, R. J.; Hinson, E. T.; Jardin, S.

    2013-10-01

    Non-solenoidal startup via Local Helicity Injection (LHI) uses compact current injectors to produce toroidal plasma current Ip up to 170 kA in the PEGASUS Toroidal Experiment, driven by 4-8 kA injector current on timescales of 5-20 milliseconds. Increasing the Ip buildup duration enables experimental demonstration of plasma position control on timescales relevant for high-current startup. LHI-driven discharges exhibit bursty MHD activity, apparently line-tied kinking of LHI-driven field lines, with the bursts correlating with rapid equilibrium changes, sharp Ip rises, and sharp drops in the injector impedance. Preliminary NIMROD results suggest that helical LHI-driven current channels remain coherent, with Ip increases due to reconnection between adjacent helical turns forming axisymmetric plasmoids, and corresponding sharp drops in the bias circuit impedance. The DC injector impedance is consistent with a space charge limit at low bias current and a magnetic limit at high bias current. Internal measurements show the current density profile starts strongly hollow and rapidly fills in during Ip buildup. Simulations of LHI discharges using the Tokamak Simulation Code (TSC) will provide insight into the detailed current drive mechanism and guide experiments on PEFASUS and NSTX-U. Work supported by US DOE Grants DE-FG02-96ER54375 and DE-SC0006928.

  7. Investigations of plasmoid reconnection in the presence of strong guide fields in CHI plasma start-up on HIST

    NASA Astrophysics Data System (ADS)

    Nagata, Masayoshi; Fujita, Akihiro; Ibragi, Youhei; Matsui, Takahiro; Kikuchi, Yusuke; Fukumoto, Naoyuki; Kanki, Takashi

    2017-10-01

    Plasmoid magnetic reconnections have been examined in the Coaxial Helicity Injection (CHI) experiments on HIST. Magnetic reconnections are required for the formation of closed flux surfaces in the transient-CHI start-up plasmas. So far, we have observed formation of plasmoids inside an elongated current layer to create the multiple X-points during the CHI process. According to the MHD simulation by F. Ebrahimi and R. Raman, the reconnection rate based on the plasmoid instability is faster than that by Sweet-Parker (S-P) model. To estimate the Lundquist number S number, we have measured spatial profiles of magnetic field strength, electron density and temperature in the current layer. In this meeting, we will present the effect of the guide (toroidal) magnetic field and mass (H, D and He) on the current layer thickness and reconnection rates of plasmoids. It is found that behavior of plasmoids is synchronized with Ion Doppler temperature, leading to ion heating.

  8. Verification and optimization of the CFETR baseline scenario

    NASA Astrophysics Data System (ADS)

    Zhao, D.; Lao, L. L.; Meneghini, O.; Staebler, G. M.; Candy, J.; Smith, S. P.; Snyder, P. B.; Prater, R.; Chen, X.; Chan, V. S.; Li, J.; Chen, J.; Shi, N.; Guo, W.; Pan, C.; Jian, X.

    2016-10-01

    The baseline scenario of China Fusion Engineering Test Reactor (CFETR) was designed starting from 0D calculations. The CFETR baseline scenario satisfies the minimum goal of Fusion Nuclear Science Facility aimed at bridging the gaps between ITER and DEMO. 1.5D calculations are presented to verify the on-going efforts in higher-dimensional modeling of CFETR. Steady-state scenarios are calculated self-consistently by the OMFIT integrated modeling framework that includes EFIT for equilibrium, ONETWO for sources and current, TGYRO for transport. With 68MW of neutral beam power and 8MW of ECH injected to the plasma, the average ion temperature is maintained at 15keV, while 150MW fusion power is produced. The neutral beams also drive 55% of the plasma current. Modest fast ion diffusion will reduce NBCD and affect the profile substantially. Top-launch ECH will increase the current drive and the power absorption rate. EPED model are being included. Work supported by U.S. DOE under DE-FC02-04ER54698 and the USTC CFETR contract.

  9. A new multi-line cusp magnetic field plasma device (MPD) with variable magnetic field

    NASA Astrophysics Data System (ADS)

    Patel, A. D.; Sharma, M.; Ramasubramanian, N.; Ganesh, R.; Chattopadhyay, P. K.

    2018-04-01

    A new multi-line cusp magnetic field plasma device consisting of electromagnets with core material has been constructed with a capability to experimentally control the relative volume fractions of magnetized to unmagnetized plasma volume as well as accurate control on the gradient length scales of mean density and temperature profiles. Argon plasma has been produced using a hot tungsten cathode over a wide range of pressures 5 × 10-5 -1 × 10-3 mbar, achieving plasma densities ranging from 109 to 1011 cm-3 and the electron temperature in the range 1-8 eV. The radial profiles of plasma parameters measured along the non-cusp region (in between two consecutive magnets) show a finite region with uniform and quiescent plasma, where the magnetic field is very low such that the ions are unmagnetized. Beyond that region, both plasma species are magnetized and the profiles show gradients both in temperature and density. The electrostatic fluctuation measured using a Langmuir probe radially along the non-cusp region shows less than 1% (δIisat/Iisat < 1%). The plasma thus produced will be used to study new and hitherto unexplored physics parameter space relevant to both laboratory multi-scale plasmas and astrophysical plasmas.

  10. Comparison of proteomic profiles of serum, plasma, and modified media supplements used for cell culture and expansion

    PubMed Central

    Ayache, Saleh; Panelli, Monica C; Byrne, Karen M; Slezak, Stefanie; Leitman, Susan F; Marincola, Francesco M; Stroncek, David F

    2006-01-01

    Background The culture and expansion of human cells for clinical use requires the presence of human serum or plasma in culture media. Although these supplements have been extensively characterized in their chemical composition, only recently it has been possible to provide by high throughput protein analysis, a comprehensive profile of the soluble factors contributing to cell survival. This study analyzed and compared the presence of 100 proteins including chemokines, cytokines and soluble factors in six different types of media supplements: serum, plasma, recalcified plasma, heat inactivated serum, heat inactivated plasma and heat inactivated recalcified plasma. Methods Serum, plasma, recalcified plasma, and heat inactivated supplements were prepared from ten healthy subjects. The levels of 100 soluble factors were measured in each sample using a multiplexed ELISA assay and compared by Eisen hierarchical clustering analysis. Results A comparison of serum and plasma levels of soluble factors found that 2 were greater in plasma but 18 factors were greater in serum including 11 chemokines. The levels of only four factors differed between recalcified plasma and plasma. Heat inactivation had the greatest effect on soluble factors. Supervised Eisen hierarchical clustering indicated that the differences between heat inactivated supplements and those that were not were greater than the differences within these two groups. The levels of 36 factors differed between heat inactivated plasma and plasma. Thirty one of these factors had a lower concentration in heat inactivated plasma including 12 chemokines, 4 growth factors, 4 matrix metalloproteases, and 3 adhesion molecules. Heat inactivated decalcified plasma is often used in place of heat inactivated serum and the levels of 19 soluble factors differed between these two supplements. Conclusion Our report provides a comprehensive protein profile of serum, plasma recalcified plasma, and heat inactivated supplements. This profile represents a qualitative and quantitative database that can aid in the selection of the appropriate blood derived supplement for human cell cultures with special requirements. PMID:17020621

  11. The effect of feedback-controlled divertor nitrogen seeding on the boundary plasma and power exhaust channel width in Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Labombard, B.; Brunner, D.; Kuang, A. Q.; McCarthy, W.; Terry, J. L.

    2017-10-01

    The scrape-off layer (SOL) power channel width, λq, is projected to be 0.5 mm in power reactors, based on multi-machine measurements of divertor target heat fluxes in H-mode at low levels of divertor dissipation. An important question is: does λq change with the level of divertor dissipation? We report results in which feedback controlled nitrogen seeding in the divertor was used to systematically vary divertor dissipation in a series of otherwise identical L-mode plasmas at three plasma currents: 0.55, 0.8 and 1.1 MA. Outer midplane profiles were recorded with a scanning Mirror Langmuir Probe; divertor plasma conditions were monitored with `rail' Langmuir probe and surface thermocouple arrays. Despite an order of magnitude reduction in divertor target heat fluxes (q// 400 MW m-2 to 40 MW m-2) and corresponding change in divertor regime from sheath-limited through high-recycling to near-detached, the upstream electron temperature profile is found to remain unchanged or to become slightly steeper in the near SOL and to drop significantly in the far SOL. Thus heat in the SOL appears to take advantage of this impurity radiation `heat sink' in the divertor by preferentially draining via the narrow (and perhaps an increasingly narrow) λq of the near SOL. Supported by USDoE award DE-FC02-99ER54512.

  12. Overview of results from the MST reversed field pinch experiment

    NASA Astrophysics Data System (ADS)

    Sarff, J. S.; Almagri, A. F.; Anderson, J. K.; Borchardt, M.; Carmody, D.; Caspary, K.; Chapman, B. E.; Den Hartog, D. J.; Duff, J.; Eilerman, S.; Falkowski, A.; Forest, C. B.; Goetz, J. A.; Holly, D. J.; Kim, J.-H.; King, J.; Ko, J.; Koliner, J.; Kumar, S.; Lee, J. D.; Liu, D.; Magee, R.; McCollam, K. J.; McGarry, M.; Mirnov, V. V.; Nornberg, M. D.; Nonn, P. D.; Oliva, S. P.; Parke, E.; Reusch, J. A.; Sauppe, J. P.; Seltzman, A.; Sovinec, C. R.; Stephens, H.; Stone, D.; Theucks, D.; Thomas, M.; Triana, J.; Terry, P. W.; Waksman, J.; Bergerson, W. F.; Brower, D. L.; Ding, W. X.; Lin, L.; Demers, D. R.; Fimognari, P.; Titus, J.; Auriemma, F.; Cappello, S.; Franz, P.; Innocente, P.; Lorenzini, R.; Martines, E.; Momo, B.; Piovesan, P.; Puiatti, M.; Spolaore, M.; Terranova, D.; Zanca, P.; Belykh, V.; Davydenko, V. I.; Deichuli, P.; Ivanov, A. A.; Polosatkin, S.; Stupishin, N. V.; Spong, D.; Craig, D.; Harvey, R. W.; Cianciosa, M.; Hanson, J. D.

    2013-10-01

    An overview of recent results from the MST programme on physics important for the advancement of the reversed field pinch (RFP) as well as for improved understanding of toroidal magnetic confinement more generally is reported. Evidence for the classical confinement of ions in the RFP is provided by analysis of impurity ions and energetic ions created by 1 MW neutral beam injection (NBI). The first appearance of energetic-particle-driven modes by NBI in a RFP plasma is described. MST plasmas robustly access the quasi-single-helicity state that has commonalities to the stellarator and ‘snake’ formation in tokamaks. In MST the dominant mode grows to 8% of the axisymmetric field strength, while the remaining modes are reduced. Predictive capability for tearing mode behaviour has been improved through nonlinear, 3D, resistive magnetohydrodynamic computation using the measured resistivity profile and Lundquist number, which reproduces the sawtooth cycle dynamics. Experimental evidence and computational analysis indicates two-fluid effects, e.g., Hall physics and gyro-viscosity, are needed to understand the coupling of parallel momentum transport and current profile relaxation. Large Reynolds and Maxwell stresses, plus separately measured kinetic stress, indicate an intricate momentum balance and a possible origin for MST's intrinsic plasma rotation. Gyrokinetic analysis indicates that micro-tearing modes can be unstable at high beta, with a critical gradient for the electron temperature that is larger than for tokamak plasmas by roughly the aspect ratio.

  13. Saturated Widths of Magnetic Islands in Tokamak Discharges

    NASA Astrophysics Data System (ADS)

    Halpern, F.; Pankin, A. Y.

    2005-10-01

    The new ISLAND module described in reference [1] implements a quasi-linear model to compute the widths of multiple magnetic islands driven by saturated tearing modes in toroidal plasmas of arbitrary aspect ratio and cross sectional shape. The distortion of the island shape caused by the radial variation in the perturbation is computed in the new module. In transport simulations, the enhanced transport caused by the magnetic islands has the effect of flattening the pressure and current density profiles. This self consistent treatment of the magnetic islands alters the development of the plasma profiles. In addition, it is found that islands closer to the magnetic axis influence the evolution of islands further out in the plasma. In order to investigate such phenomena, the ISLAND module is used within the BALDUR predictive modeling code to compute the widths of multiple magnetic islands in tokamak discharges. The interaction between the islands and sawtooth crashes is examined in simulations of DIII-D and JET discharges. The module is used to compute saturated neoclassical tearing mode island widths for multiple modes in ITER. Preliminary results for island widths in ITER are consistent with those presented [2] by Hegna. [1] F.D. Halpern, G. Bateman, A.H. Kritz and A.Y. Pankin, ``The ISLAND Module for Computing Magnetic Island Widths in Tokamaks,'' submitted to J. Plasma Physics (2005). [2] C.C. Hegna, 2002 Fusion Snowmass Meeting.

  14. Modelling of three dimensional equilibrium and stability of MAST plasmas with magnetic perturbations using VMEC and COBRA

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ham, C. J., E-mail: christopher.ham@ccfe.ac.uk; Chapman, I. T.; Kirk, A.

    2014-10-15

    It is known that magnetic perturbations can mitigate edge localized modes (ELMs) in experiments, for example, MAST [Kirk et al., Nucl. Fusion 53, 043007 (2013)]. One hypothesis is that the magnetic perturbations cause a three dimensional corrugation of the plasma and this corrugated plasma has different stability properties to peeling-ballooning modes compared to an axisymmetric plasma. It has been shown in an up-down symmetric plasma that magnetic perturbations in tokamaks will break the usual axisymmetry of the plasma causing three dimensional displacements [Chapman et al., Plasma Phys. Controlled Fusion 54, 105013 (2012)]. We produce a free boundary three-dimensional equilibrium ofmore » a lower single null MAST relevant plasma using VMEC [S. P. Hirshman and J. C. Whitson, Phys. Fluids 26, 3553 (1983)]. The safety factor and pressure profiles used for the modelling are similar to those deduced from axisymmetric analysis of experimental data with ELMs. We focus on the effect of applying n = 3 and n = 6 magnetic perturbations using the resonant magnetic perturbation (RMP) coils. A midplane displacement of over ±1 cm is seen when the full current is applied. The current in the coils is scanned and a linear relationship between coil current and midplane displacement is found. The pressure gradient in real space in different toroidal locations is shown to change when RMPs are applied. This effect should be taken into account when diagnosing plasmas with RMPs applied. The helical Pfirsch-Schlüter currents which arise as a result of the assumption of nested flux surfaces are estimated for this equilibrium. The effect of this non-axisymmetric equilibrium on infinite n ballooning stability is investigated using COBRA [Sanchez et al., J. Comput. Phys. 161, 576–588 (2000)]. The infinite n ballooning stability is analysed for two reasons; it may give an indication of the effect of non-axisymmetry on finite n peeling-ballooning modes, responsible for ELMs; and infinite n ballooning modes are correlated to kinetic ballooning modes which are thought to limit the pressure gradient of the pedestal [Snyder et al., Phys. Plasmas 16, 056118 (2009)]. The ballooning mode growth rate gains a variation in toroidal angle. The equilibria with midplane displacements due to RMP coils have a higher ballooning mode growth rate than the axisymmetric case and the possible implications are discussed.« less

  15. Recent progress of RF-dominated experiments on EAST

    NASA Astrophysics Data System (ADS)

    Liu, F. K.; Zhao, Y. P.; Shan, J. F.; Zhang, X. J.; Ding, B. J.; Wang, X. J.; Wang, M.; Xu, H. D.; Qin, C. M.; Li, M. H.; Gong, X. Z.; Hu, L. Q.; Wan, B. N.; Song, Y. T.; Li, J. G.

    2017-10-01

    The research of EAST program is mostly focused on the development of high performance steady state scenario with ITER-like poloidal configuration and RF-dominated heating schemes. With the enhanced ITER-relevant auxiliary heating and current drive systems, the plasma profile control by coupling/integration of various combinations has been investigated, including lower hybrid current drive (LHCD), electron cyclotron resonance heating (ECRH) and ion cyclotron resonance heating (ICRH). The 12 MW ICRH system has been installed on EAST. Heating and confinement studies using the Hydrogen Minority Heating scheme have been investigated. One of the importance challenges for EAST is coupling higher power into the core plasma, experiments including changing plasma position, electron density, local gas puffing and antenna phasing scanning were performed to improve ICRF coupling efficiency on EAST. Results show that local gas injection and reducing the k|| can improve the coupling efficiency directly. By means of the 4.6 GHz and 2.45 GHz LHCD systems, H-mode can be obtained and sustained at relatively high density, even up to ne ˜ 4.5 × 1019 m-3, where a current drive effect is still observed. Meanwhile, effect of source frequency (2.45GHz and 4.6GHz) on LHCD characteristic has been studied on EAST, showing that higher frequency improves penetration of the coupled LH (lower hybrid) power into the plasma core and leads to a better effect on plasma characteristics. Studies demonstrate the role of parasitic effects of edge plasma in LHCD and the mitigation by increasing source frequency. Experiments of effect of LH spectrum and plasma density on plasma characteristics are performed, suggesting the possibility of plasma control for high performance. The development of a 4MW ECRH system is in progress for the purpose of plasma heating and MHD control. The built ECRH system with 1MW source power has been successfully put into use on EAST in 2015. H-mode discharges with L-H transition triggered by ECRH injection were obtained and its effects on the electron temperature, particle confinement and the core MHD stabilities were observed. By further exploring and optimizing the RF combination for the sole RF heating and current drive regime, fully non-inductive H-mode discharges with Vloop˜0V has progressed steadily in the 2016 campaign. The overview of the significant progress of RF dominated experiments is presented in this paper.

  16. Integrated modelling of steady-state scenarios and heating and current drive mixes for ITER

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Murakami, Masanori; Park, Jin Myung; Giruzzi, G.

    2011-01-01

    Recent progress on ITER steady-state (SS) scenario modelling by the ITPA-IOS group is reviewed. Code-to-code benchmarks as the IOS group's common activities for the two SS scenarios (weak shear scenario and internal transport barrier scenario) are discussed in terms of transport, kinetic profiles, and heating and current drive (CD) sources using various transport codes. Weak magnetic shear scenarios integrate the plasma core and edge by combining a theory-based transport model (GLF23) with scaled experimental boundary profiles. The edge profiles (at normalized radius rho = 0.8-1.0) are adopted from an edge-localized mode-averaged analysis of a DIII-D ITER demonstration discharge. A fullymore » noninductive SS scenario is achieved with fusion gain Q = 4.3, noninductive fraction f(NI) = 100%, bootstrap current fraction f(BS) = 63% and normalized beta beta(N) = 2.7 at plasma current I(p) = 8MA and toroidal field B(T) = 5.3 T using ITER day-1 heating and CD capability. Substantial uncertainties come from outside the radius of setting the boundary conditions (rho = 0.8). The present simulation assumed that beta(N)(rho) at the top of the pedestal (rho = 0.91) is about 25% above the peeling-ballooning threshold. ITER will have a challenge to achieve the boundary, considering different operating conditions (T(e)/T(i) approximate to 1 and density peaking). Overall, the experimentally scaled edge is an optimistic side of the prediction. A number of SS scenarios with different heating and CD mixes in a wide range of conditions were explored by exploiting the weak-shear steady-state solution procedure with the GLF23 transport model and the scaled experimental edge. The results are also presented in the operation space for DT neutron power versus stationary burn pulse duration with assumed poloidal flux availability at the beginning of stationary burn, indicating that the long pulse operation goal (3000s) at I(p) = 9 MA is possible. Source calculations in these simulations have been revised for electron cyclotron current drive including parallel momentum conservation effects and for neutral beam current drive with finite orbit and magnetic pitch effects.« less

  17. Turbulence evolution and transport behavior during current ramp-up in ITER-like plasmas on DIII-D

    DOE PAGES

    McKee, George R.; Austin, Max E.; Boedo, Jose A.; ...

    2017-07-12

    Low-wavenumber density fluctuations exhibit unique characteristics during the current ramp-up phase of ITER-like discharges that can partially explain the challenges of correctly modeling transport behavior and predicting global plasma parameters during this period. A strong interaction takes place between the evolving transport, safety factor (q) and kinetic profiles as well as the appearance and evolution of low-order rational surfaces. Density fluctuations from 0.75 < ρ < 0.9 are transiently reduced to exceptionally low levels during early times and from 0.8 < ρ < 0.9 at late times in the ramp-up in a manner that is different from behavior observed duringmore » steady-state plasma conditions with similar values of q 95. Turbulence is suppressed as low-order-rational q-surfaces enter the plasma; the local electron temperature likewise exhibits transient increases during these periods of reduced fluctuations indicating changes in transport that impact temperature and consequently the evolution of current density and plasma inductance. These observations can explain discrepancies between CORSICA modelling and the higher electron temperature found previously over the outer half radius. Comparison of turbulence properties with time-varying linear growth rates with GYRO and GENE demonstrate qualitative consistency with measured fluctuation levels, but calculations don’t exhibit reduced growth rates near low-order rational surfaces, which is inconsistent with experimental observations. Here, this indicates a mechanism that can contribute to reconciling observed turbulence behavior with transport models, allowing for the development of more accurate predictive tools.« less

  18. Turbulence evolution and transport behavior during current ramp-up in ITER-like plasmas on DIII-D

    NASA Astrophysics Data System (ADS)

    McKee, G. R.; Austin, M.; Boedo, J.; Bravenec, R.; Holland, C.; Jackson, G.; Luce, T. C.; Rhodes, T. L.; Rudakov, D.; Wang, G.; Yan, Z.; Zeng, L.; Zhao, Y.

    2017-08-01

    Low-wavenumber density fluctuations exhibit unique characteristics during the current ramp-up phase of ITER-like discharges that can partially explain the challenges of correctly modeling transport behavior and predicting global plasma parameters during this period. A strong interaction takes place between the evolving transport, safety factor (q) and kinetic profiles as well as the appearance and evolution of low-order rational surfaces. Density fluctuations from 0.75  <  ρ  <  0.9 are transiently reduced to exceptionally low levels during early times and from 0.8  <  ρ  <  0.9 at late times in the ramp-up in a manner that is different from behavior observed during steady-state plasma conditions with similar values of q 95. Turbulence is suppressed as low-order-rational q-surfaces enter the plasma; the local electron temperature likewise exhibits transient increases during these periods of reduced fluctuations indicating changes in transport that impact temperature and consequently the evolution of current density and plasma inductance. These observations can explain discrepancies between CORSICA modelling and the higher electron temperature found previously over the outer half radius. Comparison of turbulence properties with time-varying linear growth rates with GYRO and GENE demonstrate qualitative consistency with measured fluctuation levels, but calculations don’t exhibit reduced growth rates near low-order rational surfaces, which is inconsistent with experimental observations. This indicates a mechanism that can contribute to reconciling observed turbulence behavior with transport models, allowing for the development of more accurate predictive tools.

  19. Towards self-consistent plasma modelisation in presence of neoclassical tearing mode and sawteeth: effects on transport coefficients

    NASA Astrophysics Data System (ADS)

    Basiuk, V.; Huynh, P.; Merle, A.; Nowak, S.; Sauter, O.; Contributors, JET; the EUROfusion-IM Team

    2017-12-01

    The neoclassical tearing modes (NTM) increase the effective heat and particle radial transport inside the plasma, leading to a flattening of the electron and ion temperature and density profiles at a given location depending on the safety factor q rational surface (Hegna and Callen 1997 Phys. Plasmas 4 2940). In burning plasma such as in ITER, this NTM-induced increased transport could reduce significantly the fusion performance and even lead to a disruption. Validating models describing the NTM-induced transport in present experiment is thus important to help quantifying this effect on future devices. In this work, we apply an NTM model to an integrated simulation of current, heat and particle transport on JET discharges using the European transport simulator. In this model, the heat and particle radial transport coefficients are modified by a Gaussian function locally centered at the NTM position and characterized by a full width proportional to the island size through a constant parameter adapted to obtain the best simulations of experimental profiles. In the simulation, the NTM model is turned on at the same time as the mode is triggered in the experiment. The island evolution is itself determined by the modified Rutherford equation, using self-consistent plasma parameters determined by the transport evolution. The achieved simulation reproduces the experimental measurements within the error bars, before and during the NTM. A small discrepancy is observed on the radial location of the island due to a shift of the position of the computed q = 3/2 surface compared to the experimental one. To explain such small shift (up to about 12% with respect to the position observed from the experimental electron temperature profiles), sensitivity studies of the NTM location as a function of the initialization parameters are presented. First results validate both the transport model and the transport modification calculated by the NTM model.

  20. Population Pharmacokinetics of Atazanavir in Patients with Human Immunodeficiency Virus Infection▿

    PubMed Central

    Colombo, Sara ; Buclin, Thierry; Cavassini, Matthias; Décosterd, Laurent A.; Telenti, Amalio; Biollaz, Jérôme; Csajka, Chantal

    2006-01-01

    Atazanavir (ATV) is a new azapeptide protease inhibitor recently approved and currently used at a fixed dose of either 300 mg once per day (q.d.) in combination with 100 mg ritonavir (RTV) or 400 mg q.d. without boosting. ATV is highly bound to plasma proteins and extensively metabolized by CYP3A4. Since ATV plasma levels are highly variable and seem to be correlated with both viral response and toxicity, dosage individualization based on plasma concentration monitoring might be indicated. This study aimed to assess the ATV pharmacokinetic profile in a target population of HIV patients, to characterize interpatient and intrapatient variability, and to identify covariates that might influence ATV disposition. A population analysis was performed with NONMEM with 574 plasma samples from a cohort of 214 randomly selected patients receiving ATV. A total of 346 randomly collected ATV plasma levels and 19 full concentration-time profiles at steady state were available. The pharmacokinetic parameter estimates were an oral clearance (CL) of 12.9 liters/h (coefficient of variation [CV], 26%), a volume of distribution of 88.3 liters (CV, 29%), an absorption rate constant of 0.405 h−1 (CV, 122%), and a lag time of 0.88 h. A relative bioavailability value was introduced to account for undercompliance due to infrequent follow-ups (0.81; CV, 45%). Among the covariates tested, only RTV significantly reduced CL by 46%, thereby increasing the ATV elimination half-life from 4.6 h to 8.8 h. The pharmacokinetic parameters of ATV were adequately described by a one-compartment population model. The concomitant use of RTV improved the pharmacokinetic profile. However, the remaining high interpatient variability suggests the possibility of an impact of unmeasured covariates, such as genetic traits or environmental influences. This population pharmacokinetic model, together with therapeutic drug monitoring and Bayesian dosage adaptation, can be helpful in the selection and adaptation of ATV doses. PMID:16940065

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