Sample records for yield d-t tokamak

  1. Controlling fusion yield in tokamaks with spin polarized fuel, and feasibility studies on the DIII-D tokamak

    DOE PAGES

    Pace, D. C.; Lanctot, M. J.; Jackson, G. L.; ...

    2015-09-21

    The march towards electricity production through tokamaks requires the construction of new facilities and the inevitable replacement of the previous generation. There are, however, research topics that are better suited to the existing tokamaks, areas of great potential that are not sufficiently mature for implementation in high power machines, and these provide strong support for a balanced policy that includes the redirection of existing programs. Spin polarized fusion, in which the nuclei of tokamak fuel particles are spin-aligned and favorably change both the fusion cross-section and the distribution of initial velocity vectors of charged fusion products, is described here asmore » an example of a technological and physics topic that is ripe for development in a machine such as the DIII-D tokamak. In this study, such research and development experiments may not be efficient at the ITER-scale, while the plasma performance, diagnostic access, and collaborative personnel available within the United States’ magnetic fusion research program, and at the DIII-D facility in particular, provide a unique opportunity to further fusion progress.« less

  2. The Role of Combined ICRF and NBI Heating in JET Hybrid Plasmas in Quest for High D-T Fusion Yield

    NASA Astrophysics Data System (ADS)

    Mantsinen, Mervi; Challis, Clive; Frigione, Domenico; Graves, Jonathan; Hobirk, Joerg; Belonohy, Eva; Czarnecka, Agata; Eriksson, Jacob; Gallart, Dani; Goniche, Marc; Hellesen, Carl; Jacquet, Philippe; Joffrin, Emmanuel; King, Damian; Krawczyk, Natalia; Lennholm, Morten; Lerche, Ernesto; Pawelec, Ewa; Sips, George; Solano, Emilia R.; Tsalas, Maximos; Valisa, Marco

    2017-10-01

    Combined ICRF and NBI heating played a key role in achieving the world-record fusion yield in the first deuterium-tritium campaign at the JET tokamak in 1997. The current plans for JET include new experiments with deuterium-tritium (D-T) plasmas with more ITER-like conditions given the recently installed ITER-like wall (ILW). In the 2015-2016 campaigns, significant efforts have been devoted to the development of high-performance plasma scenarios compatible with ILW in preparation of the forthcoming D-T campaign. Good progress was made in both the inductive (baseline) and the hybrid scenario: a new record JET ILW fusion yield with a significantly extended duration of the high-performance phase was achieved. This paper reports on the progress with the hybrid scenario which is a candidate for ITER longpulse operation (˜1000 s) thanks to its improved normalized confinement, reduced plasma current and higher plasma beta with respect to the ITER reference baseline scenario. The combined NBI+ICRF power in the hybrid scenario was increased to 33 MW and the record fusion yield, averaged over 100 ms, to 2.9x1016 neutrons/s from the 2014 ILW fusion record of 2.3x1016 neutrons/s. Impurity control with ICRF waves was one of the key means for extending the duration of the high-performance phase. The main results are reviewed covering both key core and edge plasma issues.

  3. μ CF Study of D/T and H/D/T Mixtures in Homogeneous and Inhomogeneous Medium, and Comparison of Their Fusion Yields

    NASA Astrophysics Data System (ADS)

    Eskandari, M. R.; Faghihi, F.; Gheisari, R.

    Muon reactivation coefficient are determined for muonic He (He = 42He = α , He = 23 He = h) for up to six (n = 1, 2, 3, ..., 6) states of formation and at temperature Tp = 100 eV and for various relative ion densities. In the next decade it may be possible to explore new conditions for further energy gain in muon catalyzed fusion system, μ CF, using nonuniform (temperature and density) plasma states. Here, we have considered a model for inhomogeneous μ CF for mixtures of D/T and H/D/T. Using coupled dynamical equations it is shown that the neutrons yield per muon injection, Yn (neutrons/muon), in the dt branch of an inhomogeneous H/D/T mixture is at least 2.24 times higher than similar homogeneous systems and this rate for a D/T mixture is 1.92. Also, we have compared the neutron yield in the dt branch of homogeneous D/T and H/D/T mixtures (temperature range T = 300-800 K, and density φ = 1 LHD). It is shown that Yn(D/T)/Yn(H/D/T) = 1.32, which is in good agreement with recently measured experimental values. In other words our calculations show that the addition of protonium to a D/T mixture leads to a significant decrease in the cycling rate for the physical conditions described herein.

  4. Extracting 3D Information from 1D and 2D Diagnostic Systems on the DIII-D Tokamak

    NASA Astrophysics Data System (ADS)

    Brookman, Michael

    2017-10-01

    The interpretation of tokamak data often hinges on assumptions of axisymetry and flux surface equilibria, neglecting 3D effects. This work discusses examples on the DIII-D tokamak where this assumption is an insufficient approximation, and explores the diagnostic information available to resolve 3D effects while preserving 1D profiles. Methods for extracting 3D data from the electron cyclotron emission radiometers, density profile reflectometer, and Thomson scattering system are discussed. Coordinating diagnostics around the tokamak shows the significance of 3D features, such as sawteeth[1] and resonant magnetic perturbations. A consequence of imposed 3D perturbations is a shift in major radius of measured profiles between diagnostics at different toroidal locations. Integrating different diagnostics requires a database containing information about their toroidal, poloidal, and radial locations. Through the data analysis framework OMFIT, it is possible to measure the magnitude of the apparent shifts from 3D effects and enforce consistency between diagnostics. Using the existing 1D and 2D diagnostic systems on DIII-D, this process allows the effects of the 3D perturbations on 1D profiles to be addressed. Supported by US DOE contracts DE-FC02-04ER54698, DE-FG03-97ER54415.

  5. Recent Results of IRAN-T1 Tokamak

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

    Dorranian, D.; Ghoranneviss, M.; Salem, M. K.

    2006-12-04

    In this article after introducing the IR-T1 tokamak and its diagnostic systems a brief discussion on the range of grossly stable operating conditions of its plasma by Hugill diagram is presented. Hard disruption instability is studied experimentally in the next part, which confirms that MHD behavior in small tokamaks can be characterized by a single parameter q(a), safety factor at plasma edge. Finally the characteristics of the new regime of IR-T1 are reported. By our new model of triggering different fields (toroidal, ohmic and vertical), the plasma duration time is increased up to 35 ms with Ip of about 25more » kA. By modifying capacitance and charging voltage of ohmic and vertical fields the spike oscillations which was appeared in the plasma behavior is taken out. The role of cleaning the vacuum chamber and using heavier gas for glow discharge and the effect of base pressure is described in detail.« less

  6. Equilibrium reconstruction with 3D eddy currents in the Lithium Tokamak eXperiment

    DOE PAGES

    Hansen, C.; Boyle, D. P.; Schmitt, J. C.; ...

    2017-04-18

    Axisymmetric free-boundary equilibrium reconstructions of tokamak plasmas in the Lithium Tokamak eXperiment (LTX) are performed using the PSI-Tri equilibrium code. Reconstructions in LTX are complicated by the presence of long-lived non-axisymmetric eddy currents generated by a vacuum vessel and first wall structures. To account for this effect, reconstructions are performed with additional toroidal current sources in these conducting regions. The eddy current sources are fixed in their poloidal distributions, but their magnitude is adjusted as part of the full reconstruction. Eddy distributions are computed by toroidally averaging currents, generated by coupling to vacuum field coils, from a simplified 3D filamentmore » model of important conducting structures. The full 3D eddy current fields are also used to enable the inclusion of local magnetic field measurements, which have strong 3D eddy current pick-up, as reconstruction constraints. Using this method, equilibrium reconstruction yields good agreement with all available diagnostic signals. Here, an accompanying field perturbation produced by 3D eddy currents on the plasma surface with a primarily n = 2, m = 1 character is also predicted for these equilibria.« less

  7. Preliminary measurements of neutrons from the D-D reaction in the COMPASS tokamak

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

    Dankowski, J., E-mail: jan.dankowski@ifj.edu.pl; Kurowski, A.; Twarog, D.

    Recent results of measured fast neutrons created in the D-D reaction on the COMPASS tokamak during ohmic discharges are presented in this paper. Two different type detectors were used during experiment. He-3 detectors and bubble detectors as a support. The measurements are an introduction for neutron diagnostic on tokamak COMPASS and monitoring neutrons during discharges with Neutral Beam Injection (NBI). The He-3 counters and bubble detectors were located in two positions near tokamak vacuum chamber at a distance less than 40 cm to the centre of plasma. The neutrons flux was observed in ohmic discharges. However, analysis of our resultsmore » does not indicate any clear source of neutrons production during ohmic discharges.« less

  8. Currents in the DIII-D Tokamak

    NASA Astrophysics Data System (ADS)

    Azari, A.; Eidietis, N. W.

    2012-10-01

    Loss of vertical control of an elongated tokamak plasma results in a vertical displacement event (VDE) which can induce large currents on open field lines and exert high JxB forces on in-vessel components. An array of first-wall tile current monitors on DIII-D provides direct measurement of the poloidal halo currents. These measurements are analyzed to create a database of halo current magnitude and asymmetry, which are found to lie within the ranges seen by numerous other tokamaks in the ITPA Disruption Database. In addition, an analysis of halo asymmetry rotation is presented, as rotation at the resonance frequencies of in-vessel components could lead to significant amplification of the halo forces. Halo current rotation is found to be far more prevalent in old (1997-2002) DIII-D halo current data than recent data (2009), perhaps due to a change in divertor geometry over that time.

  9. Georgia Tech Studies of Sub-Critical Advanced Burner Reactors with a D-T Fusion Tokamak Neutron Source for the Transmutation of Spent Nuclear Fuel

    NASA Astrophysics Data System (ADS)

    Stacey, W. M.

    2009-09-01

    The possibility that a tokamak D-T fusion neutron source, based on ITER physics and technology, could be used to drive sub-critical, fast-spectrum nuclear reactors fueled with the transuranics (TRU) in spent nuclear fuel discharged from conventional nuclear reactors has been investigated at Georgia Tech in a series of studies which are summarized in this paper. It is found that sub-critical operation of such fast transmutation reactors is advantageous in allowing longer fuel residence time, hence greater TRU burnup between fuel reprocessing stages, and in allowing higher TRU loading without compromising safety, relative to what could be achieved in a similar critical transmutation reactor. The required plasma and fusion technology operating parameter range of the fusion neutron source is generally within the anticipated operational range of ITER. The implications of these results for fusion development policy, if they hold up under more extensive and detailed analysis, is that a D-T fusion tokamak neutron source for a sub-critical transmutation reactor, built on the basis of the ITER operating experience, could possibly be a logical next step after ITER on the path to fusion electrical power reactors. At the same time, such an application would allow fusion to contribute to meeting the nation's energy needs at an earlier stage by helping to close the fission reactor nuclear fuel cycle.

  10. Radioactivity measurements of ITER materials using the TFTR D-T neutron field

    NASA Astrophysics Data System (ADS)

    Kumar, A.; Abdou, M. A.; Barnes, C. W.; Kugel, H. W.

    1994-06-01

    The availability of high D-T fusion neutron yields at TFTR has provided a useful opportunity to directly measure D-T neutron-induced radioactivity in a realistic tokamak fusion reactor environment for materials of vital interest to ITER. These measurements are valuable for characterizing radioactivity in various ITER candidate materials, for validating complex neutron transport calculations, and for meeting fusion reactor licensing requirements. The radioactivity measurements at TFTR involve potential ITER materials including stainless steel 316, vanadium, titanium, chromium, silicon, iron, cobalt, nickel, molybdenum, aluminum, copper, zinc, zirconium, niobium, and tungsten. Small samples of these materials were irradiated close to the plasma and just outside the vacuum vessel wall of TFTR, locations of different neutron energy spectra. Saturation activities for both threshold and capture reactions were measured. Data from dosimetric reactions have been used to obtain preliminary neutron energy spectra. Spectra from the first wall were compared to calculations from ITER and to measurements from accelerator-based tests.

  11. Radioactivity evaluation for the KSTAR tokamak.

    PubMed

    Kim, Hyunduk; Lee, Hee-Seock; Hong, Sukmo; Kim, Minho; Chung, Chinwha; Kim, Changsuk

    2005-01-01

    The deuterium-deuterium (D-D) reaction in the KSTAR (Korea Superconducting Tokamak Advanced Research) tokamak generates neutrons with a peak yield of 2.5 x 10(16) s(-1) through a pulse operation of 300 s. Since the structure material of the tokamak is irradiated with neutrons, this environment will restrict work around and inside the tokamak from a radiation protection physics point of view after shutdown. Identification of neutron-produced radionuclides and evaluation of absorbed dose in the structure material are needed to develop a guiding principle for radiation protection. The activation level was evaluated by MCNP4C2 and an inventory code, FISPACT. The absorbed dose in the working area decreased by 4.26 x 10(-4) mrem h(-1) in the inner vessel 1.5 d after shutdown. Furthermore, tritium strongly contributes to the contamination in the graphite tile. The amount of tritium produced by neutrons was 3.03 x 10(6) Bq kg(-1) in the carbon graphite of a plasma-facing wall.

  12. Polarized fusion, its implications, and plans for a proof-of-principle experiment at the DIII-D tokamak

    NASA Astrophysics Data System (ADS)

    Sandorfi, A. M.; Deur, A.; Lowry, M. M.; Wei, X.; Pace, D.; Eidietis, N.; Hyatt, A.; Jackson, G. L.; Lanctot, M.; Smith, S.; St-John, H.; Miller, G. W.; Zheng, X.; Baylor, L. R.

    2015-10-01

    The cross section for the primary fusion reaction in a tokamak, D+t --> α +n, would increase by a factor of 1.5 if the fuels were spin polarized parallel to the local field, rather than randomly oriented. Simulations show further gains in reaction rate would accompany this increase in large-scale machines such as ITER, due to increased alpha heating. The potential realization of such benefits rests on the crucial question of the survival of spin polarization for periods comparable to the energy containment time. Despite encouraging calculations, technical challenges in preparing and handling polarized materials have prevented any direct tests. Advances in three areas - polarized material technologies developed for nuclear and particle physics as well as medical imaging, polymer pellets developed for Inertial Confinement, and cryogenic injection guns developed for fueling tokamaks - have matured to the point where a direct in situ measurement is possible using the mirror reaction, D+3He --> α +p. Designs and simulations of a proof-of-principle experiment at the DIII-D tokamak in San Diego will be discussed. Work carried out under US DOE Contract DE-AC05-06OR23177 supporting Jefferson Lab and General Atomics Internal R&D funding.

  13. CXSFIT Code Application to Process Charge-Exchange Recombination Spectroscopy Data at the T-10 Tokamak

    NASA Astrophysics Data System (ADS)

    Serov, S. V.; Tugarinov, S. N.; Klyuchnikov, L. A.; Krupin, V. A.; von Hellermann, M.

    2017-12-01

    The applicability of the CXSFIT code to process experimental data from Charge-eXchange Recombination Spectroscopy (CXRS) diagnostics at the T-10 tokamak is studied with a view to its further use for processing experimental data at the ITER facility. The design and operating principle of the CXRS diagnostics are described. The main methods for processing the CXRS spectra of the 5291-Å line of C5+ ions at the T-10 tokamak (with and without subtraction of parasitic emission from the edge plasma) are analyzed. The method of averaging the CXRS spectra over several shots, which is used at the T-10 tokamak to increase the signal-to-noise ratio, is described. The approximation of the spectrum by a set of Gaussian components is used to identify the active CXRS line in the measured spectrum. Using the CXSFIT code, the ion temperature in ohmic discharges and discharges with auxiliary electron cyclotron resonance heating (ECRH) at the T-10 tokamak is calculated from the CXRS spectra of the 5291-Å line. The time behavior of the ion temperature profile in different ohmic heating modes is studied. The temperature profile dependence on the ECRH power is measured, and the dynamics of ECR removal of carbon nuclei from the T-10 plasma is described. Experimental data from the CXRS diagnostics at T-10 substantially contribute to the implementation of physical programs of studies on heat and particle transport in tokamak plasmas and investigation of geodesic acoustic mode properties.

  14. Comparison of 2D simulations of detached divertor plasmas with divertor Thomson measurements in the DIII-D tokamak

    DOE PAGES

    Rognlien, Thomas D.; McLean, Adam G.; Fenstermacher, Max E.; ...

    2017-01-27

    A modeling study is reported using new 2D data from DIII-D tokamak divertor plasmas and improved 2D transport model that includes large cross-field drifts for the numerically difficult H-mode regime. The data set, which spans a range of plasmas densities for both forward and reverse toroidal magnetic field (B t) over a range of plasma densities, is provided by divertor Thomson scattering (DTS). Measurements utilizing X-point sweeping give corresponding 2D profiles of electron temperature (T e) and density (n e) across both divertor legs for individual discharges. The calculations show the same features of in/out plasma asymmetries as measured inmore » the experiment, with the normal B t direction (ion ∇B drift toward the X-point) having higher n e and lower T e in the inner divertor leg than outer. Corresponding emission data for total radiated power shows a strong inner-divertor/outer-divertor asymmetry that is reproduced by the simulations. Furthermore, these 2D UEDGE transport simulations are enabled for steep-gradient H-mode conditions by newly implemented algorithms to control isolated grid-scale irregularities.« less

  15. Gamma ray imager on the DIII-D tokamak

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

    Pace, D. C., E-mail: pacedc@fusion.gat.com; Taussig, D.; Eidietis, N. W.

    2016-04-15

    A gamma ray camera is built for the DIII-D tokamak [J. Luxon, Nucl. Fusion 42, 614 (2002)] that provides spatial localization and energy resolution of gamma flux by combining a lead pinhole camera with custom-built detectors and optimized viewing geometry. This diagnostic system is installed on the outer midplane of the tokamak such that its 123 collimated sightlines extend across the tokamak radius while also covering most of the vertical extent of the plasma volume. A set of 30 bismuth germanate detectors can be secured in any of the available sightlines, allowing for customizable coverage in experiments with runaway electronsmore » in the energy range of 1–60 MeV. Commissioning of the gamma ray imager includes the quantification of electromagnetic noise sources in the tokamak machine hall and a measurement of the energy spectrum of background gamma radiation. First measurements of gamma rays coming from the plasma provide a suitable testbed for implementing pulse height analysis that provides the energy of detected gamma photons.« less

  16. Gamma ray imager on the DIII-D tokamak

    DOE PAGES

    Pace, D. C.; Cooper, C. M.; Taussig, D.; ...

    2016-04-13

    A gamma ray camera is built for the DIII-D tokamak [J. Luxon, Nucl. Fusion 42, 614 (2002)] that provides spatial localization and energy resolution of gamma flux by combining a lead pinhole camera with custom-built detectors and optimized viewing geometry. This diagnostic system is installed on the outer midplane of the tokamak such that its 123 collimated sightlines extend across the tokamak radius while also covering most of the vertical extent of the plasma volume. A set of 30 bismuth germanate detectors can be secured in any of the available sightlines, allowing for customizable coverage in experiments with runaway electronsmore » in the energy range of 1- 60 MeV. Commissioning of the gamma ray imager includes the quantification of electromagnetic noise sources in the tokamak machine hall and a measurement of the energy spectrum of background gamma radiation. In conclusion, first measurements of gamma rays coming from the plasma provide a suitable testbed for implementing pulse height analysis that provides the energy of detected gamma photons.« less

  17. Tokamak foundation in USSR/Russia 1950-1990

    NASA Astrophysics Data System (ADS)

    Smirnov, V. P.

    2010-01-01

    In the USSR, nuclear fusion research began in 1950 with the work of I.E. Tamm, A.D. Sakharov and colleagues. They formulated the principles of magnetic confinement of high temperature plasmas, that would allow the development of a thermonuclear reactor. Following this, experimental research on plasma initiation and heating in toroidal systems began in 1951 at the Kurchatov Institute. From the very first devices with vessels made of glass, porcelain or metal with insulating inserts, work progressed to the operation of the first tokamak, T-1, in 1958. More machines followed and the first international collaboration in nuclear fusion, on the T-3 tokamak, established the tokamak as a promising option for magnetic confinement. Experiments continued and specialized machines were developed to test separately improvements to the tokamak concept needed for the production of energy. At the same time, research into plasma physics and tokamak theory was being undertaken which provides the basis for modern theoretical work. Since then, the tokamak concept has been refined by a world-wide effort and today we look forward to the successful operation of ITER.

  18. Full orbit computations of ripple-induced fusion {alpha}-particle losses from burning tokamak plasmas

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

    McClements, K.G.

    A full orbit code is used to compute collisionless losses of fusion {alpha} particles from three proposed burning plasma tokamaks: the International Tokamak Experimental Reactor (ITER); a spherical tokamak power plant (STPP) [T. C. Hender, A. Bond, J. Edwards, P. J. Karditsas, K. G. McClements, J. Mustoe, D. V. Sherwood, G. M. Voss, and H. R. Wilson, Fusion Eng. Des. 48, 255 (2000)]; and a spherical tokamak components test facility (CTF) [H. R. Wilson, G. M. Voss, R. J. Akers, L. Appel, A. Dnestrovskij, O. Keating, T. C. Hender, M. J. Hole, G. Huysmans, A. Kirk, P. J. Knight, M.more » Loughlin, K. G. McClements, M. R. O'Brien, and D. Yu. Sychugov, Proceedings of the 20th IAEA Fusion Energy Conference, Invited Paper FT/3-1Ra]. It has been suggested that {alpha} particle transport could be enhanced due to cyclotron resonance with the toroidal magnetic field ripple. However, calculations for inductive operation in ITER yield a loss rate that appears to be broadly consistent with the predictions of guiding center theory, falling monotonically as the number of toroidal field coils N is increased (and hence the ripple amplitude is decreased). For STPP and CTF the loss rate does not decrease monotonically with N, but collisionless losses are generally low in absolute terms. As in the case of ITER, there is no evidence that finite Larmor radius effects would seriously degrade fusion {alpha}-particle confinement.« less

  19. Effect of 3D magnetic perturbations on divertor conditions and detachment in tokamak and stellarator

    DOE PAGES

    Ahn, J. -W.; Briesemester, A. R.; Kobayashi, M.; ...

    2017-06-22

    Enhanced perpendicular heat and momentum transport induces parallel pressure loss leading to divertor detachment, which can be produced by the increase of density in 2D tokamaks. However, in the 3D configurations such as tokamaks with 3D fields and stellarators, the fraction of perpendicular transport can be higher even in a lower density regime, which could lead to the early transition to detachment without passing through the high-recycling regime. 3D fields applied to the limiter tokamak plasmas produce edge stochastic layers close to the last closed flux surface (LCFS), which can allow for enhanced perpendicular transport and indeed the absence ofmore » high recycling regime and early detachment have been observed in TEXTOR and Tore Supra. However, in the X-point divertor tokamaks with the applied 3D fields, the parallel transport is still dominant and the detachment facilitation has not been observed yet. Rather, 3D fields affected detachment adversely under certain conditions, either by preventing detachment onset as seen in DIII-D or by re-attaching the existing detached plasma as shown in NSTX. The possible way for strong 3D effects to induce access to the early detachment in divertor tokamaks appears to be via significant perpendicular loss of parallel momentum by frictional force for the counter-streaming flows between neighboring flow channels in the divertor. In principle, the adjacent lobes in the 3D divertor tokamak may generate the counter-streaming flow channels. However, an EMC3-EIRENE simulation for ITER H-mode plasmas demonstrated that screened RMP leads to significantly reduced counter-flows near the divertor target, therefore the momentum loss effect leading to detachment facilitation is expected to be small. This is consistent with the observation in LHD, which showed screening (amplification) of RMP fields in the attachment (stable detachment) case. In conclusion, work for optimal parameter window for best divertor operation scenario is

  20. Effect of 3D magnetic perturbations on divertor conditions and detachment in tokamak and stellarator

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

    Ahn, J. -W.; Briesemester, A. R.; Kobayashi, M.

    Enhanced perpendicular heat and momentum transport induces parallel pressure loss leading to divertor detachment, which can be produced by the increase of density in 2D tokamaks. However, in the 3D configurations such as tokamaks with 3D fields and stellarators, the fraction of perpendicular transport can be higher even in a lower density regime, which could lead to the early transition to detachment without passing through the high-recycling regime. 3D fields applied to the limiter tokamak plasmas produce edge stochastic layers close to the last closed flux surface (LCFS), which can allow for enhanced perpendicular transport and indeed the absence ofmore » high recycling regime and early detachment have been observed in TEXTOR and Tore Supra. However, in the X-point divertor tokamaks with the applied 3D fields, the parallel transport is still dominant and the detachment facilitation has not been observed yet. Rather, 3D fields affected detachment adversely under certain conditions, either by preventing detachment onset as seen in DIII-D or by re-attaching the existing detached plasma as shown in NSTX. The possible way for strong 3D effects to induce access to the early detachment in divertor tokamaks appears to be via significant perpendicular loss of parallel momentum by frictional force for the counter-streaming flows between neighboring flow channels in the divertor. In principle, the adjacent lobes in the 3D divertor tokamak may generate the counter-streaming flow channels. However, an EMC3-EIRENE simulation for ITER H-mode plasmas demonstrated that screened RMP leads to significantly reduced counter-flows near the divertor target, therefore the momentum loss effect leading to detachment facilitation is expected to be small. This is consistent with the observation in LHD, which showed screening (amplification) of RMP fields in the attachment (stable detachment) case. In conclusion, work for optimal parameter window for best divertor operation scenario is

  1. Tangential System of Thomson Scattering for Tokamak T-15

    NASA Astrophysics Data System (ADS)

    Asadulin, G. M.; Bel'bas, I. S.; Gorshkov, A. V.

    2017-12-01

    Two systems of Thomson scattering diagnostics, with vertical and tangential probing, are used in the D-shaped plasma cross section in tokamak T-15. The tangential system allows measuring plasma temperature and density profiles along the major radius of the tokamak. This paper presents the tangential system project. The system is based on a Nd:YAG laser with wavelength of 1064 nm, pulse energy of 3 J, pulse duration of 10 ns, and repetition rate of 100 Hz. The chosen geometry allows collecting light from ten uniformly spaced points. Optimization of the registration system has been accomplished. The collected light will be transmitted through an optical fiber bundle with diameter of 3 mm and quartz fibers (numerical aperture is 0.22). Six-channel polychromators based on high-contrast interference filters have been chosen as spectral equipment. The radiation will be registered by avalanche photodiodes. The technique of electron temperature and density measurement is described, and estimation of its accuracy is carried out. The proposed system allows measuring the electron temperature with accuracy not worse than 10% within the range of 50 eV to 10 keV on the pinch edge over the internal contour, from 20 eV to 9 keV in the plasma central region, and from 2 eV to 400 eV on the pinch edge over the outer contour. The estimation is made for electron density of not less than 2.6 × 1013 cm-3.

  2. Developing physics basis for the snowflake divertor in the DIII-D tokamak

    NASA Astrophysics Data System (ADS)

    Soukhanovskii, V. A.; Allen, S. L.; Fenstermacher, M. E.; Lasnier, C. J.; Makowski, M. A.; McLean, A. G.; Meyer, W. H.; Ryutov, D. D.; Kolemen, E.; Groebner, R. J.; Hyatt, A. W.; Leonard, A. W.; Osborne, T. H.; Petrie, T. W.; Watkins, J.

    2018-03-01

    Recent DIII-D results demonstrate that the snowflake (SF) divertor geometry (see standard divertor) enables significant manipulation of divertor heat transport for heat spreading and reduction in attached and radiative divertor regimes, between and during edge localized modes (ELMs), while maintaining good H-mode confinement. Snowflake divertor configurations have been realized in the DIII-D tokamak for several seconds in H-mode discharges with heating power P_NBI ≤slant 4 -5 MW and a range of plasma currents I_p=0.8-1.2 MA. In this work, inter-ELM transport and radiative SF divertor properties are studied. Significant impact of geometric properties on SOL and divertor plasma parameters, including increased poloidal magnetic flux expansion, divertor magnetic field line length and divertor volume, is confirmed. In the SF-minus configuration, heat deposition is affected by the geometry, and peak divertor heat fluxes are significantly reduced. In the SF-plus and near-exact SF configurations, divertor peak heat flux reduction and outer strike point heat flux profile broadening are observed. Inter-ELM sharing of power and particle fluxes between the main and additional snowflake divertor strike points has been demonstrated. The additional strike points typically receive up to 10-15% of total outer divertor power. Measurements of electron pressure and poloidal beta βp support the theoretically proposed churning mode that is driven by toroidal curvature and vertical pressure gradient in the weak poloidal field region. A comparison of the 4-4.5 MW NBI-heated H-mode plasmas with radiative SF divertor and the standard radiative divertor (both induced with additional gas puffing) shows a nearly complete power detachment and broader divertor radiated power distribution in the SF, as compared to a partial detachment and peaked localized radiation in the standard divertor. However, insignificant difference in the detachment onset w.r.t. density between the SF and the standard

  3. Summary of Apollo; A D- sup 3 He tokamak reactor design

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

    Kulcinski, G.L.; Blanchard, T.P.; El-Guebaly, L.A.

    1992-07-01

    In this paper, the key features of Apollo, a conceptual D-{sup 3}He tokamak reactor for commercial electricity production, are summarized. The 1000-MW (electric) design utilizes direct conversion of transport, neutron, and bremsstrahlung radiation power. The direct conversion method uses reactants, and the thermal conversion cycle uses an organic coolant. Apollo operates in the first-stability regime, with a major radius of 7.89 m, a peak magnetic field on the toroidal field coils of 19.3 T, a 53-MA plasma current, and a 6.7% beta value. The low neutron production of the D-{sup 3}He fuel cycle greatly reduces the radiation damage rate andmore » allows a full-lifetime first wall and structure made of standard steels with only slight modifications to reduce activation levels.« less

  4. Influence of molecular clustering on the interpretation of diffractograms of hydrocarbon films from tokamak T-10

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

    Neverov, V. S., E-mail: vs-never@hotmail.com; Voloshinov, V. V., E-mail: vladimir.voloshinov@gmail.com; Kukushkin, A. B., E-mail: kukushkin-ab@nrcki.ru

    2015-12-15

    The influence of molecular clustering on the formerly suggested interpretation of diffraction patterns of hydrocarbon films formed in the vacuum vessel of the tokamak T-10 is analyzed numerically. The simulation of clustering of simple hydrocarbon molecules C(D, H){sub 4}, C{sub 2}(D, H){sub 4}, and C{sub 6}(D, H){sub 6} and molecules composed of curved graphene (fullerenes and toroidal nanotubes) is carried out with the rigid body molecular dynamics method. It is shown that formerly neglected atomic correlations C–C and C–D(H) in the amorphous hydrocarbon component decrease the calculated values of the scattered intensity in the range of scattering vector modulus 5more » < q < 20 nm{sup –1} because of homogenization of scatters on the spatial scale of ∼1 nm. The allowance for these correlations does not change the diffraction patterns in the range q > 20 nm{sup –1}. The results suggest the necessity to introduce to the procedure of determining the structural content of the films, similar to those from the tokamak T-10, the clusters formed by the van der Waals adhesion of hydrocarbon molecules to “graphene” nanoparticles. This simplifies the mathematical optimization to the former level of complexity—but for an extended ensemble of objects—and makes it possible to calculate the diffraction patterns of these objects using the distributed computing resources. A modified algorithm of structural content identification on the basis of joint X-ray and neutron diffractometry is suggested.« less

  5. Destruction of tungsten limiters in the T-10 Tokamak under high plasma heat loads

    NASA Astrophysics Data System (ADS)

    Grashin, S. A.; Arkhipov, I. I.; Budaev, V. P.; Giniyatulin, R. N.; Karpov, A. V.; Klyuchnikov, L. A.; Krupin, V. A.; Litunovskiy, N. V.; Masul, I. V.; Makhankov, F. N.; Martynenko, Yu V.; Sarytchev, D. V.; Solomatin, R. Yu; Khimchenko, L. N.

    2017-10-01

    Tungsten limiters were tested in the T-10 tokamak. The limiters were made from the ITER-grade WMP “POLEMA” tungsten. The influence of the edge tokamak plasma on tungsten limiters leads to significant cracking of tungsten. The heat load of up to 2 MW · m-2 leads to the micro-crack development at the grain boundaries accompanied by the loss of grains. The heat loads that exceed 5 MW · m-2 lead to the macro crack development. Under the present T-10 tokamak conditions, the heat and particle fluxes in the edge plasma lead to the significant destruction of tungsten limiters during the experimental campaign. During the disruption and runaway electron formation, extreme heat loads of more than 1 GW/m2 cause strong melting of tungsten on the inner and outer part of the ring limiter.

  6. Tokamak Equilibrium Reconstruction with MSE-LS Data in DIII-D

    NASA Astrophysics Data System (ADS)

    Lao, L.; Grierson, B.; Burrell, K. H.

    2016-10-01

    Equilibrium analysis of plasmas in DIII-D using EFIT was upgraded to include the internal magnetic field determined from spectroscopic measurements of motional-Stark-effect line-splitting (MSE-LS). MSE-LS provides measurements of the magnitude of the internal magnetic field, rather than the pitch angle as provided by MSE line-polarization (MSE-LP) used in most tokamaks to date. EFIT MSE-LS reconstruction algorithms and verifications are described. The capability of MSE-LS to provide significant constraints on the equilibrium analysis is evaluated. Reconstruction results with both synthetic and experimental MSE-LS data from 10 DIII-D discharges run over a range of conditions show that MSE-LS measurements can contribute to the equilibrium reconstruction of pressure and safety factor profiles. Adequate MSE-LS measurement accuracy and number of spatial locations are necessary. The 7 available experimental measurements provide useful additional constraints when used with other internal measurements. Using MSE-LS as the only internal measurement yields less current profile information. Work supported by the PPPL Subcontract S013769-F and US DOE under DE-FC02-04ER54698.

  7. Li Experiments at the Tokamak T-11M Toward PFC Concept of Steady State Tokamak-Reactor

    NASA Astrophysics Data System (ADS)

    Mirnov, S. V.

    2009-11-01

    As practical method of using a liquid lithium as a renewable plasma-facing component (PCF) for steady state tokamak-reactor the concept of lithium emitter-collector is considered [1]. It is based on lithium filled capillary porous system proposed by V.A. Evtikhin et al. (1996). The lithium circulation process consists of four steps: (1) Li emission from the PFC emitter into the plasma; (2) plasma boundary cooling by non-coronal Li radiation; (3) Li ion capture by the collector (before they are lost to the tokamak chamber wall); (4) Li return from the collector to the emitter. T-11M tokamak experiments have used three local rail limiters made from lithium, molybdenum and graphite as lithium collectors. The lithium behavior was studied by analysis of the witness samples, and by a mobile graphite probe. The key findings are: (1) lithium collection on the ion side of the lithium limiter is 2-3 times larger than on the electron side; (2) total efficiency of Li collection integrated over all three rail limiters can reach 50-70% of the lithium emission during the discharge pulse, while the theoretical limit is about 90%. [1] S.V. Mirnov, J. Nucl. Mat., 390-391, 876 (2009).

  8. Alpha-channeling simulation experiment in the DIII-D tokamak.

    PubMed

    Wong, K L; Budny, R; Nazikian, R; Petty, C C; Greenfield, C M; Heidbrink, W W; Ruskov, E

    2004-08-20

    Alfvén instabilities can reduce the central magnetic shear via redistribution of energetic ions. They can sustain a steady state internal transport barrier as demonstrated in this DIII-D tokamak experiment. Improvement in burning plasma performance based on this mechanism is discussed.

  9. Compact D-D/D-T neutron generators and their applications

    NASA Astrophysics Data System (ADS)

    Lou, Tak Pui

    2003-10-01

    Neutron generators based on the 2H(d,n)3He and 3H(d,n)4He fusion reactions are the most commonly available neutron sources. The applications of current commercial neutron generators are often limited by their low neutron yield and their short operational lifetime. A new generation of D-D/D-T fusion-based neutron generators has been designed at Lawrence Berkeley National Laboratory (LBNL) by using high current ion beams hitting on a self-loading target that has a large surface area to dissipate the heat load. This thesis describes the rationale behind the new designs and their potential applications. A survey of other neutron sources is presented to show their advantages and disadvantages compared to the fusion-based neutron generator. A prototype neutron facility was built at LBNL to test these neutron generators. High current ion beams were extracted from an RF-driven ion source to produce neutrons. With an average deuteron beam current of 24 mA and an energy of 100 keV, a neutron yield of >109 n/s has been obtained with a D-D coaxial neutron source. Several potential applications were investigated by using computer simulations. The computer code used for simulations and the variance reduction techniques employed were discussed. A study was carried out to determine the neutron flux and resolution of a D-T neutron source in thermal neutron scattering applications for condensed matter experiments. An error analysis was performed to validate the scheme used to predict the resolution. With a D-T neutron yield of 1014 n/s, the thermal neutron flux at the sample was predicted to be 7.3 x 105 n/cm2s. It was found that the resolution of cold neutrons was better than that of thermal neutrons when the duty factor is high. This neutron generator could be efficiently used for research and educational purposes at universities. Additional applications studied were positron production and Boron Neutron Capture Therapy (BNCT). The neutron flux required for positron production

  10. Evidence of toroidally localized turbulence with applied 3D fields in the DIII-D tokamak

    DOE PAGES

    Wilcox, R. S.; Shafer, M. W.; Ferraro, N. M.; ...

    2016-09-21

    New evidence indicates that there is significant 3D variation in density fluctuations near the boundary of weakly 3D tokamak plasmas when resonant magnetic perturbations are applied to suppress transient edge instabilities. The increase in fluctuations is concomitant with an increase in the measured density gradient, suggesting that this toroidally localized gradient increase could be a mechanism for turbulence destabilization in localized flux tubes. Two-fluid magnetohydrodynamic simulations find that, although changes to the magnetic field topology are small, there is a significant 3D variation of the density gradient within the flux surfaces that is extended along field lines. This modeling agreesmore » qualitatively with the measurements. The observed gradient and fluctuation asymmetries are proposed as a mechanism by which global profile gradients in the pedestal could be relaxed due to a local change in the 3D equilibrium. In conclusion, these processes may play an important role in pedestal and scrape-off layer transport in ITER and other future tokamak devices with small applied 3D fields.« less

  11. Chaotic density fluctuations in L-mode plasmas of the DIII-D tokamak

    DOE PAGES

    Maggs, J. E.; Rhodes, Terry L.; Morales, G. J.

    2015-03-05

    Analysis of the time series obtained with the Doppler backscattering system (DBS) in the DIII-D tokamak shows that intermediate wave number plasma density fluctuations in low confinement (L-mode) tokamak plasmas are chaotic. Here, the supporting evidence is based on the shape of the power spectrum; the location of the signal in the complexity-entropy plane (C-H plane); and the population of the corresponding Bandt-Pompe probability distributions.

  12. Study of SOL in DIII-D tokamak with SOLPS suite of codes.

    NASA Astrophysics Data System (ADS)

    Pankin, Alexei; Bateman, Glenn; Brennan, Dylan; Coster, David; Hogan, John; Kritz, Arnold; Kukushkin, Andrey; Schnack, Dalton; Snyder, Phil

    2005-10-01

    The scrape-of-layer (SOL) region in DIII-D tokamak is studied with the SOLPS integrated suite of codes. The SOLPS package includes the 3D multi-species Monte-Carlo neutral code EIRINE and 2D multi-fluid code B2. The EIRINE and B2 codes are cross-coupled through B2-EIRINE interface. The results of SOLPS simulations are used in the integrated modeling of the plasma edge in DIII-D tokamak with the ASTRA transport code. Parameterized dependences for neutral particle fluxes that are computed with the SOLPS code are implemented in a model for the H-mode pedestal and ELMs [1] in the ASTRA code. The effects of neutrals on the H-mode pedestal and ELMs are studied in this report. [1] A. Y. Pankin, I. Voitsekhovitch, G. Bateman, et al., Plasma Phys. Control. Fusion 47, 483 (2005).

  13. Nonlinear Fluid Model Of 3-D Field Effects In Tokamak Plasmas

    NASA Astrophysics Data System (ADS)

    Callen, J. D.; Hegna, C. C.; Beidler, M. T.

    2017-10-01

    Extended MHD codes (e.g., NIMROD, M3D-C1) are beginning to explore nonlinear effects of small 3-D magnetic fields on tokamak plasmas. To facilitate development of analogous physically understandable reduced models, a fluid-based dynamic nonlinear model of these added 3-D field effects in the base axisymmetric tokamak magnetic field geometry is being developed. The model incorporates kinetic-based closures within an extended MHD framework. Key 3-D field effects models that have been developed include: 1) a comprehensive modified Rutherford equation for the growth of a magnetic island that includes the classical tearing and NTM perturbed bootstrap current drives, externally applied magnetic field and current drives, and classical and neoclassical polarization current effects, and 2) dynamic nonlinear evolution of the plasma toroidal flow (radial electric field) in response to the 3-D fields. An application of this model to RMP ELM suppression precipitated by an ELM crash will be discussed. Supported by Office of Fusion Energy Sciences, Office of Science, Dept. of Energy Grants DE-FG02-86ER53218 and DE-FG02-92ER54139.

  14. High power heating of magnetic reconnection in merging tokamak experiments

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

    Ono, Y.; Tanabe, H.; Gi, K.

    2015-05-15

    Significant ion/electron heating of magnetic reconnection up to 1.2 keV was documented in two spherical tokamak plasma merging experiment on MAST with the significantly large Reynolds number R∼10{sup 5}. Measured 1D/2D contours of ion and electron temperatures reveal clearly energy-conversion mechanisms of magnetic reconnection: huge outflow heating of ions in the downstream and localized heating of electrons at the X-point. Ions are accelerated up to the order of poloidal Alfven speed in the reconnection outflow region and are thermalized by fast shock-like density pileups formed in the downstreams, in agreement with recent solar satellite observations and PIC simulation results. The magneticmore » reconnection efficiently converts the reconnecting (poloidal) magnetic energy mostly into ion thermal energy through the outflow, causing the reconnection heating energy proportional to square of the reconnecting (poloidal) magnetic field B{sub rec}{sup 2}  ∼  B{sub p}{sup 2}. The guide toroidal field B{sub t} does not affect the bulk heating of ions and electrons, probably because the reconnection/outflow speeds are determined mostly by the external driven inflow by the help of another fast reconnection mechanism: intermittent sheet ejection. The localized electron heating at the X-point increases sharply with the guide toroidal field B{sub t}, probably because the toroidal field increases electron confinement and acceleration length along the X-line. 2D measurements of magnetic field and temperatures in the TS-3 tokamak merging experiment also reveal the detailed reconnection heating mechanisms mentioned above. The high-power heating of tokamak merging is useful not only for laboratory study of reconnection but also for economical startup and heating of tokamak plasmas. The MAST/TS-3 tokamak merging with B{sub p} > 0.4 T will enables us to heat the plasma to the alpha heating regime: T{sub i} > 5 keV without using any additional heating

  15. Developing physics basis for the snowflake divertor in the DIII-D tokamak

    DOE PAGES

    Soukhanovskii, V. A.; Allen, S. L.; Fenstermacher, M. E.; ...

    2018-02-01

    Recent DIII-D results demonstrate that the snowflake (SF) divertor geometry (cf. standard divertor) enables significant manipulation of divertor heat transport for heat spreading and reduction in attached and radiative divertor regimes, between and during edge localized modes (ELMs), while maintaining good H-mode confinement. Snowflake divertor configurations have been realized in the DIII-D tokamak for several seconds in H-mode discharges with heating power PNBImore » $$\\leqslant$$ 4-5 MW and a range of plasma currents Ip = 0.8-1.2 MA. In this work, inter-ELM transport and radiative SF divertor properties are studied. Significant impact of geometric properties on SOL and divertor plasma parameters, including increased poloidal magnetic flux expansion, divertor magnetic field line length and divertor volume, is confirmed. In the SF-minus configuration, heat deposition is affected by the geometry, and peak divertor heat fluxes are significantly reduced. In the SF-plus and near-exact SF configurations, divertor peak heat flux reduction and outer strike point heat flux profile broadening are observed. Inter-ELM sharing of power and particle fluxes between the main and additional snowflake divertor strike points has been demonstrated. The additional strike points typically receive up to 10-15% of total outer divertor power. Measurements of electron pressure and poloidal beta !p support the theoretically proposed churning mode that is driven by toroidal curvature and vertical pressure gradient in the weak poloidal field region. A comparison of the 4-4.5 MW NBI-heated H-mode plasmas with radiative SF divertor and the standard radiative divertor (both induced with additional gas puffing) shows a nearly complete power detachment and broader divertor radiated power distribution in the SF, as compared to a partial detachment and peaked localized radiation in the standard divertor. However, insignificant difference in the detachment onset w.r.t. density between the SF and

  16. Developing physics basis for the snowflake divertor in the DIII-D tokamak

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

    Soukhanovskii, V. A.; Allen, S. L.; Fenstermacher, M. E.

    Recent DIII-D results demonstrate that the snowflake (SF) divertor geometry (cf. standard divertor) enables significant manipulation of divertor heat transport for heat spreading and reduction in attached and radiative divertor regimes, between and during edge localized modes (ELMs), while maintaining good H-mode confinement. Snowflake divertor configurations have been realized in the DIII-D tokamak for several seconds in H-mode discharges with heating power PNBImore » $$\\leqslant$$ 4-5 MW and a range of plasma currents Ip = 0.8-1.2 MA. In this work, inter-ELM transport and radiative SF divertor properties are studied. Significant impact of geometric properties on SOL and divertor plasma parameters, including increased poloidal magnetic flux expansion, divertor magnetic field line length and divertor volume, is confirmed. In the SF-minus configuration, heat deposition is affected by the geometry, and peak divertor heat fluxes are significantly reduced. In the SF-plus and near-exact SF configurations, divertor peak heat flux reduction and outer strike point heat flux profile broadening are observed. Inter-ELM sharing of power and particle fluxes between the main and additional snowflake divertor strike points has been demonstrated. The additional strike points typically receive up to 10-15% of total outer divertor power. Measurements of electron pressure and poloidal beta !p support the theoretically proposed churning mode that is driven by toroidal curvature and vertical pressure gradient in the weak poloidal field region. A comparison of the 4-4.5 MW NBI-heated H-mode plasmas with radiative SF divertor and the standard radiative divertor (both induced with additional gas puffing) shows a nearly complete power detachment and broader divertor radiated power distribution in the SF, as compared to a partial detachment and peaked localized radiation in the standard divertor. However, insignificant difference in the detachment onset w.r.t. density between the SF and

  17. Probing spherical tokamak plasmas using charged fusion products

    NASA Astrophysics Data System (ADS)

    Boeglin, Werner U.; Perez, Ramona V.; Darrow, Douglass S.; Cecconello, Marco; Klimek, Iwona; Allan, Scott Y.; Akers, Rob J.; Jones, Owen M.; Keeling, David L.; McClements, Ken G.; Scannell, Rory

    2015-11-01

    The detection of charged fusion products, such as protons and tritons resulting from D(d,p)t reactions, can be used to determine the fusion reaction rate profile in large spherical tokamak plasmas with neutral beam heating. The time resolution of a diagnostic of this type makes it possible to study the slowly-varying beam density profile, as well as rapid changes resulting from MHD instabilities. A 4-channel prototype proton detector (PD) was installed and operated on the MAST spherical tokamak in August/September 2013, and a new 6-channel system for the NSTX-U spherical tokamak is under construction. PD and neutron camera measurements obtained on MAST will be compared with TRANSP calculations, and the design of the new NSTX-U system will be presented, together with the first results from this diagnostic, if available. Supported in part by DOE DE-SC0001157.

  18. High-dynamic-range neutron time-of-flight detector used to infer the D(t,n){sup 4}He and D(d,n){sup 3}He reaction yield and ion temperature on OMEGA

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

    Forrest, C. J., E-mail: cforrest@lle.rochester.edu; Glebov, V. Yu.; Goncharov, V. N.

    Upgraded microchannel-plate–based photomultiplier tubes (MCP-PMT’s) with increased stability to signal-shape linearity have been implemented on the 13.4-m neutron time-of-flight (nTOF) detector at the Omega Laser Facility. This diagnostic uses oxygenated xylene doped with diphenyloxazole C{sub 15}H{sub 11}NO + p-bis-(o-methylstyryl)-benzene (PPO + bis-MSB) wavelength shifting dyes and is coupled through four viewing ports to fast-gating MCP-PMT’s, each with a different gain to allow one to measure the light output over a dynamic range of 1 × 10{sup 6}. With these enhancements, the 13.4-m nTOF can measure the D(t,n){sup 4}He and D(d,n){sup 3}He reaction yields and average ion temperatures in a singlemore » line of sight. Once calibrated for absolute neutron sensitivity, the nTOF detectors can be used to measure the neutron yield from 1 × 10{sup 9} to 1 × 10{sup 14} and the ion temperature with an accuracy approaching 5% for both the D(t,n){sup 4}He and D(d,n){sup 3}He reactions.« less

  19. Inductive flux usage and its optimization in tokamak operation

    DOE PAGES

    Luce, Timothy C.; Humphreys, David A.; Jackson, Gary L.; ...

    2014-07-30

    The energy flow from the poloidal field coils of a tokamak to the electromagnetic and kinetic stored energy of the plasma are considered in the context of optimizing the operation of ITER. The goal is to optimize the flux usage in order to allow the longest possible burn in ITER at the desired conditions to meet the physics objectives (500 MW fusion power with energy gain of 10). A mathematical formulation of the energy flow is derived and applied to experiments in the DIII-D tokamak that simulate the ITER design shape and relevant normalized current and pressure. The rate ofmore » rise of the plasma current was varied, and the fastest stable current rise is found to be the optimum for flux usage in DIII-D. A method to project the results to ITER is formulated. The constraints of the ITER poloidal field coil set yield an optimum at ramp rates slower than the maximum stable rate for plasmas similar to the DIII-D plasmas. Finally, experiments in present-day tokamaks for further optimization of the current rise and validation of the projections are suggested.« less

  20. Structure of chaotic magnetic field lines in IR-T1 tokamak due to ergodic magnetic limiter

    NASA Astrophysics Data System (ADS)

    Ahmadi, S.; Salar Elahi, A.; Ghorannevis, M.

    2018-03-01

    In this paper we have studied an Ergodic Magnetic Limiter (EML) based chaotic magnetic field for transport control in the edge plasma of IR-T1 tokamak. The resonance created by the EML causes perturbation of the equilibrium field line in tokamak and as a result, the field lines are chaotic in the vicinity of the dimerized island chains. Transport barriers are formed in the chaotic field line and actually observe in tokamak with reverse magnetic shear. We used area-preserving non-twist (and twist) Poincaré maps to describe the formation of transport barriers, which are actually features of Hamiltonian systems. This transport barrier is useful in reducing radial diffusion of the field line and thus improving the plasma confinement.

  1. Anomalous transport scaling in the DIII-D tokamak matched by supercomputer simulation.

    PubMed

    Candy, J; Waltz, R E

    2003-07-25

    Gyrokinetic simulation of tokamak transport has evolved sufficiently to allow direct comparison of numerical results with experimental data. It is to be emphasized that only with the simultaneous inclusion of many distinct and complex effects can this comparison realistically be made. Until now, numerical studies of tokamak microturbulence have been restricted to either (a) flux tubes or (b) electrostatic fluctuations. Using a newly developed global electromagnetic solver, we have been able to recover via direct simulation the Bohm-like scaling observed in DIII-D L-mode discharges. We also match, well within experimental uncertainty, the measured energy diffusivities.

  2. Energetic electrons, hard x-ray emission and MHD activity studies in the IR-T1 tokamak.

    PubMed

    Agah, K Mikaili; Ghoranneviss, M; Elahi, A Salar

    2015-01-01

    Determinations of plasma parameters as well as the Magnetohydrodynamics (MHD) activity, energetic electrons energy and energy confinement time are essential for future fusion reactors experiments and optimized operation. Also some of the plasma information can be deduced from these parameters, such as plasma equilibrium, stability, and MHD instabilities. In this contribution we investigated the relation between energetic electrons, hard x-ray emission and MHD activity in the IR-T1 Tokamak. For this purpose we used the magnetic diagnostics and a hard x-ray spectroscopy in IR-T1 tokamak. A hard x-ray emission is produced by collision of the runaway electrons with the plasma particles or limiters. The mean energy was calculated from the slope of the energy spectrum of hard x-ray photons.

  3. Deuterium velocity and temperature measurements on the DIII-D tokamak.

    PubMed

    Grierson, B A; Burrell, K H; Solomon, W M; Pablant, N A

    2010-10-01

    Newly installed diagnostic capabilities on the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 46, 6114 (2002)] enable the measurement of main ion (deuterium) velocity and temperature by charge exchange recombination spectroscopy. The uncertainty in atomic physics corrections for determining the velocity is overcome by exploiting the geometrical dependence of the apparent velocity on the viewing angle with respect to the neutral beam.

  4. Helical core reconstruction of a DIII-D hybrid scenario tokamak discharge

    DOE PAGES

    Cianciosa, Mark; Wingen, Andreas; Hirshman, Steven P.; ...

    2017-05-18

    Our paper presents the first fully 3-dimensional (3D) equilibrium reconstruction of a helical core in a tokamak device. Using a new parallel implementation of the Variational Moments Equilibrium Code (PARVMEC) coupled to V3FIT, 3D reconstructions can be performed at resolutions necessary to produce helical states in nominally axisymmetric tokamak equilibria. In a flux pumping experiment performed on DIII-D, an external n=1 field was applied while a 3/2 neoclassical tearing mode was suppressed using ECCD. The externally applied field was rotated past a set of fixed diagnostics at a 20 Hz frequency. Furthermore, the modulation, were found to be strongest in the core SXR and MSE channels, indicates a localized rotating 3D structure locked in phase with the applied field. Signals from multiple time slices are converted to a virtual rotation of modeled diagnostics adding 3D signal information. In starting from an axisymmetric equilibrium reconstruction solution, the reconstructed broader current profile flattens the q-profile, resulting in an m=1, n=1 perturbation of the magnetic axis that ismore » $$\\sim 50\\times $$ larger than the applied n=1 deformation of the edge. Error propagation confirms that the displacement of the axis is much larger than the uncertainty in the axis position validating the helical equilibrium.« less

  5. Helical core reconstruction of a DIII-D hybrid scenario tokamak discharge

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

    Cianciosa, Mark; Wingen, Andreas; Hirshman, Steven P.

    Our paper presents the first fully 3-dimensional (3D) equilibrium reconstruction of a helical core in a tokamak device. Using a new parallel implementation of the Variational Moments Equilibrium Code (PARVMEC) coupled to V3FIT, 3D reconstructions can be performed at resolutions necessary to produce helical states in nominally axisymmetric tokamak equilibria. In a flux pumping experiment performed on DIII-D, an external n=1 field was applied while a 3/2 neoclassical tearing mode was suppressed using ECCD. The externally applied field was rotated past a set of fixed diagnostics at a 20 Hz frequency. Furthermore, the modulation, were found to be strongest in the core SXR and MSE channels, indicates a localized rotating 3D structure locked in phase with the applied field. Signals from multiple time slices are converted to a virtual rotation of modeled diagnostics adding 3D signal information. In starting from an axisymmetric equilibrium reconstruction solution, the reconstructed broader current profile flattens the q-profile, resulting in an m=1, n=1 perturbation of the magnetic axis that ismore » $$\\sim 50\\times $$ larger than the applied n=1 deformation of the edge. Error propagation confirms that the displacement of the axis is much larger than the uncertainty in the axis position validating the helical equilibrium.« less

  6. Comparison of post-contrast 3D-T1-MPRAGE, 3D-T1-SPACE and 3D-T2-FLAIR MR images in evaluation of meningeal abnormalities at 3-T MRI.

    PubMed

    Jeevanandham, Balaji; Kalyanpur, Tejas; Gupta, Prashant; Cherian, Mathew

    2017-06-01

    This study was to assess the usefulness of newer three-dimensional (3D)-T 1 sampling perfection with application optimized contrast using different flip-angle evolutions (SPACE) and 3D-T 2 fluid-attenuated inversion recovery (FLAIR) sequences in evaluation of meningeal abnormalities. 78 patients who presented with high suspicion of meningeal abnormalities were evaluated using post-contrast 3D-T 2 -FLAIR, 3D-T 1 magnetization-prepared rapid gradient-echo (MPRAGE) and 3D-T 1 -SPACE sequences. The images were evaluated independently by two radiologists for cortical gyral, sulcal space, basal cisterns and dural enhancement. The diagnoses were confirmed by further investigations including histopathology. Post-contrast 3D-T 1 -SPACE and 3D-T 2 -FLAIR images yielded significantly more information than MPRAGE images (p < 0.05 for both SPACE and FLAIR images) in detection of meningeal abnormalities. SPACE images best demonstrated abnormalities in dural and sulcal spaces, whereas FLAIR was useful for basal cisterns enhancement. Both SPACE and FLAIR performed equally well in detection of gyral enhancement. In all 10 patients, where both SPACE and T 2 -FLAIR images failed to demonstrate any abnormality, further analysis was also negative. The 3D-T 1 -SPACE sequence best demonstrated abnormalities in dural and sulcal spaces, whereas FLAIR was useful for abnormalities in basal cisterns. Both SPACE and FLAIR performed holds good for detection of gyral enhancement. Post-contrast SPACE and FLAIR sequences are superior to the MPRAGE sequence for evaluation of meningeal abnormalities and when used in combination have the maximum sensitivity for leptomeningeal abnormalities. The negative-predictive value is nearly 100%, where no leptomeningeal abnormality was detected on these sequences. Advances in knowledge: Post-contrast 3D-T 1 -SPACE and 3D-T 2 -FLAIR images are more useful than 3D-T 1 -MPRAGE images in evaluation of meningeal abnormalities.

  7. Effect of ECRH and resonant magnetic fields on formation of magnetic islands in the T-10 tokamak plasma

    NASA Astrophysics Data System (ADS)

    Shestakov, E. A.; Savrukhin, P. V.

    2017-10-01

    Experiments in the T-10 tokamak demonstrated possibility of controlling the plasma current during disruption instability using the electron cyclotron resonance heating (ECRH) and the controlled operation of the ohmic current-holding system. Quasistable plasma discharge with repeating sawtooth oscillations can be restored after energy quench using auxiliary ECRH power when PEC / POH > 2-5. The external magnetic field generation system consisted of eight saddle coils that were arranged symmetrically relative to the equatorial plane of the torus outside of the vacuum vessel of the T-10 tokamak to study the possible resonant magnetic field effects on the rotation frequency of magnetic islands. The saddle coils power supply system is based on four thyristor converters with a total power of 300 kW. The power supply control system is based on Siemens S7 controllers. As shown by preliminary experiments, the interaction efficiency of external magnetic fields with plasma depends on the plasma magnetic configuration. Optimal conditions for slowing the rotation of magnetic islands were determined. Additionally, the direction of the error magnetic field in the T-10 tokamak was determined, and the threshold value of the external magnetic field was determined.

  8. Kinetic simulations of scrape-off layer physics in the DIII-D tokamak

    DOE PAGES

    Churchill, Randy M.; Canik, John M.; Chang, C. S.; ...

    2016-12-27

    Simulations using the fully kinetic code XGCa were undertaken to explore the impact of kinetic effects on scrape-off layer (SOL) physics in DIII-D H-mode plasmas. XGCa is a total- f, gyrokinetic code which self-consistently calculates the axisymmetric electrostatic potential and plasma dynamics, and includes modules for Monte Carlo neutral transport. Fluid simulations are normally used to simulate the SOL, due to its high collisionality. However, depending on plasma conditions, a number of discrepancies have been observed between experiment and leading SOL fluid codes (e.g. SOLPS), including underestimating outer target temperatures, radial electric field in the SOL, parallel ion SOL flowsmore » at the low field side, and impurity radiation. Many of these discrepancies may be linked to the fluid treatment, and might be resolved by including kinetic effects in SOL simulations. The XGCa simulation of the DIII-D tokamak in a nominally sheath-limited regime show many noteworthy features in the SOL. The density and ion temperature are higher at the low-field side, indicative of ion orbit loss. The SOL ion Mach flows are at experimentally relevant levels ( Mi ~0.5), with similar shapes and poloidal variation as observed in various tokamaks. Surprisingly, the ion Mach flows close to the sheath edge remain subsonic, in contrast to the typical fluid Bohm criterion requiring ion flows to be above sonic at the sheath edge. Related to this are the presence of elevated sheath potentials, eΔΦ/T e ~ 3–4, over most of the SOL, with regions in the near-SOL close to the separatrix having eΔΦ/Te > 4. Finally, these two results at the sheath edge are a consequence of non-Maxwellian features in the ions and electrons there.« less

  9. Magnetic evaluation of hydrogen pressures changes on MHD fluctuations in IR-T1 tokamak plasma

    NASA Astrophysics Data System (ADS)

    Alipour, Ramin; Ghanbari, Mohamad R.

    2018-04-01

    Identification of tokamak plasma parameters and investigation on the effects of each parameter on the plasma characteristics is important for the better understanding of magnetohydrodynamic (MHD) activities in the tokamak plasma. The effect of different hydrogen pressures of 1.9, 2.5 and 2.9 Torr on MHD fluctuations of the IR-T1 tokamak plasma was investigated by using of 12 Mirnov coils, singular value decomposition and wavelet analysis. The parameters such as plasma current, loop voltage, power spectrum density, energy percent of poloidal modes, dominant spatial structures and temporal structures of poloidal modes at different plasma pressures are plotted. The results indicate that the MHD activities at the pressure of 2.5 Torr are less than them at other pressures. It also has been shown that in the stable area of plasma and at the pressure of 2.5 Torr, the magnetic force and the force of plasma pressure are in balance with each other and the MHD activities are at their lowest level.

  10. A frequency tunable, eight-channel correlation ECE system for electron temperature turbulence measurements on the DIII-D tokamak

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

    Sung, C., E-mail: csung@physics.ucla.edu; Peebles, W. A.; Wannberg, C.

    2016-11-15

    A new eight-channel correlation electron cyclotron emission diagnostic has recently been installed on the DIII-D tokamak to study both turbulent and coherent electron temperature fluctuations under various plasma conditions and locations. This unique system is designed to cover a broad range of operation space on DIII-D (1.6-2.1 T, detection frequency: 72-108 GHz) via four remotely selected local oscillators (80, 88, 96, and 104 GHz). Eight radial locations are measured simultaneously in a single discharge covering as much as half the minor radius. In this paper, we present design details of the quasi-optical system, the receiver, as well as representative datamore » illustrating operation of the system.« less

  11. Sawtooth mitigation in 3D MHD tokamak modelling with applied magnetic perturbations

    NASA Astrophysics Data System (ADS)

    Bonfiglio, D.; Veranda, M.; Cappello, S.; Chacón, L.; Escande, D. F.

    2017-01-01

    The effect of magnetic perturbations (MPs) on the sawtoothing dynamics of the internal kink mode in the tokamak is discussed in the framework of nonlinear 3D MHD modelling. Numerical simulations are performed with the pixie3d code (Chacón 2008 Phys. Plasmas 15 056103) based on a D-shaped configuration in toroidal geometry. MPs are applied as produced by two sets of coils distributed along the toroidal direction, one set located above and the other set below the outboard midplane, like in experimental devices such as DIII-D and ASDEX Upgrade. The capability of n  =  1 MPs to affect quasi-periodic sawteeth is shown to depend on the toroidal phase difference Δ φ between the perturbations produced by the two sets of coils. In particular, sawtooth mitigation is obtained for the Δ φ =π phasing, whereas no significant effect is observed for Δ φ =0 . Numerical findings are explained by the interplay between different poloidal harmonics in the spectrum of applied MPs, and appear to be consistent with experiments performed in the DIII-D device. Sawtooth mitigation and stimulation of self-organized helical states by applied MPs have been previously demonstrated in both circular tokamak and reversed-field pinch (RFP) experiments in the RFX-mod device, and in related 3D MHD modelling.

  12. Dynamic diagnostics of the error fields in tokamaks

    NASA Astrophysics Data System (ADS)

    Pustovitov, V. D.

    2007-07-01

    The error field diagnostics based on magnetic measurements outside the plasma is discussed. The analysed methods rely on measuring the plasma dynamic response to the finite-amplitude external magnetic perturbations, which are the error fields and the pre-programmed probing pulses. Such pulses can be created by the coils designed for static error field correction and for stabilization of the resistive wall modes, the technique developed and applied in several tokamaks, including DIII-D and JET. Here analysis is based on the theory predictions for the resonant field amplification (RFA). To achieve the desired level of the error field correction in tokamaks, the diagnostics must be sensitive to signals of several Gauss. Therefore, part of the measurements should be performed near the plasma stability boundary, where the RFA effect is stronger. While the proximity to the marginal stability is important, the absolute values of plasma parameters are not. This means that the necessary measurements can be done in the diagnostic discharges with parameters below the nominal operating regimes, with the stability boundary intentionally lowered. The estimates for ITER are presented. The discussed diagnostics can be tested in dedicated experiments in existing tokamaks. The diagnostics can be considered as an extension of the 'active MHD spectroscopy' used recently in the DIII-D tokamak and the EXTRAP T2R reversed field pinch.

  13. Modeling of 3D magnetic equilibrium effects on edge turbulence stability during RMP ELM suppression in tokamaks

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

    Wilcox, R. S.; Wingen, Andreas; Cianciosa, Mark R.

    Some recent experimental observations have found turbulent fluctuation structures that are non-axisymmetric in a tokamak with applied 3D fields. Here, two fluid resistive effects are shown to produce changes relevant to turbulent transport in the modeled 3D magnetohydrodynamic (MHD) equilibrium of tokamak pedestals with these 3D fields applied. Ideal MHD models are insufficient to reproduce the relevant effects. By calculating the ideal 3D equilibrium using the VMEC code, the geometric shaping parameters that determine linear turbulence stability, including the normal curvature and local magnetic shear, are shown to be only weakly modified by applied 3D fields in the DIII-D tokamak.more » These ideal MHD effects are therefore not sufficient to explain the observed changes to fluctuations and transport. Using the M3D-C1 code to model the 3D equilibrium, density is shown to be redistributed on flux surfaces in the pedestal when resistive two fluid effects are included, while islands are screened by rotation in this region. Furthermore, the redistribution of density results in density and pressure gradient scale lengths that vary within pedestal flux surfaces between different helically localized flux tubes. This would produce different drive terms for trapped electron mode and kinetic ballooning mode turbulence, the latter of which is expected to be the limiting factor for pedestal pressure gradients in DIII-D.« less

  14. Modeling of 3D magnetic equilibrium effects on edge turbulence stability during RMP ELM suppression in tokamaks

    DOE PAGES

    Wilcox, R. S.; Wingen, Andreas; Cianciosa, Mark R.; ...

    2017-07-28

    Some recent experimental observations have found turbulent fluctuation structures that are non-axisymmetric in a tokamak with applied 3D fields. Here, two fluid resistive effects are shown to produce changes relevant to turbulent transport in the modeled 3D magnetohydrodynamic (MHD) equilibrium of tokamak pedestals with these 3D fields applied. Ideal MHD models are insufficient to reproduce the relevant effects. By calculating the ideal 3D equilibrium using the VMEC code, the geometric shaping parameters that determine linear turbulence stability, including the normal curvature and local magnetic shear, are shown to be only weakly modified by applied 3D fields in the DIII-D tokamak.more » These ideal MHD effects are therefore not sufficient to explain the observed changes to fluctuations and transport. Using the M3D-C1 code to model the 3D equilibrium, density is shown to be redistributed on flux surfaces in the pedestal when resistive two fluid effects are included, while islands are screened by rotation in this region. Furthermore, the redistribution of density results in density and pressure gradient scale lengths that vary within pedestal flux surfaces between different helically localized flux tubes. This would produce different drive terms for trapped electron mode and kinetic ballooning mode turbulence, the latter of which is expected to be the limiting factor for pedestal pressure gradients in DIII-D.« less

  15. Measurement of H/D ratio and ion temperature on a HT-6M Tokamak

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

    Wei, L.; Lin, X.

    1997-01-01

    By combining optical fibers with piezoelectric scanning Fabry{endash}Perot interferometer, the profiles of H{sub {alpha}} and D{sub {alpha}} have been determined simultaneously in a single Tokamak discharge. Consequently, the ratio of hydrogen to deuterium and ion temperature are obtained. Not only is the uncertainty of shot-to-shot avoided, the results of the experiment indicate that this instrumentation has the advantage of rapid wavelength scanning, large dispersion, high resolution, and good adaptability of working in adverse circumstances such as at a Tokamak site. {copyright} {ital 1997 American Institute of Physics.}

  16. Physics evaluation of compact tokamak ignition experiments

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

    Uckan, N.A.; Houlberg, W.A.; Sheffield, J.

    1985-01-01

    At present, several approaches for compact, high-field tokamak ignition experiments are being considered. A comprehensive method for analyzing the potential physics operating regimes and plasma performance characteristics of such ignition experiments with O-D (analytic) and 1-1/2-D (WHIST) transport models is presented. The results from both calculations are in agreement and show that there are regimes in parameter space in which a class of small (R/sub o/ approx. 1-2 m), high-field (B/sub o/ approx. 8-13 T) tokamaks with aB/sub o/S/q/sub */ approx. 25 +- 5 and kappa = b/a approx. 1.6-2.0 appears ignitable for a reasonable range of transport assumptions. Consideringmore » both the density and beta limits, an evaluation of the performance is presented for various forms of chi/sub e/ and chi/sub i/, including degradation at high power and sawtooth activity. The prospects of ohmic ignition are also examined. 16 refs., 13 figs.« less

  17. Compact Torus Injection Experiments on the H.I.T. teststand and the JFT-2M tokamak

    NASA Astrophysics Data System (ADS)

    Fukumoto, Naoyuki; Fujiwara, Makoto; Kuramoto, Keiji; Ageishi, Masaya; Nagata, Masayoshi; Uyama, Tadao; Ogawa, Hiroaki; Kasai, Satoshi; Hasegawa, Kouichi; Shibata, Takatoshi

    1997-11-01

    A spheromak-type compact torus (CT) acceleration and injection experiment has been carried out using the Himeji Institute of Technology Compact Torus Injector (HIT-CTI). We investigate the possibility of refueling, density control, current drive, and edge electric field control of tokamak plasmas by means of CT injection. The HIT-CTI produces a CT with a speed of 200 km/s and a density of 1× 10^21m-3. We have constructed new electrodes and power supplies, and will install the HIT-CTI on the JFT-2M tokamak at JAERI in Autumn 1997. The outer electrode serves as a common ground for both the formation bank (144μF, 20kV) and the acceleration bank (92.4μF, 40kV). If the external toroidal field of the tokamak is applied across the CT acceleration region, the CT kinetic energy might decrease during penetration into the field lines joining the inner and outer electrode. This could result in the CT not being able to reach the core of the tokamak plasma. Determining the optimum position of the inner electrode is one of the near term goals of this research. We will present magnetic probe, He-Ne interferometer and fast framing camera data from experiments at H.I.T., where a CT was accelerated into a transverse field. We will also present initial results from the operation of the HIT-CTI on the JFT-2M tokamak.

  18. Quiescent double barrier regime in the DIII-D tokamak.

    PubMed

    Greenfield, C M; Burrell, K H; DeBoo, J C; Doyle, E J; Stallard, B W; Synakowski, E J; Fenzi, C; Gohil, P; Groebner, R J; Lao, L L; Makowski, M A; McKee, G R; Moyer, R A; Rettig, C L; Rhodes, T L; Pinsker, R I; Staebler, G M; West, W P

    2001-05-14

    A new sustained high-performance regime, combining discrete edge and core transport barriers, has been discovered in the DIII-D tokamak. Edge localized modes (ELMs) are replaced by a steady oscillation that increases edge particle transport, thereby allowing particle control with no ELM-induced pulsed divertor heat load. The core barrier resembles those usually seen with a low (L) mode edge, without the degradation often associated with ELMs. The barriers are separated by a narrow region of high transport associated with a zero crossing in the E x B shearing rate.

  19. LETTER: Study of combined NBI and ICRF enhancement of the D-3He fusion yield with a Fokker-Planck code

    NASA Astrophysics Data System (ADS)

    Azoulay, M.; George, M. A.; Burger, A.; Collins, W. E.; Silberman, E.

    A two-dimensional bounce averaged Fokker-Planck code is used to study the fusion yield and the wave absorption by residual hydrogen ions in higher harmonic ICRF heating of D (120 keV) and 3He (80 keV) beams in the JT-60U tokamak. Both for the fourth harmonic resonance of 3He (ω = 4ωc3He(0), which is accompanied by the third harmonic resonance of hydrogen (ω = 3ωcH) at the low field side, and for the third harmonic resonance of 3He (ω = 4ωcD(0) = 3ωc3He(0)) = 2ωcH(0)), a few per cent of hydrogen ions are found to absorb a large fraction of the ICRF power and to degrade the fusion output power. In the latter case, D beam acceleration due to the fourth harmonic resonance in the 3He(D) regime can enhance the fusion yield more effectively. A discussion is given of the effect of D beam acceleration due to the fifth harmonic resonance (ω = 5ωcD) at the high field side in the case of ω = 4ωc3He(0) and of the optimization of the fusion yield in the case of lower electron density and higher electron temperature

  20. Li experiments at the tokamak T-11 M in field of steady state PFC investigations

    NASA Astrophysics Data System (ADS)

    Mirnov, S. V.; Lazarev, V. B.

    2011-08-01

    The renewable plasma facing components (PFCs) of steady state tokamak-reactor can be created in framework of Lithium emitter-collector concept, which suggests Li-loop development close the Li-PFC and plasma periphery. It should ensure: Li-emission from PFC into the plasma, plasma periphery cooling by non-coronal Li radiation, Li ions collection before their loss on the wall and Li return into emitter. The subjects of the last T-11 M investigations were the Lithium collection by limiters and Lithium removal from the wall during tokamak conditioning. The Lithium behavior was studied with witness samples and mobile graphite probe. It was shown that Li-deposit on the sides of rail Li-limiter (collector) is proportional to the Li-emission from the Li-limiter (emitter). Lithium deposit on the ion-drift side of Li-limiter is up to 2-3 times more than on the electron-side. The efficiency of Li-collection by T-11 M limiters can be 60 ± 20% of total Lithium emission from Li-limiter during plasma discharges.

  1. An enhanced tokamak startup model

    NASA Astrophysics Data System (ADS)

    Goswami, Rajiv; Artaud, Jean-François

    2017-01-01

    The startup of tokamaks has been examined in the past in varying degree of detail. This phase typically involves the burnthrough of impurities and the subsequent rampup of plasma current. A zero-dimensional (0D) model is most widely used where the time evolution of volume averaged quantities determines the detailed balance between the input and loss of particle and power. But, being a 0D setup, these studies do not take into consideration the co-evolution of plasma size and shape, and instead assume an unchanging minor and major radius. However, it is known that the plasma position and its minor radius can change appreciably as the plasma evolves in time to fill in the entire available volume. In this paper, an enhanced model for the tokamak startup is introduced, which for the first time takes into account the evolution of plasma geometry during this brief but highly dynamic period by including realistic one-dimensional (1D) effects within the broad 0D framework. In addition the effect of runaway electrons (REs) has also been incorporated. The paper demonstrates that the inclusion of plasma cross section evolution in conjunction with REs plays an important role in the formation and development of tokamak startup. The model is benchmarked against experimental results from ADITYA tokamak.

  2. Experimental Test in a Tokamak of Fusion with Spin-Polarized D and 3He

    NASA Astrophysics Data System (ADS)

    Honig, Arnold; Sandorfi, Andrew

    2007-06-01

    An experiment to test polarization retention of highly polarized D and 3He fusion fuels prior to their fusion reactions in a tTokamak is in preparation. The fusion reaction rate with 100% vector polarized reactants is expected from simple theory to increase by a factor of 1.5. With presently available polarizations, fusion reaction enhancements of ˜15% are achievable and of significant interest, while several avenues for obtaining higher polarizations are open. The potential for survival of initial fusion fuel polarizations at ˜108 K plasma core temperatures (˜5KeV) throughout the time interval preceding fusion burn was addressed in a seminal paper in 1982. While the positive conclusion from those calculations suggests that reaction enhancements are indeed feasible, this crucial factor has never been tested in a high temperature plasma core because of difficulties in preparation and injection of sufficiently polarized fusion fuels into a high temperature reactorfusion plasma. Our solution to these problems employs a new source of highly polarized D in the form of solid HD which has been developed and used in our laboratories. Solid HD is compatible with fusion physics in view of its simplicity of elemental composition and very long (weeks) relaxation times at 4K temperature, allowing efficient polarization-preserving cold-transfer operations. Containment and polarization of the HD within polymer capsules, similar to those used in inertial confinement fusion (ICF), is an innovation which simplifies the cold-transfer of polarized fuel from the dilution refrigerator polarization-production apparatus to other liquid helium temperature cryostats, for storage, transport and placement into the barrel of a cryogenic pellet gun for firing at high velocity into the reactor. The other polarized fuel partner, 3He, has been prepared as a polarized gas for applications including high-energy polarized targets and magnetic resonance imaging (MRI) scans. It will be introduced

  3. Physics and Control of Locked Modes in the DIII-D Tokamak

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

    Volpe, Francesco

    This Final Technical Report summarizes an investigation, carried out under the auspices of the DOE Early Career Award, of the physics and control of non-rotating magnetic islands (“locked modes”) in tokamak plasmas. Locked modes are one of the main causes of disruptions in present tokamaks, and could be an even bigger concern in ITER, due to its relatively high beta (favoring the formation of Neoclassical Tearing Mode islands) and low rotation (favoring locking). For these reasons, this research had the goal of studying and learning how to control locked modes in the DIII-D National Fusion Facility under ITER-relevant conditions ofmore » high pressure and low rotation. Major results included: the first full suppression of locked modes and avoidance of the associated disruptions; the demonstration of error field detection from the interaction between locked modes, applied rotating fields and intrinsic errors; the analysis of a vast database of disruptive locked modes, which led to criteria for disruption prediction and avoidance.« less

  4. A fission-fusion hybrid reactor in steady-state L-mode tokamak configuration with natural uranium

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

    Reed, Mark; Parker, Ronald R.; Forget, Benoit

    2012-06-19

    This work develops a conceptual design for a fusion-fission hybrid reactor operating in steady-state L-mode tokamak configuration with a subcritical natural or depleted uranium pebble bed blanket. A liquid lithium-lead alloy breeds enough tritium to replenish that consumed by the D-T fusion reaction. The fission blanket augments the fusion power such that the fusion core itself need not have a high power gain, thus allowing for fully non-inductive (steady-state) low confinement mode (L-mode) operation at relatively small physical dimensions. A neutron transport Monte Carlo code models the natural uranium fission blanket. Maximizing the fission power gain while breeding sufficient tritiummore » allows for the selection of an optimal set of blanket parameters, which yields a maximum prudent fission power gain of approximately 7. A 0-D tokamak model suffices to analyze approximate tokamak operating conditions. This fission blanket would allow the fusion component of a hybrid reactor with the same dimensions as ITER to operate in steady-state L-mode very comfortably with a fusion power gain of 6.7 and a thermal fusion power of 2.1 GW. Taking this further can determine the approximate minimum scale for a steady-state L-mode tokamak hybrid reactor, which is a major radius of 5.2 m and an aspect ratio of 2.8. This minimum scale device operates barely within the steady-state L-mode realm with a thermal fusion power of 1.7 GW. Basic thermal hydraulic analysis demonstrates that pressurized helium could cool the pebble bed fission blanket with a flow rate below 10 m/s. The Brayton cycle thermal efficiency is 41%. This reactor, dubbed the Steady-state L-mode non-Enriched Uranium Tokamak Hybrid (SLEUTH), with its very fast neutron spectrum, could be superior to pure fission reactors in terms of breeding fissile fuel and transmuting deleterious fission products. It would likely function best as a prolific plutonium breeder, and the plutonium it produces could actually be more

  5. A fission-fusion hybrid reactor in steady-state L-mode tokamak configuration with natural uranium

    NASA Astrophysics Data System (ADS)

    Reed, Mark; Parker, Ronald R.; Forget, Benoit

    2012-06-01

    This work develops a conceptual design for a fusion-fission hybrid reactor operating in steady-state L-mode tokamak configuration with a subcritical natural or depleted uranium pebble bed blanket. A liquid lithium-lead alloy breeds enough tritium to replenish that consumed by the D-T fusion reaction. The fission blanket augments the fusion power such that the fusion core itself need not have a high power gain, thus allowing for fully non-inductive (steady-state) low confinement mode (L-mode) operation at relatively small physical dimensions. A neutron transport Monte Carlo code models the natural uranium fission blanket. Maximizing the fission power gain while breeding sufficient tritium allows for the selection of an optimal set of blanket parameters, which yields a maximum prudent fission power gain of approximately 7. A 0-D tokamak model suffices to analyze approximate tokamak operating conditions. This fission blanket would allow the fusion component of a hybrid reactor with the same dimensions as ITER to operate in steady-state L-mode very comfortably with a fusion power gain of 6.7 and a thermal fusion power of 2.1 GW. Taking this further can determine the approximate minimum scale for a steady-state L-mode tokamak hybrid reactor, which is a major radius of 5.2 m and an aspect ratio of 2.8. This minimum scale device operates barely within the steady-state L-mode realm with a thermal fusion power of 1.7 GW. Basic thermal hydraulic analysis demonstrates that pressurized helium could cool the pebble bed fission blanket with a flow rate below 10 m/s. The Brayton cycle thermal efficiency is 41%. This reactor, dubbed the Steady-state L-mode non-Enriched Uranium Tokamak Hybrid (SLEUTH), with its very fast neutron spectrum, could be superior to pure fission reactors in terms of breeding fissile fuel and transmuting deleterious fission products. It would likely function best as a prolific plutonium breeder, and the plutonium it produces could actually be more

  6. Development of frequency modulation reflectometer for Korea Superconducting Tokamak Advanced Research tokamak

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

    Seo, Seong-Heon; Wi, H. M.; Lee, W. R.

    2013-08-15

    Frequency modulation reflectometer has been developed to measure the plasma density profile of the Korea Superconducting Tokamak Advanced Research tokamak. Three reflectometers are operating in extraordinary polarization mode in the frequency range of Q band (33.6–54 GHz), V band (48–72 GHz), and W band (72–108 GHz) to measure the density up to 7 × 10{sup 19} m{sup −3} when the toroidal magnetic field is 2 T on axis. The antenna is installed inside of the vacuum vessel. A new vacuum window is developed by using 50 μm thick mica film and 0.1 mm thick gold gasket. The filter bank ofmore » low pass filter, notch filter, and Faraday isolator is used to reject the electron cyclotron heating high power at attenuation of 60 dB. The full frequency band is swept in 20 μs. The mixer output is directly digitized with sampling rate of 100 MSamples/s. The phase is obtained by using wavelet transform. The whole hardware and software system is described in detail and the measured density profile is presented as a result.« less

  7. The Multiple Gyrotron System on the DIII-D Tokamak

    DOE PAGES

    Lohr, J.; Anderson, J.; Brambila, R.; ...

    2015-08-28

    A major component of the versatile heating systems on the DIII-D tokamak is the gyrotron complex. This system routinely operates at 110 GHz with 4.7 MW generated rf power for electron cyclotron heating and current drive. The complex is being upgraded with the addition of new depressed collector potential gyrotrons operating at 117.5 GHz and generating rf power in excess of 1.0 MW each. The long term upgrade plan calls for 10 gyrotrons at the higher frequency being phased in as resources permit, for an injected power near 10 MW. This article presents a summary of the current status ofmore » the DIII-D gyrotron complex, its performance, individual components, testing procedures, operational parameters, plans, and a brief summary of the experiments for which the system is currently being used.« less

  8. Public Data Set: Non-inductively Driven Tokamak Plasmas at Near-Unity βt in the Pegasus Toroidal Experiment

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

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

    This public data set contains openly-documented, machine readable digital research data corresponding to figures published in J.A. Reusch et al., 'Non-inductively Driven Tokamak Plasmas at Near-Unity βt in the Pegasus Toroidal Experiment,' Phys. Plasmas 25, 056101 (2018).

  9. Relationship Between Locked Modes and Disruptions in the DIII-D Tokamak

    NASA Astrophysics Data System (ADS)

    Sweeney, Ryan

    This thesis is organized into three body chapters: (1) the first use of naturally rotating tearing modes to diagnose intrinsic error fields is presented with experimental results from the EXTRAP T2R reversed field pinch, (2) a large scale study of locked modes (LMs) with rotating precursors in the DIII-D tokamak is reported, and (3) an in depth study of LM induced thermal collapses on a few DIII-D discharges is presented. The amplitude of naturally rotating tearing modes (TMs) in EXTRAP T2R is modulated in the presence of a resonant field (given by the superposition of the resonant intrinsic error field, and, possibly, an applied, resonant magnetic perturbation (RMP)). By scanning the amplitude and phase of the RMP and observing the phase-dependent amplitude modulation of the resonant, naturally rotating TM, the corresponding resonant error field is diagnosed. A rotating TM can decelerate and lock in the laboratory frame, under the effect of an electromagnetic torque due to eddy currents induced in the wall. These locked modes often lead to a disruption, where energy and particles are lost from the equilibrium configuration on a timescale of a few to tens of milliseconds in the DIII-D tokamak. In fusion reactors, disruptions pose a problem for the longevity of the reactor. Thus, learning to predict and avoid them is important. A database was developed consisting of ˜ 2000 DIII-D discharges exhibiting TMs that lock. The database was used to study the evolution, the nonlinear effects on equilibria, and the disruptivity of locked and quasi-stationary modes with poloidal and toroidal mode numbers m = 2 and n = 1 at DIII-D. The analysis of 22,500 discharges shows that more than 18% of disruptions present signs of locked or quasi-stationary modes with rotating precursors. A parameter formulated by the plasma internal inductance li divided by the safety factor at 95% of the toroidal flux, q95, is found to exhibit predictive capability over whether a locked mode will

  10. Introduction to D-He(3) fusion reactors

    NASA Technical Reports Server (NTRS)

    Vlases, G. C.; Steinhauer, L. C.

    1989-01-01

    A review and evaluation of D-He(3) fusion reactor technology is presented. The advantages and disadvantages of the D-He(3) and D-T reactor cycles are outlined and compared. In addition, the general design features of D-He(3) tokamaks and field reversed configuration (FRC) reactors are described and the relative merits of each are compared. It is concluded that both tokamaks and FRC's offer certain advantages, and that the ultimate decision as to which to persue for terrestrial power generation will depend heavily on how the physics performance of each of them develops over the next few years. It is clear that the D-He(3) fuel cycle offers marked advantages over the D-T cycle. Although the physics requirements for D-He(3) are more demanding, the overwhelming advantages resulting from the two order of magnitude reduction of neutron flux are expected to lead to a shorter time to commercialization than for the D-T cycle.

  11. Introduction to D-He(3) fusion reactors

    NASA Astrophysics Data System (ADS)

    Vlases, G. C.; Steinhauer, L. C.

    1989-07-01

    A review and evaluation of D-He(3) fusion reactor technology is presented. The advantages and disadvantages of the D-He(3) and D-T reactor cycles are outlined and compared. In addition, the general design features of D-He(3) tokamaks and field reversed configuration (FRC) reactors are described and the relative merits of each are compared. It is concluded that both tokamaks and FRC's offer certain advantages, and that the ultimate decision as to which to persue for terrestrial power generation will depend heavily on how the physics performance of each of them develops over the next few years. It is clear that the D-He(3) fuel cycle offers marked advantages over the D-T cycle. Although the physics requirements for D-He(3) are more demanding, the overwhelming advantages resulting from the two order of magnitude reduction of neutron flux are expected to lead to a shorter time to commercialization than for the D-T cycle.

  12. First neutral beam injection experiments on KSTAR tokamak.

    PubMed

    Jeong, S H; Chang, D H; Kim, T S; In, S R; Lee, K W; Jin, J T; Chang, D S; Oh, B H; Bae, Y S; Kim, J S; Park, H T; Watanabe, K; Inoue, T; Kashiwagi, M; Dairaku, M; Tobari, H; Hanada, M

    2012-02-01

    The first neutral beam (NB) injection system of the Korea Superconducting Tokamak Advanced Research (KSTAR) tokamak was partially completed in 2010 with only 1∕3 of its full design capability, and NB heating experiments were carried out during the 2010 KSTAR operation campaign. The ion source is composed of a JAEA bucket plasma generator and a KAERI large multi-aperture accelerator assembly, which is designed to deliver a 1.5 MW, NB power of deuterium at 95 keV. Before the beam injection experiments, discharge, and beam extraction characteristics of the ion source were investigated. The ion source has good beam optics in a broad range of beam perveance. The optimum perveance is 1.1-1.3 μP, and the minimum beam divergence angle measured by the Doppler shift spectroscopy is 0.8°. The ion species ratio is D(+):D(2)(+):D(3)(+) = 75:20:5 at beam current density of 85 mA/cm(2). The arc efficiency is more than 1.0 A∕kW. In the 2010 KSTAR campaign, a deuterium NB power of 0.7-1.5 MW was successfully injected into the KSTAR plasma with a beam energy of 70-90 keV. L-H transitions were observed within a wide range of beam powers relative to a threshold value. The edge pedestal formation in the T(i) and T(e) profiles was verified through CES and electron cyclotron emission diagnostics. In every deuterium NB injection, a burst of D-D neutrons was recorded, and increases in the ion temperature and plasma stored energy were found.

  13. 2D electron density profile measurement in tokamak by laser-accelerated ion-beam probe.

    PubMed

    Chen, Y H; Yang, X Y; Lin, C; Wang, L; Xu, M; Wang, X G; Xiao, C J

    2014-11-01

    A new concept of Heavy Ion Beam Probe (HIBP) diagnostic has been proposed, of which the key is to replace the electrostatic accelerator of traditional HIBP by a laser-driven ion accelerator. Due to the large energy spread of ions, the laser-accelerated HIBP can measure the two-dimensional (2D) electron density profile of tokamak plasma. In a preliminary simulation, a 2D density profile was reconstructed with a spatial resolution of about 2 cm, and with the error below 15% in the core region. Diagnostics of 2D density fluctuation is also discussed.

  14. The Spherical Tokamak MEDUSA for Costa Rica

    NASA Astrophysics Data System (ADS)

    Ribeiro, Celso; Vargas, Ivan; Guadamuz, Saul; Mora, Jaime; Ansejo, Jose; Zamora, Esteban; Herrera, Julio; Chaves, Esteban; Romero, Carlos

    2012-10-01

    The former spherical tokamak (ST) MEDUSA (Madison EDUcation Small Aspect.ratio tokamak, R<0.14m, a<0.10m, BT<0.5T, Ip<40kA, 3ms pulse)[1] is in a process of donation to Costa Rica Institute of Technology. The main objective of MEDUSA is to train students in plasma physics /technical related issues which will help all tasks of the very low aspect ratio stellarator SCR-1(A≡R/>=3.6, under design[2]) and also the ongoing activities in low temperature plasmas. Courses in plasma physics at undergraduate and post-graduate joint programme levels are regularly conducted. The scientific programme is intend to clarify several issues in relevant physics for conventional and mainly STs, including transport, heating and current drive via Alfv'en wave, and natural divertor STs with ergodic magnetic limiter[3,4]. [1] G.D.Garstka, PhD thesis, University of Wisconsin at Madison, 1997 [2] L.Barillas et al., Proc. 19^th Int. Conf. Nucl. Eng., Japan, 2011 [3] C.Ribeiro et al., IEEJ Trans. Electrical and Electronic Eng., 2012(accepted) [4] C.Ribeiro et al., Proc. 39^th EPS Conf. Contr. Fusion and Plasma Phys., Sweden, 2012

  15. Helium Catalyzed D-D Fusion in a Levitated Dipole

    NASA Astrophysics Data System (ADS)

    Kesner, J.; Bromberg, L.; Garnier, D. T.; Hansen, A.; Mauel, M. E.

    2003-10-01

    Fusion research has focused on the goal of deuterium and tritium (D-T) fusion power because the reaction rate is large compared with the other fusion fuels: D-D or D-He3. Furthermore, the D-D cycle is difficult in traditional confinement devices, such as tokamaks, because good energy confinement is accompanied by good particle confinement which leads to an accumulation of ash. Fusion reactors based on the D-D reaction would be advantageous to D-T based reactors since they do not require the breeding of tritium and can reduce the flux of energetic neutrons that cause material damage. We propose a fusion power source based on the levitated dipole fusion concept that uses a "helium catalyzed D-D" fuel cycle, where rapid circulation of plasma allows the removal of tritium and the re-injection of the He3 decay product, eliminating the need for a massive blanket and shield. Stable dipole confinement derives from plasma compressibility instead of the magnetic shear and average good curvature. As a result, a dipole magnetic field can stabilize plasma at high beta while allowing large-scale adiabatic particle circulation. These properties may make the levitated dipole uniquely capable of achieving good energy confinement with low particle confinement. We find that a dipole based D-D power source can provide better utilization of magnetic field energy with a comparable mass power density to a D-T based tokamak power source.

  16. Some Aspects of Advanced Tokamak Modeling in DIII-D

    NASA Astrophysics Data System (ADS)

    St John, H. E.; Petty, C. C.; Murakami, M.; Kinsey, J. E.

    2000-10-01

    We extend previous work(M. Murakami, et al., General Atomics Report GA-A23310 (1999).) done on time dependent DIII-D advanced tokamak simulations by introducing theoretical confinement models rather than relying on power balance derived transport coefficients. We explore using NBCD and off axis ECCD together with a self-consistent aligned bootstrap current, driven by the internal transport barrier dynamics generated with the GLF23 confinement model, to shape the hollow current profile and to maintain MHD stable conditions. Our theoretical modeling approach uses measured DIII-D initial conditions to start off the simulations in a smooth consistent manner. This mitigates the troublesome long lived perturbations in the ohmic current profile that is normally caused by inconsistent initial data. To achieve this goal our simulation uses a sequence of time dependent eqdsks generated autonomously by the EFIT MHD equilibrium code in analyzing experimental data to supply the history for the simulation.

  17. Advanced Divertor Design and Application under Modern Superconducting Tokamak Constraints

    NASA Astrophysics Data System (ADS)

    Covele, Brent; Kotschenreuther, Mike; Mahajan, Swadesh; Valanju, Prashant

    2013-10-01

    With current ITER projections already predicting divertor exhaust heat loads in the 5-10 MW/m2 range, i.e. at the maximum tolerance, it is clear that the divertor heat load problem will only be exacerbated for future superconducting tokamaks, as well as perhaps some modern tokamaks today. Thus, an advanced divertor, such as the X-Divertor (XD), Super-X Divertor (SXD), or Snowflake (SF) will become a virtual necessity to reduce incident heat flux at the target plates. Using the 2D magnetic equilibrium code CORSICA, we explore the possibilities of creating an advanced divertor for a next-generation superconducting tokamak (Ip = 15 MA, BT = 5.3 T, R = 6.2 m) under nominal engineering constraints. Advanced divertors were achieved with no in-vessel PF coils, PF current densities below 30 MA/m2, and vertical maintenance access, all of which are favorable conditions for tokamaks today. Both the XD and SF divertors are readily achievable while maintaining core plasma performance, and the advantages and disadvantages of each are discussed in turn. Some thought is given as to how the divertor cassette will need to be modified to accommodate advanced divertors. Work supported under US-DOE projects DE-FG02-04ER54742 and DE-FG02-04ER54754.

  18. Modeling non-stationary, non-axisymmetric heat patterns in DIII-D tokamak

    DOE PAGES

    Ciro, D.; Evans, T. E.; Caldas, I. L.

    2016-10-27

    Non-axisymmetric stationary magnetic perturbations lead to the formation of homoclinic tangles near the divertor magnetic saddle in tokamak discharges. These tangles intersect the divertor plates in static helical structures that delimit the regions reached by open magnetic field lines reaching the plasma column and leading the charged particles to the strike surfaces by parallel transport. In this article we introduce a non-axisymmetric rotating magnetic perturbation to model the time evolution of the three-dimensional magnetic field of a singlenull DIII-D tokamak discharge developing a rotating tearing mode. The non-axiymmetric field is modeled using the magnetic signals to adjust the phases andmore » currents of a set of internal filamentary currents that approximate the magnetic field in the plasma edge region. The stable and unstable manifolds of the asymmetric magnetic saddle are obtained through an adaptive calculation providing the cuts at a given poloidal plane and the strike surfaces. Lastly, for the modeled shot, the experimental heat pattern and its time development are well described by the rotating unstable manifold, indicating the emergence of homoclinic lobes in a rotating frame due to the plasma instabilities.« less

  19. Modeling non-stationary, non-axisymmetric heat patterns in DIII-D tokamak

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

    Ciro, D.; Evans, T. E.; Caldas, I. L.

    Non-axisymmetric stationary magnetic perturbations lead to the formation of homoclinic tangles near the divertor magnetic saddle in tokamak discharges. These tangles intersect the divertor plates in static helical structures that delimit the regions reached by open magnetic field lines reaching the plasma column and leading the charged particles to the strike surfaces by parallel transport. In this article we introduce a non-axisymmetric rotating magnetic perturbation to model the time evolution of the three-dimensional magnetic field of a singlenull DIII-D tokamak discharge developing a rotating tearing mode. The non-axiymmetric field is modeled using the magnetic signals to adjust the phases andmore » currents of a set of internal filamentary currents that approximate the magnetic field in the plasma edge region. The stable and unstable manifolds of the asymmetric magnetic saddle are obtained through an adaptive calculation providing the cuts at a given poloidal plane and the strike surfaces. Lastly, for the modeled shot, the experimental heat pattern and its time development are well described by the rotating unstable manifold, indicating the emergence of homoclinic lobes in a rotating frame due to the plasma instabilities.« less

  20. Deuterium-tritium experiments on the Tokamak Fusion Test reactor

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

    Hosea, J.; Adler, J.H.; Alling, P.

    The deuterium-tritium (D-T) experimental program on the Tokamak Fusion Test Reactor (TFTR) is underway and routine tritium operations have been established. The technology upgrades made to the TFTR facility have been demonstrated to be sufficient for supporting both operations and maintenance for an extended D-T campaign. To date fusion power has been increased to {approx}9 MW and several physics results of importance to the D-T reactor regime have been obtained: electron temperature, ion temperature, and plasma stored energy all increase substantially in the D-T regime relative to the D-D regime at the same neutral beam power and comparable limiter conditioning;more » possible alpha electron heating is indicated and energy confinement improvement with average ion mass is observed; and alpha particle losses appear to be classical with no evidence of TAE mode activity up to the PFUS {approx}6 MW level. Instability in the TAE mode frequency range has been observed at PFUS > 7 MW and its effect on performance in under investigation. Preparations are underway to enhance the alpha particle density further by increasing fusion power and by extending the neutral beam pulse length to permit alpha particle effects of relevance to the ITER regime to be more fully explored.« less

  1. Heat pulse propagation studies on DIII-D and the Tokamak Fusion Test Reactor

    NASA Astrophysics Data System (ADS)

    Fredrickson, E. D.; Austin, M. E.; Groebner, R.; Manickam, J.; Rice, B.; Schmidt, G.; Snider, R.

    2000-12-01

    Sawtooth phenomena have been studied on DIII-D and the Tokamak Fusion Test Reactor (TFTR) [D. Meade and the TFTR Group, in Proceedings of the International Conference on Plasma Physics and Controlled Nuclear Fusion, Washington, DC, 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. 1, pp. 9-24]. In the experiments the sawtooth characteristics were studied with fast electron temperature (ECE) and soft x-ray diagnostics. For the first time, measurements of a strong ballistic electron heat pulse were made in a shaped tokamak (DIII-D) [J. Luxon and DIII-D Group, in Proceedings of the 11th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Kyoto (International Atomic Energy Agency, Vienna, 1987), Vol. 1, p. 159] and the "ballistic effect" was stronger than was previously reported on TFTR. Evidence is presented in this paper that the ballistic effect is related to the fast growth phase of the sawtooth precursor. Fast, 2 ms interval, measurements on DIII-D were made of the ion temperature evolution following sawteeth and partial sawteeth to document the ion heat pulse characteristics. It is found that the ion heat pulse does not exhibit the very fast, "ballistic" behavior seen for the electrons. Further, for the first time it is shown that the electron heat pulses from partial sawtooth crashes (on DIII-D and TFTR) are seen to propagate at speeds close to those expected from the power balance calculations of the thermal diffusivities whereas heat pulses from fishbones propagate at rates more consistent with sawtooth induced heat pulses. These results suggest that the fast propagation of sawtooth-induced heat pulses is not a feature of nonlinear transport models, but that magnetohydrodynamic events can have a strong effect on electron thermal transport.

  2. CAMAC throughput of a new RISC-based data acquisition computer at the DIII-D tokamak

    NASA Astrophysics Data System (ADS)

    Vanderlaan, J. F.; Cummings, J. W.

    1993-10-01

    The amount of experimental data acquired per plasma discharge at DIII-D has continued to grow. The largest shot size in May 1991 was 49 Mbyte; in May 1992, 66 Mbyte; and in April 1993, 80 Mbyte. The increasing load has prompted the installation of a new Motorola 88100-based MODCOMP computer to supplement the existing core of three older MODCOMP data acquisition CPU's. New Kinetic Systems CAMAC serial highway driver hardware runs on the 88100 VME bus. The new operating system is MODCOMP REAL/IX version of AT&T System V UNIX with real-time extensions and networking capabilities; future plans call for installation of additional computers of this type for tokamak and neutral beam control functions. Experiences with the CAMAC hardware and software will be chronicled, including observation of data throughput. The Enhanced Serial Highway crate controller is advertised as twice as fast as the previous crate controller, and computer I/O speeds are expected to also increase data rates.

  3. First wall design of aluminum alloy R-tokamak

    NASA Astrophysics Data System (ADS)

    Hamada, Y.; Matsuoka, K.; Ogawa, Y.; Kitagawa, S.; Toi, K.; Yamazaki, K.; Abe, Y.; Amano, T.; Fujita, J.; Kaneko, O.; Kawahata, K.; Kuroda, T.; Matsuura, K.; Midzuno, Y.; Naitou, H.; Noda, N.; Ohkubo, K.; Oka, Y.; Sakurai, K.; Tanahashi, S.; Watari, T.

    1984-05-01

    A design study of a low-activation D-T tokamak Reacting Plasma Project In Nagoya has been finished. The study emphasizes the vacuum vessel and the bumper limiter. Our choice of materials (aluminum vacuum vessel, copper conductors, aluminum TF coil case and lead shield) results in a radiation level of about 1 × 10 -3 times that of a TFTR type design, and 1 × 10 -4 times that of JET type design, at 2 weeks after one D-T shot. Thick graphite tiles will be fixed directly on the aluminum vacuum vessel using aluminum spring washers and bolts. With this simplified structure of the bumper limiter, the inner surface temperature of the thick aluminum vacuum vessel will be less than 120°C which is required to reduce the overaging effect of the aluminum alloy.

  4. An area-preserving mapping in natural canonical coordinates for magnetic field line trajectories in the DIII-D tokamak

    NASA Astrophysics Data System (ADS)

    Punjabi, Alkesh

    2009-11-01

    The new approach of integrating magnetic field line trajectories in natural canonical coordinates (Punjabi and Ali 2008 Phys. Plasmas 15 122502) in divertor tokamaks is used for the DIII-D tokamak (Luxon and Davis1985 Fusion Technol. 8 441). The equilibrium EFIT data (Evans et al 2004 Phys. Rev. Lett. 92 235003, Lao et al 2005 Fusion Sci. Technol. 48 968) for the DIII-D tokamak shot 115467 at 3000 ms is used to construct the equilibrium generating function (EGF) for the DIII-D in natural canonical coordinates. The EGF gives quite an accurate representation of the closed and open equilibrium magnetic surfaces near the separatrix, the separatrix, the position of the X-point and the poloidal magnetic flux inside the ideal separatrix in the DIII-D. The equilibrium safety factor q from the EGF is somewhat smaller than the DIII-D EFIT q profile. The equilibrium safety factor is calculated from EGF as described in the previous paper (Punjabi and Ali 2008 Phys. Plasmas 15 122502). Here the safety factor for the open surfaces in the DIII-D is calculated. A canonical transformation is used to construct a symplectic mapping for magnetic field line trajectories in the DIII-D in natural canonical coordinates. The map is explored in more detail in this work, and is used to calculate field line trajectories in the DIII-D tokamak. The continuous analogue of the map does not distort the DIII-D magnetic surfaces in different toroidal planes between successive iterations of the map. The map parameter k can represent effects of magnetic asymmetries in the DIII-D. These effects in the DIII-D are illustrated. The DIII-D map is then used to calculate stochastic broadening of the ideal separatrix from the topological noise and field errors, the low mn, the high mn and peeling-ballooning magnetic perturbations in the DIII-D. The width of the stochastic layer scales as 1/2 power of amplitude with a maximum deviation of 6% from the Boozer-Rechester scaling (Boozer and Rechester 1978 Phys

  5. Remote network control plasma diagnostic system for Tokamak T-10

    NASA Astrophysics Data System (ADS)

    Troynov, V. I.; Zimin, A. M.; Krupin, V. A.; Notkin, G. E.; Nurgaliev, M. R.

    2016-09-01

    The parameters of molecular plasma in closed magnetic trap is studied in this paper. Using the system of molecular diagnostics, which was designed by the authors on the «Tokamak T-10» facility, the radiation of hydrogen isotopes at the plasma edge is investigated. The scheme of optical radiation registration within visible spectrum is described. For visualization, identification and processing of registered molecular spectra a new software is developed using MatLab environment. The software also includes electronic atlas of electronic-vibrational-rotational transitions for molecules of protium and deuterium. To register radiation from limiter cross-section a network control system is designed using the means of the Internet/Intranet. Remote control system diagram and methods are given. The examples of web-interfaces for working out equipment control scenarios and viewing of results are provided. After test run in Intranet, the remote diagnostic system will be accessible through Internet.

  6. Measurements of branching fraction ratios and CP-asymmetries in suppressed B{sup -}{yields}D({yields}K{sup +}{pi}{sup -})K{sup -} and B{sup -}{yields}D({yields}K{sup +}{pi}{sup -}){pi}{sup -} decays

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

    Aaltonen, T.; Brucken, E.; Devoto, F.

    2011-11-01

    We report the first reconstruction in hadron collisions of the suppressed decays B{sup -}{yields}D({yields}K{sup +}{pi}{sup -})K{sup -} and B{sup -}{yields}D({yields}K{sup +}{pi}{sup -}){pi}{sup -}, sensitive to the Cabibbo-Kobayashi-Maskawa phase {gamma}, using data from 7 fb{sup -1} of integrated luminosity collected by the CDF II detector at the Tevatron collider. We reconstruct a signal for the B{sup -}{yields}D({yields}K{sup +}{pi}{sup -})K{sup -} suppressed mode with a significance of 3.2 standard deviations, and measure the ratios of the suppressed to favored branching fractions R(K)=[22.0{+-}8.6(stat){+-}2.6(syst)]x10{sup -3}, R{sup +}(K)=[42.6{+-}13.7(stat){+-}2.8(syst)]x10{sup -3}, R{sup -}(K)=[3.8{+-}10.3(stat){+-}2.7(syst)]x10{sup -3} as well as the direct CP-violating asymmetry A(K)=-0.82{+-}0.44(stat){+-}0.09(syst) of this mode. Corresponding quantitiesmore » for B{sup -}{yields}D({yields}K{sup +}{pi}{sup -}){pi}{sup -} decay are also reported.« less

  7. Shutdown Dose Rate Analysis for the long-pulse D-D Operation Phase in KSTAR

    NASA Astrophysics Data System (ADS)

    Park, Jin Hun; Han, Jung-Hoon; Kim, D. H.; Joo, K. S.; Hwang, Y. S.

    2017-09-01

    KSTAR is a medium size fully superconducting tokamak. The deuterium-deuterium (D-D) reaction in the KSTAR tokamak generates neutrons with a peak yield of 3.5x1016 per second through a pulse operation of 100 seconds. The effect of neutron generation from full D-D high power KSTAR operation mode to the machine, such as activation, shutdown dose rate, and nuclear heating, are estimated for an assurance of safety during operation, maintenance, and machine upgrade. The nuclear heating of the in-vessel components, and neutron activation of the surrounding materials have been investigated. The dose rates during operation and after shutdown of KSTAR have been calculated by a 3D CAD model of KSTAR with the Monte Carlo code MCNP5 (neutron flux and decay photon), the inventory code FISPACT (activation and decay photon) and the FENDL 2.1 nuclear data library.

  8. Open Charm Yields in d+Au Collisions at sqrt(sNN) = 200 GeV

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

    Adams, J.; Aggarwal, M.M.; Ahammed, Z.

    2005-01-07

    Mid-rapidity open charm spectra from direct reconstruction of D{sup 0}({bar D}{sup 0}) {yields} K{sup {-+}} {pi}{sup {+-}} in d+Au collisions and indirect electron/positron measurements via charm semileptonic decays in p+p and d+Au collisions at {radical}s{sub NN} = 200 GeV are reported. The D{sup 0}({bar D}{sup 0}) spectrum covers a transverse momentum (p{sub T}) range of 0.1 < p{sub T} < 3 GeV/c whereas the electron spectra cover a range of 1 < p{sub T} < 4 GeV/c. The electron spectra show approximate binary collision scaling between p+p and d+Au collisions. From these two independent analyses, the differential cross section permore » nucleon-nucleon binary interaction at mid-rapidity for open charm production from d+Au collisions at RHIC is d{sigma}{sub c{bar c}}{sup NN}/dy = 0.30 {+-} 0.04 (stat.) {+-} 0.09(syst.) mb. The results are compared to theoretical calculations. Implications for charmonium results in A+A collisions are discussed.« less

  9. The strongest magnetic barrier in the DIII-D tokamak and comparison with the ASDEX UG

    NASA Astrophysics Data System (ADS)

    Ali, Halima; Punjabi, Alkesh

    2013-05-01

    Magnetic perturbations in tokamaks lead to the formation of magnetic islands, chaotic field lines, and the destruction of flux surfaces. Controlling or reducing transport along chaotic field lines is a key challenge in magnetically confined fusion plasmas. A local control method was proposed by Chandre et al. [Nucl. Fusion 46, 33-45 (2006)] to build barriers to magnetic field line diffusion by addition of a small second-order control term localized in the phase space to the field line Hamiltonian. Formation and existence of such magnetic barriers in Ohmically heated tokamaks (OHT), ASDEX UG and piecewise analytic DIII-D [Luxon, J.L.; Davis, L.E., Fusion Technol. 8, 441 (1985)] plasma equilibria was predicted by the authors [Ali, H.; Punjabi, A., Plasma Phys. Control. Fusion 49, 1565-1582 (2007)]. Very recently, this prediction for the DIII-D has been corroborated [Volpe, F.A., et al., Nucl. Fusion 52, 054017 (2012)] by field-line tracing calculations, using experimentally constrained Equilibrium Fit (EFIT) [Lao, et al., Nucl. Fusion 25, 1611 (1985)] DIII-D equilibria perturbed to include the vacuum field from the internal coils utilized in the experiments. This second-order approach is applied to the DIII-D tokamak to build noble irrational magnetic barriers inside the chaos created by the locked resonant magnetic perturbations (RMPs) (m, n)=(3, 1)+(4, 1), with m and n the poloidal and toroidal mode numbers of the Fourier expansion of the magnetic perturbation with amplitude δ. A piecewise, analytic, accurate, axisymmetric generating function for the trajectories of magnetic field lines in the DIII-D is constructed in magnetic coordinates from the experimental EFIT Grad-Shafranov solver [Lao, L, et al., Fusion Sci. Technol. 48, 968 (2005)] for the shot 115,467 at 3000 ms in the DIII-D. A symplectic mathematical map is used to integrate field lines in the DIII-D. A numerical algorithm [Ali, H., et al., Radiat. Eff. Def. Solids Inc. Plasma Sc. Plasma Tech. 165, 83

  10. Influence of drug binding on DNA hydration: acoustic and densimetric characterizations of netropsin binding to the poly(dAdT).poly(dAdT) and poly(dA).poly(dT) duplexes and the poly(dT).poly(dA).poly(dT) triplex at 25 degrees C.

    PubMed

    Chalikian, T V; Plum, G E; Sarvazyan, A P; Breslauer, K J

    1994-07-26

    We use high-precision acoustic and densimetric techniques to determine, at 25 degrees C, the changes in volume, delta V, and adiabatic compressibility, delta Ks, that accompany the binding of netropsin to the poly(dAdT).poly(dAdT) and poly(dA).poly(dT) duplexes, as well as to the poly(dT).poly(dA).poly(dT) triplex. We find that netropsin binding to the heteropolymeric poly(dAdT).poly(dAdT) duplex is accompanied by negative changes in volume, delta V, and small positive changes in compressibility, delta Ks. By contrast, netropsin binding to the homopolymeric poly(dA).poly(dT) duplex is accompanied by large positive changes in both volume, delta V, and compressibility, delta Ks. Furthermore, netropsin binding to the poly(dT).poly(dA).poly(dT) triplex causes changes in both volume and compressibility that are nearly twice as large as those observed when netropsin binds to the poly(dA).poly(dT) duplex. We interpret these macroscopic data in terms of binding-induced microscopic changes in the hydration of the DNA structures and the drug. Specifically, we find that netropsin binding induces the release of approximately 22 waters from the hydration shell of the poly(dAdT).poly(dAdT) heteropolymeric duplex, approximately 40 waters from the hydration shell of the poly(dA).poly(dT) homopolymeric duplex, and about 53 waters from the hydration shell of the poly(dA).poly(dT), induces the release of 18 more water molecules than netropsin binding to the heteropolymeric duplex, poly(dAdT).poly(dAdT). On the basis of apparent molar volume, phi V, and apparent molar adiabatic compressibility, phi Ks, values for the initial drug-free and final drug-bound states of the two all-AT duplexes, we propose that the larger dehydration of the poly(dA).poly(dT) duplex reflects, in part, the formation of a less hydrated poly(dA).poly(dT)-netropsin complex compared with the corresponding poly(dAdT).poly(dAdT)-netropsin complex. In conjunction with our previously published entropy data [Marky, L

  11. Fast camera imaging of dust in the DIII-D tokamak

    NASA Astrophysics Data System (ADS)

    Yu, J. H.; Rudakov, D. L.; Pigarov, A. Yu.; Smirnov, R. D.; Brooks, N. H.; Muller, S. H.; West, W. P.

    2009-06-01

    Naturally occurring and injected dust particles are observed in the DIII-D tokamak in the outer midplane scrape-off-layer (SOL) using a visible fast-framing camera, and the size of dust particles is estimated using the observed particle lifetime and theoretical ablation rate of a carbon sphere. Using this method, the lower limit of detected dust radius is ˜3 μm and particles with inferred radius as large as ˜1 mm are observed. Dust particle 2D velocities range from approximately 10 to 300 m/s with velocities inversely correlated with dust size. Pre-characterized 2-4 μm diameter diamond dust particles are introduced at the lower divertor in an ELMing H-mode discharge using the divertor materials evaluation system (DiMES), and these particles are found to be at the lower size limit of detection using the camera with resolution of ˜0.2 cm 2 per pixel and exposure time of 330 μs.

  12. Enhancement of First Wall Damage in Iter Type Tokamak due to Lenr Effects

    NASA Astrophysics Data System (ADS)

    Lipson, Andrei G.; Miley, George H.; Momota, Hiromu

    In recent experiments with pulsed periodic high current (J ~ 300-500 mA/cm2) D2-glow discharge at deuteron energies as low as 0.8-2.45 keV a large DD-reaction yield has been obtained. Thick target yield measurement show unusually high DD-reaction enhancement (at Ed = 1 keV the yield is about nine orders of magnitude larger than that deduced from standard Bosch and Halle extrapolation of DD-reaction cross-section to lower energies) The results obtained in these LENR experiments with glow discharge suggest nonnegligible edge plasma effects in the ITER TOKAMAK that were previously ignored. In the case of the ITER DT plasma core, we here estimate the DT reaction yield at the metal edge due to plasma ion bombardment of the first wall and/or divertor materials.

  13. 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.

  14. Experimental studies of toroidal correlations of plasma density fluctuations along the magnetic field lines in the T-10 tokamak and first results of numerical modeling

    NASA Astrophysics Data System (ADS)

    Buldakov, M. A.; Vershkov, V. A.; Isaev, M. Yu; Shelukhin, D. A.

    2017-10-01

    The antenna system of reflectometry diagnostics at the T-10 tokamak allows to study long-range toroidal correlations of plasma density fluctuations along the magnetic field lines. The antenna systems are installed in two poloidal cross-sections of the vacuum chamber separated by a 90° angle in the toroidal direction. The experiments, which were conducted at the low field side, showed that the high level of toroidal correlations is observed only for quasi-coherent fluctuations. However, broadband and stochastic low frequency fluctuations are not correlated. Numerical modeling of the plasma turbulence structure in the T-10 tokamak was conducted to interpret the experimental results and take into account non-locality of reflectometry measurements. In the model used, it was assumed that the magnitudes of density fluctuations are constant along the magnetic field lines. The 2D full-wave Tamic-RTH code was used to model the reflectometry signals. High level of correlations for quasi-coherent fluctuations was obtained during the modeling, which agrees with the experimental observations. However, the performed modeling also predicts high level of correlations for broadband fluctuations, which contradicts the experimental data. The modeling showed that the effective reflection radius, from which the information on quasi-coherent plasma turbulence is obtained, is shifted outwards from the reflection radius by approximately 7 mm.

  15. Generation of noninductive current by electron-Bernstein waves on the COMPASS-D Tokamak.

    PubMed

    Shevchenko, V; Baranov, Y; O'Brien, M; Saveliev, A

    2002-12-23

    Electron-Bernstein waves (EBW) were excited in the plasma by mode converted extraordinary (X) waves launched from the high field side of the COMPASS-D tokamak at different toroidal angles. It has been found experimentally that X-mode injection perpendicular to the magnetic field provides maximum heating efficiency. Noninductive currents of up to 100 kA were found to be driven by the EBW mode with countercurrent drive. These results are consistent with ray tracing and quasilinear Fokker-Planck simulations.

  16. Overview of RWM Stabilization and Other Experiments With New Internal Coils in the DIII-D Tokamak

    NASA Astrophysics Data System (ADS)

    Jackson, G. L.; Evans, T. E.; La Haye, R. J.; Kellman, A. G.; Schaffer, M. J.; Scoville, J. T.; Strait, E. J.; Szymanski, D. D.; Bialek, J.; Garofalo, A. M.; Navratil, G. A.; Reimerdes, H.; Edgell, D. H.; Okabayashi, M.; Hatcher, R.

    2003-10-01

    A set of 12 single-turn internal coils (I-coils) has been installed and operated in the DIII-D tokamak. The primary purpose of these coils (A_coil = 1.1 m^2, I ≤,7 kA, d_wall = 1.47 cm) is to improve stabilization of the n=1 resistive wall mode (RWM), compared to the existing external C-coil set, especially for high βN advanced tokamak discharges in low toroidal rotation plasmas. The versatility of the I-coil set and its associated power systems allow for a variety of experiments: fast feedback stabilization of RWMs, dc error field correction, edge stochastic fields, n=1,2, or 3 toroidal magnetic braking, and MHD spectroscopy (0-60 Hz). The resonant field amplification from an applied n=1 field was found to be completely suppressed, demonstrating successfully the controllability with the new system. With the I-coils, the high βN regime (above the no wall limit) has been explored both with RWM feedback and with dynamic error field correction. Experiments on edge ergodization will also be discussed.

  17. 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

  18. 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

  19. Measurement of H/H+D Ratio and Recycling in Ion Cyclotron Resonance Heating HT-6M Tokamak

    NASA Astrophysics Data System (ADS)

    Ding, Liancheng; Jiang, Guangkuan; Wei, Lehan

    1994-12-01

    A scanning Fabry-Perot interferometer has been used to measure the Hα and Dα lines obtain the H/H+D ratio in ion cyclotron resonance heating HT-6M tokamak for determing the energy absorption mechanism. The recycling is observed by changing the working gas from deuterium to hydrogen.

  20. Improved operating scenarios of the DIII-D tokamak as a result of the addition of UNIX computer systems

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

    Henline, P.A.

    1995-12-31

    The increased use of UNIX based computer systems for machine control, data handling and analysis has greatly enhanced the operating scenarios and operating efficiency of the DIII-D tokamak. This paper will describe some of these UNIX systems and their specific uses. These include the plasma control system, the electron cyclotron heating control system, the analysis of electron temperature and density measurements and the general data acquisition system (which is collecting over 130 Mbytes of data). The speed and total capability of these systems has dramatically affected the ability to operate DIII-D. The improved operating scenarios include better plasma shape controlmore » due to the more thorough MHD calculations done between shots and the new ability to see the time dependence of profile data as it relates across different spatial locations in the tokamak. Other analysis which engenders improved operating abilities will be described.« less

  1. Improved operating scenarios of the DIII-D tokamak as a result of the addition of UNIX computer systems

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

    Henline, P.A.

    1995-10-01

    The increased use of UNIX based computer systems for machine control, data handling and analysis has greatly enhanced the operating scenarios and operating efficiency of the DRI-D tokamak. This paper will describe some of these UNIX systems and their specific uses. These include the plasma control system, the electron cyclotron heating control system, the analysis of electron temperature and density measurements and the general data acquisition system (which is collecting over 130 Mbytes of data). The speed and total capability of these systems has dramatically affected the ability to operate DIII-D. The improved operating scenarios include better plasma shape controlmore » due to the more thorough MHD calculations done between shots and the new ability to see the time dependence of profile data as it relates across different spatial locations in the tokamak. Other analysis which engenders improved operating abilities will be described.« less

  2. User's manual for COAST 4: a code for costing and sizing tokamaks

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

    Sink, D. A.; Iwinski, E. M.

    1979-09-01

    The purpose of this report is to document the computer program COAST 4 for the user/analyst. COAST, COst And Size Tokamak reactors, provides complete and self-consistent size models for the engineering features of D-T burning tokamak reactors and associated facilities involving a continuum of performance including highly beam driven through ignited plasma devices. TNS (The Next Step) devices with no tritium breeding or electrical power production are handled as well as power producing and fissile producing fusion-fission hybrid reactors. The code has been normalized with a TFTR calculation which is consistent with cost, size, and performance data published in themore » conceptual design report for that device. Information on code development, computer implementation and detailed user instructions are included in the text.« less

  3. Modernized active spectroscopic diagnostics (CXRS) of the T-10 tokamak

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

    Krupin, V. A., E-mail: Krupin-VA@nrcki.ru; Klyuchnikov, L. A., E-mail: Lklyuchnikov@list.ru; Korobov, K. V., E-mail: Korobov-KV@nrcki.ru

    2015-12-15

    This work presents the results of modernization of the CXRS (charge exchange recombination spectroscopy) diagnostics [1] at the T-10 tokamak. The relevance of this work is due to the importance of measurements of the ion temperature and nuclei density of the working gas and impurities for analysis of transport processes in the plasma ion component. Measurements of radial profiles of the ion temperature are extremely important for investigating the geodesic acoustic mode behavior which is conducted at the T-10 [2]. The modernized scheme of CXRS measurements, as well as the design and operational features of the spectrometer created for themore » new diagnostics, is described. Principles of data recording and further processing are considered in detail; attention is given to the problem of calibration of the whole complex of equipment. The performed changes in diagnostics allow the measurements to be taken simultaneously in three spectral intervals: in the region of the beam line H{sub α}, the CXRS line of carbon ion C{sup 5+}, and the CXRS line of one of the hydrogen-like ions: He{sup 1+}, Li{sup 2+}, N{sup 6+}, O{sup 7+} or Ne{sup 9+}. This makes it possible to measure the density profiles of two plasma impurities simultaneously, as well as the ion temperature from CXRS lines of different elements. The modernized diagnostics significantly broadens the possibilities of studying the physics of transport processes and quasi-coherent modes of plasma oscillations at the T-10.« less

  4. The Spherical Tokamak MEDUSA for Mexico

    NASA Astrophysics Data System (ADS)

    Ribeiro, C.; Salvador, M.; Gonzalez, J.; Munoz, O.; Tapia, A.; Arredondo, V.; Chavez, R.; Nieto, A.; Gonzalez, J.; Garza, A.; Estrada, I.; Jasso, E.; Acosta, C.; Briones, C.; Cavazos, G.; Martinez, J.; Morones, J.; Almaguer, J.; Fonck, R.

    2011-10-01

    The former spherical tokamak MEDUSA (Madison EDUcation Small Aspect.ratio tokamak, R < 0.14m, a < 0.10m, BT < 0.5T, Ip < 40kA, 3ms pulse) is currently being recomissioned at the Universidad Autónoma de Nuevo León, Mexico, as part of an agreement between the Faculties of Mech.-Elect. Eng. and Phy. Sci.-Maths. The main objective for having MEDUSA is to train students in plasma physics & technical related issues, aiming a full design of a medium size device (e.g. Tokamak-T). Details of technical modifications and a preliminary scientific programme will be presented. MEDUSA-MX will also benefit any developments in the existing Mexican Fusion Network. Strong liaison within national and international plasma physics communities is expected. New activities on plasma & engineering modeling are expected to be developed in parallel by using the existing facilities such as a multi-platform computer (Silicon Graphics Altix XE250, 128G RAM, 3.7TB HD, 2.7GHz, quad-core processor), ancillary graph system (NVIDIA Quadro FE 2000/1GB GDDR-5 PCI X16 128, 3.2GHz), and COMSOL Multiphysics-Solid Works programs.

  5. Scoping study for compact high-field superconducting net energy tokamaks

    NASA Astrophysics Data System (ADS)

    Mumgaard, R. T.; Greenwald, M.; Freidberg, J. P.; Wolfe, S. M.; Hartwig, Z. S.; Brunner, D.; Sorbom, B. N.; Whyte, D. G.

    2016-10-01

    The continued development and commercialization of high temperature superconductors (HTS) may enable the construction of compact, net-energy tokamaks. HTS, in contrast to present generation low temperature superconductors, offers improved performance in high magnetic fields, higher current density, stronger materials, higher temperature operation, and simplified assembly. Using HTS along with community-consensus confinement physics (H98 =1) may make it possible to achieve net-energy (Q>1) or burning plasma conditions (Q>5) in DIII-D or ASDEX-U sized, conventional aspect ratio tokamaks. It is shown that, by operating at high plasma current and density enabled by the high magnetic field (B>10T), the required triple products may be achieved at plasma volumes under 20m3, major radii under 2m, with external heating powers under 40MW. This is at the scale of existing devices operated by laboratories, universities and companies. The trade-offs in the core heating, divertor heat exhaust, sustainment, stability, and proximity to known plasma physics limits are discussed in the context of the present tokamak experience base and the requirements for future devices. The resulting HTS-based design space is compared and contrasted to previous studies on high-field copper experiments with similar missions. The physics exploration conducted with such HTS devices could decrease the real and perceived risks of ITER exploitation, and aid in quickly developing commercially-applicable tokamak pilot plants and reactors.

  6. Thin isotropic FLAIR MR images at 1.5T increase the yield of focal cortical dysplasia transmantle sign detection in frontal lobe epilepsy.

    PubMed

    Kokkinos, Vasileios; Kallifatidis, Alexandros; Kapsalaki, Eftychia Z; Papanikolaou, Nikolaos; Garganis, Kyriakos

    2017-05-01

    The transmantle sign is a distinctive imaging marker of focal cortical dysplasia (FCD) type II in frontal lobe epilepsy (FLE), which is revealed predominantly by fluid-attenuation inversion recovery (FLAIR) sequences. Although the transmantle sign detection yield is high by routine imaging protocols for epilepsy at 3T, most centers around the world have access to 1.5T MR technology and FLE patients often receive negative imaging reports. This study investigates the optimization of transmantle detection yield at 1.5T by introducing a 3D thin-slice isotropic FLAIR sequence in the epilepsy imaging protocol. Twenty FLE patients underwent diagnostic imaging for epilepsy with typical 2D thick-slice (3.0mm) coronal FLAIR sequences and a 3D thin-slice (1.0mm) isotropic FLAIR sequences at 1.5T, and transmantle sign detection yields and thickness measurements were derived. The 2D thick-slice FLAIR detected a transmantle sign in seven (35.0%) patients. The 3D isotropic thin-slice FLAIR detected a transmantle sign in eleven (55.0%) patients, thereby increasing the transmantle sign detection yield by 57.4%. The mean transmantle sign thickness by thick images was 12.3mm, by thin images was 8.9mm, and in the patients undetected by thick FLAIR was 3.5mm. This study showed that the extratemporal transmantle sign in FLE patients can be thin enough to be missed by thick-slice FLAIR sequences at 1.5T. By introducing 3D thin-slice isotropic FLAIR, false-negative reports can be reduced without reference for higher MR field structural scanning or other modalities, and more FLE patients can benefit from epilepsy surgery candidacy. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Fully 3D modeling of tokamak vertical displacement events with realistic parameters

    NASA Astrophysics Data System (ADS)

    Pfefferle, David; Ferraro, Nathaniel; Jardin, Stephen; Bhattacharjee, Amitava

    2016-10-01

    In this work, we model the complex multi-domain and highly non-linear physics of Vertical Displacement Events (VDEs), one of the most damaging off-normal events in tokamaks, with the implicit 3D extended MHD code M3D-C1. The code has recently acquired the capability to include finite thickness conducting structures within the computational domain. By exploiting the possibility of running a linear 3D calculation on top of a non-linear 2D simulation, we monitor the non-axisymmetric stability and assess the eigen-structure of kink modes as the simulation proceeds. Once a stability boundary is crossed, a fully 3D non-linear calculation is launched for the remainder of the simulation, starting from an earlier time of the 2D run. This procedure, along with adaptive zoning, greatly increases the efficiency of the calculation, and allows to perform VDE simulations with realistic parameters and high resolution. Simulations are being validated with NSTX data where both axisymmetric (toroidally averaged) and non-axisymmetric induced and conductive (halo) currents have been measured. This work is supported by US DOE Grant DE-AC02-09CH11466.

  8. Nonlinear 3D MHD verification study: SpeCyl and PIXIE3D codes for RFP and Tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Bonfiglio, D.; Cappello, S.; Chacon, L.

    2010-11-01

    A strong emphasis is presently placed in the fusion community on reaching predictive capability of computational models. An essential requirement of such endeavor is the process of assessing the mathematical correctness of computational tools, termed verification [1]. We present here a successful nonlinear cross-benchmark verification study between the 3D nonlinear MHD codes SpeCyl [2] and PIXIE3D [3]. Excellent quantitative agreement is obtained in both 2D and 3D nonlinear visco-resistive dynamics for reversed-field pinch (RFP) and tokamak configurations [4]. RFP dynamics, in particular, lends itself as an ideal non trivial test-bed for 3D nonlinear verification. Perspectives for future application of the fully-implicit parallel code PIXIE3D to RFP physics, in particular to address open issues on RFP helical self-organization, will be provided. [4pt] [1] M. Greenwald, Phys. Plasmas 17, 058101 (2010) [0pt] [2] S. Cappello and D. Biskamp, Nucl. Fusion 36, 571 (1996) [0pt] [3] L. Chac'on, Phys. Plasmas 15, 056103 (2008) [0pt] [4] D. Bonfiglio, L. Chac'on and S. Cappello, Phys. Plasmas 17 (2010)

  9. Development of lithium and tungsten limiters for test on T-10 tokamak at high heat load condition

    NASA Astrophysics Data System (ADS)

    Lyublinski, I. E.; Vertkov, A. V.; Zharkov, M. Yu; Vershkov, V. A.; Mirnov, S. V.

    2016-04-01

    Application of a complex of powerful (up to 3 MW) ECR plasma heating in T-10 tokamak is pulled down with a problem of the strong plasma pollution at power input more than 2 MW. For the solution of these problems the new W and Li limiters is developed and prepared to implementation. As it is supposed, application of W as a plasma facing material will allow excluding carbon influx into vacuum chamber. An additional Li limiter arranged in a shadow of W one will be used as a Li source for plasma periphery cooling due to a reradiation on Li that will lead to decrease in power deposition on W limiters. Parameters and design of limiters are presented. Plasma facing surface of a limiter is made of capillary-porous system (CPS) with Li. Porous matrix of CPS (W felt) provides stability of liquid Li surface under MHD force effect and an opportunity of its constant renewal due to capillary forces. The necessary Li flux from a Li limiter surface is estimated for maintenance of normal operation mode of W limiters at ECRH power of 3 MW during 400 ms. It is shown, that upgrade of limiters in tokamak T-10 will allow providing of ECR plasma heating with power up to 3 MW at reasonable Li flux.

  10. Bifurcated helical core equilibrium states in tokamaks

    NASA Astrophysics Data System (ADS)

    Cooper, W. A.; Chapman, I. T.; Schmitz, O.; Turnbull, A. D.; Tobias, B. J.; Lazarus, E. A.; Turco, F.; Lanctot, M. J.; Evans, T. E.; Graves, J. P.; Brunetti, D.; Pfefferlé, D.; Reimerdes, H.; Sauter, O.; Halpern, F. D.; Tran, T. M.; Coda, S.; Duval, B. P.; Labit, B.; Pochelon, A.; Turnyanskiy, M. R.; Lao, L.; Luce, T. C.; Buttery, R.; Ferron, J. R.; Hollmann, E. M.; Petty, C. C.; van Zeeland, M.; Fenstermacher, M. E.; Hanson, J. M.; Lütjens, H.

    2013-07-01

    Tokamaks with weak to moderate reversed central shear in which the minimum inverse rotational transform (safety factor) qmin is in the neighbourhood of unity can trigger bifurcated magnetohydrodynamic equilibrium states, one of which is similar to a saturated ideal internal kink mode. Peaked prescribed pressure profiles reproduce the ‘snake’ structures observed in many tokamaks which has led to a novel explanation of the snake as a bifurcated equilibrium state. Snake equilibrium structures are computed in simulations of the tokamak à configuration variable (TCV), DIII-D and mega amp spherical torus (MAST) tokamaks. The internal helical deformations only weakly modulate the plasma-vacuum interface which is more sensitive to ripple and resonant magnetic perturbations. On the other hand, the external perturbations do not alter the helical core deformation in a significant manner. The confinement of fast particles in MAST simulations deteriorate with the amplitude of the helical core distortion. These three-dimensional bifurcated solutions constitute a paradigm shift that motivates the applications of tools developed for stellarator research in tokamak physics investigations.

  11. Anomalous DD and TT yields relative to the DT yield in inertial-confinement-fusion implosions

    NASA Astrophysics Data System (ADS)

    Casey, Daniel T.

    2011-10-01

    Measurements of the D(d,p)T (DD), T(t,2n)4He (TT) and D(t,n)4He (DT) reactions have been conducted using deuterium-tritium gas-filled inertial confinement fusion (ICF) implosions. In these experiments, which were carried out at the OMEGA laser facility, absolute spectral measurements of the DD protons and TT neutrons were conducted and compared to neutron-time-of-flight measured DT-neutron yields. From these measurements, it is concluded that the DD yield is anomalously low and the TT yield is anomalously high relative to the DT yield, an effect that is enhanced with increasing ion temperature. These results can be explained by an enrichment of tritium in the core of an ICF implosion, which may be present in ignition experiments planned on the National Ignition Facility. In addition, the spectral measurements of the TT-neutron spectrum were conducted for the first time at reactant central-mass energies in the range of 15-30 keV. The results from these measurements indicate that the TT reaction proceeds primarily through the direct three-body reaction channel, producing a continuous TT-neutron spectrum in the range 0 - 9.5 MeV. This work was conducted in collaboration with J. A. Frenje, M. Gatu Johnson, M. J.-E. Manuel, H. G. Rinderknecht, N. Sinenian, F. H. Seguin, C. K. Li, R. D. Petrasso, P. B. Radha, J. A. Delettrez, V. Yu Glebov, D. D. Meyerhofer, T. C. Sangster, D. P. McNabb, P. A. Amendt, R. N. Boyd, J. R. Rygg, H. W. Herrmann, Y. H. Kim, G. P. Grim and A. D. Bacher. This work was supported in part by the U.S. Department of Energy (Grant No. DE-FG03-03SF22691), LLE (subcontract Grant No. 412160-001G), LLNL (subcontract Grant No. B504974).

  12. MHD Instabilities and Toroidal Field Effects on Plasma Column Behavior in Tokamak

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

    Khorshid, Pejman; Plasma Physics Research Center, Islamic Azad University, 14665-678, Tehran; Wang, L.

    2006-12-04

    In the edge plasma of the CT-6B and IRAN-T1 tokamaks the shape of plasma column based on MHD behavior has been studied. The bulk of plasma behavior during plasma column rotation as non-rigid body plasma has been investigated. We found that mode number and rotation frequency of plasma column are different in angle position, so that the mode number detected from Mirnov coils array located in poloidal angle on the inner side of chamber is more than outer side which it can be because of toroidal magnetic field effects. The results of IR-T1 and CT-6B tokamaks compared with each other,more » so that in the CT-6B because of its coils number must be less, but because of its Iron core the effect of toroidal magnetic field became more effective with respect to IR-T1. In addition, it is shown that the plasma column behaves as non-Rigid body plasma so that the poloidal rotation velocity variation in CT-6B is more than IR-T1. A relative correction for island rotation frequency has been suggested in connection with IRAN-T1 and CT-6B tokamak results, which can be considered for optical measurement purposes and also for future advanced tokamak control design.« less

  13. GBS: Global 3D simulation of tokamak edge region

    NASA Astrophysics Data System (ADS)

    Zhu, Ben; Fisher, Dustin; Rogers, Barrett; Ricci, Paolo

    2012-10-01

    A 3D two-fluid global code, namely Global Braginskii Solver (GBS), is being developed to explore the physics of turbulent transport, confinement, self-consistent profile formation, pedestal scaling and related phenomena in the edge region of tokamaks. Aimed at solving drift-reduced Braginskii equations [1] in complex magnetic geometry, the GBS is used for turbulence simulation in SOL region. In the recent upgrade, the simulation domain is expanded into close flux region with twist-shift boundary conditions. Hence, the new GBS code is able to explore global transport physics in an annular full-torus domain from the top of the pedestal into the far SOL. We are in the process of identifying and analyzing the linear and nonlinear instabilities in the system using the new GBS code. Preliminary results will be presented and compared with other codes if possible.[4pt] [1] A. Zeiler, J. F. Drake and B. Rogers, Phys. Plasmas 4, 2134 (1997)

  14. Poloidal flux profile reconstruction from pointwise measurements via extended Kalman filtering in the DIII-D Tokamak

    DOE PAGES

    Wang, Hexiang; Barton, Justin E.; Schuster, Eugenio

    2015-09-01

    The accuracy of the internal states of a tokamak, which usually cannot be measured directly, is of crucial importance for feedback control of the plasma dynamics. A first-principles-driven plasma response model could provide an estimation of the internal states given the boundary conditions on the magnetic axis and at plasma boundary. However, the estimation would highly depend on initial conditions, which may not always be known, disturbances, and non-modeled dynamics. Here in this work, a closed-loop state observer for the poloidal magnetic flux is proposed based on a very limited set of real-time measurements by following an Extended Kalman Filteringmore » (EKF) approach. Comparisons between estimated and measured magnetic flux profiles are carried out for several discharges in the DIII-D tokamak. The experimental results illustrate the capability of the proposed observer in dealing with incorrect initial conditions and measurement noise.« less

  15. The Aneutronic Rodless Ultra Low Aspect Ratio Tokamak

    NASA Astrophysics Data System (ADS)

    Ribeiro, Celso

    2016-10-01

    The replacement of the metal centre-post in spherical tokamaks (STs) by a plasma centre-post (PCP, the TF current carrier) is the ideal scenario for a ST reactor. A simple rodless ultra low aspect-ratio tokamak (RULART) using a screw-pinch PCP ECR-assisted with an external solenoid has been proposed in the most compact RULART [Ribeiro C, SOFE-15]. There the solenoid provided the stabilizing field for the PCP and the toroidal electrical field for the tokamak start-up, which will stabilize further the PCP, acting as stabilizing closed conducting surface. Relative low TF will be required. The compactness (high ratio of plasma-spherical vessel volume) may provide passive stabilization and easier access to L-H mode transition. It is presented here: 1) stability analysis of the PCP (initially MHD stable due to the hollow J profile); 2) tokamak equilibrium simulations, and 3) potential use for aneutronic reactions studies via pairs of proton p and boron 11B ion beams in He plasmas. The beams' line-of-sights sufficiently miss the sources of each other, thus allowing a near maximum relative velocities and reactivity. The reactions should occur close to the PCP mid-plane. Some born alphas should cross the PCP and be dragged by the ion flow (higher momentum exchange) towards the anode but escape directly to a direct electricity converter. Others will reach evenly the vessel directly or via thermal diffusion (favourable heating by the large excursion 2a), leading to the lowest power wall load possible. This might be a potential hybrid direct-steam cycle conversion reactor scheme, nearly aneutronic, and with no ash or particle retention problems, as opposed to the D-T thermal reaction proposals.

  16. T-T Neutron Spectrum from Inertial Confinement Implosions

    NASA Astrophysics Data System (ADS)

    Bacher, A. D.; Casey, D. T.; Frenje, J. A.; Gatu Johnson, M. J.; Manuel, M.; Sinenian, N.; Zylstra, A. B.; Séguin, F. H.; Li, C. K.; Petrasso, R. D.; Glebov, V. Yu; Radha, P. B.; Meyerhofer, D. D.; Sangster, T. C.; McNabb, D. P.; Amendt, P. A.; Boyd, R. N.; Caggiano, J. A.; Hatchett, S. P.; Pino, J. E.; Quaglioni, S.; Rygg, J. R.; Thompson, I. J.; Herrmann, H. W.; Kim, Y. H.

    2013-08-01

    A new technique that uses inertial confinement implosions for measuring low-energy nuclear reactions important to nuclear astrophysics is described. Simultaneous measurements of n-D and n-T elastic scattering at 14.1 MeV using deuterium-tritium gas-filled capsules provide a proof of principle for this technique. Measurements have been made of D(d,p)T (dd) and T(t,2n)4He (tt) reaction yields relative to the D(t,n)4He (dt) reaction yield for deuterium-tritium mixtures with f T / f D between 0.62 and 0.75 and for a wide range of ion temperatures to test our understanding of the implosion processes. Measurements of the shape of the neutron spectrum from the T(t,2n)4He reaction have been made for each of these target configurations.

  17. Compact Torus Fueling of the STOR-M Tokamak

    NASA Astrophysics Data System (ADS)

    Xiao, C.; Hirose, A.; Zawalski, W.; White, D.; Raman, R.; Decoste, R.; Gregory, B. C.; Martin, F.

    1996-11-01

    Tangential injection of accelerated compact torus (CT) has been performed on the STOR-M tokamak (R/a=46/12 cm, B_t<1 T, I_p<= 50 kA, barn_e=(0.5 - 1)×10^13 cm-3) using the University of Saskatchewan Compact Torus Injector (USCTI). The CT parameters are: m~=1 μg, v=120 km/sec, B=0.1 T and n=(2 - 4)×10^15 cm-3. After CT injection, the electron density in tokamak doubles and the poloidal β-value increases. Indications of reduction in the loop voltage and H_α emission level have also been observed. Currently, following efforts are being made: (a) to coat chromium on the electrode surface, (b) to increase the on-line baking temperature, and (c) to reduce the neutral gas load which follows the CT plasma. In addition, numerical calculation of CT motion in a tokamak magnetic field has been carried out. For horizontal injection, the initial CT magnetic dipole direction should be aligned with the CT velocity for deeper penetration. In the case of vertical injection, the CT trajectory is independent of the initial magnetic dipole direction and central penetration is facilitated by off-axis injection.

  18. Dynamics of tokamak plasma surface current in 3D ideal MHD model

    NASA Astrophysics Data System (ADS)

    Galkin, Sergei A.; Svidzinski, V. A.; Zakharov, L. E.

    2013-10-01

    Interest in the surface current which can arise on perturbed sharp plasma vacuum interface in tokamaks was recently generated by a few papers (see and references therein). In dangerous disruption events with plasma-touching-wall scenarios, the surface current can be shared with the wall leading to the strong, damaging forces acting on the wall A relatively simple analytic definition of δ-function surface current proportional to a jump of tangential component of magnetic field nevertheless leads to a complex computational problem on the moving plasma-vacuum interface, requiring the incorporation of non-linear 3D plasma dynamics even in one-fluid ideal MHD. The Disruption Simulation Code (DSC), which had recently been developed in a fully 3D toroidal geometry with adaptation to the moving plasma boundary, is an appropriate tool for accurate self-consistent δfunction surface current calculation. Progress on the DSC-3D development will be presented. Self-consistent surface current calculation under non-linear dynamics of low m kink mode and VDE will be discussed. Work is supported by the US DOE SBIR grant #DE-SC0004487.

  19. Dependence of intrinsic torque and momentum confinement on normalized gyroradius and collisionality in the DIII-D tokamak

    DOE PAGES

    Chrystal, C.; Grierson, B. A.; Solomon, W. M.; ...

    2017-03-29

    We measured the dependence of intrinsic torque and momentum confinement time on normalized gyroradius (ρ *) and collisionality (v *) in the DIII-D tokamak. The intrinsic torque normalized to temperature is found to have ρ * and v * dependencies of ρ * -1.5 ± 0.8 and v * -0.26 ± 0.04. This dependence on ρ * is unexpectedly favorable (increasing as ρ * decreases). The choice of normalization is important, and the implications are discussed. The unexpected dependence on ρ * is found to be robust, despite some uncertainty in the choice of normalization. Furthermore, the dependence of momentummore » confinement on ρ * does not clearly demonstrate Bohm or gyro-Bohm like scaling, and a weaker dependence on v * is found. The calculations required to use these dependencies to determine the intrinsic torque in future tokamaks such as ITER are presented, and the importance of the normalization is explained. Based on the currently available information, the intrinsic torque predicted for ITER is 33 N m, comparable to the expected torque available from neutral beam injection. The expected average intrinsic rotation associated with this intrinsic torque is small compared to current tokamaks, but it may still aid stability and performance in ITER. Published by AIP Publishing.« less

  20. Performance of V-4Cr-4Ti material exposed to DIII-D tokamak environment

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

    Tsai, H.; Chung, H.M.; Smith, D.L.

    1997-04-01

    Test specimens made with the 832665 heat of V-4Cr-4Ti alloy were exposed in the DIII-D tokamak environment to support the installation of components made of a V-4Cr-4Ti alloy in the radiative divertor of the DIII-D. Some of the tests were conducted with the Divertor Materials Evaluation System (DiMES) to study the short-term effects of postvent bakeout, when concentrations of gaseous impurities in the DIII-D chamber are the highest. Other specimens were mounted next to the chamber wall behind the divertor baffle plate, to study the effects of longer-term exposures. By design, none of the specimens directly interacted with the plasma.more » Preliminary results from testing the exposed specimens indicate only minor degradation of mechanical properties. Additional testing and microstructural characterization are in progress.« less

  1. A spatially resolving x-ray crystal spectrometer for measurement of ion-temperature and rotation-velocity profiles on the Alcator C-Mod tokamak.

    PubMed

    Hill, K W; Bitter, M L; Scott, S D; Ince-Cushman, A; Reinke, M; Rice, J E; Beiersdorfer, P; Gu, M-F; Lee, S G; Broennimann, Ch; Eikenberry, E F

    2008-10-01

    A new spatially resolving x-ray crystal spectrometer capable of measuring continuous spatial profiles of high resolution spectra (lambda/d lambda>6000) of He-like and H-like Ar K alpha lines with good spatial (approximately 1 cm) and temporal (approximately 10 ms) resolutions has been installed on the Alcator C-Mod tokamak. Two spherically bent crystals image the spectra onto four two-dimensional Pilatus II pixel detectors. Tomographic inversion enables inference of local line emissivity, ion temperature (T(i)), and toroidal plasma rotation velocity (upsilon(phi)) from the line Doppler widths and shifts. The data analysis techniques, T(i) and upsilon(phi) profiles, analysis of fusion-neutron background, and predictions of performance on other tokamaks, including ITER, will be presented.

  2. OMFIT Tokamak Profile Data Fitting and Physics Analysis

    DOE PAGES

    Logan, N. C.; Grierson, B. A.; Haskey, S. R.; ...

    2018-01-22

    Here, One Modeling Framework for Integrated Tasks (OMFIT) has been used to develop a consistent tool for interfacing with, mapping, visualizing, and fitting tokamak profile measurements. OMFIT is used to integrate the many diverse diagnostics on multiple tokamak devices into a regular data structure, consistently applying spatial and temporal treatments to each channel of data. Tokamak data are fundamentally time dependent and are treated so from the start, with front-loaded and logic-based manipulations such as filtering based on the identification of edge-localized modes (ELMs) that commonly scatter data. Fitting is general in its approach, and tailorable in its application inmore » order to address physics constraints and handle the multiple spatial and temporal scales involved. Although community standard one-dimensional fitting is supported, including scale length–fitting and fitting polynomial-exponential blends to capture the H-mode pedestal, OMFITprofiles includes two-dimensional (2-D) fitting using bivariate splines or radial basis functions. These 2-D fits produce regular evolutions in time, removing jitter that has historically been smoothed ad hoc in transport applications. Profiles interface directly with a wide variety of models within the OMFIT framework, providing the inputs for TRANSP, kinetic-EFIT 2-D equilibrium, and GPEC three-dimensional equilibrium calculations. he OMFITprofiles tool’s rapid and comprehensive analysis of dynamic plasma profiles thus provides the critical link between raw tokamak data and simulations necessary for physics understanding.« less

  3. OMFIT Tokamak Profile Data Fitting and Physics Analysis

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

    Logan, N. C.; Grierson, B. A.; Haskey, S. R.

    Here, One Modeling Framework for Integrated Tasks (OMFIT) has been used to develop a consistent tool for interfacing with, mapping, visualizing, and fitting tokamak profile measurements. OMFIT is used to integrate the many diverse diagnostics on multiple tokamak devices into a regular data structure, consistently applying spatial and temporal treatments to each channel of data. Tokamak data are fundamentally time dependent and are treated so from the start, with front-loaded and logic-based manipulations such as filtering based on the identification of edge-localized modes (ELMs) that commonly scatter data. Fitting is general in its approach, and tailorable in its application inmore » order to address physics constraints and handle the multiple spatial and temporal scales involved. Although community standard one-dimensional fitting is supported, including scale length–fitting and fitting polynomial-exponential blends to capture the H-mode pedestal, OMFITprofiles includes two-dimensional (2-D) fitting using bivariate splines or radial basis functions. These 2-D fits produce regular evolutions in time, removing jitter that has historically been smoothed ad hoc in transport applications. Profiles interface directly with a wide variety of models within the OMFIT framework, providing the inputs for TRANSP, kinetic-EFIT 2-D equilibrium, and GPEC three-dimensional equilibrium calculations. he OMFITprofiles tool’s rapid and comprehensive analysis of dynamic plasma profiles thus provides the critical link between raw tokamak data and simulations necessary for physics understanding.« less

  4. Startup and stability of a small spherical tokamak

    NASA Astrophysics Data System (ADS)

    Garstka, Gregory Douglas

    1997-09-01

    The spherical tokamak (ST) is an evolutionary extension of the conventional tokamak concept where the aspect ratio is less than 2. These devices may possess significant advantages over standard tokamaks-they are capable of achieving higher values of /beta, seem to be more resilient to disruptions, and are significantly smaller than conventional tokamaks. Two important questions for the next generation of spherical tokamaks concern startup and internal reconnection events (IREs). Understanding startup is crucial due to the limited amount of ohmic flux in an ST. The IREs are disruption- like events observed on STs that do not result in termination of the current channel. Experiments have been conducted on the Madison EDUcational Small Aspect-ratio (MEDUSA) tokamak to answer some of the questions about startup and IREs in STs. MEDUSA is a small ohmic tokamak with an insulating vacuum vessel. Major parameters are R=12 cm, a=8 cm, Ip=10-40 kA, BT=0.2-0.45 T, /Delta tpulse=1-2 ms, /langle ne/rangle/approx5×1019/ m-3, and Te0/approx100 eV. The experiments in this work were aided by an internal magnetic probe array that constrained the reconstruction of MHD equilibria. It was found that startup efficiency, measured by the Ejima coefficient CE, improved with increasing loop voltage and toroidal field. Double tearing modes were found to be an important mechanism for current penetration in MEDUSA; their presence early in the discharge can improve the magnetic flux consumption. The lowest achieved value of the Ejima coefficient was 0.61 (0.13 for 'OH only') for a discharge with 0.375 T toroidal field and 9.4 V startup loop voltage. The study of internal reconnection events revealed the presence of a heretofore undiscovered precursor, which in MEDUSA was manifested as coherent oscillations in the internal poloidal field at 65-75 kHz for 100 μs prior to the IRE. These events were found to result in decreased /ell i and /beta, inward movement of the magnetic axis, dramatically

  5. D-T Neutron Skyshine Experiments at JAERI/FNS

    NASA Astrophysics Data System (ADS)

    Nishitani, Takeo; Ochiai, Kentaro; Yoshida, Shigeo; Tanaka, Ryohei; Wakisaka, Masashi; Nakao, Makoto; Sato, Satoshi; Yamauchi, Michinori; Hori, Jun-Ichi; Takahashi, Akito; Kaneko, Jun-Ichi; Sawamura, Teruko

    The D-T neutron skyshine experiments have been carried out at the Fusion Neutronics Source (FNS) of JAERI with the neutron yield of ˜1.7×1011n/s. The concrete thickness of the roof and the wall of a FNS target room are 1.15 and 2 m, respectively. The FNS skyshine port with a size of 0.9 × 0.9 m2 was open during the experimental period.The radiation dose rate outside the target room was measured as far as about 550 m away from the D-T target point with a spherical rem-counter. The highest neutron dose was about 0.5 μSv/hr at a distance of 30 m from the D-T target point and the dose rate was attenuated to 0.002 μSv/hr at a distance of 550 m. The measured neutron dose distribution was analyzed with Monte Carlo code MCNP-4B and a simple line source model. The MCNP calculation overestimates the neutron dose in the distance range larger than 250 m. The neutron spectra were evaluated with a 3He detector with different thickness of polyethylene neutron moderators. Secondary gamma-rays were measured with high purity Ge detectors and NaI scintillation detectors.

  6. Use of reconstructed 3D equilibria to determine onset conditions of helical cores in tokamaks for extrapolation to ITER

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

    Wingen, A.; Wilcox, R. S.; Seal, S. K.

    In this paper, large, spontaneous m/n = 1/1 helical cores are shown to be expected in tokamaks such as ITER with extended regions of low- or reversed- magnetic shear profiles and q near 1 in the core. The threshold for this spontaneous symmetry breaking is determined using VMEC scans, beginning with reconstructed 3D equilibria from DIII-D and Alcator C-Mod based on observed internal 3D deformations. The helical core is a saturated internal kink mode (Wesson 1986 Plasma Phys. Control. Fusion 28 243); its onset threshold is shown to be proportional tomore » $$({\\rm d}p/{\\rm d}\\rho)/B_t^2$$ around q = 1. Below the threshold, applied 3D fields can drive a helical core to finite size, as in DIII-D. The helical core size thereby depends on the magnitude of the applied perturbation. Above it, a small, random 3D kick causes a bifurcation from axisymmetry and excites a spontaneous helical core, which is independent of the kick size. Systematic scans of the q-profile show that the onset threshold is very sensitive to the q-shear in the core. Helical cores occur frequently in Alcator C-Mod during ramp-up when slow current penetration results in a reversed shear q-profile, which is favorable for helical core formation. In conclusion, a comparison of the helical core onset threshold for discharges from DIII-D, Alcator C-Mod and ITER confirms that while DIII-D is marginally stable, Alcator C-Mod and especially ITER are highly susceptible to helical core formation without being driven by an externally applied 3D magnetic field.« less

  7. Use of reconstructed 3D equilibria to determine onset conditions of helical cores in tokamaks for extrapolation to ITER

    DOE PAGES

    Wingen, A.; Wilcox, R. S.; Seal, S. K.; ...

    2018-01-15

    In this paper, large, spontaneous m/n = 1/1 helical cores are shown to be expected in tokamaks such as ITER with extended regions of low- or reversed- magnetic shear profiles and q near 1 in the core. The threshold for this spontaneous symmetry breaking is determined using VMEC scans, beginning with reconstructed 3D equilibria from DIII-D and Alcator C-Mod based on observed internal 3D deformations. The helical core is a saturated internal kink mode (Wesson 1986 Plasma Phys. Control. Fusion 28 243); its onset threshold is shown to be proportional tomore » $$({\\rm d}p/{\\rm d}\\rho)/B_t^2$$ around q = 1. Below the threshold, applied 3D fields can drive a helical core to finite size, as in DIII-D. The helical core size thereby depends on the magnitude of the applied perturbation. Above it, a small, random 3D kick causes a bifurcation from axisymmetry and excites a spontaneous helical core, which is independent of the kick size. Systematic scans of the q-profile show that the onset threshold is very sensitive to the q-shear in the core. Helical cores occur frequently in Alcator C-Mod during ramp-up when slow current penetration results in a reversed shear q-profile, which is favorable for helical core formation. In conclusion, a comparison of the helical core onset threshold for discharges from DIII-D, Alcator C-Mod and ITER confirms that while DIII-D is marginally stable, Alcator C-Mod and especially ITER are highly susceptible to helical core formation without being driven by an externally applied 3D magnetic field.« less

  8. High spatial resolution upgrade of the electron cyclotron emission radiometer for the DIII-D tokamak.

    PubMed

    Truong, D D; Austin, M E

    2014-11-01

    The 40-channel DIII-D electron cyclotron emission (ECE) radiometer provides measurements of Te(r,t) at the tokamak midplane from optically thick, second harmonic X-mode emission over a frequency range of 83-130 GHz. The frequency spacing of the radiometer's channels results in a spatial resolution of ∼1-3 cm, depending on local magnetic field and electron temperature. A new high resolution subsystem has been added to the DIII-D ECE radiometer to make sub-centimeter (0.6-0.8 cm) resolution Te measurements. The high resolution subsystem branches off from the regular channels' IF bands and consists of a microwave switch to toggle between IF bands, a switched filter bank for frequency selectivity, an adjustable local oscillator and mixer for further frequency down-conversion, and a set of eight microwave filters in the 2-4 GHz range. Higher spatial resolution is achieved through the use of a narrower (200 MHz) filter bandwidth and closer spacing between the filters' center frequencies (250 MHz). This configuration allows for full coverage of the 83-130 GHz frequency range in 2 GHz bands. Depending on the local magnetic field, this translates into a "zoomed-in" analysis of a ∼2-4 cm radial region. Expected uses of these channels include mapping the spatial dependence of Alfven eigenmodes, geodesic acoustic modes, and externally applied magnetic perturbations. Initial Te measurements, which demonstrate that the desired resolution is achieved, are presented.

  9. Use of reconstructed 3D equilibria to determine onset conditions of helical cores in tokamaks for extrapolation to ITER

    NASA Astrophysics Data System (ADS)

    Wingen, A.; Wilcox, R. S.; Seal, S. K.; Unterberg, E. A.; Cianciosa, M. R.; Delgado-Aparicio, L. F.; Hirshman, S. P.; Lao, L. L.

    2018-03-01

    Large, spontaneous m/n  =  1/1 helical cores are shown to be expected in tokamaks such as ITER with extended regions of low- or reversed- magnetic shear profiles and q near 1 in the core. The threshold for this spontaneous symmetry breaking is determined using VMEC scans, beginning with reconstructed 3D equilibria from DIII-D and Alcator C-Mod based on observed internal 3D deformations. The helical core is a saturated internal kink mode (Wesson 1986 Plasma Phys. Control. Fusion 28 243); its onset threshold is shown to be proportional to (dp/dρ)/B_t2 around q  =  1. Below the threshold, applied 3D fields can drive a helical core to finite size, as in DIII-D. The helical core size thereby depends on the magnitude of the applied perturbation. Above it, a small, random 3D kick causes a bifurcation from axisymmetry and excites a spontaneous helical core, which is independent of the kick size. Systematic scans of the q-profile show that the onset threshold is very sensitive to the q-shear in the core. Helical cores occur frequently in Alcator C-Mod during ramp-up when slow current penetration results in a reversed shear q-profile, which is favorable for helical core formation. Finally, a comparison of the helical core onset threshold for discharges from DIII-D, Alcator C-Mod and ITER confirms that while DIII-D is marginally stable, Alcator C-Mod and especially ITER are highly susceptible to helical core formation without being driven by an externally applied 3D magnetic field.

  10. Physics of Tokamak Plasma Start-up

    NASA Astrophysics Data System (ADS)

    Mueller, Dennis

    2012-10-01

    This tutorial describes and reviews the state-of-art in tokamak plasma start-up and its importance to next step devices such as ITER, a Fusion Nuclear Science Facility and a Tokamak/ST demo. Tokamak plasma start-up includes breakdown of the initial gas, ramp-up of the plasma current to its final value and the control of plasma parameters during those phases. Tokamaks rely on an inductive component, typically a central solenoid, which has enabled attainment of high performance levels that has enabled the construction of the ITER device. Optimizing the inductive start-up phase continues to be an area of active research, especially in regards to achieving ITER scenarios. A new generation of superconducting tokamaks, EAST and KSTAR, experiments on DIII-D and operation with JET's ITER-like wall are contributing towards this effort. Inductive start-up relies on transformer action to generate a toroidal loop voltage and successful start-up is determined by gas breakdown, avalanche physics and plasma-wall interaction. The goal of achieving steady-sate tokamak operation has motivated interest in other methods for start-up that do not rely on the central solenoid. These include Coaxial Helicity Injection, outer poloidal field coil start-up, and point source helicity injection, which have achieved 200, 150 and 100 kA respectively of toroidal current on closed flux surfaces. Other methods including merging reconnection startup and Electron Bernstein Wave (EBW) plasma start-up are being studied on various devices. EBW start-up generates a directed electron channel due to wave particle interaction physics while the other methods mentioned rely on magnetic helicity injection and magnetic reconnection which are being modeled and understood using NIMROD code simulations.

  11. A power-balance model for local helicity injection startup in a spherical tokamak

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

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

    A 0D circuit model for predicting I p( t) in Local Helicity Injection (LHI) discharges is developed. Analytic formulas for estimating the surface flux of finite-A plasmas developed are modified and expanded to treat highly shaped, ultralow-A tokamak geometry using a database of representative equilibria. Model predictions are compared to sample LHI discharges in the A ~ 1 Pegasus spherical tokamak, and are found to agree within 15% of experimental I p( t). High performance LHI discharges are found to follow the Taylor relaxation current limit for approximately the first half of the current ramp, or I p ≲ 75more » kA. The second half of the current ramp follows a limit imposed by power-balance as plasmas expand from high- A to ultralow- A. Here, this shape evolution generates a significant drop in external plasma inductance, effectively using the plasma’s initially high inductance to drive the current ramp and provide > 70% of the current drive V-s. Projections using this model indicate the relative influences of higher helicity input rate and injector current on the attainable total plasma current.« less

  12. A power-balance model for local helicity injection startup in a spherical tokamak

    DOE PAGES

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

    2018-05-15

    A 0D circuit model for predicting I p( t) in Local Helicity Injection (LHI) discharges is developed. Analytic formulas for estimating the surface flux of finite-A plasmas developed are modified and expanded to treat highly shaped, ultralow-A tokamak geometry using a database of representative equilibria. Model predictions are compared to sample LHI discharges in the A ~ 1 Pegasus spherical tokamak, and are found to agree within 15% of experimental I p( t). High performance LHI discharges are found to follow the Taylor relaxation current limit for approximately the first half of the current ramp, or I p ≲ 75more » kA. The second half of the current ramp follows a limit imposed by power-balance as plasmas expand from high- A to ultralow- A. Here, this shape evolution generates a significant drop in external plasma inductance, effectively using the plasma’s initially high inductance to drive the current ramp and provide > 70% of the current drive V-s. Projections using this model indicate the relative influences of higher helicity input rate and injector current on the attainable total plasma current.« less

  13. The Efficiency of Delone Coverings of the Canonical Tilings T}(*(A_4)) -> T^*(A4) and T}(*(D_6)) -> T^*(D6)

    NASA Astrophysics Data System (ADS)

    Papadopolos, Zorka; Kasner, Gerald

    This chapter is devoted to the coverings of the two quasiperiodic canonical tilings T}(*(A_4)) -> T^*(A4) and T}(*(D_6)) equiv {cal T}(*(2F)) -> T^*(D6) T^*(2F), obtained by projection from the root lattices A4 and D6, respectively. In the first major part of this chapter, in Sect. 5.2, we shall introduce a Delone covering T}(*(A_4)}) -> C^sT^*(A4) of the 2-dimensional decagonal tiling T}(*(A_4)) -> T^*(A4). In the second major part of this chapter, Sect. 5.3, we summarize the results related to the Delone covering of the icosahedral tiling T}(*(D_6)) -> T^*(D6), T}(*(D_6)}) -> CT^*(D6) and determine the zero-, single-, and double- deckings and the resulting thickness of the covering. In the conclusions section, we give some suggestions as to how the definition of the Delone covering might be changed in order to reach some real (full) covering of the icosahedral tiling T}(*(D_6)) -> T^*(D6). In Section 5.2 the definition of the Delone covering is also changed in order to avoid an unnecessary large thickness of the covering.

  14. Analysis of the Zeeman effect on D α spectra on the EAST tokamak

    NASA Astrophysics Data System (ADS)

    Gao, Wei; Huang, Juan; Wu, Chengrui; Xu, Zong; Hou, Yumei; Jin, Zhao; Chen, Yingjie; Zhang, Pengfei; Zhang, Ling; Wu, Zhenwei; EAST Team

    2017-04-01

    Based on the passive spectroscopy, the {{{D}}}α atomic emission spectra in the boundary region of the plasma have been measured by a high resolution optical spectroscopic multichannel analysis (OSMA) system in EAST tokamak. The Zeeman splitting of the {{{D}}}α spectral lines has been observed. A fitting procedure by using a nonlinear least squares method was applied to fit and analyze all polarization π and +/- σ components of the {{{D}}}α atomic spectra to acquire the information of the local plasma. The spectral line shape was investigated according to emission spectra from different regions (e.g., low-field side and high-field side) along the viewing chords. Each polarization component was fitted and classified into three energy categories (the cold, warm, and hot components) based on different atomic production processes, in consistent with the transition energy distribution by calculating the gradient of the {{{D}}}α spectral profile. The emission position, magnetic field intensity, and flow velocity of a deuterium atom were also discussed in the context. Project supported by the National Natural Science Foundation of China (Grant Nos. 11275231 and 11575249) and the National Magnetic Confinement Fusion Energy Research Program of China (Grant No. 2015GB110005).

  15. H-Mode Behavior Induced by Modulated Toroidal Current on HT-7 and HT-6M Tokamak

    NASA Astrophysics Data System (ADS)

    Mao, J. S.; Luo, J. R.; Xu, Y. H.; Zhao, J. Y.; Zhang, X. M.; Li, J. G.; Zhang, X. M.; Gao, X.; Li, Y. D.; Jie, Y. X.; Wu, Z. W.; Hu, L. Q.; Liu, S. X.; Zhang, X. D.; Bao, Y.; Yang, K.; Wang, G. X.; Chen, L.; Shi, Y. J.; Qin, P. J.; Gu, X. M.; Cui, N. Z.; Fan, H. Y.; Chen, Y. F.; Xia, C. Y.; Ruan, H. L.; Tong, X. D.; Phillips, P. E.

    2001-10-01

    An improved Ohmic confinement phase (similar to H-mode) has been observed during Modulating Toroidal Current on the Hefei Tokamak-6M (HT-6M) and Hefei super-conducting Tokamak-7 (HT-7). This improved plasma confinement phase is characterized by: (a) an increase in ne and T_e(0); (b) reduced H_α radiation from the edge; (c) steeper density and temperature profiles at the edge; (d) a more negative radial electric field inside the limiter; (e) a deeper electrostatic potential well at the edge; (f) reduced magnetic fluctuations at the edge; (g) MHD suppressing; (h) and by an increase in global energy confinement time, τ _e, by 27%-45%. The well-like structure of the radial electric field E_r, appears at an L-H like transition.

  16. Time dependent 14 MeV neutrons measurement using a polycrystalline chemical vapor deposited diamond detector at the JET tokamak

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

    Angelone, M.; Pillon, M.; Bertalot, L.

    A polycrystalline chemical vapor deposited (CVD) diamond detector was installed on a JET tokamak in order to monitor the time dependent 14 MeV neutron emission produced by D-T plasma pulses during the Trace Tritium Experiment (TTE) performed in October 2003. This was the first tentative ever attempted to use a CVD diamond detector as neutron monitor in a tokamak environment. Despite its small active volume, the detector was able to detect the 14 MeV neutron emission (>1.0x10{sup 15} n/shot) with good reliability and stability during the experimental campaign that lasted five weeks. The comparison with standard silicon detectors presently usedmore » at JET as 14 MeV neutron monitors is reported, showing excellent correlation between the measurements. The results prove that CVD diamond detectors can be reliably used in a tokamak environment and therefore confirm the potential of this technology for next step machines like ITER.« less

  17. On extended analytic theory of 2D ballooning modes in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Abdoul, Peshwaz; Dickinson, David; Roach, Colin; Wilson, Howard

    2016-10-01

    We have extended the leading order ballooning theory which typically yields more unstable isolated mode (IM) that usually sit on the outboard mid-plane, to higher order where less unstable general mode (GM) sits at a different poloidal location. Our analytic theory has revealed that any poloidal shift of the mode with respect to the outboard mid-plane - arising from the effect of profile variations, for example - is always accompanied by an asymmetry of the radial eigenmode structure. Hence, GMs have radial asymmetry. Our theory can have important consequences, especially for calculations that invoke quasilinear theory to model intrinsic rotation arising from Reynolds stress. This is very important in ITER for which external torques are small. In such theories it is the radial asymmetry in the global GM mode which can generate a Reynolds stress that could in principle contribute to the poloidal flow during the low to high (L-H) mode transition in tokamaks. I am also an associate member at the York Plasma Institute, University of York and teaching at the Physics Department, University of Sulaimani, Kurdistan Region, Iraq.

  18. Experiments with lithium limiter on T-11M tokamak and applications of the lithium capillary-pore system in future fusion reactor devices

    NASA Astrophysics Data System (ADS)

    Mirnov, S. V.; Azizov, E. A.; Evtikhin, V. A.; Lazarev, V. B.; Lyublinski, I. E.; Vertkov, A. V.; Prokhorov, D. Yu

    2006-06-01

    The paper is an overview of recent results of Li limiter testing in T-11M tokamak. The lithium limiter is based on the capillary-pore system (CPS) concept. The Li erosion process and deuterium (D2) and helium (He) sorption by Li first wall were investigated. The ability of capillary forces to confine the liquid Li in the CPS limiter during disruption was demonstrated. The idea of combined lithium limiter with thin (0.6 mm) CPS coating as a solution of the heat removal problem was realized. As a result the quasi steady-state tokamak regime with duration up to 0.3 s and clean (Zeff = 1) deuterium plasma has been achieved. The temporal evolution of the lithium surface temperature during discharge was measured by a IR radiometer and then was recalculated to the surface power load. For the estimation of the Li limiter erosion the Li neutral and ions spectral line emission were observed. The increase in lithium erosion as a result of limiter heating was discovered. The radial distribution of plasma column radiation measurements showed up to 90% of the total radiation losses in a relatively thin (5 cm) boundary layer and only 10% in a plasma centre during discharges with high Li influx. Oscillations of Li emission and saw-tooth-like oscillations of the limiter surface temperature have been detected in discharge regimes with highest Li limiter temperature (>600 °C). A version of Li CPS first wall of DEMO reactor and Li CPS limiter experiment in the International Thermonuclear Energy Reactor are suggested.

  19. Alpha-driven magnetohydrodynamics (MHD) and MHD-induced alpha loss in the Tokamak Fusion Test Reactor

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

    Chang, Z.; Nazikian, R.; Fu, G.Y.

    1997-02-01

    Alpha-driven toroidal Alfven eigenmodes (TAEs) are observed as predicted by theory in the post neutral beam phase in high central q (safety factor) deuterium-tritium (D-T) plasmas in the Tokamak Fusion Test Reactor (TFTR). The mode location, poloidal structure and the importance of q profile for TAE instability are discussed. So far no alpha particle loss due to these modes was detected due to the small mode amplitude. However, alpha loss induced by kinetic ballooning modes (KBMs) was observed in high confinement D-T discharges. Particle orbit simulation demonstrates that the wave-particle resonant interaction can explain the observed correlation between the increasemore » in alpha loss and appearance of multiple high-n (n {ge} 6, n is the toroidal mode number) modes.« less

  20. Tokamak plasma high field side response to an n = 3 magnetic perturbation: a comparison of 3D equilibrium solutions from seven different codes

    NASA Astrophysics Data System (ADS)

    Reiman, A.; Ferraro, N. M.; Turnbull, A.; Park, J. K.; Cerfon, A.; Evans, T. E.; Lanctot, M. J.; Lazarus, E. A.; Liu, Y.; McFadden, G.; Monticello, D.; Suzuki, Y.

    2015-06-01

    In comparing equilibrium solutions for a DIII-D shot that is amenable to analysis by both stellarator and tokamak three-dimensional (3D) equilibrium codes, a significant disagreement has been seen between solutions of the VMEC stellarator equilibrium code and solutions of tokamak perturbative 3D equilibrium codes. The source of that disagreement has been investigated, and that investigation has led to new insights into the domain of validity of the different equilibrium calculations, and to a finding that the manner in which localized screening currents at low order rational surfaces are handled can affect global properties of the equilibrium solution. The perturbative treatment has been found to break down at surprisingly small perturbation amplitudes due to overlap of the calculated perturbed flux surfaces, and that treatment is not valid in the pedestal region of the DIII-D shot studied. The perturbative treatment is valid, however, further into the interior of the plasma, and flux surface overlap does not account for the disagreement investigated here. Calculated equilibrium solutions for simple model cases and comparison of the 3D equilibrium solutions with those of other codes indicate that the disagreement arises from a difference in handling of localized currents at low order rational surfaces, with such currents being absent in VMEC and present in the perturbative codes. The significant differences in the global equilibrium solutions associated with the presence or absence of very localized screening currents at rational surfaces suggests that it may be possible to extract information about localized currents from appropriate measurements of global equilibrium plasma properties. That would require improved diagnostic capability on the high field side of the tokamak plasma, a region difficult to access with diagnostics.

  1. Edge-localized-modes in tokamaks

    DOE PAGES

    Leonard, Anthony W.

    2014-09-11

    Edge-localized-modes (ELMs) are a ubiquitous feature of H-mode in tokamaks. When gradients in the H-mode transport barrier grow to exceed the MHD stability limit the ELM instability grows explosively rapidly transporting energy and particles onto open field lines and material surfaces. Though ELMs provide additional particle and impurity transport through the H-mode transport barrier, enabling steady operation, the resulting heat flux transients to plasma facing surfaces project to large amplitude in future low collisionality burning plasma tokamaks. Measurements of the ELM heat flux deposition onto material surfaces in the divertor and main chamber indicate significant broadening compared to inter-ELM heatmore » flux, with a timescale for energy deposition that is consistent with sonic ion flow and numerical simulation. Comprehensive ELM simulation is highlighting the important physics processes of ELM transport including parallel transport due to magnetic reconnection and turbulence resulting from collapse of the H-mode transport barrier. As a result, encouraging prospects for ELM control and/or suppression in future tokamaks include intrinsic modes of ELM free operation, ELM triggering with frequent small pellet injection and the application of 3D magnetic fields.« less

  2. Core tungsten radiation diagnostic calibration by small shell pellet injection in the DIII-D tokamak

    DOE PAGES

    Hollmann, Eric M.; Commaux, Nicolas; Shiraki, Daisuke; ...

    2017-10-04

    Injection of small (OD = 0.8 mm) plastic pellets carrying embedded smaller (10 μg) tungsten grains is used to check calibrations of core tungsten line radiation diagnostics in support of the 2016 tungsten rings campaign in the DIII-D tokamak. The total (1 eV – 10 keV) and soft x-ray (1 keV – 10 keV) brightnesses we observed were found to be reasonably well (< factor 2) predicted using existing calibration factors and rate calculations. Individual core (EUV/SXR) tungsten line brightnesses appear to be somewhat less reliable (factor 2-4) for prediction of core tungsten concentration.

  3. Core tungsten radiation diagnostic calibration by small shell pellet injection in the DIII-D tokamak

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

    Hollmann, Eric M.; Commaux, Nicolas; Shiraki, Daisuke

    Injection of small (OD = 0.8 mm) plastic pellets carrying embedded smaller (10 μg) tungsten grains is used to check calibrations of core tungsten line radiation diagnostics in support of the 2016 tungsten rings campaign in the DIII-D tokamak. The total (1 eV – 10 keV) and soft x-ray (1 keV – 10 keV) brightnesses we observed were found to be reasonably well (< factor 2) predicted using existing calibration factors and rate calculations. Individual core (EUV/SXR) tungsten line brightnesses appear to be somewhat less reliable (factor 2-4) for prediction of core tungsten concentration.

  4. Boundary perturbations coupled to core 3/2 tearing modes on the DIII-D tokamak

    NASA Astrophysics Data System (ADS)

    Tobias, B.; Yu, L.; Domier, C. W.; Luhmann, N. C., Jr.; Austin, M. E.; Paz-Soldan, C.; Turnbull, A. D.; Classen, I. G. J.; the DIII-D Team

    2013-09-01

    High confinement (H-mode) discharges on the DIII-D tokamak are routinely subject to the formation of long-lived, non-disruptive magnetic islands that degrade confinement and limit fusion performance. Simultaneous, 2D measurement of electron temperature fluctuations in the core and edge regions allows for reconstruction of the radially resolved poloidal mode number spectrum and phase of the global plasma response associated with these modes. Coherent, n = 2 excursions of the plasma boundary are found to be the result of coupling to an n = 2, kink-like mode which arises locked in phase to the 3/2 island chain. This coupling dictates the relative phase of the displacement at the boundary with respect to the tearing mode. This unambiguous phase relationship, for which no counter-examples are observed, is presented as a test for modeling of the perturbed fields to be expected outside the confined plasma.

  5. Full wave simulations of helicon wave losses in the scrape-off-layer of the DIII-D tokamak

    NASA Astrophysics Data System (ADS)

    Lau, Cornwall; Jaeger, Fred; Berry, Lee; Bertelli, Nicola; Pinsker, Robert

    2017-10-01

    Helicon waves have been recently proposed as an off-axis current drive actuator for DIII-D. Previous modeling using the hot plasma, full wave code AORSA, has shown good agreement with the ray tracing code GENRAY for helicon wave propagation and absorption in the core plasma. AORSA, and a new, reduced finite-element-model show discrepancies between ray tracing and full wave occur in the scrape-off-layer (SOL), especially at high densities. The reduced model is much faster than AORSA, and reproduces most of the important features of the AORSA model. The reduced model also allows for larger parametric scans and for the easy use of arbitrary tokamak geometry. Results of the full wave codes, AORSA and COMSOL, will be shown for helicon wave losses in the SOL are shown for a large range of parameters, such as SOL density profiles, n||, radial and vertical locations of the antenna, and different tokamak vessel geometries. This work was supported by DE-AC05-00OR22725, DE-AC02-09CH11466, and DE-FC02-04ER54698.

  6. Optimal Control Techniques for ResistiveWall Modes in Tokamaks

    NASA Astrophysics Data System (ADS)

    Clement, Mitchell Dobbs Pearson

    Tokamaks can excite kink modes that can lock or nearly lock to the vacuum vessel wall, and whose rotation frequencies and growth rates vary in time but are generally inversely proportional to the magnetic flux diffusion time of the vacuum vessel wall. This magnetohydrodynamic (MHD) instability is pressure limiting in tokamaks and is called the Resistive Wall Mode (RWM). Future tokamaks that are expected to operate as fusion reactors will be required to maximize plasma pressure in order to maximize fusion performance. The DIII-D tokamak is equipped with electromagnetic control coils, both inside and outside of its vacuum vessel, which create magnetic fields that are small by comparison to the machine's equilibrium field but are able to dynamically counteract the RWM. Presently for RWM feedback, DIII-D uses its interior control coils using a classical proportional gain only controller to achieve high plasma pressure. Future advanced tokamak designs will not likely have the luxury of interior control coils and a proportional gain algorithm is not expected to be effective with external control coils. The computer code VALEN was designed to calculate the performance of an MHD feedback control system in an arbitrary geometry. VALEN models the perturbed magnetic field from a single MHD instability and its interaction with surrounding conducting structures using a finite element approach. A linear quadratic gaussian (LQG) control, or H 2 optimal control, algorithm based on the VALEN model for RWM feedback was developed for use with DIII-D's external control coil set. The algorithm is implemented on a platform that combines a graphics processing unit (GPU) for real-time control computation with low latency digital input/output control hardware and operates in parallel with the DIII-D Plasma Control System (PCS). Simulations and experiments showed that modern control techniques performed better, using 77% less current, than classical techniques when using coils external to

  7. Protecting Against Damage from Refraction of High Power Microwaves in the DIII-D Tokamak

    NASA Astrophysics Data System (ADS)

    Lohr, John; Brambila, Rigo; Cengher, Mirela; Chen, Xi; Gorelov, Yuri; Grosnickle, William; Moeller, Charles; Ponce, Dan; Prater, Ron; Torrezan, Antonio; Austin, Max; Doyle, Edward; Hu, Xing; Dormier, Calvin

    2017-07-01

    Several new protective systems are being installed on the DIII D tokamak to increase the safety margins for plasma operations with injected ECH power at densities approaching cutoff. Inadvertent overdense operation has previously resulted in reflection of an rf beam back into a launcher causing extensive arcing and melt damage on one waveguide line. Damage to microwave diagnostics, which are located on the same side of the tokamak as the ECH launchers, also has occurred. Developing a reliable microwave based interlock to protect the many vulnerable systems in DIII-D has proved to be difficult. Therefore, multiple protective steps have been taken to reduce the risk of damage in the future. Among these is a density interlock generated by the plasma control system, with setpoint determined by the ECH operators based on rf beam trajectories and plasma parameters. Also installed are enhanced video monitoring of the launchers, and an ambient light monitor on each of the waveguide systems, along with a Langmuir probe at the mouth of each launcher. Versatile rf monitors, measuring forward and reflected power in addition to the mode content of the rf beams, have been installed as the last miter bends in each waveguide line. As these systems are characterized, they are being incorporated in the interlock chains, which enable the ECH injection permits. The diagnostics most susceptible to damage from the ECH waves have also been fitted with a variety of protective devices including stripline filters, thin resonant notch filters tuned to the 110 GHz injected microwave frequency, blazed grating filters and shutters. Calculations of rf beam trajectories in the plasmas are performed using the TORAY ray tracing code with input from kinetic profile diagnostics. Using these calculations, strike points for refracted beams on the vacuum vessel are calculated, which allows evaluation of the risk of damage to sensitive diagnostics and hardware.

  8. Multi-field plasma sandpile model in tokamaks and applications

    NASA Astrophysics Data System (ADS)

    Peng, X. D.; Xu, J. Q.

    2016-08-01

    A multi-field sandpile model of tokamak plasmas is formulated for the first time to simulate the dynamic process with interaction between avalanche events on the fast/micro time-scale and diffusive transports on the slow/macro time-scale. The main characteristics of the model are that both particle and energy avalanches of sand grains are taken into account simultaneously. New redistribution rules of a sand-relaxing process are defined according to the transport properties of special turbulence which allows the uphill particle transport. Applying the model, we first simulate the steady-state plasma profile self-sustained by drift wave turbulences in the Ohmic discharge of a tokamak. A scaling law as f = a q0 b + c for the relation of both center-density n ( 0 ) and electron (ion) temperatures T e ( 0 ) ( T i ( 0 ) ) with the center-safety-factor q 0 is found. Then interesting work about the nonlocal transport phenomenon observed in tokamak experiments proceeds. It is found that the core electron temperature increases rapidly in response to the edge cold pulse and inversely it decreases in response to the edge heat pulse. The results show that the nonlocal response of core electron temperature depending on the amplitudes of background plasma density and temperature is more remarkable in a range of gas injection rate. Analyses indicate that the avalanche transport caused by plasma drift instabilities with thresholds is a possible physical mechanism for the nonlocal transport in tokamaks. It is believed that the model is capable of being applied to more extensive questions occurring in the transport field.

  9. A review of radiative detachment studies in tokamak advanced magnetic divertor configurations

    DOE PAGES

    Soukhanovskii, V. A.

    2017-04-28

    The present vision for a plasma–material interface in the tokamak is an axisymmetric poloidal magnetic X-point divertor. Four tasks are accomplished by the standard poloidal X-point divertor: plasma power exhaust; particle control (D/T and He pumping); reduction of impurity production (source); and impurity screening by the divertor scrape-off layer. A low-temperature, low heat flux divertor operating regime called radiative detachment is viewed as the main option that addresses these tasks for present and future tokamaks. Advanced magnetic divertor configuration has the capability to modify divertor parallel and cross-field transport, radiative and dissipative losses, and detachment front stability. Advanced magnetic divertormore » configurations are divided into four categories based on their salient qualitative features: (1) multiple standard X-point divertors; (2) divertors with higher order nulls; (3) divertors with multiple X-points; and (4) long poloidal leg divertors (and also with multiple X-points). As a result, this paper reviews experiments and modeling in the area of radiative detachment in the advanced magnetic divertor configurations.« less

  10. A review of radiative detachment studies in tokamak advanced magnetic divertor configurations

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

    Soukhanovskii, V. A.

    The present vision for a plasma–material interface in the tokamak is an axisymmetric poloidal magnetic X-point divertor. Four tasks are accomplished by the standard poloidal X-point divertor: plasma power exhaust; particle control (D/T and He pumping); reduction of impurity production (source); and impurity screening by the divertor scrape-off layer. A low-temperature, low heat flux divertor operating regime called radiative detachment is viewed as the main option that addresses these tasks for present and future tokamaks. Advanced magnetic divertor configuration has the capability to modify divertor parallel and cross-field transport, radiative and dissipative losses, and detachment front stability. Advanced magnetic divertormore » configurations are divided into four categories based on their salient qualitative features: (1) multiple standard X-point divertors; (2) divertors with higher order nulls; (3) divertors with multiple X-points; and (4) long poloidal leg divertors (and also with multiple X-points). As a result, this paper reviews experiments and modeling in the area of radiative detachment in the advanced magnetic divertor configurations.« less

  11. The Design and Use of Tungsten Coated TZM Molybdenum Tile Inserts in the DIII-D Tokamak Divertor

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

    Murphy, Christopher; Nygren, R. E.; Chrobak, C P.

    Future tokamak devices are envisioned to utilize a high-Z metal divertor with tungsten as theleading candidate. However, tokamak experiments with tungsten divertors have seen significantdetrimental effects on plasma performance. The DIII-D tokamak presently has carbon as theplasma facing surface but to study the effect of tungsten on the plasma and its migration aroundthe vessel, two toroidal rows of carbon tiles in the divertor region were modified with high-Zmetal inserts, composed of a molybdenum alloy (TZM) coated with tungsten. A dedicated twoweek experimental campaign was run with the high-Z metal inserts. One row was coated withtungsten containing naturally occurring levels ofmore » isotopes. The second row was coated withtungsten where the isotope 182W was enhanced from the natural level of 26% up to greater than90%. The different isotopic concentrations enabled the experiment to differentiate between thetwo different sources of metal migration from the divertor. Various coating methods wereexplored for the deposition of the tungsten coating, including chemical vapor deposition,electroplating, vacuum plasma spray, and electron beam physical vapor deposition. The coatingswere tested to see if they were robust enough to act as a divertor target for the experiment. Testsincluded cyclic thermal heating using a high power laser and high-fluence deuterium plasmabombardment. The issues associate with the design of the inserts (tile installation, thermal stress,arcing, leading edges, surface preparation, etc.), are reviewed. The results of the tests used toselect the coating method and preliminary experimental observations are presented.« less

  12. Status of the tokamak program

    NASA Astrophysics Data System (ADS)

    Sheffield, J.

    1981-08-01

    For a specific configuration of magnetic field and plasma to be economically attractive as a commercial source of energy, it must contain a high-pressure plasma in a stable fashion while thermally isolating the plasma from the walls of the containment vessel. The tokamak magnetic configuration is presently the most successful in terms of reaching the considered goals. Tokamaks were developed in the USSR in a program initiated in the mid-1950s. By the early 1970s tokamaks were operating not only in the USSR but also in the U.S., Australia, Europe, and Japan. The advanced state of the tokamak program is indicated by the fact that it is used as a testbed for generic fusion development - for auxiliary heating, diagnostics, materials - as well as for specific tokamak advancement. This has occurred because it is the most economic source of a large, reproducible, hot, dense plasma. The basic tokamak is considered along with tokamak improvements, impurity control, additional heating, particle and power balance in a tokamak, aspects of microscopic transport, and macroscopic stability.

  13. Measurement and simulation of passive fast-ion D-alpha emission from the DIII-D tokamak

    DOE PAGES

    Bolte, Nathan G.; Heidbrink, William W.; Pace, David; ...

    2016-09-14

    Spectra of passive fast-ion D-alpha (FIDA) light from beam ions that charge exchange with background neutrals are measured and simulated. The fast ions come from three sources: ions that pass through the diagnostic sightlines on their first full orbit, an axisymmetric confined population, and ions that are expelled into the edge region by instabilities. A passive FIDA simulation (P-FIDASIM) is developed as a forward model for the spectra of the first-orbit fast ions and consists of an experimentally-validated beam deposition model, an ion orbit-following code, a collisional-radiative model, and a synthetic spectrometer. Model validation consists of the simulation of 86more » experimental spectra that are obtained using 6 different neutral beam fast-ion sources and 13 different lines of sight. Calibrated spectra are used to estimate the neutral density throughout the cross-section of the tokamak. The resulting 2D neutral density shows the expected increase toward each X-point with average neutral densities of 8 X 10 9 cm -3 at the plasma boundary and 1 X 10 11 cm -3 near the wall. Here, fast ions that are on passing orbits are expelled by the sawtooth instability more readily than trapped ions. In a sample discharge, approximately 1% of the fast-ion population is ejected into the high neutral density region per sawtooth crash.« less

  14. Interaction of external n = 1 magnetic fields with the sawtooth instability in low- q RFX-mod and DIII-D tokamaks

    DOE PAGES

    Piron, C.; Martin, P.; Bonfiglio, D.; ...

    2016-08-11

    External n = 1 magnetic fields are applied in RFX-mod and DIII-D low safety factor Tokamak plasmas to investigate their interaction with the internal MHD dynamics and in particular with the sawtooth instability. In these experiments the applied magnetic fields cause a reduction of both the sawtooth amplitude and period, leading to an overall stabilizing effect on the oscillations. In RFX-mod sawteeth eventually disappear and are replaced by a stationary m = 1, n = 1 helical equilibrium without an increase in disruptivity. However toroidal rotation is significantly reduced in these plasmas, thus it is likely that the sawtooth mitigationmore » in these experiments is due to the combination of the helically deformed core and the reduced rotation. The former effect is qualitatively well reproduced by nonlinear MHD simulations performed with the PIXIE3D code. The results obtained in these RFX-mod experiments motivated similar ones in DIII-D L-mode diverted Tokamak plasmas at low q 95. These experiments succeeded in reproducing the sawtooth mitigation with the approach developed in RFX-mod. In DIII-D this effect is correlated with a clear increase of the n = 1 plasma response, that indicates an enhancement of the coupling to the marginally stable n = 1 external kink, as simulations with the linear MHD code IPEC suggest. A significant rotation braking in the plasma core is also observed in DIII-D. Finally, numerical calculations of the neoclassical toroidal viscosity (NTV) carried out with PENT identify this torque as a possible contributor for this effect.« less

  15. Design of set-point weighting PI{sup λ} + D{sup μ} controller for vertical magnetic flux controller in Damavand tokamak

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

    Rasouli, H.; Fatehi, A.

    2014-12-15

    In this paper, a simple method is presented for tuning weighted PI{sup λ} + D{sup μ} controller parameters based on the pole placement controller of pseudo-second-order fractional systems. One of the advantages of this controller is capability of reducing the disturbance effects and improving response to input, simultaneously. In the following sections, the performance of this controller is evaluated experimentally to control the vertical magnetic flux in Damavand tokamak. For this work, at first a fractional order model is identified using output-error technique in time domain. For various practical experiments, having desired time responses for magnetic flux in Damavand tokamak,more » is vital. To approach this, at first the desired closed loop reference models are obtained based on generalized characteristic ratio assignment method in fractional order systems. After that, for the identified model, a set-point weighting PI{sup λ} + D{sup μ} controller is designed and simulated. Finally, this controller is implemented on digital signal processor control system of the plant to fast/slow control of magnetic flux. The practical results show appropriate performance of this controller.« less

  16. Measurement of H/D ratio and ion temperature on a HT-6M Tokamak

    NASA Astrophysics Data System (ADS)

    Wei, Lehan; Lin, Xiaodong

    1997-01-01

    By combining optical fibers with piezoelectric scanning Fabry-Perot interferometer, the profiles of Hα and Dα have been determined simultaneously in a single Tokamak discharge. Consequently, the ratio of hydrogen to deuterium and ion temperature are obtained. Not only is the uncertainty of shot-to-shot avoided, the results of the experiment indicate that this instrumentation has the advantage of rapid wavelength scanning, large dispersion, high resolution, and good adaptability of working in adverse circumstances such as at a Tokamak site.

  17. Simulations of Turbulence in Tokamak Edge and Effects of Self-Consistent Zonal Flows

    NASA Astrophysics Data System (ADS)

    Cohen, Bruce; Umansky, Maxim

    2013-10-01

    Progress is reported on simulations of electromagnetic drift-resistive ballooning turbulence in the tokamak edge. This extends previous work to include self-consistent zonal flows and their effects. The previous work addressed simulation of L-mode tokamak edge turbulence using the turbulence code BOUT that solves Braginskii-based plasma fluid equations in tokamak edge domain. The calculations use realistic single-null geometry and plasma parameters of the DIII-D tokamak and produce fluctuation amplitudes, fluctuation spectra, and particle and thermal fluxes that compare favorably to experimental data. In the effect of sheared ExB poloidal rotation is included with an imposed static radial electric field fitted to experimental data. In the new work here we include the radial electric field self-consistently driven by the microturbulence, which contributes to the sheared ExB poloidal rotation (zonal flow generation). We present simulations with/without zonal flows for both cylindrical geometry, as in the UCLA Large Plasma Device, and for the DIII-D tokamak L-mode cases in to quantify the influence of self-consistent zonal flows on the microturbulence and the concomitant transport. This work was performed under the auspices of the U.S. Department of Energy under contract DE-AC52-07NA27344 at the Lawrence Livermore National Laboratory.

  18. Enhancing the Production of D-Mannitol by an Artificial Mutant of Penicillium sp. T2-M10.

    PubMed

    Duan, Rongting; Li, Hongtao; Li, Hongyu; Tang, Linhuan; Zhou, Hao; Yang, Xueqiong; Yang, Yabin; Ding, Zhongtao

    2018-05-26

    D-Mannitol belongs to a linear polyol with six-carbon and has indispensable usage in medicine and industry. In order to obtain more efficient D-mannitol producer, this study has screened out a stable mutant Penicillium sp. T2-M10 that was isolated from the initial D-mannitol-produced strain Penicillium sp.T2-8 via UV irradiation as well as nitrosoguanidine (NTG) induction. The mutant had a considerable enhancement in yield of D-mannitol based on optimizing fermentation. The production condition was optimized as the PDB medium with 24 g/L glucose for 9 days. The results showed that the production of D-mannitol from the mutant strain T2-M10 increased 125% in contrast with the parental strain. Meanwhile, the fact that D-mannitol is the main product in the mutant simplified the process of purification. Our finding revealed the potential value of the mutant strain Penicillium sp. T2-M10 to be a D-mannitol-producing strain.

  19. 237Np absolute delayed neutron yield measurements

    NASA Astrophysics Data System (ADS)

    Doré, D.; Ledoux, X.; Nolte, R.; Gagnon-Moisan, F.; Thulliez, L.; Litaize, O.; Roettger, S.; Serot, O.

    2017-09-01

    237Np absolute delayed neutron yields have been measured at different incident neutron energies from 1.5 to 16 MeV. The experiment was performed at the Physikalisch-Technische Bundesanstalt (PTB) facility where the Van de Graaff accelerator and the cyclotron CV28 delivered 9 different neutron energy beams using p+T, d+D and d+T reactions. The detection system is made up of twelve 3He tubes inserted into a polyethylene cylinder. In this paper, the experimental setup and the data analysis method are described. The evolution of the absolute DN yields as a function of the neutron incident beam energies are presented and compared to experimental data found in the literature and data from the libraries.

  20. Simulations of Tokamak Edge Turbulence Including Self-Consistent Zonal Flows

    NASA Astrophysics Data System (ADS)

    Cohen, Bruce; Umansky, Maxim

    2013-10-01

    Progress on simulations of electromagnetic drift-resistive ballooning turbulence in the tokamak edge is summarized in this mini-conference talk. A more detailed report on this work is presented in a poster at this conference. This work extends our previous work to include self-consistent zonal flows and their effects. The previous work addressed the simulation of L-mode tokamak edge turbulence using the turbulence code BOUT. The calculations used realistic single-null geometry and plasma parameters of the DIII-D tokamak and produced fluctuation amplitudes, fluctuation spectra, and particle and thermal fluxes that compare favorably to experimental data. In the effect of sheared ExB poloidal rotation is included with an imposed static radial electric field fitted to experimental data. In the new work here we include the radial electric field self-consistently driven by the microturbulence, which contributes to the sheared ExB poloidal rotation (zonal flow generation). We present simulations with/without zonal flows for both cylindrical geometry, as in the UCLA Large Plasma Device, and for the DIII-D tokamak L-mode cases in to quantify the influence of self-consistent zonal flows on the microturbulence and the concomitant transport. This work was performed under the auspices of the US Department of Energy under contract DE-AC52-07NA27344 at the Lawrence Livermore National Laboratory.

  1. A quartz nanopillar hemocytometer for high-yield separation and counting of CD4+ T lymphocytes

    NASA Astrophysics Data System (ADS)

    Kim, Dong-Joo; Seol, Jin-Kyeong; Wu, Yu; Ji, Seungmuk; Kim, Gil-Sung; Hyung, Jung-Hwan; Lee, Seung-Yong; Lim, Hyuneui; Fan, Rong; Lee, Sang-Kwon

    2012-03-01

    We report the development of a novel quartz nanopillar (QNP) array cell separation system capable of selectively capturing and isolating a single cell population including primary CD4+ T lymphocytes from the whole pool of splenocytes. Integrated with a photolithographically patterned hemocytometer structure, the streptavidin (STR)-functionalized-QNP (STR-QNP) arrays allow for direct quantitation of captured cells using high content imaging. This technology exhibits an excellent separation yield (efficiency) of ~95.3 +/- 1.1% for the CD4+ T lymphocytes from the mouse splenocyte suspensions and good linear response for quantitating captured CD4+ T-lymphoblasts, which is comparable to flow cytometry and outperforms any non-nanostructured surface capture techniques, i.e. cell panning. This nanopillar hemocytometer represents a simple, yet efficient cell capture and counting technology and may find immediate applications for diagnosis and immune monitoring in the point-of-care setting.We report the development of a novel quartz nanopillar (QNP) array cell separation system capable of selectively capturing and isolating a single cell population including primary CD4+ T lymphocytes from the whole pool of splenocytes. Integrated with a photolithographically patterned hemocytometer structure, the streptavidin (STR)-functionalized-QNP (STR-QNP) arrays allow for direct quantitation of captured cells using high content imaging. This technology exhibits an excellent separation yield (efficiency) of ~95.3 +/- 1.1% for the CD4+ T lymphocytes from the mouse splenocyte suspensions and good linear response for quantitating captured CD4+ T-lymphoblasts, which is comparable to flow cytometry and outperforms any non-nanostructured surface capture techniques, i.e. cell panning. This nanopillar hemocytometer represents a simple, yet efficient cell capture and counting technology and may find immediate applications for diagnosis and immune monitoring in the point-of-care setting

  2. AE3D

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

    Spong, Donald A

    AE3D solves for the shear Alfven eigenmodes and eigenfrequencies in a torodal magnetic fusion confinement device. The configuration can be either 2D (e.g. tokamak, reversed field pinch) or 3D (e.g. stellarator, helical reversed field pinch, tokamak with ripple). The equations solved are based on a reduced MHD model and sound wave coupling effects are not currently included.

  3. 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.

  4. Numerical optimization of perturbative coils for tokamaks

    NASA Astrophysics Data System (ADS)

    Lazerson, Samuel; Park, Jong-Kyu; Logan, Nikolas; Boozer, Allen; NSTX-U Research Team

    2014-10-01

    Numerical optimization of coils which apply three dimensional (3D) perturbative fields to tokamaks is presented. The application of perturbative 3D magnetic fields in tokamaks is now commonplace for control of error fields, resistive wall modes, resonant field drive, and neoclassical toroidal viscosity (NTV) torques. The design of such systems has focused on control of toroidal mode number, with coil shapes based on simple window-pane designs. In this work, a numerical optimization suite based on the STELLOPT 3D equilibrium optimization code is presented. The new code, IPECOPT, replaces the VMEC equilibrium code with the IPEC perturbed equilibrium code, and targets NTV torque by coupling to the PENT code. Fixed boundary optimizations of the 3D fields for the NSTX-U experiment are underway. Initial results suggest NTV torques can be driven by normal field spectrums which are not pitch-resonant with the magnetic field lines. Work has focused on driving core torque with n = 1 and edge torques with n = 3 fields. Optimizations of the coil currents for the planned NSTX-U NCC coils highlight the code's free boundary capability. This manuscript has been authored by Princeton University under Contract Number DE-AC02-09CH11466 with the U.S. Department of Energy.

  5. Arguments for fundamental emission by the parametric process L yields T + S in interplanetary type III bursts. [langmuir, electromagnetic, ion acoustic waves (L, T, S)

    NASA Technical Reports Server (NTRS)

    Cairns, I. H.

    1984-01-01

    Observations of low frequency ion acoustic-like waves associated with Langmuir waves present during interplanetary Type 3 bursts are used to study plasma emission mechanisms and wave processes involving ion acoustic waves. It is shown that the observed wave frequency characteristics are consistent with the processes L yields T + S (where L = Langmuir waves, T = electromagnetic waves, S = ion acoustic waves) and L yields L' + S proceeding. The usual incoherent (random phase) version of the process L yields T + S cannot explain the observed wave production time scale. The clumpy nature of the observed Langmuir waves is vital to the theory of IP Type 3 bursts. The incoherent process L yields T + S may encounter difficulties explaining the observed Type 3 brightness temperatures when Langmuir wave clumps are incorporated into the theory. The parametric process L yields T + S may be the important emission process for the fundamental radiation of interplanetary Type 3 bursts.

  6. High spatial resolution upgrade of the electron cyclotron emission radiometer for the DIII-D tokamak

    DOE PAGES

    Truong, D. D.; Austin, M. E.

    2014-11-01

    The 40-channel DIII-D electron cyclotron emission (ECE) radiometer provides measurements of Te(r,t) at the tokamak midplane from optically thick, second harmonic X-mode emission over a frequency range of 83-130 GHz. Heterodyning divides this frequency range into three 2-18 GHz intermediate frequency (IF) bands. The frequency spacing of the radiometer’s channels results in a spatial resolution of ~1-3 cm, depending on local magnetic field and electron temperature. A new high resolution subsystem has been added to the DIII-D ECE radiometer to make sub-centimeter (0.6-0.8 cm) resolution Te measurements. The high resolution subsystem branches off from the regular channels’ IF bands andmore » consists of a microwave switch to toggle between IF bands, a switched filter bank for frequency selectivity, an adjustable local oscillator and mixer for further frequency down-conversion, and a set of eight microwave filters in the 2-4 GHz range. We achieved a higher spatial resolution through the use of a narrower (200 MHz) filter bandwidth and closer spacing between the filters’ center frequencies (250 MHz). This configuration allows for full coverage of the 83-130 GHz frequency range in 2 GHz bands. Depending on the local magnetic field, this translates into a “zoomed-in” analysis of a ~2-4 cm radial region. These high resolution channels will be most useful in the low-field side edge region where modest Te values (1-2 keV) result in a minimum of relativistic broadening. Some expected uses of these channels include mapping the spatial dependence of Alfven eigenmodes, geodesic acoustic modes, and externally applied magnetic perturbations. Initial Te measurements, which demonstrate that the desired resolution is achieved, is presented.« less

  7. Modelling ion cyclotron emission from KSTAR tokamak and LHD helical device plasmas

    NASA Astrophysics Data System (ADS)

    Dendy, Richard; Chapman, Ben; Reman, Bernard; Chapman, Sandra; Akiyama, Tsuyoshi; Yun, Gunsu

    2017-10-01

    New high quality measurements of ion cyclotron emission (ICE) from KSTAR and LHD greatly extend the scope and diversity of plasma conditions under which ICE is observed. Variables include the origin (fusion reactions or neutral beam injection) and energy (sub- or super-Alfvénic) of the minority energetic ions that drive ICE; the composition of the bulk plasma (hydrogen or deuterium) which supports the modes excited; plasma density in the emitting region, and the timescale on which it changes; and toroidal magnetic field geometry (tokamak or helical device). Future exploitation of ICE as a diagnostic for energetic ion populations in JET D-T plasmas and in ITER rests on quantitative understanding of the physics of the emission. This is tested and extended by current KSTAR and LHD measurements of ICE. We report progress on direct numerical simulation using full orbit ion kinetic codes that solve the Maxwell-Lorentz equations for hundreds of millions of particles. In the saturated regime, these simulations yield excited field spectra that correspond directly to the measured ICE spectra under diverse KSTAR and LHD regimes. At early times, comparison of simulation outputs with linear analytical theory confirms the magnetoacoustic cyclotron instability as the basic driver of ICE. Supported by RCUK Energy Programme Grant EP/P012450/1, NRF Korea Grant 2014M1A7A1A03029881, NIFS budget ULHH029 and Euratom.

  8. Electron cyclotron emission from nonthermal tokamak plasmas

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

    Harvey, R.W.; O'Brien, M.R.; Rozhdestvensky, V.V.

    1993-02-01

    Electron cyclotron emission can be a sensitive indicator of nonthermal electron distributions. A new, comprehensive ray-tracing and cyclotron emission code that is aimed at predicting and interpreting the cyclotron emission from tokamak plasmas is described. The radiation transfer equation is solved along Wentzel--Kramers--Brillouin (WKB) rays using a fully relativistic calculation of the emission and absorption from electron distributions that are gyrotropic and toroidally symmetric, but may be otherwise arbitrary functions of the constants of motion. Using a radial array of electron distributions obtained from a bounce-averaged Fokker--Planck code modeling dc electron field and electron cyclotron heating effects, the cyclotron emissionmore » spectra are obtained. A pronounced strong nonthermal cyclotron emission feature that occurs at frequencies relativistically downshifted to second harmonic cyclotron frequencies outside the tokamak is calculated, in agreement with experimental results from the DIII-D [J. L. Luxon and L. G. Davies, Fusion Technol. [bold 8], 441 (1985)] and FT-1 [D. G. Bulyginsky [ital et] [ital al]., in [ital Proceedings] [ital of] [ital the] 15[ital th] [ital European] [ital Conference] [ital on] [ital Controlled] [ital Fusion] [ital and] [ital Plasma] [ital Heating], Dubrovnik, 1988 (European Physical Society, Petit-Lancy, 1988), Vol. 12B, Part II, p. 823] tokamaks. The calculations indicate the presence of a strong loss mechanism that operates on electrons in the 100--150 keV energy range.« less

  9. Protecting against damage from refraction of high power microwaves in the DIII-D tokamak

    DOE PAGES

    Lohr, John; Brambila, Rigo; Cengher, Mirela; ...

    2017-07-24

    Here, several new protective systems are being installed on the DIII D tokamak to increase the safety margins for plasma operations with injected ECH power at densities approaching cutoff. Inadvertent overdense operation has previously resulted in reflection of an rf beam back into a launcher causing extensive arcing and melt damage on one waveguide line. Damage to microwave diagnostics, which are located on the same side of the tokamak as the ECH launchers, also has occurred. Developing a reliable microwave based interlock to protect the many vulnerable systems in DIII-D has proved to be difficult. Therefore, multiple protective steps havemore » been taken to reduce the risk of damage in the future. Among these is a density interlock generated by the plasma control system, with setpoint determined by the ECH operators based on rf beam trajectories and plasma parameters. Also installed are enhanced video monitoring of the launchers, and an ambient light monitor on each of the waveguide systems, along with a Langmuir probe at the mouth of each launcher. Versatile rf monitors, measuring forward and reflected power in addition to the mode content of the rf beams, have been installed as the last miter bends in each waveguide line. As these systems are characterized, they are being incorporated in the interlock chains, which enable the ECH injection permits. The diagnostics most susceptible to damage from the ECH waves have also been fitted with a variety of protective devices including stripline filters, thin resonant notch filters tuned to the 110 GHz injected microwave frequency, blazed grating filters and shutters. Calculations of rf beam trajectories in the plasmas are performed using the TORAY ray tracing code with input from kinetic profile diagnostics. Using these calculations, strike points for refracted beams on the vacuum vessel are calculated, which allows evaluation of the risk of damage to sensitive diagnostics and hardware.« less

  10. Protecting against damage from refraction of high power microwaves in the DIII-D tokamak

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

    Lohr, John; Brambila, Rigo; Cengher, Mirela

    Here, several new protective systems are being installed on the DIII D tokamak to increase the safety margins for plasma operations with injected ECH power at densities approaching cutoff. Inadvertent overdense operation has previously resulted in reflection of an rf beam back into a launcher causing extensive arcing and melt damage on one waveguide line. Damage to microwave diagnostics, which are located on the same side of the tokamak as the ECH launchers, also has occurred. Developing a reliable microwave based interlock to protect the many vulnerable systems in DIII-D has proved to be difficult. Therefore, multiple protective steps havemore » been taken to reduce the risk of damage in the future. Among these is a density interlock generated by the plasma control system, with setpoint determined by the ECH operators based on rf beam trajectories and plasma parameters. Also installed are enhanced video monitoring of the launchers, and an ambient light monitor on each of the waveguide systems, along with a Langmuir probe at the mouth of each launcher. Versatile rf monitors, measuring forward and reflected power in addition to the mode content of the rf beams, have been installed as the last miter bends in each waveguide line. As these systems are characterized, they are being incorporated in the interlock chains, which enable the ECH injection permits. The diagnostics most susceptible to damage from the ECH waves have also been fitted with a variety of protective devices including stripline filters, thin resonant notch filters tuned to the 110 GHz injected microwave frequency, blazed grating filters and shutters. Calculations of rf beam trajectories in the plasmas are performed using the TORAY ray tracing code with input from kinetic profile diagnostics. Using these calculations, strike points for refracted beams on the vacuum vessel are calculated, which allows evaluation of the risk of damage to sensitive diagnostics and hardware.« less

  11. Design of the 2D electron cyclotron emission imaging instrument for the J-TEXT tokamak.

    PubMed

    Pan, X M; Yang, Z J; Ma, X D; Zhu, Y L; Luhmann, N C; Domier, C W; Ruan, B W; Zhuang, G

    2016-11-01

    A new 2D Electron Cyclotron Emission Imaging (ECEI) diagnostic is being developed for the J-TEXT tokamak. It will provide the 2D electron temperature information with high spatial, temporal, and temperature resolution. The new ECEI instrument is being designed to support fundamental physics investigations on J-TEXT including MHD, disruption prediction, and energy transport. The diagnostic contains two dual dipole antenna arrays corresponding to F band (90-140 GHz) and W band (75-110 GHz), respectively, and comprises a total of 256 channels. The system can observe the same magnetic surface at both the high field side and low field side simultaneously. An advanced optical system has been designed which permits the two arrays to focus on a wide continuous region or two radially separate regions with high imaging spatial resolution. It also incorporates excellent field curvature correction with field curvature adjustment lenses. An overview of the diagnostic and the technical progress including the new remote control technique are presented.

  12. Design of the 2D electron cyclotron emission imaging instrument for the J-TEXT tokamak

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

    Pan, X. M.; Yang, Z. J., E-mail: yangzj@hust.edu.cn; Ma, X. D.

    2016-11-15

    A new 2D Electron Cyclotron Emission Imaging (ECEI) diagnostic is being developed for the J-TEXT tokamak. It will provide the 2D electron temperature information with high spatial, temporal, and temperature resolution. The new ECEI instrument is being designed to support fundamental physics investigations on J-TEXT including MHD, disruption prediction, and energy transport. The diagnostic contains two dual dipole antenna arrays corresponding to F band (90-140 GHz) and W band (75-110 GHz), respectively, and comprises a total of 256 channels. The system can observe the same magnetic surface at both the high field side and low field side simultaneously. An advancedmore » optical system has been designed which permits the two arrays to focus on a wide continuous region or two radially separate regions with high imaging spatial resolution. It also incorporates excellent field curvature correction with field curvature adjustment lenses. An overview of the diagnostic and the technical progress including the new remote control technique are presented.« less

  13. Developing snowflake divertor physics basis in the DIII-D, NSTX and NSTX-U tokamaks aimed at the divertor power exhaust solution [Snowflake divertor experiments in the DIII-D, NSTX and NSTX-U tokamaks aimed at the development of the divertor power exhaust solution

    DOE PAGES

    Soukhanovskii, V. A.; Allen, S. L.; Fenstermacher, M. E.; ...

    2016-06-02

    Experimental results from the National Spherical Torus Experiment (NSTX), a medium-size spherical tokamak with a compact divertor, and DIII-D, a large conventional aspect ratio tokamak, demonstrate that the snowflake (SF) divertor configuration may provide a promising solution for mitigating divertor heat loads and target plate erosion compatible with core H-mode confinement in future fusion devices, where the standard radiative divertor solution may be inadequate. In NSTX, where the initial high-power SF experiment were performed, the SF divertor was compatible with H-mode confinement, and led to the destabilization of large ELMs. However, a stable partial detachment of the outer strike pointmore » was also achieved where inter-ELM peak heat flux was reduced by factors 3-5, and peak ELM heat flux was reduced by up to 80% (cf. standard divertor). The DIII-D studies show the SF divertor enables significant power spreading in attached and radiative divertor conditions. Results include: compatibility with the core and pedestal, peak inter-ELM divertor heat flux reduction due to geometry at lower n e, and ELM energy and divertor peak heat flux reduction, especially prominent in radiative D 2-seeded SF divertor, and nearly complete power detachment and broader radiated power distribution in the radiative D 2-seeded SF divertor at P SOL = 3 - 4 MW. A variety of SF configurations can be supported by the divertor coil set in NSTX Upgrade. Edge transport modeling with the multi-fluid edge transport code UEDGE shows that the radiative SF divertor can successfully reduce peak divertor heat flux for the projected P SOL ≃9 MW case. In conclusion, the radiative SF divertor with carbon impurity provides a wider n e operating window, 50% less argon is needed in the impurity-seeded SF configuration to achieve similar q peak reduction factors (cf. standard divertor).« less

  14. Evidence from d+Au measurements for final-state suppression of high-p(T) hadrons in Au+Au collisions at RHIC.

    PubMed

    Adams, J; Adler, C; Aggarwal, M M; Ahammed, Z; Amonett, J; Anderson, B D; Anderson, M; Arkhipkin, D; Averichev, G S; Badyal, S K; Balewski, J; Barannikova, O; Barnby, L S; Baudot, J; Bekele, S; Belaga, V V; Bellwied, R; Berger, J; Bezverkhny, B I; Bhardwaj, S; Bhaskar, P; Bhati, A K; Bichsel, H; Billmeier, A; Bland, L C; Blyth, C O; Bonner, B E; Botje, M; Boucham, A; Brandin, A; Bravar, A; Cadman, R V; Cai, X Z; Caines, H; Calderón de la Barca Sánchez, M; Carroll, J; Castillo, J; Castro, M; Cebra, D; Chaloupka, P; Chattopadhyay, S; Chen, H F; Chen, Y; Chernenko, S P; Cherney, M; Chikanian, A; Choi, B; Christie, W; Coffin, J P; Cormier, T M; Cramer, J G; Crawford, H J; Das, D; Das, S; Derevschikov, A A; Didenko, L; Dietel, T; Dong, X; Draper, J E; Du, F; Dubey, A K; Dunin, V B; Dunlop, J C; Dutta Majumdar, M R; Eckardt, V; Efimov, L G; Emelianov, V; Engelage, J; Eppley, G; Erazmus, B; Fachini, P; Faine, V; Faivre, J; Fatemi, R; Filimonov, K; Filip, P; Finch, E; Fisyak, Y; Flierl, D; Foley, K J; Fu, J; Gagliardi, C A; Ganti, M S; Gagunashvili, N; Gans, J; Gaudichet, L; Germain, M; Geurts, F; Ghazikhanian, V; Ghosh, P; Gonzalez, J E; Grachov, O; Grigoriev, V; Gronstal, S; Grosnick, D; Guedon, M; Guertin, S M; Gupta, A; Gushin, E; Gutierrez, T D; Hallman, T J; Hardtke, D; Harris, J W; Heinz, M; Henry, T W; Heppelmann, S; Herston, T; Hippolyte, B; Hirsch, A; Hjort, E; Hoffmann, G W; Horsley, M; Huang, H Z; Huang, S L; Humanic, T J; Igo, G; Ishihara, A; Jacobs, P; Jacobs, W W; Janik, M; Johnson, I; Jones, P G; Judd, E G; Kabana, S; Kaneta, M; Kaplan, M; Keane, D; Kiryluk, J; Kisiel, A; Klay, J; Klein, S R; Klyachko, A; Koetke, D D; Kollegger, T; Konstantinov, A S; Kopytine, M; Kotchenda, L; Kovalenko, A D; Kramer, M; Kravtsov, P; Krueger, K; Kuhn, C; Kulikov, A I; Kumar, A; Kunde, G J; Kunz, C L; Kutuev, R Kh; Kuznetsov, A A; Lamont, M A C; Landgraf, J M; Lange, S; Lansdell, C P; Lasiuk, B; Laue, F; Lauret, J; Lebedev, A; Lednický, R; Leontiev, V M; LeVine, M J; Li, C; Li, Q; Lindenbaum, S J; Lisa, M A; Liu, F; Liu, L; Liu, Z; Liu, Q J; Ljubicic, T; Llope, W J; Long, H; Longacre, R S; Lopez-Noriega, M; Love, W A; Ludlam, T; Lynn, D; Ma, J; Ma, Y G; Magestro, D; Mahajan, S; Mangotra, L K; Mahapatra, D P; Majka, R; Manweiler, R; Margetis, S; Markert, C; Martin, L; Marx, J; Matis, H S; Matulenko, Yu A; McShane, T S; Meissner, F; Melnick, Yu; Meschanin, A; Messer, M; Miller, M L; Milosevich, Z; Minaev, N G; Mironov, C; Mishra, D; Mitchell, J; Mohanty, B; Molnar, L; Moore, C F; Mora-Corral, M J; Morozov, V; de Moura, M M; Munhoz, M G; Nandi, B K; Nayak, S K; Nayak, T K; Nelson, J M; Nevski, P; Nikitin, V A; Nogach, L V; Norman, B; Nurushev, S B; Odyniec, G; Ogawa, A; Okorokov, V; Oldenburg, M; Olson, D; Paic, G; Pandey, S U; Pal, S K; Panebratsev, Y; Panitkin, S Y; Pavlinov, A I; Pawlak, T; Perevoztchikov, V; Peryt, W; Petrov, V A; Phatak, S C; Picha, R; Planinic, M; Pluta, J; Porile, N; Porter, J; Poskanzer, A M; Potekhin, M; Potrebenikova, E; Potukuchi, B V K S; Prindle, D; Pruneau, C; Putschke, J; Rai, G; Rakness, G; Raniwala, R; Raniwala, S; Ravel, O; Ray, R L; Razin, S V; Reichhold, D; Reid, J G; Renault, G; Retiere, F; Ridiger, A; Ritter, H G; Roberts, J B; Rogachevski, O V; Romero, J L; Rose, A; Roy, C; Ruan, L J; Rykov, V; Sahoo, R; Sakrejda, I; Salur, S; Sandweiss, J; Savin, I; Schambach, J; Scharenberg, R P; Schmitz, N; Schroeder, L S; Schweda, K; Seger, J; Seliverstov, D; Seyboth, P; Shahaliev, E; Shao, M; Sharma, M; Shestermanov, K E; Shimanskii, S S; Singaraju, R N; Simon, F; Skoro, G; Smirnov, N; Snellings, R; Sood, G; Sorensen, P; Sowinski, J; Spinka, H M; Srivastava, B; Stanislaus, S; Stock, R; Stolpovsky, A; Strikhanov, M; Stringfellow, B; Struck, C; Suaide, A A P; Sugarbaker, E; Suire, C; Sumbera, M; Surrow, B; Symons, T J M; Szanto de Toledo, A; Szarwas, P; Tai, A; Takahashi, J; Tang, A H; Thein, D; Thomas, J H; Tikhomirov, V; Tokarev, M; Tonjes, M B; Trainor, T A; Trentalange, S; Tribble, R E; Trivedi, M D; Trofimov, V; Tsai, O; Ullrich, T; Underwood, D G; Van Buren, G; VanderMolen, A M; Vasiliev, A N; Vasiliev, M; Vigdor, S E; Viyogi, Y P; Voloshin, S A; Waggoner, W; Wang, F; Wang, G; Wang, X L; Wang, Z M; Ward, H; Watson, J W; Wells, R; Westfall, G D; Whitten, C; Wieman, H; Willson, R; Wissink, S W; Witt, R; Wood, J; Wu, J; Xu, N; Xu, Z; Xu, Z Z; Yakutin, A E; Yamamoto, E; Yang, J; Yepes, P; Yurevich, V I; Zanevski, Y V; Zborovský, I; Zhang, H; Zhang, H Y; Zhang, W M; Zhang, Z P; Zołnierczuk, P A; Zoulkarneev, R; Zoulkarneeva, J; Zubarev, A N

    2003-08-15

    We report measurements of single-particle inclusive spectra and two-particle azimuthal distributions of charged hadrons at high transverse momentum (high p(T)) in minimum bias and central d+Au collisions at sqrt[s(NN)]=200 GeV. The inclusive yield is enhanced in d+Au collisions relative to binary-scaled p+p collisions, while the two-particle azimuthal distributions are very similar to those observed in p+p collisions. These results demonstrate that the strong suppression of the inclusive yield and back-to-back correlations at high p(T) previously observed in central Au+Au collisions are due to final-state interactions with the dense medium generated in such collisions.

  15. Progress toward steady-state tokamak operation exploiting the high bootstrap current fraction regime

    DOE PAGES

    Ren, Q. L.; Garofalo, A. M.; Gong, X. Z.; ...

    2016-06-20

    Recent DIII-D experiments have increased the normalized fusion performance of the high bootstrap current fraction tokamak regime toward reactor-relevant steady state operation. The experiments, conducted by a joint team of researchers from the DIII-D and EAST tokamaks, developed a fully noninductive scenario that could be extended on EAST to a demonstration of long pulse steady-state tokamak operation. Improved understanding of scenario stability has led to the achievement of very high values of β p and β N despite strong ITBs. Good confinement has been achieved with reduced toroidal rotation. These high β p plasmas challenge the energy transport understanding, especiallymore » in the electron energy channel. A new turbulent transport model, named 2 TGLF-SAT1, has been developed which improves the transport prediction. Experiments extending results to long pulse on EAST, based on the physics basis developed at DIII-D, have been conducted. Finally, more investigations will be carried out on EAST with more additional auxiliary power to come online in the near term.« less

  16. Advanced Tokamak Stability Theory

    NASA Astrophysics Data System (ADS)

    Zheng, Linjin

    2015-03-01

    The intention of this book is to introduce advanced tokamak stability theory. We start with the derivation of the Grad-Shafranov equation and the construction of various toroidal flux coordinates. An analytical tokamak equilibrium theory is presented to demonstrate the Shafranov shift and how the toroidal hoop force can be balanced by the application of a vertical magnetic field in tokamaks. In addition to advanced theories, this book also discusses the intuitive physics pictures for various experimentally observed phenomena.

  17. Impurity sputtering from the guard limiter of the lower hybrid wave antenna in a tokamak

    NASA Astrophysics Data System (ADS)

    Ou, Jing; Xiang, Nong; Men, Zongzheng

    2018-01-01

    The hot spots on the guard limiter of the lower hybrid wave (LHW) antenna in a tokamak were believed to be associated with the energetic electrons produced by the wave-plasma interaction, leading to a sudden increase of impurity influx and even ending with disruption. To investigate the carbon sputtering from the guard limiter of the LHW antenna, the impurity sputtering yield is calculated by coupling the module of Plasma Surface Interaction [Warrier et al., Comput. Phys. Commun. 46, 160 (2004)] with the models for the sheath of plasma containing energetic electron and for the material heat transport. It is found that the presence of a small population of energetic electrons can change significantly the impurity sputtering yield, as a result of the sheath potential modification. For the typical plasma parameters in the current tokamak, with an increase in the energetic electron component, the physical sputtering yield reaches its maximum and then decreases slowly, while the chemical sputtering yield demonstrates a very sharp increase and then decreases rapidly. In addition, effects of the ion temperature and background electron density on the impurity sputtering are also discussed.

  18. Modulation of Core Turbulent Density Fluctuations by Large-Scale Neoclassical Tearing Mode Islands in the DIII-D Tokamak

    DOE PAGES

    Bardóczi, L.; Rhodes, T. L.; Carter, T. A.; ...

    2016-05-26

    We report the first observation of localized modulation of turbulent density uctuations en (via Beam Emission Spectroscopy) by neoclassical tearing modes (NTMs) in the core of the DIII-D tokamak. NTMs are important as they often lead to severe degradation of plasma confinement and disruptions in high-confinement fusion experiments. Magnetic islands associated with NTMs significantly modify the profiles and turbulence drives. In this experiment n was found to be modulated by 14% across the island. Gyrokinetic simulations suggest that en could be dominantly driven by the ion temperature gradient (ITG) instability.

  19. Impact of an integrated core/SOL description on the R and B T optimization of tokamak fusion reactors

    NASA Astrophysics Data System (ADS)

    Siccinio, M.; Fable, E.; Angioni, C.; Saarelma, S.; Scarabosio, A.; Zohm, H.

    2018-01-01

    An updated and improved version of the 0D divertor and scrape-off layer (SOL) model published in Siccinio et al (2016 Plasma Phys. Control. Fusion 58 125011) was coupled with the 1.5D transport code ASTRA (Pereverzev 1991 IPP Report 5/42, Pereverzev and Yushmanov 2002 IPP Report 5/98 and Fable et al 2013 Plasma Phys. Control. Fusion 55 124028). The resulting numerical tool was employed for various scans in the major radius R and in the toroidal magnetic field B T—for different safety factors q, allowable loop voltages V loop and H factors—in order to identify the most convenient choices for an electricity producing tokamak. Such a scenario analysis was carried out evaluating self-consistently, and simultaneously, the core profile and transport effects, which significantly impact on the fusion power outcome, and the divertor heat loads, which represent one of the most critical issues in view of the realization of fusion power plants (Zohm et al 2013 Nucl. Fusion 53 073019 and Wenninger et al 2017 Nucl. Fusion 57 046002). The main result is that, when divertor limits are enforced, the curves at constant electrical power output are closed on themselves in the R-BT plane, and a maximum achievable power exists—i.e. no benefits would be obtained from a further increase in R and B T once the optimum is reached. This result appears as an intrinsic physical limit for all those devices where a radiative SOL is needed to deal with the power exhaust, and where a lower limit on the power crossing the separatrix (e.g. because of the L-H transition) is present.

  20. Obtaining T1-T2 distribution functions from 1-dimensional T1 and T2 measurements: The pseudo 2-D relaxation model

    NASA Astrophysics Data System (ADS)

    Williamson, Nathan H.; Röding, Magnus; Galvosas, Petrik; Miklavcic, Stanley J.; Nydén, Magnus

    2016-08-01

    We present the pseudo 2-D relaxation model (P2DRM), a method to estimate multidimensional probability distributions of material parameters from independent 1-D measurements. We illustrate its use on 1-D T1 and T2 relaxation measurements of saturated rock and evaluate it on both simulated and experimental T1-T2 correlation measurement data sets. Results were in excellent agreement with the actual, known 2-D distribution in the case of the simulated data set. In both the simulated and experimental case, the functional relationships between T1 and T2 were in good agreement with the T1-T2 correlation maps from the 2-D inverse Laplace transform of the full 2-D data sets. When a 1-D CPMG experiment is combined with a rapid T1 measurement, the P2DRM provides a double-shot method for obtaining a T1-T2 relationship, with significantly decreased experimental time in comparison to the full T1-T2 correlation measurement.

  1. Development of the scintillator-based probe for fast-ion losses in the HL-2A tokamak

    NASA Astrophysics Data System (ADS)

    Zhang, Y. P.; Liu, Yi; Luo, X. B.; Isobe, M.; Yuan, G. L.; Liu, Y. Q.; Hua, Y.; Song, X. Y.; Yang, J. W.; Li, X.; Chen, W.; Li, Y.; Yan, L. W.; Song, X. M.; Yang, Q. W.; Duan, X. R.

    2014-05-01

    A new scintillator-based lost fast-ion probe (SLIP) has been developed and operated in the HL-2A tokamak [L. W. Yan, X. R. Duan, X. T. Ding, J. Q. Dong, Q. W. Yang, Yi Liu, X. L. Zou, D. Q. Liu, W. M. Xuan, L. Y. Chen, J. Rao, X. M. Song, Y. Huang, W. C. Mao, Q. M. Wang, Q. Li, Z. Cao, B. Li, J. Y. Cao, G. J. Lei, J. H. Zhang, X. D. Li, W. Chen, J. Chen, C. H. Cui, Z. Y. Cui, Z. C. Deng, Y. B. Dong, B. B. Feng, Q. D. Gao, X. Y. Han, W. Y. Hong, M. Huang, X. Q. Ji, Z. H. Kang, D. F. Kong, T. Lan, G. S. Li, H. J. Li, Qing Li, W. Li, Y. G. Li, A. D. Liu, Z. T. Liu, C. W. Luo, X. H. Mao, Y. D. Pan, J. F. Peng, Z. B. Shi, S. D. Song, X. Y. Song, H. J. Sun, A. K. Wang, M. X. Wang, Y. Q. Wang, W. W. Xiao, Y. F. Xie, L. H. Yao, D. L. Yu, B. S. Yuan, K. J. Zhao, G. W. Zhong, J. Zhou, J. C. Yan, C. X. Yu, C. H. Pan, Y. Liu, and the HL-2A Team, Nucl. Fusion 51, 094016 (2011)] to measure the losses of neutral beam ions. The design of the probe is based on the concept of the α-particle detectors on Tokamak Fusion Test Reactor (TFTR) using scintillator plates. The probe is capable of traveling across an equatorial plane port and sweeping the aperture angle rotationally with respect to the axis of the probe shaft by two step motors, in order to optimize the radial position and the collimator angle. The energy and the pitch angle of the lost fast ions can be simultaneously measured if the two-dimensional image of scintillation light intensity due to the impact of the lost fast ions is detected. Measurements of the fast-ion losses using the probe have been performed during HL-2A neutral beam injection discharges. The clear experimental evidence of enhanced losses of beam ions during disruptions has been obtained by means of the SLIP system. A detailed description of the probe system and the first experimental results are reported.

  2. Development of the scintillator-based probe for fast-ion losses in the HL-2A tokamak

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

    Zhang, Y. P., E-mail: zhangyp@swip.ac.cn; Liu, Yi; Yuan, G. L.

    A new scintillator-based lost fast-ion probe (SLIP) has been developed and operated in the HL-2A tokamak [L. W. Yan, X. R. Duan, X. T. Ding, J. Q. Dong, Q. W. Yang, Yi Liu, X. L. Zou, D. Q. Liu, W. M. Xuan, L. Y. Chen, J. Rao, X. M. Song, Y. Huang, W. C. Mao, Q. M. Wang, Q. Li, Z. Cao, B. Li, J. Y. Cao, G. J. Lei, J. H. Zhang, X. D. Li, W. Chen, J. Chen, C. H. Cui, Z. Y. Cui, Z. C. Deng, Y. B. Dong, B. B. Feng, Q. D. Gao, X. Y.more » Han, W. Y. Hong, M. Huang, X. Q. Ji, Z. H. Kang, D. F. Kong, T. Lan, G. S. Li, H. J. Li, Qing Li, W. Li, Y. G. Li, A. D. Liu, Z. T. Liu, C. W. Luo, X. H. Mao, Y. D. Pan, J. F. Peng, Z. B. Shi, S. D. Song, X. Y. Song, H. J. Sun, A. K. Wang, M. X. Wang, Y. Q. Wang, W. W. Xiao, Y. F. Xie, L. H. Yao, D. L. Yu, B. S. Yuan, K. J. Zhao, G. W. Zhong, J. Zhou, J. C. Yan, C. X. Yu, C. H. Pan, Y. Liu, and the HL-2A Team , Nucl. Fusion 51, 094016 (2011)] to measure the losses of neutral beam ions. The design of the probe is based on the concept of the α-particle detectors on Tokamak Fusion Test Reactor (TFTR) using scintillator plates. The probe is capable of traveling across an equatorial plane port and sweeping the aperture angle rotationally with respect to the axis of the probe shaft by two step motors, in order to optimize the radial position and the collimator angle. The energy and the pitch angle of the lost fast ions can be simultaneously measured if the two-dimensional image of scintillation light intensity due to the impact of the lost fast ions is detected. Measurements of the fast-ion losses using the probe have been performed during HL-2A neutral beam injection discharges. The clear experimental evidence of enhanced losses of beam ions during disruptions has been obtained by means of the SLIP system. A detailed description of the probe system and the first experimental results are reported.« less

  3. 2D microwave imaging reflectometer electronics.

    PubMed

    Spear, A G; Domier, C W; Hu, X; Muscatello, C M; Ren, X; Tobias, B J; Luhmann, N C

    2014-11-01

    A 2D microwave imaging reflectometer system has been developed to visualize electron density fluctuations on the DIII-D tokamak. Simultaneously illuminated at four probe frequencies, large aperture optics image reflections from four density-dependent cutoff surfaces in the plasma over an extended region of the DIII-D plasma. Localized density fluctuations in the vicinity of the plasma cutoff surfaces modulate the plasma reflections, yielding a 2D image of electron density fluctuations. Details are presented of the receiver down conversion electronics that generate the in-phase (I) and quadrature (Q) reflectometer signals from which 2D density fluctuation data are obtained. Also presented are details on the control system and backplane used to manage the electronics as well as an introduction to the computer based control program.

  4. On the breakdown modes and parameter space of Ohmic Tokamak startup

    NASA Astrophysics Data System (ADS)

    Peng, Yanli; Jiang, Wei; Zhang, Ya; Hu, Xiwei; Zhuang, Ge; Innocenti, Maria; Lapenta, Giovanni

    2017-10-01

    Tokamak plasma has to be hot. The process of turning the initial dilute neutral hydrogen gas at room temperature into fully ionized plasma is called tokamak startup. Even with over 40 years of research, the parameter ranges for the successful startup still aren't determined by numerical simulations but by trial and errors. However, in recent years it has drawn much attention due to one of the challenges faced by ITER: the maximum electric field for startup can't exceed 0.3 V/m, which makes the parameter range for successful startup narrower. Besides, this physical mechanism is far from being understood either theoretically or numerically. In this work, we have simulated the plasma breakdown phase driven by pure Ohmic heating using a particle-in-cell/Monte Carlo code, with the aim of giving a predictive parameter range for most tokamaks, even for ITER. We have found three situations during the discharge, as a function of the initial parameters: no breakdown, breakdown and runaway. Moreover, breakdown delay and volt-second consumption under different initial conditions are evaluated. In addition, we have simulated breakdown on ITER and confirmed that when the electric field is 0.3 V/m, the optimal pre-filling pressure is 0.001 Pa, which is in good agreement with ITER's design.

  5. Regularization of soft-X-ray imaging in the DIII-D tokamak

    DOE PAGES

    Wingen, A.; Shafer, M. W.; Unterberg, E. A.; ...

    2015-03-02

    We developed an image inversion scheme for the soft X-ray imaging system (SXRIS) diagnostic at the DIII-D tokamak in order to obtain the local soft X-ray emission at a poloidal cross-section from the spatially line-integrated image taken by the SXRIS camera. The scheme uses the Tikhonov regularization method since the inversion problem is generally ill-posed. The regularization technique uses the generalized singular value decomposition to determine a solution that depends on a free regularization parameter. The latter has to be chosen carefully, and the so called {\\it L-curve} method to find the optimum regularization parameter is outlined. A representative testmore » image is used to study the properties of the inversion scheme with respect to inversion accuracy, amount/strength of regularization, image noise and image resolution. Moreover, the optimum inversion parameters are identified, while the L-curve method successfully computes the optimum regularization parameter. Noise is found to be the most limiting issue, but sufficient regularization is still possible at noise to signal ratios up to 10%-15%. Finally, the inversion scheme is applied to measured SXRIS data and the line-integrated SXRIS image is successfully inverted.« less

  6. Impact of helical boundary conditions in MHD modeling of RFP and tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Bonfiglio, D.; Cappello, S.; Escande, D. F.; Piovesan, P.; Veranda, M.; Chacón, L.

    2012-10-01

    Helical boundary conditions imposed by the active control system of the RFX-mod device provide a handle to govern the plasma dynamics in both RFP and Ohmic tokamak discharges [1]. By applying an edge radial magnetic field with proper helicity, it is possible to increase the persistence of the spontaneous helical RFP states at high current,and to stimulate them also at low current or high density. Helical BCs even allow to access helical states with different helicity than the spontaneous one [2]. In Ohmic tokamak operation at q(a)<2, the presence of the 2/1 RWM reduces the sawtoothing activity of the 1/1 internal kink, which takes a stationary snake-like character instead. Many of these features are qualitatively reproduced in 3D nonlinear MHD modeling. We study the impact of helical BCs on the MHD dynamics in both RFP and tokamak with two successfully benchmarked numerical tools, SpeCyl and PIXIE3D [3]. We recover the bifurcation from a sawtooth to a snake solution when imposing a 2/1 BC in the tokamak case and we interpret this as a toroidal/nonlinear coupling effect. We show that the bifurcation is more easily stimulated with a 1/1 BC.[4pt] [1] P. Piovesan, invited talk this meeting[0pt] [2] M. Veranda et al EPS-ICPP Conference (2012) P4.004[0pt] [3] D. Bonfiglio et al Phys. Plasmas (2010)

  7. Runaway Electrons Modeling and Nanoparticle Plasma Jet Penetration into Tokamak Plasma

    NASA Astrophysics Data System (ADS)

    Galkin, S. A.; Bogatu, I. N.

    2017-10-01

    A novel idea to probe runaway electrons (REs) by superfast injection of high velocity nanoparticle plasma jet (NPPJ) from a plasma accelerator needs to be sustained by both RE dynamics modeling and simulation of NPPJ penetration through increasing tokamak magnetic field. We present our recent progress in both areas. RE simulation is based on the model, including Dreicer and ``avalanche'' mechanisms of RE generation, with emphasis on high Zeff effects. The high-density hyper-velocity C60 and BN NPPJ penetration through transversal B-field is conducted with the Hybrid Electro-Magnetic code (HEM-2D) in cylindrical coordinates, with 1/R B-field dependence for both DIII-D and ITER tokamaks. Work is supported in part by US DOE SBIR Grant.

  8. Electron Cyclotron Current Drive Efficiency in General Tokamak Geometry and Its Application to Advanced Tokamak Plasmas

    NASA Astrophysics Data System (ADS)

    Lin-Liu, Y. R.; Chan, V. S.; Luce, T. C.; Prater, R.

    1998-11-01

    Owing to relativistic mass shift in the cyclotron resonance condition, a simple and accurate interpolation formula for estimating the current drive efficiency, such as those(S.C. Chiu et al.), Nucl. Fusion 29, 2175 (1989).^,(D.A. Ehst and C.F.F. Karney, Nucl. Fusion 31), 1933 (1991). commonly used in FWCD, is not available in the case of ECCD. In this work, we model ECCD using the adjoint techniques. A semi-analytic adjoint function appropriate for general tokamak geometry is obtained using Fisch's relativistic collision model. Predictions of off-axis ECCD qualitatively and semi-quantitatively agrees with those of Cohen,(R.H. Cohen, Phys. Fluids 30), 2442 (1987). currently implemented in the raytracing code TORAY. The dependences of the current drive efficiency on the wave launch configuration and the plasma parameters will be presented. Strong absorption of the wave away from the resonance layer is shown to be an important factor in optimizing the off-axis ECCD for application to advanced tokamak operations.

  9. Dynamic basis for dG•dT misincorporation via tautomerization and ionization

    NASA Astrophysics Data System (ADS)

    Kimsey, Isaac J.; Szymanski, Eric S.; Zahurancik, Walter J.; Shakya, Anisha; Xue, Yi; Chu, Chia-Chieh; Sathyamoorthy, Bharathwaj; Suo, Zucai; Al-Hashimi, Hashim M.

    2018-02-01

    Tautomeric and anionic Watson-Crick-like mismatches have important roles in replication and translation errors through mechanisms that are not fully understood. Here, using NMR relaxation dispersion, we resolve a sequence-dependent kinetic network connecting G•T/U wobbles with three distinct Watson-Crick mismatches: two rapidly exchanging tautomeric species (Genol•T/UG•Tenol/Uenol population less than 0.4%) and one anionic species (G•T-/U- population around 0.001% at neutral pH). The sequence-dependent tautomerization or ionization step was inserted into a minimal kinetic mechanism for correct incorporation during replication after the initial binding of the nucleotide, leading to accurate predictions of the probability of dG•dT misincorporation across different polymerases and pH conditions and for a chemically modified nucleotide, and providing mechanisms for sequence-dependent misincorporation. Our results indicate that the energetic penalty for tautomerization and/or ionization accounts for an approximately 10-2 to 10-3-fold discrimination against misincorporation, which proceeds primarily via tautomeric dGenol•dT and dG•dTenol, with contributions from anionic dG•dT- dominant at pH 8.4 and above or for some mutagenic nucleotides.

  10. Isoguanine quartets formed by d(T4isoG4T4): tetraplex identification and stability.

    PubMed Central

    Seela, F; Wei, C; Melenewski, A

    1996-01-01

    The self-aggregation of the oligonucleotide d(T4isoG4T4) (1) is investigated. Based on ion exchange HPLC experiments and CD spectroscopy, a tetrameric structure is identified. This structure was formed in the presence of sodium ions and shows almost the same chromatographic mobility on ion exchange HPLC as d(T4G4T4) (2). The ratio of aggregate versus monomer is temperature dependent and the tetraplex of [d(T4isoG4T4)]4 is more stable than that of [d(T4G4T4)]4. A mixture of d(T4isoG4T4) and d(T4G4T4) forms mixed tetraplexes containing strands of d(T4isoG4T4) and d(T4G4T4). PMID:9016664

  11. Design, simulation and construction of the Taban tokamak

    NASA Astrophysics Data System (ADS)

    H, R. MIRZAEI; R, AMROLLAHI

    2018-04-01

    This paper describes the design and construction of the Taban tokamak, which is located in Amirkabir University of Technology, Tehran, Iran. The Taban tokamak was designed for plasma investigation. The design, simulation and construction of essential parts of the Taban tokamak such as the toroidal field (TF) system, ohmic heating (OH) system and equilibrium field system and their power supplies are presented. For the Taban tokamak, the toroidal magnetic coil was designed to produce a maximum field of 0.7 T at R = 0.45 m. The power supply of the TF was a 130 kJ, 0–10 kV capacitor bank. Ripples of toroidal magnetic field at the plasma edge and plasma center are 0.2% and 0.014%, respectively. For the OH system with 3 kA current, the stray field in the plasma region is less than 40 G over 80% of the plasma volume. The power supply of the OH system consists of two stages, as follows. The fast bank stage is a 120 μF, 0–5 kV capacitor that produces 2.5 kA in 400 μs and the slow bank stage is 93 mF, 600 V that can produce a maximum of 3 kA. The equilibrium system can produce uniform magnetic field at plasma volume. This system’s power supply, like the OH system, consists of two stages, so that the fast bank stage is 500 μF, 800 V and the slow bank stage is 110 mF, 200 V.

  12. Nanoparticle Plasma Jet as Fast Probe for Runaway Electrons in Tokamak Disruptions

    NASA Astrophysics Data System (ADS)

    Bogatu, I. N.; Galkin, S. A.

    2017-10-01

    Successful probing of runaway electrons (REs) requires fast (1 - 2 ms) high-speed injection of enough mass able to penetrate through tokamak toroidal B-field (2 - 5 T) over 1 - 2 m distance with large assimilation fraction in core plasma. A nanoparticle plasma jet (NPPJ) from a plasma gun is a unique combination of millisecond trigger-to-delivery response and mass-velocity of 100 mg at several km/s for deep direct injection into current channel of rapidly ( 1 ms) cooling post-TQ core plasma. After C60 NPPJ test bed demonstration we started to work on ITER-compatible boron nitride (BN) NPPJ. Once injected into plasma, BN NP undergoes ablative sublimation, thermally decomposes into B and N, and releases abundant B and N high-charge ions along plasma-traversing path and into the core. We present basic characteristics of our BN NPPJ concept and first results from B and N ions on Zeff > 1 effect on REs dynamics by using a self-consistent model for RE current density. Simulation results of BNQ+ NPPJ penetration through tokamak B-field to RE beam location performed with Hybrid Electro-Magnetic code (HEM-2D) are also presented. Work supported by U.S. DOE SBIR Grant.

  13. Observation of finite-. beta. MHD phenomena in tokamaks

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

    McGuire, K.M.

    1984-09-01

    Stable high-beta plasmas are required for the tokamak to attain an economical fusion reactor. Recently, intense neutral beam heating experiments in tokamaks have shown new effects on plasma stability and confinement associated with high beta plasmas. The observed spectrum of MHD fluctuations at high beta is clearly dominated by the n = 1 mode when the q = 1 surface is in the plasma. The m/n = 1/1 mode drives other n = 1 modes through toroidal coupling and n > 1 modes through nonlinear coupling. On PDX, with near perpendicular injection, a resonant interaction between the n = 1more » internal kink and the trapped fast ions results in loss of beam particles and heating power. Key parameters in the theory are the value of q/sub 0/ and the injection angle. High frequency broadband magnetic fluctuations have been observed on ISX-B and D-III and a correlation with the deterioration of plasma confinement was reported. During enhanced confinement (H-mode) discharges in divertor plasmas, two new edge instabilities were observed, both localized radially near the separatrix. By assembling results from the different tokamak experiments, it is found that the simple theoretical ideal MHD beta limit has not been exceeded. Whether this represents an ultimate tokamak limit or if beta optimized configurations (Dee- or bean-shaped plasmas) can exceed this limit and perhaps enter a second regime of stability remains to be clarified.« less

  14. Application of automatic gain control for radiometer diagnostic in SST-1 tokamak.

    PubMed

    Makwana, Foram R; Siju, Varsha; Edappala, Praveenlal; Pathak, S K

    2017-12-01

    This paper describes the characterisation of a negative feedback type of automatic gain control (AGC) circuit that will be an integral part of the heterodyne radiometer system operating at a frequency range of 75-86 GHz at SST-1 tokamak. The developed AGC circuit is a combination of variable gain amplifier and log amplifier which provides both gain and attenuation typically up to 15 dB and 45 dB, respectively, at a fixed set point voltage and it has been explored for the first time in tokamak radiometry application. The other important characteristics are that it exhibits a very fast response time of 390 ns to understand the fast dynamics of electron cyclotron emission and can operate at very wide input RF power dynamic range of around 60 dB that ensures signal level within the dynamic range of the detection system.

  15. 17 CFR 240.11a1-1(T) - Transactions yielding priority, parity, and precedence.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ..., parity, and precedence. 240.11a1-1(T) Section 240.11a1-1(T) Commodity and Securities Exchanges SECURITIES... (rule 11a-1) § 240.11a1-1(T) Transactions yielding priority, parity, and precedence. (a) A transaction... section 11(a)(1) of the Act or specified in 17 CFR 240.11a1-4(T) shall be deemed to be revenue derived...

  16. 17 CFR 240.11a1-1(T) - Transactions yielding priority, parity, and precedence.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ..., parity, and precedence. 240.11a1-1(T) Section 240.11a1-1(T) Commodity and Securities Exchanges SECURITIES... (rule 11a-1) § 240.11a1-1(T) Transactions yielding priority, parity, and precedence. (a) A transaction... section 11(a)(1) of the Act or specified in 17 CFR 240.11a1-4(T) shall be deemed to be revenue derived...

  17. Microflow High-p,T Intensification of Vitamin D3 Synthesis Using an Ultraviolet Lamp

    PubMed Central

    2017-01-01

    Herewith a new process concept for synthesis is presented which combines both UV-photoirradiation and high-p,T intensification (photo-high-p,T) in continuous flow. The application of this procedure to Vitamin D3 synthesis promotes thermal shifting of the equilibrium from the reaction intermediate to the product. This is enabled by microreactors which allow operation under harsh conditions such as the high temperature used here. This provides, to our best knowledge, a new kind of process combination (novel process window). As a result, in less than 1 min, 42% conversion of 7-dehydrocholesterol can be achieved giving a 17% yield and 40% selectivity of Vitamin D3. This approach enhances productivity by up to 2 orders of magnitude compared with the current capillary based vitamin D3 synthesis, because, under the microflow conditions, photochemistry can be performed at fairly high concentration and up to 20 times faster. PMID:29503521

  18. Energetic-ion-driven global instabilities in stellarator/helical plasmas and comparison with tokamak plasmas

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

    Toi, K.; Ogawa, K.; Isobe, M.

    2011-01-01

    Comprehensive understanding of energetic-ion-driven global instabilities such as Alfven eigenmodes (AEs) and their impact on energetic ions and bulk plasma is crucially important for tokamak and stellarator/helical plasmas and in the future for deuterium-tritium (DT) burning plasma experiments. Various types of global modes and their associated enhanced energetic ion transport are commonly observed in toroidal plasmas. Toroidicity-induced AEs and ellipticity-induced AEs, whose gaps are generated through poloidal mode coupling, are observed in both tokamak and stellarator/helical plasmas. Global AEs and reversed shear AEs, where toroidal couplings are not as dominant were also observed in those plasmas. Helicity induced AEs thatmore » exist only in 3D plasmas are observed in the large helical device (LHD) and Wendelstein 7 Advanced Stellarator plasmas. In addition, the geodesic acoustic mode that comes from plasma compressibility is destabilized by energetic ions in both tokamak and LHD plasmas. Nonlinear interaction of these modes and their influence on the confinement of the bulk plasma as well as energetic ions are observed in both plasmas. In this paper, the similarities and differences in these instabilities and their consequences for tokamak and stellarator/helical plasmas are summarized through comparison with the data sets obtained in LHD. In particular, this paper focuses on the differences caused by the rotational transform profile and the 2D or 3D geometrical structure of the plasma equilibrium. Important issues left for future study are listed.« less

  19. Low-frequency, Raman-active vibrational modes of poly(dA).poly(dT)

    NASA Astrophysics Data System (ADS)

    Liu, C.; Edwards, G. S.; Morgan, S.; Silberman, E.

    1989-12-01

    The Raman activity of low-frequency (20-300 cm-1) vibrational modes of dehydrated, oriented fibers of the sodium salts of poly(dA).poly(dT) and random sequenced DNA have been measured. Distinct bands near 60, 75-100, and 125-140 cm-1 are resolved in poly(dA).poly(dT). The Raman activity of the two lowest bands correlate with the previously observed infrared activity of poly(dA).poly(dT). The apparent reduction in spectral line broadening for poly(dA).poly(dT), as demonstrated by this and previous measurements of a number of different polynucleotides, is considered as possible evidence for inhomogeneous line broadening.

  20. Computational Study of Anomalous Transport in High Beta DIII-D Discharges with ITBs

    NASA Astrophysics Data System (ADS)

    Pankin, Alexei; Garofalo, Andrea; Grierson, Brian; Kritz, Arnold; Rafiq, Tariq

    2015-11-01

    The advanced tokamak scenarios require a large bootstrap current fraction and high β. These large values are often outside the range that occurs in ``conventional'' tokamak discharges. The GLF23, TGLF, and MMM transport models have been previously validated for discharges with parameters associated with ``conventional'' tokamak discharges. It has been demonstrated that the TGLF model under-predicts anomalous transport in high β DIII-D discharges [A.M. Garofalo et al. 2015 TTF Workshop]. In this research, the validity of MMM7.1 model [T. Rafiq et al. Phys. Plasmas 20 032506 (2013)] is tested for high β DIII-D discharges with low and high torque. In addition, the sensitivity of the anomalous transport to β is examined. It is shown that the MMM7.1 model over-predicts the anomalous transport in the DIII-D discharge 154406. In particular, a significant level of anomalous transport is found just outside the internal transport barrier. Differences in the anomalous transport predicted using TGLF and MMM7.1 are reviewed. Mechanisms for quenching of anomalous transport in the ITB regions of high-beta discharges are investigated. This research is supported by US Department of Energy.

  1. Measurement of the Cabibbo-Kobayashi-Maskawa Angle {gamma} in B{sup {+-}}{yields}D{sup (*)}K{sup {+-}} Decays with a Dalitz Analysis of D{yields}K{sub S}{sup 0}{pi}{sup -}{pi}{sup +}

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

    Aubert, B.; Barate, R.; Boutigny, D.

    2005-09-16

    We report on a measurement of the Cabibbo-Kobayashi-Maskawa CP-violating phase {gamma} through a Dalitz analysis of neutral D decays to K{sub S}{sup 0}{pi}{sup -}{pi}{sup +} in the processes B{sup {+-}}{yields}D{sup (*)}K{sup {+-}}, D*{yields}D{pi}{sup 0}, D{gamma}. Using a sample of 227x10{sup 6} BB pairs collected by the BABAR detector, we measure the amplitude ratios r{sub B}=0.12{+-}0.08{+-}0.03{+-}0.04 and r{sub B}*=0.17{+-}0.10{+-}0.03{+-}0.03, the relative strong phases {delta}{sub B}=(104{+-}45{sub -21-24}{sup +17+16}) deg. and {delta}{sub B}*=(-64{+-}41{sub -12}{sup +14}{+-}15) deg. between the amplitudes A(B{sup -}{yields}D{sup (*)0}K{sup -}) and A(B{sup -}{yields}D{sup (*)0}K{sup -}), and {gamma}=(70{+-}31{sub -10-11}{sup +12+14}) deg. The first error is statistical, the second is the experimentalmore » systematic uncertainty, and the third reflects the Dalitz model uncertainty. The results for the strong and weak phases have a twofold ambiguity.« less

  2. Tunneling chemical reactions D+H{sub 2}{yields}DH+H and D+DH{yields}D{sub 2}+H in solid D{sub 2}-H{sub 2} and HD-H{sub 2} mixtures: An electron-spin-resonance study

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

    Kumada, Takayuki

    2006-03-07

    Tunneling chemical reactions D+H{sub 2}{yields}DH+H and D+DH{yields}D{sub 2}+H in solid HD-H{sub 2} and D{sub 2}-H{sub 2} mixtures were studied in the temperature range between 4 and 8 K. These reactions were initiated by UV photolysis of DI molecules doped in these solids for 30 s and followed by measuring the time course of electron-spin-resonance (ESR) intensities of D and H atoms. ESR intensity of D atoms produced by the photolysis decreases but that of H atoms increases with time. Time course of the D and H intensities has the fast and slow processes. The fast process, which finishes within {approx}300more » s after the photolysis, is assigned to the reaction of D atom with one of its nearest-neighboring H{sub 2} molecules, D(H{sub 2}){sub n}(HD){sub 12-n}{yields}H(H{sub 2}){sub n-1}(HD){sub 13-n} or D(H{sub 2}){sub n}(D{sub 2}){sub 12-n}{yields}H(HD)(H{sub 2}){sub n-1}(D{sub 2}){sub 12-n} for 12{>=}n{>=}1. Rate constant for the D+H{sub 2} reaction between neighboring D atom-H{sub 2} molecule pair is determined to be (7.5{+-}0.7)x10{sup -3} s{sup -1} in solid HD-H{sub 2} and (1.3{+-}0.3)x10{sup -2} s{sup -1} in D{sub 2}-H{sub 2} at 4.1 K, which is very close to that calculated based on the theory of chemical reaction in gas phase by Hancock et al. [J. Chem. Phys. 91, 3492 (1989)] and Takayanagi and Sato [J. Chem. Phys. 92, 2862 (1990)]. This rate constant was found to be independent of temperature up to 7 K within experimental error of {+-}30%. The slow process is assigned to the reaction of D atom produced in a cage fully surrounded by HD or D{sub 2} molecules, D(HD){sub 12} or D(D{sub 2}){sub 12}. This D atom undergoes the D+DH reaction with one of its nearest-neighboring HD molecules in solid HD-H{sub 2} or diffuses to the neighbor of H{sub 2} molecules to allow the D+H{sub 2} reaction in solid HD-H{sub 2} and D{sub 2}-H{sub 2}. The former is the main channel in solid HD-H{sub 2} below 6 K where D atoms diffuse very slowly, whereas the latter dominates

  3. 42GHz ECRH assisted Plasma Breakdown in tokamak SST-1

    NASA Astrophysics Data System (ADS)

    Shukla, B. K.; Pradhan, S.; Patel, Paresh; Babu, Rajan; Patel, Jatin; Patel, Harshida; Dhorajia, Pragnesh; Tanna, V.; Atrey, P. K.; Manchanda, R.; Gupta, Manoj; Joisa, Shankar; Gupta, C. N.; Danial, Raju; Singh, Prashant; Jha, R.; Bora, D.

    2015-03-01

    In SST-1, 42GHz ECRH system has been commissioned to carry out breakdown and heating experiments at 0.75T and 1.5T operating toroidal magnetic fields. The 42GHz ECRH system consists of high power microwave source Gyrotron capable to deliver 500kW microwave power for 500ms duration, approximately 20 meter long transmission line and a mirror based launcher. The ECRH power in fundamental O-mode & second harmonic X-mode is launched from low field side (radial port) of the tokamak. At 0.75T operation, approximately 300 kW ECH power is launched in second harmonic X-mode and successful ECRH assisted breakdown is achieved at low loop_voltage ~ 3V. The ECRH power is launched around 45ms prior to loop voltage. The hydrogen pressure in tokamak is maintained ~ 1×10-5mbar and the pre-ionized density is ~ 4×1012/cc. At 1.5T operating toroidal magnetic field, the ECH power is launched in fundamental O-mode. The ECH power at fundamental harmonic is varied from 100 kW to 250 kW and successful breakdown is achieved in all ECRH shots. In fundamental harmonic there is no delay in breakdown while at second harmonic ~ 40ms delay is observed, which is normal in case of second harmonic ECRH assisted breakdown.

  4. Interaction of external n  =  1 magnetic fields with the sawtooth instability in low-q RFX-mod and DIII-D tokamaks

    NASA Astrophysics Data System (ADS)

    Piron, C.; Martin, P.; Bonfiglio, D.; Hanson, J.; Logan, N. C.; Paz-Soldan, C.; Piovesan, P.; Turco, F.; Bialek, J.; Franz, P.; Jackson, G.; Lanctot, M. J.; Navratil, G. A.; Okabayashi, M.; Strait, E.; Terranova, D.; Turnbull, A.

    2016-10-01

    External n  =  1 magnetic fields are applied in RFX-mod and DIII-D low safety factor Tokamak plasmas to investigate their interaction with the internal MHD dynamics and in particular with the sawtooth instability. In these experiments the applied magnetic fields cause a reduction of both the sawtooth amplitude and period, leading to an overall stabilizing effect on the oscillations. In RFX-mod sawteeth eventually disappear and are replaced by a stationary m  =  1, n  =  1 helical equilibrium without an increase in disruptivity. However toroidal rotation is significantly reduced in these plasmas, thus it is likely that the sawtooth mitigation in these experiments is due to the combination of the helically deformed core and the reduced rotation. The former effect is qualitatively well reproduced by nonlinear MHD simulations performed with the PIXIE3D code. The results obtained in these RFX-mod experiments motivated similar ones in DIII-D L-mode diverted Tokamak plasmas at low q 95. These experiments succeeded in reproducing the sawtooth mitigation with the approach developed in RFX-mod. In DIII-D this effect is correlated with a clear increase of the n  =  1 plasma response, that indicates an enhancement of the coupling to the marginally stable n  =  1 external kink, as simulations with the linear MHD code IPEC suggest. A significant rotation braking in the plasma core is also observed in DIII-D. Numerical calculations of the neoclassical toroidal viscosity (NTV) carried out with PENT identify this torque as a possible contributor for this effect.

  5. Development of a cross-polarization scattering system for the measurement of internal magnetic fluctuations in the DIII-D tokamak

    DOE PAGES

    Rhodes, Terry L.; Peebles, William A.; Crocker, Neal A.; ...

    2014-08-05

    The design and performance of a new cross-polarization scattering (CPS) system for the localized measurement of internal magnetic fluctuations is presented. CPS is a process whereby magnetic fluctuations scatter incident electromagnetic radiation into a perpendicular polarization which is subsequently detected. A new CPS design that incorporates a unique scattering geometry was laboratory tested, optimized, and installed on the DIII-D tokamak. Plasma tests of signal-to-noise, polarization purity, and frequency response indicate proper functioning of the system. Lastly, CPS data show interesting features related to internal MHD perturbations known as sawteeth that are not observed on density fluctuations.

  6. Noninductively Driven Tokamak Plasmas at Near-Unity Toroidal Beta

    DOE PAGES

    Schlossberg, David J.; Bodner, Grant M.; Bongard, Michael W.; ...

    2017-07-01

    Access to and characterization of sustained, toroidally confined plasmas with a very high plasma-to-magnetic pressure ratio (β t), low internal inductance, high elongation, and nonsolenoidal current drive is a central goal of present tokamak plasma research. Stable access to this desirable parameter space is demonstrated in plasmas with ultralow aspect ratio and high elongation. Local helicity injection provides nonsolenoidal sustainment, low internal inductance, and ion heating. Equilibrium analyses indicate β t up to ~100% with a minimum |B| well spanning up to ~50% of the plasma volume.

  7. Noninductively Driven Tokamak Plasmas at Near-Unity Toroidal Beta.

    PubMed

    Schlossberg, D J; Bodner, G M; Bongard, M W; Burke, M G; Fonck, R J; Perry, J M; Reusch, J A

    2017-07-21

    Access to and characterization of sustained, toroidally confined plasmas with a very high plasma-to-magnetic pressure ratio (β_{t}), low internal inductance, high elongation, and nonsolenoidal current drive is a central goal of present tokamak plasma research. Stable access to this desirable parameter space is demonstrated in plasmas with ultralow aspect ratio and high elongation. Local helicity injection provides nonsolenoidal sustainment, low internal inductance, and ion heating. Equilibrium analyses indicate β_{t} up to ∼100% with a minimum |B| well spanning up to ∼50% of the plasma volume.

  8. 3D Monte-Carlo study of toroidally discontinuous limiter SOL configurations of Aditya tokamak

    NASA Astrophysics Data System (ADS)

    Sahoo, Bibhu Prasad; Sharma, Devendra; Jha, Ratneshwar; Feng, Yühe

    2017-08-01

    The plasma-neutral transport in the scrape-off layer (SOL) region formed by toroidally discontinuous limiters deviates from usual uniform SOL approximations when 3D effects caused by limiter discreteness begin to dominate. In an upgrade version of the Aditya tokamak, originally having a toroidally localized poloidal ring-like limiter, the newer outboard block and inboard belt limiters are expected to have smaller connection lengths and a multiple fold toroidal periodicity. The characteristics of plasma discharges may accordingly vary from the original observations of large diffusivity, and a net improvement and the stability of the discharges are desired. The estimations related to 3D effects in the ring limiter plasma transport are also expected to be modified and are updated by predictive simulations of transport in the new block limiter configuration. A comparison between the ring limiter results and those from new simulations with block limiter SOL shows that for the grids produced using same core plasma equilibrium, the modified SOL plasma flows and flux components have enhanced poloidal periodicity in the block limiter case. These SOL modifications result in a reduced net recycling for the equivalent edge density values. Predictions are also made about the relative level of the diffusive transport and its impact on the factors limiting the operational regime.

  9. Microinstability properties of negative magnetic shear discharges in the Tokamak Fusion Test Reactor and DIII-D

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

    Rewoldt, G.; Tang, W.M.; Lao, L.L.

    1997-03-01

    The microinstability properties of discharges with negative (reversed) magnetic shear in the Tokamak Fusion Test Reactor (TFTR) and DIII-D experiments with and without confinement transitions are investigated. A comprehensive kinetic linear eigenmode calculation employing the ballooning representation is employed with experimentally measured profile data, and using the corresponding numerically computed magnetohydrodynamic (MHD) equilibria. The instability considered is the toroidal drift mode (trapped-electron-{eta}{sub i} mode). A variety of physical effects associated with differing q-profiles are explained. In addition, different negative magnetic shear discharges at different times in the discharge for TFTR and DIII-D are analyzed. The effects of sheared toroidal rotation,more » using data from direct spectroscopic measurements for carbon, are analyzed using comparisons with results from a two-dimensional calculation. Comparisons are also made for nonlinear stabilization associated with shear in E{sub r}/RB{sub {theta}}. The relative importance of changes in different profiles (density, temperature, q, rotation, etc.) on the linear growth rates is considered.« less

  10. Scoping and sensitivity analyses for the Demonstration Tokamak Hybrid Reactor (DTHR)

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

    Sink, D.A.; Gibson, G.

    1979-03-01

    The results of an extensive set of parametric studies are presented which provide analytical data of the effects of various tokamak parameters on the performance and cost of the DTHR (Demonstration Tokamak Hybrid Reactor). The studies were centered on a point design which is described in detail. Variations in the device size, neutron wall loading, and plasma aspect ratio are presented, and the effects on direct hardware costs, fissile fuel production (breeding), fusion power production, electrical power consumption, and thermal power production are shown graphically. The studies considered both ignition and beam-driven operations of DTHR and yielded results based onmore » two empirical scaling laws presently used in reactor studies. Sensitivity studies were also made for variations in the following key parameters: the plasma elongation, the minor radius, the TF coil peak field, the neutral beam injection power, and the Z/sub eff/ of the plasma.« less

  11. Global two-fluid turbulence simulations of L-H transitions and edge localized mode dynamics in the COMPASS-D tokamak

    NASA Astrophysics Data System (ADS)

    Thyagaraja, A.; Valovič, M.; Knight, P. J.

    2010-04-01

    It is shown that the transition from L-mode to H-mode regimes in tokamaks can be reproduced using a two-fluid, fully electromagnetic, plasma model when a suitable particle sink is added at the edge. Such a model is implemented in the CUTIE code [A. Thyagaraja et al., Eur. J. Mech. B/Fluids 23, 475 (2004)] and is illustrated on plasma parameters that mimic those in the COMPASS-D tokamak with electron cyclotron resonance heating [Fielding et al., Plasma Phys. Contr. Fusion 42, A191 (2000)]. In particular, it is shown that holding the heating power, current, and magnetic field constant and increasing the fuelling rate to raise the plasma density leads spontaneously to the formation of an edge transport barrier (ETB) which occurs going from low to higher density experimentally. In the following quiescent period in which the stored energy of the plasma rises linearly with time, a dynamical transition occurs in the simulation with the appearance of features resembling strong edge localized modes. The simulation qualitatively reproduces many features observed in the experiment. Its relative robustness suggests that some, at least of the observed characteristics of ETBs and L-H transitions, can be captured in the global electromagnetic turbulence model.

  12. 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.

  13. Evaluation of multimodal segmentation based on 3D T1-, T2- and FLAIR-weighted images - the difficulty of choosing.

    PubMed

    Lindig, Tobias; Kotikalapudi, Raviteja; Schweikardt, Daniel; Martin, Pascal; Bender, Friedemann; Klose, Uwe; Ernemann, Ulrike; Focke, Niels K; Bender, Benjamin

    2018-04-15

    Voxel-based morphometry is still mainly based on T1-weighted MRI scans. Misclassification of vessels and dura mater as gray matter has been previously reported. Goal of the present work was to evaluate the effect of multimodal segmentation methods available in SPM12, and their influence on identification of age related atrophy and lesion detection in epilepsy patients. 3D T1-, T2- and FLAIR-images of 77 healthy adults (mean age 35.8 years, 19-66 years, 45 females), 7 patients with malformation of cortical development (MCD) (mean age 28.1 years,19-40 years, 3 females), and 5 patients with left hippocampal sclerosis (LHS) (mean age 49.0 years, 25-67 years, 3 females) from a 3T scanner were evaluated. Segmentation based on T1-only, T1+T2, T1+FLAIR, T2+FLAIR, and T1+T2+FLAIR were compared in the healthy subjects. Clinical VBM results based on the different segmentation approaches for MCD and for LHS were compared. T1-only segmentation overestimated total intracranial volume by about 80ml compared to the other segmentation methods. This was due to misclassification of dura mater and vessels as GM and CSF. Significant differences were found for several anatomical regions: the occipital lobe, the basal ganglia/thalamus, the pre- and postcentral gyrus, the cerebellum, and the brainstem. None of the segmentation methods yielded completely satisfying results for the basal ganglia/thalamus and the brainstem. The best correlation with age could be found for the multimodal T1+T2+FLAIR segmentation. Highest T-scores for identification of LHS were found for T1+T2 segmentation, while highest T-scores for MCD were dependent on lesion and anatomical location. Multimodal segmentation is superior to T1-only segmentation and reduces the misclassification of dura mater and vessels as GM and CSF. Depending on the anatomical region and the pathology of interest (atrophy, lesion detection, etc.), different combinations of T1, T2 and FLAIR yield optimal results. Copyright © 2017 Elsevier

  14. 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

  15. Hybrid model for simulation of plasma jet injection in tokamak

    NASA Astrophysics Data System (ADS)

    Galkin, Sergei A.; Bogatu, I. N.

    2016-10-01

    Hybrid kinetic model of plasma treats the ions as kinetic particles and the electrons as charge neutralizing massless fluid. The model is essentially applicable when most of the energy is concentrated in the ions rather than in the electrons, i.e. it is well suited for the high-density hyper-velocity C60 plasma jet. The hybrid model separates the slower ion time scale from the faster electron time scale, which becomes disregardable. That is why hybrid codes consistently outperform the traditional PIC codes in computational efficiency, still resolving kinetic ions effects. We discuss 2D hybrid model and code with exact energy conservation numerical algorithm and present some results of its application to simulation of C60 plasma jet penetration through tokamak-like magnetic barrier. We also examine the 3D model/code extension and its possible applications to tokamak and ionospheric plasmas. The work is supported in part by US DOE DE-SC0015776 Grant.

  16. Temperature derivatives for fusion reactivity of D-D and D-T

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

    Langenbrunner, James R.; Makaruk, Hanna Ewa

    Deuterium-tritium (D-T) and deuterium-deuterium (D-D) fusion reaction rates are observable using leakage gamma flux. A direct measurement of γ-rays with equipment that exhibits fast temporal response could be used to infer temperature, if the detector signal is amenable for taking the logarithmic time-derivative, alpha. We consider the temperature dependence for fusion cross section reactivity.

  17. Magnetic diagnostics for equilibrium reconstructions with eddy currents on the lithium tokamak experimenta)

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

    Schmitt, J. C.; Bialek, J.; Lazerson, S.

    2014-11-01

    The Lithium Tokamak eXperiment is a spherical tokamak with a close-fitting low-recycling wall composed of thin lithium layers evaporated onto a stainless steel-lined copper shell. Long-lived non-axisymmetric eddy currents are induced in the shell and vacuum vessel by transient plasma and coil currents and these eddy currents influence both the plasma and the magnetic diagnositc signals that are used as constraints for equilibrium reconstruction. A newly installed set of re-entrant magnetic diagnostics and internal saddle flux loops, compatible with high-temperatures and lithium environments, is discussed. Details of the axisymmetric (2D) and non-axisymmetric (3D) treatments of the eddy currents and themore » equilibrium reconstruction are presented.« less

  18. Magnetic diagnostics for equilibrium reconstructions with eddy currents on the lithium tokamak experiment

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

    Schmitt, J. C., E-mail: jschmitt@pppl.gov; Lazerson, S.; Majeski, R.

    2014-11-15

    The Lithium Tokamak eXperiment is a spherical tokamak with a close-fitting low-recycling wall composed of thin lithium layers evaporated onto a stainless steel-lined copper shell. Long-lived non-axisymmetric eddy currents are induced in the shell and vacuum vessel by transient plasma and coil currents and these eddy currents influence both the plasma and the magnetic diagnostic signals that are used as constraints for equilibrium reconstruction. A newly installed set of re-entrant magnetic diagnostics and internal saddle flux loops, compatible with high-temperatures and lithium environments, is discussed. Details of the axisymmetric (2D) and non-axisymmetric (3D) treatments of the eddy currents and themore » equilibrium reconstruction are presented.« less

  19. 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.

  20. 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

  1. Self-Organized Stationary States of Tokamaks

    DOE PAGES

    Jardin, S. C.; Ferraro, N.; Krebs, I.

    2015-11-17

    We demonstrate that in a 3D resistive magnetohydrodynamic (MHD) simulation, for some parameters it is possible to form a stationary state in a tokamak where a saturated interchange mode in the center of the discharge drives a near helical flow pattern that acts to non-linearly sustain the configuration by adjusting the central loop voltage through a dynamo action. This could explain the physical mechanism for maintaining stationary non-sawtoothing “hybrid” discharges, often referred to as “flux-pumping”.

  2. Rare decay of the top quark t{yields}cll and single top quark production at the ILC

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

    Frank, Mariana; Turan, Ismail

    We perform a complete and detailed analysis of the flavor changing neutral current rare top quark decays t{yields}cl{sup +}l{sup -} and t{yields}c{nu}{sub i}{nu}{sub i} at one-loop level in the standard model, two Higgs doublet models (I and II), and in minimal supersymmetric standard model (MSSM). The branching ratios are very small in all models, O(10{sup -14}), except for the case of the unconstrained MSSM, where they can reach O(10{sup -6}) for e{sup +}e{sup -}, {mu}{sup +}{mu}{sup -}, and {nu}{sub i}{nu}{sub i}, and O(10{sup -5}) for {tau}{sup +}{tau}{sup -}. This branching ratio is comparable to the ones for t{yields}cV, cH. Wemore » also study the production rates of single top and the forward-backward asymmetry in e{sup +}e{sup -}{yields}tc and comment on the observability of such a signal at the International Linear Collider.« less

  3. The GBS code for tokamak scrape-off layer simulations

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

    Halpern, F.D., E-mail: federico.halpern@epfl.ch; Ricci, P.; Jolliet, S.

    2016-06-15

    We describe a new version of GBS, a 3D global, flux-driven plasma turbulence code to simulate the turbulent dynamics in the tokamak scrape-off layer (SOL), superseding the code presented by Ricci et al. (2012) [14]. The present work is driven by the objective of studying SOL turbulent dynamics in medium size tokamaks and beyond with a high-fidelity physics model. We emphasize an intertwining framework of improved physics models and the computational improvements that allow them. The model extensions include neutral atom physics, finite ion temperature, the addition of a closed field line region, and a non-Boussinesq treatment of the polarizationmore » drift. GBS has been completely refactored with the introduction of a 3-D Cartesian communicator and a scalable parallel multigrid solver. We report dramatically enhanced parallel scalability, with the possibility of treating electromagnetic fluctuations very efficiently. The method of manufactured solutions as a verification process has been carried out for this new code version, demonstrating the correct implementation of the physical model.« less

  4. Measurements of the branching fractions for B{sub (s)}{yields}D{sub (s)}{pi}{pi}{pi} and {Lambda}{sub b}{sup 0}{yields}{Lambda}{sub c}{sup +}{pi}{pi}{pi}

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

    Aaij, R.; Bauer, Th.; Beuzekom, M. van

    Branching fractions of the decays H{sub b}{yields}H{sub c}{pi}{sup -}{pi}{sup +}{pi}{sup -} relative to H{sub b}{yields}H{sub c}{pi}{sup -} are presented, where H{sub b} (H{sub c}) represents B{sup 0} (D{sup +}), B{sup -} (D{sup 0}), B{sub s}{sup 0} (D{sub s}{sup +}), and {Lambda}{sub b}{sup 0} ({Lambda}{sub c}{sup +}). The measurements are performed with the LHCb detector using 35 pb{sup -1} of data collected at {radical}(s)=7 TeV. The ratios of branching fractions are measured to be [B(B{sup 0}{yields}D{sup +}{pi}{sup -}{pi}{sup +}{pi}{sup -})]/[B(B{sup 0}{yields}D{sup +}{pi}{sup -})]=2.38{+-}0.11{+-}0.21, [B(B{sup -}{yields}D{sup 0}{pi}{sup -}{pi}{sup +}{pi}{sup -})]/[B(B{sup -}{yields}D{sup 0}{pi}{sup -})]= 1.27{+-}0.06{+-}0.11, [B(B{sub s}{sup 0}{yields}D{sub s}{sup +}{pi}{sup -}{pi}{sup +}{pi}{sup -})]/[B(B{submore » s}{sup 0}{yields}D{sub s}{sup +}{pi}{sup -})]=2.01{+-}0.37{+-}0.20, [B({Lambda}{sub b}{sup 0}{yields}{Lambda}{sub c}{sup +}{pi}{sup -} {pi}{sup +}{pi}{sup -})]/[B({Lambda}{sub b}{sup 0}{yields}{Lambda}{sub c}{sup +}{pi}{sup -})]=1.43{+-}0.16{+-}0.13 We also report measurements of partial decay rates of these decays to excited charm hadrons. These results are of comparable or higher precision than existing measurements.« less

  5. Avoidance of tearing mode locking with electro-magnetic torque introduced by feedback-based mode rotation control in DIII-D and RFX-mod

    DOE PAGES

    Okabayashi, M.; Zanca, P.; Strait, E. J.; ...

    2016-11-25

    Disruptions caused by tearing modes (TMs) are considered to be one of the most critical roadblocks to achieving reliable, steady-state operation of tokamak fusion reactors. We have demonstrated a promising scheme to avoid mode locking by utilizing the electro-magnetic (EM) torque produced with 3D coils that are available in many tokamaks. In this scheme, the EM torque is delivered to the modes by a toroidal phase shift between the externally applied field and the excited TM fields, compensating for the mode momentum loss through the interaction with the resistive wall and uncorrected error fields. Fine control of torque balance ismore » provided by a feedback scheme. We have explored this approach in two widely different devices and plasma conditions: DIII-D and RFX-mod operated in tokamak mode. In DIII-D, the plasma target was high β N in a non-circular divertor tokamak. We define β N as β N = β/(I p /aB t) (%Tm/MA), where β, I p, a, B t are the total stored plasma pressure normalized by the magnetic pressure, plasma current, plasma minor radius and toroidal magnetic field at the plasma center, respectively. The RFX-mod plasma was ohmically-heated with ultra-low safety factor in a circular limiter discharge with active feedback coils outside the thick resistive shell. The DIII-D and RFX-mod experiments showed remarkable consistency with theoretical predictions of torque balance. The application to ignition-oriented devices such as the International Thermonuclear Experimental Reactor (ITER) would expand the horizon of its operational regime. Finally, the internal 3D coil set currently under consideration for edge localized mode suppression in ITER would be well suited for this purpose.« less

  6. Avoidance of tearing mode locking with electro-magnetic torque introduced by feedback-based mode rotation control in DIII-D and RFX-mod

    NASA Astrophysics Data System (ADS)

    Okabayashi, M.; Zanca, P.; Strait, E. J.; Garofalo, A. M.; Hanson, J. M.; In, Y.; La Haye, R. J.; Marrelli, L.; Martin, P.; Paccagnella, R.; Paz-Soldan, C.; Piovesan, P.; Piron, C.; Piron, L.; Shiraki, D.; Volpe, F. A.; DIII-D, The; RFX-mod Teams

    2017-01-01

    Disruptions caused by tearing modes (TMs) are considered to be one of the most critical roadblocks to achieving reliable, steady-state operation of tokamak fusion reactors. Here we have demonstrated a promising scheme to avoid mode locking by utilizing the electro-magnetic (EM) torque produced with 3D coils that are available in many tokamaks. In this scheme, the EM torque is delivered to the modes by a toroidal phase shift between the externally applied field and the excited TM fields, compensating for the mode momentum loss through the interaction with the resistive wall and uncorrected error fields. Fine control of torque balance is provided by a feedback scheme. We have explored this approach in two widely different devices and plasma conditions: DIII-D and RFX-mod operated in tokamak mode. In DIII-D, the plasma target was high β N in a non-circular divertor tokamak. Here β N is defined as β N  =  β/(I p /aB t) (%Tm/MA), where β, I p, a, B t are the total stored plasma pressure normalized by the magnetic pressure, plasma current, plasma minor radius and toroidal magnetic field at the plasma center, respectively. The RFX-mod plasma was ohmically-heated with ultra-low safety factor in a circular limiter discharge with active feedback coils outside the thick resistive shell. The DIII-D and RFX-mod experiments showed remarkable consistency with theoretical predictions of torque balance. The application to ignition-oriented devices such as the International Thermonuclear Experimental Reactor (ITER) would expand the horizon of its operational regime. The internal 3D coil set currently under consideration for edge localized mode suppression in ITER would be well suited for this purpose.

  7. Natural Divertor Spherical Tokamak Plasmas with bean shape and ergodic limiter

    NASA Astrophysics Data System (ADS)

    Ribeiro, Celso; Herrera, Julio; Chavez, Esteban; Tritz, Kevin

    2013-10-01

    The former spherical tokamak (ST) MEDUSA (Madison EDUcation Small Aspect.ratio tokamak, R < 0.14 m, a < 0.10 m, BT < 0.5T, Ip < 40 kA, 3 ms pulse) is being recommissioned in Costa Rica Institute of Technology. The main objectives of the MEDUSA-CR project are training and to clarify several issues in relevant physics for conventional and mainly STs, including beta studies in bean-shaped ST plasmas, transport, heating and current drive via Alfvén wave, and natural divertor STs with ergodic magnetic limiter. We report here improvements in the self-consistency of these equilibrium comparisons and a preliminary study of their MHD stability beta limits. VIE-ITCR, IAEA-CRP contract 17592, National Instruments of Costa Rica.

  8. Determination of the D{sup 0}{yields}K{sup -}{pi}{sup +}{pi}{sup 0} and D{sup 0}{yields}K{sup -}{pi}{sup +}{pi}{sup +}{pi}{sup -} coherence factors and average strong-phase differences using quantum-correlated measurements

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

    Lowrey, N.; Mehrabyan, S.; Selen, M.

    The first measurements of the coherence factors (R{sub K{pi}}{sub {pi}{sup 0}} and R{sub K3{pi}}) and the average strong-phase differences ({delta}{sub D}{sup K{pi}}{sup {pi}{sup 0}} and {delta}{sub D}{sup K3{pi}}) for D{sup 0}{yields}K{sup -}{pi}{sup +}{pi}{sup 0} and D{sup 0}{yields}K{sup -}{pi}{sup +}{pi}{sup +}{pi}{sup -} are presented. These parameters can be used to improve the determination of the unitarity triangle angle {gamma} in B{sup -}{yields}DK{sup -} decays, where D is a D{sup 0} or D{sup 0} meson decaying to the same final state. The measurements are made using quantum-correlated, fully reconstructed D{sup 0}D{sup 0} pairs produced in e{sup +}e{sup -} collisions at the {psi}(3770)more » resonance. The measured values are: R{sub K{pi}}{sub {pi}{sup 0}}=0.84{+-}0.07, {delta}{sub D}{sup K{pi}}{sup {pi}{sup 0}}=(227{sub -17}{sup +14}) deg., R{sub K3{pi}}=0.33{sub -0.23}{sup +0.20}, and {delta}{sub D}{sup K3{pi}}=(114{sub -23}{sup +26}) deg. These results indicate significant coherence in the decay D{sup 0}{yields}K{sup -}{pi}{sup +}{pi}{sup 0}, whereas lower coherence is observed in the decay D{sup 0}{yields}K{sup -}{pi}{sup +}{pi}{sup +}{pi}{sup -}. The analysis also results in a small improvement in the knowledge of other D-meson parameters, in particular, the strong-phase difference for D{sup 0}{yields}K{sup -}{pi}{sup +}, {delta}{sub D}{sup K{pi}}, and the mixing parameter y.« less

  9. T-branes through 3d mirror symmetry

    NASA Astrophysics Data System (ADS)

    Collinucci, Andrés; Giacomelli, Simone; Savelli, Raffaele; Valandro, Roberto

    2016-07-01

    T-branes are exotic bound states of D-branes, characterized by mutually non-commuting vacuum expectation values for the worldvolume scalars. The M/F-theory geometry lifting D6/D7-brane configurations is blind to the T-brane data. In this paper, we make this data manifest, by probing the geometry with an M2-brane. We find that the effect of a T-brane is to deform the membrane worldvolume superpotential with monopole operators, which partially break the three-dimensional flavor symmetry, and reduce super-symmetry from {N} = 4 to {N} = 2. Our main tool is 3d mirror symmetry. Through this language, a very concrete framework is developed for understanding T-branes in M-theory. This leads us to uncover a new class of {N} = 2 quiver gauge theories, whose Higgs branches mimic those of membranes at ADE singularities, but whose Coulomb branches differ from their {N} = 4 counterparts.

  10. Snowflake divertor experiments in the DIII-D, NSTX, and NSTX-U tokamaks aimed at the development of the divertor power exhaust solution

    DOE PAGES

    Soukhanovskii, V. A.; Allen, S. L.; Fenstermacher, M. E.; ...

    2016-11-16

    Experimental results from the National Spherical Torus Experiment (NSTX), a medium-size spherical tokamak with a compact divertor, and DIII-D, a large conventional aspect ratio tokamak, demonstrate that the snowflake (SF) divertor configuration may provide a promising solution for mitigating divertor heat loads and target plate erosion compatible with core H-mode confinement in the future fusion devices, where the standard radiative divertor solution may be inadequate. In NSTX, where the initial high-power SF experiment was performed, the SF divertor was compatible with H-mode confinement, and led to the destabilization of large Edge Localized Modes (ELMs). However, a stable partial detachment ofmore » the outer strike point was also achieved where inter-ELM peak heat flux was reduced by factors 3-5, and peak ELM heat flux was reduced by up to 80% (see standard divertor). The DIII-D studies show the SF divertor enables significant power spreading in attached and radiative divertor conditions. Results include: compatibility with the core and pedestal, peak inter-ELM divertor heat flux reduction due to geometry at lower ne, and ELM energy and divertor peak heat flux reduction, especially prominent in radiative D 2-seeded SF divertor, and nearly complete power detachment and broader radiated power distribution in the radiative D 2-seeded SF divertor at PSOL = 3 - 4 MW. A variety of SF configurations can be supported by the divertor coil set in NSTX Upgrade. Edge transport modeling with the multifluid edge transport code UEDGE shows that the radiative SF divertor can successfully reduce peak divertor heat flux for the projected PSOL ≃ 9 MW case. Furthermore, the radiative SF divertor with carbon impurity provides a wider ne operating window, 50% less argon is needed in the impurity-seeded SF configuration to achieve similar q peak reduction factors (see standard divertor).« less

  11. Evidence of coupling to Global Alfv{acute e}ne Eigenmodes during Alfv{acute e}n wave current drive experiments on the Phaedrus-T tokamak

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

    Vukovic, M.; Wukitch, S.; Harper, M.

    1996-02-01

    A series of experiments designed to explore mechanisms of power deposition during Alfv{acute e}n wave current drive experiments on the Phaedrus-T tokamak has shown evidence of power deposition via mode conversion of Global Alfv{acute e}n Eigenmodes at the Alfv{acute e}n resonance. Observation of radially localized RF induced density fluctuations in the plasma and their location vs. {ital B}{sub {ital T}} is in agreement with the predictions of behaviour of GAE damping on the AR by the toroidal code LION. Furthermore, the change in the time evolution of the loop voltage, is consistent with the change of effective power deposition radius,more » {ital r}{sub PD}, and is in agreement with the density fluctuations radius. {copyright} {ital 1996 American Institute of Physics.}« less

  12. Plasma Confinement in the UCLA Electric Tokamak.

    NASA Astrophysics Data System (ADS)

    Taylor, Robert J.

    2001-10-01

    The main goal of the newly constructed large Electric Tokamak (R = 5 m, a = 1 m, BT < 0.25 T) is to access an omnigeneous, unity beta(S.C. Cowley, P.K. Kaw, R.S. Kelly, R.M. Kulsrud, Phys. fluids B 3 (1991) 2066.) plasma regime. The design goal was to achieve good confinement at low magnetic fields, consistent with the high beta goal. To keep the program cost down, we adopted the use of ICRF as the primary heating source. Consequently, antenna surfaces covering 1/2 of the surface of the tokamak has been prepared for heating and current drive. Very clean hydrogenic plasmas have been achieved with loop voltage below 0.7 volt and densities 3 times above the Murakami limit, n(0) > 8 x 10^12 cm-3 when there is no MHD activity. The electron temperature, derived from the plasma conductivity is > 250 eV with a central electron energy confinement time > 350 msec in ohmic conditions. The sawteeth period is 50 msec. Edge plasma rotation is induced by plasma biasing via electron injection in an analogous manner to that seen in CCT(R.J. Taylor, M.L. Brown, B.D. Fried, H. Grote, J.R. Liberati, G.J. Morales, P. Pribyl, D. Darrow, and M. Ono. Phys. Rev Lett. 63 2365 1989.) and the neoclassical bifurcation is close to that described by Shaing et al(K.C. Shaing and E.C. Crume, Phys. Rev. Lett. 63 2369 (1989).). In the ohmic phase the confinement tends to be MHD limited. The ICRF heating eliminates the MHD disturbances. Under second harmonic heating conditions, we observe an internal confinement peaking characterized by doubling of the core density and a corresponding increase in the central electron temperature. Charge exchange data, Doppler data in visible H-alpha light, and EC radiation all indicate that ICRF heating works much better than expected. The major effort is focused on increasing the power input and controlling the resulting equilibrium. This task appears to be easy since our current pulses are approaching the 3 second mark without RF heating or current drive. Our

  13. Homoclinic tangle of the ideal separatrix in the DIII-D tokamak from (30, 10) + (40, 10) perturbation

    NASA Astrophysics Data System (ADS)

    Punjabi, Alkesh

    2014-12-01

    Trajectories of magnetic field lines are a 1½ degree of freedom Hamiltonian system. The perturbed separatrix in a divertor tokamak is radically different from the unperturbed one. This is because magnetic asymmetries cause the separatrix to form extremely complicated structures called homoclinic tangles. The shape of flux surfaces in the edge region of divertor tokamaks such as the DIII (J. L. Luxon and L. G. Davis, Fusion Technol. 8, 441 (1985)) is fundamentally different from near-circular. Recently, a new method is developed to calculate the homoclinic tangle and lobes of the separatrix of divertor tokamaks in physical space (A. Punjabi and A. Boozer, Phys. Lett. A 378, 2410 (2014)). This method is based on three elements: preservation of the two invariants—symplectic and topological neighborhood—and a new set of canonical coordinates called the natural canonical coordinates. The very complicated shape of edge surfaces can be represented very accurately and very realistically in these new coordinates (A. Punjabi and H. Ali, Phys. Plasmas 15, 122502 (2008); A. Punjabi, Nucl. Fusion 49, 115020 (2009)). A symplectic map in the new coordinates can advance the separatrix manifold forward and backward in time. Every time the two manifolds meet in a fixed poloidal plane, they intersect and form homoclinic tangle to preserve the two invariants. The new coordinates can be mapped to physical space and the dynamical evolution of the homoclinic tangle can be seen and pictured in physical space. Here, the new method is applied to the DIII-D tokamak to study the basic features of the homoclinic tangle of the unperturbed separatrix from two Fourier components, which represent the peeling-ballooning modes of equal amplitude and no radial dependence, and the results are analyzed. Homoclinic tangle has a very complicated structure and becomes extremely complicated for as the lines take more toroidal turns, especially near the X-point. Homoclinic tangle is the most

  14. Dust measurements in tokamaks (invited).

    PubMed

    Rudakov, D L; Yu, J H; Boedo, J A; Hollmann, E M; Krasheninnikov, S I; Moyer, R A; Muller, S H; Pigarov, A Yu; Rosenberg, M; Smirnov, R D; West, W P; Boivin, R L; Bray, B D; Brooks, N H; Hyatt, A W; Wong, C P C; Roquemore, A L; Skinner, C H; Solomon, W M; Ratynskaia, S; Fenstermacher, M E; Groth, M; Lasnier, C J; McLean, A G; Stangeby, P C

    2008-10-01

    Dust production and accumulation present potential safety and operational issues for the ITER. Dust diagnostics can be divided into two groups: diagnostics of dust on surfaces and diagnostics of dust in plasma. Diagnostics from both groups are employed in contemporary tokamaks; new diagnostics suitable for ITER are also being developed and tested. Dust accumulation in ITER is likely to occur in hidden areas, e.g., between tiles and under divertor baffles. A novel electrostatic dust detector for monitoring dust in these regions has been developed and tested at PPPL. In the DIII-D tokamak dust diagnostics include Mie scattering from Nd:YAG lasers, visible imaging, and spectroscopy. Laser scattering is able to resolve particles between 0.16 and 1.6 microm in diameter; using these data the total dust content in the edge plasmas and trends in the dust production rates within this size range have been established. Individual dust particles are observed by visible imaging using fast framing cameras, detecting dust particles of a few microns in diameter and larger. Dust velocities and trajectories can be determined in two-dimension with a single camera or three-dimension using multiple cameras, but determination of particle size is challenging. In order to calibrate diagnostics and benchmark dust dynamics modeling, precharacterized carbon dust has been injected into the lower divertor of DIII-D. Injected dust is seen by cameras, and spectroscopic diagnostics observe an increase in carbon line (CI, CII, C(2) dimer) and thermal continuum emissions from the injected dust. The latter observation can be used in the design of novel dust survey diagnostics.

  15. Mitigation of Alfvén activity in a tokamak by externally applied static 3D fields.

    PubMed

    Bortolon, A; Heidbrink, W W; Kramer, G J; Park, J-K; Fredrickson, E D; Lore, J D; Podestà, M

    2013-06-28

    The application of static magnetic field perturbations to a tokamak plasma is observed to alter the dynamics of high-frequency bursting Alfvén modes that are driven unstable by energetic ions. In response to perturbations with an amplitude of δB/B∼0.01 at the plasma boundary, the mode amplitude is reduced, the bursting frequency is increased, and the frequency chirp is smaller. For modes of weaker bursting character, the magnetic perturbation induces a temporary transition to a saturated continuous mode. Calculations of the perturbed distribution function indicate that the 3D perturbation affects the orbits of fast ions that resonate with the bursting modes. The experimental evidence represents an important demonstration of the possibility of controlling fast-ion instabilities through "phase-space engineering" of the fast-ion distribution function, by means of externally applied perturbation fields.

  16. Effect of the Yield Stress and r-value Distribution on the Earing Profile of Cup Drawing with Yld2000-2d Yield Function

    NASA Astrophysics Data System (ADS)

    Lou, Yanshan; Bae, Gihyun; Lee, Changsoo; Huh, Hoon

    2010-06-01

    This paper deals with the effect of the yield stress and r-value distribution on the earing in the cup drawing. The anisotropic yield function, Yld2000-2d yield function, is selected to describe the anisotropy of two metal sheets, 719B and AA5182-O. The tool dimension is referred from the Benchmark problem of NUMISHEET'2002. The Downhill Simplex method is applied to identify the anisotropic coefficients in Yld2000-2d yield function. Simulations of the drawing process are performed to investigate the earing profile of two materials. The earing profiles obtained from simulations are compared with the analytical model developed by Hosford and Caddell. Simulations are conducted with respect to the change of the yield stress and r-value distribution, respectively. The correlation between the anisotropy and the earing tendency is investigated based on simulation data. Finally, the earing mechanism is analyzed through the deformation process of the blank during the cup deep drawing. It can be concluded that ears locate at angular positions with lower yield stress and higher r-value while the valleys appear at the angular position with higher yield stress and lower r-value. The effect of the yield stress distribution is more important for the cup height distribution than that of the r-value distribution.

  17. Helical flow in RFX-mod tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Piron, L.; Zaniol, B.; Bonfiglio, D.; Carraro, L.; Kirk, A.; Marrelli, L.; Martin, R.; Piron, C.; Piovesan, P.; Zuin, M.

    2017-05-01

    This work presents the first evidence of helical flow in RFX-mod q(a)  <  2 tokamak plasmas. The flow pattern is characterized by the presence of convective cells with m  =  1 and n  =  1 periodicity in the poloidal and toroidal directions, respectively. A similar helical flow deformation has been observed in the same device when operated as a reversed field pinch (RFP). In RFP plasmas, the flow dynamic is tailored by the innermost resonant m  =  1, n  =  7 tearing mode, which sustains the magnetic field configuration through the dynamo mechanism (Bonomo et al 2011 Nucl. Fusion 51 123007). By contrast, in the tokamak experiments presented here, it is strongly correlated with the m  =  1, n  =  1 MHD activity. A helical deformation of the flow pattern, associated with the deformation of the magnetic flux surfaces, is predicted by several codes, such as Specyl (Bonfiglio et al 2005 Phys. Rev. Lett. 94 145001), PIXIE3D (Chacón et al 2008 Phys. Plasmas 15 056103), NIMROD (King et al 2012 Phys. Plasmas 19 055905) and M3D-C1 (Jardin et al 2015 Phys. Rev. Lett. 115 215001). Among them, the 3D fully non-linear PIXIE3D has been used to calculate synthetic flow measurements, using a 2D flow modelling code. Inputs to the code are the PIXIE3D flow maps, the ion emission profiles as calculated by a 1D collisional radiative impurity transport code (Carraro et al 2000 Plasma Phys. Control. Fusion 42 731) and a synthetic diagnostic with the same geometry installed in RFX-mod. Good agreement between the synthetic and the experimental flow behaviour has been obtained, confirming that the flow oscillations observed with the associated convective cells are a signature of helical flow.

  18. Modular coils and finite-β operation of a quasi-axially symmetric tokamak

    NASA Astrophysics Data System (ADS)

    Drevlak, M.

    1998-09-01

    Quasi-axially symmetric tokamaks (QA tokamaks) are an extension of the conventional tokamak concept. In these devices the magnetic field strength is independent of the generalized toroidal magnetic co-ordinate even though the cross-sectional shape changes. An optimized plasma equilibrium belonging to the class of QA tokamaks has been proposed by Nührenberg. It features the small aspect ratio of a tokamak while allowing part of the rotational transform to be generated by the external field. In this article, two particular aspects of the viability of QA tokamaks are explored, namely the feasibility of modular coils and the possibility of maintaining quasi-axial symmetry in the free-boundary equilibria obtained with the coils found. A set of easily feasible modular coils for the configuration is presented. It was designed using the extended version of the NESCOIL code (Merkel, P., Nucl. Fusion 27 (1987) 867). Using this coil system, free-boundary calculations of the plasma equilibrium were carried out using the NEMEC code (Hirshman, S.P., Van Rij, W.I., Merkel, P., Comput. Phys. Commun. 43 (1986) 143). It is observed that the effects of finite β and net toroidal plasma current can be compensated for with good precision by applying a vertical magnetic field and by separately adjusting the currents of the modular coils. A set of fully three dimensional (3-D) auxiliary coils is proposed to exert control on the rotational transform in the plasma. Deterioration of the quasi-axial symmetry induced by the auxiliary coils can be avoided by adequate adjustment of the currents in the primary coils. Finally, the neoclassical transport properties of the configuration are examined. It is observed that optimization with respect to confinement of the alpha particles can be maintained at operation with finite toroidal current if the aforementioned corrective measures are used. In this case, the neoclassical behaviour is shown to be very similar to that of a conventional tokamak.

  19. Effects of Hot Limiter Biasing on Tokamak Runaway Discharges

    NASA Astrophysics Data System (ADS)

    Salar Elahi, A.; Ghoranneviss, M.; Ghanbari, M. R.

    2013-10-01

    In this research hot limiter biasing effects on the Runaway discharges were investigated. First wall of the tokamak reactors can affects serious damage due to the high energy runaway electrons during a major disruption and therefore its life time can be reduced. Therefore, it is important to find methods to decrease runaway electron generation and their energy. Tokamak limiter biasing is one of the methods for controlling the radial electric field and can induce a transition to an improved confinement state. In this article generation of runaway electrons and the energy they can obtain will be investigated theoretically. Moreover, in order to apply radial biasing an emissive limiter biasing is utilized. The biased limiter can apply +380 V in the status of cold and hot to the plasma and result in the increase of negative bias current in hot status. In fact, in this experiment we try to decrease the generation of runaway electrons and their energy by using emissive limiter biasing inserted on the IR-T1 tokamak. The mean energy of these electrons was obtained by spectroscopy of hard X-ray. Also, the plasma current center shift was measured from the vertical field coil characteristics in presence of limiter biasing. The calculation is made focusing on the vertical field coil current and voltage changes due to a horizontal displacement of plasma column.

  20. 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.

  1. Design and development of ultra-wideband 3 dB hybrid coupler for Ion cyclotron resonance frequency heating in tokamak.

    PubMed

    Yadav, Rana Pratap; Kumar, Sunil; Kulkarni, S V

    2014-04-01

    Design and development of a high power ultra-wideband, 3 dB tandem hybrid coupler is presented and its application in ICRF heating of the tokamak is discussed. In order to achieve the desired frequency band of 38-112 MHz and 200 kW power handling capability, the 3 dB hybrid coupler is developed using two 3-element 8.34 ± 0.2 dB coupled lines sections in tandem. In multi-element coupled lines, junctions are employed for the joining of coupled elements that produce the undesirable reactance called junction discontinuity effect. The effect becomes prominent in the high power multi-element coupled lines for high frequency (HF) and very high frequency(VHF) applications because of larger structural dimensions. Junction discontinuity effect significantly deteriorates coupling and output performance from the theoretical predictions. For the analysis of junction discontinuity effect and its compensation, a theoretical approach has been developed and generalized for n-element coupled lines section. The theory has been applied in the development of the 3 dB hybrid coupler. The fabricated hybrid coupler has been experimentally characterized using vector network analyzer and obtained results are found in good agreement with developed theory.

  2. Steady State Advanced Tokamak (SSAT): The mission and the machine

    NASA Astrophysics Data System (ADS)

    Thomassen, K.; Goldston, R.; Nevins, B.; Neilson, H.; Shannon, T.; Montgomery, B.

    1992-03-01

    Extending the tokamak concept to the steady state regime and pursuing advances in tokamak physics are important and complementary steps for the magnetic fusion energy program. The required transition away from inductive current drive will provide exciting opportunities for advances in tokamak physics, as well as important impetus to drive advances in fusion technology. Recognizing this, the Fusion Policy Advisory Committee and the U.S. National Energy Strategy identified the development of steady state tokamak physics and technology, and improvements in the tokamak concept, as vital elements in the magnetic fusion energy development plan. Both called for the construction of a steady state tokamak facility to address these plan elements. Advances in physics that produce better confinement and higher pressure limits are required for a similar unit size reactor. Regimes with largely self-driven plasma current are required to permit a steady-state tokamak reactor with acceptable recirculating power. Reliable techniques of disruption control will be needed to achieve the availability goals of an economic reactor. Thus the central role of this new tokamak facility is to point the way to a more attractive demonstration reactor (DEMO) than the present data base would support. To meet the challenges, we propose a new 'Steady State Advanced Tokamak' (SSAT) facility that would develop and demonstrate optimized steady state tokamak operating mode. While other tokamaks in the world program employ superconducting toroidal field coils, SSAT would be the first major tokamak to operate with a fully superconducting coil set in the elongated, divertor geometry planned for ITER and DEMO.

  3. Progress Toward Steady State Tokamak Operation Exploiting the high bootstrap current fraction regime

    NASA Astrophysics Data System (ADS)

    Ren, Q.

    2015-11-01

    Recent DIII-D experiments have advanced the normalized fusion performance of the high bootstrap current fraction tokamak regime toward reactor-relevant steady state operation. The experiments, conducted by a joint team of researchers from the DIII-D and EAST tokamaks, developed a fully noninductive scenario that could be extended on EAST to a demonstration of long pulse steady-state tokamak operation. Fully noninductive plasmas with extremely high values of the poloidal beta, βp >= 4 , have been sustained at βT >= 2 % for long durations with excellent energy confinement quality (H98y,2 >= 1 . 5) and internal transport barriers (ITBs) generated at large minor radius (>= 0 . 6) in all channels (Te, Ti, ne, VTf). Large bootstrap fraction (fBS ~ 80 %) has been obtained with high βp. ITBs have been shown to be compatible with steady state operation. Because of the unusually large ITB radius, normalized pressure is not limited to low βN values by internal ITB-driven modes. βN up to ~4.3 has been obtained by optimizing the plasma-wall distance. The scenario is robust against several variations, including replacing some on-axis with off-axis neutral beam injection (NBI), adding electron cyclotron (EC) heating, and reducing the NBI torque by a factor of 2. This latter observation is particularly promising for extension of the scenario to EAST, where maximum power is obtained with balanced NBI injection, and to a reactor, expected to have low rotation. However, modeling of this regime has provided new challenges to state-of-the-art modeling capabilities: quasilinear models can dramatically underpredict the electron transport, and the Sauter bootstrap current can be insufficient. The analysis shows first-principle NEO is in good agreement with experiments for the bootstrap current calculation and ETG modes with a larger saturated amplitude or EM modes may provide the missing electron transport. Work supported in part by the US DOE under DE-FC02-04ER54698, DE-AC52-07NA

  4. Catalyzed D-D stellarator reactor

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

    Sheffield, John; Spong, Donald A.

    The advantages of using the catalyzed deuterium-deuterium (D-D) approach for a fusion reactor—lower and less energetic neutron flux and no need for a tritium breeding blanket—have been evaluated in previous papers, giving examples of both tokamak and stellarator reactors. This paper presents an update for the stellarator example, taking account of more recent empirical transport scaling results and design studies of lower-aspect-ratio stellarators. We use a modified version of the Generic Magnetic Fusion Reactor model to cost a stellarator-type reactor. Recently, this model has been updated to reflect the improved science and technology base and costs in the magnetic fusionmore » program. Furthermore, it is shown that an interesting catalyzed D-D, stellarator power plant might be possible if the following parameters could be achieved: R/ ≈ 4, required improvement factor to ISS04 scaling, F R = 0.9 to 1.15, ≈ 8.0% to 11.5%, Z eff ≈ 1.45 plus a relativistic temperature correction, fraction of fast ions lost ≈ 0.07, B m ≈ 14 to 16 T, and R ≈ 18 to 24 m.« less

  5. Catalyzed D-D stellarator reactor

    DOE PAGES

    Sheffield, John; Spong, Donald A.

    2016-05-12

    The advantages of using the catalyzed deuterium-deuterium (D-D) approach for a fusion reactor—lower and less energetic neutron flux and no need for a tritium breeding blanket—have been evaluated in previous papers, giving examples of both tokamak and stellarator reactors. This paper presents an update for the stellarator example, taking account of more recent empirical transport scaling results and design studies of lower-aspect-ratio stellarators. We use a modified version of the Generic Magnetic Fusion Reactor model to cost a stellarator-type reactor. Recently, this model has been updated to reflect the improved science and technology base and costs in the magnetic fusionmore » program. Furthermore, it is shown that an interesting catalyzed D-D, stellarator power plant might be possible if the following parameters could be achieved: R/ ≈ 4, required improvement factor to ISS04 scaling, F R = 0.9 to 1.15, ≈ 8.0% to 11.5%, Z eff ≈ 1.45 plus a relativistic temperature correction, fraction of fast ions lost ≈ 0.07, B m ≈ 14 to 16 T, and R ≈ 18 to 24 m.« less

  6. Tritium pellet injector for the tokamak fusion test reactor

    NASA Astrophysics Data System (ADS)

    Gouge, M. J.; Baylor, L. R.; Combs, S. K.; Fisher, P. W.; Foust, C. R.; Milora, S. L.

    The tritium pellet injector (TPI) for the Tokamak Fusion Test Reactor (TFTR) will provide a tritium pellet fueling capability with pellet speeds in the 1- to 3-km/s range for the TFTR deuterium-tritium (D-T) plasma phase. An existing deuterium pellet injector (DPI) was modified at Oak Ridge National Laboratory (ORNL) to provide a four-shot, tritium-compatible, pipe-gun configuration with three upgraded single-stage pneumatic guns and a two-stage light gas gun driver. The TPI was designed for frozen pellets ranging in size from 3 to 4 mm in diameter in arbitrarily programmable firing sequences at tritium pellet speeds up to approximately 1.5 km/s for the three single-stage drivers and 2.5 to 3 km/s for the two-stage driver. Injector operation is controlled by a programmable logic controller (PLC). The new pipe-gun injector assembly was installed in the modified DPI guard vacuum box, and modifications were also made to the internals of the DPI vacuum injection line, including a new pellet diagnostics package. Assembly of these modified parts with existing DPI components was then completed and the TPI was tested at ORNL with deuterium pellets. Results of the testing program at ORNL are described. The TPI has been installed and operated on TFTR in support of the FY-92 deuterium plasma run period. In 1993, the tritium pellet injector will be retrofitted with a D-T fuel manifold and tritium gloveboxes and integrated into TFTR tritium processing systems to provide full tritium pellet capability.

  7. Public Data Set: Impedance of an Intense Plasma-Cathode Electron Source for Tokamak Plasma Startup

    DOE Data Explorer

    Hinson, Edward T. [University of Wisconsin-Madison] (ORCID:000000019713140X); Barr, Jayson L. [University of Wisconsin-Madison] (ORCID:0000000177685931); Bongard, Michael W. [University of Wisconsin-Madison] (ORCID:0000000231609746); Burke, Marcus G. [University of Wisconsin-Madison] (ORCID:0000000176193724); Fonck, Raymond J. [University of Wisconsin-Madison] (ORCID:0000000294386762); Perry, Justin M. [University of Wisconsin-Madison] (ORCID:0000000171228609)

    2016-05-31

    This data set contains openly-documented, machine readable digital research data corresponding to figures published in E.T. Hinson et al., 'Impedance of an Intense Plasma-Cathode Electron Source for Tokamak Plasma Startup,' Physics of Plasmas 23, 052515 (2016).

  8. Evidence of final-state suppression of high-p{_ T} hadrons in Au + Au collisions using d + Au measurements at RHIC

    NASA Astrophysics Data System (ADS)

    Back, B. B.; Baker, M. D.; Ballintijn, M.; Barton, D. S.; Becker, B.; Betts, R. R.; Bickley, A. A.; Bindel, R.; Busza, W.; Carroll, A.; Decowski, M. P.; García, E.; Gburek, T.; George, N.; Gulbrandsen, K.; Gushue, S.; Halliwell, C.; Hamblen, J.; Harrington, A. S.; Henderson, C.; Hofman, D. J.; Hollis, R. S.; Hołyński, R.; Holzman, B.; Iordanova, A.; Johnson, E.; Kane, J. L.; Khan, N.; Kulinich, P.; Kuo, C. M.; Lee, J. W.; Lin, W. T.; Manly, S.; Mignerey, A. C.; Nouicer, R.; Olszewski, A.; Pak, R.; Park, I. C.; Pernegger, H.; Reed, C.; Roland, C.; Roland, G.; Sagerer, J.; Sarin, P.; Sedykh, I.; Skulski, W.; Smith, C. E.; Steinberg, P.; Stephans, G. S. F.; Sukhanov, A.; Tonjes, M. B.; Trzupek, A.; Vale, C.; van Nieuwenhuizen, G. J.; Verdier, R.; Veres, G. I.; Wolfs, F. L. H.; Wosiek, B.; Woźniak, K.; Wysłouch, B.; Zhang, J.

    Transverse momentum spectra of charged hadrons with pT < 6 GeV/c have been measured near mid-rapidity (0.2 < ɛ < 1.4) by the PHOBOS experiment at RHIC in Au + Au and d + Au collisions at {√ {s{NN}} = {200 GeV}}. The spectra for different collision centralities are compared to {p + ¯ {p}} collisions at the same energy. The resulting nuclear modification factor for central Au + Au collisions shows evidence of strong suppression of charged hadrons in the high-pT region (>2 GeV/c). In contrast, the d + Au nuclear modification factor exhibits no suppression of the high-pT yields. These measurements suggest a large energy loss of the high-pT particles in the highly interacting medium created in the central Au + Au collisions. The lack of suppression in d + Au collisions suggests that it is unlikely that initial state effects can explain the suppression in the central Au + Au collisions. PACS: 25.75.-q

  9. A Research Program of Spherical Tokamak in China

    NASA Astrophysics Data System (ADS)

    He, Ye-xi

    2002-08-01

    The mission of this program is to explore the spherical torus plasma with a SUNIST spherical tokamak. Main experiments in the start phase will be involved with breakdown and plasma current set-up with a mode of saving volt-second and without ohmic heating system, equilibrium and instability, current driving, heating and profile modification. The SUNIST is a university-scale conceptual spherical tokamak, with R = 0.3 m, A 1.3, Ip ~ 50 kA, BT < 0.15 T, and PRF = 100 kW. The only peculiarity of SUNIST is that there is a toroidal insulating break along the outer wall of vacuum vessel. The expected that advantages of this arrangement are helpful not only for saving flux swing, but also for having a deep understanding of what will influence the discharge startup and globe performances of plasma under different conditions of strong vessel eddy and ECR power assistance. Of course, the vessel structure of cross seal will be at a great risk of controlling vacuum quality, although we have achieved positive results on simulation test and vacuum vessel test.

  10. The Research Progress of the J-TEXT Tokamak

    NASA Astrophysics Data System (ADS)

    Zhuang, Ge; Wang, Zhijiang; Ding, Yonghua; Zhang, Ming; Yang, Zhoujun; Gao, Li; Zhang, Xiaoqing; Hu, Xiwei; Pan, Yuan

    2010-11-01

    In 2004, the TEXT-U tokamak was disassembled and shipped to China, and later on settle down in Huazhong University of Science and Technology. The machine was renamed as the Joint TEXT (J-TEXT) tokamak and obtained its first plasma in 2007. The typical J-TEXT Ohmic discharge was performed in the limiter configuration with the main parameters as follows: major radius R=1.05 m, minor radius a=0.27m, toroidal magnetic field BT=2.2T, plasma current Ip>200kA, line-averaged density ne˜ 2-3 . 1019/m^3, and electron temperature Te0˜ 700eV. Up till now, a few diagnostic systems used to facilitate routine operation and experimental studies were designed and developed. Benefiting from these diagnostic tools, the observation of MHD activities and the statistical analysis of disruption events were done. And measurements of the electrostatic fluctuations in the edge region and conditional analysis of the intermittent burst events near the LCFS were also made as well. The preliminary results will be presented in detail in the meeting.

  11. Recent Doppler Backscattering results from EAST tokamak

    NASA Astrophysics Data System (ADS)

    Zhou, Chu; Liu, Adi; Zhang, Xiaohui; Hu, Jianqiang; Wang, Mingyuan; Yu, Changxuan; Liu, Wandong; Li, Hong; Lan, Tao; Sun, Xuan; Xie, Jinlin; Ding, Weixing; CAS Key Laboratory of Geospace Environment, University of Science and Technology of China Team; Department of Physics and Astronomy, University of California at Los Angeles Collaboration

    2013-10-01

    A Doppler reflectometer system has recently been installed in the EAST tokamak. It includes two separated systems, one for Q-band and the other for V-band. The optical system consists of a fixed flat mirror and a steerable parabolic mirror, which enabling the measurement of perpendicular wave number in the range of 4-22/cm, with the wave number resolution around 2/cm, while the radial location can cover the whole minor radius for L mode and the whole pedestal for H mode on EAST. A 2D Gaussion Ray tracing code is used to calculate the scattering location, the perpendicular wave number and the resolution. In EAST last experimental campaign the Doppler shifted signals have been obtained and the radial profiles of the perpendicular propagation velocity during L-mode and H-mode are calculated. The Er evolution during L-H and H-L transition have also been measured. The two separated systems are also used as a poloidal coherent system together to study the GAM in EAST tokamak.

  12. An efficient transport solver for tokamak plasmas

    DOE PAGES

    Park, Jin Myung; Murakami, Masanori; St. John, H. E.; ...

    2017-01-03

    A simple approach to efficiently solve a coupled set of 1-D diffusion-type transport equations with a stiff transport model for tokamak plasmas is presented based on the 4th order accurate Interpolated Differential Operator scheme along with a nonlinear iteration method derived from a root-finding algorithm. Here, numerical tests using the Trapped Gyro-Landau-Fluid model show that the presented high order method provides an accurate transport solution using a small number of grid points with robust nonlinear convergence.

  13. Homoclinic tangle of the ideal separatrix in the DIII-D tokamak from (30, 10) + (40, 10) perturbation

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

    Punjabi, Alkesh

    Trajectories of magnetic field lines are a 1½ degree of freedom Hamiltonian system. The perturbed separatrix in a divertor tokamak is radically different from the unperturbed one. This is because magnetic asymmetries cause the separatrix to form extremely complicated structures called homoclinic tangles. The shape of flux surfaces in the edge region of divertor tokamaks such as the DIII (J. L. Luxon and L. G. Davis, Fusion Technol. 8, 441 (1985)) is fundamentally different from near-circular. Recently, a new method is developed to calculate the homoclinic tangle and lobes of the separatrix of divertor tokamaks in physical space (A. Punjabimore » and A. Boozer, Phys. Lett. A 378, 2410 (2014)). This method is based on three elements: preservation of the two invariants—symplectic and topological neighborhood—and a new set of canonical coordinates called the natural canonical coordinates. The very complicated shape of edge surfaces can be represented very accurately and very realistically in these new coordinates (A. Punjabi and H. Ali, Phys. Plasmas 15, 122502 (2008); A. Punjabi, Nucl. Fusion 49, 115020 (2009)). A symplectic map in the new coordinates can advance the separatrix manifold forward and backward in time. Every time the two manifolds meet in a fixed poloidal plane, they intersect and form homoclinic tangle to preserve the two invariants. The new coordinates can be mapped to physical space and the dynamical evolution of the homoclinic tangle can be seen and pictured in physical space. Here, the new method is applied to the DIII-D tokamak to study the basic features of the homoclinic tangle of the unperturbed separatrix from two Fourier components, which represent the peeling-ballooning modes of equal amplitude and no radial dependence, and the results are analyzed. Homoclinic tangle has a very complicated structure and becomes extremely complicated for as the lines take more toroidal turns, especially near the X-point. Homoclinic tangle is the most

  14. Control and Data Acquisition for the Spherical Tokamak MEDUSA-CR

    NASA Astrophysics Data System (ADS)

    Soto, Christian; Gonzalez, Jeferson; Carvajal, Johan; Ribeiro, Celso

    2013-10-01

    The former spherical tokamak (ST) MEDUSA (Madison EDUcation Small Aspect.ratio tokamak, R < 0.14 m, a < 0.10 m, BT < 0.5 T, Ip < 40 kA, 3 ms pulse) is being recommissioned in Costa Rica Institute of Technology. The main objectives of the MEDUSA-CR project are training and to clarify several issues in relevant physics for conventional and mainly STs, including beta studies in bean-shaped ST plasmas, transport, heating and current drive via Alfvén wave, and natural divertor STs with ergodic magnetic limiter. We present here the control and data acquisition systems for MEDUSA-CR device which are based on National Instruments (NI) software (LabView) and hardware on loan to our laboratory via NI-Costa Rica. The interface with the energy, gas fueling, and security systems are also presented. VIE-ITCR, IAEA-CRP contract 17592, National Instruments of Costa Rica.

  15. Multispectroscopic methods reveal different modes of interaction of anti cancer drug mitoxantrone with Poly(dG-dC).Poly(dG-dC) and Poly(dA-dT).Poly(dA-dT).

    PubMed

    Awasthi, Pamita; Dogra, Shilpa; Barthwal, Ritu

    2013-10-05

    The interaction of mitoxantrone with alternating Poly(dG-dC).Poly(dG-dC) and Poly(dA-dT).Poly(dA-dT) duplex has been studied by absorption, fluorescence and Circular Dichroism (CD) spectroscopy at Drug to Phosphate base pair ratios D/P=20.0-0.04. Binding to GC polymer occurs in two distinct modes: partial stacking characterized by red shifts of 18-23nm at D/P=0.2-0.8 and external binding at D/P=1.0-20.0 whereas that to AT polymer occurs externally in the entire range of D/P. The binding constant and number of binding sites is 3.7×10(5)M(-1), 0.3 and 1.3× 10(4)M(-1), 1.5 in GC and AT polymers, respectively at low D/P ratios. CD binding isotherms show breakpoints at D/P=0.1, 0.5 and 0.25, 0.5 in GC and AT polymers, respectively. The intrinsic CD bands indicate that the distortions in GC polymer are significantly higher than that in AT polymer. Docking studies show partial insertion of mitoxantrone rings between to GC base pairs in alternating GC polymer. Side chains of mitoxantrone interact specifically with base pairs and DNA backbone. The studies are relevant to the understanding of suppression or inhibition of DNA cleavage on formation of ternary complex with topoisomerase-II enzyme and hence the anti cancer action. Copyright © 2013 Elsevier B.V. All rights reserved.

  16. Distortions in 2p4d Partial Fluorescence yield for 4d elements

    NASA Astrophysics Data System (ADS)

    Price, Alexander; de Groot, Frank; Datta, Trinanjan

    2014-03-01

    X-ray absorption spectroscopy (XAS) is a standard tool to determine the electronic structure of molecules and materials. CTM4XAS and CTM4RIXS are semi-empirical programs to analyze transition metal L - and M - edge transitions by evaluating the effects of crystal field and charge transfer parameters on the atomic multiplets. We compute and compare the XAS and the fluorescence yield (FY) XAS, of the 3d and 4d transition metal ions. In the case of 2p edges of 3d elements Auger decay dominates and sets the time scale. The 2p3d X -ray emission spectra (XES) accounts for approximately 80% of the radiative decay. The 2p3d partial FY is distorted and because it dominates the FY, the total FY is also distorted. For the 4d elements the 2p4d XES decay is approximately 10% of 2p3d XES decay, implying that (the energy-constant) core-core XES and Auger channels dominate the decay. The computed 2p4d partial FY -XAS spectra are different from the 2p XAS. Although 2p4d partial FY is distorted, the total FY is not because it is dominated by 2p3d XES. We also find that the 2p3s and 2p4s XES channels contribute less than 1% and can be neglected. Cottrell Research Corporation.

  17. Energy balance in TM-1-MH Tokamak (ohmical heating)

    NASA Astrophysics Data System (ADS)

    Stoeckel, J.; Koerbel, S.; Kryska, L.; Kopecky, V.; Dadalec, V.; Datlov, J.; Jakubka, K.; Magula, P.; Zacek, F.; Pereverzev, G. V.

    1981-10-01

    Plasma in the TM-1-MH Tokamak was experimentally studied in the parameter range: tor. mg. field B = 1,3 T, plasma current I sub p = 14 kA, electron density N sub E 3.10 to the 19th power cubic meters. The two numerical codes are available for the comparison with experimental data. TOKATA-code solves simplified energy balance equations for electron and ion components. TOKSAS-code solves the detailed energy balance of the ion component.

  18. Helical variation of density profiles and fluctuations in the tokamak pedestal with applied 3D fields and implications for confinement

    NASA Astrophysics Data System (ADS)

    Wilcox, R. S.; Rhodes, T. L.; Shafer, M. W.; Sugiyama, L. E.; Ferraro, N. M.; Lyons, B. C.; McKee, G. R.; Paz-Soldan, C.; Wingen, A.; Zeng, L.

    2018-05-01

    Small 3D perturbations to the magnetic field in DIII-D ( δB /B ˜2 ×10-4 ) result in large modulations of density fluctuation amplitudes in the pedestal, which are shown using Doppler backscattering measurements to vary by a factor of 2. Helical perturbations of equilibrium density within flux surfaces have previously been observed in the pedestal of DIII-D plasmas when 3D fields are applied and were correlated with density fluctuation asymmetries in the pedestal. These intra-surface density and pressure variations are shown through two fluid MHD modeling studies using the M3D-C1 code to be due to the misalignment of the density and temperature equilibrium iso-surfaces in the pedestal region. This modeling demonstrates that the phase shift between the two iso-surfaces corresponds to the diamagnetic direction of the two species, with the mass density surfaces shifted in the ion diamagnetic direction relative to the temperature and magnetic flux iso-surfaces. The resulting pedestal density, potential, and turbulence asymmetries within flux surfaces near the separatrix may be at least partially responsible for several poorly understood phenomena that occur with the application of 3D fields in tokamaks, including density pump out and the increase in power required to transition from L- to H-mode.

  19. 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.

  20. 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

  1. Simulation of magnetic island dynamics under resonant magnetic perturbation with the TEAR code and validation of the results on T-10 tokamak data

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

    Ivanov, N. V.; Kakurin, A. M.

    2014-10-15

    Simulation of the magnetic island evolution under Resonant Magnetic Perturbation (RMP) in rotating T-10 tokamak plasma is presented with intent of TEAR code experimental validation. In the T-10 experiment chosen for simulation, the RMP consists of a stationary error field, a magnetic field of the eddy current in the resistive vacuum vessel and magnetic field of the externally applied controlled halo current in the plasma scrape-off layer (SOL). The halo-current loop consists of a rail limiter, plasma SOL, vacuum vessel, and external part of the circuit. Effects of plasma resistivity, viscosity, and RMP are taken into account in the TEARmore » code based on the two-fluid MHD approximation. Radial distribution of the magnetic flux perturbation is calculated with account of the externally applied RMP. A good agreement is obtained between the simulation results and experimental data for the cases of preprogrammed and feedback-controlled halo current in the plasma SOL.« less

  2. The reconstruction and research progress of the TEXT-U tokamak in China

    NASA Astrophysics Data System (ADS)

    Zhuang, G.; Pan, Y.; Hu, X. W.; Wang, Z. J.; Ding, Y. H.; Zhang, M.; Gao, L.; Zhang, X. Q.; Yang, Z. J.; Yu, K. X.; Gentle, K. W.; Huang, H.; J-TEXT Team

    2011-09-01

    The TEXT/(TEXT-U) tokamak, formerly built and operated by the University of Texas at Austin in USA, was dismantled and shipped to China in 2004, and renamed as the Joint TEXT (J-TEXT) tokamak. The reconstruction work, which included reassembly of the machine and development of peripheral devices, was completed in the spring of 2007. Consequently, the first plasma was obtained at the end of 2007. At present, a typical J-TEXT ohmic discharge can produce a plasma with flattop current up to 220 kA and lasting for 300 ms, line-averaged density above 2 × 1019 m-3, and an electron temperature of about 800 eV, with a toroidal magnetic field of 2.2 T. A number of diagnostic devices used to facilitate the routine operation and experimental scenarios were developed on the J-TEXT tokamak. Hence, the measurements of the electrostatic fluctuations in the edge region and conditional analysis of the intermittent burst events near the last closed flux surface were undertaken. The observation and simple analysis of MHD activity and disruption events were also performed. The preliminary experimental results and the future research plan for the J-TEXT are described in detail.

  3. The conceptual design of a robust, compact, modular tokamak reactor based on high-field superconductors

    NASA Astrophysics Data System (ADS)

    Whyte, D. G.; Bonoli, P.; Barnard, H.; Haakonsen, C.; Hartwig, Z.; Kasten, C.; Palmer, T.; Sung, C.; Sutherland, D.; Bromberg, L.; Mangiarotti, F.; Goh, J.; Sorbom, B.; Sierchio, J.; Ball, J.; Greenwald, M.; Olynyk, G.; Minervini, J.

    2012-10-01

    Two of the greatest challenges to tokamak reactors are 1) large single-unit cost of each reactor's construction and 2) their susceptibility to disruptions from operation at or above operational limits. We present an attractive tokamak reactor design that substantially lessens these issues by exploiting recent advancements in superconductor (SC) tapes allowing peak field on SC coil > 20 Tesla. A R˜3.3 m, B˜9.2 T, ˜ 500 MW fusion power tokamak provides high fusion gain while avoiding all disruptive operating boundaries (no-wall beta, kink, and density limits). Robust steady-state core scenarios are obtained by exploiting the synergy of high field, compact size and ideal efficiency current drive using high-field side launch of Lower Hybrid waves. The design features a completely modular replacement of internal solid components enabled by the demountability of the coils/tapes and the use of an immersion liquid blanket. This modularity opens up the possibility of using the device as a nuclear component test facility.

  4. Numerical studies of edge localized instabilities in tokamaks

    NASA Astrophysics Data System (ADS)

    Wilson, H. R.; Snyder, P. B.; Huysmans, G. T. A.; Miller, R. L.

    2002-04-01

    A new computational tool, edge localized instabilities in tokamaks equilibria (ELITE), has been developed to help our understanding of short wavelength instabilities close to the edge of tokamak plasmas. Such instabilities may be responsible for the edge localized modes observed in high confinement H-mode regimes, which are a serious concern for next step tokamaks because of the high transient power loads which they can impose on divertor target plates. ELITE uses physical insight gained from analytic studies of peeling and ballooning modes to provide an efficient way of calculating the edge ideal magnetohydrodynamic stability properties of tokamaks. This paper describes the theoretical formalism which forms the basis for the code.

  5. Feedback-Assisted Extension of the Tokamak Operating Space to Low Safety Factor

    NASA Astrophysics Data System (ADS)

    Hanson, J. M.

    2013-10-01

    Recent DIII-D experiments have demonstrated stable operation at very low edge safety factor, q95 <~ 2 through the use of magnetic feedback to control the n = 1 resistive wall mode (RWM) instability. The performance of tokamak fusion devices may benefit from increased plasma current, and thus, decreased q. However, disruptive stability limits are commonly encountered in experiments at qedge ~ 2 (limited plasmas) and q95 ~ 2 (diverted plasmas), limiting exploration of low q regimes. In the recent DIII-D experiments, the impact and control of key disruptive instabilities was studied. Locked n = 1 modes with exponential growth times on the order of the wall eddy current decay timescale τw preceded disruptions at q95 = 2 . The instabilities have a poloidal structure that is consistent with VALEN simulations of the RWM mode structure at q95 = 2 . Applying proportional gain magnetic feedback control of the n = 1 mode resulted in stabilized operation with q95 reaching 1.9, and an extension of the discharge lifetime for > 100τw . Loss of feedback control was accompanied by power supply saturation, followed by a rapidly growing n = 1 mode and disruption. Comparisons of the feedback dynamics with VALEN simulations will be presented. The DIII-D results complement and will be discussed alongside recent RFX-MOD demonstrations of RWM control using magnetic feedback in limited tokamak discharges with qedge < 2. These results call attention to the utility of magnetic feedback in significantly extending the tokamak operational space and potentially opening a new route to economical fusion power production. Supported by the US Department of Energy under DE-FG02-04ER54761 and DE-FC02-04ER54698.

  6. An upgrade of the magnetic diagnostic system of the DIII-D tokamak for non-axisymmetric measurements

    DOE PAGES

    King, Joshua D.; Strait, Edward J.; Boivin, Rejean L.; ...

    2014-08-07

    Here, the DIII-D tokamak magnetic diagnostic system has been upgraded to significantly expand the measurement of the plasma response to intrinsic and applied non-axisymmetric “3D” fields. The placement and design of 101 additional sensors allow resolution of toroidal mode numbers 1 ≤ n ≤ 3, and poloidal wavelengths smaller than MARS-F, IPEC, and VMEC magnetohydrodynamic (MHD) model predictions. Small 3D perturbations, relative to the equilibrium field (10 –5 0 <10 –4), require sub-millimeter fabrication and installation tolerances. This high precision is achieved using electrical discharge machined components, and alignment techniques employing rotary laser levels and a coordinate measurement machine. Amore » 16-bit data acquisition system is used in conjunction with analog signal-processing to recover non-axisymmetric perturbations. Co-located radial and poloidal field measurements allow up to 14.2 cm spatial resolution of poloidal structures (plasma poloidal circumference is ~ 500 cm). The function of the new system is verified by comparing the rotating tearing mode structure, measured by 31 BP fluctuation sensors, with that measured by the upgraded B R saddle loop sensors after the mode locks to the vessel wall. The result is a nearly identical 2/1 helical eigenstructure in both cases.« less

  7. Self-consistent perturbed equilibrium with neoclassical toroidal torque in tokamaks

    DOE PAGES

    Park, Jong-Kyu; Logan, Nikolas C.

    2017-03-01

    Toroidal torque is one of the most important consequences of non-axisymmetric fields in tokamaks. The well-known neoclassical toroidal viscosity (NTV) is due to the second-order toroidal force from anisotropic pressure tensor in the presence of these asymmetries. This work shows that the first-order toroidal force originating from the same anisotropic pressure tensor, despite having no flux surface average, can significantly modify the local perturbed force balance and thus must be included in perturbed equilibrium self-consistent with NTV. The force operator with an anisotropic pressure tensor is not self-adjoint when the NTV torque is finite and thus is solved directly formore » each component. This approach yields a modified, non-self-adjoint Euler-Lagrange equation that can be solved using a variety of common drift-kinetic models in generalized tokamak geometry. The resulting energy and torque integral provides a unique way to construct a torque response matrix, which contains all the information of self-consistent NTV torque profiles obtainable by applying non-axisymmetric fields to the plasma. This torque response matrix can then be used to systematically optimize non-axisymmetric field distributions for desired NTV profiles. Published by AIP Publishing.« less

  8. 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.

  9. Bulk ion heating with ICRF waves in tokamaks

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

    Mantsinen, M. J., E-mail: mervi.mantsinen@bsc.es; Barcelona Supercomputing Center, Barcelona; Bilato, R.

    2015-12-10

    Heating with ICRF waves is a well-established method on present-day tokamaks and one of the heating systems foreseen for ITER. However, further work is still needed to test and optimize its performance in fusion devices with metallic high-Z plasma facing components (PFCs) in preparation of ITER and DEMO operation. This is of particular importance for the bulk ion heating capabilities of ICRF waves. Efficient bulk ion heating with the standard ITER ICRF scheme, i.e. the second harmonic heating of tritium with or without {sup 3}He minority, was demonstrated in experiments carried out in deuterium-tritium plasmas on JET and TFTR andmore » is confirmed by ICRF modelling. This paper focuses on recent experiments with {sup 3}He minority heating for bulk ion heating on the ASDEX Upgrade (AUG) tokamak with ITER-relevant all-tungsten PFCs. An increase of 80% in the central ion temperature T{sub i} from 3 to 5.5 keV was achieved when 3 MW of ICRF power tuned to the central {sup 3}He ion cyclotron resonance was added to 4.5 MW of deuterium NBI. The radial gradient of the T{sub i} profile reached locally values up to about 50 keV/m and the normalized logarithmic ion temperature gradients R/LT{sub i} of about 20, which are unusually large for AUG plasmas. The large changes in the T{sub i} profiles were accompanied by significant changes in measured plasma toroidal rotation, plasma impurity profiles and MHD activity, which indicate concomitant changes in plasma properties with the application of ICRF waves. When the {sup 3}He concentration was increased above the optimum range for bulk ion heating, a weaker peaking of the ion temperature profile was observed, in line with theoretical expectations.« less

  10. YieldStar based reticle 3D measurements and its application

    NASA Astrophysics Data System (ADS)

    Vaenkatesan, Vidya; Finders, Jo; ten Berge, Peter; Plug, Reinder; Sijben, Anko; Schellekens, Twan; Dillen, Harm; Pocobiej, Wojciech; Jorge, Vasco G.; van Dijck, Jurgen

    2016-09-01

    YieldStar (YS) is an established ASML-built scatterometer that is capable of measuring wafer Critical Dimension (CD), Overlay and Focus. In a recent work, the application range of YS was extended to measure 3D CD patterns on a reticle (pattern CD, height, Side Wall Angle-SWA). The primary motivation for this study came from imaging studies that indicated a need for measuring and controlling reticle 3D topography. CD scanning electron microscope (CD-SEM), Atomic force microscope (AFM), 3D multiple detector SEM (3D-SEM) are the preferred tools for reticle metrology. While these tools serve the industry well, the current research to the impact of reticle 3D involves extensive costs, logistic challenges and increased reticle lead time. YS provides an attractive alternative as it can measure pattern CD, SWA and height in a single measurement and at high throughput. This work demonstrates the capability of YS as a reticle metrology tool.

  11. Merging-compression formation of high temperature tokamak plasma

    NASA Astrophysics Data System (ADS)

    Gryaznevich, M. P.; Sykes, A.

    2017-07-01

    Merging-compression is a solenoid-free plasma formation method used in spherical tokamaks (STs). Two plasma rings are formed and merged via magnetic reconnection into one plasma ring that then is radially compressed to form the ST configuration. Plasma currents of several hundred kA and plasma temperatures in the keV-range have been produced using this method, however until recently there was no full understanding of the merging-compression formation physics. In this paper we explain in detail, for the first time, all stages of the merging-compression plasma formation. This method will be used to create ST plasmas in the compact (R ~ 0.4-0.6 m) high field, high current (3 T/2 MA) ST40 tokamak. Moderate extrapolation from the available experimental data suggests the possibility of achieving plasma current ~2 MA, and 10 keV range temperatures at densities ~1-5  ×  1020 m-3, bringing ST40 plasmas into a burning plasma (alpha particle heating) relevant conditions directly from the plasma formation. Issues connected with this approach for ST40 and future ST reactors are discussed

  12. Helical variation of density profiles and fluctuations in the tokamak pedestal with applied 3D fields and implications for confinement

    DOE PAGES

    Wilcox, R. S.; Rhodes, T. L.; Shafer, M. W.; ...

    2018-04-19

    Smore » mall 3D perturbations to the magnetic field in DIII-D ( δ B / B ~ 2 × 10 - 4 ) result in large modulations of density fluctuation amplitudes in the pedestal, which are shown using Doppler backscattering measurements to vary by a factor of 2. Helical perturbations of equilibrium density within flux surfaces have previously been observed in the pedestal of DIII-D plasmas when 3D fields are applied and were correlated with density fluctuation asymmetries in the pedestal. These intra-surface density and pressure variations are shown through two fluid MHD modeling studies using the M3D-C1 code to be due to the misalignment of the density and temperature equilibrium iso-surfaces in the pedestal region. This modeling demonstrates that the phase shift between the two iso-surfaces corresponds to the diamagnetic direction of the two species, with the mass density surfaces shifted in the ion diamagnetic direction relative to the temperature and magnetic flux iso-surfaces. Finally, the resulting pedestal density, potential, and turbulence asymmetries within flux surfaces near the separatrix may be at least partially responsible for several poorly understood phenomena that occur with the application of 3D fields in tokamaks, including density pump out and the increase in power required to transition from L- to H-mode.« less

  13. Helical variation of density profiles and fluctuations in the tokamak pedestal with applied 3D fields and implications for confinement

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

    Wilcox, R. S.; Rhodes, T. L.; Shafer, M. W.

    Smore » mall 3D perturbations to the magnetic field in DIII-D ( δ B / B ~ 2 × 10 - 4 ) result in large modulations of density fluctuation amplitudes in the pedestal, which are shown using Doppler backscattering measurements to vary by a factor of 2. Helical perturbations of equilibrium density within flux surfaces have previously been observed in the pedestal of DIII-D plasmas when 3D fields are applied and were correlated with density fluctuation asymmetries in the pedestal. These intra-surface density and pressure variations are shown through two fluid MHD modeling studies using the M3D-C1 code to be due to the misalignment of the density and temperature equilibrium iso-surfaces in the pedestal region. This modeling demonstrates that the phase shift between the two iso-surfaces corresponds to the diamagnetic direction of the two species, with the mass density surfaces shifted in the ion diamagnetic direction relative to the temperature and magnetic flux iso-surfaces. Finally, the resulting pedestal density, potential, and turbulence asymmetries within flux surfaces near the separatrix may be at least partially responsible for several poorly understood phenomena that occur with the application of 3D fields in tokamaks, including density pump out and the increase in power required to transition from L- to H-mode.« less

  14. Clinical heterogeneity of type 1 diabetes (T1D) found in Asia.

    PubMed

    Park, Yongsoo; Wintergerst, Kupper A; Zhou, Zhiguang

    2017-10-01

    Diabetes mellitus among young patients in Asia is caused by a complex set of factors. Although type 1 diabetes (T1D) remains the most common form of diabetes in children, the recent unabated increase in obesity has resulted in the emergence of type 2 diabetes (T2D) as a new type of diabetes among adolescents and young adults. In addition to the typical autoimmune type 1 diabetes (T1aD) and T2D patients, there is a variable incidence of cases of non-autoimmune types of T1D associated with insulin deficiency (T1bD). Additional forms have been described, including fulminant T1D (FT1D). Although most diagnoses of T1D are classified as T1aD, fulminant T1D exists as a hyper-acute subtype of T1D that affects older children, without associated autoimmunity. Patient with this rare aetiology of diabetes showed a complete loss of β-cell secretory capacity without evidence of recovery, necessitating long-term treatment with insulin. In addition, latent autoimmune diabetes in adults is a form of autoimmune-mediated diabetes, usually diagnosed during the insulin-dependent stage that follows a non-insulin requiring phase, which can be diagnosed earlier based on anti-islet autoantibody positivity. Some reports discuss T1bD. Others are elaborating on the presence of "atypical T1b diabetes," such as Flatbush diabetes. The prevalence of diabetes mellitus in young adults continues to rise in Asian populations as T2D increases. With improved characterization of patients with diabetes, the range of diabetic subgroups will become even more diverse in the future. Distinguishing T1D, T2D, and other forms of diabetes in young patients is challenging in Asian populations, as the correct diagnosis is clinically important and has implications for prognosis and management. Despite aetiological heterogeneity in the usual clinical setting, early diagnosis and classification of patients with diabetes relying on clinical grounds as well as measuring islet autoantibodies and fasting plasma C

  15. Optimization of 3D Field Design

    NASA Astrophysics Data System (ADS)

    Logan, Nikolas; Zhu, Caoxiang

    2017-10-01

    Recent progress in 3D tokamak modeling is now leveraged to create a conceptual design of new external 3D field coils for the DIII-D tokamak. Using the IPEC dominant mode as a target spectrum, the Finding Optimized Coils Using Space-curves (FOCUS) code optimizes the currents and 3D geometry of multiple coils to maximize the total set's resonant coupling. The optimized coils are individually distorted in space, creating toroidal ``arrays'' containing a variety of shapes that often wrap around a significant poloidal extent of the machine. The generalized perturbed equilibrium code (GPEC) is used to determine optimally efficient spectra for driving total, core, and edge neoclassical toroidal viscosity (NTV) torque and these too provide targets for the optimization of 3D coil designs. These conceptual designs represent a fundamentally new approach to 3D coil design for tokamaks targeting desired plasma physics phenomena. Optimized coil sets based on plasma response theory will be relevant to designs for future reactors or on any active machine. External coils, in particular, must be optimized for reliable and efficient fusion reactor designs. Work supported by the US Department of Energy under DE-AC02-09CH11466.

  16. In vivo 1D and 2D correlation MR spectroscopy of the soleus muscle at 7T

    PubMed Central

    Ramadan, Saadallah; Ratai, Eva-Maria; Wald, Lawrence L.; Mountford, Carolyn E.

    2013-01-01

    Aim This study aims to (1) undertake and analyse 1D and 2D MR correlation spectroscopy from human soleus muscle in vivo at 7T, and (2) determine T1 and T2 relaxation time constants at 7T field strength due to their importance in sequence design and spectral quantitation. Method Six healthy, male volunteers were consented and scanned on a 7T whole-body scanner (Siemens AG, Erlangen, Germany). Experiments were undertaken using a 28 cm diameter detunable birdcage coil for signal excitation and an 8.5 cm diameter surface coil for signal reception. The relaxation time constants, T1 and T2 were recorded using a STEAM sequence, using the ‘progressive saturation’ method for the T1 and multiple echo times for T2. The 2D L-Correlated SpectroscopY (L-COSY) method was employed with 64 increments (0.4 ms increment size) and eight averages per scan, with a total time of 17 min. Results T1 and T2 values for the metabolites of interest were determined. The L-COSY spectra obtained from the soleus muscle provided information on lipid content and chemical structure not available, in vivo, at lower field strengths. All molecular fragments within multiple lipid compartments were chemically shifted by 0.20–0.26 ppm at this field strength. 1D and 2D L-COSY spectra were assigned and proton connectivities were confirmed with the 2D method. Conclusion In vivo 1D and 2D spectroscopic examination of muscle can be successfully recorded at 7T and is now available to assess lipid alterations as well as other metabolites present with disease. T1 and T2 values were also determined in soleus muscle of male healthy volunteers. PMID:20206561

  17. H-mode achievement and edge features in RFX-mod tokamak operation

    NASA Astrophysics Data System (ADS)

    Spolaore, M.; Cavazzana, R.; Marrelli, L.; Carraro, L.; Franz, P.; Spagnolo, S.; Zaniol, B.; Zuin, M.; Cordaro, L.; Dal Bello, S.; De Masi, G.; Ferro, A.; Finotti, C.; Grando, L.; Grenfell, G.; Innocente, P.; Kudlacek, O.; Marchiori, G.; Martines, E.; Momo, B.; Paccagnella, R.; Piovesan, P.; Piron, C.; Puiatti, M. E.; Recchia, M.; Scarin, P.; Taliercio, C.; Vianello, N.; Zanotto, L.

    2017-11-01

    The RFX-mod experiment is a fusion device designed to operate as a reversed field pinch (RFP), with a major radius R = 2 m and a minor radius a = 0.459 m. Its high versatility recently allowed operating it also as an ohmic tokamak, allowing comparative studies between the two configurations in the same device. The device is equipped with a state of the art MHD mode feedback control system providing a magnetic boundary effective control, by applying resonant or non-resonant magnetic perturbations (MP), both in RFP and in tokamak configurations. In the fusion community the application of MPs is widely studied as a promising tool to limit the impact of plasma filaments and ELMs (edge localized modes) on plasma facing components. An important new research line is the exploitation of the RFX-mod active control system for ELM mitigation studies. As a first step in this direction, this paper presents the most recent achievements in term of RFX-mod tokamak explored scenarios, which allowed the first investigation of the ohmic and edge biasing induced H-mode. The production of D-shaped tokamak discharges and the design and deployment of an insertable polarized electrode were accomplished. Reproducible H-mode phases were obtained with insertable electrode negative biasing in single null discharges, representing an unexplored scenario with this technique. Important modifications of the edge plasma density and flow properties are observed. During the achieved H-mode ELM-like electromagnetic composite filamentary structures are observed. They are characterized by clear vorticity and parallel current density patterns.

  18. Neutral-beam deposition in large, finite-beta noncircular tokamak plasmas

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

    Wieland, R.M.; Houlberg, W.A.

    1982-02-01

    A parametric pencil beam model is introduced for describing the attenuation of an energetic neutral beam moving through a tokamak plasma. The nonnegligible effects of a finite beam cross section and noncircular shifted plasma cross sections are accounted for in a simple way by using a smoothing algorithm dependent linearly on beam radius and by including information on the plasma flux surface geometry explicitly. The model is benchmarked against more complete and more time-consuming two-dimensional Monte Carlo calculations for the case of a large D-shaped tokamak plasma with minor radius a = 120 cm and elongation b/a = 1.6. Depositionmore » profiles are compared for deuterium beam energies of 120 to 150 keV, central plasma densities of 8 x 10/sup 13/ - 2 x 10/sup 14/ cm/sup -3/, and beam orientation ranging from perpendicular to tangential to the inside wall.« less

  19. A novel flexible field-aligned coordinate system for tokamak edge plasma simulation

    NASA Astrophysics Data System (ADS)

    Leddy, J.; Dudson, B.; Romanelli, M.; Shanahan, B.; Walkden, N.

    2017-03-01

    Tokamak plasmas are confined by a magnetic field that limits the particle and heat transport perpendicular to the field. Parallel to the field the ionised particles can move freely, so to obtain confinement the field lines are "closed" (i.e. form closed surfaces of constant poloidal flux) in the core of a tokamak. Towards, the edge, however, the field lines intersect physical surfaces, leading to interaction between neutral and ionised particles, and the potential melting of the material surface. Simulation of this interaction is important for predicting the performance and lifetime of future tokamak devices such as ITER. Field-aligned coordinates are commonly used in the simulation of tokamak plasmas due to the geometry and magnetic topology of the system. However, these coordinates are limited in the geometry they allow in the poloidal plane due to orthogonality requirements. A novel 3D coordinate system is proposed herein that relaxes this constraint so that any arbitrary, smoothly varying geometry can be matched in the poloidal plane while maintaining a field-aligned coordinate. This system is implemented in BOUT++ and tested for accuracy using the method of manufactured solutions. A MAST edge cross-section is simulated using a fluid plasma model and the results show expected behaviour for density, temperature, and velocity. Finally, simulations of an isolated divertor leg are conducted with and without neutrals to demonstrate the ion-neutral interaction near the divertor plate and the corresponding beneficial decrease in plasma temperature.

  20. 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.

  1. Disruptions generated runaways in the FTU high field tokamak

    NASA Astrophysics Data System (ADS)

    Poli, F. M.; Esposito, B.; Maddaluno, G.; Martin-Solis, J. R.

    2001-10-01

    Disruptions in FTU are usually accompanied by the generation of a strong pulse of photoneutrons (YN 10^12n/s), resulting from photonuclear reactions induced by the bremsstrahlung radiation emitted when runaway electrons (REs) strike the plasma facing components. Measurements of YN during major disruptions on TS [1] showed variations of three orders of magnitude when the toroidal field Bt increases from 1.8T to 3.9T. Similar results were found on JT-60 [2], where no REs are produced for low Bt (<2.2T) and a large YN was measured for higher fields (up to 4T). The range of Bt available in FTU (4T-8T) allows to extend such analysis so that useful predictions can be obtained for operation in next-step high field tokamaks (IGNITOR, ITER). The dependence of YN on Bt is investigated in several FTU disruptions. YN increases with Bt for B_t=4T-6T, while no variation is found for B_t=6T-8T: the role played by ne and Ip on such trend is discussed. [1]P.Joyer,G.Martin,Contr.Fusion and Plasma Heating,Proc.17^thEPS Conf.Amsterdam(1990) [2]R.Yoshino et al.,Nucl.Fus.39 151 (1999)

  2. Analysis of higher harmonics on bidirectional heat pulse propagation experiment in helical and tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Kobayashi, T.; Ida, K.; Inagaki, S.; Tsuchiya, H.; Tamura, N.; Choe, G. H.; Yun, G. S.; Park, H. K.; Ko, W. H.; Evans, T. E.; Austin, M. E.; Shafer, M. W.; Ono, M.; López-bruna, D.; Ochando, M. A.; Estrada, T.; Hidalgo, C.; Moon, C.; Igami, H.; Yoshimura, Y.; Tsujimura, T. Ii.; Itoh, S.-I.; Itoh, K.

    2017-07-01

    In this contribution we analyze modulation electron cyclotron resonance heating (MECH) experiment and discuss higher harmonic frequency dependence of transport coefficients. We use the bidirectional heat pulse propagation method, in which both inward propagating heat pulse and outward propagating heat pulse are analyzed at a radial range, in order to distinguish frequency dependence of transport coefficients due to hysteresis from that due to other reasons, such as radially dependent transport coefficients, a finite damping term, or boundary effects. The method is applied to MECH experiments performed in various helical and tokamak devices, i.e. Large Helical Device (LHD), TJ-II, Korea Superconducting Tokamak Advanced Research (KSTAR), and Doublet III-D (DIII-D) with different plasma conditions. The frequency dependence of transport coefficients are clearly observed, showing a possibility of existence of transport hysteresis in flux-gradient relation.

  3. UCLA Tokamak Program Close Out Report.

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

    Taylor, Robert John

    2014-02-04

    The results of UCLA experimental fusion program are summarized. Starting with smaller devices like Microtor, Macrotor, CCT and ending the research on the large (5 m) Electric Tokamak. CCT was the most diagnosed device for H-mode like physics and the effects of rotation induced radial fields. ICRF heating was also studied but plasma heating of University Type Tokamaks did not produce useful results due to plasma edge disturbances of the antennae. The Electric Tokamak produced better confinement in the seconds range. However, it presented very good particle confinement due to an "electric particle pinch". This effect prevented us from reachingmore » a quasi steady state. This particle accumulation effect was numerically explained by Shaing's enhanced neoclassical theory. The PI believes that ITER will have a good energy confinement time but deleteriously large particle confinement time and it will disrupt on particle pinching at nominal average densities. The US fusion research program did not study particle transport effects due to its undue focus on the physics of energy confinement time. Energy confinement time is not an issue for energy producing tokamaks. Controlling the ash flow will be very expensive.« less

  4. Coupled two-dimensional edge plasma and neutral gas modeling of tokamak scrape-off-layers

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

    Maingi, Rajesh

    1992-08-01

    The objective of this study is to devise a detailed description of the tokamak scrape-off-layer (SOL), which includes the best available models of both the plasma and neutral species and the strong coupling between the two in many SOL regimes. A good estimate of both particle flux and heat flux profiles at the limiter/divertor target plates is desired. Peak heat flux is one of the limiting factors in determining the survival probability of plasma-facing-components at high power levels. Plate particle flux affects the neutral flux to the pump, which determines the particle exhaust rate. A technique which couples a two-dimensionalmore » (2-D) plasma and a 2-D neutral transport code has been developed (coupled code technique), but this procedure requires large amounts of computer time. Relevant physics has been added to an existing two-neutral-species model which takes the SOL plasma/neutral coupling into account in a simple manner (molecular physics model), and this model is compared with the coupled code technique mentioned above. The molecular physics model is benchmarked against experimental data from a divertor tokamak (DIII-D), and a similar model (single-species model) is benchmarked against data from a pump-limiter tokamak (Tore Supra). The models are then used to examine two key issues: free-streaming-limits (ion energy conduction and momentum flux) and the effects of the non-orthogonal geometry of magnetic flux surfaces and target plates on edge plasma parameter profiles.« less

  5. Thermodynamics of triple helix formation: spectrophotometric studies on the d(A)10.2d(T)10 and d(C+3T4C+3).d(G3A4G3).d(C3T4C3) triple helices.

    PubMed Central

    Pilch, D S; Brousseau, R; Shafer, R H

    1990-01-01

    We have stabilized the d(A)10.2d(T)10 and d(C+LT4C+3).d(G3A4G3).d(C3T4C3) triple helices with either NaCl or MgCl2 at pH 5.5. UV mixing curves demonstrate a 1:2 stoichiometry of purine to pyrimidine strands under the appropriate conditions of pH and ionic strength. Circular dichroic titrations suggest a possible sequence-independent spectral signature for triplex formation. Thermal denaturation profiles indicate the initial loss of the third strand followed by dissociation of the underlying duplex with increasing temperature. Depending on the base sequence and ionic conditions, the binding affinity of the third strand for the duplex at 25 degrees C is two to five orders of magnitude lower than that of the two strands forming the duplex. Thermodynamic parameters for triplex formation were determined for both sequences in the presence of 50 mM MgCl2 and/or 2.0 M NaCl. Hoogsteen base pairs are 0.22-0.64 kcal/mole less stable than Watson-Crick base pairs, depending on ionic conditions and base composition. C+.G and T.A Hoogsteen base pairs appear to have similar stability in the presence of Mg2+ ions at low pH. PMID:2216768

  6. The yield of N/2D/ atoms in the dissociative recombination of NO/+/

    NASA Technical Reports Server (NTRS)

    Kley, D.; Lawrence, G. M.; Stone, E. J.

    1977-01-01

    The quantum yield or branching ratio of N(2D) atoms formed in the reaction e + NO(+) yields N + O was measured to be 76% plus or minus 6%. Photoionization of buffered nitric oxide by a flash lamp was studied using time-resolved atomic absorption. Atoms were produced both by direct photodissociation and by dissociative recombination, and these two effects were separated by means of SF6 as an electron scavenger.

  7. Open charm yields in d+Au collisions at squareroot[sNN]=200 GeV.

    PubMed

    Adams, J; Aggarwal, M M; Ahammed, Z; Amonett, J; Anderson, B D; Arkhipkin, D; Averichev, G S; Badyal, S K; Bai, Y; Balewski, J; Barannikova, O; Barnby, L S; Baudot, J; Bekele, S; Belaga, V V; Bellwied, R; Berger, J; Bezverkhny, B I; Bharadwaj, S; Bhasin, A; Bhati, A K; Bhatia, V S; Bichsel, H; Billmeier, A; Bland, L C; Blyth, C O; Bonner, B E; Botje, M; Boucham, A; Brandin, A V; Bravar, A; Bystersky, M; Cadman, R V; Cai, X Z; Caines, H; Calderón de la Barca Sánchez, M; Castillo, J; Cebra, D; Chajecki, Z; Chaloupka, P; Chattopadhyay, S; Chen, H F; Chen, Y; Cheng, J; Cherney, M; Chikanian, A; Christie, W; Coffin, J P; Cormier, T M; Cramer, J G; Crawford, H J; Das, D; Das, S; de Moura, M M; Derevschikov, A A; Didenko, L; Dietel, T; Dogra, S M; Dong, W J; Dong, X; Draper, J E; Du, F; Dubey, A K; Dunin, V B; Dunlop, J C; Dutta Mazumdar, M R; Eckardt, V; Edwards, W R; Efimov, L G; Emelianov, V; Engelage, J; Eppley, G; Erazmus, B; Estienne, M; Fachini, P; Faivre, J; Fatemi, R; Fedorisin, J; Filimonov, K; Filip, P; Finch, E; Fine, V; Fisyak, Y; Fomenko, K; Fu, J; Gagliardi, C A; Gaillard, L; Gans, J; Ganti, M S; Gaudichet, L; Geurts, F; Ghazikhanian, V; Ghosh, P; Gonzalez, J E; Grachov, O; Grebenyuk, O; Grosnick, D; Guertin, S M; Guo, Y; Gupta, A; Gutierrez, T D; Hallman, T J; Hamed, A; Hardtke, D; Harris, J W; Heinz, M; Henry, T W; Hepplemann, S; Hippolyte, B; Hirsch, A; Hjort, E; Hoffmann, G W; Huang, H Z; Huang, S L; Hughes, E W; Humanic, T J; Igo, G; Ishihara, A; Jacobs, P; Jacobs, W W; Janik, M; Jiang, H; Jones, P G; Judd, E G; Kabana, S; Kang, K; Kaplan, M; Keane, D; Khodyrev, V Yu; Kiryluk, J; Kisiel, A; Kislov, E M; Klay, J; Klein, S R; Koetke, D D; Kollegger, T; Kopytine, M; Kotchenda, L; Kramer, M; Kravtsov, P; Kravtsov, V I; Krueger, K; Kuhn, C; Kulikov, A I; Kumar, A; Kutuev, R Kh; Kuznetsov, A A; Lamont, M A C; Landgraf, J M; Lange, S; Laue, F; Lauret, J; Lebedev, A; Lednicky, R; Lehocka, S; LeVine, M J; Li, C; Li, Q; Li, Y; Lin, G; Lindenbaum, S J; Lisa, M A; Liu, F; Liu, L; Liu, Q J; Liu, Z; Ljubicic, T; Llope, W J; Long, H; Longacre, R S; Lopez-Noriega, M; Love, W A; Lu, Y; Ludlam, T; Lynn, D; Ma, G L; Ma, J G; Ma, Y G; Magestro, D; Mahajan, S; Mahapatra, D P; Majka, R; Mangotra, L K; Manweiler, R; Margetis, S; Markert, C; Martin, L; Marx, J N; Matis, H S; Matulenko, Yu A; McClain, C J; McShane, T S; Meissner, F; Melnick, Yu; Meschanin, A; Miller, M L; Minaev, N G; Mironov, C; Mischke, A; Mishra, D K; Mitchell, J; Mohanty, B; Molnar, L; Moore, C F; Morozov, D A; Munhoz, M G; Nandi, B K; Nayak, S K; Nayak, T K; Nelson, J M; Netrakanti, P K; Nikitin, V A; Nogach, L V; Nurushev, S B; Odyniec, G; Ogawa, A; Okorokov, V; Oldenburg, M; Olson, D; Pal, S K; Panebratsev, Y; Panitkin, S Y; Pavlinov, A I; Pawlak, T; Peitzmann, T; Perevoztchikov, V; Perkins, C; Peryt, W; Petrov, V A; Phatak, S C; Picha, R; Planinic, M; Pluta, J; Porile, N; Porter, J; Poskanzer, A M; Potekhin, M; Potrebenikova, E; Potukuchi, B V K S; Prindle, D; Pruneau, C; Putschke, J; Rakness, G; Raniwala, R; Raniwala, S; Ravel, O; Ray, R L; Razin, S V; Reichhold, D; Reid, J G; Renault, G; Retiere, F; Ridiger, A; Ritter, H G; Roberts, J B; Rogachevskiy, O V; Romero, J L; Rose, A; Roy, C; Ruan, L; Sahoo, R; Sakrejda, I; Salur, S; Sandweiss, J; Sarsour, M; Savin, I; Sazhin, P S; Schambach, J; Scharenberg, R P; Schmitz, N; Schweda, K; Seger, J; Seyboth, P; Shahaliev, E; Shao, M; Shao, W; Sharma, M; Shen, W Q; Shestermanov, K E; Shimanskiy, S S; Sichtermann, E; Simon, F; Singaraju, R N; Skoro, G; Smirnov, N; Snellings, R; Sood, G; Sorensen, P; Sowinski, J; Speltz, J; Spinka, H M; Srivastava, B; Stadnik, A; Stanislaus, T D S; Stock, R; Stolpovsky, A; Strikhanov, M; Stringfellow, B; Suaide, A A P; Sugarbaker, E; Suire, C; Sumbera, M; Surrow, B; Symons, T J M; Szanto de Toledo, A; Szarwas, P; Tai, A; Takahashi, J; Tang, A H; Tarnowsky, T; Thein, D; Thomas, J H; Timoshenko, S; Tokarev, M; Trainor, T A; Trentalange, S; Tribble, R E; Tsai, O D; Ulery, J; Ullrich, T; Underwood, D G; Urkinbaev, A; Van Buren, G; van Leeuwen, M; Vander Molen, A M; Varma, R; Vasilevski, I M; Vasiliev, A N; Vernet, R; Vigdor, S E; Viyogi, Y P; Vokal, S; Voloshin, S A; Vznuzdaev, M; Waggoner, W T; Wang, F; Wang, G; Wang, G; Wang, X L; Wang, Y; Wang, Y; Wang, Z M; Ward, H; Watson, J W; Webb, J C; Wells, R; Westfall, G D; Wetzler, A; Whitten, C; Wieman, H; Wissink, S W; Witt, R; Wood, J; Wu, J; Xu, N; Xu, Z; Xu, Z Z; Yamamoto, E; Yepes, P; Yurevich, V I; Zanevsky, Y V; Zhang, H; Zhang, W M; Zhang, Z P; Zoulkarneev, R; Zoulkarneeva, Y; Zubarev, A N

    2005-02-18

    Midrapidity open charm spectra from direct reconstruction of D0(D0)-->K-/+pi+/- in d+Au collisions and indirect electron-positron measurements via charm semileptonic decays in p+p and d+Au collisions at squareroot[sNN]=200 GeV are reported. The D0(D0) spectrum covers a transverse momentum (pT) range of 0.1T<3 GeV/c, whereas the electron spectra cover a range of 1T<4 GeV/c. The electron spectra show approximate binary collision scaling between p+p and d+Au collisions. From these two independent analyses, the differential cross section per nucleon-nucleon binary interaction at midrapidity for open charm production from d+Au collisions at BNL RHIC is dsigma(NN)cc/dy=0.30+/-0.04(stat)+/-0.09(syst) mb. The results are compared to theoretical calculations. Implications for charmonium results in A+A collisions are discussed.

  8. NIMROD modeling of poloidal flow damping in tokamaks using kinetic closures

    NASA Astrophysics Data System (ADS)

    Jepson, J. R.; Hegna, C. C.; Held, E. D.

    2017-10-01

    Calculations of poloidal flow damping in a tokamak are undertaken using two different implementations of the ion drift kinetic equation (DKE) in the extended MHD code NIMROD. The first approach is hybrid fluid/kinetic and uses a Chapman Enskog-like (CEL) Ansatz. Closure of the evolving lower-order fluid moment equations for n, V , and T is provided by solutions to the ion CEL-DKE written in the macroscopic flow reference frame. The second implementation solves the DKE using a delta-f approach. Here, the delta-f distribution describes all of the information beyond a static, lowest-order Maxwellian. We compare the efficiency and accuracy of these two approaches for a simple initial value problem that monitors the relaxation of the poloidal flow profile in high- and low-aspect-ratio tokamak geometry. The computation results are compared against analytic predictions of time dependent closures for the parallel viscous force. Supported by DoE Grants DE-FG02-86ER53218 and DE-FG02-04ER54746.

  9. Applying the new gamma ray imager diagnostic to measurements of runaway electron Bremsstrahlung radiation in the DIII-D Tokamak (invited)

    NASA Astrophysics Data System (ADS)

    Cooper, C. M.; Pace, D. C.; Paz-Soldan, C.; Commaux, N.; Eidietis, N. W.; Hollmann, E. M.; Shiraki, D.

    2016-11-01

    A new gamma ray imager (GRI) is developed to probe the electron distribution function with 2D spatial resolution during runaway electron (RE) experiments at the DIII-D tokamak. The diagnostic is sensitive to 0.5-100 MeV gamma rays, allowing characterization of the RE distribution function evolution during RE growth and dissipation. The GRI consists of a lead "pinhole camera" mounted on the DIII-D midplane with 123 honeycombed tangential chords 20 cm wide that span the vessel interior. Up to 30 bismuth germanate (BGO) scintillation detectors capture RE bremsstrahlung radiation for Pulse Height Analysis (PHA) capable of discriminating up to 20 000 pulses per second. Digital signal processing routines combining shaping filters are performed during PHA to reject noise and record gamma ray energy. The GRI setup and PHA algorithms will be described and initial data from experiments will be presented. A synthetic diagnostic is developed to generate the gamma ray spectrum of a GRI channel given the plasma information and a prescribed distribution function. Magnetic reconstructions of the plasma are used to calculate the angle between every GRI sightline and orient and discriminate gamma rays emitted by a field-aligned RE distribution function.

  10. Applying the new gamma ray imager diagnostic to measurements of runaway electron Bremsstrahlung radiation in the DIII-D Tokamak (invited).

    PubMed

    Cooper, C M; Pace, D C; Paz-Soldan, C; Commaux, N; Eidietis, N W; Hollmann, E M; Shiraki, D

    2016-11-01

    A new gamma ray imager (GRI) is developed to probe the electron distribution function with 2D spatial resolution during runaway electron (RE) experiments at the DIII-D tokamak. The diagnostic is sensitive to 0.5-100 MeV gamma rays, allowing characterization of the RE distribution function evolution during RE growth and dissipation. The GRI consists of a lead "pinhole camera" mounted on the DIII-D midplane with 123 honeycombed tangential chords 20 cm wide that span the vessel interior. Up to 30 bismuth germanate (BGO) scintillation detectors capture RE bremsstrahlung radiation for Pulse Height Analysis (PHA) capable of discriminating up to 20 000 pulses per second. Digital signal processing routines combining shaping filters are performed during PHA to reject noise and record gamma ray energy. The GRI setup and PHA algorithms will be described and initial data from experiments will be presented. A synthetic diagnostic is developed to generate the gamma ray spectrum of a GRI channel given the plasma information and a prescribed distribution function. Magnetic reconstructions of the plasma are used to calculate the angle between every GRI sightline and orient and discriminate gamma rays emitted by a field-aligned RE distribution function.

  11. The dissociative recombination of O2(+) - The quantum yield of O(1S) and O(1D)

    NASA Technical Reports Server (NTRS)

    Abreu, V. J.; Solomon, S. C.; Sharp, W. E.; Hays, P. B.

    1983-01-01

    Data from the visible airglow experiment on the Atmosphere Explorer-E satellite have been used to determine the quantum yield of O(1S) and O(1D) from the dissociative recombination of O2(+). A range of values between 0.09 and 0.23 has been obtained for the quantum yield of O(1S). It is shown that the quantum yield of O(1S) depends on the ratio of electron density to atomic oxygen density. This suggests that the quantum yield of O(1S) may depend on the degree of vibrational excitation of the recombining O2(+). The quantum yield of O(1D) has been measured to be 1.23 + or - 0.42, with no dependence on the electron-oxygen ratio.

  12. 3D T2-weighted imaging to shorten multiparametric prostate MRI protocols.

    PubMed

    Polanec, Stephan H; Lazar, Mathias; Wengert, Georg J; Bickel, Hubert; Spick, Claudio; Susani, Martin; Shariat, Shahrokh; Clauser, Paola; Baltzer, Pascal A T

    2018-04-01

    To determine whether 3D acquisitions provide equivalent image quality, lesion delineation quality and PI-RADS v2 performance compared to 2D acquisitions in T2-weighted imaging of the prostate at 3 T. This IRB-approved, prospective study included 150 consecutive patients (mean age 63.7 years, 35-84 years; mean PSA 7.2 ng/ml, 0.4-31.1 ng/ml). Two uroradiologists (R1, R2) independently rated image quality and lesion delineation quality using a five-point ordinal scale and assigned a PI-RADS score for 2D and 3D T2-weighted image data sets. Data were compared using visual grading characteristics (VGC) and receiver operating characteristics (ROC)/area under the curve (AUC) analysis. Image quality was similarly good to excellent for 2D T2w (mean score R1, 4.3 ± 0.81; R2, 4.7 ± 0.83) and 3D T2w (mean score R1, 4.3 ± 0.82; R2, 4.7 ± 0.69), p = 0.269. Lesion delineation was rated good to excellent for 2D (mean score R1, 4.16 ± 0.81; R2, 4.19 ± 0.92) and 3D T2w (R1, 4.19 ± 0.94; R2, 4.27 ± 0.94) without significant differences (p = 0.785). ROC analysis showed an equivalent performance for 2D (AUC 0.580-0.623) and 3D (AUC 0.576-0.629) T2w (p > 0.05, respectively). Three-dimensional acquisitions demonstrated equivalent image and lesion delineation quality, and PI-RADS v2 performance, compared to 2D in T2-weighted imaging of the prostate. Three-dimensional T2-weighted imaging could be used to considerably shorten prostate MRI protocols in clinical practice. • 3D shows equivalent image quality and lesion delineation compared to 2D T2w. • 3D T2w and 2D T2w image acquisition demonstrated comparable diagnostic performance. • Using a single 3D T2w acquisition may shorten the protocol by 40%. • Combined with short DCE, multiparametric protocols of 10 min are feasible.

  13. Tokamak Operation with Safety Factor q 95 < 2 via Control of MHD Stability

    DOE PAGES

    Piovesan, Paolo; Hanson, Jeremy M.; Martin, Piero; ...

    2014-07-24

    Magnetic feedback control of the resistive-wall mode has enabled DIII-D to access stable operation at safety factor q95 = 1:9 in divertor plasmas for 150 instability growth times. Magnetohydrodynamic stability sets a hard, disruptive limit on the minimum edge safety factor achievable in a tokamak, or on the maximum plasma current at given toroidal magnetic eld. In tokamaks with a divertor, the limit occurs at q95 = 2, as con rmed in DIII-D. Since the energy con cement time scales linearly with current, this also bounds the performance of a fusion reactor. DIII-D has overcome this limit, opening a wholemore » new high-current regime not accessible before. This result brings signi cant possible bene ts in terms of fusion performance, but it also extends resistive wall mode physics and its control to conditions never explored before. In present experiments, q95 < 2 operation is eventually halted by voltage limits reached in the feedback power supplies, not by intrinsic physics issues. Improvements to power supplies and to control algorithms have the potential to further extend this regime.« less

  14. Multi-scale gyrokinetic simulation of Alcator C-Mod tokamak discharges

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

    Howard, N. T., E-mail: nthoward@psfc.mit.edu; White, A. E.; Greenwald, M.

    2014-03-15

    Alcator C-Mod tokamak discharges have been studied with nonlinear gyrokinetic simulation simultaneously spanning both ion and electron spatiotemporal scales. These multi-scale simulations utilized the gyrokinetic model implemented by GYRO code [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] and the approximation of reduced electron mass (μ = (m{sub D}/m{sub e}){sup .5} = 20.0) to qualitatively study a pair of Alcator C-Mod discharges: a low-power discharge, previously demonstrated (using realistic mass, ion-scale simulation) to display an under-prediction of the electron heat flux and a high-power discharge displaying agreement with both ion and electron heat flux channels [N. T. Howard et al.,more » Nucl. Fusion 53, 123011 (2013)]. These multi-scale simulations demonstrate the importance of electron-scale turbulence in the core of conventional tokamak discharges and suggest it is a viable candidate for explaining the observed under-prediction of electron heat flux. In this paper, we investigate the coupling of turbulence at the ion (k{sub θ}ρ{sub s}∼O(1.0)) and electron (k{sub θ}ρ{sub e}∼O(1.0)) scales for experimental plasma conditions both exhibiting strong (high-power) and marginally stable (low-power) low-k (k{sub θ}ρ{sub s} < 1.0) turbulence. It is found that reduced mass simulation of the plasma exhibiting marginally stable low-k turbulence fails to provide even qualitative insight into the turbulence present in the realistic plasma conditions. In contrast, multi-scale simulation of the plasma condition exhibiting strong turbulence provides valuable insight into the coupling of the ion and electron scales.« less

  15. Thermonuclear Reaction Rate of T(t,2n) α Measured in ICF Plasmas

    NASA Astrophysics Data System (ADS)

    Brune, C. R.; Casey, D. T.; Caggiano, J. A.; Hatarik, R.; McNabb, D. P.; Sayre, D. B.; Smalyuk, V. A.; Bacher, A. D.; Frenje, J. A.; Gatu-Johnson, M.; Zylstra, A. B.; Couder, M.

    2014-09-01

    Measurements of charged-particle reactivity have been performed in inertial confinement fusion experiments at the National Ignition Facility. Time-of-flight detectors were used to measure neutrons from the T(t,2n) and T(d,n) reactions produced by implosions with tritium-filled targets (0.1% deuterium). Along with the measured target fuel composition and reactant ion temperature, the well-known T(d,n) reactivity was used to convert the measured neutron yields into a T(t,2n) reactivity. The ion temperature was determined to be 3.3(3) keV, corresponding to an effective energy of 16 keV. In comparison to accelerator measurements of the low-energy T(t,2n) cross section, the source of all previous data, our experiment has resulted in T(t,2n) data with better statistics and lower backgrounds.

  16. Yield-stress fluids foams: flow patterns and controlled production in T-junction and flow-focusing devices.

    PubMed

    Laborie, Benoit; Rouyer, Florence; Angelescu, Dan E; Lorenceau, Elise

    2016-11-23

    We study the formation of yield-stress fluid foams in millifluidic flow-focusing and T-junction devices. First, we provide a phase diagram for the unsteady operating regimes of bubble production when the gas pressure and the yield-stress fluid flow rate are imposed. Three regimes are identified: a co-flow of gas and yield-stress fluid, a transient production of bubble and a flow of yield-stress fluid only. Taking wall slip into account, we provide a model for the pressure at the onset of bubble formation. Then, we detail and compare two simple methods to ensure steady bubble production: regulation of the gas pressure or flow-rate. These techniques, which are easy to implement, thus open pathways for controlled production of dry yield-stress fluid foams as shown at the end of this article.

  17. 78 FR 52802 - Tin T. Win, M.D., Dismissal of Proceeding

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-26

    ... DEPARTMENT OF JUSTICE Drug Enforcement Administration Tin T. Win, M.D., Dismissal of Proceeding On... Cause and Immediate Suspension of Registration to Tin T. Win, M.D. (hereinafter, Registrant), of Lake... order that the Order to Show Cause and Immediate Suspension of Registration issued to Tin T. Win, M.D...

  18. High-Q plasmas in the TFTR tokamak

    NASA Astrophysics Data System (ADS)

    Jassby, D. L.; Barnes, C. W.; Bell, M. G.; Bitter, M.; Boivin, R.; Bretz, N. L.; Budny, R. V.; Bush, C. E.; Dylla, H. F.; Efthimion, P. C.; Fredrickson, E. D.; Hawryluk, R. J.; Hill, K. W.; Hosea, J.; Hsuan, H.; Janos, A. C.; Jobes, F. C.; Johnson, D. W.; Johnson, L. C.; Kamperschroer, J.; Kieras-Phillips, C.; Kilpatrick, S. J.; LaMarche, P. H.; LeBlanc, B.; Mansfield, D. K.; Marmar, E. S.; McCune, D. C.; McGuire, K. M.; Meade, D. M.; Medley, S. S.; Mikkelsen, D. R.; Mueller, D.; Owens, D. K.; Park, H. K.; Paul, S. F.; Pitcher, S.; Ramsey, A. T.; Redi, M. H.; Sabbagh, S. A.; Scott, S. D.; Snipes, J.; Stevens, J.; Strachan, J. D.; Stratton, B. C.; Synakowski, E. J.; Taylor, G.; Terry, J. L.; Timberlake, J. R.; Towner, H. H.; Ulrickson, M.; von Goeler, S.; Wieland, R. M.; Williams, M.; Wilson, J. R.; Wong, K.-L.; Young, K. M.; Zarnstorff, M. C.; Zweben, S. J.

    1991-08-01

    In the Tokamak Fusion Test Reactor (TFTR) [Plasma Phys. Controlled Fusion 26, 11 (1984)], the highest neutron source strength Sn and D-D fusion power gain QDD are realized in the neutral-beam-fueled and heated ``supershot'' regime that occurs after extensive wall conditioning to minimize recycling. For the best supershots, Sn increases approximately as P1.8b. The highest-Q shots are characterized by high Te (up to 12 keV), Ti (up to 34 keV), and stored energy (up to 4.7 MJ), highly peaked density profiles, broad Te profiles, and lower Zeff. Replacement of critical areas of the graphite limiter tiles with carbon-fiber composite tiles and improved alignment with the plasma have mitigated the ``carbon bloom.'' Wall conditioning by lithium pellet injection prior to the beam pulse reduces carbon influx and particle recycling. Empirically, QDD increases with decreasing pre-injection carbon radiation, and increases strongly with density peakedness [ne(0)/] during the beam pulse. To date, the best fusion results are Sn=5×1016 n/sec, QDD=1.85×10-3, and neutron yield=4.0×1016 n/pulse, obtained at Ip=1.6-1.9 MA and beam energy Eb=95-103 keV, with nearly balanced co- and counter-injected beam power. Computer simulations of supershot plasmas show that typically 50%-60% of Sn arises from beam-target reactions, with the remainder divided between beam-beam and thermonuclear reactions, the thermonuclear fraction increasing with Pb. The simulations predict that QDT=0.3-0.4 would be obtained for the best present plasma conditions, if half the deuterium neutral beams were to be replaced by tritium beams. Somewhat higher values are calculated if D beams are injected into a predominantly tritium target plasma. The projected central beta of fusion alphas is 0.4%-0.6%, a level sufficient for the study of alpha-induced collective effects.

  19. Collisionless microtearing modes in hot tokamaks: Effect of trapped electrons

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

    Swamy, Aditya K.; Ganesh, R., E-mail: ganesh@ipr.res.in; Brunner, S.

    2015-07-15

    Collisionless microtearing modes have recently been found linearly unstable in sharp temperature gradient regions of large aspect ratio tokamaks. The magnetic drift resonance of passing electrons has been found to be sufficient to destabilise these modes above a threshold plasma β. A global gyrokinetic study, including both passing electrons as well as trapped electrons, shows that the non-adiabatic contribution of the trapped electrons provides a resonant destabilization, especially at large toroidal mode numbers, for a given aspect ratio. The global 2D mode structures show important changes to the destabilising electrostatic potential. The β threshold for the onset of the instabilitymore » is found to be generally downshifted by the inclusion of trapped electrons. A scan in the aspect ratio of the tokamak configuration, from medium to large but finite values, clearly indicates a significant destabilizing contribution from trapped electrons at small aspect ratio, with a diminishing role at larger aspect ratios.« less

  20. Improving thermostability of phosphatidylinositol-synthesizing Streptomyces phospholipase D.

    PubMed

    Damnjanović, Jasmina; Takahashi, Rie; Suzuki, Atsuo; Nakano, Hideo; Iwasaki, Yugo

    2012-08-01

    Aimed to produce thermostable phosphatidylinositol (PI)-synthesizing phospholipase D (PLD), we initiated site-directed combinatorial mutagenesis followed by high-throughput screening. Previous site-directed combinatorial mutagenesis of wild-type Streptomyces PLD produced a mutant, DYR (W187D/Y191Y/Y385R) with PI-synthesizing ability. Deriving PI as a product of transphosphatidylation between phosphatidylcholine and myo-inositol, with myo-inositol in excess at high-temperature reaction conditions can increase yield due to enhanced solubility of this substrate. Thus, we improved DYR's thermostability by introduction of random mutations into selected amino acid positions having high B-factor. Screening of the libraries under restricted conditions yielded single-point mutants, specifically D40H, T291Y and R329G. Combinations of these point mutations yielded double (D40H/T291Y, D40H/R329G and T291Y/R329G) and triple (D40H/T291Y/R329G) mutants. PI synthesis at elevated temperatures pointed at D40H/T291Y as the most efficient enzyme. Circular dichroism analysis revealed D40H/T291Y to have increased melting temperature and postponed onset of thermal unfolding compared with DYR. Thermal tolerance study at 65°C confirmed D40H/T291Y's thermostability as its half-inactivation time was 8.7 min longer compared with DYR. This mutant had significantly less root-mean-square deviation change compared with DYR and showed no change in root-mean-square fluctuation when temperature shifts from 40 to 60°C, as determined by molecular dynamics analysis. Acquired different degrees of thermostability were also observed for several other DYR mutants.

  1. Hybrid neural network for density limit disruption prediction and avoidance on J-TEXT tokamak

    NASA Astrophysics Data System (ADS)

    Zheng, W.; Hu, F. R.; Zhang, M.; Chen, Z. Y.; Zhao, X. Q.; Wang, X. L.; Shi, P.; Zhang, X. L.; Zhang, X. Q.; Zhou, Y. N.; Wei, Y. N.; Pan, Y.; J-TEXT team

    2018-05-01

    Increasing the plasma density is one of the key methods in achieving an efficient fusion reaction. High-density operation is one of the hot topics in tokamak plasmas. Density limit disruptions remain an important issue for safe operation. An effective density limit disruption prediction and avoidance system is the key to avoid density limit disruptions for long pulse steady state operations. An artificial neural network has been developed for the prediction of density limit disruptions on the J-TEXT tokamak. The neural network has been improved from a simple multi-layer design to a hybrid two-stage structure. The first stage is a custom network which uses time series diagnostics as inputs to predict plasma density, and the second stage is a three-layer feedforward neural network to predict the probability of density limit disruptions. It is found that hybrid neural network structure, combined with radiation profile information as an input can significantly improve the prediction performance, especially the average warning time ({{T}warn} ). In particular, the {{T}warn} is eight times better than that in previous work (Wang et al 2016 Plasma Phys. Control. Fusion 58 055014) (from 5 ms to 40 ms). The success rate for density limit disruptive shots is above 90%, while, the false alarm rate for other shots is below 10%. Based on the density limit disruption prediction system and the real-time density feedback control system, the on-line density limit disruption avoidance system has been implemented on the J-TEXT tokamak.

  2. An experimental study of turbulence by phase-contrast imaging in the DIII-D tokamak

    NASA Astrophysics Data System (ADS)

    Coda, Stefano

    1997-10-01

    A CO2-laser imaging system employing the Zernike phase-contrast technique was designed, built, installed, and operated on the DIII-D tokamak. This system measures the line integrals of plasma density fluctuations along 16 vertical chords at the outer edge of the tokamak (0.85

  3. Human T lymphocytes express N-methyl-D-aspartate receptors functionally active in controlling T cell activation

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

    Miglio, Gianluca; Varsaldi, Federica; Lombardi, Grazia

    2005-12-30

    The aim of this study was to investigate the expression and the functional role of N-methyl-D-aspartate (NMDA) receptors in human T cells. RT-PCR analysis showed that human resting peripheral blood lymphocytes (PBL) and Jurkat T cells express genes encoding for both NR1 and NR2B subunits: phytohemagglutinin (PHA)-activated PBL also expresses both these genes and the NR2A and NR2D genes. Cytofluorimetric analysis showed that NR1 expression increases as a consequence of PHA (10 {mu}g/ml) treatment. D-(-)-2-Amino-5-phosphonopentanoic acid (D-AP5), and (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine [(+)-MK 801], competitive and non-competitive NMDA receptor antagonists, respectively, inhibited PHA-induced T cell proliferation, whereas they did not affect IL-2 (10more » U/ml)-induced proliferation of PHA blasts. These effects were due to the prevention of T cell activation (inhibition of cell aggregate formation and CD25 expression), but not to cell cycle arrest or death. These results demonstrate that human T lymphocytes express NMDA receptors, which are functionally active in controlling cell activation.« less

  4. Evaluation of negative results of BacT/Alert 3D automated blood culture system.

    PubMed

    Kocoglu, M Esra; Bayram, Aysen; Balci, Iclal

    2005-06-01

    Although automated continuous-monitoring blood culture systems are both rapid and sensitive, false-positive and false-negative results still occur. The objective of this study, then, was to evaluate negative results occurring with BacT/Alert 3D blood culture systems. A total of 1032 samples were cultured with the BacT/Alert 3D automated blood culture system, using both aerobic (FA) and anaerobic (FN) [corrected] media, and 128 of these samples yielded positive results. A total of 904 negative blood samples were then subcultured in 5% sheep blood agar, eosin methylene blue, chocolate agar, and sabouraud-dextrose agar. Organisms growing on these subcultures were subsequently identified using both Vitek32 (bioMerieux, Durham, NC) and conventional methods. Twenty four (2.6%) of the 904 subcultures grew on the subculture media. The majority (83.3%) of these were determined to be gram-positive microorganisms. Fourteen (58.3%) were coagulase-negative staphylococci, two (8.3%) were Bacillus spp., one (4.2%) was Staphylococcus aureus, and one (4.2%) was identified as Enterococcus faecium. Streptococcus pneumoniae and Neisseria spp. were isolated together in two (8.3%) vials. Gram-negative microorganisms comprised 12.5% of the subcultures, of which two (8.3%) were found to be Pseudomonas aeruginosa, and one (4.2%) was Pseudomonas fluorescens. The other isolate (4.2%) was identified as Candida albicans. We conclude that the subculture of negative results is valuable in the BacT/Alert 3D system, especially in situations in which only one set of blood cultures is taken.

  5. Applications of Collisional Radiative Modeling of Helium and Deuterium for Image Tomography Diagnostic of Te, Ne, and ND in the DIII-D Tokamak

    NASA Astrophysics Data System (ADS)

    Munoz Burgos, J. M.; Brooks, N. H.; Fenstermacher, M. E.; Meyer, W. H.; Unterberg, E. A.; Schmitz, O.; Loch, S. D.; Balance, C. P.

    2011-10-01

    We apply new atomic modeling techniques to helium and deuterium for diagnostics in the divertor and scrape-off layer regions. Analysis of tomographically inverted images is useful for validating detachment prediction models and power balances in the divertor. We apply tomographic image inversion from fast tangential cameras of helium and Dα emission at the divertor in order to obtain 2D profiles of Te, Ne, and ND (neutral ion density profiles). The accuracy of the atomic models for He I will be cross-checked against Thomson scattering measurements of Te and Ne. This work summarizes several current developments and applications of atomic modeling into diagnostic at the DIII-D tokamak. Supported in part by the US DOE under DE-AC05-06OR23100, DE-FC02-04ER54698, DE-AC52-07NA27344, and DE-AC05-00OR22725.

  6. Fusion gamma diagnostics

    NASA Astrophysics Data System (ADS)

    Medley, S. S.; Cecil, F. E.; Cole, D.; Conway, M. A.; Wilkinson, F. J., III

    1985-05-01

    Nuclear reactions of interest in fusion research often possess a branch yielding prompt emission of gamma radiation in excess of 15 MeV which can be exploited to provide a new fusion reaction diagnostic having applications similar to conventional neutron emission measurements. Conceptual aspects of fusion gamma diagnostics are discussed with emphasis on application to the Tokamak Fusion Test Reactor (TFTR) during deuterium neutral beam heating of D-T and D-3He plasmas. Recent measurements of the D (T, γ)5He, D(3He, γ)5Li, and D(D, γ)4He branching ratios at low center-of-mass energy (30-100 keV) and of the response of a large volume Ne226 detector for gamma detection in high neutron backgrounds are presented. Using a well-shielded Ne226 detector during 20 MW-120 kV deuterium beam heating of a tritium plasma in TFTR, the D(T, γ)5He gamma signal level is estimated to be 3.5×105 cps.

  7. Effects of Resonant Helical Field on Toroidal Field Ripple in IR-T1 Tokamak

    NASA Astrophysics Data System (ADS)

    Mahdavipour, B.; Salar Elahi, A.; Ghoranneviss, M.

    2018-02-01

    The toroidal magnetic field which is created by toroidal coils has the ripple in torus space. This magnetic field ripple has an importance in plasma equilibrium and stability studies in tokamak. In this paper, we present the investigation of the interaction between the toroidal magnetic field ripple and resonant helical field (RHF). We have estimated the amplitude of toroidal field ripples without and with RHF (with different q = m/n) ( m = 2, m = 3, m = 4, m = 5, m = 2 & 3, n = 1) using “Comsol Multiphysics” software. The simulations show that RHF has effects on the toroidal ripples.

  8. TRITIUM-LABELED COMPOUNDS VII. ISOTOPE EFFECTS IN THE OXIDATION OF d- MANNITOLS-C$sup 14$ AND d-MANNITOLS-t TO d-FRUCTOSES

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

    Sniegoski, L.T.; Frush, H.L.; Isbell, H.S.

    1961-09-01

    D-Mannitols, labeled either with carbon-14 at C1, C2, or C3, or with tritium attached to C1, C2, or C3, were prepared. After oxidation by Acetobacter suboxydans, the distribution of radioactivity in each of the resulting labeled D- fructoses was determined. Labeled D-mannitol is unique among the hexitols in that it may be oxidized by A. suboxydans in either the labeled or the unlabeled part of the molecule. Except in the oxidation of D-mannitol-2-t, the competing reactions result in the formation of a mixture of D-fructoses, each having radioactivity in one of two different positions. Hence, the isotope effect, k*/ k,more » (where k* and k are, respectively, the rate constants for oxidation in the labeled and in the unlabeled part of the labeled emannitol molecule) is the ratio of the activities at the two positions of the product, D-fructose. The following isotope effects were found for the bacterial oxidation of labeled D-mannitols: for D-mannitol-2-C/sup 14/, k*/k = 0.93; for Dmannitol-2-t, k*/k = 0.23; and for D-mannitol-3-t, k*/k = 0.70. For D-mannitols labeled at other positions, no isotope effect was detected, since k*/k was unity. The large isotope effect for D-mannitol-2-t is indicative of rupture of the C2-H bond in the rate determining process. It is suggested that the secondary isotope effect for tritium at C3 indicates hyperconjugation of the C3 hydrogen atom in the activated enzyme-- substrate complex; the lack of such effect for tritium at C1 may be due to unfavorable steric conditions for hyperconjugation of the C1 hydrogen atoms in the complex. The following substances were prepared and their isotopic distributions determined: D-fructose1,6-C/sup 14/ and D-fructose-1,6-t (from 1- labeled D-mannitols); D-fructose-2,5-C/sup 14/ and D-fructose-5-t (from 2-labeled e-mannitols); and D-fructose-3,4-C/sup 14/ and D-fructose-3,4-t (from 3-labeled D- mannitols). A procedure, employing D-fructose-1,6-C/sup 14/ as an internal standard, was devised for the

  9. Preoperative detection of malignant liver tumors: Comparison of 3D-T2-weighted sequences with T2-weighted turbo spin-echo and single shot T2 at 1.5 T.

    PubMed

    Barat, Maxime; Soyer, Philippe; Dautry, Raphael; Pocard, Marc; Lo-Dico, Rea; Najah, Haythem; Eveno, Clarisse; Cassinotto, Christophe; Dohan, Anthony

    2018-03-01

    To assess the performances of three-dimensional (3D)-T2-weighted sequences compared to standard T2-weighted turbo spin echo (T2-TSE), T2-half-Fourier acquisition single-shot turbo spin-echo (T2-HASTE), diffusion weighted imaging (DWI) and 3D-T1-weighted VIBE sequences in the preoperative detection of malignant liver tumors. From 2012 to 2015, all patients of our institution undergoing magnetic resonance imaging (MRI) examination for suspected malignant liver tumors were prospectively included. Patients had contrast-enhanced 3D-T1-weighted, DWI, 3D-T2-SPACE, T2-HASTE and T2-TSE sequences. Imaging findings were compared with those obtained at follow-up, surgery and histopathological analysis. Sensitivities for the detection of malignant liver tumors were compared for each sequence using McNemar test. A subgroup analysis was conducted for HCCs. Image artifacts were analyzed and compared using Wilcoxon paired signed rank-test. Thirty-three patients were included: 13 patients had 40 hepatocellular carcinomas (HCC) and 20 had 54 liver metastases. 3D-T2-weighted sequences had a higher sensitivity than T2-weighted TSE sequences for the detection of malignant liver tumors (79.8% versus 68.1%; P < 0.001). The difference did not reach significance for HCC. T1-weighted VIBE and DWI had a higher sensitivity than T2-weighted sequences. 3D-T2-weighted-SPACE sequences showed significantly less artifacts than T2-weitghted TSE. 3D-T2-weighted sequences show very promising performances for the detection of liver malignant tumors compared to T2-weighted TSE sequences. Copyright © 2018 Elsevier B.V. All rights reserved.

  10. Realizing Steady State Tokamak Operation for Fusion Energy

    NASA Astrophysics Data System (ADS)

    Luce, T. C.

    2009-11-01

    Continuous operation of a tokamak for fusion energy has obvious engineering advantages, but also presents physics challenges beyond the achievement of conditions needed for a burning plasma. The power from fusion reactions and external sources must support both the pressure and the current equilibrium without inductive current drive, leading to demands on stability, confinement, current drive, and plasma-wall interactions that exceed those for pulsed tokamaks. These conditions have been met individually in the present generation of tokamaks, and significant progress has been made in the last decade to realize scenarios where the required conditions are obtained simultaneously. Tokamaks are now operated routinely without disruptions close to the ideal MHD pressure limit, as needed for steady-state operation. Scenarios that project to high fusion gain have been demonstrated where more than half of the current is supplied by the ``bootstrap'' current generated by the pressure gradient in the plasma. Fully noninductive sustainment has been obtained for about a resistive time (the longest intrinsic time scale in the confined plasma) with normalized pressure and confinement approaching those needed for demonstration of steady-state conditions in ITER. One key challenge remaining to be addressed is how to handle the demanding heat and particle fluxes expected in a steady-state tokamak without compromising the high level of core plasma performance. Rather than attempt a comprehensive historical survey, this review will start from the plasma requirements of a steady-state tokamak powerplant, illustrate with examples the progress made in both experimental and theoretical understanding, and point to the remaining physics challenges.

  11. A high yield neutron target for cancer therapy

    NASA Technical Reports Server (NTRS)

    Alger, D. L.; Steinberg, R.

    1972-01-01

    A rotating target was developed that has the potential for providing an initial yield of 10 to the 13th power neutrons per second by the T(d,n)He-4 reaction, and a useable lifetime in excess of 600 hours. This yield and lifetime are indicated for a 300 Kv and 30 mA deuteron accelerator and a 30 microns thick titanium tritide film formed of the stoichiometric compound TiT2. The potential for extended lifetime is made possible by incorporating a sputtering electrode that permits use of titanium tritide thicknesses much greater than the deuteron range. The electrode is used to remove in situ depleted titanium layers to expose fresh tritide beneath. The utilization of the rotating target as a source of fast neutrons for cancer therapy is discussed.

  12. Radial force on the vacuum chamber wall during thermal quench in tokamaks

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

    Pustovitov, V. D., E-mail: pustovitov-vd@nrcki.ru

    The radial force balance during a thermal quench in tokamaks is analyzed. As a rule, the duration τ{sub tp} of such events is much shorter than the resistive time τ{sub w} of the vacuum chamber wall. Therefore, the perturbations of the magnetic field B produced by the evolving plasma cannot penetrate the wall, which makes different the magnetic pressures on its inner and outer sides. The goal of this work is the analytical estimation of the resulting integral radial force on the wall. The plasma is considered axially symmetric; for the description of radial forces on the wall, the resultsmore » of V.D. Shafranov’s classical work [J. Nucl. Energy C 5, 251 (1963)] are used. Developed for tokamaks, the standard equilibrium theory considers three interacting systems: plasma, poloidal field coils, and toroidal field coils. Here, the wall is additionally incorporated with currents driven by ∂B/∂t≠0 accompanying the fast loss of the plasma thermal energy. It is shown that they essentially affect the force redistribution, thereby leading to large loads on the wall. The estimates prove that these loads have to be accounted for in the disruptive scenarios in large tokamaks.« less

  13. Effect of Magnetic Islands on Divertors in Tokamaks and Stellarators

    NASA Astrophysics Data System (ADS)

    Punjabi, Alkesh; Boozer, Allen

    2017-10-01

    Divertors are required for handling the plasma particle and heat exhausts on the walls in fusion plasmas. Relatively simple methods, models, and maps from field line Hamiltonian are developed to better understand the interaction of strong plasma shaping and magnetic islands on the size and behavior of the magnetic flux tubes that go from the plasma edge to the wall in non-axisymmetric system. This approach is applicable not only in tokamaks but also in stellarators. Stellarator diverters in which magnetic islands are dominant are called resonant and when shaping is dominant are called non-resonant. Optimized stellarators generally have sharp edges on their surface, but unlike the case for tokamaks these edges do not encircle the entire plasma, so they do not define an edge value for the rotational transform. The approach is used in the DIII-D tokamak. Computation results are consistent with the predictions of the models. Further simulations are being done to understand why the transition from an effective cubic to a linear increase in loss time and area of footprint occurs and whether this increase is discontinuous or not. This work is supported by the US DOE Grants DE-FG02-01ER54624 and DE-FG02-04ER54793 to Hampton University and DE-FG02-95ER54333 to Columbia University. This research used resources of the NERSC, supported by the Office of Science, US DOE, under Contract No. DE-AC02-05CH11231.

  14. Realizing steady-state tokamak operation for fusion energy

    NASA Astrophysics Data System (ADS)

    Luce, T. C.

    2011-03-01

    Continuous operation of a tokamak for fusion energy has clear engineering advantages but requires conditions beyond those sufficient for a burning plasma. The fusion reactions and external sources must support both the pressure and the current equilibrium without inductive current drive, leading to demands on stability, confinement, current drive, and plasma-wall interactions that exceed those for pulsed tokamaks. These conditions have been met individually, and significant progress has been made in the past decade to realize scenarios where the required conditions are obtained simultaneously. Tokamaks are operated routinely without disruptions near pressure limits, as needed for steady-state operation. Fully noninductive sustainment with more than half of the current from intrinsic currents has been obtained for a resistive time with normalized pressure and confinement approaching those needed for steady-state conditions. One remaining challenge is handling the heat and particle fluxes expected in a steady-state tokamak without compromising the core plasma performance.

  15. Internal transport barrier in tokamak and helical plasmas

    NASA Astrophysics Data System (ADS)

    Ida, K.; Fujita, T.

    2018-03-01

    The differences and similarities between the internal transport barriers (ITBs) of tokamak and helical plasmas are reviewed. By comparing the characteristics of the ITBs in tokamak and helical plasmas, the mechanisms of the physics for the formation and dynamics of the ITB are clarified. The ITB is defined as the appearance of discontinuity of temperature, flow velocity, or density gradient in the radius. From the radial profiles of temperature, flow velocity, and density the ITB is characterized by the three parameters of normalized temperature gradient, R/{L}T, the location, {ρ }{ITB}, and the width, W/a, and can be expressed by ‘weak’ ITB (small R/{L}T) or ‘strong’ (large R/{L}T), ‘small’ ITB (small {ρ }{ITB}) or ‘large’ ITB (large {ρ }{ITB}), and ‘narrow’ (small W/a) or ‘wide’ (large W/a). Three key physics elements for the ITB formation, radial electric field shear, magnetic shear, and rational surface (and/or magnetic island) are described. The characteristics of electron and ion heat transport and electron and impurity transport are reviewed. There are significant differences in ion heat transport and electron heat transport. The dynamics of ITB formation and termination is also discussed. The emergence of the location of the ITB is sometimes far inside the ITB foot in the steady-state phase and the ITB region shows radial propagation during the formation of the ITB. The non-diffusive terms in momentum transport and impurity transport become more dominant in the plasma with the ITB. The reversal of the sign of non-diffusive terms in momentum transport and impurity transport associated with the formation of the ITB reported in helical plasma is described. Non-local transport plays an important role in determining the radial profile of temperature and density. The spontaneous change in temperature curvature (second radial derivative of temperature) in the ITB region is described. In addition, the key parameters of the control of the

  16. Neural network evaluation of tokamak current profiles for real time control

    NASA Astrophysics Data System (ADS)

    Wróblewski, Dariusz

    1997-02-01

    Active feedback control of the current profile, requiring real-time determination of the current profile parameters, is envisioned for tokamaks operating in enhanced confinement regimes. The distribution of toroidal current in a tokamak is now routinely evaluated based on external (magnetic probes, flux loops) and internal (motional Stark effect) measurements of the poloidal magnetic field. However, the analysis involves reconstruction of magnetohydrodynamic equilibrium and is too intensive computationally to be performed in real time. In the present study, a neural network is used to provide a mapping from the magnetic measurements (internal and external) to selected parameters of the safety factor profile. The single-pass, feedforward calculation of output of a trained neural network is very fast, making this approach particularly suitable for real-time applications. The network was trained on a large set of simulated equilibrium data for the DIII-D tokamak. The database encompasses a large variety of current profiles including the hollow current profiles important for reversed central shear operation. The parameters of safety factor profile (a quantity related to the current profile through the magnetic field tilt angle) estimated by the neural network include central safety factor, q0, minimum value of q, qmin, and the location of qmin. Very good performance of the trained neural network both for simulated test data and for experimental datais demonstrated.

  17. Magnetic resonance imaging of focal cortical dysplasia: Comparison of 3D and 2D fluid attenuated inversion recovery sequences at 3T.

    PubMed

    Tschampa, Henriette J; Urbach, Horst; Malter, Michael; Surges, Rainer; Greschus, Susanne; Gieseke, Jürgen

    2015-10-01

    Focal cortical dysplasia (FCD) is a frequent finding in drug resistant epilepsy. The aim of our study was to evaluate an isotropic high-resolution 3-dimensional Fluid-attenuated inversion recovery sequence (3D FLAIR) at 3T in comparison to standard 2D FLAIR in the diagnosis of FCD. In a prospective study, 19 epilepsy patients with the MR diagnosis of FCD were examined with a sagittal 3D FLAIR sequence with modulated refocusing flip angle (slice thickness 1.10mm) and a 2D FLAIR in the coronal (thk. 3mm) and axial planes (thk. 2mm). Manually placed regions of interest were used for quantitative analysis. Qualitative image analysis was performed by two neuroradiologists in consensus. Contrast between gray and white matter (p ≤ 0.02), the lesion (p ≤ 0.031) or hyperintense extension to the ventricle (p ≤ 0.021) and white matter was significantly higher in 2D than in 3D FLAIR sequences. In the visual analysis there was no difference between 2D and 3D sequences. Conventional 2D FLAIR sequences yield a higher image contrast compared to the employed 3D FLAIR sequence in patients with FCDs. Potential advantages of 3D imaging using surface rendering or automated techniques for lesion detection have to be further elucidated. Copyright © 2015 Elsevier B.V. All rights reserved.

  18. Tokamaks

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

    Wesson, J

    1987-01-01

    The word tokamak derives from the Russian term, toroidalnaya kamera magnitaya (toroidal chamber magnetic). The device was invented in the Soviet Union in 1950 and has since developed into one of the chief ways in which it is hoped to obtain usable power from plasmas through thermonuclear fusion. The present is meant to be an introduction to those entering the field, to those already engaged in research, and to those who want to gain some understanding of what it's all about.

  19. Stability at high performance in the MAST spherical tokamak

    NASA Astrophysics Data System (ADS)

    Buttery, R. J.; Akers, R.; Arends, E.; Conway, N. J.; Counsell, G. F.; Cunningham, G.; Gimblett, C. G.; Gryaznevich, M.; Hastie, R. J.; Hole, M. J.; Lehane, I.; Martin, R.; Patel, A.; Pinfold, T.; Sauter, O.; Taylor, D.; Turri, G.; Valovic, M.; Walsh, M. J.; Wilson, H. R.; MAST Team

    2004-09-01

    The development of reliable H-modes on MAST, together with advances in heating power and a range of high spatial resolution diagnostics, has provided a platform to enable MAST to address some of the most important issues of tokamak stability. In particular the high bgr potential of the spherical tokamak is highlighted with stable operation at bgrN ~ 5-6, bgrT ~ 16% and bgrp up to ~2. Magnetic diagnostic evaluation of the global bgr parameters is independently confirmed by kinetic profile data. Calculations indicate that the bgrN values are in the vicinity of no-wall stability limits. Studies of neoclassical tearing modes (NTMs) have been extended to explore their effects and develop avoidance strategies. Experiments have demonstrated that sawteeth play a strong role in triggering NTMs—by avoiding large sawteeth a much higher bgrN value has been reached. The significance of NTMs is confirmed, with large islands observed using the 300 point Thomson scattering diagnostic, and locking of large n = 1 modes frequently leading to disruptions, which become more rapid at low q95. The role of error fields has been explored. H-mode plasmas are also limited by edge localized modes (ELMs), with confinement degraded as the ELM frequency rises. However, in contrast to the conventional tokamak, the ELMs in high performing regimes on MAST (HIPB98Y2 ~ 1) appear to be type III in nature. Modelling using the ELITE code, which incorporates finite n corrections, identifies instability to peeling modes, consistent with a type III interpretation. It also shows considerable scope to raise pressure gradients before ballooning type modes (perhaps associated with type I ELMs) occur. The calculations show that narrow pedestals can support much stronger pressure gradients than might be expected from simple n = infin ballooning calculations. Finally sawteeth are shown to degrade confinement by ~10-15% in particular cases examined. They are observed not to remove the q = 1 surface in the cases

  20. Measurement of the inclusive forward-backward t$$\\bar{t}$$ production asymmetry and its rapidity dependence dA fb/d(Δy)

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

    Strycker, Glenn Loyd

    2010-01-01

    Early measurements of a large forward-background asymmetry at the CDF and D0 experiments at Fermilab have generated much recent interest, but were hampered by large uncertainties. We present here a new measurement of the parton level forward-backward asymmetry of pair-produced top quarks, using a high-statistics sample with much improved precision. We study the rapidity, y top, of the top quark production angle with respect to the incoming parton momentum in both the lab and tmore » $$\\bar{t}$$ rest frames. We find the parton-level forward-backward asymmetries to be A fb p$$\\bar{t}$$ = 0.150 ± 0.050 stat ± 0.024 syst A fb t$$\\bar{t}$$ = 0.158 ± 0.072{sup stat} ± 0.024 syst. These results should be compared with the small p$$\\bar{p}$$ frame charge asymmetry expected in QCD at NLO, A fb = 0.050 ± 0.015. Additionally, we introduce a measurement of the A fb rapidity dependence dA fb/d(Δy). We find this to be A fb p$$\\bar{t}$$(|Δy| < 1.0) = 0.026 ± 0.104 stat ± 0.012 syst A fb p$$\\bar{t}$$(|Δy| > 1.0) = 0.611 ± 0.210 stat ± 0.246 syst which we compare with model predictions 0.039 ± 0.006 and 0.123 ± 0.018 for the inner and outer rapidities, respectively.« less

  1. Energy, Vacuum, Gas Fueling, and Security Systems for the Spherical Tokamak MEDUSA-CR

    NASA Astrophysics Data System (ADS)

    Gonzalez, Jeferson; Soto, Christian; Carvajal, Johan; Ribeiro, Celso

    2013-10-01

    The former spherical tokamak (ST) MEDUSA (Madison EDUcation Small Aspect.ratio tokamak, R < 0.14 m, a < 0.10 m, BT < 0.5 T, Ip < 40 kA, 3 ms pulse) is being recommissioned in Costa Rica Institute of Technology. The main objectives of the MEDUSA-CR project are training and to clarify several issues in relevant physics for conventional and mainly STs, including beta studies in bean-shaped ST plasmas, transport, heating and current drive via Alfvén wave, and natural divertor STs with ergodic magnetic limiter. We present here the energy, vacuum, gas fueling, and security systems for MEDUSA-CR device. The interface with the control and data acquisition systems based on National Instruments (NI) software (LabView) and hardware (on loan to our laboratory via NI-Costa Rica) are also presented. VIE-ITCR, IAEA-CRP contract 17592, National Instruments of Costa Rica.

  2. Magnetic Polarization Measurements of the Multi-modal Plasma Response to 3D fields in the EAST Tokamak

    DOE PAGES

    Logan, Nikolas; Cui, L.; Wang, Hui -Hui; ...

    2018-04-30

    A multi-modal plasma response to applied non-axisymmetric fields has been found in EAST tokamak plasmas. Here, multi-modal means the radial and poloidal structure of an individually driven toroidal harmonic is not fixed. The signature of such a multi-modal response is the magnetic polarization (ratio of radial and poloidal components) of the plasma response field measured on the low field side device mid-plane. A difference in the 3D coil phasing (the relative phase of two coil arrays) dependencies between the two responses is observed in response to n=2 fields in the same plasma for which the n=1 responses are well synchronized.more » Neither the maximum radial nor the maximum poloidal field response to n=2 fields agrees with the best applied phasing for mitigating edge localized modes, suggesting that the edge plasma response is not a dominant component of either polarization. GPEC modeling reproduces the discrepant phasing dependences of the experimental measurements, and confirms the edge resonances are maximized by the coil phasing that mitigates ELMs in the experiments. The model confirms the measured plasma response is not dominated by resonant current drive from the external field. Instead, non-resonant contributions play a large role in the diagnostic signal for both toroidal harmonics n=1 and n=2. The analysis in this paper demonstrates the ability of 3D modeling to connect external magnetic sensor measurements to the internal plasma physics and accurately predict optimal applied 3D field configurations in multi-modal plasmas.« less

  3. Magnetic Polarization Measurements of the Multi-modal Plasma Response to 3D fields in the EAST Tokamak

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

    Logan, Nikolas; Cui, L.; Wang, Hui -Hui

    A multi-modal plasma response to applied non-axisymmetric fields has been found in EAST tokamak plasmas. Here, multi-modal means the radial and poloidal structure of an individually driven toroidal harmonic is not fixed. The signature of such a multi-modal response is the magnetic polarization (ratio of radial and poloidal components) of the plasma response field measured on the low field side device mid-plane. A difference in the 3D coil phasing (the relative phase of two coil arrays) dependencies between the two responses is observed in response to n=2 fields in the same plasma for which the n=1 responses are well synchronized.more » Neither the maximum radial nor the maximum poloidal field response to n=2 fields agrees with the best applied phasing for mitigating edge localized modes, suggesting that the edge plasma response is not a dominant component of either polarization. GPEC modeling reproduces the discrepant phasing dependences of the experimental measurements, and confirms the edge resonances are maximized by the coil phasing that mitigates ELMs in the experiments. The model confirms the measured plasma response is not dominated by resonant current drive from the external field. Instead, non-resonant contributions play a large role in the diagnostic signal for both toroidal harmonics n=1 and n=2. The analysis in this paper demonstrates the ability of 3D modeling to connect external magnetic sensor measurements to the internal plasma physics and accurately predict optimal applied 3D field configurations in multi-modal plasmas.« less

  4. Applying the new gamma ray imager diagnostic to measurements of runaway electron Bremsstrahlung radiation in the DIII-D Tokamak (invited)

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

    Cooper, C. M., E-mail: coopercm@fusion.gat.com; Pace, D. C.; Paz-Soldan, C.

    2016-11-15

    A new gamma ray imager (GRI) is developed to probe the electron distribution function with 2D spatial resolution during runaway electron (RE) experiments at the DIII-D tokamak. The diagnostic is sensitive to 0.5–100 MeV gamma rays, allowing characterization of the RE distribution function evolution during RE growth and dissipation. The GRI consists of a lead “pinhole camera” mounted on the DIII-D midplane with 123 honeycombed tangential chords 20 cm wide that span the vessel interior. Up to 30 bismuth germanate (BGO) scintillation detectors capture RE bremsstrahlung radiation for Pulse Height Analysis (PHA) capable of discriminating up to 20 000 pulses permore » second. Digital signal processing routines combining shaping filters are performed during PHA to reject noise and record gamma ray energy. The GRI setup and PHA algorithms will be described and initial data from experiments will be presented. A synthetic diagnostic is developed to generate the gamma ray spectrum of a GRI channel given the plasma information and a prescribed distribution function. Magnetic reconstructions of the plasma are used to calculate the angle between every GRI sightline and orient and discriminate gamma rays emitted by a field-aligned RE distribution function.« less

  5. Applying the new gamma ray imager diagnostic to measurements of runaway electron Bremsstrahlung radiation in the DIII-D Tokamak (invited)

    DOE PAGES

    Cooper, C. M.; Pace, D. C.; Paz-Soldan, C.; ...

    2016-08-30

    A new gamma ray imager (GRI) is developed to probe the electron distribution function with 2D spatial resolution during runaway electron (RE) experiments at the DIII-D tokamak. The diagnostic is sensitive to 0.5-100 MeV gamma rays, allowing characterization of the RE distribution function evolution during RE growth and dissipation. The GRI consists of a lead "pinhole camera" mounted on the DIII-D midplane with 123 honeycombed tangential chords 20 cm wide that span the vessel interior. Up to 30 bismuth germanate (BGO) scintillation detectors capture RE bremsstrahlung radiation for Pulse Height Analysis (PHA) capable of discriminating up to 20,000 pulses permore » second. Digital signal processing routines combining shaping filters are performed during PHA to reject noise and record gamma ray energy. The GRI setup and PHA algorithms will be described and initial data from experiments will be presented. A synthetic diagnostic is developed to generate the gamma ray spectrum of a GRI channel given the plasma information and a prescribed distribution function. Furthermore, magnetic reconstructions of the plasma are used to calculate the angle between every GRI sightline and orient and discriminate gamma rays emitted by a field-aligned RE distribution function.« 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. Spatially resolved measurements of two-dimensional turbulent structures in DIII-D plasmas

    DOE PAGES

    Zemedkun, Samuel E.; Che, S.; Chen, Y.; ...

    2015-12-21

    Here, two-dimensional observations of spatially-coherent electron temperature fluctuations at drift wave scales (k ~1 cm -1) have been made using the electron cyclotron emission imaging (ECEI) diagnostic on the DIII-D tokamak. These measurements enable the extraction of spectral properties, including poloidal dispersion relations. Temperature fluctuation levels are found to be ˜ T e/< T e > = 1.2%, and the phase velocity of the fluctuations is found to be constant across frequencies, consistent with modes having real frequencies low compared to the rotation-induced Doppler shifts. Comparisons with radially global linear gyrokinetic simulations suggest that the observed modes may be trappedmore » electron modes (TEM).« less

  8. Energy Efficient IoT Data Collection in Smart Cities Exploiting D2D Communications.

    PubMed

    Orsino, Antonino; Araniti, Giuseppe; Militano, Leonardo; Alonso-Zarate, Jesus; Molinaro, Antonella; Iera, Antonio

    2016-06-08

    Fifth Generation (5G) wireless systems are expected to connect an avalanche of "smart" objects disseminated from the largest "Smart City" to the smallest "Smart Home". In this vision, Long Term Evolution-Advanced (LTE-A) is deemed to play a fundamental role in the Internet of Things (IoT) arena providing a large coherent infrastructure and a wide wireless connectivity to the devices. However, since LTE-A was originally designed to support high data rates and large data size, novel solutions are required to enable an efficient use of radio resources to convey small data packets typically exchanged by IoT applications in "smart" environments. On the other hand, the typically high energy consumption required by cellular communications is a serious obstacle to large scale IoT deployments under cellular connectivity as in the case of Smart City scenarios. Network-assisted Device-to-Device (D2D) communications are considered as a viable solution to reduce the energy consumption for the devices. The particular approach presented in this paper consists in appointing one of the IoT smart devices as a collector of all data from a cluster of objects using D2D links, thus acting as an aggregator toward the eNodeB. By smartly adapting the Modulation and Coding Scheme (MCS) on the communication links, we will show it is possible to maximize the radio resource utilization as a function of the total amount of data to be sent. A further benefit that we will highlight is the possibility to reduce the transmission power when a more robust MCS is adopted. A comprehensive performance evaluation in a wide set of scenarios will testify the achievable gains in terms of energy efficiency and resource utilization in the envisaged D2D-based IoT data collection.

  9. Energy Efficient IoT Data Collection in Smart Cities Exploiting D2D Communications

    PubMed Central

    Orsino, Antonino; Araniti, Giuseppe; Militano, Leonardo; Alonso-Zarate, Jesus; Molinaro, Antonella; Iera, Antonio

    2016-01-01

    Fifth Generation (5G) wireless systems are expected to connect an avalanche of “smart” objects disseminated from the largest “Smart City” to the smallest “Smart Home”. In this vision, Long Term Evolution-Advanced (LTE-A) is deemed to play a fundamental role in the Internet of Things (IoT) arena providing a large coherent infrastructure and a wide wireless connectivity to the devices. However, since LTE-A was originally designed to support high data rates and large data size, novel solutions are required to enable an efficient use of radio resources to convey small data packets typically exchanged by IoT applications in “smart” environments. On the other hand, the typically high energy consumption required by cellular communications is a serious obstacle to large scale IoT deployments under cellular connectivity as in the case of Smart City scenarios. Network-assisted Device-to-Device (D2D) communications are considered as a viable solution to reduce the energy consumption for the devices. The particular approach presented in this paper consists in appointing one of the IoT smart devices as a collector of all data from a cluster of objects using D2D links, thus acting as an aggregator toward the eNodeB. By smartly adapting the Modulation and Coding Scheme (MCS) on the communication links, we will show it is possible to maximize the radio resource utilization as a function of the total amount of data to be sent. A further benefit that we will highlight is the possibility to reduce the transmission power when a more robust MCS is adopted. A comprehensive performance evaluation in a wide set of scenarios will testify the achievable gains in terms of energy efficiency and resource utilization in the envisaged D2D-based IoT data collection. PMID:27338385

  10. 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.

  11. First Direct Observation of Runaway-Electron-Driven Whistler Waves in Tokamaks

    DOE PAGES

    Spong, D. A.; Heidbrink, W. W.; Paz-Soldan, C.; ...

    2018-04-11

    DIII-D experiments at low density (n e ~10 19 m -3) have directly measured whistler waves in the 100– 200 MHz range excited by multi-MeV runaway electrons. Whistler activity is correlated with runaway intensity (hard x-ray emission level), occurs in novel discrete frequency bands, and exhibits nonlinear limitcycle- like behavior. The measured frequencies scale with the magnetic field strength and electron density as expected from the whistler dispersion relation. The modes are stabilized with increasing magnetic field, which is consistent with wave-particle resonance mechanisms. The mode amplitudes show intermittent time variations correlated with changes in the electron cyclotron emission thatmore » follow predator-prey cycles. These can be interpreted as wave-induced pitch angle scattering of moderate energy runaways. The tokamak runaway-whistler mechanisms have parallels to whistler phenomena in ionospheric plasmas. The observations also open new directions for the modeling and active control of runaway electrons in tokamaks.« less

  12. First Direct Observation of Runaway-Electron-Driven Whistler Waves in Tokamaks

    NASA Astrophysics Data System (ADS)

    Spong, D. A.; Heidbrink, W. W.; Paz-Soldan, C.; Du, X. D.; Thome, K. E.; Van Zeeland, M. A.; Collins, C.; Lvovskiy, A.; Moyer, R. A.; Austin, M. E.; Brennan, D. P.; Liu, C.; Jaeger, E. F.; Lau, C.

    2018-04-01

    DIII-D experiments at low density (ne˜1019 m-3 ) have directly measured whistler waves in the 100-200 MHz range excited by multi-MeV runaway electrons. Whistler activity is correlated with runaway intensity (hard x-ray emission level), occurs in novel discrete frequency bands, and exhibits nonlinear limit-cycle-like behavior. The measured frequencies scale with the magnetic field strength and electron density as expected from the whistler dispersion relation. The modes are stabilized with increasing magnetic field, which is consistent with wave-particle resonance mechanisms. The mode amplitudes show intermittent time variations correlated with changes in the electron cyclotron emission that follow predator-prey cycles. These can be interpreted as wave-induced pitch angle scattering of moderate energy runaways. The tokamak runaway-whistler mechanisms have parallels to whistler phenomena in ionospheric plasmas. The observations also open new directions for the modeling and active control of runaway electrons in tokamaks.

  13. First Direct Observation of Runaway-Electron-Driven Whistler Waves in Tokamaks.

    PubMed

    Spong, D A; Heidbrink, W W; Paz-Soldan, C; Du, X D; Thome, K E; Van Zeeland, M A; Collins, C; Lvovskiy, A; Moyer, R A; Austin, M E; Brennan, D P; Liu, C; Jaeger, E F; Lau, C

    2018-04-13

    DIII-D experiments at low density (n_{e}∼10^{19}  m^{-3}) have directly measured whistler waves in the 100-200 MHz range excited by multi-MeV runaway electrons. Whistler activity is correlated with runaway intensity (hard x-ray emission level), occurs in novel discrete frequency bands, and exhibits nonlinear limit-cycle-like behavior. The measured frequencies scale with the magnetic field strength and electron density as expected from the whistler dispersion relation. The modes are stabilized with increasing magnetic field, which is consistent with wave-particle resonance mechanisms. The mode amplitudes show intermittent time variations correlated with changes in the electron cyclotron emission that follow predator-prey cycles. These can be interpreted as wave-induced pitch angle scattering of moderate energy runaways. The tokamak runaway-whistler mechanisms have parallels to whistler phenomena in ionospheric plasmas. The observations also open new directions for the modeling and active control of runaway electrons in tokamaks.

  14. First Direct Observation of Runaway-Electron-Driven Whistler Waves in Tokamaks

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

    Spong, D. A.; Heidbrink, W. W.; Paz-Soldan, C.

    DIII-D experiments at low density (n e ~10 19 m -3) have directly measured whistler waves in the 100– 200 MHz range excited by multi-MeV runaway electrons. Whistler activity is correlated with runaway intensity (hard x-ray emission level), occurs in novel discrete frequency bands, and exhibits nonlinear limitcycle- like behavior. The measured frequencies scale with the magnetic field strength and electron density as expected from the whistler dispersion relation. The modes are stabilized with increasing magnetic field, which is consistent with wave-particle resonance mechanisms. The mode amplitudes show intermittent time variations correlated with changes in the electron cyclotron emission thatmore » follow predator-prey cycles. These can be interpreted as wave-induced pitch angle scattering of moderate energy runaways. The tokamak runaway-whistler mechanisms have parallels to whistler phenomena in ionospheric plasmas. The observations also open new directions for the modeling and active control of runaway electrons in tokamaks.« less

  15. Tomographic reconstruction of tokamak plasma light emission using wavelet-vaguelette decomposition

    NASA Astrophysics Data System (ADS)

    Schneider, Kai; Nguyen van Yen, Romain; Fedorczak, Nicolas; Brochard, Frederic; Bonhomme, Gerard; Farge, Marie; Monier-Garbet, Pascale

    2012-10-01

    Images acquired by cameras installed in tokamaks are difficult to interpret because the three-dimensional structure of the plasma is flattened in a non-trivial way. Nevertheless, taking advantage of the slow variation of the fluctuations along magnetic field lines, the optical transformation may be approximated by a generalized Abel transform, for which we proposed in Nguyen van yen et al., Nucl. Fus., 52 (2012) 013005, an inversion technique based on the wavelet-vaguelette decomposition. After validation of the new method using an academic test case and numerical data obtained with the Tokam 2D code, we present an application to an experimental movie obtained in the tokamak Tore Supra. A comparison with a classical regularization technique for ill-posed inverse problems, the singular value decomposition, allows us to assess the efficiency. The superiority of the wavelet-vaguelette technique is reflected in preserving local features, such as blobs and fronts, in the denoised emissivity map.

  16. 3D isotropic T2-weighted fast spin echo (VISTA) versus 2D T2-weighted fast spin echo in evaluation of the calcaneofibular ligament in the oblique coronal plane.

    PubMed

    Park, H J; Lee, S Y; Choi, Y J; Hong, H P; Park, S J; Park, J H; Kim, E

    2017-02-01

    To investigate whether the image quality of three-dimensional (3D) volume isotropic fast spin echo acquisition (VISTA) magnetic resonance imaging (MRI) of the calcaneofibular ligament (CFL) view is comparable to that of 2D fast spin echo T2-weighted images (2D T2 FSE) for the evaluation of the CFL, and whether 3D VISTA can replace 2D T2 FSE for the evaluation of CFL injuries. This retrospective study included 76 patients who underwent ankle MRI with CFL views of both 2D T2 FSE MRI and 3D VISTA. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of both techniques were measured. The anatomical identification score and diagnostic performances were evaluated by two readers independently. The diagnostic performances of 3D VISTA and 2D T2 FSE were analysed by sensitivity, specificity, and accuracy for diagnosing CFL injury with reference standards of surgically or clinically confirmed diagnoses. Surgical correlation was performed in 29% of the patients, and clinical examination was used in those who did not have surgery (71%). The SNRs and CNRs of 3D VISTA were significantly higher than those of 2D T2 FSE. The anatomical identification scores on 3D VISTA were inferior to those on 2D T2 FSE, and the differences were statistically significant (p<0.05). There were no significant differences in diagnostic performance between the two sequences when diagnoses were classified as normal or abnormal. Although the image quality of 3D VISTA MRI of the CFL view is not equal to that of 2D T2 FSE for the anatomical evaluation of CFL, 3D VISTA has a diagnostic performance comparable to that of 2D T2 FSE for the diagnosis of CFL injuries. Copyright © 2016 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

  17. Design of tangential multi-energy SXR cameras for tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Yamazaki, H.; Delgado-Aparicio, L. F.; Pablant, N.; Hill, K.; Bitter, M.; Takase, Y.; Ono, M.; Stratton, B.

    2017-10-01

    A new synthetic diagnostic capability has been built to study the response of tangential multi-energy soft x-ray pin-hole cameras for arbitrary plasma densities (ne , D), temperature (Te) and ion concentrations (nZ). For tokamaks and future facilities to operate safely in a high-pressure long-pulse discharge, it is imperative to address key issues associated with impurity sources, core transport and high-Z impurity accumulation. Multi-energy soft xray imaging provides a unique opportunity for measuring, simultaneously, a variety of important plasma properties (e.g. Te, nZ and ΔZeff). These systems are designed to sample the continuum- and line-emission from low- to high-Z impurities (e.g. C, O, Al, Si, Ar, Ca, Fe, Ni and Mo) in multiple energy-ranges. These x-ray cameras will be installed in the MST-RFP, as well as NSTX-U and DIII-D tokamaks, measuring the radial structure of the photon emissivity with a radial resolution below 1 cm at a 500 Hz frame rate and a photon-energy resolution of 500 eV. The layout and response expected for the new systems will be shown for different plasma conditions and impurity concentrations. The effect of toroidal rotation driving poloidal asymmetries in the core radiation is also addressed for the case of NSTX-U.

  18. Plasma Turbulence Imaging via Beam Emission Spectroscopy in the Core of the DIII-D Tokamak

    NASA Astrophysics Data System (ADS)

    McKee, George R.; Fonck, Raymond J.; Gupta, Deepak K.; Schlossberg, David J.; Shafer, Morgan W.; Boivin, Réjean L.; Solomon, Wayne

    Beam Emission Spectroscopy (BES), a high-sensitivity, good spatial resolution imaging diagnostic system, has been deployed and recently upgraded and expanded at the DIII-D tokamak to better understand density fluctuations arising from plasma turbulence. The currently deployed system images density fluctuations over an approximately 5 × 7 cm region at the plasma mid-plane (radially scannable over 0.2 < r/a ≤ 1) with a 5 × 6 (radial × poloidal) grid of rectangular detection channels, with one microsecond time resolution. BES observes collisionally-induced, Doppler-shifted Dα fluorescence (λ = 652-655 nm) of injected deuterium neutral beam atoms. The diagnostic wavenumber sensitivity is approximately k⊥ < 2.5 cm-1, allowing measurement of longwavelength (k⊥ρI < 1) density fluctuations. The recent upgrade includes expanded fiber optics bundles, customdesigned high-transmission, sharp-edge interference filters, ultra fast collection optics, and enlarged photodiode detectors that together provide nearly an order of magnitude increase in sensitivity relative to an earlier generation BES system. The high sensitivity allows visualization of turbulence at normalized density fluctuation amplitudes of ‾n/n < 1%, typical of fluctuation levels in the core region. The imaging array allows for sampling over 2-3 turbulent eddy scale lengths, which captures the essential dynamics of eddy evolution, interaction and shearing.

  19. Toroidal Ampere-Faraday Equations Solved Simultaneously with CQL3D Fokker-Planck Time-Evolution

    NASA Astrophysics Data System (ADS)

    Harvey, R. W. (Bob); Petrov, Yu. V. (Yuri); Forest, C. B.; La Haye, R. J.

    2017-10-01

    A self-consistent, time-dependent toroidal electric field calculation is a key feature of a complete 3D Fokker-Planck kinetic distribution radial transport code for f(v,theta,rho,t). We discuss benchmarking and first applications of an implementation of the Ampere-Faraday equation for the self-consistent toroidal electric field, as applied to (1) resistive turn on of applied electron cyclotron current in the DIII-D tokamak giving initial back current adjacent to the direct CD region and having possible NTM stabilization implications, and (2) runaway electron production in tokamaks due to rapid reduction of the plasma temperature as occurs in pellet injection, massive gas injection, or a plasma disruption. Our previous results assuming a constant current density (Lenz' Law) model showed that prompt ``hot-tail runaways'' dominated ``knock-on'' and Dreicer ``drizzle'' runaways; we perform full-radius modeling and examine modifications due to the more complete Ampere-Faraday solution. Presently, the implementation relies on a fixed shape eqdsk, and this limitation will be addressed in future work. Research supported by USDOE FES award ER54744.

  20. Nucleosome core particles containing a poly(dA.dT) sequence element exhibit a locally distorted DNA structure.

    PubMed

    Bao, Yunhe; White, Cindy L; Luger, Karolin

    2006-08-25

    Poly(dA.dT) DNA sequence elements are thought to promote transcription by either excluding nucleosomes or by altering their structural or dynamic properties. Here, the stability and structure of a defined nucleosome core particle containing a 16 base-pair poly(dA.dT) element (A16 NCP) was investigated. The A16 NCP requires a significantly higher temperature for histone octamer sliding in vitro compared to comparable nucleosomes that do not contain a poly(dA.dT) element. Fluorescence resonance energy transfer showed that the interactions between the nucleosomal DNA ends and the histone octamer were destabilized in A16 NCP. The crystal structure of A16 NCP was determined to a resolution of 3.2 A. The overall structure was maintained except for local deviations in DNA conformation. These results are consistent with previous in vivo and in vitro observations that poly(dA.dT) elements cause only modest changes in DNA accessibility and modest increases in steady-state transcription levels.

  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. Spatial calibration of a tokamak neutral beam diagnostic using in situ neutral beam emission

    DOE PAGES

    Chrystal, Colin; Burrell, Keith H.; Grierson, Brian A.; ...

    2015-10-20

    Neutral beam injection is used in tokamaks to heat, apply torque, drive non-inductive current, and diagnose plasmas. Neutral beam diagnostics need accurate spatial calibrations to benefit from the measurement localization provided by the neutral beam. A new technique has been developed that uses in-situ measurements of neutral beam emission to determine the spatial location of the beam and the associated diagnostic views. This technique was developed to improve the charge exchange recombination diagnostic (CER) at the DIII-D tokamak and uses measurements of the Doppler shift and Stark splitting of neutral beam emission made by that diagnostic. These measurements contain informationmore » about the geometric relation between the diagnostic views and the neutral beams when they are injecting power. This information is combined with standard spatial calibration measurements to create an integrated spatial calibration that provides a more complete description of the neutral beam-CER system. The integrated spatial calibration results are very similar to the standard calibration results and derived quantities from CER measurements are unchanged within their measurement errors. Lastly, the methods developed to perform the integrated spatial calibration could be useful for tokamaks with limited physical access.« less

  3. Spatial calibration of a tokamak neutral beam diagnostic using in situ neutral beam emission

    NASA Astrophysics Data System (ADS)

    Chrystal, C.; Burrell, K. H.; Grierson, B. A.; Pace, D. C.

    2015-10-01

    Neutral beam injection is used in tokamaks to heat, apply torque, drive non-inductive current, and diagnose plasmas. Neutral beam diagnostics need accurate spatial calibrations to benefit from the measurement localization provided by the neutral beam. A new technique has been developed that uses in situ measurements of neutral beam emission to determine the spatial location of the beam and the associated diagnostic views. This technique was developed to improve the charge exchange recombination (CER) diagnostic at the DIII-D tokamak and uses measurements of the Doppler shift and Stark splitting of neutral beam emission made by that diagnostic. These measurements contain information about the geometric relation between the diagnostic views and the neutral beams when they are injecting power. This information is combined with standard spatial calibration measurements to create an integrated spatial calibration that provides a more complete description of the neutral beam-CER system. The integrated spatial calibration results are very similar to the standard calibration results and derived quantities from CER measurements are unchanged within their measurement errors. The methods developed to perform the integrated spatial calibration could be useful for tokamaks with limited physical access.

  4. Main-ion intrinsic toroidal rotation profile driven by residual stress torque from ion temperature gradient turbulence in the DIII-D tokamak

    DOE PAGES

    Grierson, B. A.; Wang, W. X.; Ethier, S.; ...

    2017-01-06

    Intrinsic toroidal rotation of the deuterium main ions in the core of the DIII-D tokamak is observed to transition from flat to hollow, forming an off-axis peak, above a threshold level of direct electron heating. Nonlinear gyrokinetic simulations show that the residual stress associated with electrostatic ion temperature gradient turbulence possesses the correct radial location and stress structure to cause the observed hollow rotation profile. Residual stress momentum flux in the gyrokinetic simulations is balanced by turbulent momentum diffusion, with negligible contributions from turbulent pinch. Finally, the prediction of the velocity profile by integrating the momentum balance equation produces amore » rotation profile that qualitatively and quantitatively agrees with the measured main-ion profile, demonstrating that fluctuation-induced residual stress can drive the observed intrinsic velocity profile.« less

  5. A mechanism for large divertor plasma energy loss via lithium radiation in tokamaks

    NASA Astrophysics Data System (ADS)

    Rognlien, T. D.; Meier, E. T.; Soukhanovskii, V. A.

    2012-10-01

    Lithium has been used as a wall-conditioning element in a number of tokamaks over the years, including TFTR, FTU, and NSTX, where core plasma energy confinement and particle control are often found to improve following such conditioning. Here the possible role of Li in providing substantial energy loss for divertor plasmas via line radiation is reported. A multi-charge-state 2D UEDGE fluid model is used where the hydrogenic and Li ions and neutrals are each evolved as separate species and separate equations are solved for the electron and ion temperatures. It is shown that a sufficient level of Li neutrals evolving from the divertor surface via sputtering or evaporation can induce energy detachment of the divertor plasma, yielding a strongly radiating zone near the divertor where ionization and recombination from/to neutral Li can radiate most of the power flowing into the scrape-off layer while maintaining low core contamination. A local peaking of Li emissivity for electron temperatures near 1 eV appears to play an important role in the detachment of the mixed deuterium/Li plasma. Evidence of such behavior from NSTX discharges will be discussed.

  6. 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

  7. Compact fusion energy based on the spherical tokamak

    NASA Astrophysics Data System (ADS)

    Sykes, A.; Costley, A. E.; Windsor, C. G.; Asunta, O.; Brittles, G.; Buxton, P.; Chuyanov, V.; Connor, J. W.; Gryaznevich, M. P.; Huang, B.; Hugill, J.; Kukushkin, A.; Kingham, D.; Langtry, A. V.; McNamara, S.; Morgan, J. G.; Noonan, P.; Ross, J. S. H.; Shevchenko, V.; Slade, R.; Smith, G.

    2018-01-01

    Tokamak Energy Ltd, UK, is developing spherical tokamaks using high temperature superconductor magnets as a possible route to fusion power using relatively small devices. We present an overview of the development programme including details of the enabling technologies, the key modelling methods and results, and the remaining challenges on the path to compact fusion.

  8. Field warming experiments shed light on the wheat yield response to temperature in China

    PubMed Central

    Zhao, Chuang; Piao, Shilong; Huang, Yao; Wang, Xuhui; Ciais, Philippe; Huang, Mengtian; Zeng, Zhenzhong; Peng, Shushi

    2016-01-01

    Wheat growth is sensitive to temperature, but the effect of future warming on yield is uncertain. Here, focusing on China, we compiled 46 observations of the sensitivity of wheat yield to temperature change (SY,T, yield change per °C) from field warming experiments and 102 SY,T estimates from local process-based and statistical models. The average SY,T from field warming experiments, local process-based models and statistical models is −0.7±7.8(±s.d.)% per °C, −5.7±6.5% per °C and 0.4±4.4% per °C, respectively. Moreover, SY,T is different across regions and warming experiments indicate positive SY,T values in regions where growing-season mean temperature is low, and water supply is not limiting, and negative values elsewhere. Gridded crop model simulations from the Inter-Sectoral Impact Model Intercomparison Project appear to capture the spatial pattern of SY,T deduced from warming observations. These results from local manipulative experiments could be used to improve crop models in the future. PMID:27853151

  9. Inorganic nanoparticle-based T1 and T1/T2 magnetic resonance contrast probes

    NASA Astrophysics Data System (ADS)

    Hu, Fengqin; Zhao, Yong Sheng

    2012-09-01

    Magnetic resonance imaging (MRI) yields high spatially resolved contrast with anatomical details for diagnosis, deeper penetration depth and rapid 3D scanning. To improve imaging sensitivity, adding contrast agents accelerates the relaxation rate of water molecules, thereby greatly increasing the contrast between specific issues or organs of interest. Currently, the majority of T1 contrast agents are paramagnetic molecular complexes, typically Gd(iii) chelates. Various nanoparticulate T1 and T1/T2 contrast agents have recently been investigated as novel agents possessing the advantages of both the T1 contrast effect and nanostructural characteristics. In this minireview, we describe the recent progress of these inorganic nanoparticle-based MRI contrast agents. Specifically, we mainly report on Gd and Mn-based inorganic nanoparticles and ultrasmall iron oxide/ferrite nanoparticles.

  10. 3D T2-weighted and Gd-EOB-DTPA-enhanced 3D T1-weighted MR cholangiography for evaluation of biliary anatomy in living liver donors.

    PubMed

    Cai, Larry; Yeh, Benjamin M; Westphalen, Antonio C; Roberts, John; Wang, Zhen J

    2017-03-01

    To investigate whether the addition of gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced 3D T1-weighted MR cholangiography (T1w-MRC) to 3D T2-weighted MRC (T2w-MRC) improves the confidence and diagnostic accuracy of biliary anatomy in living liver donors. Two abdominal radiologists retrospectively and independently reviewed pre-operative MR studies in 58 consecutive living liver donors. The second-order bile duct visualization on T1w- and T2w-MRC images was rated on a 4-point scale. The readers also independently recorded the biliary anatomy and their diagnostic confidence using (1) combined T1w- and T2w-MRC, and (2) T2w-MRC. In the 23 right lobe donors, the biliary anatomy at imaging and the imaging-predicted number of duct orifices at surgery were compared to intra-operative findings. T1w-MRC had a higher proportion of excellent visualization than T2w-MRC, 66% vs. 45% for reader 1 and 60% vs. 31% for reader 2. The median confidence score for biliary anatomy diagnosis was significantly higher with combined T1w- and T2w-MRC than T2w-MRC alone for both readers (Reader 1: 3 vs. 2, p < 0.001; Reader 2: 3 vs. 1, p < 0.001). Compared to intra-operative findings, the accuracy of imaging-predicted number of duct orifices using combined T1w-and T2w-MRC was significantly higher than that using T2w-MRC alone (p = 0.034 for reader 1, p = 0.0082 for reader 2). The addition of Gd-EOB-DTPA-enhanced 3D T1w-MRC to 3D T2w-MRC improves second-order bile duct visualization and increases the confidence in biliary anatomy diagnosis and the accuracy in the imaging-predicted number of duct orifices acquired during right lobe harvesting.

  11. Effects of 2D and 3D Error Fields on the SAS Divertor Magnetic Topology

    NASA Astrophysics Data System (ADS)

    Trevisan, G. L.; Lao, L. L.; Strait, E. J.; Guo, H. Y.; Wu, W.; Evans, T. E.

    2016-10-01

    The successful design of plasma-facing components in fusion experiments is of paramount importance in both the operation of future reactors and in the modification of operating machines. Indeed, the Small Angle Slot (SAS) divertor concept, proposed for application on the DIII-D experiment, combines a small incident angle at the plasma strike point with a progressively opening slot, so as to better control heat flux and erosion in high-performance tokamak plasmas. Uncertainty quantification of the error fields expected around the striking point provides additional useful information in both the design and the modeling phases of the new divertor, in part due to the particular geometric requirement of the striking flux surfaces. The presented work involves both 2D and 3D magnetic error field analysis on the SAS strike point carried out using the EFIT code for 2D equilibrium reconstruction, V3POST for vacuum 3D computations and the OMFIT integrated modeling framework for data analysis. An uncertainty in the magnetic probes' signals is found to propagate non-linearly as an uncertainty in the striking point and angle, which can be quantified through statistical analysis to yield robust estimates. Work supported by contracts DE-FG02-95ER54309 and DE-FC02-04ER54698.

  12. Calculation of impurity poloidal rotation from measured poloidal asymmetries in the toroidal rotation of a tokamak plasma.

    PubMed

    Chrystal, C; Burrell, K H; Grierson, B A; Groebner, R J; Kaplan, D H

    2012-10-01

    To improve poloidal rotation measurement capabilities on the DIII-D tokamak, new chords for the charge exchange recombination spectroscopy (CER) diagnostic have been installed. CER is a common method for measuring impurity rotation in tokamak plasmas. These new chords make measurements on the high-field side of the plasma. They are designed so that they can measure toroidal rotation without the need for the calculation of atomic physics corrections. Asymmetry between toroidal rotation on the high- and low-field sides of the plasma is used to calculate poloidal rotation. Results for the main impurity in the plasma are shown and compared with a neoclassical calculation of poloidal rotation.

  13. Tokamak und Stellarator - zwei Wege zur Fusionsenergie: Fusionsforschung

    NASA Astrophysics Data System (ADS)

    Milch, Isabella

    2006-07-01

    Im Laufe der Fusionsforschung haben sich zwei Bautypen für ein zukünftiges Kraftwerk als besonders aussichtsreich erwiesen: Tokamak und Stellarator. Mit dem geplanten Tokamak-Experimentalreaktor ITER steht die internationale Fusionsforschung vor der Demonstration eines Energie liefernden Plasmas. Parallel soll die in Greifswald entstehende Forschungsanlage Wendelstein 7-X die Kraftwerkstauglichkeit des alternativen Bauprinzips der Stellaratoren zeigen.

  14. Resistive edge mode instability in stellarator and tokamak geometries

    NASA Astrophysics Data System (ADS)

    Mahmood, M. Ansar; Rafiq, T.; Persson, M.; Weiland, J.

    2008-09-01

    Geometrical effects on linear stability of electrostatic resistive edge modes are investigated in the three-dimensional Wendelstein 7-X stellarator [G. Grieger et al., Plasma Physics and Controlled Nuclear Fusion Research 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. 3, p. 525] and the International Thermonuclear Experimental Reactor [Progress in the ITER Physics Basis, Nucl. Fusion 7, S1, S285 (2007)]-like equilibria. An advanced fluid model is used for the ions together with the reduced Braghinskii equations for the electrons. Using the ballooning mode representation, the drift wave problem is set as an eigenvalue equation along a field line and is solved numerically using a standard shooting technique. A significantly larger magnetic shear and a less unfavorable normal curvature in the tokamak equilibrium are found to give a stronger finite-Larmor radius stabilization and a more narrow mode spectrum than in the stellarator. The effect of negative global magnetic shear in the tokamak is found to be stabilizing. The growth rate on a tokamak magnetic flux surface is found to be comparable to that on a stellarator surface with the same global magnetic shear but the eigenfunction in the tokamak is broader than in the stellarator due to the presence of large negative local magnetic shear (LMS) on the tokamak surface. A large absolute value of the LMS in a region of unfavorable normal curvature is found to be stabilizing in the stellarator, while in the tokamak case, negative LMS is found to be stabilizing and positive LMS destabilizing.

  15. Process gg{yields}h{sub 0}{yields}{gamma}{gamma} in the Lee-Wick standard model

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

    Krauss, F.; Underwood, T. E. J.; Zwicky, R.

    2008-01-01

    The process gg{yields}h{sub 0}{yields}{gamma}{gamma} is studied in the Lee-Wick extension of the standard model (LWSM) proposed by Grinstein, O'Connell, and Wise. In this model, negative norm partners for each SM field are introduced with the aim to cancel quadratic divergences in the Higgs mass. All sectors of the model relevant to gg{yields}h{sub 0}{yields}{gamma}{gamma} are diagonalized and results are commented on from the perspective of both the Lee-Wick and higher-derivative formalisms. Deviations from the SM rate for gg{yields}h{sub 0} are found to be of the order of 15%-5% for Lee-Wick masses in the range 500-1000 GeV. Effects on the rate formore » h{sub 0}{yields}{gamma}{gamma} are smaller, of the order of 5%-1% for Lee-Wick masses in the same range. These comparatively small changes may well provide a means of distinguishing the LWSM from other models such as universal extra dimensions where same-spin partners to standard model fields also appear. Corrections to determinations of Cabibbo-Kobayashi-Maskawa (CKM) elements |V{sub t(b,s,d)}| are also considered and are shown to be positive, allowing the possibility of measuring a CKM element larger than unity, a characteristic signature of the ghostlike nature of the Lee-Wick fields.« less

  16. Neural network evaluation of tokamak current profiles for real time control (abstract)

    NASA Astrophysics Data System (ADS)

    Wróblewski, Dariusz

    1997-01-01

    Active feedback control of the current profile, requiring real-time determination of the current profile parameters, is envisioned for tokamaks operating in enhanced confinement regimes. The distribution of toroidal current in a tokamak is now routinely evaluated based on external (magnetic probes, flux loops) and internal (motional Stark effect) measurements of the poloidal magnetic field. However, the analysis involves reconstruction of magnetohydrodynamic equilibrium and is too intensive computationally to be performed in real time. In the present study, a neural network is used to provide a mapping from the magnetic measurements (internal and external) to selected parameters of the safety factor profile. The single-pass, feedforward calculation of output of a trained neural network is very fast, making this approach particularly suitable for real-time applications. The network was trained on a large set of simulated equilibrium data for the DIII-D tokamak. The database encompasses a large variety of current profiles including the hollow current profiles important for reversed central shear operation. The parameters of safety factor profile (a quantity related to the current profile through the magnetic field tilt angle) estimated by the neural network include central safety factor, q0, minimum value of q, qmin, and the location of qmin. Very good performance of the trained neural network both for simulated test data and for experimental data is demonstrated.

  17. Prediction and realization of ITER-like pedestal pressure in the high- B tokamak Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Hughes, Jerry

    2017-10-01

    Fusion power in a burning plasma will scale as the square of the plasma pressure, which is increased in a straightforward way by increasing magnetic field: Pfus p2 B4 . Experiments on Alcator C-Mod, a compact high- B tokamak, have tested predictive capability for pedestal pressure, at toroidal field BT up to 8T , and poloidal field BP up to 1T . These reactor-like fields enable C-Mod to approach an ITER predicted value of 90kPa . This is expected if, as in the EPED model, the pedestal is constrained by onset of kinetic ballooning modes (KBMs) and peeling-ballooning modes (PMB), yielding a pressure pedestal approximately as pped BT ×BP . One successful path to high confinement on C-Mod is the high-density (ne > 3 ×1020m-3) approach, pursued using enhanced D-alpha (EDAs) H-mode. In EDA H-mode, transport regulates both the pedestal profiles and the core impurity content, holding the pedestal stationary, at just below the PBM stability boundary. We have extended this stationary ELM-suppressed regime to the highest magnetic fields achievable on C-Mod, and used it to approach the maximum pedestal predicted by EPED at high density: pped 60kPa . Another approach to high pressure utilizes a pedestal limited by PBMs at low collisionality, where pressure increases with density and EPED predicts access to a higher ``Super H'' solution for pped. Experiments at reduced density (ne < 2 ×1020m-3) and strong plasma shaping (δ > 0.5) accessed these regimes on C-Mod, producing pedestals with world record pped 80kPa , at Tped 2keV . In both the high and low density approaches, the impact of the pedestal on core performance is substantial. Our exploration of high pedestal regimes yielded a volume-averaged pressure 〈 p 〉 > 2atm , a world record value for a magnetic fusion device. The results hold promise for the projection of pedestal pressure and overall performance of high field burning plasma devices. Supported by U.S. Department of Energy awards DE-FC02-99ER54512, DE-FG02

  18. Scaling of the stochastic broadening from low mn, high mn, and peeling-ballooning magnetic perturbations in the DIII-D tokamak

    NASA Astrophysics Data System (ADS)

    Zhao, Michael; Punjabi, Alkesh; Ali, Halima

    2009-11-01

    The equilibrium EFIT data for the DIII-D shot 115467 is used to construct the equilibrium generating function for magnetic field line trajectories in the DIII-D tokamak in natural canonical coordinates [A. Punjabi, and H. Ali, Phys. Plasmas 15, 122502 (2008)]. A canonical transformation is used to construct an area-preserving map for field line trajectories in the natural canonical coordinates in the DIII-D. Maps in natural canonical coordinates have the advantage that natural canonical coordinates can be inverted to calculate real space coordinates (R,Z,φ), and there is no problem in crossing the separatrix. This is not possible for magnetic coordinates [O. Kerwin, A. Punjabi, and H. Ali, Phys. Plasmas 15, 072504 (2008)]. This map is applied to calculate stochastic broadening from the low mn (m,n)=(1,1)+(1,-1); high mn (m,n)=(4,1)+(3,1); and the peeling-ballooning (m,n)=(40,10)+(30,10) magnetic perturbations. In all three cases, the scaling of the widths of stochastic layer near the X-point in the principal plane of the DIII-D deviates at most by 6% from the .5ex1 -.1em/ -.15em.25ex2 power Boozer-Rechester scaling [A. Boozer, and A. Rechester, Phys. Fluids 21, 682 (1978)]. This work is supported by US Department of Energy grants DE-FG02-07ER54937, DE-FG02-01ER54624 and DE-FG02-04ER54793.

  19. A D-D/D-T fusion reaction based neutron generator system for liver tumor BNCT

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

    Koivunoro, H.; Lou, T.P.; Leung, K. N.

    2003-04-02

    Boron-neutron capture therapy (BNCT) is an experimental radiation treatment modality used for highly malignant tumor treatments. Prior to irradiation with low energetic neutrons, a 10B compound is located selectively in the tumor cells. The effect of the treatment is based on the high LET radiation released in the {sup 10}B(n,{alpha}){sup 7}Li reaction with thermal neutrons. BNCT has been used experimentally for brain tumor and melanoma treatments. Lately applications of other severe tumor type treatments have been introduced. Results have shown that liver tumors can also be treated by BNCT. At Lawrence Berkeley National Laboratory, various compact neutron generators based onmore » D-D or D-T fusion reactions are being developed. The earlier theoretical studies of the D-D or D-T fusion reaction based neutron generators have shown that the optimal moderator and reflector configuration for brain tumor BNCT can be created. In this work, the applicability of 2.5 MeV neutrons for liver tumor BNCT application was studied. The optimal neutron energy for external liver treatments is not known. Neutron beams of different energies (1eV < E < 100 keV) were simulated and the dose distribution in the liver was calculated with the MCNP simulation code. In order to obtain the optimal neutron energy spectrum with the D-D neutrons, various moderator designs were performed using MCNP simulations. In this article the neutron spectrum and the optimized beam shaping assembly for liver tumor treatments is presented.« less

  20. Resistive instabilities in tokamaks

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

    Rutherford, P.H.

    1985-10-01

    Low-m tearing modes constitute the dominant instability problem in present-day tokamaks. In this lecture, the stability criteria for representative current profiles with q(0)-values slightly less than unit are reviewed; ''sawtooth'' reconnection to q(0)-values just at, or slightly exceeding, unity is generally destabilizing to the m = 2, n = 1 and m = 3, n = 2 modes, and severely limits the range of stable profile shapes. Feedback stabilization of m greater than or equal to 2 modes by rf heating or current drive, applied locally at the magnetic islands, appears feasible; feedback by island current drive is much moremore » efficient, in terms of the radio-frequency power required, then feedback by island heating. Feedback stabilization of the m = 1 mode - although yielding particularly beneficial effects for resistive-tearing and high-beta stability by allowing q(0)-values substantially below unity - is more problematical, unless the m = 1 ideal-MHD mode can be made positively stable by strong triangular shaping of the central flux surfaces. Feedback techniques require a detectable, rotating MHD-like signal; the slowing of mode rotation - or the excitation of non-rotating modes - by an imperfectly conducting wall is also discussed.« less

  1. T.D.S. spectroscopic databank for spherical tops: DOS version

    NASA Astrophysics Data System (ADS)

    Tyuterev, V. G.; Babikov, Yu. L.; Tashkun, S. A.; Perevalov, V. I.; Nikitin, A.; Champion, J.-P.; Wenger, C.; Pierre, C.; Pierre, G.; Hilico, J.-C.; Loete, M.

    1994-10-01

    T.D.S. (Traitement de Donnees Spectroscopiques or Tomsk-Dijon-Spectroscopy project) is a computer package concerned with high resolution spectroscopy of spherical top molecules like CH4, CF4, SiH4, SiF4, SnH4, GeH4, SF6, etc. T.D.S. contains information, fundamental spectroscopic data (energies, transition moments, spectroscopic constants) recovered from comprehensive modeling and simultaneous fitting of experimental spectra, and associated software written in C. The T.D.S. goal is to provide an access to all available information on vibration-rotation molecular states and transitions including various spectroscopic processes (Stark, Raman, etc.) under extended conditions based on extrapolations of laboratory measurements using validated theoretical models. Applications for T.D.S. may include: education/training in molecular physics, quantum chemistry, laser physics; spectroscopic applications (analysis, laser spectroscopy, atmospheric optics, optical standards, spectroscopic atlases); applications to environment studies and atmospheric physics (remote sensing); data supply for specific databases; and to photochemistry (laser excitation, multiphoton processes). The reported DOS-version is designed for IBM and compatible personal computers.

  2. Magnetic polarization measurements of the multi-modal plasma response to 3D fields in the EAST tokamak

    NASA Astrophysics Data System (ADS)

    Logan, N. C.; Cui, L.; Wang, H.; Sun, Y.; Gu, S.; Li, G.; Nazikian, R.; Paz-Soldan, C.

    2018-07-01

    A multi-modal plasma response to applied non-axisymmetric fields has been found in EAST tokamak plasmas. Here, multi-modal means the radial and poloidal structure of an individually driven toroidal harmonic is not fixed. The signature of such a multi-modal response is the magnetic polarization (ratio of radial and poloidal components) of the plasma response field measured on the low field side device mid-plane. A difference in the 3D coil phasing (the relative phase of two coil arrays) dependencies between the two responses is observed in response to n  =  2 fields in the same plasma for which the n  =  1 responses are well synchronized. Neither the maximum radial nor the maximum poloidal field response to n  =  2 fields agrees with the best applied phasing for mitigating edge localized modes, suggesting that the edge plasma response is not a dominant component of either polarization. GPEC modeling reproduces the discrepant phasing dependences of the experimental measurements, and confirms the edge resonances are maximized by the coil phasing that mitigates ELMs in the experiments. The model confirms the measured plasma response is not dominated by resonant current drive from the external field. Instead, non-resonant contributions play a large role in the diagnostic signal for both toroidal harmonics n  =  1 and n  =  2. The analysis in this paper demonstrates the ability of 3D modeling to connect external magnetic sensor measurements to the internal plasma physics and accurately predict optimal applied 3D field configurations in multi-modal plasmas.

  3. Saturated internal instabilities in advanced-tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Hua, M.-D.; Chapman, I. T.; Pinches, S. D.; Hastie, R. J.; MAST Team

    2010-06-01

    "Advanced tokamak" (AT) scenarios were developed with the aim of reaching steady-state operation in future potential tokamak fusion power plants. AT scenarios exhibit non-monotonic to flat safety factor profiles (q, a measure of the magnetic field line pitch), with the minimum q (qmin) slightly above an integer value (qs). However, it has been predicted that these q profiles are unstable to ideal magnetohydrodynamic instabilities as qmin approaches qs. These ideal instabilities, observed and diagnosed as such for the first time in MAST plasmas with AT-like q profiles, have far-reaching consequences like confinement degradation, flattening of the toroidal core rotation or enhanced fast ion losses. These observations motivate the stability analysis of advanced-tokamak plasmas, with a view to provide guidance for stability thresholds in AT scenarios. Additionally, the measured rotation damping is compared to the self-consistently calculated predictions from neoclassical toroidal viscosity theory.

  4. Experimental search for the radiative capture reaction d + d {yields} {sup 4}He + {gamma} from the dd{mu} muonic molecule state J = 1

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

    Baluev, V. V.; Bogdanova, L. N.; Bom, V. R.

    2011-07-15

    A search for the muon-catalyzed fusion reaction d + d {yields} {sup 4}He + {gamma} in the dd{mu} muonic molecule was performed using the experimental installation TRITON with BGO detectors for {gamma}-quanta. A high-pressure target filled with deuterium was exposed to the negative muon beam of the JINR Phasotron to detect {gamma}-quanta with the energy 23.8 MeV. An experimental estimation for the yield of radiative deuteron capture from the dd{mu} state J = 1 was obtained at the level of {eta}{sub {gamma}} {<=} 8 Multiplication-Sign 10{sup -7} per fusion.

  5. The study of heat flux for disruption on experimental advanced superconducting tokamak

    NASA Astrophysics Data System (ADS)

    Yang, Zhendong; Fang, Jianan; Gong, Xianzu; Gan, Kaifu; Luo, Jiarong; Zhao, Hailin; Cui, Zhixue; Zhang, Bin; Chen, Meiwen

    2016-05-01

    Disruption of the plasma is one of the most dangerous instabilities in tokamak. During the disruption, most of the plasma thermal energy is lost, which causes damages to the plasma facing components. Infrared (IR) camera is an effective tool to detect the temperature distribution on the first wall, and the energy deposited on the first wall can be calculated from the surface temperature profile measured by the IR camera. This paper concentrates on the characteristics of heat flux distribution onto the first wall under different disruptions, including the minor disruption and the vertical displacement events (VDE) disruption. Several minor disruptions have been observed before the major disruption under the high plasma density in experimental advanced superconducting tokamak. During the minor disruption, the heat fluxes are mainly deposited on the upper/lower divertors. The magnetic configuration prior to the minor disruption is a lower single null with the radial distance between the two separatrices in the outer midplane dRsep = -2 cm, while it changes to upper single null (dRsep = 1.4 cm) during the minor disruption. As for the VDE disruption, the spatial distribution of heat flux exhibits strong toroidal and radial nonuniformity, and the maximum heat flux received on the dome plate can be up to 11 MW/m2.

  6. Prompt-gamma neutron activation analysis system design: Effects of D-T versus D-D neutron generator source selection

    USDA-ARS?s Scientific Manuscript database

    Prompt-gamma neutron activation (PGNA) analysis is used for the non-invasive measurement of human body composition. Advancements in portable, compact neutron generator design have made those devices attractive as neutron sources. Two distinct generators are available: D-D with 2.5 MeV and D-T with...

  7. Edge ohmic heating and improved confinement on HT-6M Tokamak

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

    Gao, X.

    1995-04-01

    An improved confinement has been observed on HT-6M tokamak after application of Edge Ohmic Heating (EOH) which makes plasma current rapidly ramp up from an initial steady state (I{sub p}=55 kA) within a small time scale (0.4 ms) to a second steady state (I{sub p}=60 kA) with a ramp rate of 12 MA/sec. The improved confinement is characterized by (a) increased average density n{sub e}; (b) reduced H{sub alpha} radiation; (c) reduced density fluctuations both in the center and at the edge; (d) a steeper n{sub e} and T{sub e} profile at the edge; (e) the changed profiles of plasmamore » parameters n{sub e}(r), q(r) and j(r); (f) transferred the oscillation modes of the soft-X ray signals from Mirnov fluctuation (12 kHz) to sawtooth oscillation (1.7 kHz). The changes of edge fluctuation, radial electric field and bremsstrahlung during EOH were measured and discussed in details. The measured values of {beta}{sub p}+l{sub i}/2 and soft-X ray sawtooth inversion radius implied the anomalous current penetration. 10 refs., 2 figs.« less

  8. The DIII-D Map -- An Area-Preserving Map for Trajectories of Magnetic Field Lines in the DIII-D Tokamak

    NASA Astrophysics Data System (ADS)

    Punjabi, Alkesh; Ali, Halima; Boozer, Allen; Evans, Todd

    2007-11-01

    The EFIT data for the DIII-D shot 115467 3000 ms is used to calculate the generating function for an area-preserving map for trajectories of magnetic field lines in the DIII-D. We call this map the DIII-D map. The generating function is a bivariate polynomial in base vectors &1/2circ;cos(θ) and &1/2circ;sin(θ). ψ is toroidal flux and θ is poloidal angle. The generating function is calculated using a canonical transformation from (ψ,θ) to physical coordinates (R,Z) in the DIII-D [1] and nonlinear regression. The equilibrium generating function gives an excellent representation of the equilibrium flux surfaces in the DIII-D. The DIII-D map is then used to calculate effects of the magnetic perturbations in the DIII-D. Preliminary results of the DIII-D map will be presented. This work is supported by US DOE OFES DE-FG02-01ER54624 and DE-FG02-04ER54793. [1] A. Punjabi, H. Ali, T. Evans, and A. Boozer, Phys Lett A 364 140--145 (2007).

  9. Continuum kinetic modeling of the tokamak plasma edge

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

    Dorf, M. A.; Dorr, M. R.; Hittinger, J. A.

    2016-05-15

    The first 4D (axisymmetric) high-order continuum gyrokinetic transport simulations that span the magnetic separatrix of a tokamak are presented. The modeling is performed with the COGENT code, which is distinguished by fourth-order finite-volume discretization combined with mapped multiblock grid technology to handle the strong anisotropy of plasma transport and the complex X-point divertor geometry with high accuracy. The calculations take into account the effects of fully nonlinear Fokker-Plank collisions, electrostatic potential variations, and anomalous radial transport. Topics discussed include: (a) ion orbit loss and the associated toroidal rotation and (b) edge plasma relaxation in the presence of anomalous radial transport.

  10. Control of Post-disruption Runaway Electron Beams in the DIII-D Tokamak

    NASA Astrophysics Data System (ADS)

    Eidietis, N. W.

    2011-10-01

    Recent experiments on DIII-D have demonstrated real-time control of post-disruption runaway electron (RE) beams, presenting the possibility for slow, controlled dissipation of the beam energy. RE beams will present a greater challenge to ITER than present tokamaks due to ITER's high RE avalanche gain constant [Nucl.Fusion 37, 1355-62 (1997)] and the difficulty repairing potential damage to its first wall. In the rare event that disruption control and mitigation schemes fail to suppress RE generation, active control of the RE beam may be an important line of defense to prevent rapid, localized deposition of RE beam energy on the first wall. Initially, sustaining a RE beam plateau requires avoiding radial collapse of the beam into the inner wall during the first 1-2 wall penetration times following the current quench (CQ). This collapse is caused by attractive induced currents in the wall and a lack of radial equilibrium with slow vertical field coils. The collapse is avoided by slewing the inner PF coils to push the RE beam off the wall while reducing the outer PF coil currents. Beam survival through this phase requires sufficient RE plateau current (IRE) and power supply slew rates to re-establish equilibrium. Following that transient period, RE beam vertical position was dynamically controlled, and stabilization was maintained in an elongated (κ <= 1 . 8) DND configuration for up 250ms. Most controlled RE beams end in a rapid vertical displacement event (VDE), indicating that the profiles evolve even as the position is controlled. Experimental radial evolution and VDE onset are shown to be consistent with theoretical calculations of controllability boundaries. However, ohmic regulation of IRE has been shown to delay VDEs to the pre-programmed ramp-down time, indicating that steady-state control may be achievable. Supported by the US DOE under DE-FC02-04ER54698.

  11. High-beta spherical tokamak startup in TS-4 merging experiment by use of toroidal field ramp-up

    NASA Astrophysics Data System (ADS)

    Kaminou, Yasuhiro; , Toru, II; Kato, Joji; Inomoto, Michiaki; Ono, Yasushi; TS Group Team; National InstituteFusion Science Collaboration

    2014-10-01

    We demonstrated the formation method of an ultrahigh-beta spherical tokamak by use of a field-reversed configuration and a spheromak in TS-4 device (R ~ 0.5 m, A ~ 1.5, Ip ~ 30-100 kA, B ~ 100 mT). This method is composed of the following steps: 1. Two spheromaks are merged together and a high-beta spheromak or FRC is formed by reconnection heating. 2. External toroidal magnetic field is added (current rising time ~50 μs), and spherical tokamak-like configuration is formed. In this way, the ultrahigh-beta ST is formed. The ultrahigh-beta ST formed by FRC has a diamagnetic toroidal field, and it presumed to be in a second-stable state for ballooning stability, and the one formed by spheromak has a weak paramagnetic toroidal magnetic field, while a spheormak has a strong paramagnetic toroidal magnetic field. This diamagnetic current derives from inductive electric field by ramping up the external toroidal magnetic field, and the diamagnetic current sustains high thermal pressure of the ultrahigh-beta spherical tokamak. And the beta of the ultrahigh-beta ST formed by FRC reaches about 50%. To sustain the high-beta state, 0.6 MW neutral beam injection and center solenoid coils are installed to the TS-4 device. In the poster, we report the experimental results of ultrahigh-beta spherical tokamak startup and sustainment by NBI and CS current driving experiment.

  12. First results from gamma ray diagnostics in EAST Tokamak

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

    Zhou, R. J.; Hu, L. Q.; Zhong, G. Q., E-mail: gqzhong@ipp.ac.cn

    2016-11-15

    Gamma ray diagnostics has been developed in the EAST tokamak recently. Six BGO scintillator detectors are arranged on the down-half cross-section and pointed at the up-half cross-section of plasma, with space resolution about 15 cm and energy range from 0.3 MeV to 6 MeV. Three main gamma ray peaks in the energy spectra have been observed and are identified as the results of nuclear reactions {sup 207}Pb(n, n′){sup 207m}Pb, H(n, γ) D, and D(p, γ){sup 3}He, respectively. Upgrading of the system is in progress by using LaBr3(Ce) scintillator, fast photo-multiplier tubes, and a fully digital data acquisition system based onmore » high sample frequency digitizers with digital pulse processing algorithms.« less

  13. Structure of the classical scrape-off layer of a tokamak

    NASA Astrophysics Data System (ADS)

    Rozhansky, V.; Kaveeva, E.; Senichenkov, I.; Vekshina, E.

    2018-03-01

    The structure of the scrape-off layer (SOL) of a tokamak with little or no turbulent transport is analyzed. The analytical estimates of the density and electron temperature fall-off lengths of the SOL are put forward. It is demonstrated that the SOL width could be of the order of the ion poloidal gyroradius, as suggested in Goldston (2012 Nuclear Fusion 52 013009). The analytical results are supported by the results of the 2D simulations of the edge plasma with reduced transport coefficients performed by SOLPS-ITER transport code.

  14. Laser flash photolysis of ozone - O/1D/ quantum yields in the fall-off region 297-325 nm

    NASA Technical Reports Server (NTRS)

    Brock, J. C.; Watson, R. T.

    1980-01-01

    The wavelength dependence of the quantum yield for O(1D) production from ozone photolysis has been determined between 297.5 nm and 325 nm in order to resolve serious discrepancies among previous studies. The results of this investigation are compared to earlier work by calculating atmospheric production rate constants for O(1D). It is found that for the purpose of calculating this rate constant, there is now good agreement among three studies at 298 K. Furthermore, it appears that previous data on the temperature dependence of the O(1D) quantum yield fall-off is adequate for determining the vertical profile of the O(1D) production rate constant. Several experimental difficulties associated with using NO2(asterisk) chemiluminescence to monitor O(1D) have been identified.

  15. SU-E-T-202: Comparison of 4D-Measurement-Guided Dose Reconstructions (MGDR) with COMPASS and OCTAVIUS 4D System

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

    Leung, R; Wong, M; Lee, V

    2015-06-15

    Purpose: To cross-validate the MGDR of COMPASS (IBA dosimetry, GmbH, Germany) and OCTAVIUS 4D system (PTW, Freiburg, Germany). Methods: Volumetric-modulated arc plans (5 head-and-neck and 3 prostate) collapsed to 40° gantry on the OCTAVIUS 4D phantom in QA mode on Monaco v5.0 (Elekta, CMS, Maryland Heights, MO) were delivered on a Elekta Agility linac. This study was divided into two parts: (1) error-free measurements by gantry-mounted EvolutionXX 2D array were reconstructed in COMPASS (IBA dosimetry, GmbH, Germany), and by OCTAVIUS 1500 array in Versoft v6.1 (PTW, Freiburg, Germany) to obtain the 3D doses (COM4D and OCTA4D). COM4D and OCTA4D weremore » compared to the raw measurement (OCTA3D) at the same detector plane for which OCTAVIUS 1500 was perpendicular to 0° gantry axis while the plans were delivered at gantry 40°; (2) beam steering errors of energy (Hump=-2%) and symmetry (2T=+2%) were introduced during the delivery of 5 plans to compare the MGDR doses COM4D-Hump (COM4D-2T), OCTA4D-Hump (OCTA4D-2T), with raw doses OCTA3D-Hump (OCTA3D-2T) and with OCTA3D to assess the error reconstruction and detection ability of MGDR tools. All comparisons used Υ-criteria of 2%(local dose)/2mm and 3%/3mm. Results: Averaged Υ passing rates were 85% and 96% for COM4D,and 94% and 99% for OCTA4D at 2%/2mm and 3%/3mm criteria respectively. For error reconstruction, COM4D-Hump (COM4D-2T) showed 81% (93%) at 2%/2mm and 94% (98%) at 3%/3mm, while OCTA4D-Hump (OCTA4D-2T) showed 96% (96%) at 2%/2mm and 99% (99%) at 3%/3mm. For error detection, OCTA3D doses were compared to COM4D-Hump (COM4D-2T) showing Υ passing rates of 93% (93%) at 2%/2mm and 98% (98%), and to OCTA4D-Hump (OCTA4D -2T) showing 94% (99%) at 2%/2mm and 81% (96%) at 3%/3mm, respectively. Conclusion: OCTAVIUS MGDR showed better agreement to raw measurements in both error- and error-free comparisons. COMPASS MGDR deviated from the raw measurements possibly owing to beam modeling uncertainty.« less

  16. Runaway electrons in tokamaks

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

    Liu, Chang

    The generation of runaway electrons is a complex and important phenomenon that impacts many areas of plasma physics. Due to the decrease of electron collision frequency with increasing velocity, electrons under strong electric field can experience unlimited “runaway” acceleration. In tokamaks, runaway electrons can be produced in disruptions, due to the strong inductive electric field formed as the thermal energy of plasma gets rapidly lost. This population of runaway electrons can undergo an exponential growth, denoted the runaway electron avalanche, due to hard collisions between relativistic runaway electrons and low energy electrons. It is predicted that in a large tokamakmore » device like the International Thermonuclear Experimental Reactor (ITER), a runway electron beam generated in a disruption event can potentially cause severe damage to the device, which poses a significant challenge for ITER to achieve its mission. It is therefore extremely important to seek an effective mitigation mechanism for runaway electrons. Experimental efforts have been made to study the properties of runaway electrons in tokamaks, including their generation, diffusion, and radiation. In order to understand these experimental results, extensive theoretical and simulation studies of runaway electron physics are required. The main topic of this thesis is to study the wave particle interaction associated with runaway electron beams in tokamaks. The runaway electrons can emit and absorb electromagnetic waves through resonances, and can be diffused in momentum space by the waves. Initially, we address the Cherenkov radiation of runaway electrons, which originates from the polarization of the plasma medium. The energy and momentum loss of the Cherenkov radiation can be modeled by adding a correction to the Coulomb logarithm in the collisional drag force. Subsequently, we address pitch angle scattering caused by normal modes in the plasma, which are driven unstable by the

  17. Enabling co-simulation of tokamak plant models and plasma control systems

    DOE PAGES

    Walker, M. L.

    2017-12-22

    A system for connecting the Plasma Control System and a model of the tokamak Plant in closed loop co-simulation for plasma control development has been in routine use at DIII-D for more than 20 years and at other fusion labs that use variants of the DIII-D PCS for approximately the last decade. Here, co-simulation refers to the simultaneous execution of two independent codes with the exchange of data - Plant actuator commands and tokamak diagnostic data - between them during execution. Interest in this type of PCS-Plant simulation technology has also been growing recently at other fusion facilities. In fact,more » use of such closed loop control simulations is assumed to play an even larger role in the development of both the ITER Plasma Control System (PCS) and the experimental operation of the ITER device, where they will be used to support verification/validation of the PCS and also for ITER pulse schedule development and validation. We describe the key use cases that motivate the co-simulation capability and the features that must be provided by the Plasma Control System to support it. These features could be provided by the PCS itself or by a model of the PCS. If the PCS itself is chosen to provide them, there are requirements imposed on its architecture. If a PCS model is chosen, there are requirements imposed on the initial implementation of this simulation as well as long-term consequences for its continued development and maintenance. We describe these issues for each use case and discuss the relative merits of the two choices. Several examples are given illustrating uses of the co-simulation method to address problems of plasma control during the operation of DIII-D and of other devices that use the DIII-D PCS.« less

  18. Enabling co-simulation of tokamak plant models and plasma control systems

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

    Walker, M. L.

    A system for connecting the Plasma Control System and a model of the tokamak Plant in closed loop co-simulation for plasma control development has been in routine use at DIII-D for more than 20 years and at other fusion labs that use variants of the DIII-D PCS for approximately the last decade. Here, co-simulation refers to the simultaneous execution of two independent codes with the exchange of data - Plant actuator commands and tokamak diagnostic data - between them during execution. Interest in this type of PCS-Plant simulation technology has also been growing recently at other fusion facilities. In fact,more » use of such closed loop control simulations is assumed to play an even larger role in the development of both the ITER Plasma Control System (PCS) and the experimental operation of the ITER device, where they will be used to support verification/validation of the PCS and also for ITER pulse schedule development and validation. We describe the key use cases that motivate the co-simulation capability and the features that must be provided by the Plasma Control System to support it. These features could be provided by the PCS itself or by a model of the PCS. If the PCS itself is chosen to provide them, there are requirements imposed on its architecture. If a PCS model is chosen, there are requirements imposed on the initial implementation of this simulation as well as long-term consequences for its continued development and maintenance. We describe these issues for each use case and discuss the relative merits of the two choices. Several examples are given illustrating uses of the co-simulation method to address problems of plasma control during the operation of DIII-D and of other devices that use the DIII-D PCS.« less

  19. Symplectic approach to calculation of magnetic field line trajectories in physical space with realistic magnetic geometry in divertor tokamaks

    NASA Astrophysics Data System (ADS)

    Punjabi, Alkesh; Ali, Halima

    2008-12-01

    A new approach to integration of magnetic field lines in divertor tokamaks is proposed. In this approach, an analytic equilibrium generating function (EGF) is constructed in natural canonical coordinates (ψ,θ) from experimental data from a Grad-Shafranov equilibrium solver for a tokamak. ψ is the toroidal magnetic flux and θ is the poloidal angle. Natural canonical coordinates (ψ,θ,φ) can be transformed to physical position (R,Z,φ) using a canonical transformation. (R,Z,φ) are cylindrical coordinates. Another canonical transformation is used to construct a symplectic map for integration of magnetic field lines. Trajectories of field lines calculated from this symplectic map in natural canonical coordinates can be transformed to trajectories in real physical space. Unlike in magnetic coordinates [O. Kerwin, A. Punjabi, and H. Ali, Phys. Plasmas 15, 072504 (2008)], the symplectic map in natural canonical coordinates can integrate trajectories across the separatrix surface, and at the same time, give trajectories in physical space. Unlike symplectic maps in physical coordinates (x,y) or (R,Z), the continuous analog of a symplectic map in natural canonical coordinates does not distort trajectories in toroidal planes intervening the discrete map. This approach is applied to the DIII-D tokamak [J. L. Luxon and L. E. Davis, Fusion Technol. 8, 441 (1985)]. The EGF for the DIII-D gives quite an accurate representation of equilibrium magnetic surfaces close to the separatrix surface. This new approach is applied to demonstrate the sensitivity of stochastic broadening using a set of perturbations that generically approximate the size of the field errors and statistical topological noise expected in a poloidally diverted tokamak. Plans for future application of this approach are discussed.

  20. Effect of Damping and Yielding on the Seismic Response of 3D Steel Buildings with PMRF

    PubMed Central

    Haldar, Achintya; Rodelo-López, Ramon Eduardo; Bojórquez, Eden

    2014-01-01

    The effect of viscous damping and yielding, on the reduction of the seismic responses of steel buildings modeled as three-dimensional (3D) complex multidegree of freedom (MDOF) systems, is studied. The reduction produced by damping may be larger or smaller than that of yielding. This reduction can significantly vary from one structural idealization to another and is smaller for global than for local response parameters, which in turn depends on the particular local response parameter. The uncertainty in the estimation is significantly larger for local response parameter and decreases as damping increases. The results show the limitations of the commonly used static equivalent lateral force procedure where local and global response parameters are reduced in the same proportion. It is concluded that estimating the effect of damping and yielding on the seismic response of steel buildings by using simplified models may be a very crude approximation. Moreover, the effect of yielding should be explicitly calculated by using complex 3D MDOF models instead of estimating it in terms of equivalent viscous damping. The findings of this paper are for the particular models used in the study. Much more research is needed to reach more general conclusions. PMID:25097892

  1. Effect of damping and yielding on the seismic response of 3D steel buildings with PMRF.

    PubMed

    Reyes-Salazar, Alfredo; Haldar, Achintya; Rodelo-López, Ramon Eduardo; Bojórquez, Eden

    2014-01-01

    The effect of viscous damping and yielding, on the reduction of the seismic responses of steel buildings modeled as three-dimensional (3D) complex multidegree of freedom (MDOF) systems, is studied. The reduction produced by damping may be larger or smaller than that of yielding. This reduction can significantly vary from one structural idealization to another and is smaller for global than for local response parameters, which in turn depends on the particular local response parameter. The uncertainty in the estimation is significantly larger for local response parameter and decreases as damping increases. The results show the limitations of the commonly used static equivalent lateral force procedure where local and global response parameters are reduced in the same proportion. It is concluded that estimating the effect of damping and yielding on the seismic response of steel buildings by using simplified models may be a very crude approximation. Moreover, the effect of yielding should be explicitly calculated by using complex 3D MDOF models instead of estimating it in terms of equivalent viscous damping. The findings of this paper are for the particular models used in the study. Much more research is needed to reach more general conclusions.

  2. Functions of NKG2D in CD8+ T cells: an opportunity for immunotherapy.

    PubMed

    Prajapati, Kushal; Perez, Cynthia; Rojas, Lourdes Beatriz Plaza; Burke, Brianna; Guevara-Patino, Jose A

    2018-02-05

    Natural killer group 2 member D (NKG2D) is a type II transmembrane receptor. NKG2D is present on NK cells in both mice and humans, whereas it is constitutively expressed on CD8 + T cells in humans but only expressed upon T-cell activation in mice. NKG2D is a promiscuous receptor that recognizes stress-induced surface ligands. In NK cells, NKG2D signaling is sufficient to unleash the killing response; in CD8 + T cells, this requires concurrent activation of the T-cell receptor (TCR). In this case, the function of NKG2D is to authenticate the recognition of a stressed target and enhance TCR signaling. CD28 has been established as an archetype provider of costimulation during T-cell priming. It has become apparent, however, that signals from other costimulatory receptors, such as NKG2D, are required for optimal T-cell function outside the priming phase. This review will focus on the similarities and differences between NKG2D and CD28; less well-described characteristics of NKG2D, such as the potential role of NKG2D in CD8 + T-cell memory formation, cancer immunity and autoimmunity; and the opportunities for targeting NKG2D in immunotherapy.Cellular and Molecular Immunology advance online publication, 5 February 2018; doi:10.1038/cmi.2017.161.

  3. Evidence for Direct CP Violation in the Measurement of the Cabbibo-Kobayashi-Maskawa Angle {gamma} with B{sup {+-}}{yields}D(*)K{sup (*){+-}} Decays

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

    Amo Sanchez, P. del; Lees, J. P.; Poireau, V.

    2010-09-17

    We report the measurement of the Cabibbo-Kobayashi-Maskawa CP-violating angle {gamma} through a Dalitz plot analysis of neutral D-meson decays to K{sub S}{sup 0}{pi}{sup +}{pi}{sup -} and K{sub S}{sup 0}K{sup +}K{sup -} produced in the processes B{sup {+-}}{yields}DK{sup {+-}}, B{sup {+-}}{yields}D*K{sup {+-}} with D*{yields}D{pi}{sup 0}, D{gamma}, and B{sup {+-}}{yields}DK*{sup {+-}} with K*{sup {+-}}{yields}K{sub S}{sup 0}{pi}{+-}, using 468 million BB pairs collected by the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider at SLAC. We measure {gamma}=(68{+-}14{+-}4{+-}3) deg. (modulo 180 deg.), where the first error is statistical, the second is the experimental systematic uncertainty, and the third reflects the uncertaintymore » in the description of the neutral D decay amplitudes. This result is inconsistent with {gamma}=0 (no direct CP violation) with a significance of 3.5 standard deviations.« less

  4. Modeling T1 and T2 relaxation in bovine white matter

    NASA Astrophysics Data System (ADS)

    Barta, R.; Kalantari, S.; Laule, C.; Vavasour, I. M.; MacKay, A. L.; Michal, C. A.

    2015-10-01

    The fundamental basis of T1 and T2 contrast in brain MRI is not well understood; recent literature contains conflicting views on the nature of relaxation in white matter (WM). We investigated the effects of inversion pulse bandwidth on measurements of T1 and T2 in WM. Hybrid inversion-recovery/Carr-Purcell-Meiboom-Gill experiments with broad or narrow bandwidth inversion pulses were applied to bovine WM in vitro. Data were analysed with the commonly used 1D-non-negative least squares (NNLS) algorithm, a 2D-NNLS algorithm, and a four-pool model which was based upon microscopically distinguishable WM compartments (myelin non-aqueous protons, myelin water, non-myelin non-aqueous protons and intra/extracellular water) and incorporated magnetization exchange between adjacent compartments. 1D-NNLS showed that different T2 components had different T1 behaviours and yielded dissimilar results for the two inversion conditions. 2D-NNLS revealed significantly more complicated T1/T2 distributions for narrow bandwidth than for broad bandwidth inversion pulses. The four-pool model fits allow physical interpretation of the parameters, fit better than the NNLS techniques, and fits results from both inversion conditions using the same parameters. The results demonstrate that exchange cannot be neglected when analysing experimental inversion recovery data from WM, in part because it can introduce exponential components having negative amplitude coefficients that cannot be correctly modeled with nonnegative fitting techniques. While assignment of an individual T1 to one particular pool is not possible, the results suggest that under carefully controlled experimental conditions the amplitude of an apparent short T1 component might be used to quantify myelin water.

  5. Pentopyranosyl Oligonucleotide Systems. Part 11: Systems with Shortened Backbones: D)-beta-Ribopyranosyl-(4 yields 3 )- and (L)-alpha - Lyxopyranosyl-(4 yields 3 )-oligonucleotides

    NASA Technical Reports Server (NTRS)

    Wippo, Harald; Reck, Folkert; Kudick, Rene; Ramaseshan, Mahesh; Ceulemans, Griet; Bolli, Martin; Krishnamurthy, Ramanarayanan; Eschenmoser, Albert

    2001-01-01

    The (L)-a-lyxopyranosyl-(4'yields 3')-oligonucleotide system-a member of a pentopyranosyl oligonucleotide family containing a shortened backbone-is capable of cooperative base-pairing and of cross-pairing with DNA and RNA. In contrast, corresponding (D)-beta-ribopyransoyl-(4' yields 3')-oligonucleotides do not show base-pairing under similar conditions. We conclude that oligonucleotide systems can violate the six-bonds-per-backbone-unit rule by having five bonds instead, if their vicinally bound phosphodiester bridges can assume an antiperiplanar conformation. An additional structural feature that seems relevant to the cross-pairing capability of the (L)-a-lyxopyranosyl-(4' yields 3')-oligonucleotide system is its (small) backbone/basepair axes inclination. An inclination which is similar to that in B-DNA seems to be a prerequisite for an oligonucleotide system s capability to cross-pair with DNA.

  6. Effect of electronic coupling of Watson-Crick hopping in DNA poly(dA)-poly(dT)

    NASA Astrophysics Data System (ADS)

    Risqi, A. M.; Yudiarsah, E.

    2017-07-01

    Charge transport properties of poly(dA)-poly(dT) DNA has been studied by using thigh binding Hamiltonian approach. Molecule DNA that we use consist of 32 base pair of adenine (A) and thymine (T) and backbone is consist of phosphate and sugar. The molecule DNA is contacted electrode at both ends. Charge transport in molecule DNA depend on the environment, we studied the effect of electronic coupling of Watson-Crick hopping in poly(dA)-poly(dT) DNA to transmission probability and characteristic I-V. The electronic coupling constant influence charge transport between adenine-thymine base pairs at the same site. Transmission probability is studied by using transfer matrix and scattering matrix method, and the result of transmission probability is used to calculate the characteristic I-V by using formula Landauer Buttiker. The result shows that when the electronic coupling increase then transmission probability and characteristic I-V increase slightly.

  7. Characterized the pattern of the material deposition in the HL-2A tokamak

    NASA Astrophysics Data System (ADS)

    Cai, Laizhong; Wang, Jianbao; Wu, Ting; Zeng, Xiaoxiao; Hai, Ran; Ding, Hongbin

    2017-03-01

    Since the divertor geometry of a tokamak has a strong impact on the material erosion and deposition on the wall and HL-2A has a unique divertor configuration, it is necessary to investigate the material deposition pattern in HL-2A although a few results on other tokamaks have already been published. In this paper, tiles retrieved from the vessel are analyzed ex-situ by SIMS, SEM and laser-induced breakdown spectroscopy (LIBS). And deposition behind the lower divertor is in-situ measured by a quartz crystal microbalance (QMB). The deposition in HL-2A displays a complex pattern and clear localization characteristic. The thickness of the deposition layer varies in the range of 0-4μm. And in-situ diagnostic of QMB indicates that the average thickness of the deposition layer per pulse is over ten nanometers. In addition, the results imply that Si, Fe and D have different behaviors during the material deposition in HL-2A.

  8. Retracted: Association of ACE I/D gene polymorphism with T2DN susceptibility and the risk of T2DM developing into T2DN in a Caucasian population.

    PubMed

    Liu, Guohui; Zhou, Tian-Biao; Jiang, Zongpei; Zheng, Dongwen

    2015-03-01

    The association of the angiotensin-converting enzyme (ACE) insertion/deletion (I/D) gene polymorphism with type-2 diabetic nephropathy (T2DN) susceptibility and the risk of type-2 diabetes mellitus (T2DM) developing into T2DN in Caucasian populations is still controversial. A meta-analysis was performed to evaluate the association of ACE I/D gene polymorphism with T2DN susceptibility and the risk of T2DM developing into T2DN in Caucasian populations. A predefined literature search and selection of eligible relevant studies were performed to collect data from electronic databases. Sixteen articles were identified for the analysis of the association of ACE I/D gene polymorphism with T2DN susceptibility and the risk of T2DM developing into T2DN in Caucasian populations. ACE I/D gene polymorphism was not associated with T2DN susceptibility and the risk of patients with T2DM developing T2DN in Caucasian populations. Sensitivity analysis according to sample size of case (<100 vs. ≥100) was also performed, and the results were similar to the non-sensitivity analysis. ACE I/D gene polymorphism was not associated with T2DN susceptibility and the risk of patients with T2DM developing T2DN in Caucasian populations. However, more studies should be performed in the future. © The Author(s) 2014.

  9. Fucoxanthin exerts differing effects on 3T3-L1 cells according to differentiation stage and inhibits glucose uptake in mature adipocytes

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

    Kang, Seong-Il; Ko, Hee-Chul; Shin, Hye-Sun

    2011-06-17

    Highlights: {yields} Fucoxanthin enhances 3T3-L1 adipocyte differentiation at an early stage. {yields} Fucoxanthin inhibits 3T3-L1 adipocyte differentiation at intermediate and late stages. {yields} Fucoxanthin attenuates glucose uptake by inhibiting the phosphorylation of IRS in mature 3T3-L1 adipocytes. {yields} Fucoxanthin exerts its anti-obesity effect by inhibiting the differentiation of adipocytes at both intermediate and late stages, as well as glucose uptake in mature adipocytes. -- Abstract: Progression of 3T3-L1 preadipocyte differentiation is divided into early (days 0-2, D0-D2), intermediate (days 2-4, D2-D4), and late stages (day 4 onwards, D4-). In this study, we investigated the effects of fucoxanthin, isolated from themore » edible brown seaweed Petalonia binghamiae, on adipogenesis during the three differentiation stages of 3T3-L1 preadipocytes. When fucoxanthin was applied during the early stage of differentiation (D0-D2), it promoted 3T3-L1 adipocyte differentiation, as evidenced by increased triglyceride accumulation. At the molecular level, fucoxanthin increased protein expression of peroxisome proliferator-activated receptor {gamma} (PPAR{gamma}), CCAAT/enhancer-binding protein {alpha} (C/EBP{alpha}), sterol regulatory element-binding protein 1c (SREBP1c), and aP2, and adiponectin mRNA expression, in a dose-dependent manner. However, it reduced the expression of PPAR{gamma}, C/EBP{alpha}, and SREBP1c during the intermediate (D2-D4) and late stages (D4-D7) of differentiation. It also inhibited the uptake of glucose in mature 3T3-L1 adipocytes by reducing the phosphorylation of insulin receptor substrate 1 (IRS-1). These results suggest that fucoxanthin exerts differing effects on 3T3-L1 cells of different differentiation stages and inhibits glucose uptake in mature adipocytes.« less

  10. Design of set-point weighting PIλ + Dμ controller for vertical magnetic flux controller in Damavand tokamak.

    PubMed

    Rasouli, H; Fatehi, A

    2014-12-01

    In this paper, a simple method is presented for tuning weighted PI(λ) + D(μ) controller parameters based on the pole placement controller of pseudo-second-order fractional systems. One of the advantages of this controller is capability of reducing the disturbance effects and improving response to input, simultaneously. In the following sections, the performance of this controller is evaluated experimentally to control the vertical magnetic flux in Damavand tokamak. For this work, at first a fractional order model is identified using output-error technique in time domain. For various practical experiments, having desired time responses for magnetic flux in Damavand tokamak, is vital. To approach this, at first the desired closed loop reference models are obtained based on generalized characteristic ratio assignment method in fractional order systems. After that, for the identified model, a set-point weighting PI(λ) + D(μ) controller is designed and simulated. Finally, this controller is implemented on digital signal processor control system of the plant to fast/slow control of magnetic flux. The practical results show appropriate performance of this controller.

  11. Multi-frequency ICRF diagnostic of Tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Lafonteese, David James

    This thesis explores the diagnostic possibilities of a fast wave-based method for measuring the ion density and temperature profiles of tokamak plasmas. In these studies fast waves are coupled to the plasma at frequencies at the second harmonic of the ion gyrofrequency, at which wave energy is absorbed by the finite-temperature ions. As the ion gyrofrequency is dependent upon the local magnetic field, which varies as l/R in a tokamak, this power absorption is radially localized. The simultaneous launching of multiple frequencies, all resonating at different plasma positions, allows local measurements of the ion density and temperature. To investigate the profile applications of wave damping measurements in a simulated tokamak, an inhouse slab-model ICRF code is developed. A variety of analysis methods are presented, and ion density and temperature profiles are reconstructed for hydrogen plasmas for the Electric Tokamak (ET) and ITER parameter spaces. These methods achieve promising results in simulated plasmas featuring bulk ion heating, off-axis RF heating, and density ramps. The experimental results of similar studies on the Electric Tokamak, a high aspect ratio (R/a = 5), low toroidal field (2.2 kG) device are then presented. In these studies, six fast wave frequencies were coupled using a single-strap, low-field-side antenna to ET plasmas. The frequencies were variable, and could be tuned to resonate at different radii for different experiments. Four magnetic pickup loops were used to measure of the toroidal component of the wave magnetic field. The expected greater eigenmode damping of center-resonant frequencies versus edge-resonant frequencies is consistently observed. Comparison of measured aspects of fast wave behavior in ET is made with the slab code predictions, which validate the code simulations under weakly-damped conditions. A density profile is measured for an ET discharge through analysis of the fast wave measurements, and is compared to an

  12. Millimeter-wave imaging diagnostics systems on the EAST tokamak (invited)

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

    Zhu, Y. L.; Xie, J. L., E-mail: jlxie@ustc.edu.cn; Yu, C. X.

    2016-11-15

    Millimeter-wave imaging diagnostics, with large poloidal span and wide radial range, have been developed on the EAST tokamak for visualization of 2D electron temperature and density fluctuations. A 384 channel (24 poloidal × 16 radial) Electron Cyclotron Emission Imaging (ECEI) system in F-band (90-140 GHz) was installed on the EAST tokamak in 2012 to provide 2D electron temperature fluctuation images with high spatial and temporal resolution. A co-located Microwave Imaging Reflectometry (MIR) will be installed for imaging of density fluctuations by December 2016. This “4th generation” MIR system has eight independent frequency illumination beams in W-band (75-110 GHz) driven bymore » fast tuning synthesizers and active multipliers. Both of these advanced millimeter-wave imaging diagnostic systems have applied the latest techniques. A novel design philosophy “general optics structure” has been employed for the design of the ECEI and MIR receiver optics with large aperture. The extended radial and poloidal coverage of ECEI on EAST is made possible by innovations in the design of front-end optics. The front-end optical structures of the two imaging diagnostics, ECEI and MIR, have been integrated into a compact system, including the ECEI receiver and MIR transmitter and receiver. Two imaging systems share the same mid-plane port for simultaneous, co-located 2D fluctuation measurements of electron density and temperature. An intelligent remote-control is utilized in the MIR electronics systems to maintain focusing at the desired radial region even with density variations by remotely tuning the probe frequencies in about 200 μs. A similar intelligent technique has also been applied on the ECEI IF system, with remote configuration of the attenuations for each channel.« less

  13. Millimeter-wave imaging diagnostics systems on the EAST tokamak (invited)

    NASA Astrophysics Data System (ADS)

    Zhu, Y. L.; Xie, J. L.; Yu, C. X.; Zhao, Z. L.; Gao, B. X.; Chen, D. X.; Liu, W. D.; Liao, W.; Qu, C. M.; Luo, C.; Hu, X.; Spear, A. G.; Luhmann, N. C.; Domier, C. W.; Chen, M.; Ren, X.; Tobias, B. J.

    2016-11-01

    Millimeter-wave imaging diagnostics, with large poloidal span and wide radial range, have been developed on the EAST tokamak for visualization of 2D electron temperature and density fluctuations. A 384 channel (24 poloidal × 16 radial) Electron Cyclotron Emission Imaging (ECEI) system in F-band (90-140 GHz) was installed on the EAST tokamak in 2012 to provide 2D electron temperature fluctuation images with high spatial and temporal resolution. A co-located Microwave Imaging Reflectometry (MIR) will be installed for imaging of density fluctuations by December 2016. This "4th generation" MIR system has eight independent frequency illumination beams in W-band (75-110 GHz) driven by fast tuning synthesizers and active multipliers. Both of these advanced millimeter-wave imaging diagnostic systems have applied the latest techniques. A novel design philosophy "general optics structure" has been employed for the design of the ECEI and MIR receiver optics with large aperture. The extended radial and poloidal coverage of ECEI on EAST is made possible by innovations in the design of front-end optics. The front-end optical structures of the two imaging diagnostics, ECEI and MIR, have been integrated into a compact system, including the ECEI receiver and MIR transmitter and receiver. Two imaging systems share the same mid-plane port for simultaneous, co-located 2D fluctuation measurements of electron density and temperature. An intelligent remote-control is utilized in the MIR electronics systems to maintain focusing at the desired radial region even with density variations by remotely tuning the probe frequencies in about 200 μs. A similar intelligent technique has also been applied on the ECEI IF system, with remote configuration of the attenuations for each channel.

  14. Be ITER-like wall at the JET tokamak under plasma

    NASA Astrophysics Data System (ADS)

    Tsavalas, P.; Lagoyannis, A.; Mergia, K.; Rubel, M.; Triantou, K.; Harissopulos, S.; Kokkoris, M.; Petersson, P.; Contributors, JET

    2017-12-01

    The JET tokamak is operated with beryllium and tungsten plasma-facing components to prepare for the exploitation of ITER. To determine beryllium erosion and migration in JET a set of markers were installed. Specimens from different beryllium marker tiles of the main wall of the ITER-like wall (ILW) JET tokamak from the first and the second D-D campaign were analyzed with nuclear reaction analysis, x-ray fluorescence spectroscopy, scanning electron microscopy and x-ray diffraction (XRD). Emphasis was on the determination of carbon plasma impurities deposited on beryllium surfaces. The 12C(d, p0)13C reaction was used to quantify carbon deposition and to determine depth profiles. Carbon quantities on the surface of the Be tiles are low, varying from (0.35 ± 0.07) × 1017 to (11.8 ± 0.6) × 1017 at cm-2 in the deposition depth from 0.4 to 6.7 μm, respectively. In the 0.4-0.5 mm wide grooves of castellation sides the carbon content is found up to (14.3 ± 2.5) × 1017 at cm-2 while it is higher (up to (38 ± 4) × 1017 at cm-2) in wider gaps (0.8 mm) separating tile segments. Oxygen (O), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni) and tungsten (W) were detected in all samples exposed to plasma and the reference one but at lower quantities at the latter. In the central part of the Inner Wall Guard Limiter from the first ILW campaign and in the Outer Poloidal Limiter from the second ILW campaign the Ni interlayer has been completely eroded. XRD shows the formation of BeNi in most specimens.

  15. Slope Controls Grain Yield and Climatic Yield in Mountainous Yunnan province, China

    NASA Astrophysics Data System (ADS)

    Duan, X.; Rong, L.; Gu, Z.; Feng, D.

    2017-12-01

    Mountainous regions are increasingly vulnerable to food insecurity because of limited arable land, growing population pressure, and climate change. Development of sustainable mountain agriculture will require an increased understanding of the effects of environmental factors on grain and climatic yields. The objective of this study was to explore the relationships between actual grain yield, climatic yield, and environmental factors in a mountainous region in China. We collected data on the average grain yield per unit area in 119 counties in Yunnan province from 1985 to 2012, and chose 17 environmental factors for the same period. Our results showed that actual grain yield ranged from 1.43 to 6.92 t·ha-1, and the climatic yield ranged from -0.15 to -0.01 t·ha-1. Lower climatic yield but higher grain yield was generally found in central areas and at lower slopes and elevations in the western and southwestern counties of Yunnan province. Higher climatic yield but lower grain yield were found in northwestern parts of Yunnan province on steep slopes. Annual precipation and temperature had a weak influence on the climatic yield. Slope explained 44.62 and 26.29% of the variation in grain yield and climatic yield. The effects of topography on grain and climatic yields were greater than climatic factors. Slope was the most important environmental variable for the variability in climatic and grain yields in the mountainous Yunnan province due to the highly heterogeneous topographic conditions. Conversion of slopes to terraces in areas with higher climatic yields is an effective way to maintain grain production in response to climate variability. Additionally, soil amendments and soil and water conservation measures should be considered to maintain soil fertility and aid in sustainable development in central areas, and in counties at lower slopes and elevations in western and southwestern Yunnan province.

  16. Scalar resonances in a unitary {pi}{pi} S-wave model for D{sup +}{yields}{pi}{sup +}{pi}{sup -}{pi}{sup +}

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

    Boito, D. R.; Instituto de Fisica, Universidade de Sao Paulo, C.P. 66318, 05315-970, Sao Paulo, SP; Dedonder, J.-P.

    We propose a model for D{sup +}{yields}{pi}{sup +}{pi}{sup -}{pi}{sup +} decays following experimental results which indicate that the two-pion interaction in the S wave is dominated by the scalar resonances f{sub 0}(600)/{sigma} and f{sub 0}(980). The weak decay amplitude for D{sup +}{yields}R{pi}{sup +}, where R is a resonance that subsequently decays into {pi}{sup +}{pi}{sup -}, is constructed in a factorization approach. In the S wave, we implement the strong decay R{yields}{pi}{sup +}{pi}{sup -} by means of a scalar form factor. This provides a unitary description of the pion-pion interaction in the entire kinematically allowed mass range m{sub {pi}}{sub {pi}}{sup 2}more » from threshold to about 3 GeV{sup 2}. In order to reproduce the experimental Dalitz plot for D{sup +}{yields}{pi}{sup +}{pi}{sup -}{pi}{sup +}, we include contributions beyond the S wave. For the P wave, dominated by the {rho}(770){sup 0}, we use a Breit-Wigner description. Higher waves are accounted for by using the usual isobar prescription for the f{sub 2}(1270) and {rho}(1450){sup 0}. The major achievement is a good reproduction of the experimental m{sub {pi}}{sub {pi}}{sup 2} distribution, and of the partial as well as the total D{sup +}{yields}{pi}{sup +}{pi}{sup -}{pi}{sup +} branching ratios. Our values are generally smaller than the experimental ones. We discuss this shortcoming and, as a by-product, we predict a value for the poorly known D{yields}{sigma} transition form factor at q{sup 2}=m{sub {pi}}{sup 2}.« less

  17. Structure of Escherichia coli Arginyl-tRNA Synthetase in Complex with tRNAArg: Pivotal Role of the D-loop.

    PubMed

    Stephen, Preyesh; Ye, Sheng; Zhou, Ming; Song, Jian; Zhang, Rongguang; Wang, En-Duo; Giegé, Richard; Lin, Sheng-Xiang

    2018-05-25

    Aminoacyl-tRNA synthetases are essential components in protein biosynthesis. Arginyl-tRNA synthetase (ArgRS) belongs to the small group of aminoacyl-tRNA synthetases requiring cognate tRNA for amino acid activation. The crystal structure of Escherichia coli (Eco) ArgRS has been solved in complex with tRNA Arg at 3.0-Å resolution. With this first bacterial tRNA complex, we are attempting to bridge the gap existing in structure-function understanding in prokaryotic tRNA Arg recognition. The structure shows a tight binding of tRNA on the synthetase through the identity determinant A20 from the D-loop, a tRNA recognition snapshot never elucidated structurally. This interaction of A20 involves 5 amino acids from the synthetase. Additional contacts via U20a and U16 from the D-loop reinforce the interaction. The importance of D-loop recognition in EcoArgRS functioning is supported by a mutagenesis analysis of critical amino acids that anchor tRNA Arg on the synthetase; in particular, mutations at amino acids interacting with A20 affect binding affinity to the tRNA and specificity of arginylation. Altogether the structural and functional data indicate that the unprecedented ArgRS crystal structure represents a snapshot during functioning and suggest that the recognition of the D-loop by ArgRS is an important trigger that anchors tRNA Arg on the synthetase. In this process, A20 plays a major role, together with prominent conformational changes in several ArgRS domains that may eventually lead to the mature ArgRS:tRNA complex and the arginine activation. Functional implications that could be idiosyncratic to the arginine identity of bacterial ArgRSs are discussed. Copyright © 2018 Elsevier Ltd. All rights reserved.

  18. Structured Cable for High-Current Coils of Tokamaks

    NASA Astrophysics Data System (ADS)

    Benson, Christopher; McIntyre, Peter; Sattarov, Akhdiyor; Mann, Thomas

    2011-10-01

    The 45 kA superconducting cable for the ITER central solenoid coil has yielded questionable results in two recent tests. In both cases the cable Tc increased after cycling only a fraction of the design life, indicating degradation due to fatigue and fracture among the superconducting strands. The Accelerator Research Lab at Texas A&M University is developing a design for a Nb3Sn structured cable suitable for such tokamak coils. The superconductor is configured in 6 sub-cables, and each subcable is supported within a channel of a central support structure within a high-strength armor sheath. The structured cable addresses two issues that are thought to compromise opposition at high current. The strands are supported without cross-overs (which produce stress concentration); and armor sheath and core structure bypass stress through the coil and among subcables so that the stress within each subcable is only what is produced directly upon it. Details of the design and plans for development will be presented.

  19. Continuum kinetic modeling of the tokamak plasma edge

    DOE PAGES

    Dorf, M. A.; Dorr, M.; Rognlien, T.; ...

    2016-03-10

    In this study, the first 4D (axisymmetric) high-order continuum gyrokinetic transport simulations that span the magnetic separatrix of a tokamak are presented. The modeling is performed with the COGENT code, which is distinguished by fourth-order finite-volume discretization combined with mapped multiblock grid technology to handle the strong anisotropy of plasmatransport and the complex X-point divertor geometry with high accuracy. The calculations take into account the effects of fully nonlinear Fokker-Plank collisions, electrostatic potential variations, and anomalous radial transport. Topics discussed include: (a) ion orbit loss and the associated toroidal rotation and (b) edge plasma relaxation in the presence of anomalousmore » radial transport.« less

  20. Tomographic reconstruction of tokamak plasma light emission from single image using wavelet-vaguelette decomposition

    NASA Astrophysics Data System (ADS)

    Nguyen van yen, R.; Fedorczak, N.; Brochard, F.; Bonhomme, G.; Schneider, K.; Farge, M.; Monier-Garbet, P.

    2012-01-01

    Images acquired by cameras installed in tokamaks are difficult to interpret because the three-dimensional structure of the plasma is flattened in a non-trivial way. Nevertheless, taking advantage of the slow variation of the fluctuations along magnetic field lines, the optical transformation may be approximated by a generalized Abel transform, for which we propose an inversion technique based on the wavelet-vaguelette decomposition. After validation of the new method using an academic test case and numerical data obtained with the Tokam 2D code, we present an application to an experimental movie obtained in the tokamak Tore Supra. A comparison with a classical regularization technique for ill-posed inverse problems, the singular value decomposition, allows us to assess the efficiency. The superiority of the wavelet-vaguelette technique is reflected in preserving local features, such as blobs and fronts, in the denoised emissivity map.

  1. Burn Control Mechanisms in Tokamaks

    NASA Astrophysics Data System (ADS)

    Hill, M. A.; Stacey, W. M.

    2015-11-01

    Burn control and passive safety in accident scenarios will be an important design consideration in future tokamak reactors, in particular fusion-fission hybrid reactors, e.g. the Subcritical Advanced Burner Reactor. We are developing a burning plasma dynamics code to explore various aspects of burn control, with the intent to identify feedback mechanisms that would prevent power excursions. This code solves the coupled set of global density and temperature equations, using scaling relations from experimental fits. Predictions of densities and temperatures have been benchmarked against DIII-D data. We are examining several potential feedback mechanisms to limit power excursions: i) ion-orbit loss, ii) thermal instability density limits, iii) MHD instability limits, iv) the degradation of alpha-particle confinement, v) modifications to the radial current profile, vi) ``divertor choking'' and vii) Type 1 ELMs. Work supported by the US DOE under DE-FG02-00ER54538, DE-FC02-04ER54698.

  2. Protection of tokamak plasma facing components by a capillary porous system with lithium

    NASA Astrophysics Data System (ADS)

    Lyublinski, I.; Vertkov, A.; Mirnov, S.; Lazarev, V.

    2015-08-01

    Development of plasma facing material (PFM) based on the Capillary-Porous System (CPS) with lithium and activity on realization of lithium application strategy are addressed to meet the challenges under the creation of steady-state tokamak fusion reactor and fusion neutron source. Presented overview of experimental study of lithium CPS in plasma devices demonstrates the progress in protection of tokamak plasma facing components (PFC) from damage, stabilization and self-renewal of liquid lithium surface, elimination of plasma pollution and lithium accumulation in tokamak chamber. The possibility of PFC protection from the high power load related to cooling of the tokamak boundary plasma by radiation of non-fully stripped lithium ions supported by experimental results. This approach demonstrated in scheme of closed loops of Li circulation in the tokamak vacuum chamber and realized in a series of design of tokamak in-vessel elements.

  3. The study of heat flux for disruption on experimental advanced superconducting tokamak

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

    Yang, Zhendong, E-mail: dongyz@ipp.ac.cn, E-mail: jafang@dhu.edu.cn; Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031; Fang, Jianan, E-mail: dongyz@ipp.ac.cn, E-mail: jafang@dhu.edu.cn

    Disruption of the plasma is one of the most dangerous instabilities in tokamak. During the disruption, most of the plasma thermal energy is lost, which causes damages to the plasma facing components. Infrared (IR) camera is an effective tool to detect the temperature distribution on the first wall, and the energy deposited on the first wall can be calculated from the surface temperature profile measured by the IR camera. This paper concentrates on the characteristics of heat flux distribution onto the first wall under different disruptions, including the minor disruption and the vertical displacement events (VDE) disruption. Several minor disruptionsmore » have been observed before the major disruption under the high plasma density in experimental advanced superconducting tokamak. During the minor disruption, the heat fluxes are mainly deposited on the upper/lower divertors. The magnetic configuration prior to the minor disruption is a lower single null with the radial distance between the two separatrices in the outer midplane dR{sub sep} = −2 cm, while it changes to upper single null (dR{sub sep} = 1.4 cm) during the minor disruption. As for the VDE disruption, the spatial distribution of heat flux exhibits strong toroidal and radial nonuniformity, and the maximum heat flux received on the dome plate can be up to 11 MW/m{sup 2}.« less

  4. High Performance Programming Using Explicit Shared Memory Model on the Cray T3D

    NASA Technical Reports Server (NTRS)

    Saini, Subhash; Simon, Horst D.; Lasinski, T. A. (Technical Monitor)

    1994-01-01

    The Cray T3D is the first-phase system in Cray Research Inc.'s (CRI) three-phase massively parallel processing program. In this report we describe the architecture of the T3D, as well as the CRAFT (Cray Research Adaptive Fortran) programming model, and contrast it with PVM, which is also supported on the T3D We present some performance data based on the NAS Parallel Benchmarks to illustrate both architectural and software features of the T3D.

  5. Measurement of |V{sub cb}| using {bar B}{sup 0} {yields} D*{sup +}{ell}{sup -}{bar {nu}}{sub {ell}} Decays

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

    Della Ricca, Giuseppe

    A preliminary measurement of |V{sub cb}| and the branching fraction {Beta}({bar B}{sup 0} {yields} D*{sup +}{ell}{sup -}{bar {nu}}{sub {ell}}) has been performed based on a sample of about 55,700 {bar B}{sup 0} {yields} D*{sup +}{ell}{sup -}{bar {nu}}{sub {ell}} decays recorded with the BABAR detector. The decays are identified in the D*{sup +} {yields} D{sup 0}{pi}{sup +} final state, with the D{sup 0} reconstructed in three different decay modes. The differential decay rate is measured as a function of the relativistic boost of the D*{sup +} in the {bar B}{sup 0} rest frame. The value of the differential decay rate atmore » ''zero recoil'', namely the point at which the D*{sup +} is at rest in the {bar B}{sup 0} frame, is predicted in Heavy Quark Effective Theory as a kinematic factor times F(1)|V{sub cb}|, where F is the unique form factor governing the decay. We extrapolate the measured differential decay rate to the zero recoil point and obtain F(1)|V{sub cb}| = (34.03 {+-} 0.24 {+-} 1.31) x 10{sup -3}. Using a theoretical calculation for F(1) we extract |V{sub cb}| = (37.27 {+-} 0.26(stat.) {+-} 1.43(syst.){sub -1.2}{sup +1.5}(theo.)) x 10{sup -3}. From the integrated decay rate we obtain {Beta}({bar B}{sup 0} {yields} D*{sup +}{ell}{sup -}{bar {nu}}{sub {ell}}) = (4.68 {+-} 0.03 {+-} 0.29)%.« less

  6. Selective destruction of mouse islet beta cells by human T lymphocytes in a newly-established humanized type 1 diabetic model

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

    Zhao, Yong, E-mail: yongzhao@uic.edu; Guo, Chengshan; Hwang, David

    2010-09-03

    Research highlights: {yields} Establish a human immune-mediated type 1 diabetic model in NOD-scid IL2r{gamma}{sup null} mice. {yields} Using the irradiated diabetic NOD mouse spleen mononuclear cells as trigger. {yields} The islet {beta} cells were selectively destroyed by infiltrated human T cells. {yields} The model can facilitate translational research to find a cure for type 1 diabetes. -- Abstract: Type 1 diabetes (T1D) is caused by a T cell-mediated autoimmune response that leads to the loss of insulin-producing {beta} cells. The optimal preclinical testing of promising therapies would be aided by a humanized immune-mediated T1D model. We develop this model inmore » NOD-scid IL2r{gamma}{sup null} mice. The selective destruction of pancreatic islet {beta} cells was mediated by human T lymphocytes after an initial trigger was supplied by the injection of irradiated spleen mononuclear cells (SMC) from diabetic nonobese diabetic (NOD) mice. This resulted in severe insulitis, a marked loss of total {beta}-cell mass, and other related phenotypes of T1D. The migration of human T cells to pancreatic islets was controlled by the {beta} cell-produced highly conserved chemokine stromal cell-derived factor 1 (SDF-1) and its receptor C-X-C chemokine receptor (CXCR) 4, as demonstrated by in vivo blocking experiments using antibody to CXCR4. The specificity of humanized T cell-mediated immune responses against islet {beta} cells was generated by the local inflammatory microenvironment in pancreatic islets including human CD4{sup +} T cell infiltration and clonal expansion, and the mouse islet {beta}-cell-derived CD1d-mediated human iNKT activation. The selective destruction of mouse islet {beta} cells by a human T cell-mediated immune response in this humanized T1D model can mimic those observed in T1D patients. This model can provide a valuable tool for translational research into T1D.« less

  7. 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

  8. Experimental study of fusion neutron and proton yields produced by petawatt-laser-irradiated D₂-³He or CD₄-³He clustering gases.

    PubMed

    Bang, W; Barbui, M; Bonasera, A; Quevedo, H J; Dyer, G; Bernstein, A C; Hagel, K; Schmidt, K; Gaul, E; Donovan, M E; Consoli, F; De Angelis, R; Andreoli, P; Barbarino, M; Kimura, S; Mazzocco, M; Natowitz, J B; Ditmire, T

    2013-09-01

    We report on experiments in which the Texas Petawatt laser irradiated a mixture of deuterium or deuterated methane clusters and helium-3 gas, generating three types of nuclear fusion reactions: D(d,^{3}He)n, D(d,t)p, and ^{3}He(d,p)^{4}He. We measured the yields of fusion neutrons and protons from these reactions and found them to agree with yields based on a simple cylindrical plasma model using known cross sections and measured plasma parameters. Within our measurement errors, the fusion products were isotropically distributed. Plasma temperatures, important for the cross sections, were determined by two independent methods: (1) deuterium ion time of flight and (2) utilizing the ratio of neutron yield to proton yield from D(d,^{3}He)n and ^{3}He(d,p)^{4}He reactions, respectively. This experiment produced the highest ion temperature ever achieved with laser-irradiated deuterium clusters.

  9. High β produced by neutral beam injection in the START (Small Tight Aspect Ratio Tokamak) spherical tokamak

    NASA Astrophysics Data System (ADS)

    Sykes, Alan

    1997-05-01

    The world's first high-power auxiliary heating experiments in a tight aspect ratio (or spherical) tokamak have been performed on the Small Tight Aspect Ratio Tokomak (START) device [Sykes et al., Nucl. Fusion 32, 694 (1992)] at Culham Laboratory, using the 40 keV, 0.5 MW Neutral Beam Injector loaned by the Oak Ridge National Laboratory. Injection has been mainly of hydrogen into hydrogen or deuterium target plasmas, with a one-day campaign to explore D→D operation. In each case injection provides a combination of higher density operation and effective heating of both ions and electrons. The highest β values achieved to date in START are volume average βT˜11.5% and central beta βO˜50%. Already high, these values are expected to increase further with the use of higher beam power.

  10. Vibrational and electronic circular dichroism study of the interactions of cationic porphyrins with (dG-dC)10 and (dA-dT)10.

    PubMed

    Nový, Jakub; Urbanová, Marie

    2007-03-01

    The interactions of two different porphyrins, without axial ligands-5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin-Cu(II) tetrachloride (Cu(II)TMPyP) and with bulky meso substituents-5,10,15,20-tetrakis(N,N,N-trimethylanilinium-4-yl)porphyrin tetrachloride (TMAP), with (dG-dC)10 and (dA-dT)10 were studied by combination of vibrational circular dichroism (VCD) and electronic circular dichroism (ECD) spectroscopy at different [oligonucleotide]/[porphyrin] ratios, where [oligonucleotide] and [porphyrin] are the concentrations of oligonucleotide per base-pair and porphyrin, respectively. The combination of VCD and ECD spectroscopy enables us to identify the types of interactions, and to specify the sites of interactions: The intercalative binding mode of Cu(II)TMPyP with (dG-dC)(10), which has been well described, was characterized by a new VCD "marker" and it was shown that the interaction of Cu(II)TMPyP with (dA-dT)10 via external binding to the phosphate backbone and major groove binding caused transition from the B to the non-B conformer. TMAP interacted with the major groove of (dG-dC)10, was semi-intercalated into (dA-dT)10, and caused significant variation in the structure of both oligonucleotides at the higher concentration of porphyrin. The spectroscopic techniques used in this study revealed that porphyrin binding with AT sequences caused substantial variation of the DNA structure. It was shown that VCD spectroscopy is an effective tool for the conformational studies of nucleic acid-porphyrin complexes in solution. (c) 2007 Wiley Periodicals, Inc.

  11. Improved l1-SPIRiT using 3D walsh transform-based sparsity basis.

    PubMed

    Feng, Zhen; Liu, Feng; Jiang, Mingfeng; Crozier, Stuart; Guo, He; Wang, Yuxin

    2014-09-01

    l1-SPIRiT is a fast magnetic resonance imaging (MRI) method which combines parallel imaging (PI) with compressed sensing (CS) by performing a joint l1-norm and l2-norm optimization procedure. The original l1-SPIRiT method uses two-dimensional (2D) Wavelet transform to exploit the intra-coil data redundancies and a joint sparsity model to exploit the inter-coil data redundancies. In this work, we propose to stack all the coil images into a three-dimensional (3D) matrix, and then a novel 3D Walsh transform-based sparsity basis is applied to simultaneously reduce the intra-coil and inter-coil data redundancies. Both the 2D Wavelet transform-based and the proposed 3D Walsh transform-based sparsity bases were investigated in the l1-SPIRiT method. The experimental results show that the proposed 3D Walsh transform-based l1-SPIRiT method outperformed the original l1-SPIRiT in terms of image quality and computational efficiency. Copyright © 2014 Elsevier Inc. All rights reserved.

  12. Characterization of D-maltose as a T2 -exchange contrast agent for dynamic contrast-enhanced MRI.

    PubMed

    Goldenberg, Joshua M; Pagel, Mark D; Cárdenas-Rodríguez, Julio

    2018-09-01

    We sought to investigate the potential of D-maltose, D-sorbitol, and D-mannitol as T 2 exchange magnetic resonance imaging (MRI) contrast agents. We also sought to compare the in vivo pharmacokinetics of D-maltose with D-glucose with dynamic contrast enhancement (DCE) MRI. T 1 and T 2 relaxation time constants of the saccharides were measured using eight pH values and nine concentrations. The effect of echo spacing in a multiecho acquisition sequence used for the T 2 measurement was evaluated for all samples. Finally, performances of D-maltose and D-glucose during T 2 -weighted DCE-MRI were compared in vivo. Estimated T 2 relaxivities (r 2 ) of D-glucose and D-maltose were highly and nonlinearly dependent on pH and echo spacing, reaching their maximum at pH = 7.0 (∼0.08 mM -1 s -1 ). The r 2 values of D-sorbitol and D-mannitol were estimated to be ∼0.02 mM -1 s -1 and were invariant to pH and echo spacing for pH ≤7.0. The change in T 2 in tumor and muscle tissues remained constant after administration of D-maltose, whereas the change in T 2 decreased in tumor and muscle after administration of D-glucose. Therefore, D-maltose has a longer time window for T 2 -weighted DCE-MRI in tumors. We have demonstrated that D-maltose can be used as a T 2 exchange MRI contrast agent. The larger, sustained T 2 -weighted contrast from D-maltose relative to D-glucose has practical advantages for tumor diagnoses during T 2 -weighted DCE-MRI. Magn Reson Med 80:1158-1164, 2018. © 2018 International Society for Magnetic Resonance in Medicine. © 2018 International Society for Magnetic Resonance in Medicine.

  13. Sub-Alfvénic reduced magnetohydrodynamic equations for tokamaks

    NASA Astrophysics Data System (ADS)

    Sengupta, W.; Hassam, A. B.; Antonsen, T. M.

    2017-06-01

    A reduced set of magnetohydrodynamic (MHD) equations is derived, applicable to large aspect ratio tokamaks and relevant for dynamics that is sub-Alfvénic with respect to ideal ballooning modes. This ordering optimally allows sound waves, Mercier modes, drift modes, geodesic-acoustic modes (GAM), zonal flows and shear Alfvén waves. Wavelengths long compared to the gyroradius but comparable to the minor radius of a typical tokamak are considered. With the inclusion of resistivity, tearing modes, resistive ballooning modes, Pfirsch-Schluter cells and the Stringer spin-up are also included. A major advantage is that the resulting system is two-dimensional in space, and the system incorporates self-consistent and dynamic Shafranov shifts. A limitation is that the system is valid only in radial domains where the tokamak safety factor, , is close to rational. In the tokamak core, the system is well suited to study the sawtooth discharge in the presence of Mercier modes. The systematic ordering scheme and methodology developed are versatile enough to reduce the more general collisional two-fluid equations or possibly the Vlasov-Maxwell system in the MHD ordering.

  14. Formation and stability of impurity "snakes" in tokamak plasmas.

    PubMed

    Delgado-Aparicio, L; Sugiyama, L; Granetz, R; Gates, D A; Rice, J E; Reinke, M L; Bitter, M; Fredrickson, E; Gao, C; Greenwald, M; Hill, K; Hubbard, A; Hughes, J W; Marmar, E; Pablant, N; Podpaly, Y; Scott, S; Wilson, R; Wolfe, S; Wukitch, S

    2013-02-08

    New observations of the formation and dynamics of long-lived impurity-induced helical "snake" modes in tokamak plasmas have recently been carried out on Alcator C-Mod. The snakes form as an asymmetry in the impurity ion density that undergoes a seamless transition from a small helically displaced density to a large crescent-shaped helical structure inside q<1, with a regularly sawtoothing core. The observations show that the conditions for the formation and persistence of a snake cannot be explained by plasma pressure alone. Instead, many features arise naturally from nonlinear interactions in a 3D MHD model that separately evolves the plasma density and temperature.

  15. Structures of (5′S)-8,5′-Cyclo-2′-deoxyguanosine Mismatched with dA or dT

    PubMed Central

    2012-01-01

    Diastereomeric 8,5′-cyclopurine 2′-deoxynucleosides, containing a covalent bond between the deoxyribose and the purine base, are induced in DNA by ionizing radiation. They are suspected to play a role in the etiology of neurodegeneration in xeroderma pigmentosum patients. If not repaired, the S-8,5′-cyclo-2′-deoxyguanosine lesion (S-cdG) induces Pol V-dependent mutations at a frequency of 34% in Escherichia coli. Most are S-cdG → A transitions, suggesting mis-incorporation of dTTP opposite the lesion during replication bypass, although low levels of S-cdG → T transversions, arising from mis-incorporation of dATP, are also observed. We report the structures of 5′-d(GTGCXTGTTTGT)-3′·5′-d(ACAAACAYGCAC)-3′, where X denotes S-cdG and Y denotes either dA or dT, corresponding to the situation following mis-insertion of either dTTP or dATP opposite the S-cdG lesion. The S-cdG·dT mismatch pair adopts a wobble base pairing. This provides a plausible rationale for the S-cdG → A transitions. The S-cdG·dA mismatch pair differs in conformation from the dG·dA mismatch pair. For the S-cdG·dA mismatch pair, both S-cdG and dA intercalate, but no hydrogen bonding is observed between S-cdG and dA. This is consistent with the lower levels of S-cdG → T transitions in E. coli. PMID:22309170

  16. A symplectic map for trajectories of magnetic field lines in double-null divertor tokamaks

    NASA Astrophysics Data System (ADS)

    Crank, Willie; Ali, Halima; Punjabi, Alkesh

    2009-11-01

    The coordinates of the area-preserving map equations for integration of magnetic field line trajectories in tokamaks can be any coordinates for which a transformation to (ψ,θ,φ) coordinates exists [A. Punjabi, H. Ali, T. Evans, and A. Boozer, Phys. Lett. A 364, 140 (2007)]. ψ is toroidal magnetic flux, θ is poloidal angle, and φ is toroidal angle. This freedom is exploited to construct a map that represents the magnetic topology of double-null divertor tokamaks. For this purpose, the generating function of the simple map [A. Punjabi, A. Verma, and A. Boozer, Phys. Rev. Lett. 69, 3322 (1992)] is slightly modified. The resulting map equations for the double-null divertor tokamaks are: x1=x0-ky0(1-y0^2 ), y1=y0+kx1. k is the map parameter. It represents the generic topological effects of toroidal asymmetries. The O-point is at (0.0). The X-points are at (0,±1). The equilibrium magnetic surfaces are calculated. These surfaces are symmetric about the x- and y- axes. The widths of stochastic layer near the X-points in the principal plane, and the fractal dimensions of the magnetic footprints on the inboard and outboard side of upper and lower X-points are calculated from the map. This work is supported by US Department of Energy grants DE-FG02-07ER54937, DE-FG02-01ER54624 and DE-FG02-04ER54793.

  17. Tokamak magneto-hydrodynamics and reference magnetic coordinates for simulations of plasma disruptions

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

    Zakharov, Leonid E.; Li, Xujing

    This paper formulates the Tokamak Magneto-Hydrodynamics (TMHD), initially outlined by X. Li and L. E. Zakharov [Plasma Science and Technology 17(2), 97–104 (2015)] for proper simulations of macroscopic plasma dynamics. The simplest set of magneto-hydrodynamics equations, sufficient for disruption modeling and extendable to more refined physics, is explained in detail. First, the TMHD introduces to 3-D simulations the Reference Magnetic Coordinates (RMC), which are aligned with the magnetic field in the best possible way. The numerical implementation of RMC is adaptive grids. Being consistent with the high anisotropy of the tokamak plasma, RMC allow simulations at realistic, very high plasmamore » electric conductivity. Second, the TMHD splits the equation of motion into an equilibrium equation and the plasma advancing equation. This resolves the 4 decade old problem of Courant limitations of the time step in existing, plasma inertia driven numerical codes. The splitting allows disruption simulations on a relatively slow time scale in comparison with the fast time of ideal MHD instabilities. A new, efficient numerical scheme is proposed for TMHD.« less

  18. T & D Publications. Vol. 13. No. 6.

    ERIC Educational Resources Information Center

    International Labour Office, Geneva (Switzerland).

    The sixth dispatch of T & D abstracts contains 42 abstracts of international scope which focus on education, training, and work patterns, and on training in rural areas. Brief abstracts are presented under the following headings: conferences and exhibitions, new policies, new institutions, management, research, training standards, agriculture,…

  19. Engineering aspects of the HT-6M Tokamak

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

    Not Available

    1986-05-01

    The HT-6M is a medium-sized tokamak being built in China. The principal aim of the project is to study high-power auxiliary heating (1-MW neutral beam injection, 1-MW ion cyclotron resonance heating, and 100-kW electron cyclotron resonance heating), high-..beta.. experiments, the transport process, and the formation and diffusion process of impurities. The main device parameters are: major plasma radius R = 65 cm, minor plasma radius a = 20 cm, plasma current I/subP/ = 150 kA, discharge time tau = 150 ms, toroidal field B/subT/ = 15 kG. Simplicity of construction, accessibility to the plasma, reliability in operation, and convenience formore » maintenance were particularly emphasized in the design. The important design features of the device and power supply system are described.« less

  20. From pure fusion to fusion-fission Demo tokamaks

    NASA Astrophysics Data System (ADS)

    Mirnov, S. V.

    2013-04-01

    The major requirements for pure fusion tokamak reactors and tokamak-based fusion neutron sources (FNS) are analyzed together with possible paths from the present-day tokamak towards the FNS tokamak. The FNS are of interest for traditional fission reactors as a method of waste management by burning of long-lived transuranic radionuclides (minorities) and fission fuel breeding. The Russian fission community places several hard requirements on the quality of FNS suitable for the first step of the investigation program of minority burning and breeding. They are (a) a steady-state regime of neutron production (more than 80% of the operational time), (b) a neutron power flux density greater than >0.2 MW m-2, (c) a total surface integrated neutron power >10 MW. Among the different FNS projects, based on magnetically confined plasmas, only ‘classical tokamak’ is most likely to fulfill these requirements in the nearest future. Some of the most important improvements of the ‘classical tokamak’ needed for successful realization of the FNS are (1) decrease in Zeff (probably, by making use of lithium as a part of plasma-facing components), (2) He removal and closed loop DT fuel circulation, (3) increase in the energy of stationary injected neutral tritium beams up to 150-170 keV and (4) control of impurity contamination at the plasma center (probably, by local RF heating). These key issues are discussed.

  1. Role of vitamin D in cytotoxic T lymphocyte immunity to pathogens and cancer.

    PubMed

    Sarkar, Surojit; Hewison, Martin; Studzinski, George P; Li, Yan Chun; Kalia, Vandana

    2016-01-01

    The discovery of vitamin D receptor (VDR) expression in immune cells has opened up a new area of research into immunoregulation by vitamin D, a niche that is distinct from its classical role in skeletal health. Today, about three decades since this discovery, numerous cellular and molecular targets of vitamin D in the immune system have been delineated. Moreover, strong clinical associations between vitamin D status and the incidence/severity of many immune-regulated disorders (e.g. infectious diseases, cancers and autoimmunity) have prompted the idea of using vitamin D supplementation to manipulate disease outcome. While much is known about the effects of vitamin D on innate immune responses and helper T (T(H)) cell immunity, there has been relatively limited progress on the frontier of cytotoxic T lymphocyte (CTL) immunity--an arm of host cellular adaptive immunity that is crucial for the control of such intracellular pathogens as human immunodeficiency virus (HIV), tuberculosis (TB), malaria, and hepatitis C virus (HCV). In this review, we discuss the strong historical and clinical link between vitamin D and infectious diseases that involves cytotoxic T lymphocyte (CTL) immunity, present our current understanding as well as critical knowledge gaps in the realm of vitamin D regulation of host CTL responses, and highlight potential regulatory connections between vitamin D and effector and memory CD8 T cell differentiation events during infections.

  2. The symmetric quartic map for trajectories of magnetic field lines in elongated divertor tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Jones, Morgin; Wadi, Hasina; Ali, Halima; Punjabi, Alkesh

    2009-04-01

    The coordinates of the area-preserving map equations for integration of magnetic field line trajectories in divertor tokamaks can be any coordinates for which a transformation to (ψt,θ,φ) coordinates exists [A. Punjabi, H. Ali, T. Evans, and A. Boozer, Phys. Lett. A 364, 140 (2007)]. ψt is toroidal magnetic flux, θ is poloidal angle, and φ is toroidal angle. This freedom is exploited to construct the symmetric quartic map such that the only parameter that determines magnetic geometry is the elongation of the separatrix surface. The poloidal flux inside the separatrix, the safety factor as a function of normalized minor radius, and the magnetic perturbation from the symplectic discretization are all held constant, and only the elongation is κ varied. The width of stochastic layer, the area, and the fractal dimension of the magnetic footprint and the average radial diffusion coefficient of magnetic field lines from the stochastic layer; and how these quantities scale with κ is calculated. The symmetric quartic map gives the correct scalings which are consistent with the scalings of coordinates with κ. The effects of m =1, n =±1 internal perturbation with the amplitude that is expected to occur in tokamaks are calculated by adding a term [H. Ali, A. Punjabi, A. H. Boozer, and T. Evans, Phys. Plasmas 11, 1908 (2004)] to the symmetric quartic map. In this case, the width of stochastic layer scales as 0.35 power of κ. The area of the footprint is roughly constant. The average radial diffusion coefficient of field lines near the X-point scales linearly with κ. The low mn perturbation changes the quasisymmetric structure of the footprint, and reorganizes it into a single, large scale, asymmetric structure. The symmetric quartic map is combined with the dipole map [A. Punjabi, H. Ali, and A. H. Boozer, Phys. Plasmas 10, 3992 (2003)] to calculate the effects of magnetic perturbation from a current carrying coil. The coil position and coil current coil are

  3. Extending the validation of multi-mode model for anomalous transport to high beta poloidal tokamak scenario in DIII-D

    NASA Astrophysics Data System (ADS)

    Pankin, A. Y.; Kritz, A. H.; Rafiq, T.; Garofalo, A. M.; Holod, I.; Weiland, J.

    2018-05-01

    The Multi-Mode Model (MMM7.1) for anomalous transport is tested in predictive modeling of temperature profiles of a high beta poloidal DIII-D discharge. This new H-mode plasma regime, with high beta poloidal and high bootstrap currents, has been studied in DIII-D tokamak discharges [A. Garofalo et al., Nucl. Fusion 55, 123025 (2015)]. The role of instabilities that can drive the anomalous transport described by MMM7.1 is investigated. The temperature profiles for a high beta poloidal DIII-D discharge are computed using the NCLASS model for the neoclassical transport and the Weiland and Electron Temperature Gradient (ETG) components of the MMM7.1 model for the anomalous transport. The neoclassical transport is found to be the main contributor to the ion thermal transport in the plasma core. The contributions from the ion temperature gradient driven modes are found to be important only outside of the internal transport barrier. The magnitudes of the predicted temperature profiles are found to be in a reasonable agreement with experimental profiles. The simulation results approximately reproduce the internal transport barrier in the ion temperature profile but not in the electron temperature profile due to a weak dependence of the ETG driven transport on the Shafranov shift in the ETG component of MMM7.1. Possible effects that can contribute to stabilization of these modes, for example, effects associated with the large beta poloidal such as the Shafranov shift stabilization in the MMM7.1 model, are discussed. It is demonstrated that the E × B flow shear has a relatively small effect in the formation of the internal transport barrier in the high beta poloidal DIII-D discharge 154406. The Shafranov shift (alpha stabilization) and small or reversed magnetic shear profiles are found to be the primary reasons for quenched anomalous transport in this discharge.

  4. Status of fusion research and implications for D/He-3 systems

    NASA Technical Reports Server (NTRS)

    Miley, George H.

    1988-01-01

    World wide programs in both magnetic confinement and inertial confinement fusion research have made steady progress towards the experimental demonstration of energy breakeven. However, after breakeven is achieved, considerable time and effort must still be expended to develop a usable power plant. The main program described is focused on Deuterium-Tritium devices. In magnetic confinement, three of the most promising high beta approaches with a reasonable experimental data base are the Field Reversed Configuration, the high field tokamak, and the dense Z-pinch. The situation is less clear in inertial confinement where the first step requires an experimental demonstration of D/T spark ignition. It appears that fusion research has reached a point in time where an R and D plan to develop a D/He-3 fusion reactor can be laid out with some confidence of success.

  5. Mitochondrial cyclophilin D regulates T cell metabolic responses and disease tolerance to tuberculosis.

    PubMed

    Tzelepis, Fanny; Blagih, Julianna; Khan, Nargis; Gillard, Joshua; Mendonca, Laura; Roy, Dominic G; Ma, Eric H; Joubert, Philippe; Jones, Russell G; Divangahi, Maziar

    2018-05-11

    Mycobacterium tuberculosis ( Mtb ) is one of the most ancient human pathogens, yet the exact mechanism(s) of host defense against Mtb remains unclear. Although one-third of the world's population is chronically infected with Mtb , only 5 to 10% develop active disease. This indicates that, in addition to resistance mechanisms that control bacterial burden, the host has also evolved strategies to tolerate the presence of Mtb to limit disease severity. We identify mitochondrial cyclophilin D (CypD) as a critical checkpoint of T cell metabolism that controls the expansion of activated T cells. Although loss of CypD function in T cells led to enhanced Mtb antigen-specific T cell responses, this increased T cell response had no impact on bacterial burden. Rather, mice containing CypD-deficient T cells exhibited substantially compromised disease tolerance and succumbed to Mtb infection. This study establishes a mechanistic link between T cell-mediated immunity and disease tolerance during Mtb infection. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

  6. Measurement of branching fraction and time-dependent CP asymmetry parameters in B{sup 0}{yields}D*{sup +}D*{sup -}K{sub S}{sup 0} decays

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

    Dalseno, J.; Moloney, G. R.; Sevior, M. E.

    2007-10-01

    We present a measurement of the branching fraction and time-dependent CP violation parameters for B{sup 0}{yields}D*{sup +}D*{sup -}K{sub S}{sup 0} decays. These results are obtained from a 414 fb{sup -1} data sample that contains 449x10{sup 6} BB pairs collected at the {upsilon}(4S) resonance with the Belle detector at the KEKB asymmetric-energy e{sup +}e{sup -} collider. We obtain the branching fraction, B(B{sup 0}{yields}D*{sup +}D*{sup -}K{sub S}{sup 0})=[3.4{+-}0.4(stat){+-}0.7(syst)]x10{sup -3}, which is in agreement with the current world average. We also obtain an upper limit on the product branching fraction for a possible two-body decay, B(B{sup 0}{yields}D{sub s1}{sup +}(2536)D*{sup -})B(D{sub s1}{sup +}(2536){yields}D*{sup +}K{submore » S}{sup 0})<7.1x10{sup -4} (90% CL). In the traditional 2-parameter time-dependent CP analysis, we measure the CP violation parameters, A{sub CP}=-0.01{sub -0.28}{sup +0.28}(stat){+-}0.09(syst), Dsin2{phi}{sub 1}=0.06{sub -0.44}{sup +0.45}(stat){+-}0.06(syst). No evidence for either mixing-induced or direct CP violation is found. In a 3-parameter fit sensitive to cos2{phi}{sub 1} performed in the half-Dalitz spaces, s{sup -}{<=}s{sup +} and s{sup -}>s{sup +}, where s{sup {+-}}{identical_to}m{sup 2}(D*{sup {+-}}K{sub S}{sup 0}), we extract the CP violation parameters, J{sub c}/J{sub 0}=0.60{sub -0.28}{sup +0.25}(stat){+-}0.08(syst), 2J{sub s1}/J{sub 0}sin2{phi}{sub 1}=-0.17{sub -0.42}{sup +0.42}(stat){+-}0.09(syst), 2J{sub s2}/J{sub 0}cos2{phi}{sub 1}=-0.23{sub -0.41}{sup +0.43}(stat){+-}0.13(syst). A large value of J{sub c}/J{sub 0} would indicate a significant resonant contribution from a broad unknown D{sub s}**{sup +} state. Although the sign of the factor, 2J{sub s2}/J{sub 0}, can be deduced from theory, no conclusion can be drawn regarding the sign of cos2{phi}{sub 1} given the errors.« less

  7. Origin of Non-Gaussian Spectra Observed via the Charge Exchange Recombination Spectroscopy Diagnostic in the DIII-D Tokamak

    NASA Astrophysics Data System (ADS)

    Sulyman, Alex; Chrystal, Colin; Haskey, Shaun; Burrell, Keith; Grierson, Brian

    2017-10-01

    The possible observation of non-Maxwellian ion distribution functions in the pedestal of DIII-D will be investigated with a synthetic diagnostic that accounts for the effect of finite neutral beam size. Ion distribution functions in tokamak plasmas are typically assumed to be Maxwellian, however non-Gaussian features observed in impurity charge exchange spectra have challenged this concept. Two possible explanations for these observations are spatial averaging over a finite beam size and a local ion distribution that is non-Maxwellian. Non-Maxwellian ion distribution functions could be driven by orbit loss effects in the edge of the plasma, and this has implications for momentum transport and intrinsic rotation. To investigate the potential effect of finite beam size on the observed spectra, a synthetic diagnostic has been created that uses FIDAsim to model beam and halo neutral density. Finite beam size effects are investigated for vertical and tangential views in the core and pedestal region with varying gradient scale lengths. Work supported in part by US DoE under the Science Undergraduate Laboratory Internship (SULI) program, DE-FC02-04ER54698, and DE-AC02-09CH11466.

  8. High-resolution 3D-constructive interference in steady-state MR imaging and 3D time-of-flight MR angiography in neurovascular compression: a comparison between 3T and 1.5T.

    PubMed

    Garcia, M; Naraghi, R; Zumbrunn, T; Rösch, J; Hastreiter, P; Dörfler, A

    2012-08-01

    High-resolution MR imaging is useful for diagnosis and preoperative planning in patients with NVC. Because high-field MR imaging promises higher SNR and resolution, the aim of this study was to determine the value of high-resolution 3D-CISS and 3D-TOF MRA at 3T compared with 1.5T in patients with NVC. Forty-seven patients with NVC, trigeminal neuralgia, hemifacial spasm, and glossopharyngeal neuralgia were examined at 1.5T and 3T, including high-resolution 3D-CISS and 3D-TOF MRA sequences. Delineation of anatomic structures, overall image quality, severity of artifacts, visibility of NVC, and assessment of the SNR and CNR were compared between field strengths. SNR and CNR were significantly higher at 3T (P < .001). Significantly better anatomic conspicuity, including delineation of CNs, nerve branches, and assessment of small vessels, was obtained at 3T (P < .02). Severity of artifacts was significantly lower at 3T (P < .001). Consequently, overall image quality was significantly higher at 3T. NVC was significantly better delineated at 3T (P < .001). Six patients in whom NVC was not with certainty identifiable at 1.5T were correctly diagnosed at 3T. Patients with NVC may benefit from the higher resolution and greater sensitivity of 3T for preoperative assessment of NVC, and 3T may be of particular value when 1.5T is equivocal.

  9. Symplectic approach to calculation of magnetic field line trajectories in physical space with realistic magnetic geometry in divertor tokamaks

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

    Punjabi, Alkesh; Ali, Halima

    A new approach to integration of magnetic field lines in divertor tokamaks is proposed. In this approach, an analytic equilibrium generating function (EGF) is constructed in natural canonical coordinates ({psi},{theta}) from experimental data from a Grad-Shafranov equilibrium solver for a tokamak. {psi} is the toroidal magnetic flux and {theta} is the poloidal angle. Natural canonical coordinates ({psi},{theta},{phi}) can be transformed to physical position (R,Z,{phi}) using a canonical transformation. (R,Z,{phi}) are cylindrical coordinates. Another canonical transformation is used to construct a symplectic map for integration of magnetic field lines. Trajectories of field lines calculated from this symplectic map in natural canonicalmore » coordinates can be transformed to trajectories in real physical space. Unlike in magnetic coordinates [O. Kerwin, A. Punjabi, and H. Ali, Phys. Plasmas 15, 072504 (2008)], the symplectic map in natural canonical coordinates can integrate trajectories across the separatrix surface, and at the same time, give trajectories in physical space. Unlike symplectic maps in physical coordinates (x,y) or (R,Z), the continuous analog of a symplectic map in natural canonical coordinates does not distort trajectories in toroidal planes intervening the discrete map. This approach is applied to the DIII-D tokamak [J. L. Luxon and L. E. Davis, Fusion Technol. 8, 441 (1985)]. The EGF for the DIII-D gives quite an accurate representation of equilibrium magnetic surfaces close to the separatrix surface. This new approach is applied to demonstrate the sensitivity of stochastic broadening using a set of perturbations that generically approximate the size of the field errors and statistical topological noise expected in a poloidally diverted tokamak. Plans for future application of this approach are discussed.« less

  10. Spatially resolved D-T(2) correlation NMR of porous media.

    PubMed

    Zhang, Yan; Blümich, Bernhard

    2014-05-01

    Within the past decade, 2D Laplace nuclear magnetic resonance (NMR) has been developed to analyze pore geometry and diffusion of fluids in porous media on the micrometer scale. Many objects like rocks and concrete are heterogeneous on the macroscopic scale, and an integral analysis of microscopic properties provides volume-averaged information. Magnetic resonance imaging (MRI) resolves this spatial average on the contrast scale set by the particular MRI technique. Desirable contrast parameters for studies of fluid transport in porous media derive from the pore-size distribution and the pore connectivity. These microscopic parameters are accessed by 1D and 2D Laplace NMR techniques. It is therefore desirable to combine MRI and 2D Laplace NMR to image functional information on fluid transport in porous media. Because 2D Laplace resolved MRI demands excessive measuring time, this study investigates the possibility to restrict the 2D Laplace analysis to the sum signals from low-resolution pixels, which correspond to pixels of similar amplitude in high-resolution images. In this exploratory study spatially resolved D-T2 correlation maps from glass beads and mortar are analyzed. Regions of similar contrast are first identified in high-resolution images to locate corresponding pixels in low-resolution images generated with D-T2 resolved MRI for subsequent pixel summation to improve the signal-to-noise ratio of contrast-specific D-T2 maps. This method is expected to contribute valuable information on correlated sample heterogeneity from the macroscopic and the microscopic scales in various types of porous materials including building materials and rock. Copyright © 2014 Elsevier Inc. All rights reserved.

  11. Non-Solenoidal Tokamak Startup via Inboard Local Helicity Injection on the Pegasus ST

    NASA Astrophysics Data System (ADS)

    Perry, J. M.; Barr, J. L.; Bodner, G. M.; Bongard, M. W.; Fonck, R. J.; Pachicano, J. L.; Reusch, J. A.; Rodriguez Sanchez, C.; Richner, N. J.; Schlossberg, D. J.

    2016-10-01

    Local helicity injection (LHI) is a non-solenoidal startup technique utilizing small injectors at the plasma edge to source current along helical magnetic field lines. Unstable injected current streams relax to a tokamak-like configuration with high toroidal current multiplication. Flexible placement of injectors permits tradeoffs between helicity injection rate, poloidal field induction, and magnetic geometry requirements for initial relaxation. Experiments using a new set of large-area injectors in the lower divertor explore the efficacy of high-field-side (HFS) injection. The increased area (4 cm2) current source is functional up to full Pegasus toroidal field (BT , inj = 0.23 T). However, relaxation to a tokamak state is increasingly frustrated for BT , inj > 0.15 T with uniform vacuum vertical field. Paths to relaxation at increased field include: manipulation of vacuum poloidal field geometry; increased injector current; and plasma initiation with outboard injectors, subsequently transitioning to divertor injector drive. During initial tests of HFS injectors, achieved Vinj was limited to 600 V by plasma-material interactions on the divertor plate, which may be mitigated by increasing injector elevation. In experiments with helicity injection as the dominant current drive Ip 0.13 MA has been attained, with T̲e > 100 eV and ne 1019 m-3. Extrapolation to full BT, longer pulse length, and Vinj 1 kV suggest Ip > 0.25 MA should be attainable in a plasma dominated by helicity drive. Work supported by US DOE Grant DE-FG02-96ER54375.

  12. A comparison study between 3D T2-weighted SPACE and conventional 2D T2-weighted turbo spin echo in assessment of carotid plaque.

    PubMed

    Lv, Peng; Dai, Yuanyuan; Lin, Jiang; Zhang, Weisheng; Liu, Hao; Liu, Hui; Tang, Xiao

    2017-03-01

    The aim of this study was to compare 3D T2-weighted sampling perfection with application optimized contrast using different flip angle evolutions (T2w SPACE) with conventional 2D T2w turbo-spin echo (TSE) in plaque imaging of carotid artery. 45 patients underwent 3.0-T MRI for carotid arteries imaging. MR sequences included T2w SPACE, T2w TSE, Time of flight (TOF) and T1-weighted (T1w) TSE. The signal intensity of intra-plaque hemorrhage (IPH), lipid-rich necrotic core (LRNC), and loose matrix (LM) were measured and their contrast ratios (CRs) against adjacent muscle were calculated. CRs from T2w SPACE and T2w TSE were compared to each other. CRs of LM, LRNC, and IPH measured on T2w SPACE were 1.74-3.04 (2.44), 0.98-1.66 (1.39), and 1.91-2.93 (2.51), respectively. CRs of LM, LRNC, and IPH on T2w TSE were 1.97-3.41 (2.44), 1.18-1.73 (1.43), and 2.26-3.75 (2.26), respectively. There was no significant difference of CR of the carotid plaques between T2w SPACE and T2w TSE (p = 0.455). Markedly significant differences of CRs were found between LM and LRNC (p < 0.001), and between LRNC and IPH (p < 0.001) on T2w SPACE and T2w TSE. T2w SPACE was comparable with conventional T2w TSE in characterization of carotid plaque.

  13. ADX: a high field, high power density, advanced divertor and RF tokamak

    NASA Astrophysics Data System (ADS)

    LaBombard, B.; Marmar, E.; Irby, J.; Terry, J. L.; Vieira, R.; Wallace, G.; Whyte, D. G.; Wolfe, S.; Wukitch, S.; Baek, S.; Beck, W.; Bonoli, P.; Brunner, D.; Doody, J.; Ellis, R.; Ernst, D.; Fiore, C.; Freidberg, J. P.; Golfinopoulos, T.; Granetz, R.; Greenwald, M.; Hartwig, Z. S.; Hubbard, A.; Hughes, J. W.; Hutchinson, I. H.; Kessel, C.; Kotschenreuther, M.; Leccacorvi, R.; Lin, Y.; Lipschultz, B.; Mahajan, S.; Minervini, J.; Mumgaard, R.; Nygren, R.; Parker, R.; Poli, F.; Porkolab, M.; Reinke, M. L.; Rice, J.; Rognlien, T.; Rowan, W.; Shiraiwa, S.; Terry, D.; Theiler, C.; Titus, P.; Umansky, M.; Valanju, P.; Walk, J.; White, A.; Wilson, J. R.; Wright, G.; Zweben, S. J.

    2015-05-01

    The MIT Plasma Science and Fusion Center and collaborators are proposing a high-performance Advanced Divertor and RF tokamak eXperiment (ADX)—a tokamak specifically designed to address critical gaps in the world fusion research programme on the pathway to next-step devices: fusion nuclear science facility (FNSF), fusion pilot plant (FPP) and/or demonstration power plant (DEMO). This high-field (⩾6.5 T, 1.5 MA), high power density facility (P/S ˜ 1.5 MW m-2) will test innovative divertor ideas, including an ‘X-point target divertor’ concept, at the required performance parameters—reactor-level boundary plasma pressures, magnetic field strengths and parallel heat flux densities entering into the divertor region—while simultaneously producing high-performance core plasma conditions that are prototypical of a reactor: equilibrated and strongly coupled electrons and ions, regimes with low or no torque, and no fuelling from external heating and current drive systems. Equally important, the experimental platform will test innovative concepts for lower hybrid current drive and ion cyclotron range of frequency actuators with the unprecedented ability to deploy launch structures both on the low-magnetic-field side and the high-magnetic-field side—the latter being a location where energetic plasma-material interactions can be controlled and favourable RF wave physics leads to efficient current drive, current profile control, heating and flow drive. This triple combination—advanced divertors, advanced RF actuators, reactor-prototypical core plasma conditions—will enable ADX to explore enhanced core confinement physics, such as made possible by reversed central shear, using only the types of external drive systems that are considered viable for a fusion power plant. Such an integrated demonstration of high-performance core-divertor operation with steady-state sustainment would pave the way towards an attractive pilot plant, as envisioned in the ARC concept

  14. Time-of-Flight Measurements of Neutron Yields from Implosions at the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Caggaino, Joseph

    2014-10-01

    Three 20-m time-of-flight detectors measure neutron spectra from implosions of deuterium-tritium targets at the National Ignition Facility. Two prominent peaks appear in the spectra from the T(d, n) and D(d, n) reactions. The ratio of yields extracted from the peaks depend on the DT and DD reaction rates and attenuation from the compressed DT fuel, which makes the ratio a diagnostic of the hotspot thermodynamics and fuel areal density. The measured peak widths provide additional constraints on reactant temperature. Recent measurements from a high-yield campaign will be presented and compared to radiation-hydrodynamic simulations of similar implosions. This research is supported by the Department of Energy National Nuclear Security Administration under Contract DE-NA0001944.

  15. Comparison of FSE T2 W PROPELLER and 3D-FIESTA of 3 T MR for the internal auditory canal.

    PubMed

    Wu, Hai-Bo; Yuan, Hui-Shu; Ma, Furong; Zhao, Qiang

    The study compared the use of periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) technique fast spin echo (FSE) T2 W and the sequence of three-dimensional fast imaging employing steady-state acquisition (3D-FIESTA) technique in the MRI of the internal auditory canal for overall image quality improvement. One hundred thirty-two patients undergoing FSE T2 W PROPELLER and 3D-FIESTA examinations of the internal auditory canal were included. All examinations were performed at 3.0 T with comparison of a sagittal oblique FSE T2 W sequence with the PROPELLER technique to 3D-FIESTA in the same reconstructed orientation with PROPELLER. Image quality was evaluated by two radiologists using a 4-point scale. The Wilcoxon signed rank test was used to compare the data of the two techniques. The image quality of FSE T2 W PROPELLER was significantly improved compared to the reconstructed images of 3D-FIESTA. Observer 1: median FSE T2 W with PROPELLER, 4 [mean, 3.455] versus median reconstructed 3D-FIESTA, 3 [mean, 3.15], (P<.001); Observer 2: median FSE T2 W with PROPELLER, 4 [mean, 3.47] versus median reconstructed 3D-FIESTA, 3 [mean, 3.25], (P<.001). Interobserver agreement was good (k value, 0.73) for the rating of the overall image quality. The FSE T2 W PROPELLER technique for MRI of internal auditory canal reduced uncertainty caused by motion artifact and improved the quality of the image compared to the reconstructed 3D-FIESTA. It was affected by different parameters including the blade width, echo train length (ETL). This is explained by data oversampling at the center region of k-space, which requires additional imaging time over conventional MRI techniques. Increasing blade was expected to improve motion correction effects but also the signal-to-noise ratio. ETL increases the image sharpness and the overall image quality. Copyright © 2016. Published by Elsevier Inc.

  16. Source-to-incident-flux relation in a Tokamak blanket module

    NASA Astrophysics Data System (ADS)

    Imel, G. R.

    The next-generation Tokamak experiments, including the Tokamak fusion test reactor (TFTR), will utilize small blanket modules to measure performance parameters such as tritium breeding profiles, power deposition profiles, and neutron flux profiles. Specifically, a neutron calorimeter (simply a neutron moderating blanket module) which permits inferring the incident 14 MeV flux based on measured temperature profiles was proposed for TFTR. The problem of how to relate this total scalar flux to the fusion neutron source is addressed. This relation is necessary since the calorimeter is proposed as a total fusion energy monitor. The methods and assumptions presented was valid for the TFTR Lithium Breeding Module (LBM), as well as other modules on larger Tokamak reactors.

  17. Plasma production and preliminary results from the ADITYA Upgrade tokamak

    NASA Astrophysics Data System (ADS)

    R, L. TANNA; J, GHOSH; Harshita, RAJ; Rohit, KUMAR; Suman, AICH; Vaibhav, RANJAN; K, A. JADEJA; K, M. PATEL; S, B. BHATT; K, SATHYANARAYANA; P, K. CHATTOPADHYAY; M, N. MAKWANA; K, S. SHAH; C, N. GUPTA; V, K. PANCHAL; Praveenlal, EDAPPALA; Bharat, ARAMBHADIYA; Minsha, SHAH; Vismay, RAULJI; M, B. CHOWDHURI; S, BANERJEE; R, MANCHANDA; D, RAJU; P, K. ATREY; Umesh, NAGORA; J, RAVAL; Y, S. JOISA; K, TAHILIANI; S, K. JHA; M, V. GOPALKRISHANA

    2018-07-01

    The Ohmically heated circular limiter tokamak ADITYA (R 0 = 75 cm, a = 25 cm) has been upgraded to a tokamak named the ADITYA Upgrade (ADITYA-U) with an open divertor configuration with divertor plates. The main goal of ADITYA-U is to carry out dedicated experiments relevant for bigger fusion machines including ITER, such as the generation and control of runaway electrons, disruption prediction, and mitigation studies, along with an improvement in confinement with shaped plasma. The ADITYA tokamak was dismantled and the assembly of ADITYA-U was completed in March 2016. Integration of subsystems like data acquisition and remote operation along with plasma production and preliminary plasma characterization of ADITYA-U plasmas are presented in this paper.

  18. Consideration of neutral beam prompt loss in the design of a tokamak helicon antenna

    DOE PAGES

    Pace, D. C.; Van Zeeland, M. A.; Fishler, B.; ...

    2016-08-02

    Neutral beam prompt losses (injected neutrals that ionize such that their first poloidal transit intersects with the wall) can put appreciable power on the outer wall of tokamaks, and this power may damage the wall or other internal components. These prompt losses are simulated including a protruding helicon antenna installation in the DIII-D tokamak and it is determined that 160 kW of power will impact the antenna during the injection of a particular neutral beam. Protective graphite tiles are designed in response to this modeling and the wall shape of the installed antenna is precisely measured to improve the accuracymore » of these calculations. Initial experiments con rm that the antenna component temperature increases according to the amount of neutral beam energy injected into the plasma. Incorporating neutral beam prompt loss considerations into the design of this in-vessel component serves to ensure that adequate protection or cooling is provided.« less

  19. Consideration of neutral beam prompt loss in the design of a tokamak helicon antenna

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

    Pace, D. C.; Van Zeeland, M. A.; Fishler, B.

    Neutral beam prompt losses (injected neutrals that ionize such that their first poloidal transit intersects with the wall) can put appreciable power on the outer wall of tokamaks, and this power may damage the wall or other internal components. These prompt losses are simulated including a protruding helicon antenna installation in the DIII-D tokamak and it is determined that 160 kW of power will impact the antenna during the injection of a particular neutral beam. Protective graphite tiles are designed in response to this modeling and the wall shape of the installed antenna is precisely measured to improve the accuracymore » of these calculations. Initial experiments con rm that the antenna component temperature increases according to the amount of neutral beam energy injected into the plasma. Incorporating neutral beam prompt loss considerations into the design of this in-vessel component serves to ensure that adequate protection or cooling is provided.« less

  20. Maximum entropy reconstruction of poloidal magnetic field and radial electric field profiles in tokamaks

    NASA Astrophysics Data System (ADS)

    Chen, Yihang; Xiao, Chijie; Yang, Xiaoyi; Wang, Tianbo; Xu, Tianchao; Yu, Yi; Xu, Min; Wang, Long; Lin, Chen; Wang, Xiaogang

    2017-10-01

    The Laser-driven Ion beam trace probe (LITP) is a new diagnostic method for measuring poloidal magnetic field (Bp) and radial electric field (Er) in tokamaks. LITP injects a laser-driven ion beam into the tokamak, and Bp and Er profiles can be reconstructed using tomography methods. A reconstruction code has been developed to validate the LITP theory, and both 2D reconstruction of Bp and simultaneous reconstruction of Bp and Er have been attained. To reconstruct from experimental data with noise, Maximum Entropy and Gaussian-Bayesian tomography methods were applied and improved according to the characteristics of the LITP problem. With these improved methods, a reconstruction error level below 15% has been attained with a data noise level of 10%. These methods will be further tested and applied in the following LITP experiments. Supported by the ITER-CHINA program 2015GB120001, CHINA MOST under 2012YQ030142 and National Natural Science Foundation Abstract of China under 11575014 and 11375053.

  1. Multi-region approach to free-boundary three-dimensional tokamak equilibria and resistive wall instabilities

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

    Ferraro, N. M.; Jardin, S. C.; Lao, L. L.

    Free-boundary 3D tokamak equilibria and resistive wall instabilities are calculated using a new resistive wall model in the two-fluid M3D-C1 code. In this model, the resistive wall and surround- ing vacuum region are included within the computational domain. Our implementation contrasts with the method typically used in fluid codes in which the resistive wall is treated as a boundary condition on the computational domain boundary and has the advantage of maintaining purely local coupling of mesh elements. We use this new capability to simulate perturbed, free-boundary non- axisymmetric equilibria; the linear evolution of resistive wall modes; and the linear andmore » nonlinear evolution of axisymmetric vertical displacement events (VDEs). Calculated growth rates for a resistive wall mode with arbitrary wall thickness are shown to agree well with the analytic theory. Equilibrium and VDE calculations are performed in diverted tokamak geometry, at physically real- istic values of dissipation, and with resistive walls of finite width. Simulations of a VDE disruption extend into the current-quench phase, in which the plasma becomes limited by the first wall, and strong currents are observed to flow in the wall, in the SOL, and from the plasma to the wall.« less

  2. Multi-region approach to free-boundary three-dimensional tokamak equilibria and resistive wall instabilities

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

    Ferraro, N. M., E-mail: nferraro@pppl.gov; Lao, L. L.; Jardin, S. C.

    Free-boundary 3D tokamak equilibria and resistive wall instabilities are calculated using a new resistive wall model in the two-fluid M3D-C1 code. In this model, the resistive wall and surrounding vacuum region are included within the computational domain. This implementation contrasts with the method typically used in fluid codes in which the resistive wall is treated as a boundary condition on the computational domain boundary and has the advantage of maintaining purely local coupling of mesh elements. This new capability is used to simulate perturbed, free-boundary non-axisymmetric equilibria; the linear evolution of resistive wall modes; and the linear and nonlinear evolutionmore » of axisymmetric vertical displacement events (VDEs). Calculated growth rates for a resistive wall mode with arbitrary wall thickness are shown to agree well with the analytic theory. Equilibrium and VDE calculations are performed in diverted tokamak geometry, at physically realistic values of dissipation, and with resistive walls of finite width. Simulations of a VDE disruption extend into the current-quench phase, in which the plasma becomes limited by the first wall, and strong currents are observed to flow in the wall, in the SOL, and from the plasma to the wall.« less

  3. Multi-region approach to free-boundary three-dimensional tokamak equilibria and resistive wall instabilities

    NASA Astrophysics Data System (ADS)

    Ferraro, N. M.; Jardin, S. C.; Lao, L. L.; Shephard, M. S.; Zhang, F.

    2016-05-01

    Free-boundary 3D tokamak equilibria and resistive wall instabilities are calculated using a new resistive wall model in the two-fluid M3D-C1 code. In this model, the resistive wall and surrounding vacuum region are included within the computational domain. This implementation contrasts with the method typically used in fluid codes in which the resistive wall is treated as a boundary condition on the computational domain boundary and has the advantage of maintaining purely local coupling of mesh elements. This new capability is used to simulate perturbed, free-boundary non-axisymmetric equilibria; the linear evolution of resistive wall modes; and the linear and nonlinear evolution of axisymmetric vertical displacement events (VDEs). Calculated growth rates for a resistive wall mode with arbitrary wall thickness are shown to agree well with the analytic theory. Equilibrium and VDE calculations are performed in diverted tokamak geometry, at physically realistic values of dissipation, and with resistive walls of finite width. Simulations of a VDE disruption extend into the current-quench phase, in which the plasma becomes limited by the first wall, and strong currents are observed to flow in the wall, in the SOL, and from the plasma to the wall.

  4. Multi-region approach to free-boundary three-dimensional tokamak equilibria and resistive wall instabilities

    DOE PAGES

    Ferraro, N. M.; Jardin, S. C.; Lao, L. L.; ...

    2016-05-20

    Free-boundary 3D tokamak equilibria and resistive wall instabilities are calculated using a new resistive wall model in the two-fluid M3D-C1 code. In this model, the resistive wall and surround- ing vacuum region are included within the computational domain. Our implementation contrasts with the method typically used in fluid codes in which the resistive wall is treated as a boundary condition on the computational domain boundary and has the advantage of maintaining purely local coupling of mesh elements. We use this new capability to simulate perturbed, free-boundary non- axisymmetric equilibria; the linear evolution of resistive wall modes; and the linear andmore » nonlinear evolution of axisymmetric vertical displacement events (VDEs). Calculated growth rates for a resistive wall mode with arbitrary wall thickness are shown to agree well with the analytic theory. Equilibrium and VDE calculations are performed in diverted tokamak geometry, at physically real- istic values of dissipation, and with resistive walls of finite width. Simulations of a VDE disruption extend into the current-quench phase, in which the plasma becomes limited by the first wall, and strong currents are observed to flow in the wall, in the SOL, and from the plasma to the wall.« less

  5. Applying the new HIT results to tokamak and solar plasmas

    NASA Astrophysics Data System (ADS)

    Jarboe, Thomas; Sutherland, Derek; Hossack, Aaron; Nelson, Brian; Morgan, Kyle; Chris, Hansen; Benedett, Thomas; Everson, Chris; Penna, James

    2016-10-01

    Understanding sustainment of stable equilibria with helicity injection in HIT-SI has led to a simple picture of several tokamak features. Perturbations cause a viscous-like force on the current that flattens the λ profile, which sustains and stabilizes the equilibrium. An explanation of the mechanism is based on two properties of stable, ideal, two-fluid, magnetized plasma. First, the electron fluid is frozen to magnetic fields and, therefore, current flow is also magnetic field flow. Second, for a stable equilibrium the structure perpendicular to the flux surface resists deformation. Thus toroidal current is from electrons frozen in nested, rotating resilient flux surfaces. Only symmetric flux surfaces allow free differential current flow. Perturbations cause interference of the flux surfaces. Thus, perturbations cause forces that oppose differential electron rotation and forced differential flow produces a symmetrizing force against perturbations and instability. This mechanism can explain the level of field error that spoils tokamak performance and the rate of poloidal flux loss in argon-induced disruptions in DIII-D. This new understanding has led to an explanation of the source of the solar magnetic fields and the power source for the chromosphere, solar wind and corona. Please place in spheromak and FRC section with other HIT posters.

  6. Spatial and temporal analysis of DIII-D 3D magnetic diagnostic data

    DOE PAGES

    Strait, E. J.; King, J. D.; Hanson, J. M.; ...

    2016-08-11

    An extensive set of magnetic diagnostics in DIII-D is aimed at measuring non-axisymmetric "3D" features of tokamak plasmas, with typical amplitudes ~10 -3 to 10 -5 of the total magnetic field. We describe hardware and software techniques used at DIII-D to condition the individual signals and analysis to estimate the spatial structure from an ensemble of discrete measurements. Lastly, applications of the analysis include detection of non-rotating MHD instabilities, plasma control, and validation of MHD stability and 3D equilibrium models.

  7. Impedance of an intense plasma-cathode electron source for tokamak startup

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    An impedance model is formulated and tested for the ˜1 kV , 1 kA/cm2 , arc-plasma cathode electron source used for local helicity injection tokamak startup. A double layer sheath is established between the high-density arc plasma ( narc≈1021 m-3 ) within the electron source, and the less dense external tokamak edge plasma ( nedge≈1018 m-3 ) into which current is injected at the applied injector voltage, Vinj . Experiments on the Pegasus spherical tokamak show that the injected current, Iinj , increases with Vinj according to the standard double layer scaling Iinj˜Vinj3 /2 at low current and transitions to Iinj˜Vinj1 /2 at high currents. In this high current regime, sheath expansion and/or space charge neutralization impose limits on the beam density nb˜Iinj/Vinj1 /2 . For low tokamak edge density nedge and high Iinj , the inferred beam density nb is consistent with the requirement nb≤nedge imposed by space-charge neutralization of the beam in the tokamak edge plasma. At sufficient edge density, nb˜narc is observed, consistent with a limit to nb imposed by expansion of the double layer sheath. These results suggest that narc is a viable control actuator for the source impedance.

  8. 3D Field Modifications of Core Neutral Fueling In the EMC3-EIRENE Code

    NASA Astrophysics Data System (ADS)

    Waters, Ian; Frerichs, Heinke; Schmitz, Oliver; Ahn, Joon-Wook; Canal, Gustavo; Evans, Todd; Feng, Yuehe; Kaye, Stanley; Maingi, Rajesh; Soukhanovskii, Vsevolod

    2017-10-01

    The application of 3-D magnetic field perturbations to the edge plasmas of tokamaks has long been seen as a viable way to control damaging Edge Localized Modes (ELMs). These 3-D fields have also been correlated with a density drop in the core plasmas of tokamaks; known as `pump-out'. While pump-out is typically explained as the result of enhanced outward transport, degraded fueling of the core may also play a role. By altering the temperature and density of the plasma edge, 3-D fields will impact the distribution function of high energy neutral particles produced through ion-neutral energy exchange processes. Starved of the deeply penetrating neutral source, the core density will decrease. Numerical studies carried out with the EMC3-EIRENE code on National Spherical Tokamak eXperiment-Upgrade (NSTX-U) equilibria show that this change to core fueling by high energy neutrals may be a significant contributor to the overall particle balance in the NSTX-U tokamak: deep core (Ψ < 0.5) fueling from neutral ionization sources is decreased by 40-60% with RMPs. This work was funded by the US Department of Energy under Grant DE-SC0012315.

  9. 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.

  10. The Dynamic Mutation Characteristics of Thermonuclear Reaction in Tokamak

    PubMed Central

    Li, Jing; Quan, Tingting; Zhang, Wei; Deng, Wei

    2014-01-01

    The stability and bifurcations of multiple limit cycles for the physical model of thermonuclear reaction in Tokamak are investigated in this paper. The one-dimensional Ginzburg-Landau type perturbed diffusion equations for the density of the plasma and the radial electric field near the plasma edge in Tokamak are established. First, the equations are transformed to the average equations with the method of multiple scales and the average equations turn to be a Z 2-symmetric perturbed polynomial Hamiltonian system of degree 5. Then, with the bifurcations theory and method of detection function, the qualitative behavior of the unperturbed system and the number of the limit cycles of the perturbed system for certain groups of parameter are analyzed. At last, the stability of the limit cycles is studied and the physical meaning of Tokamak equations under these parameter groups is given. PMID:24892099

  11. Solenoid-free plasma start-up in spherical tokamaks

    NASA Astrophysics Data System (ADS)

    Raman, R.; Shevchenko, V. F.

    2014-10-01

    The central solenoid is an intrinsic part of all present-day tokamaks and most spherical tokamaks. The spherical torus (ST) confinement concept is projected to operate at high toroidal beta and at a high fraction of the non-inductive bootstrap current as required for an efficient reactor system. The use of a conventional solenoid in a ST-based fusion nuclear facility is generally believed to not be a possibility. Solenoid-free plasma start-up is therefore an area of extensive worldwide research activity. Solenoid-free plasma start-up is also relevant to steady-state tokamak operation, as the central transformer coil of a conventional aspect ratio tokamak reactor would be located in a high radiation environment but would be needed only during the initial discharge initiation and current ramp-up phases. Solenoid-free operation also provides greater flexibility in the selection of the aspect ratio and simplifies the reactor design. Plasma start-up methods based on induction from external poloidal field coils, helicity injection and radio frequency current drive have all made substantial progress towards meeting this important need for the ST. Some of these systems will now undergo the final stages of test in a new generation of large STs, which are scheduled to begin operations during the next two years. This paper reviews research to date on methods for inducing the initial start-up current in STs without reliance on the conventional central solenoid.

  12. Depopulation of highly excited singlet states of DNA model compounds: quantum yields of 193 and 245 nm photoproducts of pyrimidine monomers and dinucleoside monophosphates.

    PubMed

    Gurzadyan, G G; Görner, H

    1996-02-01

    Formation of uracil and orotic acid photodimers, uridine and 5'-UMP photohydrates, TpT photodimers and (6-4)photoproducts, dCpT photohydrates and (6-4)photoproducts and UpU, CpC and CpU photohydrates were studied in neutral deoxygenated aqueous solution at room temperature upon irradiation at either 193 or 254 nm. The photoproducts were identified and quantified and the contribution from photoionization to substrate decomposition, using lambda irr = 193 nm, was separated. The ratio of the quantum yields of respective stable products, eta = phi 193/phi 254, is indicative of the yield of internal conversion from the second to the first excited singlet state, S2-->S1. For the observed photodimers eta decreases from 0.94 for uracil to 0.7 for TpT and further to 0.55 for orotic acid. For the (6-4)photoproducts of TpT and dCpT eta = 0.5-0.8 and for the photohydrates in the cases of UpU, CpC, CpU and dCpT eta ranges from 0.55 to 1.

  13. Properties of ion temperature gradient and trapped electron modes in tokamak plasmas with inverted density profiles

    NASA Astrophysics Data System (ADS)

    Du, Huarong; Jhang, Hogun; Hahm, T. S.; Dong, J. Q.; Wang, Z. X.

    2017-12-01

    We perform a numerical study of linear stability of the ion temperature gradient (ITG) mode and the trapped electron mode (TEM) in tokamak plasmas with inverted density profiles. A local gyrokinetic integral equation is applied for this study. From comprehensive parametric scans, we obtain stability diagrams for ITG modes and TEMs in terms of density and temperature gradient scale lengths. The results show that, for the inverted density profile, there exists a normalized threshold temperature gradient above which the ITG mode and the TEM are either separately or simultaneously unstable. The instability threshold of the TEM for the inverted density profile is substantially different from that for normal and flat density profiles. In addition, deviations are found on the ITG threshold from an early analytic theory in sheared slab geometry with the adiabatic electron response [T. S. Hahm and W. M. Tang, Phys. Fluids B 1, 1185 (1989)]. A possible implication of this work on particle transport in pellet fueled tokamak plasmas is discussed.

  14. First Measurements of Deuterium-Tritium and Deuterium-Deuterium Fusion Reaction Yields in Ignition-Scalable Direct-Drive Implosions

    NASA Astrophysics Data System (ADS)

    Forrest, C. J.; Radha, P. B.; Knauer, J. P.; Glebov, V. Yu.; Goncharov, V. N.; Regan, S. P.; Rosenberg, M. J.; Sangster, T. C.; Shmayda, W. T.; Stoeckl, C.; Gatu Johnson, M.

    2017-03-01

    The deuterium-tritium (D-T) and deuterium-deuterium neutron yield ratio in cryogenic inertial confinement fusion (ICF) experiments is used to examine multifluid effects, traditionally not included in ICF modeling. This ratio has been measured for ignition-scalable direct-drive cryogenic DT implosions at the Omega Laser Facility [T. R. Boehly et al., Opt. Commun. 133, 495 (1997), 10.1016/S0030-4018(96)00325-2] using a high-dynamic-range neutron time-of-flight spectrometer. The experimentally inferred yield ratio is consistent with both the calculated values of the nuclear reaction rates and the measured preshot target-fuel composition. These observations indicate that the physical mechanisms that have been proposed to alter the fuel composition, such as species separation of the hydrogen isotopes [D. T. Casey et al., Phys. Rev. Lett. 108, 075002 (2012), 10.1103/PhysRevLett.108.075002], are not significant during the period of peak neutron production in ignition-scalable cryogenic direct-drive DT implosions.

  15. Neoclassical toroidal viscosity calculations in tokamaks using a δf Monte Carlo simulation and their verifications.

    PubMed

    Satake, S; Park, J-K; Sugama, H; Kanno, R

    2011-07-29

    Neoclassical toroidal viscosities (NTVs) in tokamaks are investigated using a δf Monte Carlo simulation, and are successfully verified with a combined analytic theory over a wide range of collisionality. A Monte Carlo simulation has been required in the study of NTV since the complexities in guiding-center orbits of particles and their collisions cannot be fully investigated by any means of analytic theories alone. Results yielded the details of the complex NTV dependency on particle precessions and collisions, which were predicted roughly in a combined analytic theory. Both numerical and analytic methods can be utilized and extended based on these successful verifications.

  16. MHD Studies of Advanced Tokamak Equilibria

    NASA Astrophysics Data System (ADS)

    Strumberger, E.

    2005-10-01

    Advanced tokamak scenarios are often characterized by an extremely reversed profile of the safety factor, q, and a fast toroidal rotation. ASDEX Upgrade type equilibria with toroidal flow are computed up to a toroidal Mach number of Mta= 0.5, and compared with the static solution. Using these equilibria, the stabilizing effect of differential toroidal rotation on double tearing modes (DTMs) is investigated. These studies show that the computation of equilibria with flow is necessary for toroidally rotating plasma with Mta>=0.2. The use of ρtor instead of ρpol as radial coordinate enables us also to investigate the stability of equilibria with current holes. For numerical reasons, the rotational transform, = 1/q, has to be unequal zero in the CASTOR$FLOW code, but values of a>=0.001 (qa<=1000) can be easily handled. Stability studies of DTMs in the presence of a current hole are presented. Tokamak equilibria are only approximately axisymmetric. The finite number of toroidal field coils destroys the perfect axisymmetry of the device, and the coils produce a short wavelength ripple in the magnetic field strength. This toroidal field ripple plays a crucial role for the loss of high energy particles. Therefore, three-dimensional tokamak equilibria with and without current holes are computed for various plasma beta values. In addition the influence of the plasma beta on the toroidal field ripple is investigated.

  17. Spherical tokamaks with plasma centre-post

    NASA Astrophysics Data System (ADS)

    Ribeiro, Celso

    2013-10-01

    The metal centre-post (MCP) in tokamaks is a structure which carries the total toroidal field current and also houses the Ohmic heating solenoid in conventional or low aspect ratio (Spherical)(ST) tokamaks. The MCP and solenoid are critical components for producing the toroidal field and for the limited Ohmic flux in STs. Constraints for a ST reactor related to these limitations lead to a minimum plasma aspect ratio of 1.4 which reduces the benefit of operation at higher betas in a more compact ST reactor. Replacing the MCP is of great interest for reactor-based ST studies since the device is simplified, compactness increased, and maintenance reduced. An experiment to show the feasibility of using a plasma centre-post (PCP) is being currently under construction and involves a high level of complexity. A preliminary study of a very simple PCP, which is ECR(Electron Cyclotron Resonance)-assisted and which includes an innovative fuelling system based on pellet injection, has recently been reported. This is highly suitable for an ultra-low aspect ratio tokamak (ULART) device. Advances on this PCP ECR-assisted concept within a ULART and the associated fuelling system are presented here, and will include the field topology for the PCP ECR-assisted scheme, pellet ablation modeling, and a possible global equilibrium simulation. VIE-ITCR, IAEA-CRP contr.17592, National Instruments-Costa Rica.

  18. The effect of pressure anisotropy on ballooning modes in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Johnston, A.; Hole, M. J.; Qu, Z. S.; Hezaveh, H.

    2018-06-01

    Edge Localised Modes are thought to be caused by a spectrum of magnetohydrodynamic instabilities, including the ballooning mode. While ballooning modes have been studied extensively both theoretically and experimentally, the focus of the vast majority of this research has been on isotropic plasmas. The prevalence of pressure anisotropy in modern tokamaks thus motivates further study of these modes. This paper presents a numerical analysis of ballooning modes in anisotropic equilibria. The investigation was conducted using the newly-developed codes HELENA+ATF and MISHKA-A, which adds anisotropic physics to equilibria and stability analysis. We have examined the impact of anisotropy on the stability of an n = 30 ballooning mode, confirming results conform to previous calculations in the isotropic limit. Growth rates of ballooning modes in equilibria with different levels of anisotropy were then calculated using the stability code MISHKA-A. The key finding was that the level of anisotropy had a significant impact on ballooning mode growth rates. For {T}\\perp > {T}| | , typical of ICRH heating, the growth rate increases, while for {T}\\perp < {T}| | , typical of neutral beam heating, the growth rate decreases.

  19. Aeronomical determinations of the quantum yields of O (1S) and O (1D) from dissociative recombination of O2(+)

    NASA Technical Reports Server (NTRS)

    Yee, Jeng-Hwa; Abreu, Vincent J.; Colwell, William B.

    1989-01-01

    Data from the visible-airglow experiment on the Atmosphere Explorer-E satellite have been used to determine the quantum yields of O (1S) and O (1D) from the dissociative recombination of O2(+) based on a constant total recombination rate from each vibrational level. A range of values between 0.05 and 0.18 has been obtained for the quantum yield of O (1S) and shows a positive correlation with the extent of the vibrational excitation of O2(+). The quantum yield of O (1D) has been measured to be 0.9 + or - 0.2, with no apparent dependence on the vibrational distribution of O2(+).

  20. What's D&T For? Gathering and Comparing the Values of Design and Technology Academics and Trainee Teachers

    ERIC Educational Resources Information Center

    Hardy, Alison

    2015-01-01

    Some who read and research about Design & Technology (D&T) would say that the concept of value is key to understanding and defining D&T. Closer inspection reveals though that there are two ways in which values are defined in D&T: how values are taught and learnt about in D&T to use them to make judgments in D&T lessons, and…

  1. Satisfactory surgical outcome of T2 gastric cancer after modified D2 lymphadenectomy.

    PubMed

    Zhang, Shupeng; Wu, Liangliang; Wang, Xiaona; Ding, Xuewei; Liang, Han

    2017-04-01

    Though D2 lymphadenectomy has been increasingly regarded as standard surgical procedure for advanced gastric cancer (GC), the modified D2 (D1 + 7, 8a and 9) lymphadenectomy may be more suitable than D2 dissection for T2 stage GC. The purpose of this study is to elucidate whether the surgical outcome of modified D2 lymphadenectomy was comparable to that of standard D2 dissection in T2 stage GC patients. A retrospective cohort study with 77 cases and 77 controls matched for baseline characteristics was conducted. Patients were categorized into two groups according to the extent of lymphadenectomy: the modified D2 group (mD2) and the standard D2 group (D2). Surgical outcome and recurrence date were compared between the two groups. The 5-year overall survival (OS) rate was 71.4% for patients accepted mD2 lymphadenectomy and 70.1% for those accepted standard D2, respectively, and the difference was not statistically significant. Multivariate survival analysis revealed that curability, tumor size, TNM stage and postoperative complications were independently prognostic factors for T2 stage GC patients. Patients in the mD2 group tended to have less intraoperative blood loss (P=0.001) and shorter operation time (P<0.001) than those in the D2 group. While there were no significant differences in recurrence rate and types, especially lymph node recurrence, between the two groups. The surgical outcome of mD2 lymphadenectomy was equal to that of standard D2, and the use of mD2 instead of standard D2 can be a better option for T2 stage GC.

  2. Regulation and gene expression profiling of NKG2D positive human cytomegalovirus-primed CD4+ T-cells.

    PubMed

    Jensen, Helle; Folkersen, Lasse; Skov, Søren

    2012-01-01

    NKG2D is a stimulatory receptor expressed by natural killer (NK) cells, CD8(+) T-cells, and γδ T-cells. NKG2D expression is normally absent from CD4(+) T-cells, however recently a subset of NKG2D(+) CD4(+) T-cells has been found, which is specific for human cytomegalovirus (HCMV). This particular subset of HCMV-specific NKG2D(+) CD4(+) T-cells possesses effector-like functions, thus resembling the subsets of NKG2D(+) CD4(+) T-cells found in other chronic inflammations. However, the precise mechanism leading to NKG2D expression on HCMV-specific CD4(+) T-cells is currently not known. In this study we used genome-wide analysis of individual genes and gene set enrichment analysis (GSEA) to investigate the gene expression profile of NKG2D(+) CD4(+) T-cells, generated from HCMV-primed CD4(+) T-cells. We show that the HCMV-primed NKG2D(+) CD4(+) T-cells possess a higher differentiated phenotype than the NKG2D(-) CD4(+) T-cells, both at the gene expression profile and cytokine profile. The ability to express NKG2D at the cell surface was primarily determined by the activation or differentiation status of the CD4(+) T-cells and not by the antigen presenting cells. We observed a correlation between CD94 and NKG2D expression in the CD4(+) T-cells following HCMV stimulation. However, knock-down of CD94 did not affect NKG2D cell surface expression or signaling. In addition, we show that NKG2D is recycled at the cell surface of activated CD4(+) T-cells, whereas it is produced de novo in resting CD4(+) T-cells. These findings provide novel information about the gene expression profile of HCMV-primed NKG2D(+) CD4(+) T-cells, as well as the mechanisms regulating NKG2D cell surface expression.

  3. Geodesic acoustic modes in noncircular cross section tokamaks

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

    Sorokina, E. A., E-mail: sorokina.ekaterina@gmail.com; Lakhin, V. P.; Konovaltseva, L. V.

    2017-03-15

    The influence of the shape of the plasma cross section on the continuous spectrum of geodesic acoustic modes (GAMs) in a tokamak is analyzed in the framework of the MHD model. An expression for the frequency of a local GAM for a model noncircular cross section plasma equilibrium is derived. Amendments to the oscillation frequency due to the plasma elongation and triangularity and finite tokamak aspect ratio are calculated. It is shown that the main factor affecting the GAM spectrum is the plasma elongation, resulting in a significant decrease in the mode frequency.

  4. Continuous high-yield production of vertically aligned carbon nanotubes on 2D and 3D substrates.

    PubMed

    Guzmán de Villoria, Roberto; Hart, A John; Wardle, Brian L

    2011-06-28

    Vertically aligned carbon nanotubes (VACNTs) have certain advantages over bulk CNT powders and randomly oriented CNT mats for applications in flexible electronic devices, filtration membranes, biosensors and multifunctional aerospace materials. Here, a machine and a process to synthesize VACNTs in a continuous manner are presented showing uniform growth on 2D and 3D substrates, including alumina fibers, silicon wafer pieces, and stainless steel foils. Aligned multiwalled carbon nanotubes (MWNT) are synthesized at substrate feed rates of up to 6.8 cm/min, and the CNTs reach up to 60 μm in length depending on residence time in the reactor. In addition to the aligned morphology indicative of high yield growth, transmission electron microscopy and Raman spectroscopy reveal that the CNTs are of comparable quality to CNTs grown via a similar batch process. A significant reduction in time, reaction products, gases, and energy is demonstrated relative to batch processing, paving the way for industrial production of VACNTs.

  5. Feedback-assisted extension of the tokamak operating space to low safety factor

    DOE PAGES

    Hanson, Jeremy M.; Bialek, James M.; Baruzzo, M.; ...

    2014-07-07

    Recent DIII-D and RFX-mod experiments have demonstrated stable tokamak operation at very low values of the edge safety factor q( a) near and below 2. The onset of n = 1 resistive wall mode (RWM) kink instabilities leads to a disruptive stability limit, encountered at q( a) = 2 (limiter plasmas) and q 95 = 2 (divertor plasmas). However, passively stable operation can be attained for q( a) and q 95 values as low as 2.2. RWM damping in the q( a) = 2 regime was measured using active MHD spectroscopy. Although consistent with theoretical predictions, the amplitude of themore » damped response does not increase significantly as the q( a) = 2 limit is approached, in contrast with damping measurements made approaching the pressure-driven RWM limit. Applying proportional gain magnetic feedback control of the n = 1 modes has resulted in stabilized operation with q 95 values reaching as low as 1.9 in DIII-D and q( a) reaching 1.55 in RFX-mod. In addition to being consistent with the q( a) = 2 external kink mode stability limit, the unstable modes have growth rates on the order of the characteristic wall eddy-current decay timescale in both devices, and a dominant m = 2 poloidal structure that is consistent with ideal MHD predictions. As a result, the experiments contribute to validating MHD stability theory and demonstrate that a key tokamak stability limit can be overcome with feedback.« less

  6. Spectral emission measurements of lithium on the lithium tokamak experiment.

    PubMed

    Gray, T K; Biewer, T M; Boyle, D P; Granstedt, E M; Kaita, R; Maingi, R; Majeski, R P

    2012-10-01

    There has been a long-standing collaboration between ORNL and PPPL on edge and boundary layer physics. As part of this collaboration, ORNL has a large role in the instrumentation and interpretation of edge physics in the lithium tokamak experiment (LTX). In particular, a charge exchange recombination spectroscopy (CHERS) diagnostic is being designed and undergoing staged testing on LTX. Here we present results of passively measured lithium emission at 5166.89 A in LTX in anticipation of active spectroscopy measurements, which will be enabled by the installation of a neutral beam in 2013. Preliminary measurements are made in transient LTX plasmas with plasma current, I(p) < 70 kA, ohmic heating power, P(oh) ∼ 0.3 MW and discharge lifetimes of 10-15 ms. Measurements are made with a short focal length spectrometer and optics similar to the CHERS diagnostics on NSTX [R. E. Bell, Rev. Sci. Instrum. 68(2), 1273-1280 (1997)]. These preliminary measurements suggest that even without the neutral beam for active spectroscopy, there is sufficient passive lithium emission to allow for line-of-sight profile measurements of ion temperature, T(i); toroidal velocity and v(t). Results show peak T(i) = 70 eV and peak v(t) = 45 km/s were reached 10 ms into the discharge.

  7. 75 FR 47893 - Proposed Collection; Comment Request for REG-111583-07, (T.D. 9405) (Final)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-09

    ...-111583-07, (T.D. 9405) (Final) AGENCY: Internal Revenue Service (IRS), Treasury. ACTION: Notice and... comments concerning temporary and final regulations (REG-111583-07) (T.D. 9405), Employment Tax Adjustments... Adjustments. OMB Number: 1545-2097. Form Number: REG-111583-07 (T.D. 9405) (final). Abstract: This document...

  8. High resolution main-ion charge exchange spectroscopy in the DIII-D H-mode pedestal.

    PubMed

    Grierson, B A; Burrell, K H; Chrystal, C; Groebner, R J; Haskey, S R; Kaplan, D H

    2016-11-01

    A new high spatial resolution main-ion (deuterium) charge-exchange spectroscopy system covering the tokamak boundary region has been installed on the DIII-D tokamak. Sixteen new edge main-ion charge-exchange recombination sightlines have been combined with nineteen impurity sightlines in a tangentially viewing geometry on the DIII-D midplane with an interleaving design that achieves 8 mm inter-channel radial resolution for detailed profiles of main-ion temperature, velocity, charge-exchange emission, and neutral beam emission. At the plasma boundary, we find a strong enhancement of the main-ion toroidal velocity that exceeds the impurity velocity by a factor of two. The unique combination of experimentally measured main-ion and impurity profiles provides a powerful quasi-neutrality constraint for reconstruction of tokamak H-mode pedestals.

  9. Regulation and Gene Expression Profiling of NKG2D Positive Human Cytomegalovirus-Primed CD4+ T-Cells

    PubMed Central

    Jensen, Helle; Folkersen, Lasse; Skov, Søren

    2012-01-01

    NKG2D is a stimulatory receptor expressed by natural killer (NK) cells, CD8+ T-cells, and γδ T-cells. NKG2D expression is normally absent from CD4+ T-cells, however recently a subset of NKG2D+ CD4+ T-cells has been found, which is specific for human cytomegalovirus (HCMV). This particular subset of HCMV-specific NKG2D+ CD4+ T-cells possesses effector-like functions, thus resembling the subsets of NKG2D+ CD4+ T-cells found in other chronic inflammations. However, the precise mechanism leading to NKG2D expression on HCMV-specific CD4+ T-cells is currently not known. In this study we used genome-wide analysis of individual genes and gene set enrichment analysis (GSEA) to investigate the gene expression profile of NKG2D+ CD4+ T-cells, generated from HCMV-primed CD4+ T-cells. We show that the HCMV-primed NKG2D+ CD4+ T-cells possess a higher differentiated phenotype than the NKG2D– CD4+ T-cells, both at the gene expression profile and cytokine profile. The ability to express NKG2D at the cell surface was primarily determined by the activation or differentiation status of the CD4+ T-cells and not by the antigen presenting cells. We observed a correlation between CD94 and NKG2D expression in the CD4+ T-cells following HCMV stimulation. However, knock-down of CD94 did not affect NKG2D cell surface expression or signaling. In addition, we show that NKG2D is recycled at the cell surface of activated CD4+ T-cells, whereas it is produced de novo in resting CD4+ T-cells. These findings provide novel information about the gene expression profile of HCMV-primed NKG2D+ CD4+ T-cells, as well as the mechanisms regulating NKG2D cell surface expression. PMID:22870231

  10. Toroidal Ampere-Faraday Equations Solved Consistently with the CQL3D Fokker-Planck Time-Evolution

    NASA Astrophysics Data System (ADS)

    Harvey, R. W.; Petrov, Yu. V.

    2013-10-01

    A self-consistent, time-dependent toroidal electric field calculation is a key feature of a complete 3D Fokker-Planck kinetic distribution radial transport code for f(v,theta,rho,t). In the present CQL3D finite-difference model, the electric field E(rho,t) is either prescribed, or iteratively adjusted to obtain prescribed toroidal or parallel currents. We discuss first results of an implementation of the Ampere-Faraday equation for the self-consistent toroidal electric field, as applied to the runaway electron production in tokamaks due to rapid reduction of the plasma temperature as occurs in a plasma disruption. Our previous results assuming a constant current density (Lenz' Law) model showed that prompt ``hot-tail runaways'' dominated ``knock-on'' and Dreicer ``drizzle'' runaways; we will examine modifications due to the more complete Ampere-Faraday solution. Work supported by US DOE under DE-FG02-ER54744.

  11. (t, n) Threshold d-Level Quantum Secret Sharing.

    PubMed

    Song, Xiu-Li; Liu, Yan-Bing; Deng, Hong-Yao; Xiao, Yong-Gang

    2017-07-25

    Most of Quantum Secret Sharing(QSS) are (n, n) threshold 2-level schemes, in which the 2-level secret cannot be reconstructed until all n shares are collected. In this paper, we propose a (t, n) threshold d-level QSS scheme, in which the d-level secret can be reconstructed only if at least t shares are collected. Compared with (n, n) threshold 2-level QSS, the proposed QSS provides better universality, flexibility, and practicability. Moreover, in this scheme, any one of the participants does not know the other participants' shares, even the trusted reconstructor Bob 1 is no exception. The transformation of the particles includes some simple operations such as d-level CNOT, Quantum Fourier Transform(QFT), Inverse Quantum Fourier Transform(IQFT), and generalized Pauli operator. The transformed particles need not to be transmitted from one participant to another in the quantum channel. Security analysis shows that the proposed scheme can resist intercept-resend attack, entangle-measure attack, collusion attack, and forgery attack. Performance comparison shows that it has lower computation and communication costs than other similar schemes when 2 < t < n - 1.

  12. The ARIES Advanced and Conservative Tokamak Power Plant Study

    DOE PAGES

    Kessel, C. E; Tillak, M. S; Najmabadi, F.; ...

    2015-12-22

    Tokamak power plants are studied with advanced and conservative design philosophies to identify the impacts on the resulting designs and to provide guidance to critical research needs. Incorporating updated physics understanding and using more sophisticated engineering and physics analysis, the tokamak configurations have developed a more credible basis compared with older studies. The advanced configuration assumes a self-cooled lead lithium blanket concept with SiC composite structural material with 58% thermal conversion efficiency. This plasma has a major radius of 6.25 m, a toroidal field of 6.0 T, a q₉₅ of 4.5, aᵦ total N of 5.75, an H98 of 1.65,more » an n/n Gr of 1.0, and a peak divertor heat flux of 13.7 MW/m² . The conservative configuration assumes a dual-coolant lead lithium blanket concept with reduced activation ferritic martensitic steel structural material and helium coolant, achieving a thermal conversion efficiency of 45%. The plasma has a major radius of 9.75 m, a toroidal field of 8.75 T, a q₉₅ of 8.0, aᵦ total N of 2.5, an H₉₈ of 1.25, an n/n Gr of 1.3, and a peak divertor heat flux of 10 MW/m² . The divertor heat flux treatment with a narrow power scrape off width has driven the plasmas to larger major radius. Edge and divertor plasma simulations are targeting a basis for high radiated power fraction in the divertor, which is necessary for solutions to keep the peak heat flux in the range 10 to 15 MW/m² . Combinations of the advanced and conservative approaches show intermediate sizes. A new systems code using a database approach has been used and shows that the operating point is really an operating zone with some range of plasma and engineering parameters and very similar costs of electricity. Other papers in this issue provide more detailed discussion of the work summarized here.« less

  13. Vitamin D Actions on CD4+ T Cells in Autoimmune Disease

    PubMed Central

    Hayes, Colleen Elizabeth; Hubler, Shane L.; Moore, Jerott R.; Barta, Lauren E.; Praska, Corinne E.; Nashold, Faye E.

    2015-01-01

    This review summarizes and integrates research on vitamin D and CD4+ T-lymphocyte biology to develop new mechanistic insights into the molecular etiology of autoimmune disease. A deep understanding of molecular mechanisms relevant to gene–environment interactions is needed to deliver etiology-based autoimmune disease prevention and treatment strategies. Evidence linking sunlight, vitamin D, and the risk of multiple sclerosis and type 1 diabetes is summarized to develop the thesis that vitamin D is the environmental factor that most strongly influences autoimmune disease development. Evidence for CD4+ T-cell involvement in autoimmune disease pathogenesis and for paracrine calcitriol signaling to CD4+ T lymphocytes is summarized to support the thesis that calcitriol is sunlight’s main protective signal transducer in autoimmune disease risk. Animal modeling and human mechanistic data are summarized to support the view that vitamin D probably influences thymic negative selection, effector Th1 and Th17 pathogenesis and responsiveness to extrinsic cell death signals, FoxP3+CD4+ T-regulatory cell and CD4+ T-regulatory cell type 1 (Tr1) cell functions, and a Th1–Tr1 switch. The proposed Th1–Tr1 switch appears to bridge two stable, self-reinforcing immune states, pro- and anti-inflammatory, each with a characteristic gene regulatory network. The bi-stable switch would enable T cells to integrate signals from pathogens, hormones, cell–cell interactions, and soluble mediators and respond in a biologically appropriate manner. Finally, unanswered questions and potentially informative future research directions are highlighted to speed delivery of etiology-based strategies to reduce autoimmune disease. PMID:25852682

  14. Equilibrium reconstruction in an iron core tokamak using a deterministic magnetisation model

    NASA Astrophysics Data System (ADS)

    Appel, L. C.; Lupelli, I.; JET Contributors

    2018-02-01

    In many tokamaks ferromagnetic material, usually referred to as an iron-core, is present in order to improve the magnetic coupling between the solenoid and the plasma. The presence of the iron core in proximity to the plasma changes the magnetic topology with consequent effects on the magnetic field structure and the plasma boundary. This paper considers the problem of obtaining the free-boundary plasma equilibrium solution in the presence of ferromagnetic material based on measured constraints. The current approach employs a model described by O'Brien et al. (1992) in which the magnetisation currents at the iron-air boundary are represented by a set of free parameters and appropriate boundary conditions are enforced via a set of quasi-measurements on the material boundary. This can lead to the possibility of overfitting the data and hiding underlying issues with the measured signals. Although the model typically achieves good fits to measured magnetic signals there are significant discrepancies in the inferred magnetic topology compared with other plasma diagnostic measurements that are independent of the magnetic field. An alternative approach for equilibrium reconstruction in iron-core tokamaks, termed the deterministic magnetisation model is developed and implemented in EFIT++. The iron is represented by a boundary current with the gradients in the magnetisation dipole state generating macroscopic internal magnetisation currents. A model for the boundary magnetisation currents at the iron-air interface is developed using B-Splines enabling continuity to arbitrary order; internal magnetisation currents are allocated to triangulated regions within the iron, and a method to enable adaptive refinement is implemented. The deterministic model has been validated by comparing it with a synthetic 2-D electromagnetic model of JET. It is established that the maximum field discrepancy is less than 1.5 mT throughout the vacuum region enclosing the plasma. The discrepancies

  15. Physics of the Tokamak Pedestal, and Implications for Magnetic Fusion Energy

    NASA Astrophysics Data System (ADS)

    Snyder, Philip

    2017-10-01

    High performance in tokamaks is achieved via the spontaneous formation of a transport barrier in the outer few percent of the confined plasma. This narrow insulating layer, referred to as a ``pedestal,'' typically results in a >30x increase in pressure across a 0.4-5cm layer. Predicted fusion power scales with the square of the pedestal top pressure (or ``pedestal height''), hence a fusion reactor strongly benefits from a high pedestal, provided this can be attained without large Edge Localized Modes (ELMs), which may erode plasma facing materials. The overlap of drift orbit, turbulence, and equilibrium scales across this narrow layer leads to rich and complex physics, and challenges traditional analytic and computational approaches. We review studies employing gyrokinetic, neoclassical, MHD, and other methods, which have explored how a range of instabilities, influenced by complex geometry, and strong ExB flows and bootstrap current, drive transport across the pedestal and guide its structure and dynamics. Development of high resolution diagnostics, and coordinated experiments on several tokamaks, have validated understanding of important aspects of the physics, while highlighting open issues. A predictive model (EPED) has proven capable of predicting the pedestal height and width to 20-25% accuracy in large statistical studies. This model was used to predict a new, high pedestal ``Super H-Mode'' regime, which was subsequently discovered on DIII-D, and motivated experiments on Alcator C-Mod which achieved world record, reactor relevant pedestal pressure. We review open issues including improved formalism, particle and momentum transport, the role of neutrals and impurities, ELM control, and pedestal formation. Finally we discuss coupling pedestal and core predictive models to enable more comprehensive optimization of the tokamak fusion concept. Supported by the US DOE under DE-FG02-95ER54309, FC02-06ER54873, DE-FC02-04ER54698, DE-FC02-99ER54512.

  16. Synthetic Microwave Imaging Reflectometry diagnostic using 3D FDTD Simulations

    NASA Astrophysics Data System (ADS)

    Kruger, Scott; Jenkins, Thomas; Smithe, David; King, Jacob; Nimrod Team Team

    2017-10-01

    Microwave Imaging Reflectometry (MIR) has become a standard diagnostic for understanding tokamak edge perturbations, including the edge harmonic oscillations in QH mode operation. These long-wavelength perturbations are larger than the normal turbulent fluctuation levels and thus normal analysis of synthetic signals become more difficult. To investigate, we construct a synthetic MIR diagnostic for exploring density fluctuation amplitudes in the tokamak plasma edge by using the three-dimensional, full-wave FDTD code Vorpal. The source microwave beam for the diagnostic is generated and refelected at the cutoff surface that is distorted by 2D density fluctuations in the edge plasma. Synthetic imaging optics at the detector can be used to understand the fluctuation and background density profiles. We apply the diagnostic to understand the fluctuations in edge plasma density during QH-mode activity in the DIII-D tokamak, as modeled by the NIMROD code. This work was funded under DOE Grant Number DE-FC02-08ER54972.

  17. Experimental Investigation of Muon-Catalyzed d-t Fusion

    NASA Astrophysics Data System (ADS)

    Jones, S. E.; Anderson, A. N.; Caffrey, A. J.; Walter, J. B.; Watts, K. D.; Bradbury, J. N.; Gram, P. A. M.; Leon, M.; Maltrud, H. R.; Paciotti, M. A.

    1983-11-01

    Measurements of the absolute neutron yield and the time dependence of the appearance of neutrons resulting from muon-catalyzed fusion have been carried out in high-density deuterium-tritium mixtures. The temperature dependence of the resonant dtμ-molecular formation process has been determined in the range 100 to 540 K. Mesomolecular formation is found to be resonant for DT as well as D2 target molecules. The sticking probability and other fundamental parameters have been measured for the first time.

  18. ECRH Studies on Tokamak Plasmas.

    DTIC Science & Technology

    1980-10-10

    r.I*cru.Dtrtibution uUnliited 300 Unicorn Pork Drive Woburn, Massachusetts 04801 ECRH STUDIES ON TOKAMAK PLASMAS JAYCOR Project No. 6183 Final Report...up techniques now in use or being suggested, include growing the plasma from a small minor radius or applying a negative voltage spike immediately

  19. Scrape-off layer tokamak plasma turbulence

    NASA Astrophysics Data System (ADS)

    Bisai, N.; Singh, R.; Kaw, P. K.

    2012-05-01

    Two-dimensional (2D) interchange turbulence in the scrape-off layer of tokamak plasmas and their subsequent contribution to anomalous plasma transport has been studied in recent years using electron continuity, current balance, and electron energy equations. In this paper, numerically it is demonstrated that the inclusion of ion energy equation in the simulation changes the nature of plasma turbulence. Finite ion temperature reduces floating potential by about 15% compared with the cold ion temperature approximation and also reduces the radial electric field. Rotation of plasma blobs at an angular velocity about 1.5×105 rad/s has been observed. It is found that blob rotation keeps plasma blob charge separation at an angular position with respect to the vertical direction that gives a generation of radial electric field. Plasma blobs with high electron temperature gradients can align the charge separation almost in the radial direction. Influence of high ion temperature and its gradient has been presented.

  20. A controlled comparison of the BacT/ALERT® 3D and VIRTUO™ microbial detection systems.

    PubMed

    Totty, H; Ullery, M; Spontak, J; Viray, J; Adamik, M; Katzin, B; Dunne, W M; Deol, P

    2017-10-01

    The performance of the next-generation BacT/ALERT® VIRTUO™ Microbial Detection System (VIRTUO™, bioMérieux Inc., Hazelwood, MO) was compared to the BacT/ALERT® 3D Microbial Detection System (3D, bioMérieux Inc., Durham, NC) using BacT/ALERT® FA Plus (FA Plus), BacT/ALERT® PF Plus (PF Plus), BacT/ALERT® FN Plus (FN Plus), BacT/ALERT® Standard Aerobic (SA), and BacT/ALERT® Standard Anaerobic (SN) blood culture bottles (bioMérieux Inc., Durham, NC). A seeded limit of detection (LoD) study was performed for each bottle type in both systems. The LoD studies demonstrated that both systems were capable of detecting organisms at nearly identical levels [<10 colony-forming units (CFU) per bottle], with no significant difference. Following LoD determination, a seeded study was performed to compare the time to detection (TTD) between the systems using a panel of clinically relevant microorganisms inoculated at or near the LoD with 0, 4, or 10 mL of healthy human blood. VIRTUO™ exhibited a faster TTD by an average of 3.5 h, as well as demonstrated a significantly improved detection rate of 99.9% compared to 98.8% with 3D (p-value <0.05).

  1. Gint2D-T2 correlation NMR of porous media

    NASA Astrophysics Data System (ADS)

    Zhang, Yan; Blümich, Bernhard

    2015-03-01

    The internal magnetic field gradient induced in porous media by magnetic susceptibility differences at material interfaces impacts diffusion measurements in particular at high magnetic field and can be used to probe the pore structure. Insight about the relationship between pore space and internal gradient Gint can be obtained from 2D Laplace NMR experiments. When measuring distributions of transverse relaxation times T2 in fluid filled porous media, relaxation and diffusion in internal gradients arise simultaneously and data are often interpreted with the assumption that one or the other parameter be constant throughout the sample. To examine this assumption we measure correlations of the distributions of Gint2D and T2 by 2D Laplace NMR for three different kinds of samples, glass beads with different bead diameters saturated with water, glass beads filled with oil and water, and a wet mortar sample. For the first two samples the cases where either the internal gradient or diffusion dominates were examined separately in order to better understand the relationship between Gint and D. These results are useful for assessing the impact of internal gradients and diffusion in unknown samples, such as the mortar sample. The experiments were performed at different magnetic field strengths corresponding to 300 MHz and 700 MHz 1H Larmor frequency to identify the impact of the magnetic field on the internal gradient. Subsequently, spatially resolved Gint2D-T2 maps were obtained to study the sample heterogeneity.

  2. Quasistationary Plasma Predator-Prey System of Coupled Turbulence, Drive, and Sheared E ×B Flow During High Performance DIII-D Tokamak Discharges

    NASA Astrophysics Data System (ADS)

    Barada, K.; Rhodes, T. L.; Burrell, K. H.; Zeng, L.; Bardóczi, L.; Chen, Xi; Muscatello, C. M.; Peebles, W. A.

    2018-03-01

    A new, long-lived limit cycle oscillation (LCO) regime has been observed in the edge of near zero torque high performance DIII-D tokamak plasma discharges. These LCOs are localized and composed of density turbulence, gradient drives, and E ×B velocity shear damping (E and B are the local radial electric and total magnetic fields). Density turbulence sequentially acts as a predator (via turbulence transport) of profile gradients and a prey (via shear suppression) to the E ×B velocity shear. Reported here for the first time is a unique spatiotemporal variation of the local E ×B velocity, which is found to be essential for the existence of this system. The LCO system is quasistationary, existing from 3 to 12 plasma energy confinement times (˜30 - 900 LCO cycles) limited by hardware constraints. This plasma system appears to contribute strongly to the edge transport in these high performance and transient-free plasmas, as evident from oscillations in transport relevant edge parameters at LCO time scale.

  3. MRI of the lumbar spine: comparison of 3D isotropic turbo spin-echo SPACE sequence versus conventional 2D sequences at 3.0 T.

    PubMed

    Lee, Sungwon; Jee, Won-Hee; Jung, Joon-Yong; Lee, So-Yeon; Ryu, Kyeung-Sik; Ha, Kee-Yong

    2015-02-01

    Three-dimensional (3D) fast spin-echo sequence with variable flip-angle refocusing pulse allows retrospective alignments of magnetic resonance imaging (MRI) in any desired plane. To compare isotropic 3D T2-weighted (T2W) turbo spin-echo sequence (TSE-SPACE) with standard two-dimensional (2D) T2W TSE imaging for evaluating lumbar spine pathology at 3.0 T MRI. Forty-two patients who had spine surgery for disk herniation and had 3.0 T spine MRI were included in this study. In addition to standard 2D T2W TSE imaging, sagittal 3D T2W TSE-SPACE was obtained to produce multiplanar (MPR) images. Each set of MR images from 3D T2W TSE and 2D TSE-SPACE were independently scored for the degree of lumbar neural foraminal stenosis, central spinal stenosis, and nerve compression by two reviewers. These scores were compared with operative findings and the sensitivities were evaluated by McNemar test. Inter-observer agreements and the correlation with symptoms laterality were assessed with kappa statistics. The 3D T2W TSE and 2D TSE-SPACE had similar sensitivity in detecting foraminal stenosis (78.9% versus 78.9% in 32 foramen levels), spinal stenosis (100% versus 100% in 42 spinal levels), and nerve compression (92.9% versus 81.8% in 59 spinal nerves). The inter-observer agreements (κ = 0.849 vs. 0.451 for foraminal stenosis, κ = 0.809 vs. 0.503 for spinal stenosis, and κ = 0.681 vs. 0.429 for nerve compression) and symptoms correlation (κ = 0.449 vs. κ = 0.242) were better in 3D TSE-SPACE compared to 2D TSE. 3D TSE-SPACE with oblique coronal MPR images demonstrated better inter-observer agreements compared to 3D TSE-SPACE without oblique coronal MPR images (κ = 0.930 vs. κ = 0.681). Isotropic 3D T2W TSE-SPACE at 3.0 T was comparable to 2D T2W TSE for detecting foraminal stenosis, central spinal stenosis, and nerve compression with better inter-observer agreements and symptom correlation. © The Foundation Acta Radiologica 2014 Reprints and

  4. Production of D-lactic acid in a continuous membrane integrated fermentation reactor by genetically modified Saccharomyces cerevisiae: enhancement in D-lactic acid carbon yield.

    PubMed

    Mimitsuka, Takashi; Sawai, Kenji; Kobayashi, Koji; Tsukada, Takeshi; Takeuchi, Norihiro; Yamada, Katsushige; Ogino, Hiroyasu; Yonehara, Tetsu

    2015-01-01

    Poly d-lactic acid is an important polymer because it improves the thermostability of poly l-lactic acid by stereo complex formation. To demonstrate potency of continuous fermentation using a membrane-integrated fermentation reactor (MFR) system, continuous fermentation using genetically modified Saccharomyces cerevisiae which produces d-lactic acid was performed at the low pH and microaerobic conditions. d-Lactic acid continuous fermentation using the MFR system by genetically modified yeast increased production rate by 11-fold compared with batch fermentation. In addition, the carbon yield of d-lactic acid in continuous fermentation was improved to 74.6 ± 2.3% compared to 39.0 ± 1.7% with batch fermentation. This dramatic improvement in carbon yield could not be explained by a reduction in carbon consumption to form cells compared to batch fermentation. Further detailed analysis at batch fermentation revealed that the carbon yield increased to 76.8% at late stationary phase. S. cerevisiae, which exhibits the Crabtree-positive effect, demonstrated significant changes in metabolic activities at low sugar concentrations (Rossignol et al., Yeast, 20, 1369-1385, 2003). Moreover, lactate-producing S. cerevisiae requires ATP supplied not only from the glycolytic pathway but also from the TCA cycle (van Maris et al., Appl. Environ. Microbiol., 70, 2898-2905, 2004). Our finding was revealed that continuous fermentation, which can maintain the conditions of both a low sugar concentration and air supply, results in Crabtree-positive and lactate-producing S. cerevisiae for suitable conditions of d-lactic acid production with respect to redox balance and ATP generation because of releasing the yeast from the Crabtree effect. Copyright © 2014 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  5. An adapted yield criterion for the evolution of subsequent yield surfaces

    NASA Astrophysics Data System (ADS)

    Küsters, N.; Brosius, A.

    2017-09-01

    In numerical analysis of sheet metal forming processes, the anisotropic material behaviour is often modelled with isotropic work hardening and an average Lankford coefficient. In contrast, experimental observations show an evolution of the Lankford coefficients, which can be associated with a yield surface change due to kinematic and distortional hardening. Commonly, extensive efforts are carried out to describe these phenomena. In this paper an isotropic material model based on the Yld2000-2d criterion is adapted with an evolving yield exponent in order to change the yield surface shape. The yield exponent is linked to the accumulative plastic strain. This change has the effect of a rotating yield surface normal. As the normal is directly related to the Lankford coefficient, the change can be used to model the evolution of the Lankford coefficient during yielding. The paper will focus on the numerical implementation of the adapted material model for the FE-code LS-Dyna, mpi-version R7.1.2-d. A recently introduced identification scheme [1] is used to obtain the parameters for the evolving yield surface and will be briefly described for the proposed model. The suitability for numerical analysis will be discussed for deep drawing processes in general. Efforts for material characterization and modelling will be compared to other common yield surface descriptions. Besides experimental efforts and achieved accuracy, the potential of flexibility in material models and the risk of ambiguity during identification are of major interest in this paper.

  6. Compatibility of internal transport barrier with steady-state operation in the high bootstrap fraction regime on DIII-D

    DOE PAGES

    Garofalo, Andrea M.; Gong, Xianzu; Grierson, Brian A.; ...

    2015-11-16

    Recent EAST/DIII-D joint experiments on the high poloidal beta tokamak regime in DIII-D have demonstrated fully noninductive operation with an internal transport barrier (ITB) at large minor radius, at normalized fusion performance increased by ≥30% relative to earlier work. The advancement was enabled by improved understanding of the “relaxation oscillations”, previously attributed to repetitive ITB collapses, and of the fast ion behavior in this regime. It was found that the “relaxation oscillations” are coupled core-edge modes 2 amenable to wall-stabilization, and that fast ion losses which previously dictated a large plasma-wall separation to avoid wall over-heating, can be reduced tomore » classical levels with sufficient plasma density. By using optimized waveforms of the plasma-wall separation and plasma density, fully noninductive plasmas have been sustained for long durations with excellent energy confinement quality, bootstrap fraction ≥ 80%, β N ≤ 4 , β P ≥ 3 , and β T ≥ 2%. Finally, these results bolster the applicability of the high poloidal beta tokamak regime toward the realization of a steady-state fusion reactor.« less

  7. Numerical modelling of geodesic acoustic mode relaxation in a tokamak edge

    DOE PAGES

    Dorf, M. A.; Cohen, R. H.; Dorr, M.; ...

    2013-05-08

    Here, the edge of a tokamak in a high confinement (H mode) regime is characterized by steep density gradients and a large radial electric field. Recent analytical studies demonstrated that the presence of a strong radial electric field consistent with a subsonic pedestal equilibrium modifies the conventional results of the neoclassical formalism developed for the core region. In the present work we make use of the recently developed gyrokinetic code COGENT to numerically investigate neoclassical transport in a tokamak edge including the effects of a strong radial electric field. The results of numerical simulations are found to be in goodmore » qualitative agreement with the theoretical predictions and the quantitative discrepancy is discussed. In addition, the present work investigates the effects of a strong radial electric field on the relaxation of geodesic acoustic modes (GAMs) in a tokamak edge. Numerical simulations demonstrate that the presence of a strong radial electric field characteristic of a tokamak pedestal can enhance the GAM decay rate, and heuristic arguments elucidating this finding are provided.« less

  8. Stavudine (d4T) concentrations in women receiving post-partum antiretroviral treatment and their breastfeeding infants

    PubMed Central

    Fogel, Jessica M.; Taha, Taha E.; Sun, Jin; Hoover, Donald R.; Parsons, Teresa L.; Kumwenda, Johnstone J.; Mofenson, Lynne M.; Fowler, Mary Glenn; Hendrix, Craig W.; Kumwenda, Newton I.; Eshleman, Susan H.; Mirochnick, Mark

    2012-01-01

    First-line antiretroviral treatment regimens in resource-limited settings used in breastfeeding mothers often include stavudine (d4T). Limited data describing d4T concentrations in breast milk are available. We analyzed d4T concentrations in 52 mother-infant pairs using ultra-performance liquid chromatography-tandem mass spectrometry (lower limit of quantification: 5 ng/ml in plasma, 20 ng/ml in breast milk). Median (interquartile range) d4T concentrations were 86 (36–191) ng/ml in maternal plasma, 151 (48–259) ng/ml in whole milk, 190 (58–296) ng/ml in skim milk, and <5 (<5-<5) ng/ml in infant plasma. While d4T is concentrated in breast milk relative to maternal plasma, the infant d4T dose received from breast milk is very small and not clinically significant. PMID:22614899

  9. Involvement of Semaphorin (Sema4D) in T-Dependent Activation of B Cells.

    PubMed

    Kuklina, Е М; Nekrasova, I V; Valieva, Yu V

    2017-08-01

    The involvement of endogenous semaphorin (Sema4D) into the key stage of T-dependent differentiation of B cells, formation of plasmoblasts, was demonstrated in vitro in T/B cell co-culture under conditions of polyclonal activation of T cells. The effect of semaphorin was not associated with activation of high-affinity Sema4D receptor plexin B1, but involves lowaffinity receptor CD72. These data indicate that Sema4D-dependent signal regulates not only the initial stage of B-cell activation, proliferative response to the antigen, but also further differentiation of B cells into plasma cells.

  10. Quasistationary Plasma Predator-Prey System of Coupled Turbulence, Drive, and Sheared E × B Flow During High Performance DIII-D Tokamak Discharges [A New, Quasi-stationary Plasma Predator-Prey System of Coupled Turbulence, Drive, and Sheared E × B Flow During High Performance DIII-D Tokamak Discharges

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

    Barada, Kshitish; Rhodes, Terry L.; Burrell, Keith H.

    A new, long-lived limit cycle oscillation (LCO) regime has been observed in the edge of near zero torque high-performance DIII-D tokamak plasma discharges. These LCOs are localized and comprised of density turbulence, gradient drives, and E X B velocity shear damping ( E and B are the local radial electric and total magnetic fields). Density turbulence sequentially acts as a predator (via turbulence transport) of profile gradients and a prey (via shear suppression) to the E X B velocity shear. Reported here for the first time, a unique spatiotemporal variation of the local E X B velocity which is foundmore » to be essential for the existence of this system. The LCO system is quasi-stationary, existing from 3 to 12 plasma energy confinement times (~30 to 900 LCO cycles) limited by hardware constraints. In conclusion, this plasma system appears to contribute strongly to the edge transport in these high-performance and transient-free plasmas as evident from oscillations in transport relevant edge parameters at LCO timescale.« less

  11. Quasistationary Plasma Predator-Prey System of Coupled Turbulence, Drive, and Sheared E × B Flow During High Performance DIII-D Tokamak Discharges [A New, Quasi-stationary Plasma Predator-Prey System of Coupled Turbulence, Drive, and Sheared E × B Flow During High Performance DIII-D Tokamak Discharges

    DOE PAGES

    Barada, Kshitish; Rhodes, Terry L.; Burrell, Keith H.; ...

    2018-03-27

    A new, long-lived limit cycle oscillation (LCO) regime has been observed in the edge of near zero torque high-performance DIII-D tokamak plasma discharges. These LCOs are localized and comprised of density turbulence, gradient drives, and E X B velocity shear damping ( E and B are the local radial electric and total magnetic fields). Density turbulence sequentially acts as a predator (via turbulence transport) of profile gradients and a prey (via shear suppression) to the E X B velocity shear. Reported here for the first time, a unique spatiotemporal variation of the local E X B velocity which is foundmore » to be essential for the existence of this system. The LCO system is quasi-stationary, existing from 3 to 12 plasma energy confinement times (~30 to 900 LCO cycles) limited by hardware constraints. In conclusion, this plasma system appears to contribute strongly to the edge transport in these high-performance and transient-free plasmas as evident from oscillations in transport relevant edge parameters at LCO timescale.« less

  12. Numerical Investigation of T-joints with 3D Four Directional Braided Composite Fillers Under Tensile Loading

    NASA Astrophysics Data System (ADS)

    Li, Xiao-kang; Liu, Zhen-guo; Hu, Long; Wang, Yi-bo; Lei, Bing; Huang, Xiang

    2017-02-01

    Numerical studied on T-joints with three-dimensional four directional (3D4D) braided composite fillers was presented in this article. Compared with conventional unidirectional prepreg fillers, the 3D braided composite fillers have excellent ability to prevent crack from penetrating trigone fillers, which constantly occurred in the conventional fillers. Meanwhile, the 3D braided composite fillers had higher fiber volume fraction and eliminated the fiber folding problem in unidirectional prepreg fillers. The braiding technology and mechanical performance of 3D4D braided fillers were studied. The numerical model of carbon fiber T-joints with 3D4D braided composite fillers was built by finite element analysis software. The damage formation, extension and failing process of T-joints with 3D4D braided fillers under tensile load were investigated. Further investigation was extended to the effect of 3D4D braided fillers with different braiding angles on mechanical behavior of the T-joints. The study results revealed that the filling area was the weakest part of the T-joints where the damage first appeared and the crack then rapidly spread to the glue film around the filling area and the interface between over-laminate and soleplate. The 3D4D braided fillers were undamaged and the braiding angle change induced a little effect on the bearing capacity of T-joints.

  13. The symmetric quartic map for trajectories of magnetic field lines in elongated divertor tokamak plasmas

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

    Jones, Morgin; Wadi, Hasina; Ali, Halima

    The coordinates of the area-preserving map equations for integration of magnetic field line trajectories in divertor tokamaks can be any coordinates for which a transformation to ({psi}{sub t},{theta},{phi}) coordinates exists [A. Punjabi, H. Ali, T. Evans, and A. Boozer, Phys. Lett. A 364, 140 (2007)]. {psi}{sub t} is toroidal magnetic flux, {theta} is poloidal angle, and {phi} is toroidal angle. This freedom is exploited to construct the symmetric quartic map such that the only parameter that determines magnetic geometry is the elongation of the separatrix surface. The poloidal flux inside the separatrix, the safety factor as a function of normalizedmore » minor radius, and the magnetic perturbation from the symplectic discretization are all held constant, and only the elongation is {kappa} varied. The width of stochastic layer, the area, and the fractal dimension of the magnetic footprint and the average radial diffusion coefficient of magnetic field lines from the stochastic layer; and how these quantities scale with {kappa} is calculated. The symmetric quartic map gives the correct scalings which are consistent with the scalings of coordinates with {kappa}. The effects of m=1, n={+-}1 internal perturbation with the amplitude that is expected to occur in tokamaks are calculated by adding a term [H. Ali, A. Punjabi, A. H. Boozer, and T. Evans, Phys. Plasmas 11, 1908 (2004)] to the symmetric quartic map. In this case, the width of stochastic layer scales as 0.35 power of {kappa}. The area of the footprint is roughly constant. The average radial diffusion coefficient of field lines near the X-point scales linearly with {kappa}. The low mn perturbation changes the quasisymmetric structure of the footprint, and reorganizes it into a single, large scale, asymmetric structure. The symmetric quartic map is combined with the dipole map [A. Punjabi, H. Ali, and A. H. Boozer, Phys. Plasmas 10, 3992 (2003)] to calculate the effects of magnetic perturbation from a current

  14. High resolution main-ion charge exchange spectroscopy in the DIII-D H-mode pedestal

    DOE PAGES

    Grierson, B. A.; Burrell, K. H.; Chrystal, C.; ...

    2016-09-12

    A new high spatial resolution main-ion (deuterium) charge-exchange spectroscopy system covering the tokamak boundary region has been installed on the DIII-D tokamak. Sixteen new edge main-ion charge-exchange recombination sightlines have been combined with nineteen impurity sightlines in a tangentially viewing geometry on the DIII-D midplane with an interleaving design that achieves 8 mm inter-channel radial resolution for detailed profiles of main-ion temperature, velocity, charge-exchange emission, and neutral beam emission. At the plasma boundary, we find a strong enhancement of the main-ion toroidal velocity that exceeds the impurity velocity by a factor of two. Furthermore, the unique combination of experimentally measuredmore » main-ion and impurity profiles provides a powerful quasi-neutrality constraint for reconstruction of tokamak H-mode pedestals.« less

  15. The build-up of energetic electrons triggering electron cyclotron emission bursts due to a magnetohydrodynamic mode at the edge of tokamaks

    DOE PAGES

    Li, Erzhong; Austin, Max E.; White, R. B.; ...

    2017-08-21

    Intense bursts of electron cyclotron emission (ECE) triggered by magnetohydrodynamic (MHD) instabilities such as edge localized modes (ELMs) have been observed on many tokamaks. On the DIII-D tokamak, it is found that an MHD mode is observed to trigger the ECE bursts in the low collisionality regime at the plasma edge. ORBIT-code simulations have shown that energetic electrons build up due to an interaction between barely trapped electrons with an MHD mode (f = 50 kHz for current case). The energetic tail of the electron distribution function develops a bump within several microseconds for this collisionless case. This behavior dependsmore » on the competition between the perturbing MHD mode and slowing down and pitch angle scattering due to collisions. As a result, for typical DIII-D parameters, the calculated ECE radiation transport predicted by ORBIT is in excellent agreement with ECE measurements, clarifying the electron dynamics of the ECE bursts for the first time.« less

  16. Spatio-temporal interpolation of soil moisture in 3D+T using automated sensor network data

    NASA Astrophysics Data System (ADS)

    Gasch, C.; Hengl, T.; Magney, T. S.; Brown, D. J.; Gräler, B.

    2014-12-01

    Soil sensor networks provide frequent in situ measurements of dynamic soil properties at fixed locations, producing data in 2- or 3-dimensions and through time (2D+T and 3D+T). Spatio-temporal interpolation of 3D+T point data produces continuous estimates that can then be used for prediction at unsampled times and locations, as input for process models, and can simply aid in visualization of properties through space and time. Regression-kriging with 3D and 2D+T data has successfully been implemented, but currently the field of geostatistics lacks an analytical framework for modeling 3D+T data. Our objective is to develop robust 3D+T models for mapping dynamic soil data that has been collected with high spatial and temporal resolution. For this analysis, we use data collected from a sensor network installed on the R.J. Cook Agronomy Farm (CAF), a 37-ha Long-Term Agro-Ecosystem Research (LTAR) site in Pullman, WA. For five years, the sensors have collected hourly measurements of soil volumetric water content at 42 locations and five depths. The CAF dataset also includes a digital elevation model and derivatives, a soil unit description map, crop rotations, electromagnetic induction surveys, daily meteorological data, and seasonal satellite imagery. The soil-water sensor data, combined with the spatial and temporal covariates, provide an ideal dataset for developing 3D+T models. The presentation will include preliminary results and address main implementation strategies.

  17. Impedance of an intense plasma-cathode electron source for tokamak startup

    DOE PAGES

    Hinson, Edward Thomas; Barr, Jayson L.; Bongard, Michael W.; ...

    2016-05-31

    In this study, an impedance model is formulated and tested for the ~1kV, ~1kA/cm 2, arc-plasma cathode electron source used for local helicity injection tokamak startup. A double layer sheath is established between the high-density arc plasma (n arc ≈ 10 21 m -3) within the electron source, and the less dense external tokamak edge plasma (n edge ≈ 10 18 m -3) into which current is injected at the applied injector voltage, V inj. Experiments on the Pegasus spherical tokamak show the injected current, I inj, increases with V inj according to the standard double layer scaling I injmore » ~ V inj 3/2 at low current and transitions to I inj ~ V inj 1/2 at high currents. In this high current regime, sheath expansion and/or space charge neutralization impose limits on the beam density n b ~ I inj/V inj 1/2. For low tokamak edge density n edge and high I inj, the inferred beam density n b is consistent with the requirement n b ≤ n edge imposed by space-charge neutralization of the beam in the tokamak edge plasma. At sufficient edge density, n b ~ n arc is observed, consistent with a limit to n b imposed by expansion of the double layer sheath. These results suggest that n arc is a viable control actuator for the source impedance.« less

  18. Filterscope diagnostic system on the Experimental Advanced Superconducting Tokamak (EAST)

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

    Xu, Z.; Wu, C. R.; Yao, X. J.

    2016-11-15

    A filterscope diagnostic system has been mounted to observe the line emission and visible bremsstrahlung emission from plasma on the experimental advanced superconducting tokamak during the 2014 campaign. By this diagnostic system, multiple wavelengths including D{sub α} (656.1 nm), D{sub γ} (433.9 nm), He II (468.5 nm), Li I (670.8 nm), Li II (548.3 nm), C III (465.0 nm), O II (441.5 nm), Mo I (386.4 nm), W I (400.9 nm), and visible bremsstrahlung radiation (538.0 nm) are monitored with corresponding wavelength filters. All these multi-channel signals are digitized at up to 200 kHz simultaneously. This diagnostic plays a crucialmore » role in studying edge localized modes and H-mode plasmas, due to the high temporal resolution and spatial resolution that have been designed into it.« less

  19. Proresolving lipid mediators resolvin D1, resolvin D2, and maresin 1 are critical in modulating T cell responses.

    PubMed

    Chiurchiù, Valerio; Leuti, Alessandro; Dalli, Jesmond; Jacobsson, Anders; Battistini, Luca; Maccarrone, Mauro; Serhan, Charles N

    2016-08-24

    Resolution of inflammation is a finely regulated process mediated by specialized proresolving lipid mediators (SPMs), including docosahexaenoic acid (DHA)-derived resolvins and maresins. The immunomodulatory role of SPMs in adaptive immune cells is of interest. We report that D-series resolvins (resolvin D1 and resolvin D2) and maresin 1 modulate adaptive immune responses in human peripheral blood lymphocytes. These lipid mediators reduce cytokine production by activated CD8(+) T cells and CD4(+) T helper 1 (TH1) and TH17 cells but do not modulate T cell inhibitory receptors or abrogate their capacity to proliferate. Moreover, these SPMs prevented naïve CD4(+) T cell differentiation into TH1 and TH17 by down-regulating their signature transcription factors, T-bet and Rorc, in a mechanism mediated by the GPR32 and ALX/FPR2 receptors; they concomitantly enhanced de novo generation and function of Foxp3(+) regulatory T (Treg) cells via the GPR32 receptor. These results were also supported in vivo in a mouse deficient for DHA synthesis (Elovl2(-/-)) that showed an increase in TH1/TH17 cells and a decrease in Treg cells compared to wild-type mice. Additionally, either DHA supplementation in Elovl2(-/-) mice or in vivo administration of resolvin D1 significantly reduced cytokine production upon specific stimulation of T cells. These findings demonstrate actions of specific SPMs on adaptive immunity and provide a new avenue for SPM-based approaches to modulate chronic inflammation. Copyright © 2016, American Association for the Advancement of Science.

  20. Zr-92(d,p)Zr-93 and Zr-92(d,t)Zr-91

    NASA Technical Reports Server (NTRS)

    Baron, N.; Fink, C. L.; Christensen, P. R.; Nickels, J.; Torsteinsen, T.

    1972-01-01

    The structures of Zr-93 and Zr-91 were studied by the stripping reaction Zr-92(d,p)Zr-93 and the pick-up reaction Zr-92(d,t)Zr-91 using 13 MeV incident deuterons. The reaction product particles were detected by counter telescope. Typical spectra from the reactions were analyzed by a nonlinear least squares peak fitting program which included a background search. Spin and parity assignments to observed excited levels were made by comparing experimental angular distributions with distorted wave Born approximation calculations.