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Sample records for advanced tokamak plasma

  1. Development in Diagnostics Application to Control Advanced Tokamak Plasma

    SciTech Connect

    Koide, Y.

    2008-03-12

    For continuous operation expected in DEMO, all the plasma current must be non-inductively driven, with self-generated neoclassical bootstrap current being maximized. The control of such steady state high performance tokamak plasma (so-called 'Advanced Tokamak Plasma') is a challenge because of the strong coupling between the current density, the pressure profile and MHD stability. In considering diagnostic needs for the advanced tokamak research, diagnostics for MHD are the most fundamental, since discharges which violate the MHD stability criteria either disrupt or have significantly reduced confinement. This report deals with the development in diagnostic application to control advanced tokamak plasma, with emphasized on recent progress in active feedback control of the current profile and the pressure profile under DEMO-relevant high bootstrap-current fraction. In addition, issues in application of the present-day actuators and diagnostics for the advanced control to DEMO will be briefly addressed, where port space for the advanced control may be limited so as to keep sufficient tritium breeding ratio (TBR)

  2. Shape Optimization for DIII-D Advanced Tokamak Plasmas

    SciTech Connect

    C.E. Kesse; J.R. Ferron; C.M. Greenfield; J.E. Menard; T.S. Taylor

    2003-07-30

    The advanced tokamak program on DIII-D is targeting the full integration of high-beta and high-bootstrap/noninductive current fraction for long-pulse lengths and the high confinement consistent with these features. Central to achieving these simultaneously is access to the highest ideal beta limits possible to maximize the headroom for experimental operation with RWM control. A study of the ideal-MHD stability is done for plasmas modeled after DIII-D advanced tokamak plasmas, varying the plasma elongation, triangularity, and outboard squareness. The highest beta(sub)N limits reach 6-7 for the n=1 kink mode for all elongation, outer squareness values, and plasma triangularity equals 0.8.

  3. Probe diagnostics in the far scrape-off layer plasma of Korea Superconducting Tokamak Advanced Research tokamak using a sideband harmonic method

    SciTech Connect

    Kim, Dong-Hwan; Hong, Suk-Ho; Park, Il-Seo; Lee, Hyo-Chang; Kang, Hyun-Ju; Chung, Chin-Wook

    2015-12-15

    Plasma characteristics in the far scrape-off layer region of tokamak play a crucial role in the stable plasma operation and its sustainability. Due to the huge facility, electrical diagnostic systems to measure plasma properties have extremely long cable length resulting in large stray current. To overcome this problem, a sideband harmonic method was applied to the Korea Superconducting Tokamak Advanced Research tokamak plasma. The sideband method allows the measurement of the electron temperature and the plasma density without the effect of the stray current. The measured plasma densities are compared with those from the interferometer, and the results show reliability of the method.

  4. Probe diagnostics in the far scrape-off layer plasma of Korea Superconducting Tokamak Advanced Research tokamak using a sideband harmonic method

    NASA Astrophysics Data System (ADS)

    Kim, Dong-Hwan; Hong, Suk-Ho; Park, Il-Seo; Lee, Hyo-Chang; Kang, Hyun-Ju; Chung, Chin-Wook

    2015-12-01

    Plasma characteristics in the far scrape-off layer region of tokamak play a crucial role in the stable plasma operation and its sustainability. Due to the huge facility, electrical diagnostic systems to measure plasma properties have extremely long cable length resulting in large stray current. To overcome this problem, a sideband harmonic method was applied to the Korea Superconducting Tokamak Advanced Research tokamak plasma. The sideband method allows the measurement of the electron temperature and the plasma density without the effect of the stray current. The measured plasma densities are compared with those from the interferometer, and the results show reliability of the method.

  5. Probe diagnostics in the far scrape-off layer plasma of Korea Superconducting Tokamak Advanced Research tokamak using a sideband harmonic method.

    PubMed

    Kim, Dong-Hwan; Hong, Suk-Ho; Park, Il-Seo; Lee, Hyo-Chang; Kang, Hyun-Ju; Chung, Chin-Wook

    2015-12-01

    Plasma characteristics in the far scrape-off layer region of tokamak play a crucial role in the stable plasma operation and its sustainability. Due to the huge facility, electrical diagnostic systems to measure plasma properties have extremely long cable length resulting in large stray current. To overcome this problem, a sideband harmonic method was applied to the Korea Superconducting Tokamak Advanced Research tokamak plasma. The sideband method allows the measurement of the electron temperature and the plasma density without the effect of the stray current. The measured plasma densities are compared with those from the interferometer, and the results show reliability of the method.

  6. Probe diagnostics in the far scrape-off layer plasma of Korea Superconducting Tokamak Advanced Research tokamak using a sideband harmonic method.

    PubMed

    Kim, Dong-Hwan; Hong, Suk-Ho; Park, Il-Seo; Lee, Hyo-Chang; Kang, Hyun-Ju; Chung, Chin-Wook

    2015-12-01

    Plasma characteristics in the far scrape-off layer region of tokamak play a crucial role in the stable plasma operation and its sustainability. Due to the huge facility, electrical diagnostic systems to measure plasma properties have extremely long cable length resulting in large stray current. To overcome this problem, a sideband harmonic method was applied to the Korea Superconducting Tokamak Advanced Research tokamak plasma. The sideband method allows the measurement of the electron temperature and the plasma density without the effect of the stray current. The measured plasma densities are compared with those from the interferometer, and the results show reliability of the method. PMID:26724028

  7. Analysis of line integrated electron density using plasma position data on Korea Superconducting Tokamak Advanced Research

    SciTech Connect

    Nam, Y. U.; Chung, J.

    2010-10-15

    A 280 GHz single-channel horizontal millimeter-wave interferometer system has been installed for plasma electron density measurements on the Korea Superconducting Tokamak Advanced Research (KSTAR) device. This system has a triangular beam path that does not pass through the plasma axis due to geometrical constraints in the superconducting tokamak. The term line density on KSTAR has a different meaning from the line density of other tokamaks. To estimate the peak density and the mean density from the measured line density, information on the position of the plasma is needed. The information has been calculated from tangentially viewed visible images using the toroidal symmetry of the plasma. Interface definition language routines have been developed for this purpose. The calculated plasma position data correspond well to calculation results from magnetic analysis. With the position data and an estimated plasma profile, the peak density and the mean density have been obtained from the line density. From these results, changes of plasma density themselves can be separated from effects of the plasma movements, so they can give valuable information on the plasma status.

  8. Profile control of advanced tokamak plasmas in view of continuous operation

    NASA Astrophysics Data System (ADS)

    Mazon, D.

    2015-07-01

    The concept of the tokamak is a very good candidate to lead to a fusion reactor. In fact, certain regimes of functioning allow today the tokamaks to attain performances close to those requested by a reactor. Among the various scenarios of functioning nowadays considered for the reactor option, certain named 'advanced scenarios' are characterized by an improvement of the stability and confinement in the plasma core, as well as by a modification of the current profile, notably thank to an auto-generated 'bootstrap' current. The general frame of this paper treats the perspective of a real-time control of advanced regimes. Concrete examples will underline the impact of diagnostics on the identification of plasma models, from which the control algorithms are constructed. Several preliminary attempts will be described.

  9. Plasma Shape and Current Density Profile Control in Advanced Tokamak Operating Scenarios

    NASA Astrophysics Data System (ADS)

    Shi, Wenyu

    The need for new sources of energy is expected to become a critical problem within the next few decades. Nuclear fusion has sufficient energy density to potentially supply the world population with its increasing energy demands. The tokamak is a magnetic confinement device used to achieve controlled fusion reactions. Experimental fusion technology has now reached a level where tokamaks are able to produce about as much energy as is expended in heating the fusion fuel. The next step towards the realization of a nuclear fusion tokamak power plant is ITER, which will be capable of exploring advanced tokamak (AT) modes, characterized by a high fusion gain and plasma stability. The extreme requirements of the advanced modes motivates researchers to improve the modeling of the plasma response as well as the design of feedback controllers. This dissertation focuses on several magnetic and kinetic control problems, including the plasma current, position and shape control, and data-driven and first-principles-driven modeling and control of plasma current density profile and the normalized plasma pressure ratio betaN. The plasma is confined within the vacuum vessel by an external electromagnetic field, produced primarily by toroidal and poloidal field coils. The outermost closed plasma surface or plasma boundary is referred to as the shape of the plasma. A central characteristic of AT plasma regimes is an extreme elongated shape. The equilibrium among the electromagnetic forces acting on an elongated plasma is unstable. Moreover, the tokamak performance is improved if the plasma is located in close proximity to the torus wall, which guarantees an efficient use of available volume. As a consequence, feedback control of the plasma position and shape is necessary. In this dissertation, an Hinfinity-based, multi-input-multi-output (MIMO) controller for the National Spherical Torus Experiment (NSTX) is developed, which is used to control the plasma position, shape, and X

  10. Fishbone activity in experimental advanced superconducting tokamak neutral beam injection plasma

    SciTech Connect

    Xu, Liqing; Zhang, Jizong; Chen, Kaiyun E-mail: lqhu@ipp.cas.cn; Hu, Liqun E-mail: lqhu@ipp.cas.cn; Li, Erzhong; Lin, Shiyao; Shi, Tonghui; Duan, Yanmin; Zhu, Yubao

    2015-12-15

    Repetitive fishbones near the trapped ion procession frequency were observed for the first time in the neutral beam injection high confinement plasmas in Experimental Advanced Superconducting Tokamak (EAST) tokamak, and diagnosed using a solid-state neutral particle analyzer based on a compact silicon photodiode together with an upgraded high spatial-temporal-resolution multi-arrays soft X-ray (SX) system. This 1/1 typical internal kink mode propagates in the ion-diamagnetism direction with a rotation speed faster than the bulk plasma in the plasma frame. From the SX measurements, this mode frequency is typical of chirping down and the energetic particle effect related to the twisting mode structure. This ion fishbone was found able to trigger a multiple core sawtooth crashes with edge-2/1 sideband modes, as well as to lead to a transition from fishbone to long lived saturated kink mode to fishbone. Furthermore, using SX tomography, a correlation between mode amplitude and mode frequency was found. Finally, a phenomenological prey–predator model was found to reproduce the fishbone nonlinear process well.

  11. Fishbone activity in experimental advanced superconducting tokamak neutral beam injection plasma

    NASA Astrophysics Data System (ADS)

    Xu, Liqing; Zhang, Jizong; Chen, Kaiyun; Hu, Liqun; Li, Erzhong; Lin, Shiyao; Shi, Tonghui; Duan, Yanmin; Zhu, Yubao

    2015-12-01

    Repetitive fishbones near the trapped ion procession frequency were observed for the first time in the neutral beam injection high confinement plasmas in Experimental Advanced Superconducting Tokamak (EAST) tokamak, and diagnosed using a solid-state neutral particle analyzer based on a compact silicon photodiode together with an upgraded high spatial-temporal-resolution multi-arrays soft X-ray (SX) system. This 1/1 typical internal kink mode propagates in the ion-diamagnetism direction with a rotation speed faster than the bulk plasma in the plasma frame. From the SX measurements, this mode frequency is typical of chirping down and the energetic particle effect related to the twisting mode structure. This ion fishbone was found able to trigger a multiple core sawtooth crashes with edge-2/1 sideband modes, as well as to lead to a transition from fishbone to long lived saturated kink mode to fishbone. Furthermore, using SX tomography, a correlation between mode amplitude and mode frequency was found. Finally, a phenomenological prey-predator model was found to reproduce the fishbone nonlinear process well.

  12. Development of Burning Plasma and Advanced Scenarios in the DIII-D Tokamak

    SciTech Connect

    Luce, T C

    2004-12-01

    Significant progress in the development of burning plasma scenarios, steady-state scenarios at high fusion performance, and basic tokamak physics has been made by the DIII-D Team. Discharges similar to the ITER baseline scenario have demonstrated normalized fusion performance nearly 50% higher than required for Q = 10 in ITER, under stationary conditions. Discharges that extrapolate to Q {approx} 10 for longer than one hour in ITER at reduced current have also been demonstrated in DIII-D under stationary conditions. Proof of high fusion performance with full noninductive operation has been obtained. Underlying this work are studies validating approaches to confinement extrapolation, disruption avoidance and mitigation, tritium retention, ELM avoidance, and operation above the no-wall pressure limit. In addition, the unique capabilities of the DIII-D facility have advanced studies of the sawtooth instability with unprecedented time and space resolution, threshold behavior in the electron heat transport, and rotation in plasmas in the absence of external torque.

  13. Development of Burning Plasma and Advanced Scenarios in the DIII-D Tokamak

    SciTech Connect

    Luce, T C

    2004-10-18

    Significant progress in the development of burning plasma scenarios, steady-state scenarios at high fusion performance, and basic tokamak physics has been made by the DIII-D Team. Discharges similar to the ITER baseline scenario have demonstrated normalized fusion performance nearly 50% higher than required for Q = 10 in ITER, under stationary conditions. Discharges that extrapolate to Q {approx} 10 for longer than one hour in ITER at reduced current have also been demonstrated in DIII-D under stationary conditions. Proof of high fusion performance with full noninductive operation has been obtained. Underlying this work are studies validating approaches to confinement extrapolation, disruption avoidance and mitigation, tritium retention, ELM avoidance, and operation above the no-wall pressure limit. In addition, the unique capabilities of the DIII-D facility have advanced studies of the sawtooth instability with unprecedented time and space resolution, threshold behavior in the electron heat transport, and rotation in plasmas in the absence of external torque.

  14. Advanced Fuels Reactor using Aneutronic Rodless Ultra Low Aspect Ratio Tokamak Hydrogenic Plasmas

    NASA Astrophysics Data System (ADS)

    Ribeiro, Celso

    2015-11-01

    The use of advanced fuels for fusion reactor is conventionally envisaged for field reversed configuration (FRC) devices. It is proposed here a preliminary study about the use of these fuels but on an aneutronic Rodless Ultra Low Aspect Ratio (RULART) hydrogenic plasmas. The idea is to inject micro-size boron pellets vertically at the inboard side (HFS, where TF is very high and the tokamak electron temperature is relatively low because of profile), synchronised with a proton NBI pointed to this region. Therefore, p-B reactions should occur and alpha particles produced. These pellets will act as an edge-like disturbance only (cp. killer pellet, although the vertical HFS should make this less critical, since the unablated part should appear in the bottom of the device). The boron cloud will appear at midplance, possibly as a MARFE-look like. Scaling of the p-B reactions by varying the NBI energy should be compared with the predictions of nuclear physics. This could be an alternative to the FRC approach, without the difficulties of the optimization of the FRC low confinement time. Instead, a robust good tokamak confinement with high local HFS TF (enhanced due to the ultra low aspect ratio and low pitch angle) is used. The plasma central post makes the RULART concept attractive because of the proximity of NBI path and also because a fraction of born alphas will cross the plasma post and dragged into it in the direction of the central plasma post current, escaping vertically into a hole in the bias plate and reaching the direct electricity converter, such as in the FRC concept.

  15. New steady-state quiescent high-confinement plasma in an experimental advanced superconducting tokamak.

    PubMed

    Hu, J S; Sun, Z; Guo, H Y; Li, J G; Wan, B N; Wang, H Q; Ding, S Y; Xu, G S; Liang, Y F; Mansfield, D K; Maingi, R; Zou, X L; Wang, L; Ren, J; Zuo, G Z; Zhang, L; Duan, Y M; Shi, T H; Hu, L Q

    2015-02-01

    A critical challenge facing the basic long-pulse high-confinement operation scenario (H mode) for ITER is to control a magnetohydrodynamic (MHD) instability, known as the edge localized mode (ELM), which leads to cyclical high peak heat and particle fluxes at the plasma facing components. A breakthrough is made in the Experimental Advanced Superconducting Tokamak in achieving a new steady-state H mode without the presence of ELMs for a duration exceeding hundreds of energy confinement times, by using a novel technique of continuous real-time injection of a lithium (Li) aerosol into the edge plasma. The steady-state ELM-free H mode is accompanied by a strong edge coherent MHD mode (ECM) at a frequency of 35-40 kHz with a poloidal wavelength of 10.2 cm in the ion diamagnetic drift direction, providing continuous heat and particle exhaust, thus preventing the transient heat deposition on plasma facing components and impurity accumulation in the confined plasma. It is truly remarkable that Li injection appears to promote the growth of the ECM, owing to the increase in Li concentration and hence collisionality at the edge, as predicted by GYRO simulations. This new steady-state ELM-free H-mode regime, enabled by real-time Li injection, may open a new avenue for next-step fusion development.

  16. Advanced commercial tokamak study

    SciTech Connect

    Thomson, S.L.; Dabiri, A.E.; Keeton, D.C.; Brown, T.G.; Bussell, G.T.

    1985-12-01

    Advanced commercial tokamak studies were performed by the Fusion Engineering Design Center (FEDC) as a participant in the Tokamak Power Systems Studies (TPSS) project coordinated by the Office of Fusion Energy. The FEDC studies addressed the issues of tokamak reactor cost, size, and complexity. A scoping study model was developed to determine the effect of beta on tokamak economics, and it was found that a competitive cost of electricity could be achieved at a beta of 10 to 15%. The implications of operating at a beta of up to 25% were also addressed. It was found that the economics of fusion, like those of fission, improve as unit size increases. However, small units were found to be competitive as elements of a multiplex plant, provided that unit cost and maintenance time reductions are realized for the small units. The modular tokamak configuration combined several new approaches to develop a less complex and lower cost reactor. The modular design combines the toroidal field coil with the reactor structure, locates the primary vacuum boundary at the reactor cell wall, and uses a vertical assembly and maintenance approach. 12 refs., 19 figs.

  17. Tokamak plasma modelling and atomic processes

    NASA Astrophysics Data System (ADS)

    Kawamura, T.

    1986-06-01

    Topics addressed include: particle control in a tokomak device; ionizing and recombining plasmas; effects of data accuracy on tokamak impurity transport modeling; plasma modeling of tokamaks; and ultraviolet and X-ray spectroscopy of tokamak plasmas.

  18. Effect of gas puffing from different side on lower hybrid wave-plasma coupling in experimental advanced superconductive tokamak

    NASA Astrophysics Data System (ADS)

    Ding, B. J.; Kong, E. H.; Zhang, T.; Ekedahl, A.; Li, M. H.; Zhang, L.; Wei, W.; Li, Y. C.; Wu, J. H.; Xu, G. S.; Zhao, H. L.; Wang, M.; Gong, X. Z.; Shan, J. F.; Liu, F. K.; EAST Team

    2013-10-01

    Effect of gas puffing from electron-side and ion-side on lower hybrid wave (LHW)-plasma is investigated in experimental advanced superconductive tokamak for the first time. Experimental results with different gas flow rates show that electron density at the grill is higher in the case of gas puffing from electron-side; consequently, a lower reflection coefficient is observed, suggesting better effect of puffing from electron-side on LHW-plasma. The difference in edge density between electron- and ion-side cases suggests that local ionization of puffed gas plays a dominant role in affecting the density at the grill due to different movement direction of ionized electrons and that part of gas has been locally ionized near the gas pipe before diffusing into the grill region. Such difference could be enlarged and important in ITER due to the improvement of plasma parameters and LHW power.

  19. Integrated magnetic and kinetic control of advanced tokamak plasmas on DIII-D based on data-driven models

    NASA Astrophysics Data System (ADS)

    Moreau, D.; Walker, M. L.; Ferron, J. R.; Liu, F.; Schuster, E.; Barton, J. E.; Boyer, M. D.; Burrell, K. H.; Flanagan, S. M.; Gohil, P.; Groebner, R. J.; Holcomb, C. T.; Humphreys, D. A.; Hyatt, A. W.; Johnson, R. D.; La Haye, R. J.; Lohr, J.; Luce, T. C.; Park, J. M.; Penaflor, B. G.; Shi, W.; Turco, F.; Wehner, W.; the ITPA-IOS Group members; experts

    2013-06-01

    The first real-time profile control experiments integrating magnetic and kinetic variables were performed on DIII-D in view of regulating and extrapolating advanced tokamak scenarios to steady-state devices and burning plasma experiments. Device-specific, control-oriented models were obtained from experimental data using a generic two-time-scale method that was validated on JET, JT-60U and DIII-D under the framework of the International Tokamak Physics Activity for Integrated Operation Scenarios (Moreau et al 2011 Nucl. Fusion 51 063009). On DIII-D, these data-driven models were used to synthesize integrated magnetic and kinetic profile controllers. The neutral beam injection (NBI), electron cyclotron current drive (ECCD) systems and ohmic coil provided the heating and current drive (H&CD) sources. The first control actuator was the plasma surface loop voltage (i.e. the ohmic coil), and the available beamlines and gyrotrons were grouped to form five additional H&CD actuators: co-current on-axis NBI, co-current off-axis NBI, counter-current NBI, balanced NBI and total ECCD power from all gyrotrons (with off-axis current deposition). Successful closed-loop experiments showing the control of (a) the poloidal flux profile, Ψ(x), (b) the poloidal flux profile together with the normalized pressure parameter, βN, and (c) the inverse of the safety factor profile, \\bar{\\iota}(x)=1/q(x) , are described.

  20. Transport Equations In Tokamak Plasmas

    NASA Astrophysics Data System (ADS)

    Callen, J. D.

    2009-11-01

    Tokamak plasma transport equations are usually obtained by flux surface averaging the collisional Braginskii equations. However, tokamak plasmas are not in collisional regimes. Also, ad hoc terms are added for: neoclassical effects on the parallel Ohm's law (trapped particle effects on resistivity, bootstrap current); fluctuation-induced transport; heating, current-drive and flow sources and sinks; small B field non-axisymmetries; magnetic field transients etc. A set of self-consistent second order in gyroradius fluid-moment-based transport equations for nearly axisymmetric tokamak plasmas has been developed recently using a kinetic-based framework. The derivation uses neoclassical-based parallel viscous force closures, and includes all the effects noted above. Plasma processes on successive time scales (and constraints they impose) are considered sequentially: compressional Alfv'en waves (Grad-Shafranov equilibrium, ion radial force balance); sound waves (pressure constant along field lines, incompressible flows within a flux surface); and ion collisions (damping of poloidal flow). Radial particle fluxes are driven by the many second order in gyroradius toroidal angular torques on the plasma fluid: 7 ambipolar collision-based ones (classical, neoclassical, etc.) and 8 non-ambipolar ones (fluctuation-induced, polarization flows from toroidal rotation transients etc.). The plasma toroidal rotation equation [1] results from setting to zero the net radial current induced by the non-ambipolar fluxes. The radial particle flux consists of the collision-based intrinsically ambipolar fluxes plus the non-ambipolar fluxes evaluated at the ambipolarity-enforcing toroidal plasma rotation (radial electric field). The energy transport equations do not involve an ambipolar constraint and hence are more directly obtained. The resultant transport equations will be presented and contrasted with the usual ones. [4pt] [1] J.D. Callen, A.J. Cole, C.C. Hegna, ``Toroidal Rotation In

  1. Impact of E × B flow shear on turbulence and resulting power fall-off width in H-mode plasmas in experimental advanced superconducting tokamak

    SciTech Connect

    Yang, Q. Q. Zhong, F. C. E-mail: fczhong@dhu.edu.cn; Jia, M. N.; Xu, G. S. E-mail: fczhong@dhu.edu.cn; Wang, L.; Wang, H. Q.; Chen, R.; Yan, N.; Liu, S. C.; Chen, L.; Li, Y. L.; Liu, J. B.

    2015-06-15

    The power fall-off width in the H-mode scrape-off layer (SOL) in tokamaks shows a strong inverse dependence on the plasma current, which was noticed by both previous multi-machine scaling work [T. Eich et al., Nucl. Fusion 53, 093031 (2013)] and more recent work [L. Wang et al., Nucl. Fusion 54, 114002 (2014)] on the Experimental Advanced Superconducting Tokamak. To understand the underlying physics, probe measurements of three H-mode discharges with different plasma currents have been studied in this work. The results suggest that a higher plasma current is accompanied by a stronger E×B shear and a shorter radial correlation length of turbulence in the SOL, thus resulting in a narrower power fall-off width. A simple model has also been applied to demonstrate the suppression effect of E×B shear on turbulence in the SOL and shows relatively good agreement with the experimental observations.

  2. Dynamically stable, self-similarly evolving, and self-organized states of high beta tokamak and reversed pinch plasmas and advanced active control

    SciTech Connect

    Kondoh, Yoshiomi; Fukasawa, Toshinobu

    2009-11-15

    Generalized simultaneous eigenvalue equations derived from a generalized theory of self-organization are applied to a set of simultaneous equations for two-fluid model plasmas. An advanced active control by using theoretical time constants is proposed by predicting quantities to be controlled. Typical high beta numerical configurations are presented for the ultra low q tokamak plasmas and the reversed-field pinch (RFP) ones in cylindrical geometry by solving the set of simultaneous eigenvalue equations. Improved confinement with no detectable saw-teeth oscillations in tokamak experiments is reasonably explained by the shortest time constant of ion flow. The shortest time constant of poloidal ion flow is shown to be a reasonable mechanism for suppression of magnetic fluctuations by pulsed poloidal current drives in RFP experiments. The bifurcation from basic eigenmodes to mixed ones deduced from stability conditions for eigenvalues is shown to be a good candidate for the experimental bifurcation from standard RFP plasmas to their improved confinement regimes.

  3. Impact of E × B flow shear on turbulence and resulting power fall-off width in H-mode plasmas in experimental advanced superconducting tokamak

    NASA Astrophysics Data System (ADS)

    Yang, Q. Q.; Xu, G. S.; Zhong, F. C.; Wang, L.; Wang, H. Q.; Chen, R.; Yan, N.; Liu, S. C.; Chen, L.; Jia, M. N.; Li, Y. L.; Liu, J. B.

    2015-06-01

    The power fall-off width in the H-mode scrape-off layer (SOL) in tokamaks shows a strong inverse dependence on the plasma current, which was noticed by both previous multi-machine scaling work [T. Eich et al., Nucl. Fusion 53, 093031 (2013)] and more recent work [L. Wang et al., Nucl. Fusion 54, 114002 (2014)] on the Experimental Advanced Superconducting Tokamak. To understand the underlying physics, probe measurements of three H-mode discharges with different plasma currents have been studied in this work. The results suggest that a higher plasma current is accompanied by a stronger E × B shear and a shorter radial correlation length of turbulence in the SOL, thus resulting in a narrower power fall-off width. A simple model has also been applied to demonstrate the suppression effect of E × B shear on turbulence in the SOL and shows relatively good agreement with the experimental observations.

  4. Tokamak plasma interaction with limiters

    NASA Astrophysics Data System (ADS)

    Pitcher, Charles Spencer

    1988-08-01

    The importance of plasma purity is discussed in terms of the general requirements of controlled thermonuclear fusion. The tokamak approach to fusion and its inherent problem of plasma contamination are introduced. A main source of impurities is due to the bombardment of the limiter by energetic particles and thus the three main aspects of the plasma-limiter interaction are reviewed, boundary plasma conditions, fueling/recycling and impurity production. The experiments, carried out on the DITE tokomak at Culham Laboratory, UK, investigated these three topics and the results are compared with predicted behavior; new physical phenomena are presented in all three areas.

  5. Fluid-particle hybrid simulation on the transports of plasma, recycling neutrals, and carbon impurities in the Korea Superconducting Tokamak Advanced Research divertor region

    NASA Astrophysics Data System (ADS)

    Kim, Deok-Kyu; Hong, Sang Hee

    2005-06-01

    A two-dimensional simulation modeling that has been performed in a self-consistent way for analysis on the fully coupled transports of plasma, recycling neutrals, and intrinsic carbon impurities in the divertor domain of tokamaks is presented. The numerical model coupling the three major species transports in the tokamak edge is based on a fluid-particle hybrid approach where the plasma is described as a single magnetohydrodynamic fluid while the neutrals and impurities are treated as kinetic particles using the Monte Carlo technique. This simulation code is applied to the KSTAR (Korea Superconducting Tokamak Advanced Research) tokamak [G. S. Lee, J. Kim, S. M. Hwang et al., Nucl. Fusion 40, 575 (2000)] to calculate the peak heat flux on the divertor plate and to explore the divertor plasma behavior depending on the upstream conditions in its base line operation mode for various values of input heating power and separatrix plasma density. The numerical modeling for the KSTAR tokamak shows that its full-powered operation is subject to the peak heat loads on the divertor plate exceeding an engineering limit, and reveals that the recycling zone is formed in front of the divertor by increasing plasma density and by reducing power flow into the scrape-off layer. Compared with other researchers' work, the present hybrid simulation more rigorously reproduces severe electron pressure losses along field lines by the presence of recycling zone accounting for the transitions between the sheath limited and the detached divertor regimes. The substantial profile changes in carbon impurity population and ionic composition also represent the key features of this divertor regime transition.

  6. Transport equations in tokamak plasmas

    SciTech Connect

    Callen, J. D.; Hegna, C. C.; Cole, A. J.

    2010-05-15

    Tokamak plasma transport equations are usually obtained by flux surface averaging the collisional Braginskii equations. However, tokamak plasmas are not in collisional regimes. Also, ad hoc terms are added for neoclassical effects on the parallel Ohm's law, fluctuation-induced transport, heating, current-drive and flow sources and sinks, small magnetic field nonaxisymmetries, magnetic field transients, etc. A set of self-consistent second order in gyroradius fluid-moment-based transport equations for nearly axisymmetric tokamak plasmas has been developed using a kinetic-based approach. The derivation uses neoclassical-based parallel viscous force closures, and includes all the effects noted above. Plasma processes on successive time scales and constraints they impose are considered sequentially: compressional Alfven waves (Grad-Shafranov equilibrium, ion radial force balance), sound waves (pressure constant along field lines, incompressible flows within a flux surface), and collisions (electrons, parallel Ohm's law; ions, damping of poloidal flow). Radial particle fluxes are driven by the many second order in gyroradius toroidal angular torques on a plasma species: seven ambipolar collision-based ones (classical, neoclassical, etc.) and eight nonambipolar ones (fluctuation-induced, polarization flows from toroidal rotation transients, etc.). The plasma toroidal rotation equation results from setting to zero the net radial current induced by the nonambipolar fluxes. The radial particle flux consists of the collision-based intrinsically ambipolar fluxes plus the nonambipolar fluxes evaluated at the ambipolarity-enforcing toroidal plasma rotation (radial electric field). The energy transport equations do not involve an ambipolar constraint and hence are more directly obtained. The 'mean field' effects of microturbulence on the parallel Ohm's law, poloidal ion flow, particle fluxes, and toroidal momentum and energy transport are all included self-consistently. The

  7. ADX - Advanced Divertor and RF Tokamak Experiment

    NASA Astrophysics Data System (ADS)

    Greenwald, Martin; Labombard, Brian; Bonoli, Paul; Irby, Jim; Terry, Jim; Wallace, Greg; Vieira, Rui; Whyte, Dennis; Wolfe, Steve; Wukitch, Steve; Marmar, Earl

    2015-11-01

    The Advanced Divertor and RF Tokamak Experiment (ADX) is a design concept for a compact high-field tokamak that would address boundary plasma and plasma-material interaction physics challenges whose solution is critical for the viability of magnetic fusion energy. This device would have two crucial missions. First, it would serve as a Divertor Test Tokamak, developing divertor geometries, materials and operational scenarios that could meet the stringent requirements imposed in a fusion power plant. By operating at high field, ADX would address this problem at a level of power loading and other plasma conditions that are essentially identical to those expected in a future reactor. Secondly, ADX would investigate the physics and engineering of high-field-side launch of RF waves for current drive and heating. Efficient current drive is an essential element for achieving steady-state in a practical, power producing fusion device and high-field launch offers the prospect of higher efficiency, better control of the current profile and survivability of the launching structures. ADX would carry out this research in integrated scenarios that simultaneously demonstrate the required boundary regimes consistent with efficient current drive and core performance.

  8. Tokamak plasma position dynamics and feedback control

    SciTech Connect

    Burenko, L.; Bailey, J.M.

    1983-01-01

    The perturbation equations of a tokamak plasma equilibrium position are developed. Solution of the approximated perturbation equations is carried out. A unique, simple, and useful plasma displacement dynamics transfer function of a tokamak is developed. The dominant time constants of the dynamics transfer function are determined in a symbolic form.

  9. Toroidal Flow in Tokamak Plasmas

    NASA Astrophysics Data System (ADS)

    Callen, J. D.; Cole, A. J.; Hegna, C. C.

    2007-11-01

    Many effects influence toroidal flow evolution in tokamak plasmas. Momentum sources and radial diffusion due to axisymmetric neoclassical, paleoclassical and anomalous transport are usually considered. In addition, the toroidal flow can be affected by field errors. Small, non-axisymmetric field errors arise from coil irregularities, active control coils and collective plasma magnetic distortions (e.g., NTMs, RWMs). Resonant field errors cause localized electromagnetic torques near rational surfaces in the plasma, which can lock the plasma to the wall leading to magnetic islands and reduced confinement or disruptions. Their penetration into the plasma is limited by flow-shielding effects; but they can be amplified by the plasma response at high beta. Non-resonant field errors cause magnetic pumping and radial banana drifts, and lead to toroidal flow damping over the entire plasma. Many of these processes can also produce momentum pinch and intrinsic flow effects. This poster will seek to present a coherent picture of all these effects and suggest ways they could be tested and distinguished experimentally.

  10. Observations of compound sawteeth in ion cyclotron resonant heating plasma using ECE imaging on experimental advanced superconducting tokamak

    NASA Astrophysics Data System (ADS)

    Hussain, Azam; Zhao, Zhenling; Xie, Jinlin; Zhu, Ping; Liu, Wandong; Ti, Ang

    2016-04-01

    The spatial and temporal evolutions of compound sawteeth were directly observed using 2D electron cyclotron emission imaging on experimental advanced superconducting tokamak. The compound sawtooth consists of partial and full collapses. After partial collapse, the hot core survives as only a small amount of heat disperses outwards, whereas in the following full collapse a large amount of heat is released and the hot core dissipates. The presence of two q = 1 surfaces was not observed. Instead, the compound sawtooth occurs mainly at the beginning of an ion cyclotron resonant frequency heating pulse and during the L-H transition phase, which may be related to heat transport suppression caused by a decrease in electron heat diffusivity.

  11. OPTIMUM PLASMA STATES FOR NEXT STEP TOKAMAKS

    SciTech Connect

    LIN-LIU,YR; STAMBAUGH,RD

    2002-11-01

    OAK A271 OPTIMUM PLASMA STATES FOR NEXT STEP TOKAMAKS. The dependence of the ideal ballooning {beta} limit on aspect ratio, A, and elongation {kappa} is systematically explored for nearly 100% bootstrap current driven tokamak equilibria in a wide range of the shape parameters (A = 1.2-7.0, {kappa} = 1.5-6.0 with triangularity {delta} = 0.5). The critical {beta}{sub N} is shown to be optimal at {kappa} = 3.0-4.0 for all A studied and increases as A decreases with a dependence close to A{sup -0.5}. The results obtained can be used as a theoretical basis for the choice of optimum aspect ratio and elongation of next step burning plasma tokamaks or tokamak reactors.

  12. Plasma-gun fueling for tokamak reactors

    SciTech Connect

    Ehst, D.A.

    1980-11-01

    In light of the uncertain extrapolation of gas puffing for reactor fueling and certain limitations to pellet injection, the snowplow plasma gun has been studied as a fueling device. Based on current understanding of gun and plasma behavior a design is proposed, and its performance is predicted in a tokamak reactor environment.

  13. Fusion Plasma Theory: Task 3, Auxiliary radiofrequency heating of tokamaks

    SciTech Connect

    Scharer, J.E.

    1992-01-01

    The research performed under this grant during the past year has been concentrated on the following several key tokamak ICRF (Ion Cyclotron Range of Frequencies) coupling, heating and current drive issues: Efficient coupling during the L- to H- mode transition by analysis and computer simulation of ICRF antennas; analysis of ICRF cavity-backed coil antenna coupling to plasma edge profiles including fast and ion Bernstein wave coupling for heating and current drive; benchmarking the codes to compare with current JET, D-IIID and ASDEX experimental results and predictions for advanced tokamaks such as BPX and SSAT (Steady-State Advanced Tokamak); ICRF full-wave field solutions, power conservation, heating analyses and minority ion current drive; and the effects of fusion alpha particle or ion tail populations on the ICRF absorption. Research progress, publications, and conference and workshop presentations are summarized in this report.

  14. 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.

  15. Boundary Plasma Turbulence Simulations for Tokamaks

    SciTech Connect

    Xu, X; Umansky, M; Dudson, B; Snyder, P

    2008-05-15

    The boundary plasma turbulence code BOUT models tokamak boundary-plasma turbulence in a realistic divertor geometry using modified Braginskii equations for plasma vorticity, density (ni), electron and ion temperature (T{sub e}; T{sub i}) and parallel momenta. The BOUT code solves for the plasma fluid equations in a three dimensional (3D) toroidal segment (or a toroidal wedge), including the region somewhat inside the separatrix and extending into the scrape-off layer; the private flux region is also included. In this paper, a description is given of the sophisticated physical models, innovative numerical algorithms, and modern software design used to simulate edge-plasmas in magnetic fusion energy devices. The BOUT code's unique capabilities and functionality are exemplified via simulations of the impact of plasma density on tokamak edge turbulence and blob dynamics.

  16. Burning plasma simulation and environmental assessment of tokamak, spherical tokamak and helical reactors

    NASA Astrophysics Data System (ADS)

    Yamazaki, K.; Uemura, S.; Oishi, T.; Garcia, J.; Arimoto, H.; Shoji, T.

    2009-05-01

    Reference 1-GWe DT reactors (tokamak TR-1, spherical tokamak ST-1 and helical HR-1 reactors) are designed using physics, engineering and cost (PEC) code, and their plasma behaviours with internal transport barrier operations are analysed using toroidal transport analysis linkage (TOTAL) code, which clarifies the requirement of deep penetration of pellet fuelling to realize steady-state advanced burning operation. In addition, economical and environmental assessments were performed using extended PEC code, which shows the advantage of high beta tokamak reactors in the cost of electricity (COE) and the advantage of compact spherical tokamak in life-cycle CO2 emission reduction. Comparing with other electric power generation systems, the COE of the fusion reactor is higher than that of the fission reactor, but on the same level as the oil thermal power system. CO2 reduction can be achieved in fusion reactors the same as in the fission reactor. The energy payback ratio of the high-beta tokamak reactor TR-1 could be higher than that of other systems including the fission reactor.

  17. Electrostatic analysis of the tokamak edge plasma

    SciTech Connect

    Motley, R.W.

    1981-07-01

    The intrusion of an equipotential poloidal limiter into the edge plasma of a circular tokamak discharge distorts the axisymmetry in two ways: (1) it (partially) shorts out the top-to-bottom Pfirsch-Schlueter driving potentials, and (2) it creates zones of back current flow into the limiter. The resulting boundary mismatch between the outer layers and the inner axisymmetric Pfirsch-Schlueter layer provides free energy to drive the edge plasma unstable. Special limiters are proposed to symmetrize the edge plasma and thereby reduce the electrical and MHD activity in the boundary layer.

  18. Forced Magnetic Reconnection In A Tokamak Plasma

    NASA Astrophysics Data System (ADS)

    Callen, J. D.; Hegna, C. C.

    2015-11-01

    The theory of forced magnetic field reconnection induced by an externally imposed resonant magnetic perturbation usually uses a sheared slab or cylindrical magnetic field model and often focuses on the potential time-asymptotic induced magnetic island state. However, tokamak plasmas have significant magnetic geometry and dynamical plasma toroidal rotation screening effects. Also, finite ion Larmor radius (FLR) and banana width (FBW) effects can damp and thus limit the width of a nascent magnetic island. A theory that is more applicable for tokamak plasmas is being developed. This new model of the dynamics of forced magnetic reconnection considers a single helicity magnetic perturbation in the tokamak magnetic field geometry, uses a kinetically-derived collisional parallel electron flow response, and employs a comprehensive dynamical equation for the plasma toroidal rotation frequency. It is being used to explore the dynamics of bifurcation into a magnetically reconnected state in the thin singular layer around the rational surface, evolution into a generalized Rutherford regime where the island width exceeds the singular layer width, and assess the island width limiting effects of FLR and FBW polarization currents. Support by DoE grants DE-FG02-86ER53218, DE-FG02-92ER54139.

  19. NEXT-GENERATION PLASMA CONTROL IN THE DIII-D TOKAMAK

    SciTech Connect

    WALKER, ML; FERRON, JR; HUMPHREYS, DA; JOHNSON, RD; LEUER, JA; PENAFLOR, BG; PIGLOWSKI, DA; ARIOLA, M; PIRONTI, A; SCHUSTER, E

    2002-10-01

    OAK A271 NEXT-GENERATION PLASMA CONTROL IN THE DIII-D TOKAMAK. The advanced tokamak (AT) operating mode which is the principal focus of the DIII-D tokamak requires highly integrated and complex plasma control. Simultaneous high performance regulation of the plasma boundary and internal profiles requires multivariable control techniques to account for the highly coupled influences of equilibrium shape, profile, and stability control. This paper describes progress towards the DIII-D At mission goal through both significantly improved real-time computational hardware and control algorithm capability.

  20. Properties of dc helicity injected tokamak plasmas

    SciTech Connect

    Darrow, D.S.; Ono, M.; Forest, C.B.; Greene, G.J.; Hwang, Y.S.; Park, H.K. ); Taylor, R.J.; Pribyl, P.A.; Evans, J.D.; Lai, K.F.; Liberati, J.R. )

    1990-06-01

    Several dc helicity injection experiments using an electron beam technique have been conducted on the Current Drive Experiment (CDX) (Phys. Rev. Lett. {bold 59}, 2165 (1987)) and the Continuous Current Tokamak (CCT) (Phys. Rev. Lett. {bold 63}, 2365 (1989)). The data strongly suggest that tokamak plasmas are being formed and maintained by this method. The largest currents driven to date are 1 kA in CDX ({ital q}{sub {ital a}} =5) and 6 kA in CCT ({ital q}{sub {ital a}} =3.5). An initial comparison of discharge properties with helicity theory indicates rough agreement. Current drive energy efficiencies are 9% and 23% of Ohmic efficiency in two cases analyzed. Strong radial electric fields are observed in these plasmas that cause poloidal rotation and, possibly, improved confinement.

  1. High beta plasmas in the PBX tokamak

    SciTech Connect

    Bol, K.; Buchenauer, D.; Chance, M.; Couture, P.; Fishman, H.; Fonck, R.; Gammel, G.; Grek, B.; Ida, K.; Itami, K.

    1986-04-01

    Bean-shaped configurations favorable for high ..beta.. discharges have been investigated in the Princeton Beta Experiment (PBX) tokamak. Strongly indented bean-shaped plasmas have been successfully formed, and beta values of over 5% have been obtained with 5 MW of injected neutral beam power. These high beta discharges still lie in the first stability regime for ballooning modes, and MHD stability analysis implicates the external kink as responsible for the present ..beta.. limit.

  2. Plasma Physics Regimes in Tokamaks with Li Walls

    SciTech Connect

    L.E. Zakharo; N.N. Gorelenkov; R.B. White; S.I. Krasheninnikov; G.V. Pereverzev

    2003-08-21

    Low recycling regimes with a plasma limited by a lithium wall surface suggest enhanced stability and energy confinement, both necessary for tokamak reactors. These regimes could make ignition feasible in compact tokamaks. Ignited Spherical Tokamaks (IST), self-sufficient in the bootstrap current, are introduced as a necessary step for development of the physics and technology of power reactors.

  3. LIDAR Thomson scattering for advanced tokamaks. Final report

    SciTech Connect

    Molvik, A.W.; Lerche, R.A.; Nilson, D.G.

    1996-03-18

    The LIDAR Thomson Scattering for Advanced Tokamaks project made a valuable contribution by combining LLNL expertise from the MFE Program: tokamak design and diagnostics, and the ICF Program and Physics Dept.: short-pulse lasers and fast streak cameras. This multidisciplinary group evaluated issues involved in achieving a factor of 20 higher high spatial resolution (to as small as 2-3 mm) from the present state of the art in LIDAR Thomson scattering, and developed conceptual designs to apply LIDAR Thomson scattering to three tokamaks: Upgraded divertor measurements in the existing DIII-D tokamak; Both core and divertor LIDAR Thomson scattering in the proposed (now cancelled) TPX; and core, edge, and divertor LIDAR Thomson scattering on the presently planned International Tokamak Experimental Reactor, ITER. Other issues were evaluated in addition to the time response required for a few millimeter spatial resolution. These include the optimum wavelength, 100 Hz operation of the laser and detectors, minimizing stray light - always the Achilles heel of Thomson scattering, and time dispersion in optics that could prevent good spatial resolution. Innovative features of our work included: custom short pulsed laser concepts to meet specific requirements, use of a prism spectrometer to maintain a constant optical path length for high temporal and spatial resolution, the concept of a laser focus outside the plasma to ionize gas and form an external fiducial to use in locating the plasma edge as well as to spread the laser energy over a large enough area of the inner wall to avoid laser ablation of wall material, an improved concept for cleaning windows between shots by means of laser ablation, and the identification of a new physics issue - nonlinear effects near a laser focus which could perturb the plasma density and temperature that are to be measured.

  4. Spontaneous generation of rotation in tokamak plasmas

    SciTech Connect

    Parra Diaz, Felix

    2013-12-24

    Three different aspects of intrinsic rotation have been treated. i) A new, first principles model for intrinsic rotation [F.I. Parra, M. Barnes and P.J. Catto, Nucl. Fusion 51, 113001 (2011)] has been implemented in the gyrokinetic code GS2. The results obtained with the code are consistent with several experimental observations, namely the rotation peaking observed after an L-H transition, the rotation reversal observed in Ohmic plasmas, and the change in rotation that follows Lower Hybrid wave injection. ii) The model in [F.I. Parra, M. Barnes and P.J. Catto, Nucl. Fusion 51, 113001 (2011)] has several simplifying assumptions that seem to be satisfied in most tokamaks. To check the importance of these hypotheses, first principles equations that do not rely on these simplifying assumptions have been derived, and a version of these new equations has been implemented in GS2 as well. iii) A tokamak cross-section that drives large intrinsic rotation has been proposed for future large tokamaks. In large tokamaks, intrinsic rotation is expected to be very small unless some up-down asymmetry is introduced. The research conducted under this contract indicates that tilted ellipticity is the most efficient way to drive intrinsic rotation.

  5. Numerical investigations of plasma parameters in the COMPASS tokamak

    SciTech Connect

    Havlickova, E.; Zagorski, R.; Panek, R.

    2008-09-15

    A numerical investigation of plasma parameters in a diverter configuration of COMPASS tokamak is presented. The plasma parameters in the device are analyzed in the frame of the self-consistent description of the central plasma and edge region. The possibility of achieving high recycling and detached regimes in the boundary layer of the COMPASS tokamak is discussed.

  6. Electron cyclotron emission imaging in tokamak plasmas

    SciTech Connect

    Munsat, Tobin; Domier, Calvin W.; Kong, Xiangyu; Liang, Tianran; Luhmann, Jr.; Neville C.; Tobias, Benjamin J.; Lee, Woochang; Park, Hyeon K.; Yun, Gunsu; Classen, Ivo. G. J.; Donne, Anthony J. H.

    2010-07-01

    We discuss the recent history and latest developments of the electron cyclotron emission imaging diagnostic technique, wherein electron temperature is measured in magnetically confined plasmas with two-dimensional spatial resolution. The key enabling technologies for this technique are the large-aperture optical systems and the linear detector arrays sensitive to millimeter-wavelength radiation. We present the status and recent progress on existing instruments as well as new systems under development for future experiments. We also discuss data analysis techniques relevant to plasma imaging diagnostics and present recent temperature fluctuation results from the tokamak experiment for technology oriented research (TEXTOR).

  7. Status of and prospects for advanced tokamak regimes from multi-machine comparisons using the 'International Tokamak Physics Activity' database

    NASA Astrophysics Data System (ADS)

    Litaudon, X.; Barbato, E.; Bécoulet, A.; Doyle, E. J.; Fujita, T.; Gohil, P.; Imbeaux, F.; Sauter, O.; Sips, G.; ITPA Group on Transport; Internal ITB Physics; Connor, J. W.; Doyle, E. J.; Esipchuk, Yu; Fujita, T.; Fukuda, T.; Gohil, P.; Kinsey, J.; Kirneva, N.; Lebedev, S.; Litaudon, X.; Mukhovatov, V.; Rice, J.; Synakowski, E.; Toi, K.; Unterberg, B.; Vershkov, V.; Wakatani, M.; International ITB Database Working Group; Aniel, T.; Baranov, Yu F.; Barbato, E.; Bécoulet, A.; Behn, R.; Bourdelle, C.; Bracco, G.; Budny, R. V.; Buratti, P.; Doyle, E. J.; Esipchuk, Yu; Esposito, B.; Ide, S.; Field, A. R.; Fujita, T.; Fukuda, T.; Gohil, P.; Gormezano, C.; Greenfield, C.; Greenwald, M.; Hahm, T. S.; Hoang, G. T.; Hobirk, J.; Hogeweij, D.; Ide, S.; Isayama, A.; Imbeaux, F.; Joffrin, E.; Kamada, Y.; Kinsey, J.; Kirneva, N.; Litaudon, X.; Luce, T. C.; Murakami, M.; Parail, V.; Peng, Y.-K. M.; Ryter, F.; Sakamoto, Y.; Shirai, H.; Sips, G.; Suzuki, T.; Synakowski, E.; Takenaga, H.; Takizuka, T.; Tala, T.; Wade, M. R.; Weiland, J.

    2004-05-01

    Advanced tokamak regimes obtained in ASDEX Upgrade, DIII-D, FT-U, JET, JT-60U, TCV and Tore Supra experiments are assessed both in terms of their fusion performance and capability for ultimately reaching steady-state using data from the international internal transport barrier database. These advanced modes of tokamak operation are characterized by an improved core confinement and a modified current profile compared to the relaxed Ohmically driven one. The present results obtained in these experiments are studied in view of their prospect for achieving either long pulses ('hybrid' scenario with inductive and non-inductive current drive) or ultimately steady-state purely non-inductive current drive operation in next step devices such as ITER. A new operational diagram for advanced tokamak operation is proposed where the figure of merit characterizing the fusion performances and confinement, H\\times \\beta _{\\rm N}/q^{2}_{95} , is drawn versus the fraction of the plasma current driven by the bootstrap effect. In this diagram, present day advanced tokamak regimes have now reached an operational domain that is required in the non-inductive ITER current drive operation with typically 50% of the plasma current driven by the bootstrap effect (Green et al 2003 Plasma Phys. Control. Fusion 45 587). In addition, the existence domain of the advanced mode regimes is also mapped in terms of dimensionless plasmas physics quantities such as normalized Larmor radius, normalized collisionality, Mach number and ratio of ion to electron temperature. The gap between present day and future advanced tokamak experiments is quantitatively assessed in terms of these dimensionless parameters. A preliminary version of this study was presented in the 29th EPS Conf. on Plasma Phys. and Control. Fusion (Montreux, Switzerland, 17 21 June 2002) [1].

  8. Mathematical modeling plasma transport in tokamaks

    SciTech Connect

    Quiang, Ji

    1995-12-31

    In this work, the author applied a systematic calibration, validation and application procedure based on the methodology of mathematical modeling to international thermonuclear experimental reactor (ITER) ignition studies. The multi-mode plasma transport model used here includes a linear combination of drift wave branch and ballooning branch instabilities with two a priori uncertain constants to account for anomalous plasma transport in tokamaks. A Bayesian parameter estimation method is used including experimental calibration error/model offsets and error bar rescaling factors to determine the two uncertain constants in the transport model with quantitative confidence level estimates for the calibrated parameters, which gives two saturation levels of instabilities. This method is first tested using a gyroBohm multi-mode transport model with a pair of DIII-D discharge experimental data, and then applied to calibrating a nominal multi-mode transport model against a broad database using twelve discharges from seven different tokamaks. The calibrated transport model is then validated on five discharges from JT-60 with no adjustable constants. The results are in a good agreement with experimental data. Finally, the resulting class of multi-mode tokamak plasma transport models is applied to the transport analysis of the ignition probability in a next generation machine, ITER. A reference simulation of basic ITER engineering design activity (EDA) parameters shows that a self-sustained thermonuclear burn with 1.5 GW output power can be achieved provided that impurity control makes radiative losses sufficiently small at an average plasma density of 1.2 X 10{sup 20}/m{sup 3} with 50 MW auxiliary heating. The ignition probability of ITER for the EDA parameters, can be formally as high as 99.9% in the present context. The same probability for concept design activity (CDA) parameters of ITER, which has smaller size and lower current, is only 62.6%.

  9. Plasma engineering analysis of Tennessee Tokamak

    SciTech Connect

    Yokoyama, K.E.; Lacatski, J.T.; Miller, J.B.; Bryan, W.E.; King, P.W.; Santoro, R.T.; Shannon, T.E.; Uckan, N.A.

    1983-01-01

    This paper summarizes the results of the plasma engineering and systems analysis studies for the Tennessee Tokamak (TENTOK) fusion power reactor. TENTOK is a 3000-MW(t) central station power plant that uses dueterium-tritium fuel in a D-shaped tokamak plasma configuration with a double-null poloidal divertor. Detailed analyses are performed in the areas of (1) transport simulation using the 1-1/2-D WHIST transport code, (2) equilibrium/poloidal field coil systems, (3) neutral beam and radiofrequency (rf) heating, and (4) pellet fueling. In addition, impurity control sytems, diagnostics and controls, and possible microwave plasma preheating and steady-state current drive options are also considered. Some of the major features of TENTOK include rf heating in the ion cyclotron range of frequencies, superconducting equilibrium field coils outside the superconducting toroidal field coils, a double-null poloidal divertor for impurity control and alpha ash removal, and rf-assisted plasma preheating and current startup.

  10. Viscosity in the edge of tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Stacey, W. M.

    1993-05-01

    A fluid representation of viscosity has been incorporated into a set of fluid equations that are maximally ordered in the 'short radial gradient scale length' (srgsl) ordering that is appropriate for the edge of tokamak plasmas. The srgsl ordering raises viscous drifts and other viscous terms to leading order and fundamentally alters the character of the fluid equations. A leasing order viscous drift is identified. Viscous-driven radial particle and energy fluxes in the scrape-off layer and divertor channel are estimated to have an order unity effect in reducing radial peaking of energy fluxes transported along the field lines to divertor collector plates.

  11. Magnetic field measurements in tokamak plasmas

    SciTech Connect

    Feldman, U.; Seely, J.F.; Sheeley,Jr., N.R.; Suckewer, S.; Title, A.M.

    1984-11-01

    The measurement of the poloidal magnetic field in a tokamak plasma from the Zeeman splitting and polarization of the magnetic dipole radiation from heavy ions is discussed. When viewed from a direction perpendicular to the toroidal field, the effect of the poloidal field on the circularly polarized radiation is detectable using a photoelectric polarimeter. The Zeeman splittings for a number of magnetic dipole transitions with wavelengths in the range 2300--9300 A are presented. An imaging polarimeter is proposed that can measure the poloidal magnetic field with space and time resolution.

  12. Neoclassical Transport Properties of Tokamak Plasmas

    SciTech Connect

    Weyssow, B.

    2004-03-15

    The classical transport theory is strictly valid for a plasma in a homogeneous and stationary magnetic field. In the '60, experiments have shown that this theory does not apply as a local theory of transport in Tokamaks. It was shown that global geometric characteristics of the confining elements have a strong influence on the transport. Three regimes of collisionality are characteristic of the neoclassical transport theory: the banana regime (the electronic diffusion coefficient increases starting from zero), the plateau regime (the diffusion coefficient is almost independent of the collisionality) and the Pfirsch-Schlueter regime (the electronic diffusion coefficient again increases with the collisionality)

  13. Neoclassical diffusion of heavy impurities in a rotating tokamak plasma

    SciTech Connect

    Wong, K.L.; Cheng, C.Z.

    1987-08-01

    Particle orbits in a rotating tokamak plasma are calculated from the equation of motion in the frame that rotates with the plasma. It is found that heavy particles in a rotating plasma can drift away from magnetic surfaces significantly faster, resulting in a diffusion coefficient much larger than that for a stationary plasma. Particle simulation is carried out and the results offer a qualitative explanation for some experimental data from the Tokamak Test Reactor (TFTR). 13 refs., 2 figs.

  14. Controlling sawtooth oscillations in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Chapman, I. T.

    2011-01-01

    The sawtooth instability in tokamak plasmas results in a periodic reorganization of the core plasma. A typical sawtooth cycle consists of a quiescent period, during which the plasma density and temperature increase, followed by the growth of a helical magnetic perturbation, which in turn is followed by a rapid collapse of the central pressure. The stabilizing effects of fusion-born α particles are likely to lead to long sawtooth periods in burning plasmas. However, sawteeth with long quiescent periods have been observed to result in the early triggering of neo-classical tearing modes (NTMs) at low plasma pressure, which can, in turn, significantly degrade confinement. Consequently, recent experiments have identified various methods to deliberately control sawtooth oscillations in an attempt to avoid seeding NTMs whilst retaining the benefits of small, frequent sawteeth, such as the prevention of core impurity accumulation. Sawtooth control actuators include current drive schemes, such as electron cyclotron current drive, and tailoring the fast ion population in the plasma using neutral beam injection or ion cyclotron resonance heating.

  15. Nonlinear lower hybrid modeling in tokamak plasmas

    SciTech Connect

    Napoli, F.; Schettini, G.; Castaldo, C.; Cesario, R.

    2014-02-12

    We present here new results concerning the nonlinear mechanism underlying the observed spectral broadening produced by parametric instabilities occurring at the edge of tokamak plasmas in present day LHCD (lower hybrid current drive) experiments. Low frequency (LF) ion-sound evanescent modes (quasi-modes) are the main parametric decay channel which drives a nonlinear mode coupling of lower hybrid (LH) waves. The spectrum of the LF fluctuations is calculated here considering the beating of the launched LH wave at the radiofrequency (RF) operating line frequency (pump wave) with the noisy background of the RF power generator. This spectrum is calculated in the frame of the kinetic theory, following a perturbative approach. Numerical solutions of the nonlinear LH wave equation show the evolution of the nonlinear mode coupling in condition of a finite depletion of the pump power. The role of the presence of heavy ions in a Deuterium plasma in mitigating the nonlinear effects is analyzed.

  16. Plasma rotation in the PDX tokamak

    SciTech Connect

    Brau, K.; Bitter, M.; Goldston, R.J.; Manos, D.; McGuire, K.; Suckewer, S.

    1983-06-01

    Toroidal and poloidal rotation has been measured in the Poloidal Divertor Experiment (PDX) tokamak in ohmic- and neutral-beam-heated plasmas in a variety of discharge conditions and in both circular and diverted configurations. Rotation velocities were deduced from Doppler shifts of magnetic dipole (M1) lines and lines of optically allowed transitions in the visible and uv regions, from K/sub ..cap alpha../ emission, and also from an array of magnetic pickup loops. Poloidal and toroidal rotation velocities in ohmically heated discharges were unusually less than 3 x 10/sup 5/ cm/sec. Near the plasma edge the toroidal-rotation velocity varies with poloidal angle both before and during neutral-beam injection. No systematic poloidal rotation was observed during neutral-beam injection centered about or displaced 10 cm from the horizontal midplane, which implies that the poloidal damping time tau/sub theta/ < 0.5 tau/sub ii/, consistent with theoretical estimates.

  17. Plasma diagnostics for the compact ignition tokamak

    SciTech Connect

    Medley, S.S.; Young, K.M.

    1988-06-01

    The primary mission of the Compact Ignition Tokamak (CIT) is to study the physics of alpha-particle heating in an ignited D-T plasma. A burn time of about 10 /tau//sub E/ is projected in a divertor configuration with baseline machine design parameters of R=2.10 m, 1=0.65 m, b=1.30 m, I/sub p/=11 MA, B/sub T/=10 T and 10-20 MW of auxiliary rf heating. Plasma temperatures and density are expected to reach T/sub e/(O) /approximately/20 keV, T/sub i/(O) /approximately/30 keV, and n/sub e/(O) /approximately/ 1 /times/ 10/sup 21/m/sup /minus/3/. The combined effects of restricted port access to the plasma, the presence of severe neutron and gamma radiation backgrounds, and the necessity for remote of in-cell components create challenging design problems for all of the conventional diagnostic associated with tokamak operations. In addition, new techniques must be developed to diagnose the evolution in space, time, and energy of the confined alpha distribution as well as potential plasma instabilities driven by collective alpha-particle effects. The design effort for CIT diagnostics is presently in the conceptual phase with activity being focused on the selection of a viable diagnostic set and the identification of essential research and development projects to support this process. A review of these design issues and other aspects impacting the selection of diagnostic techniques for the CIT experiment will be presented. 28 refs., 10 figs., 2 tabs.

  18. A simulation study of a controlled tokamak plasma

    NASA Astrophysics Data System (ADS)

    Fujii, N.; Niwa, Y.

    1980-03-01

    A tokamak circuit theory, including results of numerical simulation studies, is applied to a control system synthesized for a Joule heated tokamak plasma. The treatment is similar to that of Ogata and Ninomiya (1979) except that in this case a quadrupole field coil current is considered coexisting with image induced on a vacuum chamber.

  19. Transport Bifurcation in a Rotating Tokamak Plasma

    SciTech Connect

    Highcock, E. G.; Barnes, M.; Schekochihin, A. A.; Parra, F. I.; Roach, C. M.; Cowley, S. C.

    2010-11-19

    The effect of flow shear on turbulent transport in tokamaks is studied numerically in the experimentally relevant limit of zero magnetic shear. It is found that the plasma is linearly stable for all nonzero flow shear values, but that subcritical turbulence can be sustained nonlinearly at a wide range of temperature gradients. Flow shear increases the nonlinear temperature gradient threshold for turbulence but also increases the sensitivity of the heat flux to changes in the temperature gradient, except over a small range near the threshold where the sensitivity is decreased. A bifurcation in the equilibrium gradients is found: for a given input of heat, it is possible, by varying the applied torque, to trigger a transition to significantly higher temperature and flow gradients.

  20. DIII-D Advanced Tokamak Research Overview

    SciTech Connect

    V.S. Chan; C.M. Greenfield; L.L. Lao; T.C. Luce; C.C. Petty; G.M. Staebler

    1999-12-01

    This paper reviews recent progress in the development of long-pulse, high performance discharges on the DIII-D tokamak. It is highlighted by a discharge achieving simultaneously {beta}{sub N}H of 9, bootstrap current fraction of 0.5, noninductive current fraction of 0.75, and sustained for 16 energy confinement times. The physics challenge has changed in the long-pulse regime. Non-ideal MHD modes are limiting the stability, fast ion driven modes may play a role in fast ion transport which limits the stored energy and plasma edge behavior can affect the global performance. New control tools are being developed to address these issues.

  1. Filterscope diagnostic system on the Experimental Advanced Superconducting Tokamak (EAST)

    NASA Astrophysics Data System (ADS)

    Xu, Z.; Wu, Z. W.; Gao, W.; Chen, Y. J.; Wu, C. R.; Zhang, L.; Huang, J.; Chang, J. F.; Yao, X. J.; Gao, W.; Zhang, P. F.; Jin, Z.; Hou, Y. M.; Guo, H. Y.

    2016-11-01

    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 Dα (656.1 nm), Dγ (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 crucial 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.

  2. Advanced ICRF antenna design for R-TOKAMAK

    NASA Astrophysics Data System (ADS)

    Kako, E.; Ando, R.; Ichimura, M.; Ogawa, Y.; Amano, T.; Watari, T.

    1986-01-01

    The advanced ICRF antennas designed for the R-TOKAMAK (a proposal in the Institute of Plasma Physics, Nagoya University) are described. They are a standard loop antenna and a panel heater antenna for fast wave heating, and a waveguide antenna for ion Bernstein wave heating. The standard loop antenna is made of Al-alloy and has a simple structure to install because of radioactivation by D-T neutrons. For high power heating, a new type antenna called Panel heater antenna is proposed. It has a wide radiation area and is able to select a parallel wave number k. The field pattern of the panel heater antenna is measured. The feasibility of the waveguide antenna is discussed for ion Bernstein wave heating. The radiation from the aperture of the double ridge waveguide is experimentally estimated with a load simulating the plasma.

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

    NASA Astrophysics Data System (ADS)

    Seo, Seong-Heon; Park, Jinhyung; Wi, H. M.; Lee, W. R.; Kim, H. S.; Lee, T. G.; Kim, Y. S.; Kang, Jin-Seob; Bog, M. G.; Yokota, Y.; Mase, A.

    2013-08-01

    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 × 1019 m-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 of 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.

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

    SciTech Connect

    Seo, Seong-Heon; Wi, H. M.; Lee, W. R.; Kim, H. S.; Lee, T. G.; Kim, Y. S.; Park, Jinhyung; Kang, Jin-Seob; Bog, M. G.; Yokota, Y.; Mase, A.

    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 of 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.

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

    SciTech Connect

    Khorshid, Pejman; Wang, L.; Ghoranneviss, M.; Arvin, R.; Dorranian, D.; Talebitaher, A.; Salem, M. K.; Abhari, A.

    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, 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.

  6. Status of neutron diagnostics on the experimental advanced superconducting tokamak

    NASA Astrophysics Data System (ADS)

    Zhong, G. Q.; Hu, L. Q.; Pu, N.; Zhou, R. J.; Xiao, M.; Cao, H. R.; Zhu, Y. B.; Li, K.; Fan, T. S.; Peng, X. Y.; Du, T. F.; Ge, L. J.; Huang, J.; Xu, G. S.; Wan, B. N.

    2016-11-01

    Neutron diagnostics have become a significant means to study energetic particles in high power auxiliary heating plasmas on the Experimental Advanced Superconducting Tokamak (EAST). Several kinds of neutron diagnostic systems have been implemented for time-resolved measurements of D-D neutron flux, fluctuation, emission profile, and spectrum. All detectors have been calibrated in laboratory, and in situ calibration using 252Cf neutron source in EAST is in preparation. A new technology of digitized pulse signal processing is adopted in a wide dynamic range neutron flux monitor, compact recoil proton spectrometer, and time of flight spectrometer. Improvements will be made continuously to the system to achieve better adaptation to the EAST's harsh γ-ray and electro-magnetic radiation environment.

  7. Diagnosing transient plasma status: from solar atmosphere to tokamak divertor

    NASA Astrophysics Data System (ADS)

    Giunta, A. S.; Henderson, S.; O'Mullane, M.; Harrison, J.; Doyle, J. G.; Summers, H. P.

    2016-09-01

    This work strongly exploits the interdisciplinary links between astrophysical (such as the solar upper atmosphere) and laboratory plasmas (such as tokamak devices) by sharing the development of a common modelling for time-dependent ionisation. This is applied to the interpretation of solar flare data observed by the UVSP (Ultraviolet Spectrometer and Polarimeter), on-board the Solar Maximum Mission and the IRIS (Interface Region Imaging Spectrograph), and also to data from B2-SOLPS (Scrape Off Layer Plasma Simulations) for MAST (Mega Ampère Spherical Tokamak) Super-X divertor upgrade. The derived atomic data, calculated in the framework of the ADAS (Atomic Data and Analysis Structure) project, allow equivalent prediction in non-stationary transport regimes and transients of both the solar atmosphere and tokamak divertors, except that the tokamak evolution is about one thousand times faster.

  8. The ARIES Advanced And Conservative Tokamak (ACT) Power Plant Study

    SciTech Connect

    Kessel, C. E.; Poli, F. M.; Ghantous, K.; Gorelenkov, N.; Tillack, M. S.; Najmabadi, F.; Wang, X. R.; Navaei, D.; Toudeshki, H. H.; Koehly, C.; El-Guebaly, L.; Blanchard, J. P.; Martin, C. J.; Mynsburge, L.; Humrickhouse, P.; Rensink, M. E.; Rognlien, T. D.; Yoda, M.; Abdel-Khalik, S. I.; Hageman, M. D.; Mills, B. H.; Radar, J. D.; Sadowski, D. L.; Snyder, P. B.; St. John, H.; Turnbull, A. D.; Waganer, L. M.; Malang, S.; Rowcliffe, A. F.

    2014-03-05

    Tokamak power plants are studied with advanced and conservative design philosophies in order 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 to older studies. The advanced configuration assumes a self-cooled lead lithium (SCLL) 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, a {beta}N{sup total} of 5.75, H{sub 98} of 1.65, n/nGr of 1.0, and peak divertor heat flux of 13.7 MW/m{sup 2}. The conservative configuration assumes a dual coolant lead lithium (DCLL) blanket concept with ferritic steel structural material and helium coolant, achieving a thermal conversion efficiency of 45%. The plasma major radius is 9.75 m, a toroidal field of 8.75 T, a q95 of 8.0, a {beta}N{sup total} of 2.5, H{sub 98} of 1.25, n/n{sub Gr} of 1.3, and peak divertor heat flux of 10 MW/m{sup 2}. 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 of 10-15 MW/m{sup 2}. 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. Papers in this issue provide more detailed discussion of the work summarized here.

  9. The ARIES Advanced and Conservative Tokamak Power Plant Study

    SciTech Connect

    Kessel, C. E; Tillak, M. S; Najmabadi, F.; Poli, F. M.; Ghantous, K.; Gorelenkov, N.; Wang, X. R.; Navaei, D.; Toudeshki, H. H.; Koehly, C.; EL-Guebaly, L.; Blanchard, J. P.; Martin, C. J.; Mynsburge, L.; Humrickhouse, P.; Rensink, M. E.; Rognlien, T. D.; Yoda, M.; Abdel-Khalik, S. I.; Hageman, M. D.; Mills, B. H.; Rader, J. D.; Sadowski, D. L.; Snyder, P. B.; St. John, H.; Turnbull, A. D.; Waganer, L. M.; Malang, S.; Rowcliffe, A. 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, aᵦtotal N of 5.75, an H98 of 1.65, an n/nGr 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, aᵦtotalN of 2.5, an H₉₈ of 1.25, an n/nGr 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.

  10. The ARIES Advanced and Conservative Tokamak Power Plant Study

    DOE PAGES

    Kessel, C. E; Tillak, M. S; Najmabadi, F.; Poli, F. M.; Ghantous, K.; Gorelenkov, N.; Wang, X. R.; Navaei, D.; Toudeshki, H. H.; Koehly, C.; et al

    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, aᵦtotal N of 5.75, an H98 of 1.65, anmore » n/nGr 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, aᵦtotalN of 2.5, an H₉₈ of 1.25, an n/nGr 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

  11. Designing a tokamak fusion reactor—How does plasma physics fit in?

    NASA Astrophysics Data System (ADS)

    Freidberg, J. P.; Mangiarotti, F. J.; Minervini, J.

    2015-07-01

    This paper attempts to bridge the gap between tokamak reactor design and plasma physics. The analysis demonstrates that the overall design of a tokamak fusion reactor is determined almost entirely by the constraints imposed by nuclear physics and fusion engineering. Virtually, no plasma physics is required to determine the main design parameters of a reactor: a , R 0 , B 0 , T i , T e , p , n , τ E , I . The one exception is the value of the toroidal current I , which depends upon a combination of engineering and plasma physics. This exception, however, ultimately has a major impact on the feasibility of an attractive tokamak reactor. The analysis shows that the engineering/nuclear physics design makes demands on the plasma physics that must be satisfied in order to generate power. These demands are substituted into the well-known operational constraints arising in tokamak physics: the Troyon limit, Greenwald limit, kink stability limit, and bootstrap fraction limit. Unfortunately, a tokamak reactor designed on the basis of standard engineering and nuclear physics constraints does not scale to a reactor. Too much current is required to achieve the necessary confinement time for ignition. The combination of achievable bootstrap current plus current drive is not sufficient to generate the current demanded by the engineering design. Several possible solutions are discussed in detail involving advances in plasma physics or engineering. The main contribution of the present work is to demonstrate that the basic reactor design and its plasma physics consequences can be determined simply and analytically. The analysis thus provides a crisp, compact, logical framework that will hopefully lead to improved physical intuition for connecting plasma physic to tokamak reactor design.

  12. A Midsize Tokamak As Fast Track To Burning Plasmas

    SciTech Connect

    E. Mazzucato

    2010-07-14

    This paper presents a midsize tokamak as a fast track to the investigation of burning plasmas. It is shown that it could reach large values of energy gain (≥10) with only a modest improvement in confinement over the scaling that was used for designing the International Thermonuclear Experimental Reactor (ITER). This could be achieved by operating in a low plasma recycling regime that experiments indicate can lead to improved plasma confinement. The possibility of reaching the necessary conditions of low recycling using a more efficient magnetic divertor than those of present tokamaks is discussed.

  13. Self-suppression of double tearing modes via Alfven resonance in rotating tokamak plasmas

    SciTech Connect

    Wang Zhengxiong; Wei Lai; Liu Yue; Wang Xiaogang

    2011-05-15

    Reversed magnetic shear configuration, a key method for improving plasma confinement in advanced tokamaks, is prone to exciting double tearing modes (DTMs) that can severely degrade the plasma confinement. In this letter, we reveal a new mechanism of suppressing the DTM instability due to the self-induced Alfven resonance in rotating tokamak plasmas. The linear growth rate is reduced from {approx}S{sub Hp}{sup -1/3} of the fast DTM regime to {approx}S{sub Hp}{sup -3/5} of the slow single tearing mode regime, where S{sub Hp} is magnetic Reynolds number. Instead of generating magnetic islands at the inner rational surface that can greatly enhance plasma transport in the core region, the formation of current sheets at resonance layers not only prevents the fast nonlinear DTM reconnection phase but also contributes to plasma heating.

  14. Long-wavelength turbulence measurements in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Fonck, Raymond

    1999-11-01

    A quantum jump in our understanding of turbulence in magnetically confined plasmas has been driven by advances in both plasma theory and diagnostic capabilities. Beam Emission Spectroscopy, reflectometry, and microwave scattering provide increasingly detailed measurements of tokamak plasma turbulence, especially for long wavelength (i.e., larger than the ion gyroradius) modes. Measurements of amplitudes and spatial and temporal correlation properties are consistent with this turbulence causing the ion transport observed in standard confinement regimes such as L-mode and hot-ion regimes. Radial and poloidal spectra are in good agreement with those calculated in theoretical gyrokinetic simulations. A signature characteristic of ion temperature gradient driven turbulence is the prediction of relatively large ion thermal fluctuations, which has been confirmed to exist in experiment and establishes ITG turbulence as the dominant mechanism in the ion channel. This identification has been reinforced by the reduction of turbulence in the presence of shear flow stabilization. At both the plasma edge region (H-mode) and the hot plasma interior (Internal Transport Barrier), a drop in local turbulence and transport is observed when the local flow-induced shearing rate exceeds the calculated growth rate of the most unstable modes. Advances in challenging theory will require new experimental techniques: nonlinear spectral analysis to provide experimentally determined growth rates; 2-D visualization of the density turbulence via several proposed techniques; and high time resolution measurements to provide details on intermittency. New correlation techniques may allow measurement of flow velocity fluctuations. This in turn may allow study of zonal flows and/or fluctuations in the local electrostatic potential.

  15. Stochastic modeling of plasma mode forecasting in tokamak

    NASA Astrophysics Data System (ADS)

    Saadat, Sh.; Salem, M.; Ghoranneviss, M.; Khorshid, P.

    2012-04-01

    The structure of magnetohydrodynamic (MHD) modes has always been an interesting study in tokamaks. The mode number of tokamak plasma is the most important parameter, which plays a vital role in MHD instabilities. If it could be predicted, then the time of exerting external fields, such as feedback fields and Resonance Helical Field, could be obtained. Autoregressive Integrated Moving Average (ARIMA) and Seasonal Autoregressive Integrated Moving Average are useful models to predict stochastic processes. In this paper, we suggest using ARIMA model to forecast mode number. The ARIMA model shows correct mode number (m = 4) about 0.5 ms in IR-T1 tokamak and equations of Mirnov coil fluctuations are obtained. It is found that the recursive estimates of the ARIMA model parameters change as the plasma mode changes. A discriminator function has been proposed to determine plasma mode based on the recursive estimates of model parameters.

  16. Radial and poloidal correlation reflectometry on Experimental Advanced Superconducting Tokamak

    SciTech Connect

    Qu, Hao; Zhang, Tao; Han, Xiang; Wen, Fei; Zhang, Shoubiao; Kong, Defeng; Wang, Yumin; Gao, Yu; Huang, Canbin; Cai, Jianqing; Gao, Xiang

    2015-08-15

    An X-mode polarized V band (50 GHz–75 GHz) radial and poloidal correlation reflectometry is designed and installed on Experimental Advanced Superconducting Tokamak (EAST). Two frequency synthesizers (12 GHz–19 GHz) are used as sources. Signals from the sources are up-converted to V band using active quadruplers and then coupled together for launching through one single pyramidal antenna. Two poloidally separated antennae are installed to receive the reflected waves from plasma. This reflectometry system can be used for radial and poloidal correlation measurement of the electron density fluctuation. In ohmically heated plasma, the radial correlation length is about 1.5 cm measured by the system. The poloidal correlation analysis provides a means to estimate the fluctuation velocity perpendicular to the main magnetic field. In the present paper, the distance between two poloidal probing points is calculated with ray-tracing code and the propagation time is deduced from cross-phase spectrum. Fluctuation velocity perpendicular to the main magnetic field in the core of ohmically heated plasma is about from −1 km/s to −3 km/s.

  17. Radial and poloidal correlation reflectometry on Experimental Advanced Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Qu, Hao; Zhang, Tao; Han, Xiang; Wen, Fei; Zhang, Shoubiao; Kong, Defeng; Wang, Yumin; Gao, Yu; Huang, Canbin; Cai, Jianqing; Gao, Xiang

    2015-08-01

    An X-mode polarized V band (50 GHz-75 GHz) radial and poloidal correlation reflectometry is designed and installed on Experimental Advanced Superconducting Tokamak (EAST). Two frequency synthesizers (12 GHz-19 GHz) are used as sources. Signals from the sources are up-converted to V band using active quadruplers and then coupled together for launching through one single pyramidal antenna. Two poloidally separated antennae are installed to receive the reflected waves from plasma. This reflectometry system can be used for radial and poloidal correlation measurement of the electron density fluctuation. In ohmically heated plasma, the radial correlation length is about 1.5 cm measured by the system. The poloidal correlation analysis provides a means to estimate the fluctuation velocity perpendicular to the main magnetic field. In the present paper, the distance between two poloidal probing points is calculated with ray-tracing code and the propagation time is deduced from cross-phase spectrum. Fluctuation velocity perpendicular to the main magnetic field in the core of ohmically heated plasma is about from -1 km/s to -3 km/s.

  18. Radial and poloidal correlation reflectometry on Experimental Advanced Superconducting Tokamak.

    PubMed

    Qu, Hao; Zhang, Tao; Han, Xiang; Wen, Fei; Zhang, Shoubiao; Kong, Defeng; Wang, Yumin; Gao, Yu; Huang, Canbin; Cai, Jianqing; Gao, Xiang

    2015-08-01

    An X-mode polarized V band (50 GHz-75 GHz) radial and poloidal correlation reflectometry is designed and installed on Experimental Advanced Superconducting Tokamak (EAST). Two frequency synthesizers (12 GHz-19 GHz) are used as sources. Signals from the sources are up-converted to V band using active quadruplers and then coupled together for launching through one single pyramidal antenna. Two poloidally separated antennae are installed to receive the reflected waves from plasma. This reflectometry system can be used for radial and poloidal correlation measurement of the electron density fluctuation. In ohmically heated plasma, the radial correlation length is about 1.5 cm measured by the system. The poloidal correlation analysis provides a means to estimate the fluctuation velocity perpendicular to the main magnetic field. In the present paper, the distance between two poloidal probing points is calculated with ray-tracing code and the propagation time is deduced from cross-phase spectrum. Fluctuation velocity perpendicular to the main magnetic field in the core of ohmically heated plasma is about from -1 km/s to -3 km/s.

  19. The Numerical Tokamak Project (NTP) simulation of turbulent transport in the core plasma: A grand challenge in plasma physics

    SciTech Connect

    Not Available

    1993-12-01

    The long-range goal of the Numerical Tokamak Project (NTP) is the reliable prediction of tokamak performance using physics-based numerical tools describing tokamak physics. The NTP is accomplishing the development of the most advanced particle and extended fluid model`s on massively parallel processing (MPP) environments as part of a multi-institutional, multi-disciplinary numerical study of tokamak core fluctuations. The NTP is a continuing focus of the Office of Fusion Energy`s theory and computation program. Near-term HPCC work concentrates on developing a predictive numerical description of the core plasma transport in tokamaks driven by low-frequency collective fluctuations. This work addresses one of the greatest intellectual challenges to our understanding of the physics of tokamak performance and needs the most advanced computational resources to progress. We are conducting detailed comparisons of kinetic and fluid numerical models of tokamak turbulence. These comparisons are stimulating the improvement of each and the development of hybrid models which embody aspects of both. The combination of emerging massively parallel processing hardware and algorithmic improvements will result in an estimated 10**2--10**6 performance increase. Development of information processing and visualization tools is accelerating our comparison of computational models to one another, to experimental data, and to analytical theory, providing a bootstrap effect in our understanding of the target physics. The measure of success is the degree to which the experimentally observed scaling of fluctuation-driven transport may be predicted numerically. The NTP is advancing the HPCC Initiative through its state-of-the-art computational work. We are pushing the capability of high performance computing through our efforts which are strongly leveraged by OFE support.

  20. (High beta tokamak research and plasma theory)

    SciTech Connect

    Not Available

    1990-01-01

    Our activities on High Beta Tokamak Research during the past 12 months of the present budget period can be divided into four areas: completion of kink mode studies in HBT; completion of carbon impurity transport studies in HBT; design of HBT-EP; and construction of HBT-EP. Each of these is described briefly in the sections of this progress report.

  1. Stabilization of tokamak plasma by lithium streams

    SciTech Connect

    L.E. Zakharov

    2000-08-07

    The stabilization theory of free-boundary magnetohydrodynamic instabilities in tokamaks by liquid lithium streams driven by magnetic propulsion is formulated. While the conventional, wall-locked, resistive wall mode can be well suppressed by the flow, a new, stream-locked mode determines the limits of the flow stabilization.

  2. Experimental observations of driven and intrinsic rotation in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Rice, J. E.

    2016-08-01

    Experimental observations of driven and intrinsic rotation in tokamak plasmas are reviewed. For momentum sources, there is direct drive from neutral beam injection, lower hybrid and ion cyclotron range of frequencies waves (including mode conversion flow drive), as well as indirect \\mathbf{j}× \\mathbf{B} forces from fast ion and electron orbit shifts, and toroidal magnetic field ripple loss. Counteracting rotation drive are sinks, such as from neutral drag and toroidal viscosity. Many of these observations are in agreement with the predictions of neo-classical theory while others are not, and some cases of intrinsic rotation remain puzzling. In contrast to particle and heat fluxes which depend on the relevant diffusivity and convection, there is an additional term in the momentum flux, the residual stress, which can act as the momentum source for intrinsic rotation. This term is independent of the velocity or its gradient, and its divergence constitutes an intrinsic torque. The residual stress, which ultimately responds to the underlying turbulence, depends on the confinement regime and is a complicated function of collisionality, plasma shape, and profiles of density, temperature, pressure and current density. This leads to the rich intrinsic rotation phenomenology. Future areas of study include integration of these many effects, advancement of quantitative explanations for intrinsic rotation and development of strategies for velocity profile control.

  3. On steady poloidal and toroidal flows in tokamak plasmas

    SciTech Connect

    McClements, K. G.

    2010-08-15

    The effects of poloidal and toroidal flows on tokamak plasma equilibria are examined in the magnetohydrodynamic limit. ''Transonic'' poloidal flows of the order of the sound speed multiplied by the ratio of poloidal magnetic field to total field B{sub {theta}/}B can cause the (normally elliptic) Grad-Shafranov (GS) equation to become hyperbolic in part of the solution domain. It is pointed out that the range of poloidal flows for which the GS equation is hyperbolic increases with plasma beta and B{sub {theta}/}B, thereby complicating the problem of determining spherical tokamak plasma equilibria with transonic poloidal flows. It is demonstrated that the calculation of the hyperbolicity criterion can be easily modified when the assumption of isentropic flux surfaces is replaced with the more tokamak-relevant one of isothermal flux surfaces. On the basis of the latter assumption, a simple expression is obtained for the variation of density on a flux surface when poloidal and toroidal flows are simultaneously present. Combined with Thomson scattering measurements of density and temperature, this expression could be used to infer information on poloidal and toroidal flows on the high field side of a tokamak plasma, where direct measurements of flows are not generally possible. It is demonstrated that there are four possible solutions of the Bernoulli relation for the plasma density when the flux surfaces are assumed to be isothermal, corresponding to four distinct poloidal flow regimes. Finally, observations and first principles-based theoretical modeling of poloidal flows in tokamak plasmas are briefly reviewed and it is concluded that there is no clear evidence for the occurrence of supersonic poloidal flows.

  4. Modelling multi-ion plasma gun simulations of Tokamak disruptions

    SciTech Connect

    Ehst, D.A.

    1995-08-01

    The effect of impurity ions in plasma gun ablation tests of various targets is considered. Inclusion of reasonable amounts of impurity ({approximately}10%) is adequate to explain observed energy transmission and erosion measurements. The gun tests and the computer code calculations are relevant to the parameter range expected for major disruptions on large tokamaks.

  5. Dust-Particle Transport in Tokamak Edge Plasmas

    SciTech Connect

    Pigarov, A Y; Krasheninnikov, S I; Soboleva, T K; Rognlien, T D

    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 comprehensive 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.

  6. Analytic model for coaxial helicity injection in tokamak plasmas

    SciTech Connect

    Weening, R. H.

    2011-12-15

    Using a partial differential equation for the time evolution of the mean-field poloidal magnetic flux that incorporates resistivity {eta} and hyper-resistivity {Lambda} terms, an exact analytic solution is obtained for steady-state coaxial helicity injection (CHI) in force-free large aspect ratio tokamaks. The analytic mean-field Ohm's law model allows for calculation of the tokamak CHI current drive efficiency and the plasma inductances at arbitrary levels of magnetic fluctuations, or dynamo activity. The results of the mean-field model suggest that CHI approaching Ohmic efficiency is only possible in tokamaks when the size of the effective current drive boundary layer, {delta}{identical_to}({Lambda}/{eta}){sup 1/2}, becomes greater than half the size of the plasma, {delta}>a/2, with a the plasma minor radius. The electron thermal diffusivity due to magnetic fluctuation induced transport is obtained from the expression {chi}{sub e}={Lambda}/{mu}{sub 0}d{sub e}{sup 2}, with {mu}{sub 0} the permeability of free space and d{sub e} the electron skin depth, which for typical tokamak fusion plasma parameters is on the order of a millimeter. Thus, the ratio of the energy confinement time to the resistive diffusion time in a tokamak plasma driven by steady-state CHI approaching Ohmic efficiency is shown to be constrained by the relation {tau}{sub E}/{tau}{sub {eta}}<(d{sub e}/a){sup 2}{approx_equal}10{sup -6}. The mean-field model suggests that steady-state CHI can be viewed most simply as a boundary layer of stochastically wandering magnetic field lines.

  7. Problems with the concept of plasma equilibrium in tokamaks

    SciTech Connect

    Carreras, B.A.

    1992-06-01

    The equilibrium condition for a magnetically confined plasma in normally formulated in terms of macroscopic equations. In these equations, the plasma pressure is assumed to be a function of the magnetic flux with continuous derivatives. However, in three- dimensional systems this is not necessarily the case. Here, we look at the case of an intrinsically three-dimensional realistic tokamak, and we discuss the possible interconnection between the equilibrium and anomalous transport.

  8. 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.

  9. Disruption avoidance through active magnetic feedback in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Paccagnella, Roberto; Zanca, Paolo; Yanovskiy, Vadim; Finotti, Claudio; Manduchi, Gabriele; Piron, Chiara; Carraro, Lorella; Franz, Paolo; RFX Team

    2014-10-01

    Disruptions avoidance and mitigation is a fundamental need for a fusion relevant tokamak. In this paper a new experimental approach for disruption avoidance using active magnetic feedback is presented. This scheme has been implemented and tested on the RFX-mod device operating as a circular tokamak. RFX-mod has a very complete system designed for active mode control that has been proved successful for the stabilization of the Resistive Wall Modes (RWMs). In particular the current driven 2/1 mode, unstable when the edge safety factor, qa, is around (or even less than) 2, has been shown to be fully and robustly stabilized. However, at values of qa (qa > 3), the control of the tearing 2/1 mode has been proved difficult. These results suggested the idea to prevent disruptions by suddenly lowering qa to values around 2 where the tearing 2/1 is converted to a RWM. Contrary to the universally accepted idea that the tokamaks should disrupt at low qa, we demonstrate that in presence of a well designed active control system, tokamak plasmas can be driven to low qa actively stabilized states avoiding plasma disruption with practically no loss of the plasma internal energy.

  10. 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.

  11. Pseudo-MHD ballooning modes in tokamak plasmas

    SciTech Connect

    Callen, J.D.; Hegna, C.C.

    1996-08-01

    The MHD description of a plasma is extended to allow electrons to have both fluid-like and adiabatic-regime responses within an instability eigenmode. In the resultant {open_quotes}pseudo-MHD{close_quotes} model, magnetic field line bending is reduced in the adiabatic electron regime. This makes possible a new class of ballooning-type, long parallel extent, MHD-like instabilities in tokamak plasmas for {alpha} > s{sup 2}(2 {sup 7/3}/9) (r{sub p}/R{sub 0}) or-d{radical}{Beta}/dr > (2{sup 1/6} /3)(s/ R{sub 0q}), which is well below the ideal-MHD stability boundary. The marginally stable pressure profile is similar in both magnitude and shape to that observed in ohmically heated tokamak plasmas.

  12. Two Dimensional Particle Transport in the Cct Tokamak Edge Plasma

    NASA Astrophysics Data System (ADS)

    Tynan, George Robert

    The physics of particle transport in the CCT tokamak plasma edge is studied experimentally in this dissertation. A full poloidal array of Langmuir probes is used to measure the equilibrium plasma and transport properties of the CCT edge plasma during Ohmic and H-mode discharges. During Ohmic L-mode, the equilibrium plasma density and electron temperature are found to vary on a magnetic flux surface. The equilibrium plasma distribution coincides with the distribution of particle transport. Inside the last closed flux surface, convective processes dominate particle transport. Several large convective cells are observed near the limiter radius. At and beyond the limiter radius, turbulent transport is significant. The turbulence appears to be driven by the convective plasma flows. In Ohmic L-mode-like discharges, plasma transport occurs predominantly through the low-field region of the tokamak with local bad curvature. The convective cells are destroyed at the L-H transition and replaced with a more poloidally symmetric, radially narrow jet of plasma flow at the limiter radius. The jet effectively isolates the plasma core from the scrape -off layer. The turbulence associated with the convective cells is reduced across the edge region. Radial particle transport across the limiter radius is thus inhibited and the global particle confinement is increased. The available data suggest that the residual H-mode particle transport is more poloidally symmetric.

  13. Neoclassical Simulation of Tokamak Plasmas using Continuum Gyrokinetc Code TEMPEST

    SciTech Connect

    Xu, X Q

    2007-11-09

    We present gyrokinetic neoclassical simulations of tokamak plasmas with self-consistent electric field for the first time using a fully nonlinear (full-f) continuum code TEMPEST in a circular geometry. A set of gyrokinetic equations are discretized on a five dimensional computational grid in phase space. The present implementation is a Method of Lines approach where the phase-space derivatives are discretized with finite differences and implicit backwards differencing formulas are used to advance the system in time. The fully nonlinear Boltzmann model is used for electrons. The neoclassical electric field is obtained by solving gyrokinetic Poisson equation with self-consistent poloidal variation. With our 4D ({psi}, {theta}, {epsilon}, {mu}) version of the TEMPEST code we compute radial particle and heat flux, the Geodesic-Acoustic Mode (GAM), and the development of neoclassical electric field, which we compare with neoclassical theory with a Lorentz collision model. The present work provides a numerical scheme and a new capability for self-consistently studying important aspects of neoclassical transport and rotations in toroidal magnetic fusion devices.

  14. A flowing liquid lithium limiter for the Experimental Advanced Superconducting Tokamak.

    PubMed

    Ren, J; Zuo, G Z; Hu, J S; Sun, Z; Yang, Q X; Li, J G; Zakharov, L E; Xie, H; Chen, Z X

    2015-02-01

    A program involving the extensive and systematic use of lithium (Li) as a "first," or plasma-facing, surface in Tokamak fusion research devices located at Institute of Plasma Physics, Chinese Academy of Sciences, was started in 2009. Many remarkable results have been obtained by the application of Li coatings in Experimental Advanced Superconducting Tokamak (EAST) and liquid Li limiters in the HT-7 Tokamak-both located at the institute. In furtherance of the lithium program, a flowing liquid lithium (FLiLi) limiter system has been designed and manufactured for EAST. The design of the FLiLi limiter is based on the concept of a thin flowing film which was previously tested in HT-7. Exploiting the capabilities of the existing material and plasma evaluation system on EAST, the limiter will be pre-wetted with Li and mechanically translated to the edge of EAST during plasma discharges. The limiter will employ a novel electro-magnetic pump which is designed to drive liquid Li flow from a collector at the bottom of limiter into a distributor at its top, and thus supply a continuously flowing liquid Li film to the wetted plasma-facing surface. This paper focuses on the major design elements of the FLiLi limiter. In addition, a simulation of incoming heat flux has shown that the distribution of heat flux on the limiter surface is acceptable for a future test of power extraction on EAST. PMID:25725839

  15. A flowing liquid lithium limiter for the Experimental Advanced Superconducting Tokamak.

    PubMed

    Ren, J; Zuo, G Z; Hu, J S; Sun, Z; Yang, Q X; Li, J G; Zakharov, L E; Xie, H; Chen, Z X

    2015-02-01

    A program involving the extensive and systematic use of lithium (Li) as a "first," or plasma-facing, surface in Tokamak fusion research devices located at Institute of Plasma Physics, Chinese Academy of Sciences, was started in 2009. Many remarkable results have been obtained by the application of Li coatings in Experimental Advanced Superconducting Tokamak (EAST) and liquid Li limiters in the HT-7 Tokamak-both located at the institute. In furtherance of the lithium program, a flowing liquid lithium (FLiLi) limiter system has been designed and manufactured for EAST. The design of the FLiLi limiter is based on the concept of a thin flowing film which was previously tested in HT-7. Exploiting the capabilities of the existing material and plasma evaluation system on EAST, the limiter will be pre-wetted with Li and mechanically translated to the edge of EAST during plasma discharges. The limiter will employ a novel electro-magnetic pump which is designed to drive liquid Li flow from a collector at the bottom of limiter into a distributor at its top, and thus supply a continuously flowing liquid Li film to the wetted plasma-facing surface. This paper focuses on the major design elements of the FLiLi limiter. In addition, a simulation of incoming heat flux has shown that the distribution of heat flux on the limiter surface is acceptable for a future test of power extraction on EAST.

  16. 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).

  17. Formation and Stability of Impurity "snakes" in Tokamak Plasmas

    SciTech Connect

    L. Delgado-Aparicio, et. al.

    2013-01-28

    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

  18. Measuring the escaping beam ions from a tokamak plasma

    SciTech Connect

    Buchenauer, D.; Heidbrink, W.W.; Roquemore, L.; McGuire, K.

    1987-12-01

    A new technique using a silicon surface barrier (SSB) diode has been developed for measuring the escaping fast ion flux from a tokamak plasma. Calibration of the detector with an ion beam showed that at a fixed energy the diode's output current varied linearly with the incident deuteron flux. The diode was mounted inside the PDX vacuum vessel with collimating apertures designed to admit the spiraling orbits of 50-keV deuterons expelled from the plasma by MHD instabilities. Results from PDX indicated that relative measurements of the escaping fast ion flux due to several plasma instabilities could be made.

  19. Observation of Energetic Particle Driven Modes Relevant to Advanced Tokamak Regimes

    SciTech Connect

    R. Nazikian; B. Alper; H.L. Berk; D. Borba; C. Boswell; R.V. Budny; K.H. Burrell; C.Z. Cheng; E.J. Doyle; E. Edlund; R.J. Fonck; A. Fukuyama; N.N. Gorelenkov; C.M. Greenfield; D.J. Gupta; M. Ishikawa; R.J. Jayakumar; G.J. Kramer; Y. Kusama; R.J. La Haye; G.R. McKee; W.A. Peebles; S.D. Pinches; M. Porkolab; J. Rapp; T.L. Rhodes; S.E. Sharapov; K. Shinohara; J.A. Snipes; W.M. Solomon; E.J. Strait; M. Takechi; M.A. Van Zeeland; W.P. West; K.L. Wong; S. Wukitch; L. Zeng

    2004-10-21

    Measurements of high-frequency oscillations in JET [Joint European Torus], JT-60U, Alcator C-Mod, DIII-D, and TFTR [Tokamak Fusion Test Reactor] plasmas are contributing to a new understanding of fast ion-driven instabilities relevant to Advanced Tokamak (AT) regimes. A model based on the transition from a cylindrical-like frequency-chirping mode to the Toroidal Alfven Eigenmode (TAE) has successfully encompassed many of the characteristics seen in experiments. In a surprising development, the use of internal density fluctuation diagnostics has revealed many more modes than has been detected on edge magnetic probes. A corollary discovery is the observation of modes excited by fast particles traveling well below the Alfven velocity. These observations open up new opportunities for investigating a ''sea of Alfven Eigenmodes'' in present-scale experiments, and highlight the need for core fluctuation and fast ion measurements in a future burning-plasma experiment.

  20. 3D MHD disruptions simulations of tokamaks plasmas

    NASA Astrophysics Data System (ADS)

    Paccagnella, Roberto; Strauss, Hank; Breslau, Joshua

    2008-11-01

    Tokamaks Vertical Displacement Events (VDEs) and disruptions simulations in toroidal geometry by means of a single fluid visco-resistive magneto-hydro-dynamic (MHD) model are presented in this paper. The plasma model, implemented in the M3D code [1], is completed with the presence of a 2D homogeneous wall with finite resistivity. This allows the study of the relatively slowly growing magneto-hydro-dynamical perturbation, the resistive wall mode (RWM), which is, in this work, the main drive of the disruptions. Amplitudes and asymmetries of the halo currents pattern at the wall are also calculated and comparisons with tokamak experimental databases and predictions for ITER are given. [1] W. Park, E.V. Belova, G.Y. Fu, X.Z. Tang, H.R. Strauss, L.E. Sugiyama, Phys. Plasmas 6 (1999) 1796.

  1. Drift-wave fluctuation in an inviscid tokamak plasma

    NASA Astrophysics Data System (ADS)

    Yang, Jian-Rong; Mao, Jie-Jian; Tang, Xiao-Yan

    2013-11-01

    In order to describe the characterization of resistive drift-wave fluctuation in a tokamak plasma, a coupled inviscid two-dimensional Hasegawa—Wakatani model is investigated. Two groups of new analytic solutions with and without phase shift between the fluctuant density and the fluctuant potential are obtained by using the special function transformation method. It is demonstrated that the fluctuant potential shares similar spatio—temporal variations with the density. It is found from the solutions without phase shift that the effect of the diffusion and adiabaticity on the fluctuant density is quite complex, and that the fluctuation may be controlled through the adiabaticity and diffusion. By using the typical parameters in the quasi-adiabatic regime in the solutions with phase shift, it is shown that the density gradient becomes larger as the contours become dense toward the plasma edge and the contours have irregular structures, which reveal the nonuniform distribution in the tokamak edge.

  2. 'Snowflake' H Mode in a Tokamak Plasma

    SciTech Connect

    Piras, F.; Coda, S.; Duval, B. P.; Labit, B.; Marki, J.; Moret, J.-M.; Pitzschke, A.; Sauter, O.; Medvedev, S. Yu.

    2010-10-08

    An edge-localized mode (ELM) H-mode regime, supported by electron cyclotron heating, has been successfully established in a 'snowflake' (second-order null) divertor configuration for the first time in the TCV tokamak. This regime exhibits 2 to 3 times lower ELM frequency and 20%-30% increased normalized ELM energy ({Delta}W{sub ELM}/W{sub p}) compared to an identically shaped, conventional single-null diverted H mode. Enhanced stability of mid- to high-toroidal-mode-number ideal modes is consistent with the different snowflake ELM phenomenology. The capability of the snowflake to redistribute the edge power on the additional strike points has been confirmed experimentally.

  3. Heavy Neutral Beam Probe for Edge Plasma Analysis in Tokamaks

    SciTech Connect

    Castracane, J.

    2001-01-04

    The Heavy Neutral Beam Probe (HNBP) developed initially with DOE funding under the Small Business Innovation Research (SBIR) program was installed on the Tokamak de Varennes (TdeV) at the CCFM. This diagnostic was designed to perform fundamental measurements of edge plasma properties. The hardware was capable of measuring electron density and potential profiles with high spatial and temporal resolution. Fluctuation spectra for these parameters were obtained with HNBP for transport studies.

  4. Momentum Injection in Tokamak Plasmas and Transitions to Reduced Transport

    SciTech Connect

    Parra, F. I.; Highcock, E. G.; Schekochihin, A. A.; Barnes, M.

    2011-03-18

    The effect of momentum injection on the temperature gradient in tokamak plasmas is studied. A plausible scenario for transitions to reduced transport regimes is proposed. The transition happens when there is sufficient momentum input so that the velocity shear can suppress or reduce the turbulence. However, it is possible to drive too much velocity shear and rekindle the turbulent transport. The optimal level of momentum injection is determined. The reduction in transport is maximized in the regions of low or zero magnetic shear.

  5. 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.

  6. Stochastic Acceleration of Dust Particles in Tokamak Edge Plasmas

    SciTech Connect

    Marmolino, C.; De Angelis, U.; Ivlev, A. V.; Morfill, G. E.

    2008-10-15

    Stochastic heating of dust particles resulting from dust charge fluctuations is considered in the conditions of the scrape-off-layer (SOL) in tokamak plasmas. It is shown that kinetic energies corresponding to velocities of {approx_equal}Km/s can be reached in times of order {approx_equal}1 ms by micron-size dust particles interacting with a background of stochastically heated nano-size dust particles.

  7. Tokamak plasma current disruption infrared control system

    DOEpatents

    Kugel, Henry W.; Ulrickson, Michael

    1987-01-01

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

  8. Elements of Neoclassical Theory and Plasma Rotation in a Tokamak

    NASA Astrophysics Data System (ADS)

    Smolyakov, A.

    2015-12-01

    The following sections are included: * Introduction * Quasineutrality condition * Diffusion in fully ionized magnetized plasma and automatic ambipolarity * Toroidal geometry and neoclassical diffusion * Diffusion and ambipolarity in toroidal plasmas * Ambipolarity and equilibrium poloidal rotation * Ambipolarity paradox and damping of poloidal rotation * Neoclassical plasma inertia * Oscillatory modes of poloidal plasma rotation * Dynamics of the toroidal momentum * Momentum diffusion in strongly collisional, short mean free path regime * Diffusion of toroidal momentum in the weak collision (banana) regime * Toroidal momentum diffusion and momentum damping from drift-kinetic theory and fluid moment equations * Comments on non-axisymmetric effects * Summary * Acknowledgments * Appendix: Trapped (banana) particles and collisionality regimes in a tokamak * Appendix: Hierarchy of moment equations * Appendix: Plasma viscosity tensor in the magnetic field: parallel viscosity, gyroviscosity, and perpendicular viscosity * Appendix: Closure relations for the flux surface averaged parallel viscosity in neoclassical (banana and plateau) regimes * References

  9. Eikonal waves, caustics and mode conversion in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Jaun, A.; Tracy, E. R.; Kaufman, A. N.

    2007-01-01

    Ray optics is used to model the propagation of short electromagnetic plasma waves in toroidal geometry. The new RAYCON code evolves each ray independently in phase space, together with its amplitude, phase and focusing tensor to describe the transport of power along the ray. Particular emphasis is laid on caustics and mode conversion layers, where a linear phenomenon splits a single incoming ray into two. The complete mode conversion algorithm is described and tested for the first time, using the two space dimensions that are relevant in a tokamak. Applications are shown, using a cold plasma model to account for mode conversion at the ion-hybrid resonance in the Joint European Torus.

  10. Turbulence studies in Tokamak boundary plasmas with realistic divertor geometry

    SciTech Connect

    Xu, X.Q.

    1998-10-14

    Results are presented from the 3D nonlocal electromagnetic turbulence code BOUT [1] and the linearized shooting code BAL[2] to study turbulence in tokamak boundary plasmas and its relationship to the L-H transition, in a realistic divertor plasma geometry. The key results include: (1) the identification of the dominant, resistive X-point mode in divertor geometry and (2) turbulence suppression in the L-H transition by shear in the ExB drift speed, ion diamagnetism and finite polarization. Based on the simulation results, a parameterization of the transport is given that includes the dependence on the relevant physical parameters.

  11. Quiescent double barrier high-confinement mode plasmas in the DIII-D tokamak

    NASA Astrophysics Data System (ADS)

    Burrell, K. H.; Austin, M. E.; Brennan, D. P.; DeBoo, J. C.; Doyle, E. J.; Fenzi, C.; Fuchs, C.; Gohil, P.; Greenfield, C. M.; Groebner, R. J.; Lao, L. L.; Luce, T. C.; Makowski, M. A.; McKee, G. R.; Moyer, R. A.; Petty, C. C.; Porkolab, M.; Rettig, C. L.; Rhodes, T. L.; Rost, J. C.; Stallard, B. W.; Strait, E. J.; Synakowski, E. J.; Wade, M. R.; Watkins, J. G.; West, W. P.

    2001-05-01

    High-confinement (H-mode) operation is the choice for next-step tokamak devices based either on conventional or advanced tokamak physics. This choice, however, comes at a significant cost for both the conventional and advanced tokamaks because of the effects of edge localized modes (ELMs). ELMs can produce significant erosion in the divertor and can affect the beta limit and reduced core transport regions needed for advanced tokamak operation. Experimental results from DIII-D [J. L. Luxon et al., Plasma Physics and Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] this year have demonstrated a new operating regime, the quiescent H-mode regime, which solves these problems. We have achieved quiescent H-mode operation that is ELM-free and yet has good density and impurity control. In addition, we have demonstrated that an internal transport barrier can be produced and maintained inside the H-mode edge barrier for long periods of time (>3.5 s or >25 energy confinement times τE), yielding a quiescent double barrier regime. By slowly ramping the input power, we have achieved βNH89=7 for up to 5 times the τE of 150 ms. The βNH89 values of 7 substantially exceed the value of 4 routinely achieved in the standard ELMing H mode. The key factors in creating the quiescent H-mode operation are neutral beam injection in the direction opposite to the plasma current (counter injection) plus cryopumping to reduce the density. Density and impurity control in the quiescent H mode is possible because of the presence of an edge magnetohydrodynamic (MHD) oscillation, the edge harmonic oscillation, which enhances the edge particle transport while leaving the energy transport unaffected.

  12. Equilibrium calculations for plasma control in CIT (Compact Ignition Tokamak)

    SciTech Connect

    Strickler, D.J.; Peng, Y-K.M. . Fusion Engineering Design Center); Pomphrey, N.; Jardin, S.C. . Plasma Physics Lab.)

    1990-01-01

    The free-boundary equilibrium code VEQ provides equilibrium data that are used by the Tokamak Simulation Code (TSC) in design and analysis of the poloidal field (PF) system for the Compact Ignition Tokamak (CIT). VEQ serves as an important design tool for locating the PF coils and defining coil current trajectories and control systems for TSC. In this report, VEQ and its role in the TSC analysis of the CIT PF system are described. Equilibrium and coil current calculations are discussed, an overview of the CIT PF system is presented, a set of reference equilibria for modeling a complete discharge in CIT is described, and the concept of a plasma shape control matrix is introduced. 9 refs., 8 figs., 7 tabs.

  13. Molecular emission in the edge plasma of T-10 tokamak

    SciTech Connect

    Zimin, A. M.; Krupin, V. A.; Troynov, V. I.; Klyuchnikov, L. A.

    2015-12-15

    The experiments on recording molecular emission in the edge plasma of the T-10 tokamak are described. To obtain reliable spectra with sufficient spectral, temporal, and spatial resolution, the optical circuit is optimized for various experimental conditions. Typical spectra measured in two sections of the tokamak are shown. It is shown that, upon varying the parameters of the discharge, the molecular spectrum not only changes significantly in intensity but also undergoes a qualitative change in the rotational and vibrational structure. For a detailed analysis, we use the Fulcher-α system (d{sup 3}Π{sub u}–a{sup 3}Σ{sub g}{sup +}) of deuterium in the wavelength range from 590 to 640 nm. The rotational temperatures of ground state X{sup 1}Σ{sub g}{sup +} and upper excited state d{sup 3}Π{sub u} are estimated by the measured spectra.

  14. Development on JET of advanced tokamak operations for ITER

    NASA Astrophysics Data System (ADS)

    Tuccillo, A. A.; Crisanti, F.; Litaudon, X.; Baranov, Yu. F.; Becoulet, A.; Becoulet, M.; Bertalot, L.; Castaldo, C.; Challis, C. D.; Cesario, R.; DeBaar, M. R.; de Vries, P. C.; Esposito, B.; Frigione, D.; Garzotti, L.; Giovannozzi, E.; Giroud, C.; Gorini, G.; Gormezano, C.; Hawkes, N. C.; Hobirk, J.; Imbeaux, F.; Joffrin, E.; Lomas, P. J.; Mailloux, J.; Mantica, P.; Mantsinen, M. J.; Mazon, D.; Moreau, D.; Murari, A.; Pericoli-Ridolfini, V.; Rimini, F.; Sips, A. C. C.; Sozzi, C.; Tudisco, O.; Van Eester, D.; Zastrow, K.-D.; work-programme contributors, JET-EFDA

    2006-02-01

    Recent research on advanced tokamak in JET has focused on scenarios with both monotonic and reversed shear q-profiles having plasma parameters as relevant as possible for extrapolation to ITER. Wide internal transport barriers (ITBs), r/a ~ 0.7, are formed at ITER relevant triangularity δ ~ 0.45 and moderate plasma current, IP = 1.5-2.5 MA, with ne/nG ~ 60% when ELMs are moderated by Ne injection. At higher current (IP <= 3.5 MA, δ ~ 0.25) wide ITBs sitting at r/a >= 0.5, in the positive shear region, have been developed. Generally MHD events terminate these barriers otherwise limited in strength by power availability. ITBs with core density close to Greenwald value, Te ~ Ti and low toroidal rotation (4 times lower than standard ITBs) are obtained in plasma target preformed by opportune timing of lower hybrid current drive (LHCD), pellet injection and a small amount of NBI power. Wide ITBs, r/a ~ 0.6, of moderate strength, can be sustained without impurities accumulation for a time close to neoclassical resistive time in 3 T/1.8 MA discharges that exhibit reversed magnetic shear profiles and type-III ELMy edge. These discharges have been extended to the maximum duration allowed by JET subsystems (20 s) bringing to the record of injected energy in a JET discharge: E ~ 330 MJ. Portability of ITB physics has been addressed through dedicated similarity experiments. The ITB is identified as a layer of reduced diffusivity studying the propagation of the heat wave generated by modulating the ICRF mode conversion (MC) electron heating. Impressive results, QDT ~ 0.25, are obtained in these deuterium discharges with 3He minority when the MC layer is located in the core. The ion behaviour has been investigated in pure LHCD electron ITBs optimizing the 3He minority concentration for direct ion heating. Preliminary results of particle transport, studied via injection of a trace of tritium and an Ar-Ne mixture, will be presented.

  15. Neoclassical momentum transport in an impure rotating tokamak plasma

    SciTech Connect

    Newton, S.; Helander, P.

    2006-01-15

    It is widely believed that transport barriers in tokamak plasmas are caused by radial electric-field shear, which is governed by angular momentum transport. Turbulence is suppressed in the barrier, and ion thermal transport is comparable to the neoclassical prediction, but experimentally angular momentum transport has remained anomalous. With this motivation, the collisional transport matrix is calculated for a low collisionality plasma with collisional impurity ions. The bulk plasma toroidal rotation velocity is taken to be subsonic, but heavy impurities undergo poloidal redistribution due to the centrifugal force. The impurities give rise to off-diagonal terms in the transport matrix, which cause the plasma to rotate spontaneously. At conventional aspect ratio, poloidal impurity redistribution increases the angular momentum flux by a factor up to {epsilon}{sup -3/2} over previous predictions, making it comparable to the 'banana' regime heat flux. The flux is primarily driven by radial pressure and temperature gradients.

  16. The role of plasma rotation on MHD instabilities in tokamaks

    NASA Astrophysics Data System (ADS)

    Varadarajan, V.; Miley, G. H.

    An improved analysis of the linear stage of the internal kink mode has been developed to include plasma rotation and finite aspect ratio effects. The linear instability growth rates are increased by the plasma rotation. A pseudo-variational, bilinear formalism is used to discretize the linear instability equations; Fourier decomposition is used in the periodic coordinate, and a mixed-finite element procedure is adopted in the radial direction. The numerical studies with the resulting PEST-like code can be used to predict the complex plasma eigenfrequencies. The finite aspect ratio results are similar to the large aspect ratio results for flow instability. The complex instability frequencies found in the 'fishbone' and TAE modes would be strong determined by the large plasma rotation velocities observed in present-day tokamak devices. These effects could be studied by using the computationally convenient bilinear form derived from the Frieman-Rotenberg equation.

  17. Predicting High Harmonic Ion Cyclotron Heating Efficiency in Tokamak Plasmas

    NASA Astrophysics Data System (ADS)

    Green, D. L.; Berry, L. A.; Chen, G.; Ryan, P. M.; Canik, J. M.; Jaeger, E. F.

    2011-09-01

    Observations of improved radio frequency (rf) heating efficiency in ITER relevant high-confinement (H-)mode plasmas on the National Spherical Tokamak Experiment are investigated by whole-device linear simulation. The steady-state rf electric field is calculated for various antenna spectra and the results examined for characteristics that correlate with observations of improved or reduced rf heating efficiency. We find that launching toroidal wave numbers that give fast-wave propagation in the scrape-off plasma excites large amplitude (˜kVm-1) coaxial standing modes between the confined plasma density pedestal and conducting vessel wall. Qualitative comparison with measurements of the stored plasma energy suggests that these modes are a probable cause of degraded heating efficiency.

  18. Predicting high harmonic ion cyclotron heating efficiency in Tokamak plasmas.

    PubMed

    Green, D L; Berry, L A; Chen, G; Ryan, P M; Canik, J M; Jaeger, E F

    2011-09-30

    Observations of improved radio frequency (rf) heating efficiency in ITER relevant high-confinement (H-)mode plasmas on the National Spherical Tokamak Experiment are investigated by whole-device linear simulation. The steady-state rf electric field is calculated for various antenna spectra and the results examined for characteristics that correlate with observations of improved or reduced rf heating efficiency. We find that launching toroidal wave numbers that give fast-wave propagation in the scrape-off plasma excites large amplitude (∼kV m(-1)) coaxial standing modes between the confined plasma density pedestal and conducting vessel wall. Qualitative comparison with measurements of the stored plasma energy suggests that these modes are a probable cause of degraded heating efficiency.

  19. OVERVIEW OF RECENT EXPERIMENTAL RESULTS FROM THE DIII-D ADVANCED TOKAMAK PROGRAM

    SciTech Connect

    BURRELL,KH

    2002-11-01

    OAK A271 OVERVIEW OF RECENT EXPERIMENTAL RESULTS FROM THE DIII-D ADVANCED TOKAMAK PROGRAM. The DIII-D research program is developing the scientific basis for advanced tokamak (AT) modes of operation in order to enhance the attractiveness of the tokamak as an energy producing system. Since the last International Atomic Energy Agency (IAEA) meeting, the authors have made significant progress in developing the building blocks needed for AT operation: (1) the authors have doubled the magnetohydrodynamic (MHD) stable tokamak operating space through rotational stabilization of the resistive wall mode; (2) using this rotational stabilization, they have achieved {beta}{sub N}H{sub 89} {le} 10 for 4 {tau}{sub E} limited by the neoclassical tearing mode; (3) using real-time feedback of the electron cyclotron current drive (ECCD) location, they have stabilized the (m,n) = (3,2) neoclassical tearing mode and then increased {beta}{sub T} by 60%; (4) they have produced ECCD stabilization of the (2,1) neoclassical tearing mode in initial experiments; (5) they have made the first integrated AT demonstration discharges with current profile control using ECCD; (6) ECCD and electron cyclotron heating (ECH) have been used to control the pressure profile in high performance plasmas; and (7) they have demonstrated stationary tokamak operation for 6.5 s (36 {tau}{sub E}) at the same fusion gain parameter of {beta}{sub N}H{sub 89}/q{sub 95}{sup 2} {approx} 0.4 as ITER but at much higher q{sub 95} = 4.2. They have developed general improvements applicable to conventional and advanced tokamak operating modes: (1) they have an existence proof of a mode of tokamak operation, quiescent H-mode, which has no pulsed, ELM heat load to the divertor and which can run for long periods of time (3.8 s or 25 {tau}{sub E}) with constant density and constant radiation power; (2) they have demonstrated real-time disruption detection and mitigation for vertical disruption events using high pressure gas jet

  20. Tokamak magneto-hydrodynamics and reference magnetic coordinates for simulations of plasma disruptions

    SciTech Connect

    Zakharov, Leonid E.; Li, Xujing

    2015-06-15

    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 plasma 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.

  1. Tokamak plasma current disruption infrared control system

    DOEpatents

    Kugel, H.W.; Ulrickson, M.

    1984-04-16

    This invention is directed to the diagnosis and detection of gross or macroinstabilities in a magnetically-confined fusion plasma device. Detection is performed in real time, and is prompt such that correction of the instability can be initiated in a timely fashion.

  2. Plasma engineering studies for Tennessee Tokamak (TENTOK) fusion power reactor

    SciTech Connect

    Yokoyama, K.E.; Lacatski, J.T.; Miller, J.B.; Bryan, W.E.; King, P.W.; Santoro, R.T.; Uckan, N.A.; Shannon, T.E.

    1984-02-01

    This paper summarizes the results of the plasma engineering and systems analysis studies for the Tennessee Tokamak (TENTOK) fusion power reactor. TENTOK is a 3000-MW(t) central station power plant that uses deuterium-tritium fuel in a D-shaped tokamak plasma configuration with a double-null poloidal divertor. The major parameters are R/sub 0/ = 6.4 m, a = 1.6 m, sigma (elongation) = 1.65, (n) = 1.5 x 10/sup 20/ m/sup -3/, (T) = 15 keV, (..beta..) = 6%, B/sub T/ (on-axis) = 5.6 T, I/sub p/ = 8.5 MA, and wall loading = 3 MW/m/sup 2/. Detailed analyses are performed in the areas of (1) transport simulation using the one-and-one-half-dimensional (1-1/2-D) WHIST transport code, (2) equilibrium/poloidal field coil systems, (3) neutral beam and radiofrequency (rf) heating, and (4) pellet fueling. In addition, impurity control systems, diagnostics and controls, and possible microwave plasma preheating and steady-state current drive options are also considered. Some of the major features of TENTOK include rf heating in the ion cyclotron range of frequencies, superconducting equilibrium field coils outside the superconducting toroidal field coils, a double-null poloidal divertor for impurity control and alpha ash removal, and rf-assisted plasma preheating and current startup.

  3. Magnetized plasma flow injection into tokamak and high-beta compact torus plasmas

    NASA Astrophysics Data System (ADS)

    Matsunaga, Hiroyuki; Komoriya, Yuuki; Tazawa, Hiroyasu; Asai, Tomohiko; Takahashi, Tsutomu; Steinhauer, Loren; Itagaki, Hirotomo; Onchi, Takumi; Hirose, Akira

    2010-11-01

    As an application of a magnetized coaxial plasma gun (MCPG), magnetic helicity injection via injection of a highly elongated compact torus (magnetized plasma flow: MPF) has been conducted on both tokamak and field-reversed configuration (FRC) plasmas. The injected plasmoid has significant amounts of helicity and particle contents and has been proposed as a fueling and a current drive method for various torus systems. In the FRC, MPF is expected to generate partially spherical tokamak like FRC equilibrium by injecting a significant amount of magnetic helicity. As a circumstantial evidence of the modified equilibrium, suppressed rotational instability with toroidal mode number n = 2. MPF injection experiments have also been applied to the STOR-M tokamak as a start-up and current drive method. Differences in the responses of targets especially relation with beta value and the self-organization feature will be studied.

  4. Plasma shape experiments for an optimized tokamak

    NASA Astrophysics Data System (ADS)

    Hyatt, A. W.; Osborne, T. H.; Lazarus, E. A.

    1994-07-01

    In this paper we present results from recent experiments at DIII-D which measured the plasma stability and confinement performance product, beta(tau)(sub E), in one previously studied and three new plasma shapes. One important goal of these experiments was to identify performance vs. shape trends which would identify a shape compatible with both high performance and the planned effort to decrease the power flux to the divertor floor using a closed 'slot' divertor geometry. The closed divertor hardware must be designed for a reduced set of plasma shapes, so care must be taken to choose the shape that optimizes beta(tau)(sub E) and divertor performance. The four shapes studied form a matrix of moderate and high elongations (kappa congruent to 1.8 and 2.1) and low and high triangularities (delta congruent to 0.3 and 0.9). All configurations were double-null diverted (DND), held fixed during a shot, with neutral beam heating. The shapes span a range of X-point locations compatible with the envisioned closed divertor. We find that from shape to shape, a shot's transient normalized performance, beta(sub N)H, where beta(sub N) is equivalent to beta/(I(sup p)/aB(sub T)) and H is equivalent to tau(sub E)/tau(sub E)(sup ITER-89P), increases strongly with triangularity, but depends only weakly on elongation. However, the normalized performance during quasi stationary ELMing H-mode, to which these discharges eventually relax, is insensitive to both triangularity and elongation. The moderate elongation, high triangularity DND shape is shown to be near optimum for future studies on DIII-D.

  5. Fusion Plasma Theory: Task 3, Auxiliary radiofrequency heating of tokamaks. Annual report, November 16, 1991--November 15, 1992

    SciTech Connect

    Scharer, J.E.

    1992-12-31

    The research performed under this grant during the past year has been concentrated on the following several key tokamak ICRF (Ion Cyclotron Range of Frequencies) coupling, heating and current drive issues: Efficient coupling during the L- to H- mode transition by analysis and computer simulation of ICRF antennas; analysis of ICRF cavity-backed coil antenna coupling to plasma edge profiles including fast and ion Bernstein wave coupling for heating and current drive; benchmarking the codes to compare with current JET, D-IIID and ASDEX experimental results and predictions for advanced tokamaks such as BPX and SSAT (Steady-State Advanced Tokamak); ICRF full-wave field solutions, power conservation, heating analyses and minority ion current drive; and the effects of fusion alpha particle or ion tail populations on the ICRF absorption. Research progress, publications, and conference and workshop presentations are summarized in this report.

  6. Mechanisms governing radial heat fluxes in tokamak plasma

    NASA Astrophysics Data System (ADS)

    Razumova, K. A.; Timchenko, N. N.; Dnestrovskij, A. Yu.; Lysenko, S. E.

    2016-09-01

    A method for analyzing the characteristics of turbulence responsible for radial heat transport is proposed. The method is based on the previously proposed hypotheses (to a great extent, confirmed experimentally) concerning the consistency of normalized pressure profiles in tokamak plasmas and the mechanism of internal transport barrier formation. Using the proposed approach, it is shown that, under an external action on the plasma, when the plasma heat flux onto the wall grows, the spectrum of turbulent modes broadens due to the excitation of modes with lower poloidal numbers m. Thus, in contrast to the conventional diffusion approach, the transport coefficient depends on the flux intensity. A mechanism of formation of internal transport barriers is proposed.

  7. Trade studies of plasma elongation for next-step tokamaks

    SciTech Connect

    Galambos, J.D.; Strickler, D.J.; Peng, Y.K.M.; Reid, R.L.

    1988-09-01

    The effect of elongation on minimum-cost devices is investigated for elongations ranging from 2 to 3. The analysis, carried out with the TETRA tokamak systems code, includes the effects of elongation on both physics (plasma beta limit) and engineering (poloidal field coil currents) issues. When ignition is required, the minimum cost occurs for elongations from 2.3 to 2.9, depending on the plasma energy confinement scaling used. Scalings that include favorable plasma current dependence and/or degradation with fusion power tend to have minimum cost at higher elongation (2.5-2.9); scalings that depend primarily on size result in lower elongation (/approximately/2.3) for minimum cost. For design concepts that include steady-state current-driven operation, minimum cost occurs at an elongation of 2.3. 12 refs., 13 figs.

  8. Electromagnetic effects on trace impurity transport in tokamak plasmas

    SciTech Connect

    Hein, T.; Angioni, C.

    2010-01-15

    The impact of electromagnetic effects on the transport of light and heavy impurities in tokamak plasmas is investigated by means of an extensive set of linear gyrokinetic numerical calculations with the code GYRO[J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] and of analytical derivations with a fluid model. The impurity transport is studied by appropriately separating diffusive and convective contributions, and conditions of background microturbulence dominated by both ion temperature gradient (ITG) and trapped electron modes (TEMs) are analyzed. The dominant contribution from magnetic flutter transport turns out to be of pure convective type. However it remains small, below 10% with respect to the ExB transport. A significant impact on the impurity transport due to an increase in the plasma normalized pressure parameter beta is observed in the case of ITG modes, while for TEM the overall effect remains weak. In realistic conditions of high beta plasmas in the high confinement (H-) mode with dominant ITG turbulence, the impurity diffusivity is found to decrease with increasing beta in qualitative agreement with recent observations in tokamaks. In contrast, in these conditions, the ratio of the total off-diagonal convective velocity to the diagonal diffusivity is not strongly affected by an increase in beta, particularly at low impurity charge, due to a compensation between the different off-diagonal contributions.

  9. Particle confinement of pellet-fuelled tokamak plasma

    NASA Astrophysics Data System (ADS)

    Valovič, M.; Axon, K.; Garzotti, L.; Saarelma, S.; Thyagaraja, A.; Akers, R.; Gurl, C.; Kirk, A.; Lloyd, B.; Maddison, G. P.; Morris, A. W.; Patel, A.; Shibaev, S.; Scannell, R.; Taylor, D.; Walsh, M.; MAST Team

    2008-07-01

    This paper quantifies the particle confinement of pellet-fuelled plasmas as measured in the Mega Ampere Spherical Tokamak. The dataset is restricted mostly to neutral beam heated plasmas in H-mode and to shallow pellets launched from the high-field side. It is shown that the pellet deposition can be explained only by invoking the ∇B drift of the pellet ablatant. The pellet creates a zone with positive density gradient and increased temperature gradient. Simulations show that these changes could increase the level of micro-turbulence and thus enhance further the penetration of pellet-deposited particles towards the core. Post-pellet dynamics of the density profile is characterized by the pellet retention time τpel. It is shown that τpel correlates with the status of the edge transport barrier (L-mode or H-mode) and decreases rapidly for pellet deposition radius rpel approaching the plasma edge. For ELMy H-mode and pellet deposition radius of rpel ≈ 0.8a, the pellet retention time is about 20% of the energy confinement time. The fuelling requirement by the pellets for ITER and the Component Test Facility based on the spherical tokamak is discussed.

  10. A flowing liquid lithium limiter for the Experimental Advanced Superconducting Tokamak

    SciTech Connect

    Ren, J.; Zuo, G. Z.; Hu, J. S.; Sun, Z.; Yang, Q. X.; Li, J. G.; Xie, H.; Chen, Z. X.; Zakharov, L. E.

    2015-02-15

    A program involving the extensive and systematic use of lithium (Li) as a “first,” or plasma-facing, surface in Tokamak fusion research devices located at Institute of Plasma Physics, Chinese Academy of Sciences, was started in 2009. Many remarkable results have been obtained by the application of Li coatings in Experimental Advanced Superconducting Tokamak (EAST) and liquid Li limiters in the HT-7 Tokamak—both located at the institute. In furtherance of the lithium program, a flowing liquid lithium (FLiLi) limiter system has been designed and manufactured for EAST. The design of the FLiLi limiter is based on the concept of a thin flowing film which was previously tested in HT-7. Exploiting the capabilities of the existing material and plasma evaluation system on EAST, the limiter will be pre-wetted with Li and mechanically translated to the edge of EAST during plasma discharges. The limiter will employ a novel electro-magnetic pump which is designed to drive liquid Li flow from a collector at the bottom of limiter into a distributor at its top, and thus supply a continuously flowing liquid Li film to the wetted plasma-facing surface. This paper focuses on the major design elements of the FLiLi limiter. In addition, a simulation of incoming heat flux has shown that the distribution of heat flux on the limiter surface is acceptable for a future test of power extraction on EAST.

  11. Advanced tokamak reactors based on the spherical torus (ATR/ST). Preliminary design considerations

    SciTech Connect

    Miller, R.L.; Krakowski, R.A.; Bathke, C.G.; Copenhaver, C.; Schnurr, N.M.; Engelhardt, A.G.; Seed, T.J.; Zubrin, R.M.

    1986-06-01

    Preliminary design results relating to an advanced magnetic fusion reactor concept based on the high-beta, low-aspect-ratio, spherical-torus tokamak are summarized. The concept includes resistive (demountable) toroidal-field coils, magnetic-divertor impurity control, oscillating-field current drive, and a flowing liquid-metal breeding blanket. Results of parametric tradeoff studies, plasma engineering modeling, fusion-power-core mechanical design, neutronics analyses, and blanket thermalhydraulics studies are described. The approach, models, and interim results described here provide a basis for a more detailed design. Key issues quantified for the spherical-torus reactor center on the need for an efficient drive for this high-current (approx.40 MA) device as well as the economic desirability to increase the net electrical power from the nominal 500-MWe(net) value adopted for the baseline system. Although a direct extension of present tokamak scaling, the stablity and transport of this high-beta (approx.0.3) plasma is a key unknown that is resoluble only by experiment. The spherical torus generally provides a route to improved tokamak reactors as measured by considerably simplified coil technology in a configuration that allows a realistic magnetic divertor design, both leading to increased mass power density and reduced cost.

  12. THz time-domain spectroscopy for tokamak plasma diagnostics

    NASA Astrophysics Data System (ADS)

    Causa, F.; Zerbini, M.; Johnston, M.; Buratti, P.; Doria, A.; Gabellieri, L.; Gallerano, G. P.; Giovenale, E.; Pacella, D.; Romano, A.; Tuccillo, A. A.; Tudisco, O.

    2014-08-01

    The technology is now becoming mature for diagnostics using large portions of the electromagnetic spectrum simultaneously, in the form of THz pulses. THz radiation-based techniques have become feasible for a variety of applications, e.g., spectroscopy, imaging for security, medicine and pharmaceutical industry. In particular, time-domain spectroscopy (TDS) is now being used also for plasma diagnostics in various fields of application. This technique is promising also for plasmas for fusion applications, where plasma characteristics are non-uniform and/or evolve during the discharge This is because THz pulses produced with femtosecond mode-locked lasers conveniently span the spectrum above and below the plasma frequency and, thus, can be used as very sensitive and versatile probes of widely varying plasma parameters. The short pulse duration permits time resolving plasma characteristics while the large frequency span permits a large dynamic range. The focus of this work is to present preliminary experimental and simulation results demonstrating that THz TDS can be realistically adapted as a versatile tokamak plasma diagnostic technique.

  13. THz time-domain spectroscopy for tokamak plasma diagnostics

    SciTech Connect

    Causa, F.; Zerbini, M.; Buratti, P.; Gabellieri, L.; Pacella, D.; Romano, A.; Tuccillo, A. A.; Tudisco, O.; Johnston, M.; Doria, A.; Gallerano, G. P.; Giovenale, E.

    2014-08-21

    The technology is now becoming mature for diagnostics using large portions of the electromagnetic spectrum simultaneously, in the form of THz pulses. THz radiation-based techniques have become feasible for a variety of applications, e.g., spectroscopy, imaging for security, medicine and pharmaceutical industry. In particular, time-domain spectroscopy (TDS) is now being used also for plasma diagnostics in various fields of application. This technique is promising also for plasmas for fusion applications, where plasma characteristics are non-uniform and/or evolve during the discharge This is because THz pulses produced with femtosecond mode-locked lasers conveniently span the spectrum above and below the plasma frequency and, thus, can be used as very sensitive and versatile probes of widely varying plasma parameters. The short pulse duration permits time resolving plasma characteristics while the large frequency span permits a large dynamic range. The focus of this work is to present preliminary experimental and simulation results demonstrating that THz TDS can be realistically adapted as a versatile tokamak plasma diagnostic technique.

  14. Optical system design for the charge exchange spectroscopy of the Korea superconducting tokamak advanced research device

    NASA Astrophysics Data System (ADS)

    Oh, Seungtae; Ko, Won-Ha

    2011-04-01

    The collective optical design is described for the charge exchange spectroscopy (CES) of the Korea superconducting tokamak advanced research (KSTAR) device. The CES diagnostic measures the ion temperature of carbon and other impurities, in conjunction with the neutral heating beam in KSTAR. The visible light from the plasma is concentrated via collection optics and imaged onto quartz fibers. The collection optics in the system is the key component for the CES system. The final design is derived through four steps and its performance is examined in a simulation step. In this paper, the design details of the collective optical system for the KSTAR CES are discussed.

  15. Magnetic confinement experiment -- 1: Tokamaks

    SciTech Connect

    Goldston, R.J.

    1994-12-31

    This report reviews presentations made at the 15th IAEA Conference on Plasma Physics and Controlled Nuclear Fusion on experimental tokamak physics, particularly on advances in core plasma physics, divertor and edge physics, heating and current drive, and tokamak concept optimization.

  16. Tokamak plasma self-organization and the possibility to have the peaked density profile in ITER

    NASA Astrophysics Data System (ADS)

    Razumova, K. A.; Andreev, V. F.; Kislov, A. Ya.; Kirneva, N. A.; Lysenko, S. E.; Pavlov, Yu. D.; Shafranov, T. V.; T-10 Team; Donné, A. J. H.; Hogeweij, G. M. D.; Spakman, G. W.; Jaspers, R.; TEXTOR Team; Kantor, M.; Walsh, M.

    2009-06-01

    The self-organization of a tokamak plasma is a fundamental turbulent plasma phenomenon, which leads to the formation of a self-consistent pressure profile. This phenomenon has been investigated in several tokamaks with different methods of heating. It is shown that the normalized pressure profile has a universal shape for a wide class of tokamaks and regimes, if the normalized radius ρ = r/(IpR/κB)1/2 is used. The consequences of this phenomenon for low aspect ratio tokamaks, the optimal deposition of additional heating, fast velocity of heat/cold pulse propagation and the possibility of obtaining a peaked density profile in ITER are discussed.

  17. Halo current diagnostic system of experimental advanced superconducting tokamak

    SciTech Connect

    Chen, D. L.; Shen, B.; Sun, Y.; Qian, J. P. Wang, Y.; Xiao, B. J.; Granetz, R. S.

    2015-10-15

    The design, calibration, and installation of disruption halo current sensors for the Experimental Advanced Superconducting Tokamak are described in this article. All the sensors are Rogowski coils that surround conducting structures, and all the signals are analog integrated. Coils with two different cross-section sizes have been fabricated, and their mutual inductances are calibrated. Sensors have been installed to measure halo currents in several different parts of both the upper divertor (tungsten) and lower divertor (graphite) at several toroidal locations. Initial measurements from disruptions show that the halo current diagnostics are working well.

  18. Halo current diagnostic system of experimental advanced superconducting tokamak.

    PubMed

    Chen, D L; Shen, B; Granetz, R S; Sun, Y; Qian, J P; Wang, Y; Xiao, B J

    2015-10-01

    The design, calibration, and installation of disruption halo current sensors for the Experimental Advanced Superconducting Tokamak are described in this article. All the sensors are Rogowski coils that surround conducting structures, and all the signals are analog integrated. Coils with two different cross-section sizes have been fabricated, and their mutual inductances are calibrated. Sensors have been installed to measure halo currents in several different parts of both the upper divertor (tungsten) and lower divertor (graphite) at several toroidal locations. Initial measurements from disruptions show that the halo current diagnostics are working well.

  19. Toroidal flow and radial particle flux in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Callen, J. D.; Cole, A. J.; Hegna, C. C.

    2009-08-01

    Many effects influence toroidal flow evolution in tokamak plasmas. Momentum sources and radial plasma transport due to collisional processes and microturbulence-induced anomalous transport are usually considered. In addition, toroidal flow can be affected by nonaxisymmetric magnetic fields; resonant components cause localized electromagnetic toroidal torques near rational surfaces in flowing plasmas and nonresonant components induce "global" toroidal flow damping torque throughout the plasma. Also, poloidal magnetic field transients on the magnetic field diffusion time scale can influence plasma transport. Many of these processes can also produce momentum pinch and intrinsic flow effects. This paper presents a comprehensive and self-consistent description of all these effects within a fluid moment context. Plasma processes on successive time scales (and constraints they impose) are considered sequentially: compressional Alfvén waves (Grad-Shafranov equilibrium and ion radial force balance), sound waves (pressure constant along a field line and incompressible flows within a flux surface), and ion collisions (damping of poloidal flow). Finally, plasma transport across magnetic flux surfaces is induced by the many second order (in the small gyroradius expansion) toroidal torque effects indicated above. Nonambipolar components of the induced particle transport fluxes produce radial plasma currents. Setting the flux surface average of the net radial current induced by all these effects to zero yields the transport-time-scale equation for evolution of the plasma toroidal flow. It includes a combination of global toroidal flow damping and resonant torques induced by nonaxisymmetric magnetic field components, poloidal magnetic field transients, and momentum source effects, as well as the usual collision- and microturbulence-induced transport. On the transport time scale, the plasma toroidal rotation determines the radial electric field for net ambipolar particle transport

  20. Electron temperature gradient driven instability in the tokamak boundary plasma

    SciTech Connect

    Xu, X.Q.; Rosenbluth, M.N.; Diamond, P.H.

    1992-12-15

    A general method is developed for calculating boundary plasma fluctuations across a magnetic separatrix in a tokamak with a divertor or a limiter. The slab model, which assumes a periodic plasma in the edge reaching the divertor or limiter plate in the scrape-off layer(SOL), should provide a good estimate, if the radial extent of the fluctuation quantities across the separatrix to the edge is small compared to that given by finite particle banana orbit. The Laplace transform is used for solving the initial value problem. The electron temperature gradient(ETG) driven instability is found to grow like t{sup {minus}1/2}e{sup {gamma}mt}.

  1. 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.

  2. Impurity poloidal asymmetries and plasma rotation in the PDX Tokamak

    NASA Astrophysics Data System (ADS)

    Brau, K.

    Vertical poloidal asymmetries of carbon and oxygen in the PDX Tokamak were monitored under a variety of discharge conditions in circular plasmas. Near the edge of the plasma and in the region beyond the limiter, the asymmetries appear to be caused by local impurity recycling, variations in the length of the emitting region, and effects due to vertical ion drifts. In the case of C V impurities, the sign and magnitude of the asymmetry is in qualitative agreement with the predictions of a quasi-neoclassical fluid model of impurity transport. A two dimensional computer code is used to simulate different models of poloidal asymmetries, including: (1) poloidally asymmetric source function, (2) charge exchange recombination with neutral hydrogen, (3) poloidally asymmetric electron ensity and temperature profiles, (4) poloidally varying anomalous radial diffusion coefficient, and (5) the quasi-neoclassical fluid model.

  3. Positron creation and annihilation in tokamak plasmas with runaway electrons.

    PubMed

    Helander, P; Ward, D J

    2003-04-01

    It is shown that electron-positron pair production is expected to occur in post-disruption plasmas in large tokamaks, including JET and JT-60U, where up to about 10(14) positrons may be created in collisions between multi-MeV runaway electrons and thermal particles. If the loop voltage is large enough, they are accelerated and form a beam of long-lived runaway positrons in the direction opposite to that of the electrons; if the loop voltage is smaller, the positrons have a lifetime of a few hundred ms, in which they are slowed down to energies comparable to that of the cool ( less, similar 10 eV) background plasma before being annihilated.

  4. Initial Plasma Startup Test on SUNIST Spherical Tokamak

    NASA Astrophysics Data System (ADS)

    Wang, Ying; Zeng, Li; He, Yexi; SUNIST Team

    2003-12-01

    The goal of the Sino-United Spherical Tokamak (SUNIST) at Tsinghua University is to extend the understanding of toroidal plasma physics at a low aspect ratio (R/a approx 1.3) and to demonstrate a maintainable target plasma by non-inductive startup. The SUNIST device is designed to operate with up to 13 kA of ohmic heating field current, and to 0.15 T of toroidal field at 10 kA of discharge current. All of the poloidal fields can provide 30 mVs of Volt-seconds transformer. Experimental results of plasma startup show that SUNIST has remarkable characteristics of high ramp rate (dIP/dt approx 50 MA/s), high normalized current IN of about 2.8 (IN = (IP/aBT), and high-efficiency (IP/IROD approx 0.4) production of plasma current while operating at a low toroidal field. Major disruption phenomena have not been observed from magnetic diagnostics of all testing shots. Initial discharges with 52 kA of plasma current (exceeding the designed value of 50 kA), 2 ms of pulse length and 50 MA/s of ramp rate have been achieved easily with pre-ionized filament.

  5. High speed cine film studies of plasma behaviour and plasma surface interactions in tokamaks

    NASA Astrophysics Data System (ADS)

    Goodall, D. H. J.

    1982-12-01

    High speed cine photography is a useful diagnostic aid for studying plasma behaviour and plasma surface interactions. Several workers have filmed discharges in tokamaks including ASDEX, DITE, DIVA, ISX, JFT2, TFR and PLT. These films are discussed and examples given of the observed phenomena which include plasma limiter interactions, diverted discharges, disruptions, magnetic islands and moving glowing objects often known as 'UFOs'. Examples of plasma structures in ASDEX and DITE not previously published are also given. The paper also reports experiments in DITE to determine the origin of UFOs.

  6. Helical temperature perturbations associated with tearing modes in tokamak plasmas

    SciTech Connect

    Fitzpatrick, R.

    1994-06-01

    An investigation is made into the electron temperature perturbations associated with tearing modes in tokamak plasmas, with a view to determining the mode structure using Electron Cyclotron Emission (ECE) data. It is found that there is a critical magnetic island width below which the conventional picture where the temperature is flattened inside the separatrix is invalid. This effect comes about because of the stagnation of magnetic field lines in the vicinity of the rational surface and the finite parallel thermal conductivity of the plasma. For islands whose widths lie below the critical value there is no flattening of the electron temperature inside the separatrix. Such islands have quite different ECE signatures to conventional magnetic islands. In fact the two island types could, in principle, be differentiated experimentally. It should also be possible to map out the outer ideal magnetohydrodynamical eigenfunctions using ECE data. Islands whose widths are much less than the critical value are not destabilized by the perturbed bootstrap current, unlike conventional magnetic islands. This effect is found to have a number of very interesting consequences and may, indeed, provide an explanation for some puzzling experimental results regarding error field induced magnetic reconnection. All islands whose widths are much greater than the critical width possess a boundary layer on the separatrix which enables heat to be transported from one side of the island to the other via the X-point region. The structure of this boundary layer is described in some detail. Finally, the critical island width is found to be fairly substantial in conventional tokamak plasmas, provided that the long mean free path nature of parallel heat transport and the anomalous nature of perpendicular heat transport are taken into account in the calculation.

  7. ADX: A high Power Density, Advanced RF-Driven Divertor Test Tokamak for PMI studies

    NASA Astrophysics Data System (ADS)

    Whyte, Dennis; ADX Team

    2015-11-01

    The MIT PSFC and collaborators are proposing an advanced divertor experiment, ADX; a divertor test tokamak dedicated to address critical gaps in plasma-material interactions (PMI) science, and the world fusion research program, on the pathway to FNSF/DEMO. Basic ADX design features are motivated and discussed. In order to assess the widest range of advanced divertor concepts, a large fraction (>50%) of the toroidal field volume is purpose-built with innovative magnetic topology control and flexibility for assessing different surfaces, including liquids. ADX features high B-field (>6 Tesla) and high global power density (P/S ~ 1.5 MW/m2) in order to access the full range of parallel heat flux and divertor plasma pressures foreseen for reactors, while simultaneously assessing the effect of highly dissipative divertors on core plasma/pedestal. Various options for efficiently achieving high field are being assessed including the use of Alcator technology (cryogenic cooled copper) and high-temperature superconductors. The experimental platform would also explore advanced lower hybrid current drive and ion-cyclotron range of frequency actuators located at the high-field side; a location which is predicted to greatly reduce the PMI effects on the launcher while minimally perturbing the core plasma. The synergistic effects of high-field launchers with high total B on current and flow drive can thus be studied in reactor-relevant boundary plasmas.

  8. OVERVIEW OF RECENT EXPERIMENTAL RESULTS FROM THE DIII-D ADVANCED TOKAMAK PROGRAM

    SciTech Connect

    BURRELL,HK

    2002-11-01

    OAK A271 OVERVIEW OF RECENT EXPERIMENTAL RESULTS FROM THE DIII-D ADVANCED TOKAMAK PROGRAM. The DIII-D research program is developing the scientific basis for advanced tokamak (AT) modes of operation in order to enhance the attractiveness of the tokamak as an energy producing system. Since the last International Atomic Energy Agency (IAEA) meeting, they have made significant progress in developing the building blocks needed for AT operation: (1) they have doubled the magnetohydrodynamic (MHD) stable tokamak operating space through rotational stabilization of the resistive wall mode; (2) using this rotational stabilization, they have achieved {beta}{sub N}H{sub 89} {ge} 10 for 4 {tau}{sub E} limited by the neoclassical tearing mode; (3) using real-time feedback of the electron cyclotron current drive (ECCD) location, they have stabilized the (m,n) = (3,2) neoclassical tearing mode and then increased {beta}{sub T} by 60%; (4) they have produced ECCD stabilization of the (2,1) neoclassical tearing mode in initial experiments; (5) they have made the first integrated AT demonstration discharges with current profile control using ECCD; (6) ECCD and electron cyclotron heating (ECH) have been used to control the pressure profile in high performance plasmas; and (7) they have demonstrated stationary tokamak operation for 6.5 s (36 {tau}{sub E}) at the same fusion gain parameter of {beta}{sub N}H{sub 89}/q{sub 95}{sup 2} {approx} 0.4 as ITER but at much higher q{sub 95} = 4.2. The authors have developed general improvements applicable to conventional and advanced tokamak operating modes: (1) they have an existence proof of a mode of tokamak operation, quiescent H-mode, which has no pulsed, ELM heat load to the divertor and which can run for long periods of time (3.8 s or 25 {tau}{sub E}) with constant density and constant radiated power; (2) they have demonstrated real-time disruption detection and mitigation for vertical disruption events using high pressure gas jet

  9. Performance of a New Ion Source for KSTAR Tokamak Plasma Heating

    NASA Astrophysics Data System (ADS)

    Tae-Seong, Kim; Seung, Ho Jeong; Doo, Hee Chang; Kwang, Won Lee; Sang-Ryul, In

    2014-06-01

    In the experimental campaign of 2010 and 2011 on KSTAR, the NBI-1 system was equipped with one prototype ion source and operated successfully, providing a neutral beam power of 0.7-1.6 MW to the tokamak plasma. The new ion source planned for the 2012 KSTAR campaign had a much more advanced performance compared with the previous one. The target performance of the new ion source was to provide a neutral deuterium beam of 2 MW to the tokamak plasma. The ion source was newly designed, fabricated, and assembled in 2011. The new ion source was then conditioned up to 64 A/100 keV over a 2-hour beam extraction and performance tested at the NB test stand (NBTS) at the Korea Atomic Energy Research Institute (KAERI) in 2012. The measured optimum perveance at which the beam divergence is a minimum was about 2.5 μP, and the minimum beam divergent angle was under 1.0° at 60 keV. These results indicate that the 2.0 MW neutral beam power at 100 keV required for the heating of plasma in KSTAR can be delivered by the installation of the new ion source in the KSTAR NBI-1 system.

  10. New dual gas puff imaging system with up-down symmetry on experimental advanced superconducting tokamak

    NASA Astrophysics Data System (ADS)

    Liu, S. C.; Shao, L. M.; Zweben, S. J.; Xu, G. S.; Guo, H. Y.; Cao, B.; Wang, H. Q.; Wang, L.; Yan, N.; Xia, S. B.; Zhang, W.; Chen, R.; Chen, L.; Ding, S. Y.; Xiong, H.; Zhao, Y.; Wan, B. N.; Gong, X. Z.; Gao, X.

    2012-12-01

    Gas puff imaging (GPI) offers a direct and effective diagnostic to measure the edge turbulence structure and velocity in the edge plasma, which closely relates to edge transport and instability in tokamaks. A dual GPI diagnostic system has been installed on the low field side on experimental advanced superconducting tokamak (EAST). The two views are up-down symmetric about the midplane and separated by a toroidal angle of 66.6°. A linear manifold with 16 holes apart by 10 mm is used to form helium gas cloud at the 130×130 mm (radial versus poloidal) objective plane. A fast camera is used to capture the light emission from the image plane with a speed up to 390 804 frames/s with 64×64 pixels and an exposure time of 2.156 μs. The spatial resolution of the system is 2 mm at the objective plane. A total amount of 200 Pa.L helium gas is puffed into the plasma edge for each GPI viewing region for about 250 ms. The new GPI diagnostic has been applied on EAST for the first time during the recent experimental campaign under various plasma conditions, including ohmic, L-mode, and type-I, and type-III ELMy H-modes. Some of these initial experimental results are also presented.

  11. In situ ``artificial plasma'' calibration of tokamak magnetic sensors

    NASA Astrophysics Data System (ADS)

    Shiraki, D.; Levesque, J. P.; Bialek, J.; Byrne, P. J.; DeBono, B. A.; Mauel, M. E.; Maurer, D. A.; Navratil, G. A.; Pedersen, T. S.; Rath, N.

    2013-06-01

    A unique in situ calibration technique has been used to spatially calibrate and characterize the extensive new magnetic diagnostic set and close-fitting conducting wall of the High Beta Tokamak-Extended Pulse (HBT-EP) experiment. A new set of 216 Mirnov coils has recently been installed inside the vacuum chamber of the device for high-resolution measurements of magnetohydrodynamic phenomena including the effects of eddy currents in the nearby conducting wall. The spatial positions of these sensors are calibrated by energizing several large in situ calibration coils in turn, and using measurements of the magnetic fields produced by the various coils to solve for each sensor's position. Since the calibration coils are built near the nominal location of the plasma current centroid, the technique is referred to as an "artificial plasma" calibration. The fitting procedure for the sensor positions is described, and results of the spatial calibration are compared with those based on metrology. The time response of the sensors is compared with the evolution of the artificial plasma current to deduce the eddy current contribution to each signal. This is compared with simulations using the VALEN electromagnetic code, and the modeled copper thickness profiles of the HBT-EP conducting wall are adjusted to better match experimental measurements of the eddy current decay. Finally, the multiple coils of the artificial plasma system are also used to directly calibrate a non-uniformly wound Fourier Rogowski coil on HBT-EP.

  12. Identification of new turbulence contributions to plasma transport and confinement in spherical tokamak regime

    DOE PAGES

    Wang, W. X.; Ethier, S.; Ren, Y.; Kaye, S.; Chen, J.; Startsev, E.; Lu, Z.; Li, Z. Q.

    2015-10-15

    Highly distinct features of spherical tokamaks (ST), such as National Spherical Torus eXperiment (NSTX) and NSTX-U, result in a different fusion plasma regime with unique physics properties compared to conventional tokamaks. Nonlinear global gyrokinetic simulations critical for addressing turbulence and transport physics in the ST regime have led to new insights. The drift wave Kelvin-Helmholtz (KH) instability characterized by intrinsic mode asymmetry is identified in strongly rotating NSTX L-mode plasmas. While the strong E x B shear associated with the rotation leads to a reduction in KH/ion temperature gradient turbulence, the remaining fluctuations can produce a significant ion thermal transportmore » that is comparable to the experimental level in the outer core region (with no "transport shortfall"). The other new, important turbulence source identified in NSTX is the dissipative trapped electron mode (DTEM), which is believed to play little role in conventional tokamak regime. Due to the high fraction of trapped electrons, long wavelength DTEMs peaking around kθρs ~ 0.1 are destabilized in NSTX collisionality regime by electron density and temperature gradients achieved there. Surprisingly, the E x B shear stabilization effect on DTEM is remarkably weak, which makes it a major turbulence source in the ST regime dominant over collisionless TEM (CTEM). The latter, on the other hand, is subject to strong collisional and E x B shear suppression in NSTX. DTEM is shown to produce significant particle, energy and toroidal momentum transport, in agreement with experimental levels in NSTX H-modes. Furthermore, DTEM-driven transport in NSTX parametric regime is found to increase with electron collision frequency, providing one possible source for the scaling of confinement time observed in NSTX H-modes. Most interestingly, the existence of a turbulence-free regime in the collision-induced CTEM to DTEM transition, corresponding to a minimum plasma transport in

  13. Identification of new turbulence contributions to plasma transport and confinement in spherical tokamak regime

    SciTech Connect

    Wang, W. X.; Ethier, S.; Ren, Y.; Kaye, S.; Chen, J.; Startsev, E.; Lu, Z.; Li, Z. Q.

    2015-10-15

    Highly distinct features of spherical tokamaks (ST), such as National Spherical Torus eXperiment (NSTX) and NSTX-U, result in a different fusion plasma regime with unique physics properties compared to conventional tokamaks. Nonlinear global gyrokinetic simulations critical for addressing turbulence and transport physics in the ST regime have led to new insights. The drift wave Kelvin-Helmholtz (KH) instability characterized by intrinsic mode asymmetry is identified in strongly rotating NSTX L-mode plasmas. While the strong E x B shear associated with the rotation leads to a reduction in KH/ion temperature gradient turbulence, the remaining fluctuations can produce a significant ion thermal transport that is comparable to the experimental level in the outer core region (with no "transport shortfall"). The other new, important turbulence source identified in NSTX is the dissipative trapped electron mode (DTEM), which is believed to play little role in conventional tokamak regime. Due to the high fraction of trapped electrons, long wavelength DTEMs peaking around kθρs ~ 0.1 are destabilized in NSTX collisionality regime by electron density and temperature gradients achieved there. Surprisingly, the E x B shear stabilization effect on DTEM is remarkably weak, which makes it a major turbulence source in the ST regime dominant over collisionless TEM (CTEM). The latter, on the other hand, is subject to strong collisional and E x B shear suppression in NSTX. DTEM is shown to produce significant particle, energy and toroidal momentum transport, in agreement with experimental levels in NSTX H-modes. Furthermore, DTEM-driven transport in NSTX parametric regime is found to increase with electron collision frequency, providing one possible source for the scaling of confinement time observed in NSTX H-modes. Most interestingly, the existence of a turbulence-free regime in the collision-induced CTEM to DTEM transition, corresponding to a minimum plasma

  14. Investigation of relativistic runaway electrons in electron cyclotron resonance heating discharges on Korea Superconducting Tokamak Advanced Research

    SciTech Connect

    Kang, C. S.; Lee, S. G.

    2014-07-15

    The behavior of relativistic runaway electrons during Electron Cyclotron Resonance Heating (ECRH) discharges is investigated in the Korea Superconducting Tokamak Advanced Research device. The effect of the ECRH on the runaway electron population is discussed. Observations on the generation of superthermal electrons during ECRH will be reported, which will be shown to be consistent with existing theory for the development of a superthermal electron avalanche during ECRH [A. Lazaros, Phys. Plasmas 8, 1263 (2001)].

  15. Theory of self-organized critical transport in tokamak plasmas

    SciTech Connect

    Kishimoto, Y.; Tajima, T.; Horton, W.; LeBrun, M.J.; Kim, J.Y. |

    1995-07-01

    A theoretical and computational study of the ion temperature gradient and {eta}{sub i} instabilities in tokamak plasmas has been carried out. In toroidal geometry the modes have a radially extended structure and their eigenfrequencies are constant over many rational surfaces that are coupled through toroidicity. These nonlocal properties of the ITG modes impose strong constraint on the drift mode fluctuations and the amciated transport, showing a self-organized characteristic. As any significant deviation away from marginal stability causes rapid temperature relaxation and intermittent bursts, the modes hover near marginality and exhibit strong kinetic characteristics. As a result, the temperature relaxation is self-semilar and nonlocal, leading to a radially increasing heat diffusivity. The nonlocal transport leads to the Bohm-like diffusion scaling. The heat input regulates the deviation of the temperature gradient away from marginality. The obtained transport scalings and properties are globally consistent with experimental observations of L-mode charges.

  16. Continuum kinetic modeling of the tokamak plasma edge

    DOE PAGES

    Dorf, M. A.; Dorr, M.; Rognlien, T.; Hittinger, J.; Cohen, R.

    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

  17. Study of internal transport barrier triggering mechanism in tokamak plasmas

    SciTech Connect

    Dong, J.Q.; Mou, Z.Z.; Long, Y.X.; Mahajan, S.M.

    2004-12-01

    Sheared flow layers driven by magnetic energy, released in tearing-reconnection processes inherent in dissipative magnetohydrodynamics, are proposed as a triggering mechanism for the creation of the internal transport barrier (ITB) in tokamak plasmas. The double tearing mode, mediated by anomalous electron viscosity in configurations with a nonmonotonic safety factor, is investigated as an example. Particular emphasis is placed on the formation of sheared poloidal flow layers in the vicinity of the magnetic islands. A quasilinear simulation demonstrates that the sheared flows induced by the mode have desirable characteristics (lying just outside the magnetic islands), and sufficient levels required for ITB formation. A possible explanation is also proffered for the experimental observation that the transport barriers are preferentially formed in the proximity of low-order rational surfaces.

  18. MINERVA: Ideal MHD stability code for toroidally rotating tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Aiba, N.; Tokuda, S.; Furukawa, M.; Snyder, P. B.; Chu, M. S.

    2009-08-01

    A new linear MHD stability code MINERVA is developed for investigating a toroidal rotation effect on the stability of ideal MHD modes in tokamak plasmas. This code solves the Frieman-Rotenberg equation as not only the generalized eigenvalue problem but also the initial value problem. The parallel computing method used in this code realizes the stability analysis of both long and short wavelength MHD modes in short time. The results of some benchmarking tests show the validity of this MINERVA code. The numerical study with MINERVA about the toroidal rotation effect on the edge MHD stability shows that the rotation shear destabilizes the intermediate wavelength modes but stabilizes the short wavelength edge localized MHD modes, though the rotation frequency destabilizes both the long and the short wavelength MHD modes.

  19. RF wave propagation and scattering in turbulent tokamak plasmas

    SciTech Connect

    Horton, W. Michoski, C.; Peysson, Y.; Decker, J.

    2015-12-10

    Drift wave turbulence driven by the steep electron and ion temperature gradients in H-mode divertor tokamaks produce scattering of the RF waves used for heating and current drive. The X-ray emission spectra produced by the fast electrons require the turbulence broaden RF wave spectrum. Both the 5 GHz Lower Hybrid waves and the 170 GHz electron cyclotron [EC] RF waves experience scattering and diffraction by the electron density fluctuations. With strong LHCD there are bifurcations in the coupled turbulent transport dynamics giving improved steady-state confinement states. The stochastic scattering of the RF rays makes the prediction of the distribution of the rays and the associated particle heating a statistical problem. Thus, we introduce a Fokker-Planck equation for the probably density of the RF rays. The general frame work of the coupled system of coupled high frequency current driving rays with the low-frequency turbulent transport determines the profiles of the plasma density and temperatures.

  20. RF wave propagation and scattering in turbulent tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Horton, W.; Michoski, C.; Peysson, Y.; Decker, J.

    2015-12-01

    Drift wave turbulence driven by the steep electron and ion temperature gradients in H-mode divertor tokamaks produce scattering of the RF waves used for heating and current drive. The X-ray emission spectra produced by the fast electrons require the turbulence broaden RF wave spectrum. Both the 5 GHz Lower Hybrid waves and the 170 GHz electron cyclotron [EC] RF waves experience scattering and diffraction by the electron density fluctuations. With strong LHCD there are bifurcations in the coupled turbulent transport dynamics giving improved steady-state confinement states. The stochastic scattering of the RF rays makes the prediction of the distribution of the rays and the associated particle heating a statistical problem. Thus, we introduce a Fokker-Planck equation for the probably density of the RF rays. The general frame work of the coupled system of coupled high frequency current driving rays with the low-frequency turbulent transport determines the profiles of the plasma density and temperatures.

  1. 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

  2. Theory of self-organized critical transport in tokamak plasmas

    SciTech Connect

    Kishimoto, Y.; Tajima, T.; Horton, W.; LeBrun, M.J.; Kim, J.Y.

    1996-04-01

    A theoretical and computational study of the ion temperature gradient (ITG) and {eta}{sub {ital i}} instabilities in tokamak plasmas has been carried out. In a toroidal geometry the modes have a radially extended structure and their eigenfrequencies are constant over many rational surfaces that are coupled through toroidicity. These nonlocal properties of the ITG modes impose a strong constraint on the drift mode fluctuations and the associated transport, showing self-organized criticality. As any significant deviation away from marginal stability causes rapid temperature relaxation and intermittent bursts, the modes hover near marginality and exhibit strong kinetic characteristics. As a result of this, the temperature relaxation is self-similar and nonlocal, leading to radially increasing heat diffusivity. The nonlocal transport leads to Bohm-like diffusion scaling. Heat input regulates the deviation of the temperature gradient away from marginality. We present a critical gradient transport model that describes such a self-organized relaxed state. Some of the important aspects in tokamak transport like Bohm diffusion, near marginal stability, radially increasing fluctuation energy and heat diffusivity, intermittency of the wave excitation, and resilient tendency of the plasma profile can be described by this model, and these prominent features are found to belong to one physical category that originates from the radially extended nonlocal drift modes. The obtained transport properties and scalings are globally consistent with experimental observations of low confinement mode (L-mode) discharges. The nonlocal modes can be disintegrated into smaller radial islands by a poloidal shear flow, suggesting that the transport changes from Bohm-like to near gyro-Bohm. {copyright} {ital 1996 American Institute of Physics.}

  3. Transport of Dust Particles in Tokamak Devices

    SciTech Connect

    Pigarov, A Y; Smirnov, R D; Krasheninnikov, S I; Rognlien, T D; Rozenberg, M

    2006-06-06

    Recent advances in the dust transport modeling in tokamak devices are discussed. Topics include: (1) physical model for dust transport; (2) modeling results on dynamics of dust particles in plasma; (3) conditions necessary for particle growth in plasma; (4) dust spreading over the tokamak; (5) density profiles for dust particles and impurity atoms associated with dust ablation in tokamak plasma; and (6) roles of dust in material/tritium migration.

  4. Application of visible bremsstrahlung to Z{sub eff} measurement on the Experimental Advanced Superconducting Tokamak

    SciTech Connect

    Chen, Yingjie; Wu, Zhenwei; Gao, Wei; Ti, Ang; Zhang, Ling; Jie, Yinxian; Zhang, Jizong; Huang, Juan; Xu, Zong; Zhao, Junyu

    2015-02-15

    The multi-channel visible bremsstrahlung measurement system has been developed on Experimental Advanced Superconducting Tokamak (EAST). In addition to providing effective ion charge Z{sub eff} as a routine diagnostic, this diagnostic can also be used to estimate other parameters. With the assumption that Z{sub eff} can be seen as constant across the radius and does not change significantly during steady state discharges, central electron temperature, averaged electron density, electron density profile, and plasma current density profile have been obtained based on the scaling of Z{sub eff} with electron density and the relations between Z{sub eff} and these parameters. The estimated results are in good coincidence with measured values, providing an effective and convenient method to estimate other plasma parameters.

  5. Application of visible bremsstrahlung to Z(eff) measurement on the Experimental Advanced Superconducting Tokamak.

    PubMed

    Chen, Yingjie; Wu, Zhenwei; Gao, Wei; Ti, Ang; Zhang, Ling; Jie, Yinxian; Zhang, Jizong; Huang, Juan; Xu, Zong; Zhao, Junyu

    2015-02-01

    The multi-channel visible bremsstrahlung measurement system has been developed on Experimental Advanced Superconducting Tokamak (EAST). In addition to providing effective ion charge Zeff as a routine diagnostic, this diagnostic can also be used to estimate other parameters. With the assumption that Zeff can be seen as constant across the radius and does not change significantly during steady state discharges, central electron temperature, averaged electron density, electron density profile, and plasma current density profile have been obtained based on the scaling of Zeff with electron density and the relations between Zeff and these parameters. The estimated results are in good coincidence with measured values, providing an effective and convenient method to estimate other plasma parameters.

  6. Drift-tearing magnetic islands in tokamak plasmas

    SciTech Connect

    Fitzpatrick, R.; Waelbroeck, F. L.

    2008-01-15

    A systematic fluid theory of nonlinear magnetic island dynamics in conventional low-{beta}, large aspect-ratio, circular cross-section tokamak plasmas is developed using an extended magnetohydrodynamics model that incorporates diamagnetic flows, ion gyroviscosity, fast parallel electron heat transport, the ion sound wave, the drift wave, and average magnetic field-line curvature. The model excludes the compressible Alfven wave, geodesic field-line curvature, neoclassical effects, and ion Landau damping. A collisional closure is used for plasma dynamics parallel to the magnetic field. Two distinct branches of island solutions are found, namely the 'sonic' and 'hypersonic' branches. Both branches are investigated analytically, using suitable ordering schemes, and in each case the problem is reduced to a relatively simple set of nonlinear differential equations that can be solved numerically via iteration. The solution determines the island phase velocity, relative to the plasma, and the effect of local currents on the island stability. Sonic islands are relatively wide, flatten both the temperature and density profiles, and tend to propagate close to the local ion fluid velocity. Hypersonic islands, on the other hand, are relatively narrow, only flatten the temperature profile, radiate drift-acoustic waves, and tend to propagate close to the local electron fluid velocity. The hypersonic solution branch ceases to exist above a critical island width. Under normal circumstances, both types of island are stabilized by local ion polarization currents.

  7. The residual zonal flow in tokamak plasmas toroidally rotating at arbitrary velocity

    SciTech Connect

    Zhou, Deng

    2014-08-15

    Zonal flows, initially driven by ion-temperature-gradient turbulence, may evolve due to the neoclassic polarization in a collisionless tokamak plasma. In our previous work [D. Zhou, Nucl. Fusion 54, 042002 (2014)], the residual zonal flow in a tokamak plasma rotating toroidally at sonic speed is found to have the same form as that of a static plasma. In the present work, the form of the residual zonal flow is presented for tokamak plasmas rotating toroidally at arbitrary velocity. The gyro-kinetic equation is analytically solved for low speed rotation to give the expression of residual zonal flows, and the expression is then generalized for cases with arbitrary rotating velocity through interpolation. The zonal flow level decreases as the rotating velocity increases. The numerical evaluation is in good agreement with the former simulation result for high aspect ratio tokamaks.

  8. Design of vibration compensation interferometer for Experimental Advanced Superconducting Tokamak.

    PubMed

    Yang, Y; Li, G S; Liu, H Q; Jie, Y X; Ding, W X; Brower, D L; Zhu, X; Wang, Z X; Zeng, L; Zou, Z Y; Wei, X C; Lan, T

    2014-11-01

    A vibration compensation interferometer (wavelength at 0.532 μm) has been designed and tested for Experimental Advanced Superconducting Tokamak (EAST). It is designed as a sub-system for EAST far-infrared (wavelength at 432.5 μm) poloarimeter/interferometer system. Two Acoustic Optical Modulators have been applied to produce the 1 MHz intermediate frequency. The path length drift of the system is lower than 2 wavelengths within 10 min test, showing the system stability. The system sensitivity has been tested by applying a periodic vibration source on one mirror in the system. The vibration is measured and the result matches the source period. The system is expected to be installed on EAST by the end of 2014.

  9. Emission in the 50-80 A region from highly ionized silver in PLT tokamak plasmas

    SciTech Connect

    Schwob, J.L.; Wouters, A.; Suckewer, S.; Cohen, S.A.; Finkenthal, M.

    1985-09-01

    The spectrum of silver emitted by Princeton Large Torus (PLT) tokamak plasmas has been recorded in the 25 to 150 A region by a multichannel time-resolving grazing-incidence spectrometer. Silver atoms have been introduced in the tokamak plasma using the laser blow-off technique. For the first time, lines emitted within the 3p-3d transitions of Ag XXIX, Ag XXX, and Ag XXXI ions, between 50 and 80 A, have been identified.

  10. Kinetic modelling of runaway electron avalanches in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Nilsson, E.; Decker, J.; Peysson, Y.; Granetz, R. S.; Saint-Laurent, F.; Vlainic, M.

    2015-09-01

    Runaway electrons can be generated in tokamak plasmas if the accelerating force from the toroidal electric field exceeds the collisional drag force owing to Coulomb collisions with the background plasma. In ITER, disruptions are expected to generate runaway electrons mainly through knock-on collisions (Hender et al 2007 Nucl. Fusion 47 S128-202), where enough momentum can be transferred from existing runaways to slow electrons to transport the latter beyond a critical momentum, setting off an avalanche of runaway electrons. Since knock-on runaways are usually scattered off with a significant perpendicular component of the momentum with respect to the local magnetic field direction, these particles are highly magnetized. Consequently, the momentum dynamics require a full 3D kinetic description, since these electrons are highly sensitive to the magnetic non-uniformity of a toroidal configuration. For this purpose, a bounce-averaged knock-on source term is derived. The generation of runaway electrons from the combined effect of Dreicer mechanism and knock-on collision process is studied with the code LUKE, a solver of the 3D linearized bounce-averaged relativistic electron Fokker-Planck equation (Decker and Peysson 2004 DKE: a fast numerical solver for the 3D drift kinetic equation Report EUR-CEA-FC-1736, Euratom-CEA), through the calculation of the response of the electron distribution function to a constant parallel electric field. The model, which has been successfully benchmarked against the standard Dreicer runaway theory now describes the runaway generation by knock-on collisions as proposed by Rosenbluth (Rosenbluth and Putvinski 1997 Nucl. Fusion 37 1355-62). This paper shows that the avalanche effect can be important even in non-disruptive scenarios. Runaway formation through knock-on collisions is found to be strongly reduced when taking place off the magnetic axis, since trapped electrons can not contribute to the runaway electron population. Finally, the

  11. Two Fluid Kelvin-Helmholtz Instability in a Tokamak Plasma

    NASA Astrophysics Data System (ADS)

    Lopez Ortiz, Omar; Guazzotto, Luca

    2015-11-01

    For the study of equilibrium configurations of tokamak plasmas when toroidal and poloidal flows are present, single and two fluid models are available in the literature. In the two fluid description there appears a component of the poloidal velocity perpendicular to the magnetic flux surfaces, which does not occur in a single fluid description. As an illustration of the impact the normal velocity has on the stability of a plasma, we investigate its effect on a Kelvin-Helmholtz instability driven by a radial gradient in the toroidal flow. The analysis is performed by consistently using single and two fluid equations. The model considers an approximate high beta equilibrium configuration obtained by asymptotically expanding a functional for the single fluid Grad-Shafranov Bernoulli system of equations in terms of the inverse aspect ratio. The normal component of the velocity comes from two fluid theory and it represents a small correction to the single fluid poloidal velocity. The equilibrium and stability analysis is pursued with an analytic approach.

  12. Nonlinear transport processes in tokamak plasmas. I. The collisional regimes

    SciTech Connect

    Sonnino, Giorgio; Peeters, Philippe

    2008-06-15

    An application of the thermodynamic field theory (TFT) to transport processes in L-mode tokamak plasmas is presented. The nonlinear corrections to the linear ('Onsager') transport coefficients in the collisional regimes are derived. A quite encouraging result is the appearance of an asymmetry between the Pfirsch-Schlueter (P-S) ion and electron transport coefficients: the latter presents a nonlinear correction, which is absent for the ions, and makes the radial electron coefficients much larger than the former. Explicit calculations and comparisons between the neoclassical results and the TFT predictions for Joint European Torus (JET) plasmas are also reported. It is found that the nonlinear electron P-S transport coefficients exceed the values provided by neoclassical theory by a factor that may be of the order 10{sup 2}. The nonlinear classical coefficients exceed the neoclassical ones by a factor that may be of order 2. For JET, the discrepancy between experimental and theoretical results for the electron losses is therefore significantly reduced by a factor 10{sup 2} when the nonlinear contributions are duly taken into account but, there is still a factor of 10{sup 2} to be explained. This is most likely due to turbulence. The expressions of the ion transport coefficients, determined by the neoclassical theory in these two regimes, remain unaltered. The low-collisional regimes, i.e., the plateau and the banana regimes, are analyzed in the second part of this work.

  13. 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.

  14. Lessons learned from the tokamak Advanced Reactor Innovation and Evaluation Study (ARIES)

    SciTech Connect

    Krakowski, R.A.; Bathke, C.G.; Miller, R.L.; Werley, K.A.

    1994-07-01

    Lessons from the four-year ARIES (Advanced Reactor Innovation and Evaluation Study) investigation of a number of commercial magnetic-fusion-energy (MFE) power-plant embodiments of the tokamak are summarized. These lessons apply to physics, engineering and technology, and environmental, safety, and health (ES&H) characteristics of projected tokamak power plants. Summarized herein are the composite conclusions and lessons developed in the course of four conceptual tokamak power-plant designs. A general conclusion from this extensive investigation of the commercial potential of tokamak power plants is the need for combined, symbiotic advances in both physics, engineering, and materials before economic competitiveness with developing advanced energy sources can be realized. Advances in materials are also needed for the exploitation of environmental advantages otherwise inherent in fusion power.

  15. Plasma Position Measurements in a Tokamak with an Iron Core Transformer

    NASA Astrophysics Data System (ADS)

    Kwon, Gi-Chung; Choe, W.; Kim, Jayhyun; Yi, Hyo-Suk; Jeon, Sang-Jean; Huh, Songwhe; Chang, Hong-Young; Choi, Duk-In

    2000-07-01

    Two simple methods of estimating the plasma position in a large-aspect-ratio, low-βp tokamak with an iron core transformer are demonstrated: a magnetic diagnostic method and an optical method. The magnetic diagnostic method utilizes an array of magnetic pickup coils to measure the poloidal magnetic field produced by the plasma current. To include the effects of toroidicity and an iron core transformer, the correction factor was calculated with the magnetic material (or iron core) inside the calculation domain and incorporated in the analysis. The evolution of horizontal and vertical displacement of the plasma center obtained in this way is used to control the KAIST-Tokamak plasmas. To compare the plasma position estimated using the magnetic pickup coils, a simple optical method is also demonstrated on KAIST-TOKAMAK using a composite video signal from a charge-coupled device (CCD) camera. The two results are in good agreement.

  16. The Tokamak Fusion Test Reactor decontamination and decommissioning project and the Tokamak Physics Experiment at the Princeton Plasma Physics Laboratory. Environmental Assessment

    SciTech Connect

    1994-05-27

    If the US is to meet the energy needs of the future, it is essential that new technologies emerge to compensate for dwindling supplies of fossil fuels and the eventual depletion of fissionable uranium used in present-day nuclear reactors. Fusion energy has the potential to become a major source of energy for the future. Power from fusion energy would provide a substantially reduced environmental impact as compared with other forms of energy generation. Since fusion utilizes no fossil fuels, there would be no release of chemical combustion products to the atmosphere. Additionally, there are no fission products formed to present handling and disposal problems, and runaway fuel reactions are impossible due to the small amounts of deuterium and tritium present. The purpose of the TPX Project is to support the development of the physics and technology to extend tokamak operation into the continuously operating (steady-state) regime, and to demonstrate advances in fundamental tokamak performance. The purpose of TFTR D&D is to ensure compliance with DOE Order 5820.2A ``Radioactive Waste Management`` and to remove environmental and health hazards posed by the TFTR in a non-operational mode. There are two proposed actions evaluated in this environmental assessment (EA). The actions are related because one must take place before the other can proceed. The proposed actions assessed in this EA are: the decontamination and decommissioning (D&D) of the Tokamak Fusion Test Reactor (TFTR); to be followed by the construction and operation of the Tokamak Physics Experiment (TPX). Both of these proposed actions would take place primarily within the TFTR Test Cell Complex at the Princeton Plasma Physics Laboratory (PPPL). The TFTR is located on ``D-site`` at the James Forrestal Campus of Princeton University in Plainsboro Township, Middlesex County, New Jersey, and is operated by PPPL under contract with the United States Department of Energy (DOE).

  17. 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.

  18. Extended neoclassical transport theory for incompressible tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Shaing, K. C.

    1997-09-01

    Conventional neoclassical transport theory is extended to include the effects of orbit squeezing, and to allow the effective poloidal Mach number UpM=[(V∥/vt)+(VEB/vtBp)] of the order of unity for incompressible tokamak plasmas. Here, V∥ is the parallel mass flow, vt is the ion thermal speed, VE is the poloidal E×B drift speed, B is the magnetic field strength, and Bp is the poloidal magnetic field strength. It is found that ion thermal conductivity is reduced from its conventional neoclassical value in both banana and plateau regimes if UpM>1 and S>1. Here, S=[1+cI2Φ''/(Ω0B0)] is the orbit squeezing factor with c the speed of light, I=RBt, R the major radius, Φ the electrostatic potential, B0 the magnetic field strength on the axis, Ω0=eB0/Mc, M the ion mass, e the ion charge, Φ''=d2Φ/dψ2, and ψ the poloidal flux function. However, there is an irreducible minimum for the ion thermal conductivity in the banana-plateau regime set by the conventional Pfirsch-Schlüter transport.

  19. Development of an alternating integrator for magnetic measurements for experimental advanced superconducting tokamak.

    PubMed

    Liu, D M; Wan, B N; Zhao, W Z; Shen, B; He, Y G; Chen, B; Huang, J; Liu, H Q

    2014-11-01

    A high-performance integrator is one of the key electronic devices for reliably controlling plasma in the experimental advanced superconducting tokamak for long pulse operation. We once designed an integrator system of real-time drift compensation, which has a low integration drift. However, it is not feasible for really continuous operations due to capacitive leakage error and nonlinearity error. To solve the above-mentioned problems, this paper presents a new alternating integrator. In the new integrator, the integrator system of real-time drift compensation is adopted as one integral cell while two such integral cells work alternately. To achieve the alternate function, a Field Programmable Gate Array built in the digitizer is utilized. The performance test shows that the developed integrator with the integration time constant of 20 ms has a low integration drift (<15 mV) for 1000 s.

  20. Development of an alternating integrator for magnetic measurements for experimental advanced superconducting tokamak

    SciTech Connect

    Liu, D. M. Zhao, W. Z.; He, Y. G.; Chen, B.; Wan, B. N.; Shen, B.; Huang, J.; Liu, H. Q.

    2014-11-15

    A high-performance integrator is one of the key electronic devices for reliably controlling plasma in the experimental advanced superconducting tokamak for long pulse operation. We once designed an integrator system of real-time drift compensation, which has a low integration drift. However, it is not feasible for really continuous operations due to capacitive leakage error and nonlinearity error. To solve the above-mentioned problems, this paper presents a new alternating integrator. In the new integrator, the integrator system of real-time drift compensation is adopted as one integral cell while two such integral cells work alternately. To achieve the alternate function, a Field Programmable Gate Array built in the digitizer is utilized. The performance test shows that the developed integrator with the integration time constant of 20 ms has a low integration drift (<15 mV) for 1000 s.

  1. ADVANCES IN COMPREHENSIVE GYROKINETIC SIMULATIONS OF TRANSPORT IN TOKAMAKS

    SciTech Connect

    WALTZ RE; CANDY J; HINTON FL; ESTRADA-MILA C; KINSEY JE

    2004-10-01

    A continuum global gyrokinetic code GYRO has been developed to comprehensively simulate core turbulent transport in actual experimental profiles and enable direct quantitative comparisons to the experimental transport flows. GYRO not only treats the now standard ion temperature gradient (ITG) mode turbulence, but also treats trapped and passing electrons with collisions and finite {beta}, equilibrium ExB shear stabilization, and all in real tokamak geometry. Most importantly the code operates at finite relative gyroradius ({rho}{sub *}) so as to treat the profile shear stabilization and nonlocal effects which can break gyroBohm scaling. The code operates in either a cyclic flux-tube limit (which allows only gyroBohm scaling) or a globally with physical profile variation. Rohm scaling of DIII-D L-mode has been simulated with power flows matching experiment within error bars on the ion temperature gradient. Mechanisms for broken gyroBohm scaling, neoclassical ion flows embedded in turbulence, turbulent dynamos and profile corrugations, plasma pinches and impurity flow, and simulations at fixed flow rather than fixed gradient are illustrated and discussed.

  2. Spectroscopy of smooth deuterated carbon films redeposited from plasma discharge in the tokamak T-10

    SciTech Connect

    Svechnikov, N. Yu. Stankevich, V. G.; Lebedev, A. M.; Men'shikov, K. A.; Kolbasov, B. N.; Kriventsov, V. V.

    2006-12-15

    Smooth deuterated carbon films redeposited from a deuterium plasma discharge in the tokamak T-10 vacuum chamber have been investigated by different spectroscopic methods and temperature measurements. The photoluminescence excitation spectra of sp{sup 3}-sp{sup 2} nanostructures of tokamak films and sp{sup 2} nanostructures of fullerite C60 films are compared. The effect of defect states on the photoluminescence and its temperature quenching is discussed. It is concluded that the mechanism of thermal luminescence quenching for smooth deuterated tokamak films is close to the corresponding mechanism for amorphous a-C:H films.

  3. Combined hydrogen and lithium beam emission spectroscopy observation system for Korea Superconducting Tokamak Advanced Research.

    PubMed

    Lampert, M; Anda, G; Czopf, A; Erdei, G; Guszejnov, D; Kovácsik, Á; Pokol, G I; Réfy, D; Nam, Y U; Zoletnik, S

    2015-07-01

    A novel beam emission spectroscopy observation system was designed, built, and installed onto the Korea Superconducting Tokamak Advanced Research tokamak. The system is designed in a way to be capable of measuring beam emission either from a heating deuterium or from a diagnostic lithium beam. The two beams have somewhat complementary capabilities: edge density profile and turbulence measurement with the lithium beam and two dimensional turbulence measurement with the heating beam. Two detectors can be used in parallel: a CMOS camera provides overview of the scene and lithium beam light intensity distribution at maximum few hundred Hz frame rate, while a 4 × 16 pixel avalanche photo-diode (APD) camera gives 500 kHz bandwidth data from a 4 cm × 16 cm region. The optics use direct imaging through lenses and mirrors from the observation window to the detectors, thus avoid the use of costly and inflexible fiber guides. Remotely controlled mechanisms allow adjustment of the APD camera's measurement location on a shot-to-shot basis, while temperature stabilized filter holders provide selection of either the Doppler shifted deuterium alpha or lithium resonance line. The capabilities of the system are illustrated by measurements of basic plasma turbulence properties. PMID:26233377

  4. Combined hydrogen and lithium beam emission spectroscopy observation system for Korea Superconducting Tokamak Advanced Research

    NASA Astrophysics Data System (ADS)

    Lampert, M.; Anda, G.; Czopf, A.; Erdei, G.; Guszejnov, D.; Kovácsik, Á.; Pokol, G. I.; Réfy, D.; Nam, Y. U.; Zoletnik, S.

    2015-07-01

    A novel beam emission spectroscopy observation system was designed, built, and installed onto the Korea Superconducting Tokamak Advanced Research tokamak. The system is designed in a way to be capable of measuring beam emission either from a heating deuterium or from a diagnostic lithium beam. The two beams have somewhat complementary capabilities: edge density profile and turbulence measurement with the lithium beam and two dimensional turbulence measurement with the heating beam. Two detectors can be used in parallel: a CMOS camera provides overview of the scene and lithium beam light intensity distribution at maximum few hundred Hz frame rate, while a 4 × 16 pixel avalanche photo-diode (APD) camera gives 500 kHz bandwidth data from a 4 cm × 16 cm region. The optics use direct imaging through lenses and mirrors from the observation window to the detectors, thus avoid the use of costly and inflexible fiber guides. Remotely controlled mechanisms allow adjustment of the APD camera's measurement location on a shot-to-shot basis, while temperature stabilized filter holders provide selection of either the Doppler shifted deuterium alpha or lithium resonance line. The capabilities of the system are illustrated by measurements of basic plasma turbulence properties.

  5. Combined hydrogen and lithium beam emission spectroscopy observation system for Korea Superconducting Tokamak Advanced Research

    SciTech Connect

    Lampert, M.; Anda, G.; Réfy, D.; Zoletnik, S.; Czopf, A.; Erdei, G.; Guszejnov, D.; Kovácsik, Á.; Pokol, G. I.; Nam, Y. U.

    2015-07-15

    A novel beam emission spectroscopy observation system was designed, built, and installed onto the Korea Superconducting Tokamak Advanced Research tokamak. The system is designed in a way to be capable of measuring beam emission either from a heating deuterium or from a diagnostic lithium beam. The two beams have somewhat complementary capabilities: edge density profile and turbulence measurement with the lithium beam and two dimensional turbulence measurement with the heating beam. Two detectors can be used in parallel: a CMOS camera provides overview of the scene and lithium beam light intensity distribution at maximum few hundred Hz frame rate, while a 4 × 16 pixel avalanche photo-diode (APD) camera gives 500 kHz bandwidth data from a 4 cm × 16 cm region. The optics use direct imaging through lenses and mirrors from the observation window to the detectors, thus avoid the use of costly and inflexible fiber guides. Remotely controlled mechanisms allow adjustment of the APD camera’s measurement location on a shot-to-shot basis, while temperature stabilized filter holders provide selection of either the Doppler shifted deuterium alpha or lithium resonance line. The capabilities of the system are illustrated by measurements of basic plasma turbulence properties.

  6. Combined hydrogen and lithium beam emission spectroscopy observation system for Korea Superconducting Tokamak Advanced Research.

    PubMed

    Lampert, M; Anda, G; Czopf, A; Erdei, G; Guszejnov, D; Kovácsik, Á; Pokol, G I; Réfy, D; Nam, Y U; Zoletnik, S

    2015-07-01

    A novel beam emission spectroscopy observation system was designed, built, and installed onto the Korea Superconducting Tokamak Advanced Research tokamak. The system is designed in a way to be capable of measuring beam emission either from a heating deuterium or from a diagnostic lithium beam. The two beams have somewhat complementary capabilities: edge density profile and turbulence measurement with the lithium beam and two dimensional turbulence measurement with the heating beam. Two detectors can be used in parallel: a CMOS camera provides overview of the scene and lithium beam light intensity distribution at maximum few hundred Hz frame rate, while a 4 × 16 pixel avalanche photo-diode (APD) camera gives 500 kHz bandwidth data from a 4 cm × 16 cm region. The optics use direct imaging through lenses and mirrors from the observation window to the detectors, thus avoid the use of costly and inflexible fiber guides. Remotely controlled mechanisms allow adjustment of the APD camera's measurement location on a shot-to-shot basis, while temperature stabilized filter holders provide selection of either the Doppler shifted deuterium alpha or lithium resonance line. The capabilities of the system are illustrated by measurements of basic plasma turbulence properties.

  7. Impurity effects on trapped electron mode in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Du, Huarong; Wang, Zheng-Xiong; Dong, J. Q.

    2016-07-01

    The effects of impurity ions on the trapped electron mode (TEM) in tokamak plasmas are numerically investigated with the gyrokinetic integral eigenmode equation. It is shown that in the case of large electron temperature gradient ( η e ), the impurity ions have stabilizing effects on the TEM, regardless of peaking directions of their density profiles for all normalized electron density gradient R / L n e . Here, R is the major radius and L n e is the electron density gradient scale length. In the case of intermediate and/or small η e , the light impurity ions with conventional inwardly (outwardly) peaked density profiles have stabilizing effects on the TEM for large (small) R / L n e , while the light impurity ions with steep inwardly (outwardly) peaked density profiles can destabilize the TEM for small (large) R / L n e . Besides, the TEM driven by density gradient is stabilized (destabilized) by the light carbon or oxygen ions with inwardly (outwardly) peaked density profiles. In particular, for flat and/or moderate R / L n e , two independent unstable modes, corresponding respectively to the TEM and impurity mode, are found to coexist in plasmas with impurity ions of outwardly peaked density profiles. The high Z tungsten impurity ions play a stronger stabilizing role in the TEM than the low Z impurity ions (such as carbon and oxygen) do. In addition, the effects of magnetic shear and collision on the TEM instability are analyzed. It is shown that the collisionality considered in this work weakens the trapped electron response, leading to a more stable TEM instability, and that the stabilizing effects of the negative magnetic shear on the TEM are more significant when the impurity ions with outwardly peaked density profile are taken into account.

  8. Tokamak plasma equilibrium problems with anisotropic pressure and rotation and their numerical solution

    SciTech Connect

    Ivanov, A. A. Martynov, A. A. Medvedev, S. Yu. Poshekhonov, Yu. Yu.

    2015-03-15

    In the MHD tokamak plasma theory, the plasma pressure is usually assumed to be isotropic. However, plasma heating by neutral beam injection and RF heating can lead to a strong anisotropy of plasma parameters and rotation of the plasma. The development of MHD equilibrium theory taking into account the plasma inertia and anisotropic pressure began a long time ago, but until now it has not been consistently applied in computational codes for engineering calculations of the plasma equilibrium and evolution in tokamak. This paper contains a detailed derivation of the axisymmetric plasma equilibrium equation in the most general form (with arbitrary rotation and anisotropic pressure) and description of the specialized version of the SPIDER code. The original method of calculation of the equilibrium with an anisotropic pressure and a prescribed rotational transform profile is proposed. Examples of calculations and discussion of the results are also presented.

  9. First results on disruption mitigation by massive gas injection in Korea Superconducting Tokamak Advanced Research

    SciTech Connect

    Yu Yaowei; Kim, Young-Ok; Kim, Hak-Kun; Kim, Hong-Tack; Kim, Woong-Chae; Kim, Kwang-Pyo; Son, Soo-Hyun; Bang, Eun-Nam; Hong, Suk-Ho; Yoon, Si-Woo; Zhuang Huidong; Chen Zhongyong

    2012-12-15

    Massive gas injection (MGI) system was developed on Korea Superconducting Tokamak Advanced Research (KSTAR) in 2011 campaign for disruption studies. The MGI valve has a volume of 80 ml and maximum injection pressure of 50 bar, the diameter of valve orifice to vacuum vessel is 18.4 mm, the distance between MGI valve and plasma edge is {approx}3.4 m. The MGI power supply employs a large capacitor of 1 mF with the maximum voltage of 3 kV, the valve can be opened in less than 0.1 ms, and the amount of MGI can be controlled by the imposed voltage. During KSTAR 2011 campaign, MGI disruptions are carried out by triggering MGI during the flat top of circular and limiter discharges with plasma current 400 kA and magnetic field 2-3.5 T, deuterium injection pressure 39.7 bar, and imposed voltage 1.1-1.4 kV. The results show that MGI could mitigate the heat load and prevent runaway electrons with proper MGI amount, and MGI penetration is deeper under higher amount of MGI or lower magnetic field. However, plasma start-up is difficult after some of D{sub 2} MGI disruptions due to the high deuterium retention and consequently strong outgassing of deuterium in next shot, special effort should be made to get successful plasma start-up after deuterium MGI under the graphite first wall.

  10. First results on disruption mitigation by massive gas injection in Korea Superconducting Tokamak Advanced Research

    NASA Astrophysics Data System (ADS)

    Yu, Yaowei; Kim, Young-Ok; Kim, Hak-Kun; Kim, Hong-Tack; Kim, Woong-Chae; Kim, Kwang-Pyo; Son, Soo-Hyun; Bang, Eun-Nam; Zhuang, Huidong; Chen, Zhongyong; Hong, Suk-Ho; Yoon, Si-Woo

    2012-12-01

    Massive gas injection (MGI) system was developed on Korea Superconducting Tokamak Advanced Research (KSTAR) in 2011 campaign for disruption studies. The MGI valve has a volume of 80 ml and maximum injection pressure of 50 bar, the diameter of valve orifice to vacuum vessel is 18.4 mm, the distance between MGI valve and plasma edge is ˜3.4 m. The MGI power supply employs a large capacitor of 1 mF with the maximum voltage of 3 kV, the valve can be opened in less than 0.1 ms, and the amount of MGI can be controlled by the imposed voltage. During KSTAR 2011 campaign, MGI disruptions are carried out by triggering MGI during the flat top of circular and limiter discharges with plasma current 400 kA and magnetic field 2-3.5 T, deuterium injection pressure 39.7 bar, and imposed voltage 1.1-1.4 kV. The results show that MGI could mitigate the heat load and prevent runaway electrons with proper MGI amount, and MGI penetration is deeper under higher amount of MGI or lower magnetic field. However, plasma start-up is difficult after some of D2 MGI disruptions due to the high deuterium retention and consequently strong outgassing of deuterium in next shot, special effort should be made to get successful plasma start-up after deuterium MGI under the graphite first wall.

  11. First results on disruption mitigation by massive gas injection in Korea Superconducting Tokamak Advanced Research.

    PubMed

    Yu, Yaowei; Kim, Young-Ok; Kim, Hak-Kun; Kim, Hong-Tack; Kim, Woong-Chae; Kim, Kwang-Pyo; Son, Soo-Hyun; Bang, Eun-Nam; Zhuang, Huidong; Chen, Zhongyong; Hong, Suk-Ho; Yoon, Si-Woo

    2012-12-01

    Massive gas injection (MGI) system was developed on Korea Superconducting Tokamak Advanced Research (KSTAR) in 2011 campaign for disruption studies. The MGI valve has a volume of 80 ml and maximum injection pressure of 50 bar, the diameter of valve orifice to vacuum vessel is 18.4 mm, the distance between MGI valve and plasma edge is ~3.4 m. The MGI power supply employs a large capacitor of 1 mF with the maximum voltage of 3 kV, the valve can be opened in less than 0.1 ms, and the amount of MGI can be controlled by the imposed voltage. During KSTAR 2011 campaign, MGI disruptions are carried out by triggering MGI during the flat top of circular and limiter discharges with plasma current 400 kA and magnetic field 2-3.5 T, deuterium injection pressure 39.7 bar, and imposed voltage 1.1-1.4 kV. The results show that MGI could mitigate the heat load and prevent runaway electrons with proper MGI amount, and MGI penetration is deeper under higher amount of MGI or lower magnetic field. However, plasma start-up is difficult after some of D(2) MGI disruptions due to the high deuterium retention and consequently strong outgassing of deuterium in next shot, special effort should be made to get successful plasma start-up after deuterium MGI under the graphite first wall.

  12. Plasma boundary determination in Damavand tokamak by using current filament method

    NASA Astrophysics Data System (ADS)

    Ghadiri, Rasoul; Sadeghi, Yahya; Esteki, Mohammad Hossein

    2014-05-01

    The shape and position of the plasma and consequently the plasma boundary are determined by using the Current Filament (CF) method from the experimental data of the magnetic measurements in Damavand tokamak. The method can calculate the magnetic flux without solving the equilibrium equation directly by coupling with the Current Moment (CM) method. The plasma and current-carrying coils in the tokamak will be modeled by using this method as some virtual filaments that will enable us to calculate the flux and consequently the plasma boundary. To calculate the flux of these virtual filaments, one needs to determine the Green Function and the inverse by means of the Singular Value Decomposition (SVD) method. Finally, the model was evaluated by employing 12 independent pickup coils with mean error of less than 2%. The aim of this paper is to give a brief exposition of CF method applied in Damavand tokamak.

  13. A generalized plasma dispersion function for electron damping in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Berry, L. A.; Jaeger, E. F.; Phillips, C. K.; Lau, C. H.; Bertelli, N.; Green, D. L.

    2016-10-01

    Radio frequency wave propagation in finite temperature, magnetized plasmas exhibits a wide range of physics phenomena. The plasma response is nonlocal in space and time, and numerous modes are possible with the potential for mode conversions and transformations. In addition, diffraction effects are important due to finite wavelength and finite-size wave launchers. Multidimensional simulations are required to describe these phenomena, but even with this complexity, the fundamental plasma response is assumed to be the uniform plasma response with the assumption that the local plasma current for a Fourier mode can be described by the "Stix" conductivity. However, for plasmas with non-uniform magnetic fields, the wave vector itself is nonlocal. When resolved into components perpendicular (k⊥) and parallel (k||) to the magnetic field, locality of the parallel component can easily be violated when the wavelength is large. The impact of this inconsistency is that estimates of the wave damping can be incorrect (typically low) due to unresolved resonances. For the case of ion cyclotron damping, this issue has already been addressed by including the effect of parallel magnetic field gradients. In this case, a modified plasma response (Z function) allows resonance broadening even when k|| = 0, and this improves the convergence and accuracy of wave simulations. In this paper, we extend this formalism to include electron damping and find improved convergence and accuracy for parameters where electron damping is dominant, such as high harmonic fast wave heating in the NSTX-U tokamak, and helicon wave launch for off-axis current drive in the DIII-D tokamak.

  14. Poloidal rotation near the edge of a tokamak plasma in [ital H] mode

    SciTech Connect

    Hinton, F.L.; Kim, J.; Kim, Y.; Brizard, A.; Burrell, K.H. )

    1994-02-21

    Ion poloidal flow in tokamaks near the plasma edge has been calculated by extending neoclassical theory to include orbit squeezing, which is the reduction of the ion banana widths due to the gradient in the radial electric field. The calculated poloidal flow velocity is a significant fraction of the ion diamagnetic velocity, which can be much larger than the velocity predicted by neoclassical theory (proportional to the ion temperature gradient). The agreement with spectroscopic measurements of the poloidal rotation velocity in helium plasmas in the DIII-D tokamak is shown to be reasonably good very close to the plasma edge.

  15. Dynamic behavior of plasma-facing materials during plasma instabilities in tokamak reactors

    SciTech Connect

    Hassanein, A.; Konkashbaev, I.

    1997-09-01

    Damage to plasma-facing and nearby components due to plasma instabilities remains a major obstacle to a successful tokamak concept. The high energy deposited on facing materials during plasma instabilities can cause severe erosion, plasma contamination, and structural failure of these components. Erosion damage can take various forms such as surface vaporization, spallation, and liquid ejection of metallic materials. Comprehensive thermodynamic and radiation hydrodynamic codes have been developed, integrated, and used to evaluate the extent of various damage to plasma-facing and nearby components. The eroded and splashed materials will be transported and then redeposited elsewhere on other plasma-facing components. Detailed physics of plasma/solid-liquid/vapor interaction in a strong magnetic field have been developed, optimized, and implemented in a self-consistent model. The plasma energy deposited in the evolving divertor debris is quickly and intensely reradiated, which may cause severe erosion and melting of other nearby components. Factors that influence and reduce vapor-shielding efficiency such as vapor diffusion and turbulence are also discussed and evaluated.

  16. Extended neoclassical transport theory for incompressible tokamak plasmas

    SciTech Connect

    Shaing, K.C.

    1997-09-01

    Conventional neoclassical transport theory is extended to include the effects of orbit squeezing, and to allow the effective poloidal Mach number U{sub pM}=[(V{sub {parallel}}/v{sub t})+(V{sub E}B/v{sub t}B{sub p})] of the order of unity for incompressible tokamak plasmas. Here, V{sub {parallel}} is the parallel mass flow, v{sub t} is the ion thermal speed, V{sub E} is the poloidal {bold E{times}B} drift speed, B is the magnetic field strength, and B{sub p} is the poloidal magnetic field strength. It is found that ion thermal conductivity is reduced from its conventional neoclassical value in both banana and plateau regimes if U{sub pM}{gt}1 and S{gt}1. Here, S=[1+cI{sup 2}{Phi}{sup {prime}{prime}}/({Omega}{sub 0}B{sub 0})] is the orbit squeezing factor with c the speed of light, I=RB{sub t}, R the major radius, {Phi} the electrostatic potential, B{sub 0} the magnetic field strength on the axis, {Omega}{sub 0}=eB{sub 0}/Mc, M the ion mass, e the ion charge, {Phi}{sup {prime}{prime}}=d{sup 2}{Phi}/d{psi}{sup 2}, and {psi} the poloidal flux function. However, there is an irreducible minimum for the ion thermal conductivity in the banana-plateau regime set by the conventional Pfirsch{endash}Schl{umlt u}ter transport. {copyright} {ital 1997 American Institute of Physics.}

  17. Edge localized mode characteristics during edge localized mode mitigation by supersonic molecular beam injection in Korea Superconducting Tokamak Advanced Research

    NASA Astrophysics Data System (ADS)

    Lee, H. Y.; Hahn, S. H.; Ghim, Y.-C.; Bak, J. G.; Lee, J. H.; Ko, W. H.; Lee, K. D.; Lee, S. H.; Lee, H. H.; Juhn, J.-W.; Kim, H. S.; Yoon, S. W.; Han, H.; Hong, J. H.; Jang, J. H.; Park, J. S.; Choe, Wonho

    2015-12-01

    It has been reported that supersonic molecular beam injection (SMBI) is an effective means of edge localized mode (ELM) mitigation. This paper newly reports the changes in the ELM, plasma profiles, and fluctuation characteristics during ELM mitigation by SMBI in Korea Superconducting Tokamak Advanced Research. During the mitigated ELM phase, the ELM frequency increased by a factor of 2-3 and the ELM size, which was estimated from the Dα amplitude, the fractional changes in the plasma-stored energy and the line-averaged electron density, and divertor heat flux during an ELM burst, decreased by a factor of 0.34-0.43. Reductions in the electron and ion temperatures rather than in the electron density were observed during the mitigated ELM phase. In the natural ELM phase, frequency chirping of the plasma fluctuations was observed before the ELM bursts; however, the ELM bursts occurred without changes in the plasma fluctuation frequency in the mitigated ELM phase.

  18. Impedance of an intense plasma-cathode electron source for tokamak startup

    DOE PAGES

    Hinson, Edward Thomas; Barr, Jayson L.; Bongard, Michael W.; Burke, Marcus Galen; Fonck, Raymond J.; Perry, Justin M.

    2016-05-31

    In this study, an impedance model is formulated and tested for the ~1kV, ~1kA/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 the injected current, Iinj, increases with Vinj according to the standard double layer scaling Iinj ~ Vinj3/2 at low current and transitions to Iinj ~ Vinj1/2more » 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.« less

  19. Kinetic shear Alfvén instability in the presence of impurity ions in tokamak plasmas

    SciTech Connect

    Lu, Gaimin; Shen, Y.; Xie, T.; He, Zhixiong; He, Hongda; Qi, Longyu; Cui, Shaoyan

    2013-10-15

    The effects of impurity ions on the kinetic shear Alfvén (KSA) instability in tokamak plasmas are investigated by numerically solving the integral equations for the KSA eigenmode in the toroidal geometry. The kinetic effects of hydrogen and impurity ions, including transit motion, finite ion Larmor radius, and finite-orbit-width, are taken into account. Toroidicity induced linear mode coupling is included through the ballooning-mode representation. Here, the effects of carbon, oxygen, and tungsten ions on the KSA instability in toroidal plasmas are investigated. It is found that, depending on the concentration and density profile of the impurity ions, the latter can be either stabilizing or destabilizing for the KSA modes. The results here confirm the importance of impurity ions in tokamak experiments and should be useful for analyzing experimental data as well as for understanding anomalous transport and control of tokamak plasmas.

  20. Analysis of pedestal gradient characteristic on the Experimental Advanced Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Wang, Teng Fei; Han, Xiao Feng; Zang, Qing; Xiao, Shu Mei; Tian, Bao Gang; Hu, Ai Lan; Zhao, Jun Yu

    2016-05-01

    A pedestal database was built based on type I edge localized mode H-modes in the Experimental Advanced Superconducting Tokamak. The most common functional form hyperbolic tangent function (tanh) method is used to analyze pedestal characteristics. The pedestal gradient scales linearly with its pedestal top and the normalized pedestal pressure gradient α shows a strong correlation with electron collisionality. The connection among pedestal top value, gradient, and width is established with the normalized pedestal pressure gradient. In the core region of the plasma, the nature of the electron temperature stiffness reflects a proportionality between core and pedestal temperature while the increase proportion is lower than that expected in the high temperature region. However, temperature profile stiffness is limited or even disappears at the edge of the plasma, while the gradient length ratio ( ηe ) on the pedestal is important. The range of ηe is from 0.5 to 2, varying with the plasma parameters. The pedestal temperature brings a more significant impact on ηe than pedestal density.

  1. Impact of Stationary Direct Current in the Central Solenoidal Coil on Tokamak Plasma Formation by Non-induction Heating

    NASA Astrophysics Data System (ADS)

    Watanabe, Osamu

    2016-09-01

    Stationary direct current in the central solenoidal coil (DCCS) of tokamak devices can reduce the non-induction heating energy necessary for tokamak plasma formation. The magnetic field energy in the inner region of the central solenoidal coil (CS region) is expelled during the tokamak plasma formation, because the vertical magnetic field intensity generated by the central solenoidal coil and poloidal field coils is partly cancelled by the increase in the toroidal plasma current. Because this magnetic field energy expelled from the CS region is distributed to the tokamak plasma in accordance with the mutual inductance, this expelled energy can drive the toroidal plasma current inductively. This energy expulsion in the CS region can be enhanced by the DCCS without the modification of the tokamak plasma configuration, when the CS coil current has negligible leakage magnetic field in the plasma area. Because the drive of the toroidal plasma current by non-induction heating can be assisted by this inductive current drive mechanism, the non-induction heating energy necessary for the tokamak plasma formation can be reduced by the DCCS. If the non-induction heating is constant, the tokamak plasma formation time can be shorted by the DCCS.

  2. Gridded ionization chamber for detection of x-ray wave activity in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Goldman, M. A.; Hill, K. W.; Moshey, E. A.; Sauthoff, N. R.; von Goeler, S.

    1985-03-01

    In order to carry out x-ray observations of magnetohydrodynamic wave activity of the plasma during DD and DT (deuterium-beam-heated deuterium and tritium plasmas, respectively) operation of the Tokamak Fusion Test Reactor (TFTR), we will need detectors not susceptible to nuclear radiation damage. We have investigated the use of gridded ionization chambers as fast nondamageable x-ray detectors. A prototype chamber is described which was tested on the PDX tokamak. These tests and laboratory tests with a pulsed x-ray source suggest that the detector has sufficient sensitivity and speed for the required measurements.

  3. Gridded ionization chamber for detecion of x-ray wave activity in tokamak plasmas

    SciTech Connect

    Goldman, M.A.; Hill, K.W.; Moshey, E.A.; Sauthoff, N.R.; von Goeler, S.

    1982-11-01

    In order to carry out X-ray observations of magnetohydrodynamic wave activity of the plasma during DD and DT (deuterium-beam-heated deuterium and tritium plasmas, respectively) operation of the Tokamak Fusion Test Reactor (TFTR), we will need detectors not susceptible to nuclear radiation damage. We have investigated the use of gridded ionization chambers as fast nondamageable X-ray detectors. A prototype chamber is described, which was tested on the PDX tokamak. These tests and laboratory tests with a pulsed X-ray source suggest that the detector has sufficient sensitivity and speed for the required measurements.

  4. Tokamak Equilibria with Toroidal-Current Reversal in the Plasma Core Consistent with Experimental Data

    SciTech Connect

    Rodrigues, Paulo; Bizarro, Joao P. S.

    2007-09-21

    For the first time, tokamak equilibria with negative toroidal current flowing in the plasma core are computed consistently with available measurements from typical current-hole discharges. The equilibrium reconstruction, which leads to non-nested configurations where a system of axisymmetric magnetic islands unfolds, yields an overall good agreement between the computed and experimental plasma-pressure profiles, together with an excellent fit to motional-Stark-effect data. Therefore, considering the accuracy limits of present-day experimental results, care must be exercised when ruling out the existence of tokamak equilibria with central toroidal-current reversal, particularly if relying on reconstruction tools that cannot cope with non-nested configurations.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    Analysis of the time series obtained with the Doppler backscattering system (Hillsheim et al 2009 Rev. Sci. Instrum. 80 0835070) in the DIII-D tokamak (Luxon 2005 Fusion Sci. Technol. 48 828) shows that intermediate wave number plasma density fluctuations in low confinement (L-mode) tokamak plasmas are chaotic. 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) (Rosso et al 2007 Phys. Rev. Lett. 99 154102); and the population of the corresponding Bandt-Pompe (Bandt and Pompe 2002 Phys. Rev. Lett. 88 174102) probability distributions.

  6. Texas Experimental Tokamak, a plasma research facility: Technical progress report

    SciTech Connect

    Wootton, A.J.

    1995-08-01

    In the year just past, the authors made major progress in understanding turbulence and transport in both core and edge. Development of the capability for turbulence measurements throughout the poloidal cross section and intelligent consideration of the observed asymmetries, played a critical role in this work. In their confinement studies, a limited plasma with strong, H-mode-like characteristics serendipitously appeared and received extensive study though a diverted H-mode remains elusive. In the plasma edge, they appear to be close to isolating a turbulence drive mechanism. These are major advances of benefit to the community at large, and they followed from incremental improvements in diagnostics, in the interpretation of the diagnostics, and in TEXT itself. Their general philosophy is that the understanding of plasma physics must be part of any intelligent fusion program, and that basic experimental research is the most important part of any such program. The work here demonstrates a continuing dedication to the problems of plasma transport which continue to plague the community and are an impediment to the design of future devices. They expect to show here that they approach this problem consistently, systematically, and effectively.

  7. Generation of two-column helicon plasma on KAIST-TOKAMAK

    NASA Astrophysics Data System (ADS)

    Jeon, S. J.; Huh, S. W.; Kim, J.; Lee, T. S.; Moon, S. Y.; Choe, W.; Choi, D. I.

    2000-10-01

    Industrial plasma application studies reveal that helicon waves provide high ionization rate even at modest rf input power. This suggests that helicon waves be effectively used for plasma pre-ionization/startup, and plasma heating in a tokamak. The two-column helicon plasma was produced with a Nagoya type ¥2 antenna which was modified for toroidal geometry of KAIST-TOKAMAK. The observed two columns locate at the same major radius and they move outward as toroidal magnetic field increases. In addition to the 2D image captured by a CCD camera, an 8-channel Langmuir probe array is used to measure the density profile. Parallel wave number is measured by magnetic pickup probes and a phase detector in order to study wave generation and propagation inside the plasma.

  8. Rotation of weakly collisional plasmas in tokamaks, operated with Alfv{acute e}n waves

    SciTech Connect

    Tsypin, V.S.; Elfimov, A.G.; de Azevedo, C.A.; de Assis, A.S.

    1996-12-01

    The effect of the kinetic Alfv{acute e}n waves on weakly collisional plasma rotation in tokamaks has been studied for the plateau and banana regimes. The quasistationary rotation velocities and radial electric field have been found. The estimation of these quantities for the Phaedrus-T tokamak [S. Wukitch {ital et} {ital al}., Phys. Rev. Lett. {bold 77}, 294 (1996)] and for the Joint European Torus (JET) [A. Fasoli {ital et} {ital al}., Nucl. Fusion, {bold 36}, 258 (1996)] has been presented. It is shown that the kinetic Alfv{acute e}n waves, which are needed for current drive, change weakly the quasistationary rotation velocities and radial electric field, as found from the experimental data of these tokamaks. In conditions with increased rf power, the plasma rotation and radial electric field can essentially grow up. {copyright} {ital 1996 American Institute of Physics.}

  9. ELMy H-mode linear simulation with 3-field model on experimental advanced superconducting tokamak using BOUT++

    SciTech Connect

    Liu, Z. X.; Gao, X.; Liu, S. C.; Ding, S. Y.; Li, J. G.; Xia, T. Y.; Xu, X. Q.; Hughes, J. W.

    2012-10-15

    H-mode plasmas with ELM (edge localized mode) have been realized on experimental advanced superconducting tokamak (EAST) with 2.45 GHz low hybrid wave at P{sub LHW}{approx}1 MW in 2010. Data from EAST experiments including magnetic geometry, measured pressure profiles, and calculated current profiles are used to investigate the physics of ELM utilizing the BOUT++ code. Results from linear simulations show that the ELMs in EAST are dominated by resistive ballooning modes. When the Lundquist number (dimensionless ratio of the resistive diffusion time to the Alfven time) is equal to or less than 10{sup 7}, the resistive ballooning modes are found to become unstable in the ELMy H-mode plasma. For a fixed pedestal pressure profile, increasing plasma current generates more activities of low-n ELMs.

  10. 2-D Imaging of Electron Temperature in Tokamak Plasmas

    SciTech Connect

    T. Munsat; E. Mazzucato; H. Park; C.W. Domier; M. Johnson; N.C. Luhmann Jr.; J. Wang; Z. Xia; I.G.J. Classen; A.J.H. Donne; M.J. van de Pol

    2004-07-08

    By taking advantage of recent developments in millimeter wave imaging technology, an Electron Cyclotron Emission Imaging (ECEI) instrument, capable of simultaneously measuring 128 channels of localized electron temperature over a 2-D map in the poloidal plane, has been developed for the TEXTOR tokamak. Data from the new instrument, detailing the MHD activity associated with a sawtooth crash, is presented.

  11. Distinct turbulence sources and confinement features in the spherical tokamak plasma regime

    DOE PAGES

    Wang, W. X.; Ethier, S.; Ren, Y.; Kaye, S.; Chen, J.; Startsev, E.; Lu, Z.

    2015-10-30

    New turbulence contributions to plasma transport and confinement in the spherical tokamak (ST) regime are identified through nonlinear gyrokinetic simulations. The drift wave Kelvin-Helmholtz (KH) mode characterized by intrinsic mode asymmetry is shown to drive significant ion thermal transport in strongly rotating national spherical torus experiment (NSTX) L-modes. The long wavelength, quasi-coherent dissipative trapped electron mode (TEM) is destabilized in NSTX H-modes despite the presence of strong E x B shear, providing a robust turbulence source dominant over collisionless TEM. Dissipative trapped electron mode (DTEM)-driven transport in the NSTX parametric regime is shown to increase with electron collision frequency, offeringmore » one possible source for the confinement scaling observed in experiments. There exists a turbulence-free regime in the collision-induced collisionless trapped electron mode to DTEM transition for ST plasmas. In conclusion, this predicts a natural access to a minimum transport state in the low collisionality regime that future advanced STs may cover.« less

  12. Distinct turbulence sources and confinement features in the spherical tokamak plasma regime

    SciTech Connect

    Wang, W. X.; Ethier, S.; Ren, Y.; Kaye, S.; Chen, J.; Startsev, E.; Lu, Z.

    2015-10-30

    New turbulence contributions to plasma transport and confinement in the spherical tokamak (ST) regime are identified through nonlinear gyrokinetic simulations. The drift wave Kelvin-Helmholtz (KH) mode characterized by intrinsic mode asymmetry is shown to drive significant ion thermal transport in strongly rotating national spherical torus experiment (NSTX) L-modes. The long wavelength, quasi-coherent dissipative trapped electron mode (TEM) is destabilized in NSTX H-modes despite the presence of strong E x B shear, providing a robust turbulence source dominant over collisionless TEM. Dissipative trapped electron mode (DTEM)-driven transport in the NSTX parametric regime is shown to increase with electron collision frequency, offering one possible source for the confinement scaling observed in experiments. There exists a turbulence-free regime in the collision-induced collisionless trapped electron mode to DTEM transition for ST plasmas. In conclusion, this predicts a natural access to a minimum transport state in the low collisionality regime that future advanced STs may cover.

  13. Recent developments in Bayesian inference of tokamak plasma equilibria and high-dimensional stochastic quadratures

    NASA Astrophysics Data System (ADS)

    von Nessi, G. T.; Hole, M. J.; The MAST Team

    2014-11-01

    We present recent results and technical breakthroughs for the Bayesian inference of tokamak equilibria using force-balance as a prior constraint. Issues surrounding model parameter representation and posterior analysis are discussed and addressed. These points motivate the recent advancements embodied in the Bayesian Equilibrium Analysis and Simulation Tool (BEAST) software being presently utilized to study equilibria on the Mega-Ampere Spherical Tokamak (MAST) experiment in the UK (von Nessi et al 2012 J. Phys. A 46 185501). State-of-the-art results of using BEAST to study MAST equilibria are reviewed, with recent code advancements being systematically presented though out the manuscript.

  14. Edge multi-energy soft x-ray diagnostic in Experimental Advanced Superconducting Tokamak

    SciTech Connect

    Li, Y. L.; Xu, G. S.; Wan, B. N.; Lan, H.; Liu, Y. L.; Wei, J.; Zhang, W.; Hu, G. H.; Wang, H. Q.; Duan, Y. M.; Zhao, J. L.; Wang, L.; Liu, S. C.; Ye, Y.; Li, J.; Lin, X.; Li, X. L.; Tritz, K.; Zhu, Y. B.

    2015-12-15

    A multi-energy soft x-ray (ME-SXR) diagnostic has been built for electron temperature profile in the edge plasma region in Experimental Advanced Superconducting Tokamak (EAST) after two rounds of campaigns. Originally, five preamplifiers were mounted inside the EAST vacuum vessel chamber attached to five vertically stacked compact diode arrays. A custom mechanical structure was designed to protect the detectors and electronics under constraints of the tangential field of view for plasma edge and the allocation of space. In the next experiment, the mechanical structure was redesigned with a barrel structure to absolutely isolate it from the vacuum vessel. Multiple shielding structures were mounted at the pinhole head to protect the metal foils from lithium coating. The pre-amplifiers were moved to the outside of the vacuum chamber to avoid introducing interference. Twisted copper cooling tube was embedded into the back-shell near the diode to limit the temperature of the preamplifiers and diode arrays during vacuum vessel baking when the temperature reached 150 °C. Electron temperature profiles were reconstructed from ME-SXR measurements using neural networks.

  15. Edge multi-energy soft x-ray diagnostic in Experimental Advanced Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Li, Y. L.; Xu, G. S.; Tritz, K.; Zhu, Y. B.; Wan, B. N.; Lan, H.; Liu, Y. L.; Wei, J.; Zhang, W.; Hu, G. H.; Wang, H. Q.; Duan, Y. M.; Zhao, J. L.; Wang, L.; Liu, S. C.; Ye, Y.; Li, J.; Lin, X.; Li, X. L.

    2015-12-01

    A multi-energy soft x-ray (ME-SXR) diagnostic has been built for electron temperature profile in the edge plasma region in Experimental Advanced Superconducting Tokamak (EAST) after two rounds of campaigns. Originally, five preamplifiers were mounted inside the EAST vacuum vessel chamber attached to five vertically stacked compact diode arrays. A custom mechanical structure was designed to protect the detectors and electronics under constraints of the tangential field of view for plasma edge and the allocation of space. In the next experiment, the mechanical structure was redesigned with a barrel structure to absolutely isolate it from the vacuum vessel. Multiple shielding structures were mounted at the pinhole head to protect the metal foils from lithium coating. The pre-amplifiers were moved to the outside of the vacuum chamber to avoid introducing interference. Twisted copper cooling tube was embedded into the back-shell near the diode to limit the temperature of the preamplifiers and diode arrays during vacuum vessel baking when the temperature reached 150 °C. Electron temperature profiles were reconstructed from ME-SXR measurements using neural networks.

  16. Edge multi-energy soft x-ray diagnostic in Experimental Advanced Superconducting Tokamak.

    PubMed

    Li, Y L; Xu, G S; Tritz, K; Zhu, Y B; Wan, B N; Lan, H; Liu, Y L; Wei, J; Zhang, W; Hu, G H; Wang, H Q; Duan, Y M; Zhao, J L; Wang, L; Liu, S C; Ye, Y; Li, J; Lin, X; Li, X L

    2015-12-01

    A multi-energy soft x-ray (ME-SXR) diagnostic has been built for electron temperature profile in the edge plasma region in Experimental Advanced Superconducting Tokamak (EAST) after two rounds of campaigns. Originally, five preamplifiers were mounted inside the EAST vacuum vessel chamber attached to five vertically stacked compact diode arrays. A custom mechanical structure was designed to protect the detectors and electronics under constraints of the tangential field of view for plasma edge and the allocation of space. In the next experiment, the mechanical structure was redesigned with a barrel structure to absolutely isolate it from the vacuum vessel. Multiple shielding structures were mounted at the pinhole head to protect the metal foils from lithium coating. The pre-amplifiers were moved to the outside of the vacuum chamber to avoid introducing interference. Twisted copper cooling tube was embedded into the back-shell near the diode to limit the temperature of the preamplifiers and diode arrays during vacuum vessel baking when the temperature reached 150 °C. Electron temperature profiles were reconstructed from ME-SXR measurements using neural networks.

  17. Different Methods for Measuring Plasma Displacement in Tokamaks, Construction and Compensation of Continuous Coils in IR-T1 Tokamak

    SciTech Connect

    Tarkeshian, R.; Atyabi, S. M.; Ghoranneviss, M.; Salem, K.; Talebi Taher, A.; Khorshid, P.

    2008-03-19

    The measurement of current-carrying plasma column displacement is very important for plasma position control. Two methods for this purpose are introduced. In this paper, calculation and construction of these coils is explained. Multiple moment method has been used and derived for construction of sensing coils Also Fourier Transform has been used and derived for continuous coils. The comparison of their advantages are investigated. For IR-T1 Tokamak, Two Cosine coils and two Saddle Sine coils were designed and constructed, which have been placed diametrically around minor radius of torus. Then an electronic circuit was designed for adding and integrating the Cosine and Saddle Sine coils output with proper gain. The contribution of each coils in final output is calculated. For compensation of unwanted pickups voltage from the time varying fields each signal with adjustable gain is added to main signal, until removing the additional field effects. The final output holds good proportionality to H.D.

  18. Limiter/vacuum system for plasma impurity control and exhaust in tokamaks

    SciTech Connect

    Abdou, M.; Brooks, J.; Mattas, R.

    1980-01-01

    A detailed design of a limiter/vacuum system for plasma impurity control and exhaust has been developed for the STARFIRE tokamak power plant. It is shown that the limiter/vacuum concept is a very attractive option for power reactors. It is relatively simple and inexpensive and deserves serious experimental verification.

  19. Resonance parallel viscosity in the banana regime in poloidally rotating tokamak plasmas

    SciTech Connect

    Shaing, K.C.; Hsu, C.T.; Dominguez, N. )

    1994-05-01

    Parallel viscosity in the banana regime in a poloidally ([bold E][times][bold B]) rotating tokamak plasma is calculated to include the effects of orbit squeezing and to allow the poloidal [bold E][times][bold B] Mach number [ital M][sub [ital p

  20. Effects of orbit squeezing on poloidal mass flow and bootstrap current in tokamak plasmas

    SciTech Connect

    Shaing, K.C. ); Hsu, C.T. ); Hazeltine, R.D. )

    1994-10-01

    It is shown, by solving the drift kinetic equation, that the asymptotic values of the poloidal mass flow and the bootstrap current in the banana regime of large-aspect-ratio tokamak plasmas are not affected by orbit squeezing. However, because the definition of ion collisionality [upsilon][sub *[ital i

  1. Plasma Physics found in JT-60 Tokamak over the Last 20 years

    SciTech Connect

    Kikuchi, M.

    2009-07-07

    This paper summarizes major plasma physics obtained during the period of JT-60 operation for 23 years with special emphasis on research towards steady-state operation of tokamak. Topics included are observation of large bootstrap current fraction, negative shear scenario, demonstration of efficient beam and EC current drive, discovery of current hole, stabilization of the RWM, discovery of ITB (internal transport barrier).

  2. Physics basis for an advanced physics and advanced technology tokamak power plant configuration: ARIES-ACT1

    SciTech Connect

    Kessel, C. E.; Poli, F. M.; Ghantous, K.; Gorelenkov, N. N.; Rensink, M. E.; Rognlien, T. D.; Snyder, P. B.; St. John, H.; Turnbull, A. D.

    2015-01-01

    Here, the advanced physics and advanced technology tokamak power plant ARIES-ACT1 has a major radius of 6.25 m at an aspect ratio of 4.0, toroidal field of 6.0 T, strong shaping with elongation of 2.2, and triangularity of 0.63. The broadest pressure cases reached wall-stabilized βN ~ 5.75, limited by n = 3 external kink mode requiring a conducting shell at b/a = 0.3, requiring plasma rotation, feedback, and/or kinetic stabilization. The medium pressure peaking case reaches βN = 5.28 with BT = 6.75, while the peaked pressure case reaches βN < 5.15. Fast particle magnetohydrodynamic stability shows that the alpha particles are unstable, but this leads to redistribution to larger minor radius rather than loss from the plasma. Edge and divertor plasma modeling shows that 75% of the power to the divertor can be radiated with an ITER-like divertor geometry, while >95% can be radiated in a stable detached mode with an orthogonal target and wide slot geometry. The bootstrap current fraction is 91% with a q95 of 4.5, requiring ~1.1 MA of external current drive. This current is supplied with 5 MW of ion cyclotron radio frequency/fast wave and 40 MW of lower hybrid current drive. Electron cyclotron is most effective for safety factor control over ρ~0.2 to 0.6 with 20 MW. The pedestal density is ~0.9×1020/m3, and the temperature is ~4.4 keV. The H98 factor is 1.65, n/nGr = 1.0, and the ratio of net power to threshold power is 2.8 to 3.0 in the flattop.

  3. The Physics Basis For An Advanced Physics And Advanced Technology Tokamak Power Plant Configuration, ARIES-ACT1

    SciTech Connect

    Charles Kessel, et al

    2014-03-05

    The advanced physics and advanced technology tokamak power plant ARIES-ACT1 has a major radius of 6.25 m at aspect ratio of 4.0, toroidal field of 6.0 T, strong shaping with elongation of 2.2 and triangularity of 0.63. The broadest pressure cases reached wall stabilized βN ~ 5.75, limited by n=3 external kink mode requiring a conducting shell at b/a = 0.3, and requiring plasma rotation, feedback, and or kinetic stabilization. The medium pressure peaking case reached βN = 5.28 with BT = 6.75, while the peaked pressure case reaches βN < 5.15. Fast particle MHD stability shows that the alpha particles are unstable, but this leads to redistribution to larger minor radius rather than loss from the plasma. Edge and divertor plasma modeling show that about 75% of the power to the divertor can be radiated with an ITER-like divertor geometry, while over 95% can be radiated in a stable detached mode with an orthogonal target and wide slot geometry. The bootstrap current fraction is 91% with a q95 of 4.5, requiring about ~ 1.1 MA of external current drive. This current is supplied with 5 MW of ICRF/FW and 40 MW of LHCD. EC was examined and is most effective for safety factor control over ρ ~ 0.2-0.6 with 20 MW. The pedestal density is ~ 0.9x1020 /m3 and the temperature is ~ 4.4 keV. The H98 factor is 1.65, n/nGr = 1.0, and the net power to LH threshold power is 2.8- 3.0 in the flattop.

  4. Physics basis for an advanced physics and advanced technology tokamak power plant configuration: ARIES-ACT1

    DOE PAGES

    Kessel, C. E.; Poli, F. M.; Ghantous, K.; Gorelenkov, N. N.; Rensink, M. E.; Rognlien, T. D.; Snyder, P. B.; St. John, H.; Turnbull, A. D.

    2015-01-01

    Here, the advanced physics and advanced technology tokamak power plant ARIES-ACT1 has a major radius of 6.25 m at an aspect ratio of 4.0, toroidal field of 6.0 T, strong shaping with elongation of 2.2, and triangularity of 0.63. The broadest pressure cases reached wall-stabilized βN ~ 5.75, limited by n = 3 external kink mode requiring a conducting shell at b/a = 0.3, requiring plasma rotation, feedback, and/or kinetic stabilization. The medium pressure peaking case reaches βN = 5.28 with BT = 6.75, while the peaked pressure case reaches βN < 5.15. Fast particle magnetohydrodynamic stability shows that themore » alpha particles are unstable, but this leads to redistribution to larger minor radius rather than loss from the plasma. Edge and divertor plasma modeling shows that 75% of the power to the divertor can be radiated with an ITER-like divertor geometry, while >95% can be radiated in a stable detached mode with an orthogonal target and wide slot geometry. The bootstrap current fraction is 91% with a q95 of 4.5, requiring ~1.1 MA of external current drive. This current is supplied with 5 MW of ion cyclotron radio frequency/fast wave and 40 MW of lower hybrid current drive. Electron cyclotron is most effective for safety factor control over ρ~0.2 to 0.6 with 20 MW. The pedestal density is ~0.9×1020/m3, and the temperature is ~4.4 keV. The H98 factor is 1.65, n/nGr = 1.0, and the ratio of net power to threshold power is 2.8 to 3.0 in the flattop.« less

  5. Physics Basis for the Advanced Tokamak Fusion Power Plant ARIES-AT

    SciTech Connect

    S.C. Jardin; C.E. Kessel; T.K. Mau; R.L. Miller; F. Najmabadi; V.S. Chan; M.S. Chu; R. LaHaye; L.L. Lao; T.W. Petrie; P. Politzer; H.E. St. John; P. Snyder; G.M. Staebler; A.D. Turnbull; W.P. West

    2003-10-07

    The advanced tokamak is considered as the basis for a fusion power plant. The ARIES-AT design has an aspect ratio of A always equal to R/a = 4.0, an elongation and triangularity of kappa = 2.20, delta = 0.90 (evaluated at the separatrix surface), a toroidal beta of beta = 9.1% (normalized to the vacuum toroidal field at the plasma center), which corresponds to a normalized beta of bN * 100 x b/(I(sub)P(MA)/a(m)B(T)) = 5.4. These beta values are chosen to be 10% below the ideal-MHD stability limit. The bootstrap-current fraction is fBS * I(sub)BS/I(sub)P = 0.91. This leads to a design with total plasma current I(sub)P = 12.8 MA, and toroidal field of 11.1 T (at the coil edge) and 5.8 T (at the plasma center). The major and minor radii are 5.2 and 1.3 m, respectively. The effects of H-mode edge gradients and the stability of this configuration to non-ideal modes is analyzed. The current-drive system consists of ICRF/FW for on-axis current drive and a lower-hybrid system for off-axis. Tran sport projections are presented using the drift-wave based GLF23 model. The approach to power and particle exhaust using both plasma core and scrape-off-layer radiation is presented.

  6. Influence of collisions on parametric instabilities induced by lower hybrid waves in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Castaldo, C.; Di Siena, A.; Fedele, R.; Napoli, F.; Amicucci, L.; Cesario, R.; Schettini, G.

    2016-01-01

    Parametric instabilities induced at the plasma edge by lower hybrid wave power externally coupled to tokamak plasmas have, via broadening of the antenna spectrum, strong influence on the power deposition and current drive in the core. For modeling the parametric instabilities at the tokamak plasma edge in lower hybrid current drive experiments, the effect of the collisions has been neglected so far. In the present work, a specific collisional parametric dispersion relation, useful to analyze these nonlinear phenomena near the lower hybrid antenna mouth, is derived for the first time, based on a kinetic model. Numerical solutions show that in such cold plasma regions the collisions prevent the onset of the parametric instabilities. This result is important for present lower hybrid current drive experiments, as well as in fusion reactor scenarios.

  7. Observation of ICRF (ion cyclotron range of frequencies) wave-packet propagation in a tokamak plasma

    SciTech Connect

    Greene, G.J.; Gould, R.W.

    1987-11-01

    Experimental observation of ICRF wave-packet propagation in a tokamak plasma is reported. Studies were carried out in the Caltech Research Tokamak in a pure hydrogen plasma and in a regime where fast-wave damping was sufficiently small to permit multiple toroidal transits of the wave-packet. Waves were launched by exciting a small loop antenna with a short burst of rf current and were detected with shielded magnetic probes. Probe scans revealed a large increase in wave-packet amplitude at smaller minor radii, and the packet velocity was found to be independent of radial position. Measurement of the packet transit time yielded direct information about the wave group velocity. Packet velocity was investigated as a function of the fundamental excitation frequency, plasma density, and toroidal magnetic field. Results are compared with the predictions of a cold plasma model which includes a vacuum layer at the edge. 24 refs., 8 figs.

  8. Role of neutral gas in scrape-off layer tokamak plasma

    SciTech Connect

    Bisai, N.; Jha, R.; Kaw, P. K.

    2015-02-15

    Neutral gas in scrape-off layer of tokamak plasma plays an important role as it can modify the plasma turbulence. In order to investigate this, we have derived a simple two-dimensional (2D) model that consists of electron continuity, quasi-neutrality, and neutral gas continuity equations using neutral gas ionization and charge exchange processes. Simple 1D profile analysis predicts neutral penetration depth into the plasma. Growth rate obtained from the linear theory has been presented. The 2D model equations have been solved numerically. It is found that the neutral gas reduces plasma fluctuations and shifts spectrum of the turbulence towards lower frequency side. The neutral gas fluctuation levels have been presented. The numerical results have been compared with Aditya tokamak experiments.

  9. Energy Confinement of High-Density Pellet-Fueled Plasmas in the Alcator C Tokamak

    NASA Astrophysics Data System (ADS)

    Greenwald, M.; Gwinn, D.; Milora, S.; Parker, J.; Parker, R.; Wolfe, S.; Besen, M.; Camacho, F.; Fairfax, S.; Fiore, C.; Foord, M.; Gandy, R.; Gomez, C.; Granetz, R.; Labombard, B.; Lipschultz, B.; Lloyd, B.; Marmar, E.; McCool, S.; Pappas, D.; Petrasso, R.; Pribyl, P.; Rice, J.; Schuresko, D.; Takase, Y.; Terry, J.; Watterson, R.

    1984-07-01

    A series of pellet-fueling experiments has been carried out on the Alcator C tokamak. High-speed hydrogen pellets penetrate to within a few centimeters of the magnetic axis, raise the plasma density, and produce peaked density profiles. Energy confinement is observed to increase over similar discharges fueled only by gas puffing. In this manner record values of electron density, plasma pressure, and Lawson number (n τ) have been achieved.

  10. 3D MHD VDE and disruptions simulations of tokamaks plasmas including some ITER scenarios

    NASA Astrophysics Data System (ADS)

    Paccagnella, R.; Strauss, H. R.; Breslau, J.

    2009-03-01

    Tokamaks vertical displacement events (VDEs) and disruptions simulations in toroidal geometry by means of a single fluid visco-resistive magneto-hydro-dynamic (MHD) model are presented in this paper. The plasma model is completed with the presence of a 2D wall with finite resistivity which allows the study of the relatively slowly growing magnetic perturbation, the resistive wall mode (RWM), which is, in this paper, the main drive of the disruption evolution. Amplitudes and asymmetries of the halo currents pattern at the wall are also calculated and comparisons with tokamak experimental databases and predictions for ITER are given.

  11. High βp plasma formation using off-axis ECCD in Ohmic heated plasma in the spherical tokamak QUEST

    NASA Astrophysics Data System (ADS)

    Mishra, Kishore; Zushi, H.; Idei, H.; Hasegawa, M.; Hanada, K.

    2015-03-01

    High poloidal beta (ɛβp ~ 1) operation in steady state condition in tokamaks is of great interest and has previously been demonstrated using NBI, LHCD and low current (Ip) plasma for a short time (<0.5 s). A very few experiments however, have been performed towards the investigation of highest obtainable βp in tokamak plasma. In this work we report the first result of high βp production and its sustainment though an off axis ECCD at two different frequencies (fundamental and second harmonic) in Ohmic (OH) target plasma. With application of ECCD, plasma βp increased to encounter an equilibrium limit and the standard limiter configuration is transformed to an Inboard Poloidal field Null (IPN) configuration. Both off-axis and on-axis ECCD is studied and found to have some distinctive features, which are discussed in this paper.

  12. Development of magnetohydrodynamic modes during sawteeth in tokamak plasmas

    SciTech Connect

    Firpo, M.-C.; Ettoumi, W.; Farengo, R.; Ferrari, H. E.; García-Martínez, P. L.; Lifschitz, A. F.

    2013-07-15

    A dynamical analysis applied to a reduced resistive magnetohydrodynamics model is shown to explain the chronology of the nonlinear destabilization of modes observed in tokamak sawteeth. A special emphasis is put on the nonlinear self-consistent perturbation of the axisymmetric m = n = 0 mode that manifests through the q-profile evolution. For the very low fusion-relevant resistivity values, the q-profile is shown to remain almost unchanged on the early nonlinear timescale within the central tokamak region, which supports a partial reconnection scenario. Within the resistive region, indications for a local flattening or even a local reversed-shear of the q-profile are given. The impact of this ingredient in the occurrence of the sawtooth crash is discussed.

  13. Advances in Dust Detection and Removal for Tokamaks

    NASA Astrophysics Data System (ADS)

    Campos, A.; Skinner, C. H.; Roquemore, A. L.; Leisure, J. O. V.; Wagner, S.

    2008-11-01

    Dust diagnostics and removal techniques are vital for the safe operation of next step fusion devices such as ITER. An electrostatic dust detector[1] developed in the laboratory is being applied to NSTX. In the tokamak environment, large particles or fibres can fall on the grid potentially causing a permanent short. We report on the development of a gas puff system that uses helium to clear such particles from the detector. Experiments with varying nozzle designs, backing pressures, puff durations, and exit flow orientations have obtained an optimal configuration that effectively removes particles from a 25 cm^2 area. Dust removal from next step tokamaks will be required to meet regulatory dust limits. A tripolar grid of fine interdigitated traces has been designed that generates an electrostatic travelling wave for conveying dust particles to a ``drain.'' First trials have shown particle motion in optical microscope images. [1] C. H. Skinner et al., J. Nucl. Mater., 376 (2008) 29.

  14. Supersonic molecular beam injection effects on tokamak plasma applied non-axisymmetric magnetic perturbation

    NASA Astrophysics Data System (ADS)

    Han, Hyunsun; In, Y.; Jeon, Y. M.; Lee, H. Y.; Hahn, S. H.; Lee, K. D.; Nam, Y. U.; Yoon, S. W.

    2016-08-01

    The change of tokamak plasma behavior by supersonic molecular beam injection (SMBI) was investigated by applying a three-dimensional magnetic perturbation that could suppress edge localized modes (ELMs). From the time trace of decreasing electron temperature and with increasing plasma density keeping the total confined energy constant, the SMBI seems to act as a cold pulse on the plasma. However, the ELM behaviors were changed drastically (i.e., the symptom of ELM suppression has disappeared). The plasma collisionality in the edge-pedestal region could play a role in the change of the ELM behaviors.

  15. Particle Control and Plasma Performance in the Lithium Tokamak Experiment (LTX)

    SciTech Connect

    Richard Majeski, et. al.

    2013-02-21

    The Lithium Tokamak eXperiment (LTX) is a small, low aspect ratio tokamak, which is fitted with a stainless steel-clad copper liner, conformal to the last closed flux surface. The liner can be heated to 350{degree}C. Several gas fueling systems, including supersonic gas injection, and molecular cluster injection have been studied, and produce fueling efficiencies up to 35%. Discharges are strongly affected by wall conditioning. Discharges without lithium wall coatings are limited to plasma currents of order 10 kA, and discharge durations of order 5 msec. With solid lithium coatings discharge currents exceed 70 kA, and discharge durations exceed 30 msec. Heating the lithium wall coating, however, results in a prompt degradation of the discharge, at the melting point of lithium. These results suggest that the simplest approach to implementing liquid lithium walls in a tokamak - thin, evaporated, liquefied coatings of lithium - does not produce an adequately clean surface.

  16. Can tokamaks PFC survive a single event of any plasma instabilities?

    NASA Astrophysics Data System (ADS)

    Hassanein, A.; Sizyuk, V.; Miloshevsky, G.; Sizyuk, T.

    2013-07-01

    Plasma instability events such as disruptions, edge-localized modes (ELMs), runaway electrons (REs), and vertical displacement events (VDEs) are continued to be serious events and most limiting factors for successful tokamak reactor concept. The plasma-facing components (PFCs), e.g., wall, divertor, and limited surfaces of a tokamak as well as coolant structure materials are subjected to intense particle and heat loads and must maintain a clean and stable surface environment among them and the core/edge plasma. Typical ITER transient events parameters are used for assessing the damage from these four different instability events. HEIGHTS simulation showed that a single event of a disruption, giant ELM, VDE, or RE can cause significant surface erosion (melting and vaporization) damage to PFC, nearby components, and/or structural materials (VDE, RE) melting and possible burnout of coolant tubes that could result in shut down of reactor for extended repair time.

  17. Control of magnetohydrodynamic stability by phase space engineering of energetic ions in tokamak plasmas.

    PubMed

    Graves, J P; Chapman, I T; Coda, S; Lennholm, M; Albergante, M; Jucker, M

    2012-01-01

    Virtually collisionless magnetic mirror-trapped energetic ion populations often partially stabilize internally driven magnetohydrodynamic disturbances in the magnetosphere and in toroidal laboratory plasma devices such as the tokamak. This results in less frequent but dangerously enlarged plasma reorganization. Unique to the toroidal magnetic configuration are confined 'circulating' energetic particles that are not mirror trapped. Here we show that a newly discovered effect from hybrid kinetic-magnetohydrodynamic theory has been exploited in sophisticated phase space engineering techniques for controlling stability in the tokamak. These theoretical predictions have been confirmed, and the technique successfully applied in the Joint European Torus. Manipulation of auxiliary ion heating systems can create an asymmetry in the distribution of energetic circulating ions in the velocity orientated along magnetic field lines. We show the first experiments in which large sawtooth collapses have been controlled by this technique, and neoclassical tearing modes avoided, in high-performance reactor-relevant plasmas. PMID:22233634

  18. Control of magnetohydrodynamic stability by phase space engineering of energetic ions in tokamak plasmas.

    PubMed

    Graves, J P; Chapman, I T; Coda, S; Lennholm, M; Albergante, M; Jucker, M

    2012-01-10

    Virtually collisionless magnetic mirror-trapped energetic ion populations often partially stabilize internally driven magnetohydrodynamic disturbances in the magnetosphere and in toroidal laboratory plasma devices such as the tokamak. This results in less frequent but dangerously enlarged plasma reorganization. Unique to the toroidal magnetic configuration are confined 'circulating' energetic particles that are not mirror trapped. Here we show that a newly discovered effect from hybrid kinetic-magnetohydrodynamic theory has been exploited in sophisticated phase space engineering techniques for controlling stability in the tokamak. These theoretical predictions have been confirmed, and the technique successfully applied in the Joint European Torus. Manipulation of auxiliary ion heating systems can create an asymmetry in the distribution of energetic circulating ions in the velocity orientated along magnetic field lines. We show the first experiments in which large sawtooth collapses have been controlled by this technique, and neoclassical tearing modes avoided, in high-performance reactor-relevant plasmas.

  19. The Finite Beta Effects on the Toroidal Field Ripple in a Tokamak Plasma

    NASA Astrophysics Data System (ADS)

    Bunno, M.; Nakamura, Y.; Suzuki, Y.; Shinohara, K.; Matsunaga, G.; Tani, K.

    2013-02-01

    The efficiency of energetic ion confinement is reduced in a tokamak plasma by the non-axisymmetric field, namely the ripple field. The ripple field is produced by a finite number of toroidal field coils. It is affected by the non-axisymmetric finite beta effect. The three-dimensional MHD equilibrium calculation code VMEC is used to analyze the non-axisymmetric finite beta effect in a ripple tokamak. In the VMEC code, the flux coordinates are used, so the calculation region is limited to the area of plasma. To calculate the orbit outside the plasma, we develop a field calculation code, which is based on the Biot-Savart law. The details of the method and results are described in this paper.

  20. Control of magnetohydrodynamic stability by phase space engineering of energetic ions in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Graves, J. P.; Chapman, I. T.; Coda, S.; Lennholm, M.; Albergante, M.; Jucker, M.

    2012-01-01

    Virtually collisionless magnetic mirror-trapped energetic ion populations often partially stabilize internally driven magnetohydrodynamic disturbances in the magnetosphere and in toroidal laboratory plasma devices such as the tokamak. This results in less frequent but dangerously enlarged plasma reorganization. Unique to the toroidal magnetic configuration are confined 'circulating' energetic particles that are not mirror trapped. Here we show that a newly discovered effect from hybrid kinetic-magnetohydrodynamic theory has been exploited in sophisticated phase space engineering techniques for controlling stability in the tokamak. These theoretical predictions have been confirmed, and the technique successfully applied in the Joint European Torus. Manipulation of auxiliary ion heating systems can create an asymmetry in the distribution of energetic circulating ions in the velocity orientated along magnetic field lines. We show the first experiments in which large sawtooth collapses have been controlled by this technique, and neoclassical tearing modes avoided, in high-performance reactor-relevant plasmas.

  1. Peeling-off of the external kink modes at tokamak plasma edge

    SciTech Connect

    Zheng, L. J.; Furukawa, M.

    2014-08-15

    It is pointed out that there is a current jump between the edge plasma inside the last closed flux surface and the scrape-off layer and that the current jump can lead the external kink modes to convert to the tearing modes, due to the current interchange effects [L. J. Zheng and M. Furukawa, Phys. Plasmas 17, 052508 (2010)]. The magnetic reconnection in the presence of tearing modes subsequently causes the tokamak edge plasma to be peeled off to link to the divertors. In particular, the peeling or peeling-ballooning modes can become the “peeling-off” modes in this sense. This phenomenon indicates that the tokamak edge confinement can be worse than the expectation based on the conventional kink mode picture.

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

    SciTech Connect

    Maingi, R.

    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-dimensional (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.

  3. Integrated model for transport and large scale instabilities in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Halpern, Federico David

    Improved models for neoclassical tearing modes and anomalous transport are developed and validated within integrated modeling codes to predict toroidal rotation, temperature and current density profiles in tokamak plasmas. Neoclassical tearing modes produce helical filaments of plasma, called magnetic islands, which have the effect of degrading tokamak plasma confinement or terminating the discharge. An improved code is developed in order to compute the widths of multiple simultaneous magnetic islands whose shapes are distorted by the radial variation in the magnetic perturbation [F. D. Halpern, et al., J. Plasma Physics 72 (2006) 1153]. It is found in simulations of DIII-D and JET tokamak discharges that multiple simultaneous magnetic islands produce a 10% to 20% reduction in plasma thermal confinement. If magnetic islands are allowed to grow to their full width in ITER fusion reactor simulations, fusion power production is reduced by a factor of four [F. D. Halpern, et al., Phys. Plasmas 13 (2006) 062510]. In addition to improving the prediction of neoclassical tearing modes, a new Multi-Mode transport model, MMM08, was developed to predict temperature and toroidal angular frequency profiles in simulations of tokamak discharges. The capability for predicting toroidal rotation is motivated by ITER simulation results that indicate that the effects of toroidal rotation can increase ITER fusion power production [F. D. Halpern et al., Phys. Plasmas 15 (2008), 062505]. The MMM08 model consists of an improved model for transport driven by ion drift modes [F. D. Halpern et al., Phys. Plasmas 15 (2008) 012304] together with a model for transport driven by short wavelength electron drift modes combined with models for transport driven by classical processes. The new MMM08 transport model was validated by comparing predictive simulation results with experimental data for 32 discharges in the DIII-D and JET tokamaks. It was found that the prediction of intrinsic plasma

  4. Numerical study of Alfvén eigenmodes in the Experimental Advanced Superconducting Tokamak

    SciTech Connect

    Hu, Youjun; Li, Guoqiang; Yang, Wenjun; Zhou, Deng; Ren, Qilong; Gorelenkov, N. N.; Cai, Huishan

    2014-05-15

    Alfvén eigenmodes in up-down asymmetric tokamak equilibria are studied by a new magnetohydrodynamic eigenvalue code. The code is verified with the NOVA code for the Solovév equilibrium and then is used to study Alfvén eigenmodes in a up-down asymmetric equilibrium of the Experimental Advanced Superconducting Tokamak. The frequency and mode structure of toroidicity-induced Alfvén eigenmodes are calculated. It is demonstrated numerically that up-down asymmetry induces phase variation in the eigenfunction across the major radius on the midplane.

  5. Neoclassical simulation of tokamak plasmas using the continuum gyrokinetic code TEMPEST

    NASA Astrophysics Data System (ADS)

    Xu, X. Q.

    2008-07-01

    We present gyrokinetic neoclassical simulations of tokamak plasmas with a self-consistent electric field using a fully nonlinear (full- f ) continuum code TEMPEST in a circular geometry. A set of gyrokinetic equations are discretized on a five-dimensional computational grid in phase space. The present implementation is a method of lines approach where the phase-space derivatives are discretized with finite differences, and implicit backward differencing formulas are used to advance the system in time. The fully nonlinear Boltzmann model is used for electrons. The neoclassical electric field is obtained by solving the gyrokinetic Poisson equation with self-consistent poloidal variation. With a four-dimensional (ψ,θ,γ,μ) version of the TEMPEST code, we compute the radial particle and heat fluxes, the geodesic-acoustic mode, and the development of the neoclassical electric field, which we compare with neoclassical theory using a Lorentz collision model. The present work provides a numerical scheme for self-consistently studying important dynamical aspects of neoclassical transport and electric field in toroidal magnetic fusion devices.

  6. Transport of carbon ion test particles and hydrogen recycling in the plasma of the Columbia tokamak HBT'' (High Beta Tokamak)

    SciTech Connect

    Wang, Jian-Hua.

    1990-01-01

    Carbon impurity ion transport is studied in the Columbia High Beta Tokamak (HBT), using a carbon tipped probe which is inserted into the plasma (n{sub e} {approx} 1 {minus} 5 {times} 10{sup 14} (cm{sup {minus}3}), T{sub e} {approx} 4 {minus} 10 (eV), B{sub t} {approx} 0.2 {minus} 0.4(T)). Carbon impurity light, mainly the strong lines of C{sub II}(4267A, emitted by the C{sup +} ions) and C{sub III} (4647A, emitted by the C{sup ++} ions), is formed by the ablation or sputtering of plasma ions and by the discharge of the carbon probe itself. The diffusion transport of the carbon ions is modeled by measuring the space-and-time dependent spectral light emission of the carbon ions with a collimated optical beam and photomultiplier. The point of emission can be observed in such a way as to sample regions along and transverse to the toroidal magnetic field. The carbon ion diffusion coefficients are obtained by fitting the data to a diffusion transport model. It is found that the diffusion of the carbon ions is classical'' and is controlled by the high collisionality of the HBT plasma; the diffusion is a two-dimensional problem and the expected dependence on the charge of the impurity ion is observed. The measurement of the spatial distribution of the H{sub {alpha}} emissivity was obtained by inverting the light signals from a 4-channel polychromator, the data were used to calculate the minor-radial influx, the density, and the recycling time of neutral hydrogen atoms or molecules. The calculation shows that the particle recycling time {tau}{sub p} is comparable with the plasma energy confinement time {tau}{sub E}; therefore, the recycling of the hot plasma ions with the cold neutrals from the walls is one of the main mechanisms for loss of plasma energy.

  7. Multi-channel poloidal correlation reflectometry on experimental advanced superconducting tokamak

    NASA Astrophysics Data System (ADS)

    Qu, H.; Zhang, T.; Han, X.; Xiang, H. M.; Wen, F.; Geng, K. N.; Wang, Y. M.; Kong, D. F.; Cai, J. Q.; Huang, C. B.; Gao, Y.; Gao, X.; Zhang, S.

    2016-11-01

    A new multi-channel poloidal correlation reflectometry is developed at Experimental Advanced Superconducting Tokamak. Eight dielectric resonator oscillators with frequencies of 12.5 GHz, 13.5 GHz, 14.5 GHz, 15 GHz, 15.5 GHz, 16 GHz, 17 GHz, and 18 GHz are used as sources. Signals from the sources are up-converted to V band using active quadruplers and then coupled together. The output waves are launched by one single antenna after passing through a 20 dB directional coupler which can provide the reference signal. Two poloidally separated antennae are installed to receive the reflected waves from plasma. The reference and reflected signals are down-converted by mixing with a quadrupled signal from a phase-locked source with a frequency of 14.2 GHz and the IF signals pass through the filter bank. The resulting signals from the mixers are detected by I/Q demodulators. The setup enables the measurement of density fluctuation at 8 (radial) × 2 (poloidal) spatial points. A coherent mode with an increasing velocity from 50 kHz to 100 kHz is observed by using the system. The mode is located in the steep gradient region of the pedestal.

  8. Material Surface Characteristics and Plasma Performance in the Lithium Tokamak Experiment

    NASA Astrophysics Data System (ADS)

    Lucia, Matthew James

    The performance of a tokamak plasma and the characteristics of the surrounding plasma facing component (PFC) material surfaces strongly influence each other. Despite this relationship, tokamak plasma physics has historically been studied more thoroughly than PFC surface physics. The disparity is particularly evident in lithium PFC research: decades of experiments have examined the effect of lithium PFCs on plasma performance, but the understanding of the lithium surface itself is much less complete. This latter information is critical to identifying the mechanisms by which lithium PFCs affect plasma performance. This research focused on such plasma-surface interactions in the Lithium Tokamak Experiment (LTX), a spherical torus designed to accommodate solid or liquid lithium as the primary PFC. Surface analysis was accomplished via the novel Materials Analysis and Particle Probe (MAPP) diagnostic system. In a series of experiments on LTX, the MAPP x-ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS) capabilities were used for in vacuo interrogation of PFC samples. This represented the first application of XPS and TDS for in situ surface analysis of tokamak PFCs. Surface analysis indicated that the thin (dLi ˜ 100nm) evaporative lithium PFC coatings in LTX were converted to Li2O due to oxidizing agents in both the residual vacuum and the PFC substrate. Conversion was rapid and nearly independent of PFC temperature, forming a majority Li2O surface within minutes and an entirely Li2O surface within hours. However, Li2O PFCs were still capable of retaining hydrogen and sequestering impurities until the Li2 O was further oxidized to LiOH, a process that took weeks. For hydrogen retention, Li2O PFCs retained H+ from LTX plasma discharges, but no LiH formation was observed. Instead, results implied that H+ was only weakly-bound, such that it almost completely outgassed as H 2 within minutes. For impurity sequestration, LTX plasma performance

  9. Processes with neutral hydrogen and deuterium molecules relevant to edge plasma in tokamaks

    NASA Astrophysics Data System (ADS)

    Cadez, I.; Markelj, S.; Rupnik, Z.; Pelicon, P.

    2008-07-01

    Detailed understanding and characterization of plasma-wall interaction and edge plasma in present tokamaks and future fusion reactors is becoming more and more important due to the ITER project. Involved processes determine the physical and chemical sputtering of the wall material, fuel retention in exposed material, edge plasma properties, disruption phenomena etc. Neutral hydrogen atoms and molecules are present in the edge plasma. They are continuously generated by ion recombination on the wall of the fusion reactor and on the other plasma facing components and subsequently reemitted in the plasma. Neutral molecules are especially important for plasma detachment in tokamak divertors. The interaction of excited neutral molecules with the walls and their importance for the edge plasma is still not well understood since there are not many experimental studies of relevant processes. Moreover, spectroscopic results from tokamak edge plasma are dominated by processes involving ions and electrons, so that direct evidence of the influence of neutrals is difficult to extract. Direct correlation of the observed phenomena to the processes with neutrals is mainly possible by numerical simulations. We have constructed a set-up for vibrational spectroscopy of hydrogen molecules (H_2 and D_2) that is based on the properties of the dissociative electron attachment in hydrogen in order to facilitate dedicated experimental studies of relevant processes with hydrogen molecules. For the same purpose we also developed a technique for in-situ hydrogen depth profiling on the samples exposed to the controlled hydrogen atmosphere. This is done by Ion Beam Analytical (IBA) method ERAD (Elastic Recoil Detection Analysis), utilizing 4.2 MeV probing beam of ^7Li^2+ ions. A short description of experimental techniques and results on chemical erosion of graphite layers, production of vibrationally excited hydrogen molecules on tungsten and isotope exchange on tungsten are to be presented in

  10. Theory and models of material erosion and lifetime during plasma instabilities in a tokamak environment.

    SciTech Connect

    Hassanein, A.; Konkashbaev, I.

    1999-11-08

    Surface and structural damage to plasma-facing components (PFCs) due to the frequent loss of plasma confinement remains a serious problem for the tokamak reactor concept. The deposited plasma energy causes significant surface erosion, possible structural failure, and frequent plasma contamination. Surface damage consists of vaporization, spallation, and liquid splatter of metallic materials. Structural damage includes large temperature increases in structural materials and at the interfaces between surface coatings and structural members. To evaluate the lifetimes of plasma-facing materials and nearby components and to predict the various forms of damage that they experience, comprehensive models (contained in the HEIGHTS computer simulation package) are developed, integrated self-consistently, and enhanced. Splashing mechanisms such as bubble boiling and various liquid magnetohydrodynamic instabilities and brittle destruction mechanisms of nonmelting materials are being examined. The design requirements and implications of plasma-facing and nearby components are discussed, along with recommendations to mitigate and reduce the effects of plasma instabilities on reactor components.

  11. 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.

  12. ADVANCES IN DUST DETECTION AND REMOVAL FOR TOKAMAKS

    SciTech Connect

    Campos, A.; Skinner, C.H.

    2009-01-01

    Dust diagnostics and removal techniques are vital for the safe operation of next step fusion devices such as ITER. In the tokamak environment, large particles or fi bers can fall on the electrostatic detector potentially causing a permanent short. An electrostatic dust detector developed in the laboratory is being applied to the National Spherical Torus Experiment (NSTX). We report on the development of a gas puff system that uses helium to clear such particles from the detector. Experiments at atmospheric pressure with varying nozzle designs, backing pressures, puff durations and exit fl ow orientations have given an optimal confi guration that effectively removes particles from a 25 cm² area. Similar removal effi ciencies were observed under a vacuum base pressure of 1 mTorr. Dust removal from next step tokamaks will be required to meet regulatory dust limits. A tri-polar grid of fi ne interdigitated traces has been designed that generates an electrostatic traveling wave for conveying dust particles to a “drain.” First trials with only two working electrodes have shown particle motion in optical microscope images.

  13. Scrape-off layer plasma modeling for the DIII-D tokamak

    SciTech Connect

    Porter, G.D.; Rognlien, T.D.; Allen, S.L.

    1994-09-01

    The behavior of the scrape-off layer (SOL) region in tokamaks is believed to play an important role determining the overall device performance. In addition, control of the exhaust power has become one of the most important issues in the design of future devices such as ITER and TPX. This paper presents the results of application of 2-D fluid models to the DII-D tokamak, and research into the importance of processes which are inadequately treated in the fluid models. Comparison of measured and simulated profiles of SOL plasma parameters suggest the physics model contained in the UEDGE code is sufficient to simulate plasmas which are attached to the divertor plates. Experimental evidence suggests the presence of enhanced plasma recombination and momentum removal leading to the existence of detached plasma states. UEDGE simulation of these plasmas obtains a bifurcation to a low temperature plasma at the divertor, but the plasma remains attached. Understanding the physics of this detachment is important for the design of future devices. Analytic studies of the behavior of SOL plasmas enhance our understanding beyond that achieved with fluid modeling. Analysis of the effect of drifts on sheath structure suggest these drifts may play a role in the detachment process. Analysis of the turbulent-transport equations indicate a bifurcation which is qualitatively similar to the experimentally different behavior of the L- and H-mode SOL. Electrostatic simulations of conducting wall modes suggest possible control of the SOL width by biasing.

  14. Measurements and modelling of plasma response field to RMP on the COMPASS tokamak

    NASA Astrophysics Data System (ADS)

    Markovic, T.; Liu, Y. Q.; Cahyna, P.; Pánek, R.; Peterka, M.; Aftanas, M.; Bílková, P.; Bohm, P.; Imríšek, M.; Háček, P.; Havlicek, J.; Havránek, A.; Komm, M.; Urban, J.; Weinzettl, V.; the COMPASS Team

    2016-09-01

    It has been shown on several tokamaks that application of a resonant magnetic perturbation (RMP) field to the plasma can lead to suppression or mitigation of edge-localized mode (ELM) instabilities. Due to the rotation of the plasma in the RMP field reference system, currents are induced on resonant surfaces within the plasma, consequently screening the original perturbation. In this work, the extensive set of 104 saddle loops installed on the COMPASS tokamak is utilized to measure the plasma response field for two n  =  2 RMP configurations of different poloidal mode m spectra. It is shown that spatially the response field is in opposite phase to the original perturbation, and that the poloidal profile of the measured response field does not depend on the poloidal profile of the applied RMP. Simulations of the plasma response by the linear MHD code MARS-F (Liu et al 2000 Phys. Plasmas 7 3681) reveal that both of the studied RMP configurations are well screened by the plasma. Comparison of measured plasma response field with the simulated one shows a good agreement across the majority of poloidal angles, with the exception of the midplane low-field side area, where discrepancy is seen.

  15. Neoclassical toroidal plasma viscosity with effects of finite banana width for finite aspect ratio tokamaks

    NASA Astrophysics Data System (ADS)

    Shaing, K. C.; Sabbagh, S. A.

    2016-07-01

    Theory for neoclassical toroidal plasma viscosity has been developed to model transport phenomena, especially, toroidal plasma rotation for tokamaks with broken symmetry. Theoretical predictions are in agreement with the results of the numerical codes in the large aspect ratio limit. The theory has since been extended to include effects of finite aspect ratio and finite plasma β. Here, β is the ratio of the plasma thermal pressure to the magnetic field pressure. However, there are cases where the radial wavelength of the self-consistent perturbed magnetic field strength B on the perturbed magnetic surface is comparable to the width of the trapped particles, i.e., bananas. To accommodate those cases, the theory for neoclassical toroidal plasma viscosity is further extended here to include the effects of the finite banana width. The extended theory is developed using the orbit averaged drift kinetic equation in the low collisionality regimes. The results of the theory can now be used to model plasma transport, including toroidal plasma rotation, in real finite aspect ratio, and finite plasma β tokamaks with the radial wavelength of the perturbed symmetry breaking magnetic field strength comparable to or longer than the banana width.

  16. Optimization of out-vessel magnetic diagnostics for plasma boundary reconstruction in tokamaks

    NASA Astrophysics Data System (ADS)

    Romero, J. A.; Svensson, J.

    2013-03-01

    To improve the low-frequency spectrum of magnetic field measurements of future tokamak reactors such as ITER, several steady-state magnetic sensor technologies have been considered. For all the studied technologies it is always advantageous to place the sensors outside the vacuum vessel and as far away from the reactor core to minimize radiation damage and temperature effects, but not so far as to compromise the accuracy of the equilibrium reconstruction. We have studied to what extent increasing the distance between out-vessel sensors and plasma can be compensated for sensor accuracy and/or density before the limit imposed by the degeneracy of the problem is reached. The study is particularized for the Swiss TCV tokamak, due to the quality of its magnetic data and its ability to operate with a wide range of plasma shapes and divertor configurations. We have scanned the plasma boundary reconstruction error as a function of out-vessel sensor density, accuracy and distance to the plasma. The study is performed for both the transient and steady-state phases of the tokamak discharge. We find that, in general, there is a broad region in the parameter space where sensor accuracy, density and proximity to the plasma can be traded for one another to obtain a desired level of accuracy in the reconstructed boundary, up to some limit. Extrapolation of the results to a tokamak reactor suggests that a hybrid configuration with sensors inside and outside the vacuum vessel could be used to obtain a good boundary reconstruction during both the transient and the flat-top of the discharges, if out-vessel magnetic sensors of sufficient density and accuracy can be placed sufficiently far outside the vessel to minimize radiation damage.

  17. Neoclassical ion thermal conductivity modified by finite banana effects in a tokamak plasma

    SciTech Connect

    Chang, C.S.

    1997-06-01

    A finite-banana-width correction to the neoclassical ion thermal conductivity is obtained in a tokamak plasma under the conventional assumption that the particle flow parallel to magnetic-field lines dominates the trapped particle{close_quote}s orbital dynamics. It is found that the finite-banana-width effect makes ion thermal conductivity itself be a function of radial plasma density gradient and magnetic shear. Negative radial gradients in plasma density and/or safety factor can reduce the neoclassical ion thermal conductivity when the banana width is a significant fraction of the gradient scale length. {copyright} {ital 1997 American Institute of Physics.}

  18. Thermal ablation of plasma-facing surfaces in tokamak disruptions: Sensitivity to particle kinetic energy

    SciTech Connect

    Ehst, D.A.; Hassanein, A.

    1996-02-01

    Ablation damage to solid targets with high heat flux impulses is generally greater high-energy electron beam heat sources compared to low-energy plasma guns. This sensitivity to incoming particle kinetic energy is explored with computer modelling; a fast-running routine (DESIRE) is developed for initial scoping analysis and is found to be in reasonable agreement with several experiments on graphite and tungsten targets. If tokamak disruptions are characterized by particle energies less than {approximately}1 keV, then we expect plasma guns are a better analogue than electron beams for simulating disruption behavior and testing candidate plasma-facing materials.

  19. Variation in Lyman-{alpha} fine structure components for Cl XVII during a tokamak plasma shot

    SciTech Connect

    Ashbourn, J.M.A.; McGinnity, P.; Peacock, N.J.

    2005-01-01

    In this Brief Report we study the measured and modeled Lyman-{alpha} intensity ratios for hydrogenlike Cl XVII in a deuterium base plasma in the Joint European Torus tokamak and examine the agreement between experiment and theory for a particular plasma shot. A collisional-radiative model is used to calculate the values of the intensity ratios using measured plasma parameters for comparison with line-of-sight values. When variations in the electron parameters during the discharge are taken into account, the variations in the modeled values are seen to follow the experimental data. The difference between the values of observed and modeled intensity ratios is discussed.

  20. Continuum modes in rotating plasmas: General equations and continuous spectra for large aspect ratio tokamaks

    SciTech Connect

    Lakhin, V. P.; Ilgisonis, V. I.

    2011-09-15

    A theory for localized low-frequency ideal magnetohydrodynamical (MHD) modes in axisymmetric toroidal systems is generalized to take into account both toroidal and poloidal equilibrium plasma flows. The general set of equations describing the coupling of shear Alfven and slow (sound) modes and defining the continuous spectrum of rotating plasmas in axisymmetric toroidal systems is derived. The equations are applied to study the continuous spectra in large aspect ratio tokamaks. The unstable continuous modes in the case of predominantly poloidal plasma rotation with the angular velocity exceeding the sound frequency are found. Their stabilization by the shear Alfven coupling effect is studied.

  1. Nonlinear three-dimensional MHD simulations of tearing modes in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Lütjens, H.; Luciani, J. F.; Garbet, X.

    2001-12-01

    The comprehension of the dynamics of classical and neoclassical tearing modes is a key issue in high-performance tokamak plasmas. Avoiding these instabilities requires a good knowledge of all the physical mechanisms involved in their linear and/or nonlinear onset. Our tridimensional time evolution code XTOR, which solves the full magnetohydrodynamic (MHD) equations including thermal transport, is used to tackle this difficult problem. In this paper, to show the state of art in full-scale nonlinear MHD simulations of tokamak plasmas, we investigate the effect of plasma curvature on the tearing mode dynamics. For a realistic picture of this dynamics, heat diffusion is required in the linear regimes as well, as in the nonlinear regimes. We present a new dispersion relation including perpendicular and parallel transport, and show that it matches the linear and nonlinear regimes. This leads to a new tearing mode island evolution equation including curvature effects, valid for every island size in tokamak plasmas. This equation predicts a nonlinearly unstable regime for tearing instabilities, i.e. a regime which is linearly stable, but where the tearing mode can be destabilized nonlinearly by a finite-size seed island. These theoretical predictions are in good agreement with XTOR simulations. In particular, the nonlinear instability due to curvature effects is reproduced. Our results have an important impact on the onset mechanism of neoclassical tearing modes. They indeed predict that curvature effects lead to a resistive MHD threshold.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  3. Plasma Processing of Advanced Materials

    SciTech Connect

    Heberlein, Joachim, V.R.; Pfender, Emil; Kortshagen, Uwe

    2005-02-28

    Plasma Processing of Advanced Materials The project had the overall objective of improving our understanding of the influences of process parameters on the properties of advanced superhard materials. The focus was on high rate deposition processes using thermal plasmas and atmospheric pressure glow discharges, and the emphasis on superhard materials was chosen because of the potential impact of such materials on industrial energy use and on the environment. In addition, the development of suitable diagnostic techniques was pursued. The project was divided into four tasks: (1) Deposition of superhard boron containing films using a supersonic plasma jet reactor (SPJR), and the characterization of the deposition process. (2) Deposition of superhard nanocomposite films in the silicon-nitrogen-carbon system using the triple torch plasma reactor (TTPR), and the characterization of the deposition process. (3) Deposition of films consisting of carbon nanotubes using an atmospheric pressure glow discharge reactor. (4) Adapting the Thomson scattering method for characterization of atmospheric pressure non-uniform plasmas with steep spatial gradients and temporal fluctuations. This report summarizes the results.

  4. Tokamak equilibria with toroidal-current reversal in the plasma core consistent with experimental data.

    PubMed

    Rodrigues, Paulo; Bizarro, João P S

    2007-09-21

    For the first time, tokamak equilibria with negative toroidal current flowing in the plasma core are computed consistently with available measurements from typical current-hole discharges. The equilibrium reconstruction, which leads to non-nested configurations where a system of axisymmetric magnetic islands unfolds, yields an overall good agreement between the computed and experimental plasma-pressure profiles, together with an excellent fit to motional-Stark-effect data. Therefore, considering the accuracy limits of present-day experimental results, care must be exercised when ruling out the existence of tokamak equilibria with central toroidal-current reversal, particularly if relying on reconstruction tools that cannot cope with non-nested configurations. PMID:17930511

  5. Plasma Core Electron Density and Temperature Measurements Using CVI Line Emissions in TCABR Tokamak

    NASA Astrophysics Data System (ADS)

    do Nascimento, F.; Machida, M.; Severo, J. H. F.; Sanada, E.; Ronchi, G.

    2015-08-01

    In this work, we present results of electron temperature ( T e ) and density ( n e ) measurements obtained in Tokamak Chauffage Alfvén Brésilien (TCABR) tokamak using visible spectroscopy from CVI line emissions which occurs mainly near the center of the plasma column. The presented method is based on a well-known relationship between the particle flux ( Γ ion) and the photon flux ( ø ion) emitted by an ion species combined with ionizations per photon atomic data provided by the atomic data and analysis structure (ADAS) database. In the experiment, we measured the photon fluxes of three different CVI spectral line emissions, 4685.2, 5290.5, and 6200.6 Å (one line per shot). Using this method it was possible to find out the temporal evolution of T e and n e in the plasma. The results achieved are in good agreement with T e and n e measurements made using other diagnostic tools.

  6. GEM detector development for tokamak plasma radiation diagnostics: SXR poloidal tomography

    NASA Astrophysics Data System (ADS)

    Chernyshova, Maryna; Malinowski, Karol; Ziółkowski, Adam; Kowalska-Strzeciwilk, Ewa; Czarski, Tomasz; Poźniak, Krzysztof T.; Kasprowicz, Grzegorz; Zabołotny, Wojciech; Wojeński, Andrzej; Kolasiński, Piotr; Krawczyk, Rafał D.

    2015-09-01

    An increased attention to tungsten material is related to a fact that it became a main candidate for the plasma facing material in ITER and future fusion reactor. The proposed work refers to the studies of W influence on the plasma performances by developing new detectors based on Gas Electron Multiplier GEM) technology for tomographic studies of tungsten transport in ITER-oriented tokamaks, e.g. WEST project. It presents current stage of design and developing of cylindrically bent SXR GEM detector construction for horizontal port implementation. Concept to overcome an influence of constraints on vertical port has been also presented. It is expected that the detecting unit under development, when implemented, will add to the safe operation of tokamak bringing creation of sustainable nuclear fusion reactors a step closer.

  7. Soft x-ray imaging system for measurement of noncircular tokamak plasmas

    SciTech Connect

    Fonck, R.J.; Reusch, M.; Jaehnig, K.P.; Hulse, R.; Roney, P.

    1986-08-01

    A soft x-ray camera and image processing system has been constructed to provide measurements of the internal shape of high temperature tokamak plasmas. The camera consists of a metallic-foil-filtered pinhole aperture and a microchannel plate image intensifier/convertor which produces a visible image for detection by a CCD TV camera. A wide-angle tangential view of the toroidal plasma allows a single compact camera to view the entire plasma cross section. With Be filters 12 to 50 ..mu..m thick, the signal from the microchannel plate is produced mostly by nickel L-line emissions which orignate in the hot plasma core. The measured toroidal image is numerically inverted to produce a cross-sectional soft x-ray image of the plasma. Since the internal magnetic flux surfaces are usually isothermal and the nickel emissivity depends strongly on the local electron temperature, the x-ray emission contours reflect the shape of the magnetic surfaces in the plasma interior. Initial results from the PBX tokamak experiment show clear differences in internal plasma shapes for circular and bean-shaped discharges.

  8. Importance of Plasma Response to Non-axisymmetric Perturbations in Tokamaks

    SciTech Connect

    Jong-kyu Park, Allen H. Boozer, Jonathan E. Menard, Andrea M. Garofalo, Michael J. Schaffer, Richard J. Hawryluk, Stanley M. Kaye, Stefan P. Gerhardt, Steve A. Sabbagh, and the NSTX Team

    2009-04-22

    Tokamaks are sensitive to deviations from axisymmetry as small as δB=B0 ~ 10-4. These non-axisymmetric perturbations greatly modify plasma confinement and performance by either destroying magnetic surfaces with subsequent locking or deforming magnetic surfaces with associated non-ambipolar transport. The Ideal Perturbed Equilibrium Code (IPEC) calculates ideal perturbed equilibria and provides important basis for understanding the sensitivity of tokamak plasmas to perturbations. IPEC calculations indicate that the ideal plasma response, or equiva- lently the effect by ideally perturbed plasma currents, is essential to explain locking experiments on National Spherical Torus eXperiment (NSTX) and DIII-D. The ideal plasma response is also important for Neoclassical Toroidal Viscosity (NTV) in non-ambipolar transport. The consistency between NTV theory and magnetic braking experiments on NSTX and DIII-D can be improved when the variation in the field strength in IPEC is coupled with generalized NTV theory. These plasma response effects will be compared with the previous vacuum superpositions to illustrate the importance. However, plasma response based on ideal perturbed equilibria is still not suffciently accurate to predict the details of NTV transport, and can be inconsistent when currents associated with a toroidal torque become comparable to ideal perturbed currents.

  9. Resistive MHD studies of high-. beta. -tokamak plasmas

    SciTech Connect

    Lynch, V.E.; Carreras, B.A.; Hicks, H.R.; Holmes, J.A.; Garcia, L.

    1981-01-01

    Numerical calculations have been performed to study the MHD activity in high-..beta.. tokamaks such as ISX-B. These initial value calculations built on earlier low ..beta.. techniques, but the ..beta.. effects create several new numerical issues. These issues are discussed and resolved. In addition to time-stepping modules, our system of computer codes includes equilibrium solvers (used to provide an initial condition) and output modules, such as a magnetic field line follower and an X-ray diagnostic code. The transition from current driven modes at low ..beta.. to predominantly pressure driven modes at high ..beta.. is described. The nonlinear studies yield X-ray emissivity plots which are compared with experiment.

  10. Sub-Alfvenic Reduced Equations for Tokamak Plasmas

    NASA Astrophysics Data System (ADS)

    Sengupta, W.; Hassam, A. B.; Antonsen, T. M.

    2015-11-01

    We present a system of reduced resistive MHD equations which are sub-Alfvenic with respect to ideal ballooning in large aspect ratio tokamak geometry. The low beta system allows dynamic evolution of full profiles. The system has the advantage that it is 2-dimensional in the transverse to º, space variables. This allows significant analytical tractability as well as ease in numerical implementation. The linearized equations are shown to reproduce Mercier modes, resistive ballooning modes, tearing modes, sound waves, GAMs, the Stringer spinup, and Rosenbluth-Hinton zonal flows. The methodology developed allows extension to drift modes as well as to a hybrid system of moment and electromagnetic sub-gyro-drift-kinetic equations. Analytical and numerical benchmarks will be presented. We show that the system, which requires Laplace equation inversion to solve for electromagnetic potentials, is implementable numerically. Work supported by DOE.

  11. Two-component ion distributions in tokamak hot ion plasmas

    NASA Astrophysics Data System (ADS)

    Ware, A. A.

    1984-05-01

    The two-component ion distribution observed with active charge-exchange measurements on the tokamak PDX are explained using the Fokker-Planck drift-kinetic equation and assuming that ion self-collisions are dominant for energy scattering. The energetic tail of the distribution, which is diffusing outwards in radius and down in energy, must retain an approximately constant effective temperature TH≡(-∂ ln f i/m∂ɛ)-1. The discontinuity in the slope of ln f i is shown to be the boundary between the inward and outward diffusion parts of f i and is a form of contact discontinuity. Energy-scattering collisions with electrons or circulating beam ions, when important, modify the constancy of TH.

  12. Two-component ion distributions in tokamak hot ion plasmas

    SciTech Connect

    Ware, A.A.

    1984-05-01

    The two-component ion distribution observed with active charge-exchange measurements on the tokamak PDX are explained using the Fokker--Planck drift-kinetic equation and assuming that ion self-collisions are dominant for energy scattering. The energetic tail of the distribution, which is diffusing outwards in radius and down in energy, must retain an approximately constant effective temperature T/sub H/equivalent(-partial ln f /sub i//mpartialepsilon)/sup -1/. The discontinuity in the slope of ln f /sub i/ is shown to be the boundary between the inward and outward diffusion parts of f /sub i/ and is a form of contact discontinuity. Energy-scattering collisions with electrons or circulating beam ions, when important, modify the constancy of T/sub H/.

  13. Transport properties of interacting magnetic islands in tokamak plasmas

    SciTech Connect

    Gianakon, T.A.; Callen, J.D.; Hegna, C.C.

    1993-10-01

    This paper explores the equilibrium and transient transport properties of a mixed magnetic topology model for tokamak equilibria. The magnetic topology is composed of a discrete set of mostly non-overlapping magnetic islands centered on the low-order rational surfaces. Transport across the island regions is fast due to parallel transport along the stochastic magnetic field lines about the separatrix of each island. Transport between island regions is assumed to be slow due to a low residual cross-field transport. In equilibrium, such a model leads to: a nonlinear dependence of the heat flux on the pressure gradient; a power balance diffusion coefficient which increases from core to edge; and profile resiliency. Transiently, such a model also exhibits a heat pulse diffusion coefficient larger than the power balance diffusion coefficient.

  14. Designing a Sine-Coil for Measurement of Plasma Displacements in IR-T1 Tokamak

    SciTech Connect

    Khorshid, Pejman; Razavi, M.; Molaii, M.; Ghoranneviss, M.; TalebiTaher, A.; Arvin, R.; Mohammadi, S.; NikMohammadi, A.

    2008-04-07

    A method for the measurement of the plasma position in the IR-T1 tokamak in toroidal coordinates is developed. A sine-coil, which is a Rogowski coil with a variable wiring density is designed and fabricated for this purpose. An analytic solution of the Biot-Savart law, which is used to calculate magnetic fields created by toroidal plasma current, is presented. Results of calculations are compared with the experimental data obtained in no-plasma shots with a toroidal current-carrying coil positioned inside the vessel to simulate the plasma movements. The results are shown a good linear behavior of plasma position measurements. The error is less than 2.5% and it is compared with other methods of measurements of the plasma position. This method will be used in the feedback position control system and tests of feedback controller parameters are ongoing.

  15. Plasma surface and wall eddy currents and their connection to Halo currents during disruptions in tokamaks

    NASA Astrophysics Data System (ADS)

    Yanovskiy, Vadim; Paccagnella, Roberto

    2014-10-01

    The behaviour of plasma surface currents and resistive wall eddy currents is analysed analytically within a cylindrical model for pressureless ideal plasma with flat and parabolic equilibrium current profiles. This mimics possible conditions in tokamak plasmas during disruptions between the thermal and the current quench phases. Earlier studies predict that plasma surface currents have to be taken into account for explanation of the Halo currents intensity and distribution. Our results show that this is true only in a very narrow window of edge safety factor qa and that in a wide region of qa the wall eddy currents are comparable or much larger than the plasma skin currents. The study reveals ranges of plasma and wall parameters for which the surface currents could play a role in Halo currents dynamics. Some comparison of the results with previous works on this topic is also presented.

  16. Identification of plasma boundary and position for T de V Tokamak

    NASA Astrophysics Data System (ADS)

    Wang, Zhongtian; Clair, G. Le; Li, Fangzhu; Zhang, Jinhua; Mao, Guoping

    2000-10-01

    Using virtual-casing principle, plasma boundary, plasma current center, and x-point are identified for tokamak de varennes. Adaptive parameters in a polynomial, which is a solution of the Glad-Shafranov, are determined by least-square fit of the poloidal fields. The measurement of the magnetic field is performed using pick-up coils. Plasma current is initially regarded as one filament, then replaced by virtual-case currents, which produce negative confinement magnetic field inside plasma and self-field generated by plasma current outside the plasma boundary. Though reiterative method is used, The convergence is fast enough to get picture between the shots. The configuration obtained is in good agreement with the TV image taken by camera with a toroidal view.

  17. Identification of Plasma Boundary and Position for TdeV Tokamak

    NASA Astrophysics Data System (ADS)

    Wang, Zhongtian; Clair, G. Le; Li, Fangzhu; Zhang, Jinhua; Mao, Guoping

    2000-10-01

    Using virtual-casing principle, plasma boundary, plasma current center, and x-point are identified for tokamak de varennes. Adaptive parameters in a polynomial, which is a solution of the Glad-Shafranov, are determined by least-square fit of the poloidal fields. The measurement of the magnetic field is performed using pick-up coils. Plasma current is initially regarded as one filament, then replaced by virtual-case currents, which produce negative confinement magnetic field inside plasma and self-field generated by plasma current outside the plasma boundary. Though reiterative method is used, The convergence is fast enough to get picture between the shots. The configuration obtained is in good agreement with the TV image taken by camera with a toroidal view.

  18. The construction of an electrode biasing system for driving plasma rotation in J-TEXT tokamak

    NASA Astrophysics Data System (ADS)

    Zhu, T. Z.; Chen, Z. P.; Sun, Yue; Nan, J. Y.; Liu, H.; Zhuang, G.; Wang, Z. J.

    2014-05-01

    A newly designed electrode biasing system has been constructed for driving plasma rotation in J-TEXT tokamak. To reduce the influence to the plasma, the system contains a pneumatic driving system so that it can reciprocate in a single discharge, with a stroke of about 5 cm in 100 ms. The power supply of the system can provide stable and adjustable dc voltage in the range of 0-700 V, with adjustable duration of 10-200 ms; its instantaneous power output can reach up to more than 200 kW. In addition, the power supply can also provide a multi-cycle voltage waveform, with adjustable pulse width and voltage amplitude. When applying a positive bias to the plasma, both an improvement of plasma confinement and the speed-up of plasma-edge toroidal rotation in the same direction of plasma current are observed in the experiments.

  19. Ideal plasma response to vacuum magnetic fields with resonant magnetic perturbations in non-axisymmetric tokamaks

    SciTech Connect

    Kim, Kimin; Ahn, J. -W.; Scotti, F.; Park, J. -K.; Menard, J. E.

    2015-09-03

    Ideal plasma shielding and amplification of resonant magnetic perturbations in non-axisymmetric tokamak is presented by field line tracing simulation with full ideal plasma response, compared to measurements of divertor lobe structures. Magnetic field line tracing simulations in NSTX with toroidal non-axisymmetry indicate the ideal plasma response can significantly shield/amplify and phase shift the vacuum resonant magnetic perturbations. Ideal plasma shielding for n = 3 mode is found to prevent magnetic islands from opening as consistently shown in the field line connection length profile and magnetic footprints on the divertor target. It is also found that the ideal plasma shielding modifies the degree of stochasticity but does not change the overall helical lobe structures of the vacuum field for n = 3. Furthermore, amplification of vacuum fields by the ideal plasma response is predicted for low toroidal mode n = 1, better reproducing measurements of strong striation of the field lines on the divertor plate in NSTX.

  20. Evaluation of magnetic fields due to the ferromagnetic vacuum vessel and their influence on plasma discharge in tokamak devices

    NASA Astrophysics Data System (ADS)

    Nakayama, T.; Abe, M.; Tadokoro, T.; Otsuka, M.

    We studied characteristics of the magnetic fields due to a ferromagnetic vacuum vessel (F-VV) experimentally and computationally to clarify whether plasma discharge is possible with the F-VV in tokamak devices. We made three kinds of evaluations using the Hitachi tokamak HT-2. One was a discharge test with error field coil. The second was a numerical analysis of the magnetic field induced by a ferritic first wall. The third was a discharge test with the ferritic first wall. Consequently, we confirmed that a normal plasma discharge could be obtained with a ferritic first wall in the HT-2. The strength of the localized magnetic field induced by the F-VV in the plasma region was smaller in tokamak devices with the size of the JFT-2M and ITER than in the HT-2. Therefore, the F-VV should be applicable to tokamak devices.

  1. Magnetic Reconnection Triggering Magnetohydrodynamic Instabilities during a Sawtooth Crash in a Tokamak Plasma

    SciTech Connect

    Chapman, I. T.; Scannell, R.; Hastie, R. J.; Naylor, G.; Zocco, A.

    2010-12-17

    Thomson scattering measurements with subcentimeter spatial resolution have been made during a sawtooth crash in a Mega Ampere Spherical Tokamak fusion plasma. The unparalleled resolution of the temperature profile has shed new light on the mechanisms that underlie the sawtooth. As magnetic reconnection occurs, the temperature gradient at the island boundary increases. The increased local temperature gradient is sufficient to make the helical core unstable to ideal magnetohydrodynamic instabilities, thought to be responsible for the rapidity of the collapse.

  2. Magnetic reconnection triggering magnetohydrodynamic instabilities during a sawtooth crash in a Tokamak plasma.

    PubMed

    Chapman, I T; Scannell, R; Cooper, W A; Graves, J P; Hastie, R J; Naylor, G; Zocco, A

    2010-12-17

    Thomson scattering measurements with subcentimeter spatial resolution have been made during a sawtooth crash in a Mega Ampere Spherical Tokamak fusion plasma. The unparalleled resolution of the temperature profile has shed new light on the mechanisms that underlie the sawtooth. As magnetic reconnection occurs, the temperature gradient at the island boundary increases. The increased local temperature gradient is sufficient to make the helical core unstable to ideal magnetohydrodynamic instabilities, thought to be responsible for the rapidity of the collapse.

  3. Residual parallel Reynolds stress due to turbulence intensity gradient in tokamak plasmas

    SciTech Connect

    Guercan, Oe. D.; Hennequin, P.; Diamond, P. H.; McDevitt, C. J.; Garbet, X.; Bourdelle, C.

    2010-11-15

    A novel mechanism for driving residual stress in tokamak plasmas based on k{sub ||} symmetry breaking by the turbulence intensity gradient is proposed. The physics of this mechanism is explained and its connection to the wave kinetic equation and the wave-momentum flux is described. Applications to the H-mode pedestal in particular to internal transport barriers, are discussed. Also, the effect of heat transport on the momentum flux is discussed.

  4. Spontaneous L-mode plasma rotation scaling in the TCV tokamak

    SciTech Connect

    Duval, B. P.; Bortolon, A.; Karpushov, A.; Pitts, R. A.; Pochelon, A.; Sauter, O.; Scarabosio, A.; Turri, G.

    2008-05-15

    Predicting intrinsic plasma rotation and its shear, which often help stabilize plasma instabilities affecting plasma performance, is important for prospective fusion grade devices. Although rotation in ITER-like scenarios has been extrapolated from measured experimental plasma rotation data, little is understood about the underlying mechanisms governing either the generation or dissipation of momentum in a tokamak plasma. This paper reports on studies of intrinsic toroidal and poloidal plasma rotation from charge exchange spectroscopy using a low power diagnostic beam on the TCV tokamak [Tonetti et al., in Proceedings of the Symposium on Fusion Technology (1991), p. 587] that drives negligible toroidal velocity. In TCV, plasma behavior can be separated by the core and edge regions. In limited configurations, the core rotates in the counter-current direction and can reverse to the co-current direction with a <10% increase in the plasma density. This is different for diverted configurations where the core rotates in the co-current direction reversing to the counter-current direction at higher plasma densities. For all these situations, core toroidal momentum is strongly transported by plasma sawteeth oscillations. In contrast, the toroidal edge rotation is close to stationary for limited discharges but evolves with plasma density for diverted configurations. Theoretical models that predict a change in momentum transport from turbulence have previously been suggested to provide a mechanism that might explain these phenomena. In this paper, mode activity that changes at the toroidal velocity reversal, is identified as a new possible candidate. In the absence of an available model that can explain these basic phenomena, this paper presents observations and, where possible, scaling of the rotation profiles with some of the major plasma parameters such as current, density and shape to guide the development of a physics model for use in improving the extrapolation of the

  5. Plasma start-up results with electron cyclotron assisted breakdown on Frascati Tokamak Upgrade

    NASA Astrophysics Data System (ADS)

    Granucci, G.; Ramponi, G.; Calabrò, G.; Crisanti, F.; Nowak, S.; Ramogida, G.; Tudisco, O.; Bin, W.; Botrugno, A.; Buratti, P.; D'Arcangelo, O.; Frigione, D.; Pucella, G.; Romano, A.; FTU Team

    2011-07-01

    Several experiments aimed at optimizing plasma pre-ionization using electron cyclotron (EC) waves have been carried out on many tokamaks in recent years as the basis of a multi-machine comparison study made to define the best operation scenarios for ITER, where the plasma breakdown will have to be achieved with a toroidal electric field of only 0.3 V m-1. The FTU (Frascati Tokamak Upgrade, R = 0.935 m, a = 0.3 m) contribution to this study is the main subject of this work. A reduction in electric field, as can be obtained with pre-ionization by ECH, can lower the transformer flux consumption in the start-up phase leading to a longer plasma current flat top. This point is of particular interest in the conceptual design of the steady-state scenario of the proposed FAST tokamak and has also been addressed. In the FTU experiment the scan in pre-filling pressure has evidenced the capability of EC power to increase, by a factor 4, the range of working pressure useful for plasma start-up. Varying the breakdown a minimum electric field of 0.41 V m-1 has been found with 0.8 MW of EC in perpendicular injection. A scan in magnetic field has evidenced that plasma start-up is likely insensitive to alignment between EC resonance and null position. A total transformer flux saving of 22% has been found acting on plasma resistivity (by increasing electron temperature) and on the plasma starting point (for an internal inductance reduction).

  6. Plasma-material Interactions in Current Tokamaks and their Implications for Next-step Fusion Reactors

    SciTech Connect

    Federici, G.; Skinner, C.H.; Brooks, J.N.; Coad, J.P.; Grisolia, C.

    2001-01-10

    The major increase in discharge duration and plasma energy in a next-step DT [deuterium-tritium] fusion reactor will give rise to important plasma-material effects that will critically influence its operation, safety, and performance. Erosion will increase to a scale of several centimeters from being barely measurable at a micron scale in today's tokamaks. Tritium co-deposited with carbon will strongly affect the operation of machines with carbon plasma-facing components. Controlling plasma wall interactions is critical to achieving high performance in present-day tokamaks and this is likely to continue to be the case in the approach to practical fusion reactors. Recognition of the important consequences of these phenomena has stimulated an internationally coordinated effort in the field of plasma-surface interactions supporting the Engineering Design Activities of the International Thermonuclear Experimental Reactor (ITER) project and significant progress has been made in better under standing these issues. This paper reviews the underlying physical processes and the existing experimental database of plasma-material interactions both in tokamaks and laboratory simulation facilities for conditions of direct relevance to next-step fusion reactors. Two main topical groups of interactions are considered: (i) erosion/redeposition from plasma sputtering and disruptions, including dust and flake generation, (ii) tritium retention and removal. The use of modeling tools to interpret the experimental results and make projections for conditions expected in future devices is explained. Outstanding technical issues and specific recommendations on potential R and D [Research and Development] avenues for their resolution are presented.

  7. Study of Plasma Interaction with Titanium Coated Ferritic Steel in IR-T1 Tokamak

    SciTech Connect

    Ghoranneviss, M.; Talebitaher, A.; Arvin, R.; Mohammadi, S.; Nikmohamadi, A.; Milani, M.; Salem, M. K.; Sari, A. H.; Yousefi, M. R.; Shokouhi, A.; Khorshid, P.; Saboohi, S.

    2008-04-07

    Studies of plasma interaction with titanium coated ferritic steel is performed on IR-T1 tokamak. Titanium coating is one of the candidates for the plasma facing materials in a tokomak. Titaniumization is carried out by a sputtering method. Some of the samples were baked (3 hours at 460 deg. C) before sputtering. Atomic Force Microscopy (AFM) analyses before and after discharge in r/a = l .04 carried out. The samples (with distinctive titanium layers) were placed at different depths inside the vacuum vessel of the IR-T1 tokamak in the SOL region. A comparison of the titanium coated steel with bare ferritic steel exposed to plasma tokamak and glow discharges is made in this research. Depth of impurity penetration and retention, and the surface roughness are measured by using surface analysis methods. Rutherford backscattering method is used to measure the content of nitrogen, oxygen and titanium, before and after discharges. The result is shown a change in roughness with respect to position of samples.

  8. Study of Plasma Interaction with Titanium Coated Ferritic Steel in IR-T1 Tokamak

    NASA Astrophysics Data System (ADS)

    Ghoranneviss, M.; Khorshid, P.; Saboohi, S.; Talebitaher, A.; Arvin, R.; Mohammadi, S.; Nikmohamadi, A.; Milani, M.; Salem, M. K.; Sari, A. H.; Yousefi, M. R.; Shokouhi, A.

    2008-04-01

    Studies of plasma interaction with titanium coated ferritic steel is performed on IR-T1 tokamak. Titanium coating is one of the candidates for the plasma facing materials in a tokomak. Titaniumization is carried out by a sputtering method. Some of the samples were baked (3 hours at 460 °C) before sputtering. Atomic Force Microscopy (AFM) analyses before and after discharge in r/a = l .04 carried out. The samples (with distinctive titanium layers) were placed at different depths inside the vacuum vessel of the IR-T1 tokamak in the SOL region. A comparison of the titanium coated steel with bare ferritic steel exposed to plasma tokamak and glow discharges is made in this research. Depth of impurity penetration and retention, and the surface roughness are measured by using surface analysis methods. Rutherford backscattering method is used to measure the content of nitrogen, oxygen and titanium, before and after discharges. The result is shown a change in roughness with respect to position of samples.

  9. Particle and momentum confinement in tokamak plasmas with unbalanced neutral beam injection and strong rotation

    SciTech Connect

    Malik, M.A.

    1988-01-01

    There is a self-consistent theory of the effects of neutral beam injection on impurity transport in tokamak plasmas. The theory predicts that co-injection drives impurities outward and that counter-injection enhances the normally inward flow of impurities. The theory was applied to carry out a detailed analysis of the large experimental database from the PLT and the ISX-B tokamaks. The theory was found to generally model the experimental data quite well. It is, therefore, concluded that neutral beam co-injection can drive impurities outward to achieve clean central plasmas and a cool radiating edge. Theoretical predictions for future thermonuclear reactors such as INTOR, TIBER II, and ITER indicated that neutral beam driven flow reversal might be an effective impurity control method if the rate of beam momentum deposited per plasma ion is adequate. The external momentum drag, which is a pivotal concept in impurity flow reversal theory, is correctly predicted by the gyroviscous theory of momentum confinement. The theory was applied to analyze experimental data from the PLT and the PDX tokamaks with exact experimental conditions. The theory was found to be in excellent agreement with experiment over a wide range of parameters. It is, therefore, possible to formulate the impurity transport theory from first principles, without resort to empiricism.

  10. Parametric analysis of the thermal effects on the divertor in tokamaks during plasma disruptions

    SciTech Connect

    Bruhn, M.L.

    1988-04-01

    Plasma disruptions are an ever present danger to the plasma-facing components in today's tokamak fusion reactors. This threat results from our lack of understanding and limited ability to control this complex phenomenon. In particular, severe energy deposition occurs on the divertor component of the double-null configured tokamak reactor during such disruptions. A hybrid computational model developed to estimate and graphically illustrate global thermal effects of disruptions on the divertor plates is described in detail. The quasi-two-dimensional computer code, TADDPAK (Thermal Analysis Divertor during Disruptions PAcKage), is used to conduct parametric analysis for the TIBER II Tokamak Engineering Test Reactor Design. The dependence of these thermal effects on divertor material choice, disruption pulse length, disruption pulse shape, and the characteristic thickness of the plasma scrape-off layer is investigated for this reactor design. Results and conclusions from this analysis are presented. Improvements to this model and issues that require further investigation are discussed. Cursory analysis for ITER (International Thermonuclear Experimental Reactor) is also presented in the appendix. 75 refs., 49 figs., 10 tabs.

  11. Plasma-materials interactions during rf experiments in tokamaks

    SciTech Connect

    Cohen, S.A.; Bernabei, S.; Budny, R.; Chu, T.K.; Colestock, P.; Hinnov, E.; Hooke, W.; Hosea, J.; Hwang, D.; Jobes, F.

    1984-09-01

    Plasma-materials interactions studied in recent ICRF heating and lower hybrid current drive experiments are reviewed. The microscopic processes responsible for impurity generation are discussed. In ICRF experiments, improvements in machine operation and in antenna and feedthrough design have allowed efficient plasma heating at RF powers up to 3 MW. No significant loss of energy from the plasma core due to impurity radiation occurs. Lower hybrid current drive results in the generation and maintenance of hundreds of kiloamperes of plasma current carried by suprathermal electrons. The loss of these electrons and their role in impurity generation are assessed. Methods to avoid this problem are evaluated.

  12. Progress toward long-pulse high-performance Advanced Tokamak discharges on the DIII-D tokamak

    NASA Astrophysics Data System (ADS)

    Wade, M. R.; Luce, T. C.; Politzer, P. A.; Ferron, J. R.; Allen, S. L.; Austin, M. E.; Baker, D. R.; Bray, B.; Brennen, D. P.; Burrell, K. H.; Casper, T. A.; Chu, M. S.; DeBoo, J. C.; Doyle, E. J.; Garofalo, A. M.; Gohil, P.; Gorelov, I. A.; Greenfield, C. M.; Groebner, R. J.; Heidbrink, W. W.; Hsieh, C.-L.; Hyatt, A. W.; Jayakumar, R.; Kinsey, J. E.; La Haye, R. J.; Lao, L. L.; Lasnier, C. J.; Lazarus, E. A.; Leonard, A. W.; Lin-Liu, Y. R.; Lohr, J.; Mahdavi, M. A.; Makowski, M. A.; Murakami, M.; Petty, C. C.; Pinsker, R. I.; Prater, R.; Rettig, C. L.; Rhodes, T. L.; Rice, B. W.; Strait, E. J.; Taylor, T. S.; Thomas, D. M.; Turnbull, A. D.; Watkins, J. G.; West, W. P.; Wong, K.-L.

    2001-05-01

    Significant progress has been made in obtaining high-performance discharges for many energy confinement times in the DIII-D tokamak [J. L. Luxon et al., Plasma Physics and Controlled Fusion Research (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159]. Normalized performance (measured by the product of βNH89 and indicative of the proximity to both conventional β limits and energy confinement quality, respectively) ˜10 has been sustained for >5 τE with qmin>1.5. These edge localized modes (ELMing) H-mode discharges have β˜5%, which is limited by the onset of resistive wall modes slightly above the ideal no-wall n=1 limit, with approximately 75% of the current driven noninductively. The remaining Ohmic current is localized near the half-radius. The DIII-D electron cyclotron heating system is being upgraded to replace this inductively driven current with localized electron cyclotron current drive (ECCD). Density control, which is required for effective ECCD, has been successfully demonstrated in long-pulse high-performance ELMing H-mode discharges with βNH89˜7 for up to 6.3 s. In plasma shapes compatible with good density control in the present divertor configuration, the achieved βN is somewhat less than that in the high βNH89=10 discharges.

  13. Effects of resistivity on linear plasma responses to resonant magnetic perturbations in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Kim, Juhyung; Kim, S. S.; Jhang, Hogun

    2016-09-01

    Numerical studies are made of the effects of resistivity on linear plasma responses to resonant magnetic perturbations (RMPs) in tokamaks based on a reduced magnetohydrodynamic model. From a local two-field model, it is suggested that the ratio of the poloidal electron advection to the resistivity diffusion rate α m can be a figure of merit parameter in linear RMP penetration physics. The shielding efficiency is governed by α m , and when α m ≳ 1 , RMPs are effectively shielded. Global simulations using a four-field model [Hazeltine and Meiss, Phys. Rep. 121, 1 (1985)] show that there exists an effective threshold of the perpendicular electron flow ( Ve , ⊥ c ) beyond which RMPs cannot penetrate. Resistivity is found to determine Ve , ⊥ c which increases as resistivity becomes higher, making RMP penetration easier. At low resistivity, small Ve , ⊥ c renders the RMP penetration sensitive to ion collisionality and the change in q95. The kink response is observed to be closely related to the residual level of RMPs at rational surfaces and can be also strongly affected by resistivity.

  14. Calculation of impurity poloidal rotation from measured poloidal asymmetries in the toroidal rotation of a tokamak plasma

    SciTech Connect

    Chrystal, C.; Burrell, K. H.; Groebner, R. J.; Kaplan, D. H.; Grierson, B. A.

    2012-10-15

    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.

  15. Module-type flat-field grazing-incidence spectrographs for large Tokamak (JT-60) plasma diagnosis

    NASA Astrophysics Data System (ADS)

    Nagata, Hiroshi; Kihara, Naoto; Yamashita, Takaji; Sugie, Tatsuo; Kubo, Hirotaka; Shiho, Makoto

    1990-09-01

    Module-type flat-field grazing-incidence spectrographs with holographic gratings and multichannel detectors for large TOKAMAK (JT-60) plasma diagnosis are developed. The spectrographs cover the different wavelength regions from 0.5-122 nm, and are set to measure impurity lines in the plasma every 20 ms with space resolution of 7 cm. The flat-field imaging properties with designed wavelength resolution were confirmed, and results of tokamak plasma measurements proved the value of these spectrographs for plasma diagnosis.

  16. Improvement of Plasma Performance with Lithium Wall Conditioning in Aditya Tokamak

    NASA Astrophysics Data System (ADS)

    B. Chowdhuri, M.; Manchanda, R.; Ghosh, J.; B. Bhatt, S.; Ajai, Kumar; K. Das, B.; A. Jadeja, K.; A. Raijada, P.; Manoj, Kumar; Banerjee, S.; Nilam, Ramaiya; Aniruddh, Mali; Ketan, M. Patel; Vinay, Kumar; Vasu, P.; Bhattacharyay, R.; L. Tanna, R.; Y. Shankara, Joisa; K. Atrey, P.; V. S. Rao, C.; Chenna Reddy, D.; K. Chattopadhyay, P.; Jha, R.; C. Saxena, Y.; Aditya Team

    2013-02-01

    Lithiumization of the vacuum vessel wall of the Aditya tokamak using a lithium rod exposed to glow discharge cleaning plasma has been done to understand its effect on plasma performance. After the Li-coating, an increment of ~100 eV in plasma electron temperature has been observed in most of the discharges compared to discharges without Li coating, and the shot reproducibility is considerably improved. Detailed studies of impurity behaviour and hydrogen recycling are made in the Li coated discharges by observing spectral lines of hydrogen, carbon, and oxygen in the visible region using optical fiber, an interference filter, and PMT based systems. A large reduction in O I signal (up to ~40% to 50%) and a 20% to 30% decrease of Hα signal indicate significant reduction of wall recycling. Furthermore, VUV emissions from O V and Fe XV monitored by a grazing incidence monochromator also show the reduction. Lower Fe XV emission indicates the declined impurity penetration to the core plasma in the Li coated discharges. Significant increase of the particle and energy confinement times and the reduction of Zeff of the plasma certainly indicate the improved plasma parameters in the Aditya tokamak after lithium wall conditioning.

  17. Deuterium--tritium plasmas in novel regimes in the Tokamak Fusion Test Reactor

    SciTech Connect

    Bell, M.G.; Batha, S.; Beer, M.; Bell, R.E.; Belov, A.; Berk, H.; Bernabei, S.; Bitter, M.; Breizman, B.; Bretz, N.L.; Budny, R.; Bush, C.E.; Callen, J.; Cauffman, S.; Chang, C.S.; Chang, Z.; Cheng, C.Z.; Darrow, D.S.; Dendy, R.O.; Dorland, W.; Duong, H.; Efthimion, P.C.; Ernst, D.; Evenson, H.; Fisch, N.J.; Fisher, R.; Fonck, R.J.; Fredrickson, E.D.; Fu, G.Y.; Furth, H.P.; Gorelenkov, N.N.; Goloborodko, V.Y.; Grek, B.; Grisham, L.R.; Hammett, G.W.; Hawryluk, R.J.; Heidbrink, W.; Herrmann, H.W.; Herrmann, M.C.; Hill, K.W.; Hogan, J.; Hooper, B.; Hosea, J.C.; Houlberg, W.A.; Hughes, M.; Jassby, D.L.; Jobes, F.C.; Johnson, D.W.; Kaita, R.; Kaye, S.; Kesner, J.; Kim, J.S.; Kissick, M.; Krasilnikov, A.V.; Kugel, H.; Kumar, A.; Lam, N.T.; Lamarche, P.; LeBlanc, B.; Levinton, F.M.; Ludescher, C.; Machuzak, J.; Majeski, R.P.; Manickam, J.; Mansfield, D.K.; Mauel, M.; Mazzucato, E.; McChesney, J.; McCune, D.C.; McKee, G.; McGuire, K.M.; Meade, D.M.; Medley, S.S.; Mikkelsen, D.R.; Mirnov, S.V.; Mueller, D.; Nagayama, Y.; Navratil, G.A.; Nazikian, R.; Okabayashi, M.; Osakabe, M.; Owens, D.K.; Park, H.K.; Park, W.; Paul, S.F.; Petrov, M.P.; Phillips, C.K.; Phillips, M.; Phillips, P.; Ramsey, A.T.; Rice, B.; Redi, M.H.; Rewoldt, G.; Reznik, S.; Roquemore, A.L.; Rogers, J.; Ruskov, E.; Sabbagh, S.A.; Sasao, M.; Schilling, G.; Schmidt, G.L.; Scott, S.D.; Semenov, I.; Senko, T.; Skinner, C.H.; Stevenson, T.; Strait, E.J.; Stratton, B.C.; Strachan, J.D.; Stodiek, W.; Synakowski, E.; Takahashi, H.; Tang, W.; Taylor, G.; Thompson, M.E.; von Goeler, S.; Von Halle, A.; Walters, R.T.; Wang, S.; White, R.; Wieland, R.M.; Williams, M.; Wilson, J.R.; Wong, K.L.; Wurden, G.A.; Yamada, M.; Yavorski, V.; Young, K.M.; Zakharov, L.; Zarnstorff, M.C.; Zweben, S.J.

    1997-05-01

    Experiments in the Tokamak Fusion Test Reactor (TFTR) [Phys. Plasmas {bold 2}, 2176 (1995)] have explored several novel regimes of improved tokamak confinement in deuterium{endash}tritium (D--T) plasmas, including plasmas with reduced or reversed magnetic shear in the core and high-current plasmas with increased shear in the outer region (high l{sub i}). New techniques have also been developed to enhance the confinement in these regimes by modifying the plasma-limiter interaction through {ital in situ} deposition of lithium. In reversed-shear plasmas, transitions to enhanced confinement have been observed at plasma currents up to 2.2 MA (q{sub a}{approx}4.3), accompanied by the formation of internal transport barriers, where large radial gradients develop in the temperature and density profiles. Experiments have been performed to elucidate the mechanism of the barrier formation and its relationship with the magnetic configuration and with the heating characteristics. The increased stability of high-current, high-l{sub i} plasmas produced by rapid expansion of the minor cross section, coupled with improvement in the confinement by lithium deposition has enabled the achievement of high fusion power, up to 8.7 MW, with D--T neutral beam heating. The physics of fusion alpha-particle confinement has been investigated in these regimes, including the interactions of the alphas with endogenous plasma instabilities and externally applied waves in the ion cyclotron range of frequencies. In D--T plasmas with q{sub 0}{gt}1 and weak magnetic shear in the central region, a toroidal Alfvn eigenmode instability driven purely by the alpha particles has been observed for the first time. The interactions of energetic ions with ion Bernstein waves produced by mode conversion from fast waves in mixed-species plasmas have been studied as a possible mechanism for transferring the energy of the alphas to fuel ions. {copyright} {ital 1997 American Institute of Physics.}

  18. Free boundary, high beta equilibrium in a large aspect ratio tokamak with nearly circular plasma boundary

    SciTech Connect

    Qin, H.; Reiman, A.

    1996-09-25

    An analytic solution is obtained for free-boundary, high-beta equilibria in large aspect ratio tokamaks with a nearly circular plasma boundary. In the absence of surface currents at the plasma-vacuum interface, the free-boundary equilibrium solution introduces constraints arising from the need to couple to an external vacuum field which is physically realizable with a reasonable set of external field coils. This places a strong constraint on the pressure profiles that are consistent with a given boundary shape at high {epsilon}{beta}{sub p}. The equilibrium solution also provides information on the flux surface topology. The plasma is bounded by a separatrix. Increasing the plasma pressure at fixed total current causes the plasma aperture to decrease in a manner that is described.

  19. Sawtooth Pacing by Real-Time Auxiliary Power Control in a Tokamak Plasma

    SciTech Connect

    Goodman, T. P.; Felici, F.; Sauter, O.; Graves, J. P.

    2011-06-17

    In the standard scenario of tokamak plasma operation, sawtooth crashes are the main perturbations that can trigger performance-degrading, and potentially disruption-generating, neoclassical tearing modes. This Letter demonstrates sawtooth pacing by real-time control of the auxiliary power. It is shown that the sawtooth crash takes place in a reproducible manner shortly after the removal of that power, and this can be used to precisely prescribe, i.e., pace, the individual sawteeth. In combination with preemptive stabilization of the neoclassical tearing modes, sawtooth pacing provides a new sawtooth control paradigm for improved performance in burning plasmas.

  20. Quasi-Isotropic Approximation of Geometrical Optics Method as Adequate Electrodynamical Basis for Tokamak Plasma Polarimetry

    NASA Astrophysics Data System (ADS)

    Bieg, Bohdan; Chrzanowski, Janusz; Kravtsov, Yury A.; Orsitto, Francesco

    Basic principles and recent findings of quasi-isotropic approximation (QIA) of a geometrical optics method are presented in a compact manner. QIA was developed in 1969 to describe electromagnetic waves in weakly anisotropic media. QIA represents the wave field as a power series in two small parameters, one of which is a traditional geometrical optics parameter, equal to wavelength ratio to plasma characteristic scale, and the other one is the largest component of anisotropy tensor. As a result, "" QIA ideally suits to tokamak polarimetry/interferometry systems in submillimeter range, where plasma manifests properties of weakly anisotropic medium.

  1. New Fluctuation Phenomena in the H-Mode Regime of Poloidal-Diverter Tokamak Plasmas

    NASA Astrophysics Data System (ADS)

    Slusher, R. E.; Surko, C. M.; Valley, J. F.; Crowley, T.; Mazzucato, E.; McGuire, K.

    1984-08-01

    A new kind of fluctuation is observed near the edge of plasmas in the PDX tokamak operating in the "H-mode" (improved-confinement) regime. These fluctuations are evidenced as vacuum-uv and density-fluctuation bursts at well-defined frequencies (Δωω<~0.1) in the range between 50 and 180 kHz. The bursts are correlated, both in space and in time, with changes in the temperature-density product near the plasma edge where large density and temperature gradients develop during the H mode.

  2. New fluctuation phenomena in the H-mode regime of poloidal-divertor tokamak plasmas

    SciTech Connect

    Slusher, R.E.; Surko, C.M.; Valley, J.F.; Crowley, T.; Mazzucato, E.; McGuire, K.

    1984-08-13

    A new kind of fluctuation is observed near the edge of plasmas in the PDX tokamak operating in the ''H-mode'' (improved-confinement) regime. These fluctuations are evidenced as vacuum-UV and density-fluctuation bursts at well-defined frequencies (..delta omega../..omega..< or approx. =0.1) in the range between 50 and 180 kHz. The bursts are correlated, both in space and in time, with changes in the temperature-density product near the plasma edge where large density and temperature gradients develop during the H mode.

  3. Microwave reflectometry for the study of density fluctuations in tokamak plasmas

    SciTech Connect

    Mazzucato, E.; Nazikian, R.

    1990-12-01

    The effect of small scale density fluctuations on the propagation of electromagnetic waves in an inhomogeneous magnetized plasma in the presence of a cutoff is investigated. It is shown that, provided the fluctuation scale length is greater than the free space wavelength of an incident plane wave, the scattered field is strongly enhanced from fluctuations near the turning point. Numerical results for wave propagation in a tokamak plasma demonstrate the feasibility of reflectometry for the localized measurement of density fluctuations in the range k {sub {perpendicular}} {rho}{sub i} {much lt} 1. 19 refs., 6 figs,

  4. Edge Plasma Boundary Layer Generated By Kink Modes in Tokamaks

    SciTech Connect

    L.E. Zakharov

    2010-11-22

    This paper describes the structure of the electric current generated by external kink modes at the plasma edge using the ideally conducting plasma model. It is found that the edge current layer is created by both wall touching and free boundary kink modes. Near marginal stability, the total edge current has a universal expression as a result of partial compensation of the δ-functional surface current by the bulk current at the edge. The resolution of an apparent paradox with the pressure balance across the plasma boundary in the presence of the surface currents is provided.

  5. Deuterium-tritium plasmas in novel regimes in the Tokamak Fusion Test Reactor

    SciTech Connect

    Bell, M.G.; Beer, M.; Batha, S.

    1997-02-01

    Experiments in the Tokamak Fusion Test Reactor (TFTR) have explored several novel regimes of improved tokamak confinement in deuterium-tritium (D-T) plasmas, including plasmas with reduced or reversed magnetic shear in the core and high-current plasmas with increased shear in the outer region (high-l{sub i}). New techniques have also been developed to enhance the confinement in these regimes by modifying the plasma-limiter interaction through in-situ deposition of lithium. In reversed-shear plasmas, transitions to enhanced confinement have been observed at plasma currents up to 2.2 MA (q{sub a} {approx} 4.3), accompanied by the formation of internal transport barriers, where large radial gradients develop in the temperature and density profiles. Experiments have been performed to elucidate the mechanism of the barrier formation and its relationship with the magnetic configuration and with the heating characteristics. The increased stability of high-current, high-l{sub i} plasmas produced by rapid expansion of the minor cross-section, coupled with improvement in the confinement by lithium deposition has enabled the achievement of high fusion power, up to 8.7 MW, with D-T neutral beam heating. The physics of fusion alpha-particle confinement has been investigated in these regimes, including the interactions of the alphas with endogenous plasma instabilities and externally applied waves in the ion cyclotron range of frequencies. In D-T plasmas with q{sub 0} > 1 and weak magnetic shear in the central region, a toroidal Alfven eigenmode instability driven purely by the alpha particles has been observed for the first time. The interactions of energetic ions with ion Bernstein waves produced by mode-conversion from fast waves in mixed-species plasmas have been studied as a possible mechanism for transferring the energy of the alphas to fuel ions.

  6. ADVANCES IN COMPREHENSIVE GYROKINETIC SIMULATIONS OF TRANSPORT IN TOKAMAKS

    SciTech Connect

    WALTZ,R.E; CANDY,J; HINTON,F.L; ESTRADA-MILA,C; KINSEY,J.E

    2004-10-01

    A continuum global gyrokinetic code GYRO has been developed to comprehensively simulate core turbulent transport in actual experimental profiles and enable direct quantitative comparisons to the experimental transport flows. GYRO not only treats the now standard ion temperature gradient (ITG) mode turbulence, but also treats trapped and passing electrons with collisions and finite {beta}, equilibrium ExB shear stabilization, and all in real tokamak geometry. Most importantly the code operates at finite relative gyroradius ({rho}{sub *}) so as to treat the profile shear stabilization and nonlocal effects which can break gyroBohm scaling. The code operates in either a cyclic flux-tube limit (which allows only gyroBohm scaling) or globally with physical profile variation. Bohm scaling of DIII-D L-mode has been simulated with power flows matching experiment within error bars on the ion temperature gradient. Mechanisms for broken gyroBohm scaling, neoclassical ion flows embedded in turbulence, turbulent dynamos and profile corrugations, are illustrated.

  7. Absolute intensity calibration of the 32-channel heterodyne radiometer on experimental advanced superconducting tokamak

    SciTech Connect

    Liu, X.; Zhao, H. L.; Liu, Y. Li, E. Z.; Han, X.; Ti, A.; Hu, L. Q.; Zhang, X. D.; Domier, C. W.; Luhmann, N. C.

    2014-09-15

    This paper presents the results of the in situ absolute intensity calibration for the 32-channel heterodyne radiometer on the experimental advanced superconducting tokamak. The hot/cold load method is adopted, and the coherent averaging technique is employed to improve the signal to noise ratio. Measured spectra and electron temperature profiles are compared with those from an independent calibrated Michelson interferometer, and there is a relatively good agreement between the results from the two different systems.

  8. Design and characterization of a 32-channel heterodyne radiometer for electron cyclotron emission measurements on experimental advanced superconducting tokamak

    SciTech Connect

    Han, X.; Liu, X.; Liu, Y. Li, E. Z.; Hu, L. Q.; Gao, X.; Domier, C. W.; Luhmann, N. C.

    2014-07-15

    A 32-channel heterodyne radiometer has been developed for the measurement of electron cyclotron emission (ECE) on the experimental advanced superconducting tokamak (EAST). This system collects X-mode ECE radiation spanning a frequency range of 104–168 GHz, where the frequency coverage corresponds to a full radial coverage for the case with a toroidal magnetic field of 2.3 T. The frequency range is equally spaced every 2 GHz from 105.1 to 167.1 GHz with an RF bandwidth of ∼500 MHz and the video bandwidth can be switched among 50, 100, 200, and 400 kHz. Design objectives and characterization of the system are presented in this paper. Preliminary results for plasma operation are also presented.

  9. Design of a collective scattering system for small scale turbulence study in Korea Superconducting Tokamak Advanced Research

    NASA Astrophysics Data System (ADS)

    Lee, W.; Park, H. K.; Lee, D. J.; Nam, Y. U.; Leem, J.; Kim, T. K.

    2016-04-01

    The design characteristics of a multi-channel collective (or coherent) scattering system for small scale turbulence study in Korea Superconducting Tokamak Advanced Research (KSTAR), which is planned to be installed in 2017, are given in this paper. A few critical issues are discussed in depth such as the Faraday and Cotton-Mouton effects on the beam polarization, radial spatial resolution, probe beam frequency, polarization, and power. A proper and feasible optics with the 300 GHz probe beam, which was designed based on these issues, provides a simultaneous measurement of electron density fluctuations at four discrete poloidal wavenumbers up to 24 cm-1. The upper limit corresponds to the normalized wavenumber kθρe of ˜0.15 in nominal KSTAR plasmas. To detect the scattered beam power and extract phase information, a quadrature detection system consisting of four-channel antenna/detector array and electronics will be employed.

  10. Observation of pedestal turbulence in edge localized mode-free H-mode on experimental advanced superconducting tokamak

    NASA Astrophysics Data System (ADS)

    Han, X.; Zhang, T.; Zhang, S. B.; Wang, Y. M.; Shi, T. H.; Liu, Z. X.; Kong, D. F.; Qu, H.; Gao, X.

    2014-10-01

    Two different pedestal turbulence structures have been observed in edge localized mode-free phase of H-mode heated by lower hybrid wave and RF wave in ion cyclotron range of frequencies (ICRF) on experimental advanced superconducting tokamak. When the fraction of ICRF power PICRF/Ptotal exceeds 0.7, coherent mode is observed. The mode is identified as an electromagnetic mode, rotating in electron diamagnetic direction with a frequency around 50 kHz and toroidal mode number n = -3. Whereas when PICRF/Ptotal is less than 0.7, harmonic mode with frequency f = 40-300 kHz appears instead. The characteristics of these two modes are demonstrated preliminarily. The threshold value of heating power and also the plasma parameters are distinct.

  11. Observation of pedestal turbulence in edge localized mode-free H-mode on experimental advanced superconducting tokamak

    SciTech Connect

    Han, X. Zhang, T.; Zhang, S. B.; Wang, Y. M.; Shi, T. H.; Liu, Z. X.; Kong, D. F.; Qu, H.; Gao, X.

    2014-10-15

    Two different pedestal turbulence structures have been observed in edge localized mode-free phase of H-mode heated by lower hybrid wave and RF wave in ion cyclotron range of frequencies (ICRF) on experimental advanced superconducting tokamak. When the fraction of ICRF power P{sub ICRF}/P{sub total} exceeds 0.7, coherent mode is observed. The mode is identified as an electromagnetic mode, rotating in electron diamagnetic direction with a frequency around 50 kHz and toroidal mode number n = −3. Whereas when P{sub ICRF}/P{sub total} is less than 0.7, harmonic mode with frequency f = 40–300 kHz appears instead. The characteristics of these two modes are demonstrated preliminarily. The threshold value of heating power and also the plasma parameters are distinct.

  12. Design of a collective scattering system for small scale turbulence study in Korea Superconducting Tokamak Advanced Research.

    PubMed

    Lee, W; Park, H K; Lee, D J; Nam, Y U; Leem, J; Kim, T K

    2016-04-01

    The design characteristics of a multi-channel collective (or coherent) scattering system for small scale turbulence study in Korea Superconducting Tokamak Advanced Research (KSTAR), which is planned to be installed in 2017, are given in this paper. A few critical issues are discussed in depth such as the Faraday and Cotton-Mouton effects on the beam polarization, radial spatial resolution, probe beam frequency, polarization, and power. A proper and feasible optics with the 300 GHz probe beam, which was designed based on these issues, provides a simultaneous measurement of electron density fluctuations at four discrete poloidal wavenumbers up to 24 cm(-1). The upper limit corresponds to the normalized wavenumber kθρe of ∼0.15 in nominal KSTAR plasmas. To detect the scattered beam power and extract phase information, a quadrature detection system consisting of four-channel antenna/detector array and electronics will be employed.

  13. Studies of instability and transport in tokamak plasmas with very weak magnetic shear

    SciTech Connect

    Dong, J.Q.; Zhang, Y.Z. |; Mahajan, S.M.

    1997-04-01

    Ion temperature gradient (ITG or {eta}{sub i}) driven microinstabilities are studied, using kinetic theory, for tokamak plasmas with very weak (positive or negative) magnetic shear (VWS). The gradient of magnetic shear as well as the effects of parallel and perpendicular velocity shear (v{prime}{sub {parallel}} and v{prime}{sub E}) are included in the defining equations. Two eigenmodes: the double (D) and the global (G) are found to coexist. Parametric dependence of these instabilities, and of the corresponding quasilinear transport is systematically analyzed. It is shown that, in VWS plasmas, a parallel velocity shear (PVS) may stabilize or destabilize the modes, depending on the individual as well as the relative signs of PVS and of the gradient of magnetic shear. The quasilinear transport induced by the instabilities may be significantly reduced with PVS in VWS plasmas. The v{prime}{sub E} values required to completely suppress the instabilities are much lower in VWS plasmas than they are in normal plasmas. Possible correlations with tokamak experiments are discussed.

  14. Phase locking of multi-helicity neoclassical tearing modes in tokamak plasmas

    SciTech Connect

    Fitzpatrick, Richard

    2015-04-15

    The attractive “hybrid” tokamak scenario combines comparatively high q{sub 95} operation with improved confinement compared with the conventional H{sub 98,y2} scaling law. Somewhat unusually, hybrid discharges often exhibit multiple neoclassical tearing modes (NTMs) possessing different mode numbers. The various NTMs are eventually observed to phase lock to one another, giving rise to a significant flattening, or even an inversion, of the core toroidal plasma rotation profile. This behavior is highly undesirable because the loss of core plasma rotation is known to have a deleterious effect on plasma stability. This paper presents a simple, single-fluid, cylindrical model of the phase locking of two NTMs with different poloidal and toroidal mode numbers in a tokamak plasma. Such locking takes place via a combination of nonlinear three-wave coupling and conventional toroidal coupling. In accordance with experimental observations, the model predicts that there is a bifurcation to a phase-locked state when the frequency mismatch between the modes is reduced to one half of its original value. In further accordance, the phase-locked state is characterized by the permanent alignment of one of the X-points of NTM island chains on the outboard mid-plane of the plasma, and a modified toroidal angular velocity profile, interior to the outermost coupled rational surface, which is such that the core rotation is flattened, or even inverted.

  15. Spatial localization of resistive drift wave structure in tokamak edge plasmas with an embedded magnetic island

    SciTech Connect

    Hu, Shilin; Qu, Hongpeng; Li, Jiquan; Kishimoto, Y.

    2014-10-15

    Resistive drift wave instability is investigated numerically in tokamak edge plasma confined by sheared slab magnetic field geometry with an embedded magnetic island. The focus is on the structural characteristics of eigenmode inside the island, where the density profile tends to be flattened. A transition of the dominant eigenmode occurs around a critical island width w{sub c}. For thin islands with a width below w{sub c}, two global long wavelength eigenmodes with approximately the same growth rate but different eigenfrequency are excited, which are stabilized by the magnetic island through two-dimensional mode coupling in both x and y (corresponding to radial and poloidal in tokamak) directions. On the other hand, a short wavelength eigenmode, which is destabilized by thick islands with a width above w{sub c}, dominates the edge fluctuation, showing a prominent structural localization in the region between the X-point and the O-point of the magnetic island. The main destabilization mechanism is identified as the mode coupling in the y direction, which is similar to the so-called toroidal coupling in tokamak plasmas. These three eigenmodes may coexist in the drift wave fluctuation for the island with a width around w{sub c}. It is demonstrated that the structural localization results mainly from the quasilinear flattening of density profile inside the magnetic island.

  16. Integrated modelling of the Globus-M tokamak plasma and a comparison with SOL width scaling

    NASA Astrophysics Data System (ADS)

    Senichenkov, I. Yu.; Kaveeva, E. G.; Gogoleva, A. V.; Vekshina, E. O.; Zadvitskiy, G. V.; Molchanov, P. A.; Rozhansky, V. A.; Voskoboynikov, S. P.; Khromov, N. A.; Lepikhov, S. A.; Gusev, V. K.; The Globus-M Team

    2015-05-01

    Recently a scheme for the coupling of the one-dimensional core transport code ASTRA and the two-dimensional edge transport code B2SOLPS was developed, thus providing the integrated modelling of tokamak discharge. Here, this scheme is improved by taking impurities into account and by considering a real flux surface shape using the equilibrium code SPIDER. This integrated modelling is applied to discharges of the spherical tokamak Globus-M to study the dependence of the scrape-off layer (SOL) width and divertor heat loads on the discharge power and the plasma current. Since these values, together with the magnetic field, are relatively small in Globus-M, this study can test the existing scaling against data in a wider range of tokamak operational parameters. The modelling results agree reasonably with Thomson scattering and Langmuir probe measurements and allow, in principle, the determination of the physical mechanisms responsible for the SOL structure formation. It is found that the SOL width is approximately inversely proportional to the plasma current, in agreement with existing experimental scaling, while its dependence on discharge power is found to be quite weak.

  17. 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.

  18. Alpha particle losses from Tokamak Fusion Test Reactor deuterium{endash}tritium plasmas

    SciTech Connect

    Darrow, D.S.; Zweben, S.J.; Batha, S.; Budny, R.V.; Bush, C.E.; Chang, Z.; Cheng, C.Z.; Duong, H.H.; Fang, J.; Fisch, N.J.; Fischer, R.; Fredrickson, E.D.; Fu, G.Y.; Heeter, R.F.; Heidbrink, W.W.; Herrmann, H.W.; Herrmann, M.C.; Hill, K.; Jaeger, E.F.; James, R.; Majeski, R.; Medley, S.S.; Murakami, M.; Petrov, M.; Phillips, C.K.; Redi, M.H.; Ruskov, E.; Spong, D.A.; Strait, E.J.; Taylor, G.; White, R.B.; Wilson, J.R.; Wong, K.; Zarnstorff, M.C.

    1996-05-01

    Because alpha particle losses can have a significant influence on tokamak reactor viability, the loss of deuterium{endash}tritium alpha particles from the Tokamak Fusion Test Reactor (TFTR) [K. M. McGuire {ital et} {ital al}., Phys. Plasmas {bold 2}, 2176 (1995)] has been measured under a wide range of conditions. In TFTR, first orbit loss and stochastic toroidal field ripple diffusion are always present. Other losses can arise due to magnetohydrodynamic instabilities or due to waves in the ion cyclotron range of frequencies. No alpha particle losses have yet been seen due to collective instabilities driven by alphas. Ion Bernstein waves can drive large losses of fast ions from TFTR, and details of those losses support one element of the alpha energy channeling scenario. {copyright} {ital 1996 American Institute of Physics.}

  19. x-ray irradiation analysis based on wavelet transform in tokamak plasma.

    PubMed

    Ghanbari, K; Ghoranneviss, M; Elahi, A Salar; Saviz, S

    2014-01-01

    Hard x-ray emission from the Runaway electrons is an important issue in tokamaks. Suggesting methods to reduce the Runaway electrons and therefore the emitted hard x-ray is important for tokamak plasma operation. In this manuscript, we have investigated the effects of external fields on hard x-ray intensity and Magneto-Hydro-Dynamic (MHD) activity. In other words, we have presented the effects of positive biased limiter and Resonant Helical Field (RHF) on the MHD fluctuations and hard x-ray emission from the Runaway electrons. MHD activity and hard x-ray intensity were analyzed using Wavelet transform in the presence of external fields and without them. The results show that the MHD activity and therefore the hard x-ray intensity can be controlled by the external electric and magnetic fields.

  20. Selection of materials for tokamak plasma facing elements based on a liquid tin capillary pore system

    NASA Astrophysics Data System (ADS)

    Lyublinski, I. E.; Vertkov, A. V.; Zharkov, M. Yu; Sevryukov, O. N.; Dzhumaev, P. S.; Shumskiy, V. A.; Ivannikov, A. A.

    2016-09-01

    Capillary-Pore Systems (CPS) filled by liquid metals are considered as an alternative solution of materials choice for plasma facing component of tokamak reactor. Tin is viewed as one of the candidates for CPS because it has lower corrosiveness than gallium and lower saturated vapour pressure compared to lithium. The corrosion resistance of Mo, Nb and W in pure liquid tin was investigated. The corrosion tests were carried out in the static isothermal conditions at a temperature up to 1050°C. As a result of the corrosion study, it was found that Mo does not corrode in liquid Sn, as opposed to Nb and is compatible with liquid tin in temperatures of up to approx. 1000°C. This allows considering Mo as an alloy base material of the in-vessel tokamak elements based on liquid tin capillary pore systems.

  1. Edge localized mode characteristics during edge localized mode mitigation by supersonic molecular beam injection in Korea Superconducting Tokamak Advanced Research

    SciTech Connect

    Lee, H. Y.; Hong, J. H.; Jang, J. H.; Park, J. S.; Choe, Wonho; Hahn, S. H.; Bak, J. G.; Lee, J. H.; Ko, W. H.; Lee, K. D.; Lee, S. H.; Lee, H. H.; Juhn, J.-W.; Kim, H. S.; Yoon, S. W.; Han, H.; Ghim, Y.-C.

    2015-12-15

    It has been reported that supersonic molecular beam injection (SMBI) is an effective means of edge localized mode (ELM) mitigation. This paper newly reports the changes in the ELM, plasma profiles, and fluctuation characteristics during ELM mitigation by SMBI in Korea Superconducting Tokamak Advanced Research. During the mitigated ELM phase, the ELM frequency increased by a factor of 2–3 and the ELM size, which was estimated from the D{sub α} amplitude, the fractional changes in the plasma-stored energy and the line-averaged electron density, and divertor heat flux during an ELM burst, decreased by a factor of 0.34–0.43. Reductions in the electron and ion temperatures rather than in the electron density were observed during the mitigated ELM phase. In the natural ELM phase, frequency chirping of the plasma fluctuations was observed before the ELM bursts; however, the ELM bursts occurred without changes in the plasma fluctuation frequency in the mitigated ELM phase.

  2. Far ultraviolet polychromator for spectroscopic characterization of the tokamak divertor and plasma scrape-off layer

    SciTech Connect

    Soukhanovskii, V.A.; Stutman, D.; May, M.J.; Finkenthal, M.; Moos, H.W.; Terry, J.L.; Goetz, J.A.; Lipschultz, B.

    1999-01-01

    The Plasma Spectroscopy Group of The Johns Hopkins University is developing diagnostics for spectroscopic characterization of the tokamak plasma scrape-off layer and divertor regions. A far ultraviolet polychromator has been designed for radiative divertor studies at the Alcator C-Mod and D-IIID tokamaks. Local measurements of resonant transitions of lithium- to boron-like ions of intrinsic or seeded low {ital Z} impurity elements will be performed along multiple chords around the {ital X} point. Planar diffraction gratings and stacked grids will be used for dispersion and angular collimation of radiation. Phosphor wavelength converters coupled to a photomultiplier tube by an optical fiber will be used as detectors. The design provides a wavelength resolution of {approx_equal}10 {Angstrom}, a spatial resolution of {le}2 cm, and an adequate photometric sensitivity. The in-vessel instrument, proposed for the Alcator C-Mod tokamak, will measure intensities of the lines at 1240 (N V), 765, 923 (N IV), and 990 {Angstrom} (N III). The port-mounted polychromator at DIII-D will be able to monitor intensities of 1550 (C IV), 977, 1176 (C III), and 1335 {Angstrom} (C II) lines. This, together with visible and bolometric diagnostics, should enable estimates of power losses, charge state distribution and local transport of the impurity ions in the divertor. A one-channel prototype of the C-Mod and D-IIID instruments is being built for the CDX-U spherical tokamak. Line-integrated brightnesses of the 2s{endash}2p transition at 1550 {Angstrom} will be measured and inverted to obtain C IV emissivity distribution. {copyright} {ital 1999 American Institute of Physics.}

  3. Fractional resonances between waves and energetic particles in tokamak plasmas.

    PubMed

    Kramer, G J; Chen, L; Fisher, R K; Heidbrink, W W; Nazikian, R; Pace, D C; Van Zeeland, M A

    2012-07-20

    From numerical simulation and analytical modeling it is shown that fast ions can resonate with plasma waves at fractional values of the particle drift-orbit transit frequency when the plasma wave amplitude is sufficiently large. The fractional resonances, which are caused by a nonlinear interaction between the particle orbit and the wave, give rise to an increased density of resonances in phase space which reduces the threshold for stochastic transport. The effects of the fractional resonances on spatial and energy transport are illustrated for an energetic particle geodesic acoustic mode but they apply equally well to other types of MHD activity.

  4. The interaction between fishbone modes and shear Alfvén waves in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    He, Hongda; Liu, Yueqiang; Dong, J. Q.; Hao, G. Z.; Wu, Tingting; He, Zhixiong; Zhao, K.

    2016-05-01

    The resonant interaction between the energetic particle triggered fishbone mode and the shear Alfvén waves is computationally investigated and firmly demonstrated based on a tokamak plasma equilibrium, using the self-consistent MHD-kinetic hybrid code MARS-K (Liu et al 2008 Phys. Plasmas 15 112503). This type of continuum resonance, occurring critically due to the mode’s toroidal rotation in the plasma frame, significantly modifies the eigenmode structure of the fishbone instability, by introducing two large peaks of the perturbed parallel current density near but offside the q  =  1 rational surface (q is the safety factor). The self-consistently computed radial plasma displacement substantially differs from that being assumed in the conventional fishbone theory.

  5. High Resolution Transmission Grating Spectrometer for Edge Toroidal Rotation Measurements of Tokamak Plasmas

    SciTech Connect

    Graf, A; May, M; Beiersdorfer, P; Magee, E; Lawrence, M; Terry, J; Rice, J

    2004-04-29

    We present a high throughput (f/3) visible (3500 - 7000 Angstrom) Doppler spectrometer for toroidal rotation velocity measurements of the Alcator C-Mod tokamak plasma. The spectrometer has a temporal response of 1 ms and a rotation velocity sensitivity of {approx}10{sup 5} cm/s. This diagnostic will have a tangential view and map out the plasma rotation at several locations along the outer half of the minor radius (r/a > 0.5). The plasma rotation will be determined from the Doppler shifted wavelengths of D{sub alpha} and magnetic and electric dipole transitions of highly ionized impurities in the plasma. The fast time resolution and high spectral resolving power are possible due to a 6' diameter circular transmission grating that is capable of {lambda}/{Delta}{lambda} {approx} 15500 at 5769 Angstrom in conjunction with a 50 {micro}m slit.

  6. Millimeter-Wave Imaging Technology Advancements for Plasma Diagnostics Applications

    NASA Astrophysics Data System (ADS)

    Kong, Xiangyu

    To realize fusion plant, the very first step is to understand the fundamental physics of materials under fusion conditions, i.e. to understand fusion plasmas. Our research group, Plasma Diagnostics Group, focuses on developing advanced tools for physicists to extract as much information as possible from fusion plasmas at millions degrees. The Electron Cyclotron Emission Imaging (ECEI) diagnostics is a very useful tool invented in this group to study fusion plasma electron temperature and it fluctuations. This dissertation presents millimeter wave imaging technology advances recently developed in this group to improve the ECEI system. New technologies made it more powerful to image and visualize magneto-hydrodynamics (MHD) activities and micro-turbulence in fusion plasmas. Topics of particular emphasis start from development of miniaturized elliptical substrate lens array. This novel substrate lens array replaces the previous generation substrate lens, hyper-hemispherical substrate lens, in terms of geometry. From the optical performance perspective, this substitution not only significantly simplifies the optical system with improved optical coupling, but also enhances the RF/LO coupling efficiency. By the benefit of the mini lens focusing properties, a wideband dual-dipole antenna array is carefully designed and developed. The new antenna array is optimized simultaneously for receiving both RF and LO, with sharp radiation patterns, low side-lobe levels, and less crosstalk between adjacent antennas. In addition, a high frequency antenna is also developed, which extends the frequency limit from 145 GHz to 220 GHz. This type of antenna will be used on high field operation tokamaks with toroidal fields in excess of 3 Tesla. Another important technology advance is so-called extended bandwidth double down-conversion electronics. This new electronics extends the instantaneous IF coverage from 2 to 9.2 GHz to 2 to 16.4 GHz. From the plasma point of view, it means that the

  7. Advanced methods in global gyrokinetic full f particle simulation of tokamak transport

    SciTech Connect

    Ogando, F.; Heikkinen, J. A.; Henriksson, S.; Janhunen, S. J.; Kiviniemi, T. P.; Leerink, S.

    2006-11-30

    A new full f nonlinear gyrokinetic simulation code, named ELMFIRE, has been developed for simulating transport phenomena in tokamak plasmas. The code is based on a gyrokinetic particle-in-cell algorithm, which can consider electrons and ions jointly or separately, as well as arbitrary impurities. The implicit treatment of the ion polarization drift and the use of full f methods allow for simulations of strongly perturbed plasmas including wide orbit effects, steep gradients and rapid dynamic changes. This article presents in more detail the algorithms incorporated into ELMFIRE, as well as benchmarking comparisons to both neoclassical theory and other codes.Code ELMFIRE calculates plasma dynamics by following the evolution of a number of sample particles. Because of using an stochastic algorithm its results are influenced by statistical noise. The effect of noise on relevant magnitudes is analyzed.Turbulence spectra of FT-2 plasma has been calculated with ELMFIRE, obtaining results consistent with experimental data.

  8. Modeling of transport phenomena in tokamak plasmas with neural networks

    SciTech Connect

    Meneghini, O.; Luna, C. J.; Smith, S. P.; Lao, L. L.

    2014-06-15

    A new transport model that uses neural networks (NNs) to yield electron and ion heat flux profiles has been developed. Given a set of local dimensionless plasma parameters similar to the ones that the highest fidelity models use, the NN model is able to efficiently and accurately predict the ion and electron heat transport profiles. As a benchmark, a NN was built, trained, and tested on data from the 2012 and 2013 DIII-D experimental campaigns. It is found that NN can capture the experimental behavior over the majority of the plasma radius and across a broad range of plasma regimes. Although each radial location is calculated independently from the others, the heat flux profiles are smooth, suggesting that the solution found by the NN is a smooth function of the local input parameters. This result supports the evidence of a well-defined, non-stochastic relationship between the input parameters and the experimentally measured transport fluxes. The numerical efficiency of this method, requiring only a few CPU-μs per data point, makes it ideal for scenario development simulations and real-time plasma control.

  9. Scattering of radio frequency waves by blobs in tokamak plasmas

    SciTech Connect

    Ram, Abhay K.; Hizanidis, Kyriakos; Kominis, Yannis

    2013-05-15

    The density fluctuations and blobs present in the edge region of magnetic fusion devices can scatter radio frequency (RF) waves through refraction, reflection, diffraction, and coupling to other plasma waves. This, in turn, affects the spectrum of the RF waves and the electromagnetic power that reaches the core of the plasma. The usual geometric optics analysis of RF scattering by density blobs accounts for only refractive effects. It is valid when the amplitude of the fluctuations is small, of the order of 10%, compared to the background density. In experiments, density fluctuations with much larger amplitudes are routinely observed, so that a more general treatment of the scattering process is needed. In this paper, a full-wave model for the scattering of RF waves by a blob is developed. The full-wave approach extends the range of validity well beyond that of geometric optics; however, it is theoretically and computationally much more challenging. The theoretical procedure, although similar to that followed for the Mie solution of Maxwell's equations, is generalized to plasmas in a magnetic field. Besides diffraction and reflection, the model includes coupling to a different plasma wave than the one imposed by the external antenna structure. In the model, it is assumed that the RF waves interact with a spherical blob. The plasma inside and around the blob is cold, homogeneous, and imbedded in a uniform magnetic field. After formulating the complete analytical theory, the effect of the blob on short wavelength electron cyclotron waves and longer wavelength lower hybrid waves is studied numerically.

  10. Residual gas analysis for long-pulse, advanced tokamak operation.

    PubMed

    Klepper, C C; Hillis, D L; Bucalossi, J; Douai, D; Oddon, P; Vartanian, S; Colas, L; Manenc, L; Pégourié, B

    2010-10-01

    A shielded residual gas analyzer (RGA) system on Tore Supra can function during plasma operation and is set up to monitor the composition of the neutral gas in one of the pumping ducts of the toroidal pumped limited. This "diagnostic RGA" has been used in long-pulse (up to 6 min) discharges for continuous monitoring of up to 15 masses simultaneously. Comparison of the RGA-measured evolution of the H(2)/D(2) isotopic ratio in the exhaust gas to that measured by an energetic neutral particle analyzer in the plasma core provides a way to monitor the evolution of particle balance. RGA monitoring of corrective H(2) injection to maintain proper minority heating is providing a database for improved ion cyclotron resonance heating, potentially with RGA-base feedback control. In very long pulses (>4 min) absence of significant changes in the RGA-monitored, hydrocarbon particle pressures is an indication of proper operation of the actively cooled, carbon-based plasma facing components. Also H(2) could increase due to thermodesorption of overheated plasma facing components.

  11. Residual gas analysis for long-pulse, advanced tokamak operation

    SciTech Connect

    Klepper, C. C.; Hillis, D. L.; Bucalossi, J.; Douai, D.; Oddon, P.; Vartanian, S.; Colas, L.; Manenc, L.; Pegourie, B.

    2010-10-15

    A shielded residual gas analyzer (RGA) system on Tore Supra can function during plasma operation and is set up to monitor the composition of the neutral gas in one of the pumping ducts of the toroidal pumped limited. This ''diagnostic RGA'' has been used in long-pulse (up to 6 min) discharges for continuous monitoring of up to 15 masses simultaneously. Comparison of the RGA-measured evolution of the H{sub 2}/D{sub 2} isotopic ratio in the exhaust gas to that measured by an energetic neutral particle analyzer in the plasma core provides a way to monitor the evolution of particle balance. RGA monitoring of corrective H{sub 2} injection to maintain proper minority heating is providing a database for improved ion cyclotron resonance heating, potentially with RGA-base feedback control. In very long pulses (>4 min) absence of significant changes in the RGA-monitored, hydrocarbon particle pressures is an indication of proper operation of the actively cooled, carbon-based plasma facing components. Also H{sub 2} could increase due to thermodesorption of overheated plasma facing components.

  12. Residual Gas Analysis for Long-Pulse, Advanced Tokamak Operation

    SciTech Connect

    Klepper, C Christopher; Hillis, Donald Lee; Bucalossi, J.; Douai, D.; OddonCEA, IRFM, P.; VartanianCEA-Cadarach, S.; Colas, L.; Manenc, L.; Pegourie, B.

    2010-01-01

    A shielded residual gas analyzer RGA system on Tore Supra can function during plasma operation and is set up to monitor the composition of the neutral gas in one of the pumping ducts of the toroidal pumped limited. This diagnostic RGA has been used in long-pulse up to 6 min discharges for continuous monitoring of up to 15 masses simultaneously. Comparison of the RGA-measured evolution of the H2 /D2 isotopic ratio in the exhaust gas to that measured by an energetic neutral particle analyzer in the plasma core provides a way to monitor the evolution of particle balance. RGA monitoring of corrective H2 injection to maintain proper minority heating is providing a database for improved ion cyclotron resonance heating, potentially with RGA-base feedback control. In very long pulses 4 min absence of significant changes in the RGA-monitored, hydrocarbon particle pressures is an indication of proper operation of the actively cooled, carbon-based plasma facing components. Also H2 could increase due to thermodesorption of overheated plasma facing components. 2010 American Institute of Physics.

  13. Residual gas analysis for long-pulse, advanced tokamak operationa)

    NASA Astrophysics Data System (ADS)

    Klepper, C. C.; Hillis, D. L.; Bucalossi, J.; Douai, D.; Oddon, P.; Vartanian, S.; Colas, L.; Manenc, L.; Pégourié, B.

    2010-10-01

    A shielded residual gas analyzer (RGA) system on Tore Supra can function during plasma operation and is set up to monitor the composition of the neutral gas in one of the pumping ducts of the toroidal pumped limited. This "diagnostic RGA" has been used in long-pulse (up to 6 min) discharges for continuous monitoring of up to 15 masses simultaneously. Comparison of the RGA-measured evolution of the H2/D2 isotopic ratio in the exhaust gas to that measured by an energetic neutral particle analyzer in the plasma core provides a way to monitor the evolution of particle balance. RGA monitoring of corrective H2 injection to maintain proper minority heating is providing a database for improved ion cyclotron resonance heating, potentially with RGA-base feedback control. In very long pulses (>4 min) absence of significant changes in the RGA-monitored, hydrocarbon particle pressures is an indication of proper operation of the actively cooled, carbon-based plasma facing components. Also H2 could increase due to thermodesorption of overheated plasma facing components.

  14. Plasma-material Interaction Studies On Lithium And Lithiated Substrates During Compact Tokamak Operation

    SciTech Connect

    Nieto, M.; Allain, J. P.; Hassanein, A.; Titov, V.; Hendricks, M.; Gray, T.; Kaita, R.; Kugel, H.; Majeski, R.; Mansfield, D.; Spaleta, J.; Timberlake, J.

    2006-12-04

    The role of lithium on the modification of recycling regimes in fusion reactors has renewed interest of previous lithium supershot experiments carried out in TFTR. There is a need to understand the interaction between edge plasmas and lithiated plasma-facing components (PFCs), which have the potential of enabling fusion reactors to operate at low-recycling regimes. The Interaction of Materials with Particles and Components Testing (IMPACT) facility at Argonne National Laboratory is currently collaborating with Princeton Plasma Physics Laboratory (PPPL) to conduct lithiated surface studies for the National Spherical Tokamak Experiment (NSTX) and the Current Drive eXperiment - Upgrade (CDX-U). IMPACT has the necessary tools to perform experiments that diagnose the surface dynamics of lithium thin films on metallic and non-metallic substrates, and can be monitored with multiple in-situ techniques (LEISS, AES, QMS and XPS) capturing real-time surface dynamics. Therefore, these techniques are available during He+ and D+ irradiation. Surface sputtering measurements can be performed using a quartz crystal microbalance -- dual crystal unit (QCM-DCU) with very high sensitivity.Initial results suggest that lithium intercalation into graphite occurs quite rapidly and only a fraction lithium can be kept on the surface. On metallic substrates this intercalation is absent. Additional results of Li/metal systems show lithium surface self-healing with temperature. It was also found that the presence of lithium seems to inhibit hydrocarbon formation during D+ bombardment of graphite. Experiments in CDX-U have tested the effect of both solid and liquid lithium PFCs on tokamak plasmas, and significant changes in tokamak operation are observed. These include a strong reduction in both recycling and impurity levels in the gas phase, lowered loop voltage during ohmic operation, and an increased electron temperature at the edge.

  15. Renewable boron carbide coating in plasma shots of tokamak Т11-М

    NASA Astrophysics Data System (ADS)

    Buzhinskij, O. I.; Barsuk, V. A.; Otroshchenko, V. G.

    2009-06-01

    Experimental results on boronization in plasma shots of the tokamak T-11M are presented. Non-toxic and not explosive metacarborane C 2H 12B 10 was used in the boron deposition process. Experiments have been carried out in shots with parameters: toroidal field ˜1-1.2 Т, plasma current Ip = 70 кА, average shot duration tp ˜ 150 ms and electron density along the central chord ne ˜ 2.5 × 10 13 cm -3. As a result of experiment, a dense film of ˜0.2 microns thickness with good adhesion to a surface has formed on the reference specimens after 8 s boronization. After boronization the impurities in wall areas have been suppressed. High vacuum characteristics of the discharge chamber were stabilized. Working vacuum was reached without a preliminary induction heating and cleaning by a glow discharge, and stabilization of the plasma filament has improved. Shot duration without disruption at densities of ne = 1.3 × 10 13 сm -3, Ip = 70 кА was 350 ms and ne = 4.64 × 10 13 сm -3, Ip = 70 кА was 250 ms. High repeatability of experimental results has appeared. Developed technology opens an opportunity of practical production of renewable structured boron-carbon coatings with use of plasma shots in large-scale tokamaks, such as DIII-D, JET, JT-60 UP, ITER, DEMO.

  16. Identification and control of plasma vertical position using neural network in Damavand tokamak

    SciTech Connect

    Rasouli, H.; Rasouli, C.; Koohi, A.

    2013-02-15

    In this work, a nonlinear model is introduced to determine the vertical position of the plasma column in Damavand tokamak. Using this model as a simulator, a nonlinear neural network controller has been designed. In the first stage, the electronic drive and sensory circuits of Damavand tokamak are modified. These circuits can control the vertical position of the plasma column inside the vacuum vessel. Since the vertical position of plasma is an unstable parameter, a direct closed loop system identification algorithm is performed. In the second stage, a nonlinear model is identified for plasma vertical position, based on the multilayer perceptron (MLP) neural network (NN) structure. Estimation of simulator parameters has been performed by back-propagation error algorithm using Levenberg-Marquardt gradient descent optimization technique. The model is verified through simulation of the whole closed loop system using both simulator and actual plant in similar conditions. As the final stage, a MLP neural network controller is designed for simulator model. In the last step, online training is performed to tune the controller parameters. Simulation results justify using of the NN controller for the actual plant.

  17. Generation of plasma rotation in a tokamak by ion-cyclotron absorption of fast Alfven waves

    SciTech Connect

    F.W. Perkins; R.B. White; P. Bonoli

    2000-06-13

    Control of rotation in tokamak plasmas provides a method for suppressing fine-scale turbulent transport by velocity shear and for stabilizing large-scale magnetohydrodynamic instabilities via a close-fitting conducting shell. The experimental discovery of rotation in a plasma heated by the fast-wave minority ion cyclotron process is important both as a potential control method for a fusion reactor and as a fundamental issue, because rotation arises even though this heating process introduces negligible angular momentum. This paper proposes and evaluates a mechanism which resolves this apparent conflict. First, it is assumed that angular momentum transport in a tokamak is governed by a diffusion equation with a no-slip boundary condition at the plasma surface and with a torque-density source that is a function of radius. When the torque density source consists of two separated regions of positive and negative torque density, a non-zero central rotation velocity results, even when the total angular momentum input vanishes. Secondly, the authors show that localized ion-cyclotron heating can generate regions of positive and negative torque density and consequently central plasma rotation.

  18. Identification and control of plasma vertical position using neural network in Damavand tokamak

    NASA Astrophysics Data System (ADS)

    Rasouli, H.; Rasouli, C.; Koohi, A.

    2013-02-01

    In this work, a nonlinear model is introduced to determine the vertical position of the plasma column in Damavand tokamak. Using this model as a simulator, a nonlinear neural network controller has been designed. In the first stage, the electronic drive and sensory circuits of Damavand tokamak are modified. These circuits can control the vertical position of the plasma column inside the vacuum vessel. Since the vertical position of plasma is an unstable parameter, a direct closed loop system identification algorithm is performed. In the second stage, a nonlinear model is identified for plasma vertical position, based on the multilayer perceptron (MLP) neural network (NN) structure. Estimation of simulator parameters has been performed by back-propagation error algorithm using Levenberg-Marquardt gradient descent optimization technique. The model is verified through simulation of the whole closed loop system using both simulator and actual plant in similar conditions. As the final stage, a MLP neural network controller is designed for simulator model. In the last step, online training is performed to tune the controller parameters. Simulation results justify using of the NN controller for the actual plant.

  19. Superconducting magnet system for the TPX Tokamak

    SciTech Connect

    Hassenzahl, W.V.; Chaplin, M.R.; Heim, J.R.

    1993-09-15

    The Tokamak Physics Experiment (TPX) will be the first Tokamak using superconducting magnets for both the poloidal and toroidal field. It is designed for advanced Tokamak physics experiments in steady-state and long-pulse operation. The TPX superconducting magnets use an advanced cable-in-conduit conductor (CICC) design similar to that developed in support of the International Thermonuclear Experimental Reactor (ITER). The toroidal field magnets provide 4.0 T at 2.25 m with a stored energy of 1.05 GJ. The poloidal field magnets provide 18.0 V-s to ohmically start and control long burns of a 2.0 MA plasma.

  20. Investigation of lower hybrid wave coupling and current drive experiments at different configurations in experimental advanced superconducting tokamak

    NASA Astrophysics Data System (ADS)

    Ding, B. J.; Qin, Y. L.; Li, W. K.; Li, M. H.; Kong, E. H.; Zhang, L.; Ekedahl, A.; Peysson, Y.; Decker, J.; Wang, M.; Xu, H. D.; Hu, H. C.; Xu, G. S.; Shan, J. F.; Liu, F. K.; Zhao, Y. P.; Wan, B. N.; Li, J. G.; Group, EAST

    2011-08-01

    Using a 2 MW 2.45 GHz lower hybrid wave (LHW) system installed in experimental advanced superconducting tokamak, we have systematically carried out LHW-plasma coupling and lower hybrid current drive experiments in both divertor (double null and lower single null) and limiter plasma configuration with plasma current (Ip) ˜ 250 kA and central line averaged density (ne) ˜ 1.0-1.3 × 1019 m-3 recently. Results show that the reflection coefficient (RC) first is flat up to some distance between plasma and LHW grill, and then increases with the distance. Studies indicate that with the same plasma parameters, the best coupling is obtained in the limiter case (with plasma leaning on the inner wall), followed by the lower single null, and the one with the worst coupling is the double null configuration, explained by different magnetic connection length. The RCs in the different poloidal rows show that they have different coupling characteristics, possibly due to local magnetic connection length. Current drive efficiency has been investigated by a least squares fit with N//peak=2.1, where N//peak is the peak value of parallel refractive index of the launched wave. Results show that there is no obvious difference in the current drive efficiency between double null and lower single null cases, whereas the efficiency is somewhat small in the limiter configuration. This is in agreement with the ray tracing/Fokker-Planck code simulation by LUKE/C3PO and can be interpreted by the power spectrum up-shift factor in different plasma configurations. A transformer recharge is realized with ˜0.8 MW LHW power and the energy conversion efficiency from LHW to poloidal field energy is about 2%.

  1. Trapped Electron Mode Turbulence Driven Intrinsic Rotation in Tokamak Plasmas

    SciTech Connect

    Wang, W. X.; Hahm, T. S.; Ethier, S.; Zakharov, L. E.

    2011-02-07

    Recent progress from global gyrokinetic simulations in understanding the origin of intrinsic rotation in toroidal plasmas is reported with emphasis on electron thermal transport dominated regimes. The turbulence driven intrinsic torque associated with nonlinear residual stress generation by the fluctuation intensity and the intensity gradient in the presence of zonal flow shear induced asymmetry in the parallel wavenumber spectrum is shown to scale close to linearly with plasma gradients and the inverse of the plasma current. These results qualitatively reproduce empirical scalings of intrinsic rotation observed in various experiments. The origin of current scaling is found to be due to enhanced kll symmetry breaking induced by the increased radial variation of the safety factor as the current decreases. The physics origin for the linear dependence of intrinsic torque on pressure gradient is that both turbulence intensity and the zonal flow shear, which are two key ingredients for driving residual stress, increase with the strength of turbulence drive, which is R0/LTe and R0/Lne for the trapped electron mode. __________________________________________________

  2. Scattering of radio frequency waves by cylindrical density filaments in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Ram, Abhay K.; Hizanidis, Kyriakos

    2016-02-01

    In tokamak fusion plasmas, coherent fluctuations in the form of blobs or filaments are routinely observed in the scrape-off layer. Radio frequency (RF) electromagnetic waves, excited by antenna structures placed near the wall of a tokamak, have to propagate through the scrape-off layer before reaching the core of the plasma. While the effect of fluctuations on the properties of RF waves has not been quantified experimentally, it is of interest to carry out a theoretical study to determine if fluctuations can affect the propagation characteristics of RF waves. Usually, the difference between the plasma density inside the filament and the background plasma density is sizable, the ratio of the density difference to the background density being of order one. Generally, this precludes the use of geometrical optics in determining the effect of fluctuations, since the relevant ratio has to be much less than one, typically, of the order of 10% or less. In this paper, a full-wave, analytical model is developed for the scattering of a RF plane wave by a cylindrical plasma filament. It is assumed that the plasma inside and outside the filament is cold and uniform and that the major axis of the filament is aligned along the toroidal magnetic field. The ratio of the density inside the filament to the density of the background plasma is not restricted. The theoretical framework applies to the scattering of any cold plasma wave. In order to satisfy the boundary conditions at the interface between the filament and the background plasma, the electromagnetic fields inside and outside the filament need to have the same k∥ , the wave vector parallel to the ambient magnetic field, as the incident plane wave. Consequently, in contrast to the scattering of a RF wave by a spherical blob [Ram et al., Phys. Plasmas 20, 056110-1-056110-10 (2013)], the scattering by a field-aligned filament does not broaden the k∥ spectrum. However, the filament induces side-scattering leading to surface

  3. Mathematical models of plasma discharge control in a tokamak

    NASA Astrophysics Data System (ADS)

    Andreev, V. F.; Dnestrovskij, Yu. N.; Kostomarov, D. P.; Popov, A. M.

    A model for program description of discharge development in a tokomak is considered and the problem of optimal control of poloidal fields and total current in plasma is determined. A comparison of the formulated problem solution methods is performed. A quasi-optimal control model is proposed, allowing one to take account of real power supplies. Analysis of the control task stability and correctness is conducted. The numerical code for optimal control task solution is developed and the method is described. Different operation modes of the T-15 device are calculated using the developed code.

  4. Hamiltonian theory of the ion cyclotron minority heating dynamics in tokamak plasmas

    SciTech Connect

    Becoulet, A.; Gambier, D.J.; Samain, A. )

    1991-01-01

    The question of heating a tokamak plasma by means of electromagnetic waves in the ion cyclotron range of frequencies (ICRF) is considered in the perspective of large rf powers and in the low collisionality regime. In such a case, the quasilinear theory (QLT) is validated by the Hamiltonian dynamics of the wave--particle interaction which exceeds the threshold of the intrinsic stochasticity. The Hamiltonian dynamics is represented by the evolution of a set of three canonical action angle variables well adapted to the tokamak magnetic configuration. This approach allows derivation of the rf diffusion coefficient with very few assumptions. The distribution function of the resonant ions is written as a Fokker--Planck equation but the emphasis is put on the QL diffusion instead of on the usual diffusion induced by collisions. The Fokker--Planck equation is then given a variational form from which a solution is derived in the form of a semianalytical trial function of three parameters: the percentage of resonant particles contained in the tail, an isotropic width {Delta}{ital T}, and an anisotropic width {Delta}{ital P}. This solution is successfully tested against real experimental observations. It is shown that in the case of the JET tokamak (Plasma Phys. Controlled Fusion {bold 30}, 1467 (1988)) the distribution function is influenced by adiabatic barriers which in turn limit the Hamiltonian stochasticity domain within energy values typically in the MeV range. Consequently and for a given ICRF power, the tail energy excursion is lower and its concentration higher than that from a bounce-averaged prediction. This may actually be an advantage for machines like JET (Plasma Phys. Controlled Fusion {bold 30}, 1467 (1988)) considering the energy range required to simulate the {alpha}-particle behavior in a relevant fusion reactor.

  5. Hypersonic drift-tearing magnetic islands in tokamak plasmas

    SciTech Connect

    Fitzpatrick, R.; Waelbroeck, F. L.

    2007-12-15

    A two-fluid theory of long wavelength, hypersonic, drift-tearing magnetic islands in low-collisionality, low-{beta} plasmas possessing relatively weak magnetic shear is developed. The model assumes both slab geometry and cold ions, and neglects electron temperature and equilibrium current gradient effects. The problem is solved in three asymptotically matched regions. The 'inner region' contains the island. However, the island emits electrostatic drift-acoustic waves that propagate into the surrounding 'intermediate region', where they are absorbed by the plasma. Since the waves carry momentum, the inner region exerts a net force on the intermediate region, and vice versa, giving rise to strong velocity shear in the region immediately surrounding the island. The intermediate region is matched to the surrounding 'outer region', in which ideal magnetohydrodynamic holds. Isolated hypersonic islands propagate with a velocity that lies between those of the unperturbed local ion and electron fluids, but is much closer to the latter. The ion polarization current is stabilizing, and increases with increasing island width. Finally, the hypersonic branch of isolated island solutions ceases to exist above a certain critical island width. Hypersonic islands whose widths exceed the critical width are hypothesized to bifurcate to the so-called 'sonic' solution branch.

  6. Radial Localization of Toroidal Alfven Eigenmode in Tokamak Plasmas

    NASA Astrophysics Data System (ADS)

    Wang, Zhixuan; Lin, Zhihong; Heidbrink, William; Tobias, Benjamin; van Zeeland, Michael

    2013-10-01

    Toroidal Alfven eigenmode (TAE) with radially extended structures can be driven unstable by pressure gradients of energetic particles (EP). These unstable Alfveneigenmodes (AE) have been routinely observed in fusion experiments to induce a large EP transport, whichcould degrade overall plasma confinement and damagefusion devices.In the well-accepted paradigm, the growth rate of the AEs can be calculated from a perturbative EP contribution to a fixedmode structure and real frequency given by magnetohydrodynamic (MHD) properties of thermal plasmas. However, linear and nonlinear kinetic effects of both EP and thermal plasmasare important and should be treated on the same footing. The gyrokinetic simulation has thus emerged as anecessary and powerful tool for studying the linear andnonlinear dynamics of AEs. In the current work, the gyrokinetic toroidal code(GTC) linear simulation of the tokamakexperiment finds a radial localization of the TAE dueto the non-perturbative EP contribution. The EP-drivenTAE has a radial mode width much smaller than thatpredicted by the MHD theory. The TAE radial positionpeaks at and moves with the location of the strongest EPpressure gradients. Experimental data confirms that the eigenfunction drifts quicklyoutward radially. The non-perturbativeEP contribution also breaks the radial symmetry of the mode structure and induces a TAE frequency dependence on the toroidal mode number, in excellent agreement with the experimental measurements.

  7. Charge-exchange recombination spectroscopy of the plasma ion temperature at the T-10 tokamak

    SciTech Connect

    Krupin, V. A.; Tugarinov, S. N.; Barsukov, A. G.; Dnestrovskij, A. Yu.; Klyuchnikov, L. A.; Korobov, K. V.; Krasnyanskii, S. A.; Naumenko, N. N.; Nemets, A. R.; Sushkov, A. V.; Tilinin, G. N.

    2013-08-15

    Charge-exchange recombination spectroscopy (CXRS) based on a diagnostic neutral beam has been developed at the T-10 tokamak. The diagnostics allows one to measure the ion temperature profile in the cross section of the plasma column. In T-10 experiments, the measurement technique was adjusted and the elements of the CXRS diagnostics for ITER were tested. The used spectroscopic equipment makes it possible to reliably determine the ion temperature from the Doppler broadening of impurity lines (helium, carbon), as well as of the spectral lines of the working gas. The profiles of the plasma ion temperature in deuterium and helium discharges were measured at different plasma currents and densities, including with the use of active Doppler measurements of lines of different elements. The validity and reliability of ion temperature measurements performed by means of the developed CXRS diagnostics are analyzed.

  8. Hydrodynamic effects of eroded materials on response of plasma-facing component during a tokamak disruption

    SciTech Connect

    Hassanein, A.; Konkashbaev, I.

    1999-10-25

    Loss of plasma confinement causes surface and structural damage to plasma-facing materials (PFMs) and remains a major obstacle for tokamak reactors. The deposited plasma energy results in surface erosion and structural failure. The surface erosion consists of vaporization, spallation, and liquid splatter of metallic materials, while the structural damage includes large temperature increases in structural materials and at the interfaces between surface coatings and structural members. Comprehensive models (contained in the HEIGHTS computer simulation package) are being used self-consistently to evaluate material damage. Splashing mechanisms occur as a result of volume bubble boiling and liquid hydrodynamic instabilities and brittle destruction mechanisms of nonmelting materials. The effect of macroscopic erosion on total mass losses and lifetime is evaluated. The macroscopic erosion products may further protect PFMs from severe erosion (via the droplet-shielding effect) in a manner similar to that of the vapor shielding concept.

  9. New fluctuation phenomena in the H-mode regime of PDX tokamak plasmas

    SciTech Connect

    Slusher, R.E.; Surko, C.M.; Valley, J.F.; Crowley, T.; Mazzucato, E.; McGuire, K.

    1984-05-01

    A new kind of quasi-coherent fluctuation is observed near the edge of plasmas in the PDX tokamak during H-mode operation. (The H-mode occurs in neutral beam heated divertor plasmas and is characterized by improved energy containment as well as large density and temperature gradients near the plasma edge.) These fluctuations are evidenced as VUV and density fluctuation bursts at well-defined frequencies (..delta omega../..omega.. less than or equal to 0.1) in the frequency range between 50 and 180 kHz. They affect the edge temperature-density product, and therefore they may be important for understanding the relationship between the large edge density and temperature gradients and the improved energy confinement.

  10. Aspect Ratio Scaling of Ideal No-wall Stability Limits in High Bootstrap Fraction Tokamak Plasmas

    SciTech Connect

    J.E. Menard; M.G. Bell; R.E. Bell; D.A. Gates; S.M. Kaye; B.P. LeBlanc; R. Maingi; S.A. Sabbagh; V. Soukhanovskii; D. Stutman; the NSTX National Research Team

    2003-11-25

    Recent experiments in the low aspect ratio National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40 (2000) 557] have achieved normalized beta values twice the conventional tokamak limit at low internal inductance and with significant bootstrap current. These experimental results have motivated a computational re-examination of the plasma aspect ratio dependence of ideal no-wall magnetohydrodynamic stability limits. These calculations find that the profile-optimized no-wall stability limit in high bootstrap fraction regimes is well described by a nearly aspect ratio invariant normalized beta parameter utilizing the total magnetic field energy density inside the plasma. However, the scaling of normalized beta with internal inductance is found to be strongly aspect ratio dependent at sufficiently low aspect ratio. These calculations and detailed stability analyses of experimental equilibria indicate that the nonrotating plasma no-wall stability limit has been exceeded by as much as 30% in NSTX in a high bootstrap fraction regime.

  11. Heat diffusion across magnetic islands and ergodized plasma regions in realistic tokamak geometry

    SciTech Connect

    Hoelzl, M.; Guenter, S.

    2008-07-15

    Heat diffusion in magnetized plasmas is investigated numerically for tokamak geometry and realistic plasma parameters. Heat transport across single and overlapping magnetic islands is studied. As an application, the influence of an (n+1,m+1) helical perturbation onto the temperature perturbation caused by an (n,m) neoclassical tearing mode is examined. It is shown that the resulting ergodization of the magnetic field structure is able to reduce the resonant bootstrap current perturbation of a neoclassical tearing mode. This might explain the drop in the mode amplitude observed in the frequently interrupted regime. Furthermore, the influence of edge ergodization as generated by external perturbation coils onto the electron temperature is studied. It is shown that ergodization of the plasma boundary can decrease the pedestal temperature gradient significantly. This effect might be one element in the mitigation effects of edge-localized modes achieved by external resonant perturbation fields.

  12. Plasma edge transport with magnetic islands—a comparison between tokamak and reversed-field pinch

    NASA Astrophysics Data System (ADS)

    Ciaccio, G.; Schmitz, O.; Abdullaev, S. S.; Frerichs, H.; Agostini, M.; Scarin, P.; Spizzo, G.; Vianello, N.; White, R. B.

    2014-06-01

    In the reversed-field pinch (RFP) edge, measured transport and flows are strongly influenced by magnetic islands (Vianello 2013 Nucl. Fusion 53 073025). In fact, these islands determine a differential radial diffusion of electrons and ions which, interacting with the wall, give rise to a characteristic edge ambipolar potential. Such island structures also arise in tokamak plasmas, when resonant magnetic perturbations (RMPs) are applied for control of edge-localized modes. They impose a characteristic modulation to edge electron density and temperature fields, in close correlation with the local magnetic vacuum topology (Schmitz 2012 Nucl. Fusion 52 054001). In order to develop a generic picture of particle transport with magnetic islands located in the plasma edge between RFPs and tokamaks with RMP, test-particle transport simulations are done on TEXTOR with the same tool used in RFX-mod, namely, the guiding-centre code ORBIT (White and Chance 1984 Phys. Fluids 27 2455-67). A typical TEXTOR discharge in the (m, n) = (12, 4) configuration is reconstructed and analysed with ORBIT. We use Poincaré and connection length analysis of electrons and ion orbits to analyse the magnetic structure taking into account the different gyro-orbits of both constituents. Density distributions of test ions and electrons are calculated and used to obtain an initial estimate of the plasma potential and radial electric field around the island.

  13. Fusion reactivity, confinement, and stability of neutral-beam heated plasmas in TFTR and other tokamaks

    SciTech Connect

    Park, Hyeon, K.; Sabbagh, S.A.

    1996-05-01

    The hypothesis that the heating beam fueling profile shape connects the edge condition and improved core confinement and fusion reactivity is extensively studied on TFTR and applied to other tokamaks. The derived absolute scalings based on beam fueling profile shape for the stored energy and neutron yield can be applied to the deuterium discharges at different major radii in TFTR. These include Supershot, High poloidal beta, L-mode, and discharges with a reversed shear (RS) magnetic configuration. These scalings are also applied to deuterium-tritium discharges. The role of plasma parameters, such as plasma current, Isdo2(p), edge safety factor, qsdo5(a), and toroidal field, Bsdo2(T), in the performance and stability of the discharges is explicitly studied. Based on practical and externally controllable plasma parameters, the limitation and optimization of fusion power production of the present TFTR is investigated and a path for a discharge condition with fusion power gain, Q > 1 is suggested based on this study. Similar physics interpretation is provided for beam heated discharges on other major tokamaks.

  14. Power exhaust in the snowflake divertor for L- and H-mode TCV tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Vijvers, W. A. J.; Canal, G. P.; Labit, B.; Reimerdes, H.; Tal, B.; Coda, S.; De Temmerman, G. C.; Duval, B. P.; Morgan, T. W.; Zielinski, J. J.; the TCV Team

    2014-02-01

    The snowflake (SF) divertor is a plasma configuration that may enable tokamak operation at high performance and lower peak heat loads on the plasma-facing components than a standard single-null divertor. This paper reports on the results of experiments performed on the TCV tokamak in both the low- and high-confinement regimes, wherein the divertor configuration was continuously varied between a standard single-null and a ‘SF-plus’, which features auxiliary strike points (SPs) in the private flux region of the primary separatrix. The measured edge properties show that, in L-mode, the fraction of the exhaust power reaching the additional SPs is small. During edge-localized modes, up to ˜20% of the exhausted energy is redistributed to the additional SPs even at an x-point separation of 0.6 times the plasma minor radius, thereby reducing the peak heat flux to the inner primary SP by a factor of 2-3. The observed behaviour is qualitatively consistent with a proposed model for enhanced cross-field transport through the SF's relatively large region of low poloidal field by instability-driven convection.

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

    SciTech Connect

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

    2015-02-15

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

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

    PubMed

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

    2015-02-01

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

  17. Shaping of the plasma column in a small aspect ratio tokamak

    NASA Astrophysics Data System (ADS)

    Herrera, Julio; Arroyo, Ismael; Chavez, Esteban

    2015-11-01

    This is a follow-up to the work presented in last year's meeting, on the conceptual design of a small aspect ratio tokamak of variable configuration. The base parameters for this device would be similar to those in the START tokamak. The shaping of the plasma column is known to have important effects in the plasma performance, including the value of β, bootstrap currents, and intrinsic rotation. The main feature being explored here is the inclusion of independent control coils in the inboard and outboard sides; six in the first case, and up to seven in the latter. By varying the strength in their currents it is possible to achieve a wide variety of shapes: elliptical, conventional D-shape, inverse D-shape, and Bean-shape. As the control coils are activated, the strength of the toroidal magnetic field needs to he weakened, in order to keep reasonable values of the safety factor q . The study presented here is made by means of the 3D-MAPTOR code, which produces the Poincaré maps of the magnetic field lines, given the currents. For this purpose, a seed plasma current must be provided. All studies presented here assume equatorial symmetry, due to limitations in the code.

  18. Kinetic theory and simulation of multi-species plasmas in tokamaks excited with ICRF microwaves

    SciTech Connect

    Kerbel, G.D.; McCoy, M.G.

    1984-12-21

    This paper presents a description of a bounce-averaged Fokker-Planck quasilinear model for the kinetic description of tokamak plasmas. The non-linear collision and quasilinear resonant diffusion operators are represented in a form conducive to numerical solution with specific attention to the treatment of the boundary layer separating trapped and passing orbit regions of velocity space. The numerical techniques employed are detailed in so far as they constitute significant departure from those used in the conventional uniform magnetic field case. Examples are given to illustrate the combined effects of collisional and resonant diffusion.

  19. Geodesic acoustic modes in tokamak plasmas with a radial equilibrium electric field

    SciTech Connect

    Zhou, Deng

    2015-09-15

    The dispersion relation of geodesic acoustic modes in the tokamak plasma with an equilibrium radial electric field is derived and analyzed. Multiple branches of eigenmodes have been found, similar to the result given by the fluid model with a poloidal mass flow. Frequencies and damping rates of both the geodesic acoustic mode and the sound wave increase with respect to the strength of radial electric field, while the frequency and the damping rate of the lower frequency branch slightly decrease. Possible connection to the experimental observation is discussed.

  20. Effects of Magnetic Shear on Toroidal Rotation in Tokamak Plasmas with Lower Hybrid Current Drive

    NASA Astrophysics Data System (ADS)

    Rice, J. E.; Podpaly, Y. A.; Reinke, M. L.; Mumgaard, R.; Scott, S. D.; Shiraiwa, S.; Wallace, G. M.; Chouli, B.; Fenzi-Bonizec, C.; Nave, M. F. F.; Diamond, P. H.; Gao, C.; Granetz, R. S.; Hughes, J. W.; Parker, R. R.; Bonoli, P. T.; Delgado-Aparicio, L.; Eriksson, L.-G.; Giroud, C.; Greenwald, M. J.; Hubbard, A. E.; Hutchinson, I. H.; Irby, J. H.; Kirov, K.; Mailloux, J.; Marmar, E. S.; Wolfe, S. M.

    2013-09-01

    Application of lower hybrid (LH) current drive in tokamak plasmas can induce both co- and countercurrent directed changes in toroidal rotation, depending on the core q profile. For discharges with q0<1, rotation increments in the countercurrent direction are observed. If the LH-driven current is sufficient to suppress sawteeth and increase q0 above unity, the core toroidal rotation change is in the cocurrent direction. This change in sign of the rotation increment is consistent with a change in sign of the residual stress (the divergence of which constitutes an intrinsic torque that drives the flow) through its dependence on magnetic shear.

  1. The magnetic component of geodesic acoustic modes in tokamak plasmas with a radial equilibrium electric field

    NASA Astrophysics Data System (ADS)

    Zhou, Deng

    2016-10-01

    The dispersion relation of geodesic acoustic modes with a magnetic perturbation in the tokamak plasma with an equilibrium radial electric field was derived. The dispersion relation was analyzed for very low field strength. The mode frequency decreases with increasing field strength, which is different from the electrostatic geodesic acoustic mode. There exists an m = 1 magnetic component that is very low when the radial electric field is absent. The ratio between the m = 1 and m = 2 magnetic components increases with strength of the radial electric field for low Mach numbers.

  2. ASPECT: An advanced specified-profile evaluation code for tokamaks

    SciTech Connect

    Stotler, D.P.; Reiersen, W.T.; Bateman, G.

    1993-03-01

    A specified-profile, global analysis code has been developed to evaluate the performance of fusion reactor designs. Both steady-state and time-dependent calculations are carried out; the results of the former can be used in defining the parameters of the latter, if desired. In the steady-state analysis, the performance is computed at a density and temperature chosen to be consistent with input limits (e.g., density and beta) of several varieties. The calculation can be made at either the intersection of the two limits or at the point of optimum performance as the density and temperature are varied along the limiting boundaries. Two measures of performance are available for this purpose: the ignition margin or the confinement level required to achieve a prescribed ignition margin. The time-dependent calculation can be configured to yield either the evolution of plasma energy as a function of time or, via an iteration scheme, the amount of auxiliary power required to achieve a desired final plasma energy.

  3. Study on lower hybrid current drive efficiency at high density towards long-pulse regimes in Experimental Advanced Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Li, M. H.; Ding, B. J.; Zhang, J. Z.; Gan, K. F.; Wang, H. Q.; Peysson, Y.; Decker, J.; Zhang, L.; Wei, W.; Li, Y. C.; Wu, Z. G.; Ma, W. D.; Jia, H.; Chen, M.; Yang, Y.; Feng, J. Q.; Wang, M.; Xu, H. D.; Shan, J. F.; Liu, F. K.

    2014-06-01

    Significant progress on both L- and H-mode long-pulse discharges has been made recently in Experimental Advanced Superconducting Tokamak (EAST) with lower hybrid current drive (LHCD) [J. Li et al., Nature Phys. 9, 817 (2013) And B. N. Wan et al., Nucl. Fusion 53, 104006 (2013).]. In this paper, LHCD experiments at high density in L-mode plasmas have been investigated in order to explore possible methods of improving current drive (CD) efficiency, thus to extend the operational space in long-pulse and high performance plasma regime. It is observed that the normalized bremsstrahlung emission falls much more steeply than 1/ne_av (line-averaged density) above ne_av = 2.2 × 1019 m-3 indicating anomalous loss of CD efficiency. A large broadening of the operating line frequency (f = 2.45 GHz), measured by a radio frequency (RF) probe located outside the EAST vacuum vessel, is generally observed during high density cases, which is found to be one of the physical mechanisms resulting in the unfavorable CD efficiency. Collisional absorption of lower hybrid wave in the scrape off layer (SOL) may be another cause, but this assertion needs more experimental evidence and numerical analysis. It is found that plasmas with strong lithiation can improve CD efficiency largely, which should be benefited from the changes of edge parameters. In addition, several possible methods are proposed to recover good efficiency in future experiments for EAST.

  4. Tokamak Physics Experiment (TPX) power supply design and development

    SciTech Connect

    Neumeyer, C.; Bronner, G.; Lu, E.; Ramakrishnan, S.

    1995-04-01

    The Tokamak Physics Experiment (TPX) is an advanced tokamak project aimed at the production of quasi-steady state plasmas with advanced shape, heating, and particle control. TPX is to be built at the Princeton Plasma Physics Laboratory (PPPL) using many of the facilities from the Tokamak Fusion Test Reactor (TFTR). TPX will be the first tokamak to utilize superconducting (SC) magnets in both the toroidal field (TF) and poloidal field (PF) systems. This new feature requires a departure from the traditional tokamak power supply schemes. This paper describes the plan for the adaptation of the PPPL/FTR power system facilities to supply TPX. Five major areas are addressed, namely the AC power system, the TF, PF and Fast Plasma Position Control (FPPC) power supplies, and quench protection for the TF and PF systems. Special emphasis is placed on the development of new power supply and protection schemes.

  5. On the non-stiffness of edge transport in L-mode tokamak plasmas

    SciTech Connect

    Sauter, O.; Brunner, S.; Kim, D.; Merlo, G.; Behn, R.; Coda, S.; Duval, B. P.; Federspiel, L.; Goodman, T. P.; Karpushov, A.; Merle, A.; Team, TCV; Camenen, Y.

    2014-05-15

    Transport analyses using first-principle turbulence codes and 11/2 -D transport codes usually study radial transport properties between the tokamak plasma magnetic axis and a normalized minor radius around 0.8. In this region, heat transport shows significantly stiff properties resulting in temperature scalelength values (R∕L{sub T}) that are relatively independent of the level of the radial heat flux. We have studied experimentally in the tokamak à configuration variable [F. Hofmann et al., Plasma Phys. Controlled Fusion 36, B277 (1994)] the radial electron transport properties of the edge region, close to the last closed flux surface, namely, between ρ{sub V}=√(V/V{sub edge})=0.8 to 1. It is shown that electron transport is not stiff in this region and high R∕L{sub Te} values (∼20–40) can be attained even for L-mode confinement. We can define a “pedestal” location, already in L-mode regimes, where the transport characteristics change from constant logarithmic gradient, inside ρ{sub V} = 0.8, to constant gradient between 0.8 and 1.0. In particular, we demonstrate, with well resolved T{sub e} and n{sub e} profiles, that the confinement improvement with plasma current I{sub p}, with or without auxiliary heating, is due to this non-stiff edge region. This new result is used to explain the significant confinement improvement observed with negative triangularity, which could not be explained by theory to date. Preliminary local gyrokinetic simulations are now consistent with an edge, less stiff, region that is more sensitive to triangularity than further inside. We also show that increasing the electron cyclotron heating power increases the edge temperature inverse scalelength, in contrast to the value in the main plasma region. The dependence of confinement on density in ohmic plasmas is also studied and brings new insight in the understanding of the transition between linear and saturated confinement regimes, as well as of the density limit and

  6. Impurity behavior during sawtooth activity in tokamak plasmas

    SciTech Connect

    Nicolas, T.; Garbet, X.; Sabot, R.; Lütjens, H.; Luciani, J.-F.

    2014-01-15

    The transport of impurities by a sawtooth crash is simulated with the XTOR-2F code. Impurities are modeled as passive scalars, evolving in the compressible MHD flow inferred from the main MHD plasma. For a peaked impurity density profile, the non-linear kink flow of the sawtooth crash redistributes the profile efficiently and most of the particles in the peak inside the q = 1 surface are expelled. For an initially hollow impurity density profile, the crash leads to a significant penetration up to the magnetic axis. The results are compared with Kadomtsev's model. Despite essentially different mechanisms, the evolution of the particle content inside the q = 1 surface for Kadomtsev's model and for the non-linear case are virtually identical for the peaked profile, while the model slightly overestimates penetration for the hollow case.

  7. Runaway electron dynamics in tokamak plasmas with high impurity content

    SciTech Connect

    Martín-Solís, J. R.; Loarte, A.; Lehnen, M.

    2015-09-15

    The dynamics of high energy runaway electrons is analyzed for plasmas with high impurity content. It is shown that modified collision terms are required in order to account for the collisions of the relativistic runaway electrons with partially stripped impurity ions, including the effect of the collisions with free and bound electrons, as well as the scattering by the full nuclear and the electron-shielded ion charge. The effect of the impurities on the avalanche runaway growth rate is discussed. The results are applied, for illustration, to the interpretation of the runaway electron behavior during disruptions, where large amounts of impurities are expected, particularly during disruption mitigation by massive gas injection. The consequences for the electron synchrotron radiation losses and the resulting runaway electron dynamics are also analyzed.

  8. Topology of tokamak plasma equilibria with toroidal current reversal

    SciTech Connect

    Rodrigues, Paulo; Bizarro, Joao P. S.

    2012-01-15

    Some general principles about scalar functions with critical points are used to rigorously ascertain that magnetic equilibria with both toroidal current reversal and nested magnetic surfaces are atypical solutions and highly unstable to arbitrary perturbations of boundary conditions and other parameters. The cause for such is shown to lie in the condition of nested magnetic surfaces and not in the possibility of current reversal and consequent vanishing of the poloidal field inside the plasma. Rather than supporting the claim that instability against experimentally driven perturbations forbids configurations with toroidal current reversal, it is argued that these can be attained if an axisymmetric island system is allowed for in order to break the condition of nested magnetic surfaces. A number of results previously reported in the literature are discussed and reinterpreted under the proposed framework, providing some physical insight on the nature of equilibria with toroidal current reversal.

  9. Bifurcations of axisymmetric plasma equilibrium in a tokamak

    NASA Astrophysics Data System (ADS)

    Skovoroda, A. A.

    2016-05-01

    Bifurcation of solutions to the Grad-Shafranov-type equation for helically symmetric plasma near the threshold for tearing instability are analyzed. Quadratic and cubic nonlinearities were added to the linear dependence of the current density on the helical flux. Depending on the character of nonlinearity, two types of bifurcation can be observed, the "small" and the "large" ones. The small bifurcation is typical of cubic nonlinearity and reveals itself in the growth of the magnetic island from zero as the profile parameter increases above the instability threshold. The large bifurcation is typical of quadratic nonlinearity and causes jumplike formation of a large-scale magnetic island upon exceeding the instability threshold. As the profile parameter decreases below the instability threshold, the large-scale island continues to persist for some time (the hysteresis effect) and then suddenly disappears.

  10. Runaway electron dynamics in tokamak plasmas with high impurity content

    NASA Astrophysics Data System (ADS)

    Martín-Solís, J. R.; Loarte, A.; Lehnen, M.

    2015-09-01

    The dynamics of high energy runaway electrons is analyzed for plasmas with high impurity content. It is shown that modified collision terms are required in order to account for the collisions of the relativistic runaway electrons with partially stripped impurity ions, including the effect of the collisions with free and bound electrons, as well as the scattering by the full nuclear and the electron-shielded ion charge. The effect of the impurities on the avalanche runaway growth rate is discussed. The results are applied, for illustration, to the interpretation of the runaway electron behavior during disruptions, where large amounts of impurities are expected, particularly during disruption mitigation by massive gas injection. The consequences for the electron synchrotron radiation losses and the resulting runaway electron dynamics are also analyzed.

  11. A penalization technique to model plasma facing components in a tokamak with temperature variations

    NASA Astrophysics Data System (ADS)

    Paredes, A.; Bufferand, H.; Ciraolo, G.; Schwander, F.; Serre, E.; Ghendrih, P.; Tamain, P.

    2014-10-01

    To properly address turbulent transport in the edge plasma region of a tokamak, it is mandatory to describe the particle and heat outflow on wall components, using an accurate representation of the wall geometry. This is challenging for many plasma transport codes, which use a structured mesh with one coordinate aligned with magnetic surfaces. We propose here a penalization technique that allows modeling of particle and heat transport using such structured mesh, while also accounting for geometrically complex plasma-facing components. Solid obstacles are considered as particle and momentum sinks whereas ionic and electronic temperature gradients are imposed on both sides of the obstacles along the magnetic field direction using delta functions (Dirac). Solutions exhibit plasma velocities (M=1) and temperatures fluxes at the plasma-wall boundaries that match with boundary conditions usually implemented in fluid codes. Grid convergence and error estimates are found to be in agreement with theoretical results obtained for neutral fluid conservation equations. The capability of the penalization technique is illustrated by introducing the non-collisional plasma region expected by the kinetic theory in the immediate vicinity of the interface, that is impossible when considering fluid boundary conditions. Axisymmetric numerical simulations show the efficiency of the method to investigate the large-scale transport at the plasma edge including the separatrix and in realistic complex geometries while keeping a simple structured grid.

  12. Studies of Feedback Stabilization of Axisymmetric Modes in Deformable Tokamak Plasmas

    NASA Astrophysics Data System (ADS)

    Ward, David John

    A new linear MHD stability code, NOVA-W, is described and applied to the study of the feedback stabilization of the axisymmetric mode in deformable tokamak plasmas. The NOVA-W code is a modification of the non-variational MHD stability code NOVA^1 that includes the effects of resistive passive conductors and active feedback circuits. The vacuum calculation has been reformulated in terms of the perturbed poloidal flux to allow the inclusion of perturbed toroidal currents outside the plasma. The boundary condition at the plasma-vacuum interface relates the instability displacement to the perturbed poloidal flux. This allows a solution of the linear MHD stability equations with the feedback effects included. The code has been tested for the case of passive stabilization against a simplified analytic model and against a different numerical calculation for a realistic tokamak configuration. The comparisons demonstrate the accuracy of the NOVA-W results. The utility and performance of the NOVA-W code are demonstrated for calculations of varying configurations of passive conductors. Active feedback calculations are performed for the CIT tokamak design demonstrating the effect of varying the position of the flux loops which provide the measurements of vertical displacement. The results compare well to those of earlier calculations using a less efficient nonlinear code. The NOVA-W code is used to examine the effects of plasma deformability on feedback stabilization. It is seen that plasmas with shaped cross sections have unstable motion different from a rigid shift. Plasma equilibria with large triangularity show particularly significant deviations from a uniform rigid shift. Furthermore, the placement of passive conductors is shown to modify the non-rigid components of the motion in a way that reduces the stabilizing effects of these conductors. The eigenfunction is also modified under the effects of active feedback. This deformation is seen to depend strongly on the

  13. Isotope mass and charge effects in tokamak plasmas

    SciTech Connect

    Pusztai, I.; Candy, J.; Gohil, P.

    2011-12-15

    The effect of primary ion species of differing charge and mass - specifically, deuterium, hydrogen, and helium - on instabilities and transport is studied in DIII-D plasmas through gyrokinetic simulations with gyro [J. Candy and E. Belli, General Atomics Technical Report No. GA-A26818, 2010]. In linear simulations under imposed similarity of the profiles, there is an isomorphism between the linear growth rates of hydrogen isotopes, but the growth rates are higher for Z > 1 main ions due to the appearance of the charge in the Poisson equation. On ion scales the most significant effect of the different electron-to-ion mass ratio appears through collisions stabilizing trapped electron modes. In nonlinear simulations, significant favorable deviations from pure gyro-Bohm scaling are found due to electron-to-ion mass ratio effects and collisions. The presence of any non-trace impurity species cannot be neglected in a comprehensive simulation of the transport; including carbon impurity in the simulations caused a dramatic reduction of energy fluxes. The transport in the analyzed deuterium and helium discharges could be well reproduced in gyrokinetic and gyrofluid simulations while the significant hydrogen discrepancy is the subject of ongoing investigation.

  14. Isotope mass and charge effects in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Pusztai, I.; Candy, J.; Gohil, P.

    2011-12-01

    The effect of primary ion species of differing charge and mass—specifically, deuterium, hydrogen, and helium—on instabilities and transport is studied in DIII-D plasmas through gyrokinetic simulations with gyro [J. Candy and E. Belli, General Atomics Technical Report No. GA-A26818, 2010]. In linear simulations under imposed similarity of the profiles, there is an isomorphism between the linear growth rates of hydrogen isotopes, but the growth rates are higher for Z > 1 main ions due to the appearance of the charge in the Poisson equation. On ion scales the most significant effect of the different electron-to-ion mass ratio appears through collisions stabilizing trapped electron modes. In nonlinear simulations, significant favorable deviations from pure gyro-Bohm scaling are found due to electron-to-ion mass ratio effects and collisions. The presence of any non-trace impurity species cannot be neglected in a comprehensive simulation of the transport; including carbon impurity in the simulations caused a dramatic reduction of energy fluxes. The transport in the analyzed deuterium and helium discharges could be well reproduced in gyrokinetic and gyrofluid simulations while the significant hydrogen discrepancy is the subject of ongoing investigation.

  15. Advances in Langmuir probe diagnostics of the plasma potential and electron-energy distribution function in magnetized plasma

    NASA Astrophysics Data System (ADS)

    Popov, Tsv K.; Dimitrova, M.; Ivanova, P.; Kovačič, J.; Gyergyek, T.; Dejarnac, R.; Stöckel, J.; Pedrosa, M. A.; López-Bruna, D.; Hidalgo, C.

    2016-06-01

    Advanced Langmuir probe techniques for evaluating the plasma potential and electron-energy distribution function (EEDF) in magnetized plasma are reviewed. It is shown that when the magnetic field applied is very weak and the electrons reach the probe without collisions in the probe sheath the second-derivative Druyvesteyn formula can be used for EEDF evaluation. At low values of the magnetic field, an extended second-derivative Druyvesteyn formula yields reliable results, while at higher values of the magnetic field, the first-derivative probe technique is applicable for precise evaluation of the plasma potential and the EEDF. There is an interval of intermediate values of the magnetic field when both techniques—the extended second-derivative and the first-derivative one—can be used. Experimental results from probe measurements in different ranges of magnetic field are reviewed and discussed: low-pressure argon gas discharges in the presence of a magnetic field in the range from 0.01 to 0.08 T, probe measurements in circular hydrogen plasmas for high-temperature fusion (magnetic fields from 0.45 T to 1.3 T) in small ISTTOK and CASTOR tokamaks, D-shape COMPASS tokamak plasmas, as well as in the TJ-II stellarator. In the vicinity of the last closed flux surface (LCFS) in tokamaks and in the TJ-II stellarator, the EEDF obtained is found to be bi-Maxwellian, while close to the tokamak chamber wall it is Maxwellian. The mechanism of the appearance of a bi-Maxwellian EEDF in the vicinity of the LCFS is discussed. Comparison of the results from probe measurements with those obtained from calculations using the ASTRA and EIRENE codes shows that the main reason for the appearance of a bi-Maxwellian EEDF in the vicinity of the LCFS is the ionization of the neutral atoms.

  16. Theoretical and numerical studies of wave-packet propagation in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Lu, Z. X.; Zonca, F.; Cardinali, A.

    2012-04-01

    Theoretical and numerical studies of wave-packet propagation are presented to analyze the time varying 2D mode structures of electrostatic fluctuations in tokamak plasmas, using general flux coordinates. Instead of solving the 2D wave equations directly, the solution of the initial value problem is used to obtain the 2D mode structure, following the propagation of wave-packets generated by a source and reconstructing the time varying field. As application, the 2D WKB method is applied to investigate the shaping effects (elongation and triangularity) of tokamak geometry on the lower hybrid wave propagation and absorption. Meanwhile, the mode structure decomposition (MSD) method is used to handle the boundary conditions and simplify the 2D problem to two nested 1D problems. The MSD method is related to that discussed earlier by Zonca and Chen [Phys. Fluids B 5, 3668 (1993)] and reduces to the well-known "ballooning formalism" [J. W. Connor et al., Phys. Rev. Lett. 40, 396 (1978)], when spatial scale separation applies. This method is used to investigate the time varying 2D electrostatic ion temperature gradient (ITG) mode structure with a mixed WKB-full-wave technique. The time varying field pattern is reconstructed, and the time asymptotic structure of the wave-packet propagation gives the 2D eigenmode and the corresponding eigenvalue. As a general approach to investigate 2D mode structures in tokamak plasmas, our method also applies for electromagnetic waves with general source/sink terms either by an internal/external antenna or a nonlinear wave interaction with zonal structures.

  17. Performance of current measurement system in poloidal field power supply for Experimental Advanced Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Liu, D. M.; Li, J.; Wan, B. N.; Lu, Z.; Wang, L. S.; Jiang, L.; Lu, C. H.; Huang, J.

    2016-11-01

    As one of the core subsystems of the Experimental Advanced Superconducting Tokamak (EAST), the poloidal field power system supplies energy to EAST's superconducting coils. To measure the converter current in the poloidal field power system, a current measurement system has been designed. The proposed measurement system is composed of a Rogowski coil and a newly designed integrator. The results of the resistor-inductor-capacitor discharge test and the converter equal current test show that the current measurement system provides good reliability and stability, and the maximum error of the proposed system is less than 1%.

  18. Conceptual design of a fast-ion D-alpha diagnostic on experimental advanced superconducting tokamak

    SciTech Connect

    Huang, J. Wan, B.; Hu, L.; Hu, C.; Heidbrink, W. W.; Zhu, Y.; Hellermann, M. G. von; Gao, W.; Wu, C.; Li, Y.; Fu, J.; Lyu, B.; Yu, Y.; Ye, M.; Shi, Y.

    2014-11-15

    To investigate the fast ion behavior, a fast ion D-alpha (FIDA) diagnostic system has been planned and is presently under development on Experimental Advanced Superconducting Tokamak. The greatest challenges for the design of a FIDA diagnostic are its extremely low intensity levels, which are usually significantly below the continuum radiation level and several orders of magnitude below the bulk-ion thermal charge-exchange feature. Moreover, an overlaying Motional Stark Effect (MSE) feature in exactly the same wavelength range can interfere. The simulation of spectra code is used here to guide the design and evaluate the diagnostic performance. The details for the parameters of design and hardware are presented.

  19. Conceptual design of a fast-ion D-alpha diagnostic on experimental advanced superconducting tokamak

    NASA Astrophysics Data System (ADS)

    Huang, J.; Heidbrink, W. W.; Wan, B.; von Hellermann, M. G.; Zhu, Y.; Gao, W.; Wu, C.; Li, Y.; Fu, J.; Lyu, B.; Yu, Y.; Shi, Y.; Ye, M.; Hu, L.; Hu, C.

    2014-11-01

    To investigate the fast ion behavior, a fast ion D-alpha (FIDA) diagnostic system has been planned and is presently under development on Experimental Advanced Superconducting Tokamak. The greatest challenges for the design of a FIDA diagnostic are its extremely low intensity levels, which are usually significantly below the continuum radiation level and several orders of magnitude below the bulk-ion thermal charge-exchange feature. Moreover, an overlaying Motional Stark Effect (MSE) feature in exactly the same wavelength range can interfere. The simulation of spectra code is used here to guide the design and evaluate the diagnostic performance. The details for the parameters of design and hardware are presented.

  20. Conceptual design of a fast-ion D-alpha diagnostic on experimental advanced superconducting tokamak.

    PubMed

    Huang, J; Heidbrink, W W; Wan, B; von Hellermann, M G; Zhu, Y; Gao, W; Wu, C; Li, Y; Fu, J; Lyu, B; Yu, Y; Shi, Y; Ye, M; Hu, L; Hu, C

    2014-11-01

    To investigate the fast ion behavior, a fast ion D-alpha (FIDA) diagnostic system has been planned and is presently under development on Experimental Advanced Superconducting Tokamak. The greatest challenges for the design of a FIDA diagnostic are its extremely low intensity levels, which are usually significantly below the continuum radiation level and several orders of magnitude below the bulk-ion thermal charge-exchange feature. Moreover, an overlaying Motional Stark Effect (MSE) feature in exactly the same wavelength range can interfere. The simulation of spectra code is used here to guide the design and evaluate the diagnostic performance. The details for the parameters of design and hardware are presented.

  1. The National Spherical Tokamak Experiment at the Princeton Plasma Physics Laboratory

    SciTech Connect

    1995-12-01

    The Department of Energy (DOE) has prepared an Environmental Assessment (EA), DOE/EA-1108, evaluating the environmental effects of the proposed construction and operation of the National Spherical Tokamak Experiment (NSTX) within the existing C-Stellarator (CS) Building at the Princeton Plasma Physics Laboratory, Princeton, New Jersey. The purpose of the NSTX is to investigate the physics of spherically shaped plasmas as an alternative path to conventional tokamaks for development of fusion energy. Fusion energy has the potential to help compensate for dwindling supplies of fossil fuels and the eventual depletion of fissionable uranium used in present-day nuclear reactors. Construction of the NSTX in the CS Building would require the dismantling and removal of the existing unused Princeton Large Torus (PLT) device, part of which would be reused to construct the NSTX. Based on the analyses in the EA, the DOE has determined that the proposed action does not constitute a major federal action significantly affecting the quality of the human environment within the meaning of the National Environmental Policy Act (NEPA) of 1969, 42 U.S.C. 4,321 et seq. The preparation of an Environmental Impact Statement is not required. Thus, the DOE is issuing a FONSI pursuant to the Council on Environmental Quality regulations implementing NEPA (40 CFR Parts 1500--1508) and the DOE NEPA implementing regulations (10 CFR Part 1021).

  2. TEMPEST simulations of the plasma transport in a single-null tokamak geometry

    NASA Astrophysics Data System (ADS)

    Xu, X. Q.; Bodi, K.; Cohen, R. H.; Krasheninnikov, S.; Rognlien, T. D.

    2010-06-01

    We present edge kinetic ion transport simulations of tokamak plasmas in magnetic divertor geometry using the fully nonlinear (full-f) continuum code TEMPEST. Besides neoclassical transport, a term for divergence of anomalous kinetic radial flux is added to mock up the effect of turbulent transport. To study the relative roles of neoclassical and anomalous transport, TEMPEST simulations were carried out for plasma transport and flow dynamics in a single-null tokamak geometry, including the pedestal region that extends across the separatrix into the scrape-off layer and private flux region. A series of TEMPEST simulations were conducted to investigate the transition of midplane pedestal heat flux and flow from the neoclassical to the turbulent limit and the transition of divertor heat flux and flow from the kinetic to the fluid regime via an anomalous transport scan and a density scan. The TEMPEST simulation results demonstrate that turbulent transport (as modelled by large diffusion) plays a similar role to collisional decorrelation of particle orbits and that the large turbulent transport (large diffusion) leads to an apparent Maxwellianization of the particle distribution. We also show the transition of parallel heat flux and flow at the entrance to the divertor plates from the fluid to the kinetic regime. For an absorbing divertor plate boundary condition, a non-half-Maxwellian is found due to the balance between upstream radial anomalous transport and energetic ion endloss.

  3. TEMPEST Simulations of the Plasma Transport in a Single-Null Tokamak Geometry

    DOE PAGES

    X. Q. Xu; Bodi, K.; Cohen, R. H.; Krasheninnikov, S.; Rognlien, T. D.

    2010-05-28

    We present edge kinetic ion transport simulations of tokamak plasmas in magnetic divertor geometry using the fully nonlinear (full-f) continuum code TEMPEST. Besides neoclassical transport, a term for divergence of anomalous kinetic radial flux is added to mock up the effect of turbulent transport. In order to study the relative roles of neoclassical and anomalous transport, TEMPEST simulations were carried out for plasma transport and flow dynamics in a single-null tokamak geometry, including the pedestal region that extends across the separatrix into the scrape-off layer and private flux region. In a series of TEMPEST simulations were conducted to investigate themore » transition of midplane pedestal heat flux and flow from the neoclassical to the turbulent limit and the transition of divertor heat flux and flow from the kinetic to the fluid regime via an anomalous transport scan and a density scan. The TEMPEST simulation results demonstrate that turbulent transport (as modelled by large diffusion) plays a similar role to collisional decorrelation of particle orbits and that the large turbulent transport (large diffusion) leads to an apparent Maxwellianization of the particle distribution. Moreover, we show the transition of parallel heat flux and flow at the entrance to the divertor plates from the fluid to the kinetic regime. For an absorbing divertor plate boundary condition, a non-half-Maxwellian is found due to the balance between upstream radial anomalous transport and energetic ion endloss.« less

  4. TEMPEST Simulations of the Plasma Transport in a Single-Null Tokamak Geometry

    SciTech Connect

    X. Q. Xu; Bodi, K.; Cohen, R. H.; Krasheninnikov, S.; Rognlien, T. D.

    2010-05-28

    We present edge kinetic ion transport simulations of tokamak plasmas in magnetic divertor geometry using the fully nonlinear (full-f) continuum code TEMPEST. Besides neoclassical transport, a term for divergence of anomalous kinetic radial flux is added to mock up the effect of turbulent transport. In order to study the relative roles of neoclassical and anomalous transport, TEMPEST simulations were carried out for plasma transport and flow dynamics in a single-null tokamak geometry, including the pedestal region that extends across the separatrix into the scrape-off layer and private flux region. In a series of TEMPEST simulations were conducted to investigate the transition of midplane pedestal heat flux and flow from the neoclassical to the turbulent limit and the transition of divertor heat flux and flow from the kinetic to the fluid regime via an anomalous transport scan and a density scan. The TEMPEST simulation results demonstrate that turbulent transport (as modelled by large diffusion) plays a similar role to collisional decorrelation of particle orbits and that the large turbulent transport (large diffusion) leads to an apparent Maxwellianization of the particle distribution. Moreover, we show the transition of parallel heat flux and flow at the entrance to the divertor plates from the fluid to the kinetic regime. For an absorbing divertor plate boundary condition, a non-half-Maxwellian is found due to the balance between upstream radial anomalous transport and energetic ion endloss.

  5. Gyrokinetic simulations of electrostatic microinstabilities with bounce-averaged kinetic electrons for shaped tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Qi, Lei; Kwon, Jaemin; Hahm, T. S.; Jo, Gahyung

    2016-06-01

    Nonlinear bounce-averaged kinetic theory [B. H. Fong and T. S. Hahm, Phys. Plasmas 6, 188 (1999)] is used for magnetically trapped electron dynamics for the purpose of achieving efficient gyrokinetic simulations of Trapped Electron Mode (TEM) and Ion Temperature Gradient mode with trapped electrons (ITG-TEM) in shaped tokamak plasmas. The bounce-averaged kinetic equations are explicitly extended to shaped plasma equilibria from the previous ones for concentric circular plasmas, and implemented to a global nonlinear gyrokinetic code, Gyro-Kinetic Plasma Simulation Program (gKPSP) [J. M. Kwon et al., Nucl. Fusion 52, 013004 (2012)]. Verification of gKPSP with the bounce-averaged kinetic trapped electrons in shaped plasmas is successfully carried out for linear properties of the ITG-TEM mode and Rosenbluth-Hinton residual zonal flow [M. N. Rosenbluth and F. L. Hinton, Phys. Rev. Lett. 80, 724 (1998)]. Physics responsible for stabilizing effects of elongation on both ITG mode and TEM is identified using global gKPSP simulations. These can be understood in terms of magnetic flux expansion, leading to the effective temperature gradient R / L T ( 1 - E ') [P. Angelino et al., Phys. Rev. Lett. 102, 195002 (2009)] and poloidal wave length contraction at low field side, resulting in the effective poloidal wave number kθρi/κ.

  6. Plasma current start-up using the lower hybrid wave on the TST-2 spherical tokamak

    NASA Astrophysics Data System (ADS)

    Takase, Y.; Ejiri, A.; Inada, T.; Moeller, C. P.; Shinya, T.; Tsujii, N.; Yajima, S.; Furui, H.; Homma, H.; Imamura, K.; Nakamura, K.; Nakamura, K.; Sonehara, M.; Takeuchi, T.; Togashi, H.; Tsuda, S.; Yoshida, Y.

    2015-12-01

    Non-inductive plasma current start-up, ramp-up and sustainment by waves in the lower hybrid wave (LHW) frequency range at 200 MHz were investigated on the TST-2 spherical tokamak (R0 ≤ 0.38 m, a ≤ 0.25 m, Bt0 ≤ 0.3T, Ip ≤ 0.14 MA). Experimental results obtained using three types of antenna were compared. Both the highest plasma current (Ip = 18 kA) and the highest current drive figure of merit ηCD≡n¯eIpR0/PRF=1.4 ×1017 A/W/m2 were achieved using the capacitively-coupled combline (CCC) antenna, designed to excite the LHW with a sharp and highly directional wavenumber spectrum. For Ip greater than about 5 kA, high energy electrons accelerated by the LHW become the dominant carrier of plasma current. The low value of ηCD observed so far are believed to be caused by a rapid loss of energetic electrons and parasitic losses of the LHW energy in the plasma periphery. ηCD is expected to improve by an order of magnitude by increasing the plasma current to improve energetic electron confinement. In addition, edge power losses are expected to be reduced by increasing the toroidal magnetic field to improve wave accessibility to the plasma core, and by launching the LHW from the inboard upper region of the torus to achieve better single-pass absorption.

  7. Ideal plasma response to vacuum magnetic fields with resonant magnetic perturbations in non-axisymmetric tokamaks

    DOE PAGES

    Kim, Kimin; Ahn, J. -W.; Scotti, F.; Park, J. -K.; Menard, J. E.

    2015-09-03

    Ideal plasma shielding and amplification of resonant magnetic perturbations in non-axisymmetric tokamak is presented by field line tracing simulation with full ideal plasma response, compared to measurements of divertor lobe structures. Magnetic field line tracing simulations in NSTX with toroidal non-axisymmetry indicate the ideal plasma response can significantly shield/amplify and phase shift the vacuum resonant magnetic perturbations. Ideal plasma shielding for n = 3 mode is found to prevent magnetic islands from opening as consistently shown in the field line connection length profile and magnetic footprints on the divertor target. It is also found that the ideal plasma shielding modifiesmore » the degree of stochasticity but does not change the overall helical lobe structures of the vacuum field for n = 3. Furthermore, amplification of vacuum fields by the ideal plasma response is predicted for low toroidal mode n = 1, better reproducing measurements of strong striation of the field lines on the divertor plate in NSTX.« less

  8. A penalization technique to model plasma facing components in a tokamak with temperature variations

    SciTech Connect

    Paredes, A.; Bufferand, H.; Ciraolo, G.; Schwander, F.; Serre, E.; Ghendrih, P.; Tamain, P.

    2014-10-01

    To properly address turbulent transport in the edge plasma region of a tokamak, it is mandatory to describe the particle and heat outflow on wall components, using an accurate representation of the wall geometry. This is challenging for many plasma transport codes, which use a structured mesh with one coordinate aligned with magnetic surfaces. We propose here a penalization technique that allows modeling of particle and heat transport using such structured mesh, while also accounting for geometrically complex plasma-facing components. Solid obstacles are considered as particle and momentum sinks whereas ionic and electronic temperature gradients are imposed on both sides of the obstacles along the magnetic field direction using delta functions (Dirac). Solutions exhibit plasma velocities (M=1) and temperatures fluxes at the plasma–wall boundaries that match with boundary conditions usually implemented in fluid codes. Grid convergence and error estimates are found to be in agreement with theoretical results obtained for neutral fluid conservation equations. The capability of the penalization technique is illustrated by introducing the non-collisional plasma region expected by the kinetic theory in the immediate vicinity of the interface, that is impossible when considering fluid boundary conditions. Axisymmetric numerical simulations show the efficiency of the method to investigate the large-scale transport at the plasma edge including the separatrix and in realistic complex geometries while keeping a simple structured grid.

  9. Application of poloidal beta and plasma internal inductance in determination of input power time of Damavand tokamak

    NASA Astrophysics Data System (ADS)

    Noori, Ehsanallah; Sadeghi, Yahya; Ghoranneviss, Mahmood

    2016-10-01

    In this study, magnetic measurement of poloidal fields were used to determine poloidal beta and plasma internal inductance of Damavand tokamak combination of poloidal beta and plasma internal inductance (β _p+{l_i}/{2} ), known as Shafranov parameter, was obtained experimentally in terms of normal and tangential components of the magnetic field. Plasma internal inductance and poloidal beta were obtained using parametrization method based on analytical solution of Grad-Shafranov equation (GSE) and compared with parabolic-like profile of toroidal current density approach for determination of the plasma internal inductance. Finding evolution of β _p+{l_i}/{2} and plasma internal inductance. Finding poloidal beta (Shafranov parameter and internal inductance) and using energy balance equation, thermal energy and energy confinement were determined qualitatively in terms of poloidal beta during a regular discharge of Damavand tokamak.

  10. Radial profile measurements of plasma pressure-like fluctuations with the heavy ion beam diagnostic on the tokamak ISTTOK

    SciTech Connect

    Henriques, R. B. Malaquias, A.; Nedzelskiy, I. S.; Silva, C.; Coelho, R.; Figueiredo, H.; Fernandes, H.

    2014-11-15

    The Heavy Ion Beam Diagnostic (HIBD) on the tokamak ISTTOK (Instituto Superior Técnico TOKamak) has been modified, in terms of signal conditioning, to measure the local fluctuations of the n{sub e}σ{sub 1,2}(T{sub e}) product (plasma density times the effective ionization cross-section) along the tokamak minor diameter, in 12 sample volumes in the range of −0.7a < r < 0.7a, with a maximum delay time of 1 μs. The corresponding signals show high correlation with the magnetic Mirnov coils in the characteristic MHD frequency range of ISTTOK plasmas and enable the identification of tearing modes. This paper describes the HIBD signal conditioning system and presents a preliminary analysis of the radial profile measurements of local n{sub e}σ{sub 1,2}(T{sub e}) fluctuations.

  11. Radial profile measurements of plasma pressure-like fluctuations with the heavy ion beam diagnostic on the tokamak ISTTOK.

    PubMed

    Henriques, R B; Malaquias, A; Nedzelskiy, I S; Silva, C; Coelho, R; Figueiredo, H; Fernandes, H

    2014-11-01

    The Heavy Ion Beam Diagnostic (HIBD) on the tokamak ISTTOK (Instituto Superior Técnico TOKamak) has been modified, in terms of signal conditioning, to measure the local fluctuations of the neσ1,2(Te) product (plasma density times the effective ionization cross-section) along the tokamak minor diameter, in 12 sample volumes in the range of -0.7a < r < 0.7a, with a maximum delay time of 1 μs. The corresponding signals show high correlation with the magnetic Mirnov coils in the characteristic MHD frequency range of ISTTOK plasmas and enable the identification of tearing modes. This paper describes the HIBD signal conditioning system and presents a preliminary analysis of the radial profile measurements of local neσ1,2(Te) fluctuations.

  12. Feedback stabilization of the axisymmetric instability of a deformable tokamak plasma

    SciTech Connect

    Pomphrey, N.; Jardin, S.C.

    1987-09-01

    We analyze the magnetohydrodynamic (MHD) stability of the axisymmetric system consisting of a free boundary, non-circular cross-section tokamak plasma, finite resistivity passive conductors, and an active feedback system with magnetic flux pickup loops, a proportional amplifier with gain G, and current carrying poloidal field coils. Numerical simulation of a system that is unstable with G = 0 shows that for some placements of the pickup loops, the system will remain unstable for all values of G, while for other placements of the loops, the system will be stable for G > G/sub crit/. This behavior is explained by analysis using an extended energy principle, and it is shown to result from the deformability of the plasma cross section. 9 refs., 5 figs.

  13. Particle pinch and collisionality in gyrokinetic simulations of tokamak plasma turbulence

    SciTech Connect

    Angioni, C.; Candy, J.; Waltz, R. E.; Fable, E.; Maslov, M.; Weisen, H.; Peeters, A. G.

    2009-06-15

    The generic problem of how, in a turbulent plasma, the experimentally relevant conditions of a particle flux very close to the null are achieved, despite the presence of strong heat fluxes, is addressed. Nonlinear gyrokinetic simulations of plasma turbulence in tokamaks reveal a complex dependence of the particle flux as a function of the turbulent spatial scale and of the velocity space as collisionality is increased. At experimental values of collisionality, the particle flux is found close to the null, in agreement with the experiment, due to the balance between inward and outward contributions at small and large scales, respectively. These simulations provide full theoretical support to the prediction of a peaked density profile in a future nuclear fusion reactor.

  14. Generation of a magnetic island by edge turbulence in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Poyé, A.; Agullo, O.; Muraglia, M.; Garbet, X.; Benkadda, S.; Sen, A.; Dubuit, N.

    2015-03-01

    We investigate, through extensive 3D magneto-hydro-dynamics numerical simulations, the nonlinear excitation of a large scale magnetic island and its dynamical properties due to the presence of small-scale turbulence. Turbulence is induced by a steep pressure gradient in the edge region [B. D. Scott, Plasma Phys. Controlled Fusion 49, S25 (2007)], close to the separatrix in tokamaks where there is an X-point magnetic configuration. We find that quasi-resonant localized interchange modes at the plasma edge can beat together and produce extended modes that transfer energy to the lowest order resonant surface in an inner stable zone and induce a seed magnetic island. The island width displays high frequency fluctuations that are associated with the fluctuating nature of the energy transfer process from the turbulence, while its mean size is controlled by the magnetic energy content of the turbulence.

  15. Functional form for plasma velocity in a rapidly rotating tokamak discharge

    SciTech Connect

    Burrell, K. H.; Chrystal, C.

    2014-07-15

    A recently developed technique using charge exchange spectroscopy determines the ion poloidal rotation in tokamak plasmas from the poloidal variation in the toroidal angular rotation speed. The basis for this technique is the functional form for the plasma velocity calculated from the equilibrium equations. The initial development of this technique utilized the functional form determined for conditions where the ion toroidal rotation speed is much smaller than the ion thermal speed. There are cases, however, where the toroidal rotation can be comparable to the ion thermal speed, especially for high atomic number impurities. The present paper extends the previous analysis to this high rotation speed case and demonstrates how to extract the poloidal rotation speed from measurements of the toroidal angular rotation speed at two points on a flux surface.

  16. Generation of a magnetic island by edge turbulence in tokamak plasmas

    SciTech Connect

    Poyé, A.; Agullo, O.; Muraglia, M.; Benkadda, S.; Dubuit, N.; Garbet, X.; Sen, A.

    2015-03-15

    We investigate, through extensive 3D magneto-hydro-dynamics numerical simulations, the nonlinear excitation of a large scale magnetic island and its dynamical properties due to the presence of small-scale turbulence. Turbulence is induced by a steep pressure gradient in the edge region [B. D. Scott, Plasma Phys. Controlled Fusion 49, S25 (2007)], close to the separatrix in tokamaks where there is an X-point magnetic configuration. We find that quasi-resonant localized interchange modes at the plasma edge can beat together and produce extended modes that transfer energy to the lowest order resonant surface in an inner stable zone and induce a seed magnetic island. The island width displays high frequency fluctuations that are associated with the fluctuating nature of the energy transfer process from the turbulence, while its mean size is controlled by the magnetic energy content of the turbulence.

  17. Plasma radiometry with 30 chord resolution for fast transients in the DIII-D tokamak

    SciTech Connect

    Gray, D.S.; Hollmann, E.M.; Luckhardt, S.C.; Chalfant, J.; Chousal, L.; Hernandez, R.; Jones, E.; Kellman, A.G.

    2004-10-01

    A diagnostic capable of providing time resolved measurements of plasma radiated power during disruptions and other fast transients, e.g., edge localized modes has been employed in the DIII-D tokamak. The radiation is detected with absolute extreme ultraviolet (AXUV) photodiode arrays. Thirty chords from a single port provide measurements from a full slice of the plasma at one toroidal location. The analog bandwidth is up to 1 MHz for the brightest events, i.e., disruptions. Active cooling of the diode arrays prevents damage during high temperature vessel baking. Effective responsivity values of 0.12-0.18 A/W are taken from previous work on the application of AXUV diodes in DIII-D. The total radiated energy in disruptions typically agrees with bolometer measurements within about 12%.

  18. Measurement of the edge plasma rotation on J-TEXT tokamak

    SciTech Connect

    Cheng, Z. F.; Luo, J.; Wang, Z. J.; Zhang, Z. P.; Zhang, X. L.; Hou, S. Y.; Cheng, C.; Zhuang, G.

    2013-07-15

    A multi-channel high resolution spectrometer was developed for the measurement of the edge plasma rotation on J-TEXT tokamak. With the design of two opposite viewing directions, the poloidal and toroidal rotations can be measured simultaneously, and velocity accuracy is up to 1 km/s. The photon flux was enhanced by utilizing combined optical fiber. With this design, the time resolution reaches 3 ms. An assistant software “Spectra Assist” was developed for implementing the spectrometer control and data analysis automatically. A multi-channel monochromatic analyzer is designed to get the location of chosen ions simultaneously through the inversion analysis. Some preliminary experimental results about influence of plasma density, different magnetohydrodynamics behaviors, and applying of biased electrode are presented.

  19. Shielding of External Magnetic Perturbations By Torque In Rotating Tokamak Plasmas

    SciTech Connect

    Park, Jong-Kyu; Boozer, Allen H.; Menard, Jonathan E.; Gerhardt, Stefan P.; Sabbagh, Steve A.

    2009-08-24

    The imposition of a nonaxisymmetric magnetic perturbation on a rotating tokamak plasma requires energy and toroidal torque. Fundamental electrodynamics implies that the torque is essentially limited and must be consistent with the external response of a plasma equilibrium ƒ = j x B. Here magnetic measurements on National Spherical Torus eXperiment (NSTX) device are used to derive the energy and the torque, and these empirical evaluations are compared with theoretical calculations based on perturbed scalar pressure equilibria ƒ = ∇p coupled with the theory of nonambipolar transport. The measurement and the theory are consistent within acceptable uncertainties, but can be largely inconsistent when the torque is comparable to the energy. This is expected since the currents associated with the torque are ignored in scalar pressure equilibria, but these currents tend to shield the perturbation.

  20. Intense geodesic acousticlike modes driven by suprathermal ions in a tokamak plasma.

    PubMed

    Nazikian, R; Fu, G Y; Austin, M E; Berk, H L; Budny, R V; Gorelenkov, N N; Heidbrink, W W; Holcomb, C T; Kramer, G J; McKee, G R; Makowski, M A; Solomon, W M; Shafer, M; Strait, E J; Zeeland, M A Van

    2008-10-31

    Intense axisymmetric oscillations driven by suprathermal ions injected in the direction counter to the toroidal plasma current are observed in the DIII-D tokamak. The modes appear at nearly half the ideal geodesic acoustic mode frequency, in plasmas with comparable electron and ion temperatures and elevated magnetic safety factor (q_{min}>or=2). Strong bursting and frequency chirping are observed, concomitant with large (10%-15%) drops in the neutron emission. Large electron density fluctuations (n[over ]_{e}/n_{e} approximately 1.5%) are observed with no detectable electron temperature fluctuations, confirming a dominant compressional contribution to the pressure perturbation as predicted by kinetic theory. The observed mode frequency is consistent with a recent theoretical prediction for the energetic-particle-driven geodesic acoustic mode.

  1. Intense Geodesic Acousticlike Modes Driven by Suprathermal Ions in a Tokamak Plasma

    SciTech Connect

    Nazikian, R.; Fu, G. Y.; Budny, R. V.; Gorelenkov, N. N.; Kramer, G. J.; Solomon, W. M.; Austin, M. E.; Berk, H. L.; Heidbrink, W. W.; Holcomb, C. T.; Makowski, M. A.; McKee, G. R.; Shafer, M.; Strait, E. J.; Van Zeeland, M. A.

    2008-10-31

    Intense axisymmetric oscillations driven by suprathermal ions injected in the direction counter to the toroidal plasma current are observed in the DIII-D tokamak. The modes appear at nearly half the ideal geodesic acoustic mode frequency, in plasmas with comparable electron and ion temperatures and elevated magnetic safety factor (q{sub min}{>=}2). Strong bursting and frequency chirping are observed, concomitant with large (10%-15%) drops in the neutron emission. Large electron density fluctuations (n-tilde{sub e}/n{sub e}{approx_equal}1.5%) are observed with no detectable electron temperature fluctuations, confirming a dominant compressional contribution to the pressure perturbation as predicted by kinetic theory. The observed mode frequency is consistent with a recent theoretical prediction for the energetic-particle-driven geodesic acoustic mode.

  2. Measurement of sheared flows in the edge plasma of the CASTOR tokamak

    SciTech Connect

    Brotankova, J.; Stockel, J.; Seidl, J.; Duran, I.; Hron, M.

    2009-11-15

    The ion saturation current and floating potential are measured with high temporal (1 {mu}s) and spatial (2.5 mm) resolutions at the plasma edge of the CASTOR tokamak by two poloidally spaced radial arrays of Langmuir probes. The radial electric field and the phase velocity of plasma fluctuations are estimated. The position of the velocity shear layer (VSL) is localized with a high precision. The shearing rate {omega}{sub ExB} determined and found to be comparable with the inverse of the correlation time of fluctuations 1/{tau}{sub ac} outside the VSL and about five times higher in the proximity of the VSL. A small impact of the shear on fluctuation level at the VSL is observed also in the statistic parameters of the U{sub fl} and I{sub sat}.

  3. Multidirectional plasma flow measurement by Gundestrup Probe in scrape-off layer of ADITYA tokamak

    SciTech Connect

    Sangwan, Deepak; Jha, Ratneshwar; Tanna, Rakesh L.

    2015-11-15

    Multidirectional plasma flow measurements by using Gundestrup Probe in the scrape-off layer of ADITYA tokamak are presented. The ADITYA Gundestrup Probe-head consists of eight plates arranged around the ceramic rod and three pins normal to side plates. Plates are used to measure both parallel and perpendicular flows simultaneously and pins are used to measure plasma density and floating potential. A comparison of direct perpendicular flow measurement and by two other plates of Gundestrup Probe is presented. Possible causes of perpendicular flows are identified and compared with the measured flows. It is observed that the mechanism of the parallel flow and the perpendicular flow is different only at high parallel Mach number. A puff of the working gas is used to study its effect on the perpendicular flows and its reversal with the gas puff is observed.

  4. Recent Advancements in Microwave Imaging Plasma Diagnostics

    SciTech Connect

    H. Park; C.C. Chang; B.H. Deng; C.W. Domier; A.J.H. Donni; K. Kawahata; C. Liang; X.P. Liang; H.J. Lu; N.C. Luhmann, Jr.; A. Mase; H. Matsuura; E. Mazzucato; A. Miura; K. Mizuno; T. Munsat; K. and Y. Nagayama; M.J. van de Pol; J. Wang; Z.G. Xia; W-K. Zhang

    2002-03-26

    Significant advances in microwave and millimeter wave technology over the past decade have enabled the development of a new generation of imaging diagnostics for current and envisioned magnetic fusion devices. Prominent among these are revolutionary microwave electron cyclotron emission imaging (ECEI), microwave phase imaging interferometers, imaging microwave scattering and microwave imaging reflectometer (MIR) systems for imaging electron temperature and electron density fluctuations (both turbulent and coherent) and profiles (including transport barriers) on toroidal devices such as tokamaks, spherical tori, and stellarators. The diagnostic technology is reviewed, and typical diagnostic systems are analyzed. Representative experimental results obtained with these novel diagnostic systems are also presented.

  5. Collisionless current generation in the center of the tokamak plasma by an isotropic source of {alpha}-particles

    SciTech Connect

    Ilgisonis, V. I.; Sorokina, E. A.; Yurchenko, E. I.

    2010-01-15

    The density of the noninductive current generated due to collisionless motion of {alpha}-particles in the tokamak magnetic field is calculated. The analysis is based on fully three-dimensional calculations of charged particle trajectories without simplifying assumptions typical for drift and neoclassical approaches. The current is calculated over the entire cross section of the plasma column, including the magnetic axis. It is shown that the current density is not a function of a magnetic surface and is strongly polarized over the poloidal angle. The current density distribution in the tokamak poloidal cross section is obtained, and the current density as a function of the safety factor, the tokamak aspect ratio, and the ratio of the particle Larmor radius on the axis to the tokamak minor radius is determined. It is shown that, when the source of {alpha}-particles is spatially nonuniform, the current density in the center of the tokamak is nonzero due to asymmetry of the phase-space boundary between trapped and passing particles. The current density scaling in the tokamak center differs from the known approximations for the bootstrap current and is sensitive to the spatial distribution of {alpha}-particles.

  6. Effect of the plasma shapes on intrinsic rotation due to collisionless ion orbit loss in the tokamak edge plasmas

    SciTech Connect

    Ou, Jing; Wu, Guojiang; Li, Xinxia

    2014-07-15

    Distribution of the intrinsic rotation due to collisionless ion orbit loss near the tokamak edge region is studied by using an analytical model based on ion guiding center orbit approximation. A peak of the averaged ion orbit loss momentum fraction is found very near inside the separatrix region in a double null divertor configuration but is not found inside the last closed flux surface region in an outer limiter configuration. For the double null divertor configuration, the intrinsic rotation due to ion orbit loss depends on the plasma shape. With the increase in elongation and triangularity, the peak of the averaged ion orbit loss momentum fraction increases and it moves inward for the lower plasma current.

  7. Evidence for the Importance of Trapped Particle Resonances for Resistive Wall Mode Stability in High Beta Tokamak Plasmas

    SciTech Connect

    Reimerdes, H.; Berkery, J. W.; Lanctot, M. J.; Sabbagh, S. A.; Garofalo, A. M.; Strait, E. J.; Hanson, J. M.; In, Y.; Okabayashi, M.

    2011-05-27

    Active measurements of the plasma stability in tokamak plasmas reveal the importance of kinetic resonances for resistive wall mode stability. The rotation dependence of the magnetic plasma response to externally applied quasistatic n=1 magnetic fields clearly shows the signatures of an interaction between the resistive wall mode and the precession and bounce motions of trapped thermal ions, as predicted by a perturbative model of plasma stability including kinetic effects. The identification of the stabilization mechanism is an essential step towards quantitative predictions for the prospects of ''passive'' resistive wall mode stabilization, i.e., without the use of an ''active'' feedback system, in fusion-alpha heated plasmas.

  8. Multi-machine scaling of the main SOL parallel heat flux width in tokamak limiter plasmas

    NASA Astrophysics Data System (ADS)

    Horacek, J.; Pitts, R. A.; Adamek, J.; Arnoux, G.; Bak, J.-G.; Brezinsek, S.; Dimitrova, M.; Goldston, R. J.; Gunn, J. P.; Havlicek, J.; Hong, S.-H.; Janky, F.; LaBombard, B.; Marsen, S.; Maddaluno, G.; Nie, L.; Pericoli, V.; Popov, Tsv; Panek, R.; Rudakov, D.; Seidl, J.; Seo, D. S.; Shimada, M.; Silva, C.; Stangeby, P. C.; Viola, B.; Vondracek, P.; Wang, H.; Xu, G. S.; Xu, Y.; Contributors, JET

    2016-07-01

    As in many of today’s tokamaks, plasma start-up in ITER will be performed in limiter configuration on either the inner or outer midplane first wall (FW). The massive, beryllium armored ITER FW panels are toroidally shaped to protect panel-to-panel misalignments, increasing the deposited power flux density compared with a purely cylindrical surface. The chosen shaping should thus be optimized for a given radial profile of parallel heat flux, {{q}||} in the scrape-off layer (SOL) to ensure optimal power spreading. For plasmas limited on the outer wall in tokamaks, this profile is commonly observed to decay exponentially as {{q}||}={{q}0}\\text{exp} ~≤ft(-r/λ q\\text{omp}\\right) , or, for inner wall limiter plasmas with the double exponential decay comprising a sharp near-SOL feature and a broader main SOL width, λ q\\text{omp} . The initial choice of λ q\\text{omp} , which is critical in ensuring that current ramp-up or down will be possible as planned in the ITER scenario design, was made on the basis of an extremely restricted L-mode divertor dataset, using infra-red thermography measurements on the outer divertor target to extrapolate to a heat flux width at the main plasma midplane. This unsatisfactory situation has now been significantly improved by a dedicated multi-machine ohmic and L-mode limiter plasma study, conducted under the auspices of the International Tokamak Physics Activity, involving 11 tokamaks covering a wide parameter range with R=\\text{0}\\text{.4--2}\\text{.8} \\text{m}, {{B}0}=\\text{1}\\text{.2--7}\\text{.5} \\text{T}, {{I}\\text{p}}=\\text{9--2500} \\text{kA}. Measurements of λ q\\text{omp} in the database are made exclusively on all devices using a variety of fast reciprocating Langmuir probes entering the plasma at a variety of poloidal locations, but with the majority being on the low field side. Statistical analysis of the database reveals nine reasonable engineering and dimensionless scalings. All yield, however, similar

  9. 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.

  10. Analytical modeling of equilibrium of strongly anisotropic plasma in tokamaks and stellarators

    SciTech Connect

    Lepikhin, N. D.; Pustovitov, V. D.

    2013-08-15

    Theoretical analysis of equilibrium of anisotropic plasma in tokamaks and stellarators is presented. The anisotropy is assumed strong, which includes the cases with essentially nonuniform distributions of plasma pressure on magnetic surfaces. Such distributions can arise at neutral beam injection or at ion cyclotron resonance heating. Then the known generalizations of the standard theory of plasma equilibrium that treat p{sub ‖} and p{sub ⊥} (parallel and perpendicular plasma pressures) as almost constant on magnetic surfaces are not applicable anymore. Explicit analytical prescriptions of the profiles of p{sub ‖} and p{sub ⊥} are proposed that allow modeling of the anisotropic plasma equilibrium even with large ratios of p{sub ‖}/p{sub ⊥} or p{sub ⊥}/p{sub ‖}. A method for deriving the equation for the Shafranov shift is proposed that does not require introduction of the flux coordinates and calculation of the metric tensor. It is shown that for p{sub ⊥} with nonuniformity described by a single poloidal harmonic, the equation for the Shafranov shift coincides with a known one derived earlier for almost constant p{sub ⊥} on a magnetic surface. This does not happen in the other more complex case.

  11. Novel approaches for mitigating runaway electrons and plasma disruptions in ADITYA tokamak

    NASA Astrophysics Data System (ADS)

    Tanna, R. L.; Ghosh, J.; Chattopadhyay, P. K.; Dhyani, Pravesh; Purohit, Shishir; Joisa, S.; Rao, C. V. S.; Panchal, V. K.; Raju, D.; Jadeja, K. A.; Bhatt, S. B.; Gupta, C. N.; Chavda, Chhaya; Kulkarni, S. V.; Shukla, B. K.; Praveenlal E., V.; Raval, Jayesh; Amardas, A.; Atrey, P. K.; Dhobi, U.; Manchanda, R.; Ramaiya, N.; Patel, N.; Chowdhuri, M. B.; Jha, S. K.; Jha, R.; Sen, A.; Saxena, Y. C.; Bora, D.; the ADITYA Team

    2015-06-01

    This paper summarizes the results of recent dedicated experiments on disruption control and runaway mitigation carried out in ADITYA, which are of the utmost importance for the successful operation of large size tokamaks, such as ITER. It is quite a well-known fact that disruptions in tokamaks must be avoided. Disruptions, induced by hydrogen gas puffing, are successfully avoided by two innovative techniques in ADITYA using a bias electrode placed inside the last closed flux surface and applying an ion cyclotron resonance pulse with a power of ∼50 to 70 kW. These experiments led to better understanding of the disruption avoidance mechanisms and also can be thought of as one of the options for disruption avoidance in ITER. In both cases, the physical mechanism seems to be the control of magnetohydrodynamic modes due to increased poloidal rotation of edge plasma generated by induced radial electric fields. Real time avoidance of disruption with identifying proper precursors in both the mechanisms is successfully attempted. Further, analysing thoroughly the huge database of different types of spontaneous and deliberately-triggered disruptions from ADITYA, a significant contribution has been made to the international disruption database (ITPA). Furthermore, the mitigation of the runaway electron generated mainly during disruptions remains a challenging topic in present tokamak research as these high-energy electrons can cause severe damage to in-vessel components and the vacuum vessel. A simple technique has been implemented in ADITYA to mitigate the runaway electrons before they can gain high energies using a localized vertical magnetic field perturbation applied at one toroidal location to extract runaway electrons.

  12. Electric potential dynamics in OH and ECRH plasmas in the T-10 tokamak

    NASA Astrophysics Data System (ADS)

    Melnikov, A. V.; Eliseev, L. G.; Perfilov, S. V.; Andreev, V. F.; Grashin, S. A.; Dyabilin, K. S.; Chudnovskiy, A. N.; Isaev, M. Yu.; Lysenko, S. E.; Mavrin, V. A.; Mikhailov, M. I.; Ryzhakov, D. V.; Shurygin, R. V.; Zenin, V. N.; the T-10 Team

    2013-09-01

    New experimental observations of the plasma potential using the heavy ion beam probe diagnostic are presented together with a theoretical description of the formation of the electric field Er in the T-10 circular tokamak (B0 = 1.5-2.5 T, R = 1.5 m, a = 0.3 m). Ohmically heated (OH) deuterium plasmas with main plasma parameters \\bar{{n}}_{e} =(0.6{--}4.7)\\times 10^{19}\\,m^{-3} , Te(0) < 1.3 keV, Ti(0) < 0.6 keV are characterized by a negative potential φ(ρ) with maximum negative values of φ(6 cm) = -1400 V with respect to the wall. The potential profile monotonically increases towards the plasma edge. A density rise due to gas puff is accompanied by a plasma potential that becomes increasingly negative. When the density approaches values in the range \\bar{{n}}_{e} =(2.5{--}3.5)\\times 10^{19}\\,m^{-3} , the value of the plasma potential saturates, while the energy confinement time still increases up to a saturation value that is obtained at a slightly higher density. With auxiliary heating by electron cyclotron resonance heating (ECRH) up to 1.2 MW, Te(0) increases (up to 3 keV) and the absolute value of the plasma potential decreases. In some cases the plasma potential changes its sign and becomes positive at the edge. The radial profile of Er and its dependence on ne and Ti are qualitatively explained by a neoclassical model in the core, and a turbulent dynamic model (Braginskij magnetohydrodynamic equations) in the edge.

  13. Nonlinear evolution of multi-helicity neo-classical tearing modes in rotating tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Wei, Lai; Wang, Zheng-Xiong; Wang, Jialei; Yang, Xuefeng

    2016-10-01

    Plasma perturbations from the core and/or boundary regions of tokamaks can provide seed islands for the excitation of neo-classical tearing modes (NTMs) with negative {{ Δ }\\prime} , where {{ Δ }\\prime} is the linear instability parameter of the classical tearing mode. In this work, by means of reduced magnetohydrodynamic simulations, we numerically investigate the nonlinear evolution of multi-helicity NTMs in rotating tokamak plasmas with these two types of plasma perturbations with different boundary conditions. In the first case of initial plasma perturbations from the core region with a zero boundary condition, the meta-stable property of seed-island triggered NTM with negative {{ Δ }\\prime} is verified in the single helicity simulation. Nevertheless in the multiple helicity simulation, this seed-island triggered NTM with negative {{ Δ }\\prime} can be suppressed by a spontaneous NTM with positive {{ Δ }\\prime} through the competitive interaction between NTMs with different helicities. If a fixed poloidal rotation is taken into account in the first case, two different helicity NTMs could coexist in the saturation stage, which is different qualitatively from the process without plasma rotation. In the second case of initial plasma perturbations from the boundary region with a nonzero boundary condition, as the amplitude of plasma perturbations on the boundary increases, the mode with negative {{ Δ }\\prime} gradually changes from the driven-reconnection state to the NTM state, accompanied by an enhancement of magnetic island width in the single helicity simulation. Nevertheless in the multi-helicity simulation, the spontaneous NTM with positive {{ Δ }\\prime} can make the driven-reconnection triggered NTM with negative {{ Δ }\\prime} transfer from the NTM state back to the driven-reconnection state again. The underlying mechanism behind these transitions is analyzed step by step. Effects of fixed and unfixed poloidal rotations on the nonlinear

  14. The Two-Dimensional Structure of Partially Detached Divertor Plasmas in the DIII--D Tokamak

    NASA Astrophysics Data System (ADS)

    Fenstermacher, M. E.

    1996-11-01

    In this paper we present recent measurements of the 2-D spatial profiles of divertor plasma density, temperature, and emissivity in the DIII--D tokamak under highly radiating conditions in which there is a strong reduction in plasma pressure and energy conduction along the open field lines of the scrape-off layer (Partially Detached Divertor). This regime is desirable because the energy flux to the divertor targets can be reduced by up to a factor of 10 by the increased radiation, thus allowing for reliable divertor designs in high power tokamaks such as ITER. The data presented here are obtained using a newly installed Divertor Thomson Scattering (DTS) system specifically optimized for measuring the high electron densities and low temperatures expected in these detached divertor plasmas (ne <= 10^21 m-3, 0.5 eV <= T_e). These data are correlated with simultaneous measurements from fixed and fast-plunging Langmuir probes, VUV spectrometers, bolometers, and visible-light TV cameras. The DTS data confirm that electron pressure is nearly constant along field lines in attached plasmas, consistent with upstream and target plate diagnostics. D2 gas puffing in the divertor increases the plasma radiation and lowers Te to <2 eV in most of the divertor volume. Modeling shows that this temperature is low enough to allow ion-neutral collisions, charge exchange, and volume recombination to play significant roles in reducing the electron pressure along the magnetic separatrix by 3--5×, consistent with the measurements. At these temperatures, molecules may also be present in significant numbers and can further increase the recombination rates (Krasheninnikov, et al., J. Nucl. Mater. 1996). Farther out in the SOL, the electron density and pressure rise to values higher than those on the same flux surface at the midplane, so only part of the divertor plasma is detached. Absolutely-calibrated VUV spectroscopy and 2-D images of impurity emission show that the reduction in Te results

  15. Experiments on Turbulence and Transport in the Edge Plasma of the Text Tokamak

    NASA Astrophysics Data System (ADS)

    Rhodes, Terry Lee

    We studied the turbulence and fluctuation driven transport in the edge plasma of the TEXT tokamak using a Langmuir probe array. In this dissertation we present three separate experiments, each of which examines a particular aspect of the edge turbulence and transport. In the first experiment we compare the observed fluctuation levels to the scaling predictions of several turbulence theories. We found that the fluctuations and transport were not proportional to the density and temperature gradients. Thus, drift wave turbulence theories, which predict strong scalings with density gradients, do not describe the edge plasma turbulence. In the second experiment we identify low frequency modulations (<=q1KHz) in the edge density, potential and temperature to be associated with heat and density pulses (sawtooth oscillations) which originate from the central region of the tokamak. Concurrent with the edge sawtooth oscillations are significant increases in the density and potential fluctuation levels. As a result of these increases, the fluctuation driven particle flux and associated heat flux are increased as much as 60 and 100% respectively during the sawtooth. This result has direct implications on the current methods of determining the electron thermal diffusivity chi_ {e}. The effect of electron cyclotron heating (ECH) on the edge plasma was investigated in the third experiment. Increases in edge temperature, density and potential with simultaneous increases in the density and potential fluctuations were observed during ECH. These increased fluctuation levels resulted in a significant increase (20-50%) in the fluctuation driven particle flux. Comparison of these results to an equal input power, ohmic only discharge showed similar increases in the average density, temperature and potential. However, the density fluctuations did not increase as much with the additional ohmic heating (compared to ECH) resulting in a generally smaller comparative level of fluctuation

  16. Development of an integrated energetic neutral particle measurement system on experimental advanced full superconducting tokamak

    SciTech Connect

    Zhu, Y. B. Liu, D.; Heidbrink, W. W.; Zhang, J. Z.; Qi, M. Z.; Xia, S. B.; Wan, B. N.; Li, J. G.

    2014-11-15

    Full function integrated, compact silicon photodiode based solid state neutral particle analyzers (ssNPA) have been developed for energetic particle (EP) relevant studies on the Experimental Advanced Superconducting Tokamak (EAST). The ssNPAs will be mostly operated in advanced current mode with a few channels to be operated in conventional pulse-counting mode, aiming to simultaneously achieve individually proved ultra-fast temporal, spatial, and spectral resolution capabilities. The design details together with considerations on EAST specific engineering realities and physics requirements are presented. The system, including a group of single detectors on two vertical ports and two 16-channel arrays on a horizontal port, can provide both active and passive charge exchange measurements. ssNPA detectors, with variable thickness of ultra thin tungsten dominated foils directly deposited on the front surface, are specially fabricated and utilized to achieve about 22 keV energy resolution for deuterium particle detection.

  17. First results from solid state neutral particle analyzer on experimental advanced superconducting tokamak

    NASA Astrophysics Data System (ADS)

    Zhang, J. Z.; Zhu, Y. B.; Zhao, J. L.; Wan, B. N.; Li, J. G.; Heidbrink, W. W.

    2016-11-01

    Full function integrated, compact solid state neutral particle analyzers (ssNPA) based on absolute extreme ultraviolet silicon photodiode have been successfully implemented on the experimental advanced superconducting tokamak to measure energetic particle. The ssNPA system has been operated in advanced current mode with fast temporal and spatial resolution capabilities, with both active and passive charge exchange measurements. It is found that the ssNPA flux signals are increased substantially with neutral beam injection (NBI). The horizontal active array responds to modulated NBI beam promptly, while weaker change is presented on passive array. Compared to near-perpendicular beam, near-tangential beam brings more passive ssNPA flux and a broader profile, while no clear difference is observed on active ssNPA flux and its profile. Significantly enhanced intensities on some ssNPA channels have been observed during ion cyclotron resonant heating.

  18. Development of an integrated energetic neutral particle measurement system on experimental advanced full superconducting tokamak

    NASA Astrophysics Data System (ADS)

    Zhu, Y. B.; Zhang, J. Z.; Qi, M. Z.; Xia, S. B.; Liu, D.; Heidbrink, W. W.; Wan, B. N.; Li, J. G.

    2014-11-01

    Full function integrated, compact silicon photodiode based solid state neutral particle analyzers (ssNPA) have been developed for energetic particle (EP) relevant studies on the Experimental Advanced Superconducting Tokamak (EAST). The ssNPAs will be mostly operated in advanced current mode with a few channels to be operated in conventional pulse-counting mode, aiming to simultaneously achieve individually proved ultra-fast temporal, spatial, and spectral resolution capabilities. The design details together with considerations on EAST specific engineering realities and physics requirements are presented. The system, including a group of single detectors on two vertical ports and two 16-channel arrays on a horizontal port, can provide both active and passive charge exchange measurements. ssNPA detectors, with variable thickness of ultra thin tungsten dominated foils directly deposited on the front surface, are specially fabricated and utilized to achieve about 22 keV energy resolution for deuterium particle detection.

  19. Development of an integrated energetic neutral particle measurement system on experimental advanced full superconducting tokamak.

    PubMed

    Zhu, Y B; Zhang, J Z; Qi, M Z; Xia, S B; Liu, D; Heidbrink, W W; Wan, B N; Li, J G

    2014-11-01

    Full function integrated, compact silicon photodiode based solid state neutral particle analyzers (ssNPA) have been developed for energetic particle (EP) relevant studies on the Experimental Advanced Superconducting Tokamak (EAST). The ssNPAs will be mostly operated in advanced current mode with a few channels to be operated in conventional pulse-counting mode, aiming to simultaneously achieve individually proved ultra-fast temporal, spatial, and spectral resolution capabilities. The design details together with considerations on EAST specific engineering realities and physics requirements are presented. The system, including a group of single detectors on two vertical ports and two 16-channel arrays on a horizontal port, can provide both active and passive charge exchange measurements. ssNPA detectors, with variable thickness of ultra thin tungsten dominated foils directly deposited on the front surface, are specially fabricated and utilized to achieve about 22 keV energy resolution for deuterium particle detection.

  20. Interaction of high-energy trapped particles with ballooning modes in a tokamak with a high-. beta. plasma

    SciTech Connect

    Mikhailovskii, A. B.; Novakovaskii, S. V.; Smolyakov, A. I.

    1988-12-01

    A theory is derived for the interaction of high-energy trapped particleswith ballooning modes in a tokamak with a high-..beta.. plasma. A dispersionrelation is derived to describe the ballooning modes in the presence ofsuch particles; the effects of the high plasma ..beta.. are taken into account.The stability boundary for ballooning modes with zero and finite frequenciesis studied. The effects of finite bananas on the stability of ballooningmodes with zero frequencies are determined.

  1. Dynamics of kinetic geodesic-acoustic modes and the radial electric field in tokamak neoclassical plasmas

    NASA Astrophysics Data System (ADS)

    Xu, X. Q.; Belli, E.; Bodi, K.; Candy, J.; Chang, C. S.; Cohen, R. H.; Colella, P.; Dimits, A. M.; Dorr, M. R.; Gao, Z.; Hittinger, J. A.; Ko, S.; Krasheninnikov, S.; McKee, G. R.; Nevins, W. M.; Rognlien, T. D.; Snyder, P. B.; Suh, J.; Umansky, M. V.

    2009-06-01

    We present edge gyrokinetic simulations of tokamak plasmas using the fully non-linear (full-f) continuum code TEMPEST. A non-linear Boltzmann model is used for the electrons. The electric field is obtained by solving the 2D gyrokinetic Poisson equation. We demonstrate the following. (1) High harmonic resonances (n > 2) significantly enhance geodesic-acoustic mode (GAM) damping at high q (tokamak safety factor), and are necessary to explain the damping observed in our TEMPEST q-scans and consistent with the experimental measurements of the scaling of the GAM amplitude with edge q95 in the absence of obvious evidence that there is a strong q-dependence of the turbulent drive and damping of the GAM. (2) The kinetic GAM exists in the edge for steep density and temperature gradients in the form of outgoing waves, its radial scale is set by the ion temperature profile, and ion temperature inhomogeneity is necessary for GAM radial propagation. (3) The development of the neoclassical electric field evolves through different phases of relaxation, including GAMs, their radial propagation and their long-time collisional decay. (4) Natural consequences of orbits in the pedestal and scrape-off layer region in divertor geometry are substantial non-Maxwellian ion distributions and parallel flow characteristics qualitatively like those observed in experiments.

  2. Particle control and plasma performance in the Lithium Tokamak eXperiment

    SciTech Connect

    Majeski, R.; Abrams, T.; Boyle, D.; Granstedt, E.; Hare, J.; Jacobson, C. M.; Kaita, R.; Kozub, T.; LeBlanc, B.; Lundberg, D. P.; Lucia, M.; Merino, E.; Schmitt, J.; Stotler, D.; Biewer, T. M.; Canik, J. M.; Gray, T. K.; Maingi, R.; McLean, A. G.; Kubota, S.; and others

    2013-05-15

    The Lithium Tokamak eXperiment is a small, low aspect ratio tokamak [Majeski et al., Nucl. Fusion 49, 055014 (2009)], which is fitted with a stainless steel-clad copper liner, conformal to the last closed flux surface. The liner can be heated to 350 °C. Several gas fueling systems, including supersonic gas injection and molecular cluster injection, have been studied and produce fueling efficiencies up to 35%. Discharges are strongly affected by wall conditioning. Discharges without lithium wall coatings are limited to plasma currents of order 10 kA, and discharge durations of order 5 ms. With solid lithium coatings discharge currents exceed 70 kA, and discharge durations exceed 30 ms. Heating the lithium wall coating, however, results in a prompt degradation of the discharge, at the melting point of lithium. These results suggest that the simplest approach to implementing liquid lithium walls in a tokamak—thin, evaporated, liquefied coatings of lithium—does not produce an adequately clean surface.

  3. Nitrogen retention mechanisms in tokamaks with beryllium and tungsten plasma-facing surfaces

    NASA Astrophysics Data System (ADS)

    Oberkofler, M.; Meisl, G.; Hakola, A.; Drenik, A.; Alegre, D.; Brezinsek, S.; Craven, R.; Dittmar, T.; Keenan, T.; Romanelli, S. G.; Smith, R.; Douai, D.; Herrmann, A.; Krieger, K.; Kruezi, U.; Liang, G.; Linsmeier, Ch; Mozetic, M.; Rohde, V.; the ASDEX Upgrade Team; the EUROfusion MST1 Team; Contributors, JET

    2016-02-01

    Global gas balance experiments at ASDEX Upgrade (AUG) and JET have shown that a considerable fraction of nitrogen injected for radiative cooling is not recovered as N2 upon regeneration of the liquid helium cryo pump. The most probable loss channels are ion implantation into plasma-facing materials, co-deposition and ammonia formation. These three mechanisms are investigated in laboratory and tokamak experiments and by numerical simulations. Laboratory experiments have shown that implantation of nitrogen ions into beryllium and tungsten leads to the formation of surface nitrides, which may decompose under thermal loads. On beryllium the presence of nitrogen at the surface has been seen to reduce the sputtering yield. On tungsten surfaces it has been observed that the presence of nitrogen can increase hydrogen retention. The global nitrogen retention in AUG by implantation into the tungsten surfaces saturates. At JET the steady state nitrogen retention is increased by co-deposition with beryllium. The tokamak experiments are interpreted in detail by simulations of the global migration with WallDYN. Mass spectrometry of the exhaust gas of AUG and JET has revealed the conversion of nitrogen to ammonia at percent-levels. Conclusions are drawn on the potential implications of nitrogen seeding on the operation of a reactor in a deuterium-tritium mix.

  4. Data Acquisition and Automation for Plasma Rotation Diagnostic in the TCABR Tokamak

    NASA Astrophysics Data System (ADS)

    Ronchi, G.; Severo, J. H. F.; de Sá, W. P.; Galvão, R. M. O.

    2015-03-01

    In this work we describe the implementation of a full modular system of data acquisition and processing for the plasma rotation diagnostic in the TCABR tokamak. The experimental setup uses a single monochromator and six photomultipliers (PMT), in which pair of PMTs measures the light at slightly different wavelengths. Thus, it can measure the time evolution of the Doppler shift of the impurities emission lines coming from three spatial positions (one for toroidal rotation and two for poloidal rotation). The data acquisition and preanalysis program were written with LabVIEW software and is capable of controlling the spectrometer wavelength, PMTs power supplies, data acquisition, and storage. All data are recorded in MDSplus trees that easily allow data visualization and post-processing analysis (both locally and remotely) via MATLAB, Python, Java and others programming languages. This system can run independently from other diagnostics and machine systems and can be integrated with the main tokamak control system by means of TCP/IP messages.

  5. Simulations of the L-H transition on experimental advanced superconducting Tokamak

    SciTech Connect

    Weiland, Jan

    2014-12-15

    We have simulated the L-H transition on the EAST tokamak [Baonian Wan, EAST and HT-7 Teams, and International Collaborators, “Recent experiments in the EAST and HT-7 superconducting tokamaks,” Nucl. Fusion 49, 104011 (2009)] using a predictive transport code where ion and electron temperatures, electron density, and poloidal and toroidal momenta are simulated self consistently. This is, as far as we know, the first theory based simulation of an L-H transition including the whole radius and not making any assumptions about where the barrier should be formed. Another remarkable feature is that we get H-mode gradients in agreement with the α – α{sub d} diagram of Rogers et al. [Phys. Rev. Lett. 81, 4396 (1998)]. Then, the feedback loop emerging from the simulations means that the L-H power threshold increases with the temperature at the separatrix. This is a main feature of the C-mod experiments [Hubbard et al., Phys. Plasmas 14, 056109 (2007)]. This is also why the power threshold depends on the direction of the grad B drift in the scrape off layer and also why the power threshold increases with the magnetic field. A further significant general H-mode feature is that the density is much flatter in H-mode than in L-mode.

  6. Simulations of the L-H transition on experimental advanced superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Weiland, Jan

    2014-12-01

    We have simulated the L-H transition on the EAST tokamak [Baonian Wan, EAST and HT-7 Teams, and International Collaborators, "Recent experiments in the EAST and HT-7 superconducting tokamaks," Nucl. Fusion 49, 104011 (2009)] using a predictive transport code where ion and electron temperatures, electron density, and poloidal and toroidal momenta are simulated self consistently. This is, as far as we know, the first theory based simulation of an L-H transition including the whole radius and not making any assumptions about where the barrier should be formed. Another remarkable feature is that we get H-mode gradients in agreement with the α - αd diagram of Rogers et al. [Phys. Rev. Lett. 81, 4396 (1998)]. Then, the feedback loop emerging from the simulations means that the L-H power threshold increases with the temperature at the separatrix. This is a main feature of the C-mod experiments [Hubbard et al., Phys. Plasmas 14, 056109 (2007)]. This is also why the power threshold depends on the direction of the grad B drift in the scrape off layer and also why the power threshold increases with the magnetic field. A further significant general H-mode feature is that the density is much flatter in H-mode than in L-mode.

  7. Plasma current start-up by the outer ohmic heating coils in the Saskatchewan TORus Modified (STOR-M) iron core tokamak.

    PubMed

    Mitarai, O; Xiao, C; McColl, D; Dreval, M; Hirose, A; Peng, M

    2015-03-01

    A plasma current up to 15 kA has been driven with outer ohmic heating (OH) coils in the STOR-M iron core tokamak. Even when the inner OH coil is disconnected, the outer OH coils alone can induce the plasma current as primary windings and initial breakdown are even easier in this coil layout. This result suggests a possibility to use an iron core in a spherical tokamak to start up the plasma current without a central solenoid. The effect of the iron core saturation on the extension of the discharge pulse length has been estimated for further experiments in the STOR-M tokamak.

  8. Method of sustaining a radial electric field and poloidal plasma rotation over most of the cross-section of a tokamak

    DOEpatents

    Darrow, Douglass S.; Ono, Masayuki

    1990-03-06

    A radial electric field of a desired magnitude and configuration is created throughout a substantial portion of the cross-section of the plasma of a tokamak. The radial electric field is created by injection of a unidirectional electron beam. The magnitude and configuration of the radial electric field may be controlled by the strength of the toroidal magnetic field of the tokamak.

  9. Method of sustaining a radial electric field and poloidal plasma rotation over most of the cross-section of a tokamak

    DOEpatents

    Darrow, Douglass S.; Ono, Masayuki

    1990-01-01

    A radial electric field of a desired magnitude and configuration is created hroughout a substantial portion of the cross-section of the plasma of a tokamak. The radial electric field is created by injection of a unidirectional electron beam. The magnitude and configuration of the radial electric field may be controlled by the strength of the toroidal magnetic field of the tokamak.

  10. Plasma interaction with tungsten samples in the COMPASS tokamak in ohmic ELMy H-modes

    NASA Astrophysics Data System (ADS)

    Dimitrova, M.; Weinzettl, V.; Matejicek, J.; Popov, Tsv; Marinov, S.; Costea, S.; Dejarnac, R.; Stöckel, J.; Havlicek, J.; Panek, R.

    2016-03-01

    This paper reports experimental results on plasma interaction with tungsten samples with or without pre-grown He fuzz. Under the experimental conditions, arcing was observed on the fuzzy tungsten samples, resulting in localized melting of the fuzz structure that did not extend into the bulk. The parallel power flux densities were obtained from the data measured by Langmuir probes embedded in the divertor tiles on the COMPASS tokamak. Measurements of the current-voltage probe characteristics were performed during ohmic ELMy H-modes reached in deuterium plasmas at a toroidal magnetic field BT = 1.15 T, plasma current Ip = 300 kA and line-averaged electron density ne = 5×1019 m-3. The data obtained between the ELMs were processed by the recently published first-derivative probe technique for precise determination of the plasma potential and the electron energy distribution function (EEDF). The spatial profile of the EEDF shows that at the high-field side it is Maxwellian with a temperature of 5 -- 10 eV. The electron temperatures and the ion-saturation current density obtained were used to evaluate the radial distribution of the parallel power flux density as being in the order of 0.05 -- 7 MW/m2.

  11. Kinetic description of rotating Tokamak plasmas with anisotropic temperatures in the collisionless regime

    SciTech Connect

    Cremaschini, Claudio; Tessarotto, Massimo

    2011-11-15

    A largely unsolved theoretical issue in controlled fusion research is the consistent kinetic treatment of slowly-time varying plasma states occurring in collisionless and magnetized axisymmetric plasmas. The phenomenology may include finite pressure anisotropies as well as strong toroidal and poloidal differential rotation, characteristic of Tokamak plasmas. Despite the fact that physical phenomena occurring in fusion plasmas depend fundamentally on the microscopic particle phase-space dynamics, their consistent kinetic treatment remains still essentially unchallenged to date. The goal of this paper is to address the problem within the framework of Vlasov-Maxwell description. The gyrokinetic treatment of charged particles dynamics is adopted for the construction of asymptotic solutions for the quasi-stationary species kinetic distribution functions. These are expressed in terms of the particle exact and adiabatic invariants. The theory relies on a perturbative approach, which permits to construct asymptotic analytical solutions of the Vlasov-Maxwell system. In this way, both diamagnetic and energy corrections are included consistently into the theory. In particular, by imposing suitable kinetic constraints, the existence of generalized bi-Maxwellian asymptotic kinetic equilibria is pointed out. The theory applies for toroidal rotation velocity of the order of the ion thermal speed. These solutions satisfy identically also the constraints imposed by the Maxwell equations, i.e., quasi-neutrality and Ampere's law. As a result, it is shown that, in the presence of nonuniform fluid and EM fields, these kinetic equilibria can sustain simultaneously toroidal differential rotation, quasi-stationary finite poloidal flows and temperature anisotropy.

  12. Near-infrared spectroscopy for divertor plasma diagnosis and control in DIII-D tokamak

    SciTech Connect

    Soukhanovskii, V. A. McLean, A. G.; Allen, S. L.

    2014-11-15

    New near infrared (NIR) spectroscopic measurements performed in the DIII-D tokamak divertor plasma suggest new viable diagnostic applications: divertor recycling and low-Z impurity flux measurements, a spectral survey for divertor Thomson scattering (DTS) diagnostic, and T{sub e} monitoring for divertor detachment control. A commercial 0.3 m spectrometer coupled to an imaging lens via optical fiber and a InGaAs 1024 pixel array detector enabled deuterium and impurity emission measurements in the range 800–2300 nm. The first full NIR survey identified D, He, B, Li, C, N, O, Ne lines and provided plasma T{sub e}, n{sub e} estimates from deuterium Paschen and Brackett series intensity and Stark line broadening analysis. The range 1.000–1.060 mm was surveyed in high-density and neon seeded divertor plasmas for spectral background emission studies for λ = 1.064 μm laser-based DTS development. The ratio of adjacent deuterium Paschen-α and Brackett Br9 lines in recombining divertor plasmas is studied for divertor T{sub e} monitoring aimed at divertor detachment real-time feedback control.

  13. Near-infrared spectroscopy for divertor plasma diagnosis and control in DIII-D tokamak.

    PubMed

    Soukhanovskii, V A; McLean, A G; Allen, S L

    2014-11-01

    New near infrared (NIR) spectroscopic measurements performed in the DIII-D tokamak divertor plasma suggest new viable diagnostic applications: divertor recycling and low-Z impurity flux measurements, a spectral survey for divertor Thomson scattering (DTS) diagnostic, and Te monitoring for divertor detachment control. A commercial 0.3 m spectrometer coupled to an imaging lens via optical fiber and a InGaAs 1024 pixel array detector enabled deuterium and impurity emission measurements in the range 800-2300 nm. The first full NIR survey identified D, He, B, Li, C, N, O, Ne lines and provided plasma Te, ne estimates from deuterium Paschen and Brackett series intensity and Stark line broadening analysis. The range 1.000-1.060 mm was surveyed in high-density and neon seeded divertor plasmas for spectral background emission studies for λ = 1.064 μm laser-based DTS development. The ratio of adjacent deuterium Paschen-α and Brackett Br9 lines in recombining divertor plasmas is studied for divertor Te monitoring aimed at divertor detachment real-time feedback control. PMID:25430325

  14. Near-infrared spectroscopy for divertor plasma diagnosis and control in DIII-D tokamak.

    PubMed

    Soukhanovskii, V A; McLean, A G; Allen, S L

    2014-11-01

    New near infrared (NIR) spectroscopic measurements performed in the DIII-D tokamak divertor plasma suggest new viable diagnostic applications: divertor recycling and low-Z impurity flux measurements, a spectral survey for divertor Thomson scattering (DTS) diagnostic, and Te monitoring for divertor detachment control. A commercial 0.3 m spectrometer coupled to an imaging lens via optical fiber and a InGaAs 1024 pixel array detector enabled deuterium and impurity emission measurements in the range 800-2300 nm. The first full NIR survey identified D, He, B, Li, C, N, O, Ne lines and provided plasma Te, ne estimates from deuterium Paschen and Brackett series intensity and Stark line broadening analysis. The range 1.000-1.060 mm was surveyed in high-density and neon seeded divertor plasmas for spectral background emission studies for λ = 1.064 μm laser-based DTS development. The ratio of adjacent deuterium Paschen-α and Brackett Br9 lines in recombining divertor plasmas is studied for divertor Te monitoring aimed at divertor detachment real-time feedback control.

  15. The features of the global GAM in OH and ECRH plasmas in the T-10 tokamak

    NASA Astrophysics Data System (ADS)

    Melnikov, A. V.; Eliseev, L. G.; Perfilov, S. V.; Lysenko, S. E.; Shurygin, R. V.; Zenin, V. N.; Grashin, S. A.; Krupnik, L. I.; Kozachek, A. S.; Solomatin, R. Yu.; Elfimov, A. G.; Smolyakov, A. I.; Ufimtsev, M. V.; The HIBP Team

    2015-06-01

    Zonal flows and their high-frequency counterpart, the geodesic acoustic modes (GAMs) are considered as a possible mechanism of the plasma turbulence self-regulation. In the T-10 tokamak GAMs have been studied by the heavy ion beam probing and multipin Langmuir probes. The wide range of the regimes with Ohmic, on-axis and off-axis electron cyclotron resonance heating (ECRH) were studied (Bt = 1.5-2.4 T, Ip = 140-300 kA, \\bar{{n}}e = (0.6{--}6.0) × 1019 m-3 , PEC < 1.2 MW). It was shown that GAM has radially homogeneous structure and poloidal m = 0 for potential perturbations. The local theory predicts that fGAM ˜ \\sqrt {T/mi} /R , that means the frequency increases with the decrease of the minor radius. In contrast, the radial distribution of experimental frequency of the plasma potential and density oscillations, associated to GAM, is almost uniform over the whole plasma radius, suggesting the features of the nonlocal (global) eigenmodes. The GAM amplitude in the plasma potential also tends to be uniform along the radius. GAMs are more pronounced during ECRH, when the typical frequencies are seen in the narrow band from 22 to 27 kHz for the main peak and 25-30 kHz for the higher frequency satellite. GAM characteristics and the range of GAM existence are presented as functions of Te, density, magnetic field and PEC.

  16. M3D-K simulations of sawteeth and energetic particle transport in tokamak plasmas

    SciTech Connect

    Shen, Wei; Sheng, Zheng-Mao; Fu, G. Y.; Breslau, J. A.; Wang, Feng

    2014-09-15

    Nonlinear simulations of sawteeth and related energetic particle transport are carried out using the kinetic/magnetohydrodynamic (MHD) hybrid code M3D-K. MHD simulations show repeated sawtooth cycles for a model tokamak equilibrium. Furthermore, test particle simulations are carried out to study the energetic particle transport due to a sawtooth crash. The results show that energetic particles are redistributed radially in the plasma core, depending on pitch angle and energy. For trapped particles, the redistribution occurs for particle energy below a critical value in agreement with existing theories. For co-passing particles, the redistribution is strong with little dependence on particle energy. In contrast, the redistribution level of counter-passing particles decreases with increasing particle energy.

  17. Movable multi-probes for plasma boundary measurement in sino-united spherical tokamak

    SciTech Connect

    Chai, Song Wang, Wenhao; Tan, Yi; Gao, Zhe

    2014-11-15

    A novel movable multi-probes is developed to get local magnetic and electrostatic profiles on Sino-UNIted Spherical Tokamak (SUNIST). This multi-probes combines a four-tips Langmuir probe, a magnetic coil, and a retarding field energy analyzer (RFEA). It can be used to simultaneously measure the poloidal magnetic field B{sub p}, electric field E{sub r}, electron temperature T{sub e}, electron density n{sub e}, and ion temperature T{sub i}. Its small overall size (20 × 20 × 38 mm{sup 3}) enables the movable multi-probes to measure the magnetic and electrostatic profiles in high spatial resolution, with negligible impact to plasma in SUNIST. This paper presents the design of the movable multi-probes, in particular, details of RFEA for reliable ion energy measurements. Preliminary experimental results of the movable multi-probes are given as well.

  18. Gyrokinetic study of electromagnetic effects on toroidal momentum transport in tokamak plasmas

    SciTech Connect

    Hein, T.; Angioni, C.; Fable, E.; Candy, J.; Peeters, A. G.

    2011-07-15

    The effect of a finite {beta}{sub e} = 8{pi}n{sub e}T{sub e}/B{sup 2} on the turbulent transport of toroidal momentum in tokamak plasmas is discussed. From an analytical gyrokinetic model as well as local linear gyrokinetic simulations, it is shown that the modification of the parallel mode structure due to the nonadiabatic response of passing electrons, which changes the parallel wave vector k{sub ||} with increasing {beta}{sub e}, leads to a decrease in size of both the diagonal momentum transport as well as the Coriolis pinch under ion temperature gradient turbulence conditions, while for trapped electron modes, practically no modification is found. The decrease is particularly strong close to the onset of the kinetic ballooning modes. There, the Coriolis pinch even reverses its direction.

  19. A resistive magnetodynamics analysis of sawtooth driven tearing modes in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Guo, Wenping; Wang, Jiaqi; Liu, Dongjian; Wang, Xiaogang

    2016-06-01

    In this paper, a resistive magnetohydrodynamics model is applied to study the effect of sawtooth driven on classical/neoclassical tearing modes in tokamak plasmas. In a model of forced reconnection, the sawtooth is considered as a boundary disturbance for m >1 modes and causes the islands growth of m/n = 2/1 and 3/2 modes through toroidal coupling. Theoretical and numerical analyses show that the linear growth of the modes is driven by precursors of the sawtooth through the linear mode coupling, while differential rotation has great effect on both the linear and the nonlinear development of the modes. It is believed that the tearing mode can be suppressed by control of the sawtooth by radio frequency heating or current drive.

  20. Effects of toroidal field ripple on suprathermal ions in tokamak plasmas

    SciTech Connect

    Goldston, R.J.; Towner, H.H.

    1980-02-01

    Analytic calculations of three important effects of toroidal field ripple on suprathermal ions in tokamak plasmas are presented. In the first process, collisional ripple-trapping, beam ions become trapped in local magnetic wells near their banana tips due to pitch-angle scattering as they traverse the ripple on barely unripple-trapped orbits. In the second process, collisionless ripple-trapping, near-perpendicular untrapped ions are captured (again near a banana tip) due to their finite orbits, which carry them out into regions of higher ripple. In the third process, banana-drift diffusion, fast-ion banana orbits fail to close precisely, due to a ripple-induced variable lingering period near the banana tips. These three mechanisms lead to substantial radial transport of banana-trapped, neutral-beam-injected ions when the quantity ..cap alpha..* identical with epsilon/sin theta/Nqdelta is of order unity or smaller.

  1. Toroidal rotation of multiple species of ions in tokamak plasma driven by lower-hybrid-waves

    NASA Astrophysics Data System (ADS)

    Zuo, Yang; Wang, Shaojie; Pan, Chengkang

    2012-10-01

    A numerical simulation is carried out to investigate the toroidal rotation of multiple species of ions and the radial electric field in a tokamak plasma driven by the lower-hybrid-wave (LHW). The theoretical model is based on the neoclassical transport theory associated with the anomalous transport model. Three species of ions (primary ion and two species of impurity ions) are taken into consideration. The predicted toroidal velocity of the trace impurities during the LHW injection agrees reasonably well with the experimental observation. It is shown that the toroidal rotation velocities of the trace impurity ions and the primary ions are close, therefore the trace impurity ions are representative of the primary ions in the toroidal rotation driven by the LHW.

  2. Neoclassical transport coefficients for finite-aspect-ratio and bean-shaped tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Crume, E. C., Jr.; Beasley, C. O., Jr.; Hirshman, S. P.; van Rij, W. I.

    1987-04-01

    Numerically calculated tokamak equilibria are used to compute banana-plateau transport coefficients for finite-aspect-ratio, finite-beta plasmas. Calculations are presented for the Spherical Torus Experiment (STX) (NTIS Document No. DE 86004663) and the Princeton Beta Experiment (PBX) (NTIS Document No. DE 86011173). In STX, the poloidal variation of B≡‖B‖ over a magnetic surface tends to be reduced in regions of large major radius R. The reduction of radial transport caused by this quasiomnigeneous condition is offset by increased drifts and trapping probabilities for smaller R. Thus the modulation Δ=(Bmax-Bmin)/(Bmax+Bmin) on a magnetic surface becomes the critical parameter determining neoclassical transport. In PBX, the bean-shaped topology of the magnetic surfaces leads to the presence of multiple magnetic wells. Numerical calculations confirm that analytic calculations of neoclassical transport based on the total fraction of circulating particles are valid even when geometrically distinct classes of trapped particles are present.

  3. Observation of Double Impurity Critical Gradients for Electromagnetic Turbulence Excitation in Tokamak Plasmas.

    PubMed

    Zhong, W L; Shen, Y; Zou, X L; Gao, J M; Shi, Z B; Dong, J Q; Duan, X R; Xu, M; Cui, Z Y; Li, Y G; Ji, X Q; Yu, D L; Cheng, J; Xiao, G L; Jiang, M; Yang, Z C; Zhang, B Y; Shi, P W; Liu, Z T; Song, X M; Ding, X T; Liu, Yong

    2016-07-22

    The impact of impurity ions on a pedestal has been investigated in the HL-2A Tokamak, at the Southwestern Institute of Physics, Chengdu, China. Experimental results have clearly shown that during the H-mode phase, an electromagnetic turbulence was excited in the edge plasma region, where the impurity ions exhibited a peaked profile. It has been found that double impurity critical gradients are responsible for triggering the turbulence. Strong stiffness of the impurity profile has been observed during cyclic transitions between the I-phase and H-mode regime. The results suggest that the underlying physics of the self-regulated edge impurity profile offers the possibility for an active control of the pedestal dynamics via pedestal turbulence.

  4. Alfvén acoustic channel for ion energy in high-beta tokamak plasmas.

    PubMed

    Bierwage, Andreas; Aiba, Nobuyuki; Shinohara, Kouji

    2015-01-01

    When the plasma beta (ratio of thermal to magnetic pressure) in the core of a tokamak is raised to values of several percent, as required for a thermonuclear fusion reactor, continuous spectra of long-wavelength slow magnetosonic waves enter the frequency band occupied by continuous spectra of shear Alfvén waves. It is found that these two branches can couple strongly, so that Alfvén modes that are resonantly driven by suprathermal ions transfer some of their energy to sound waves. Since sound waves are heavily damped by thermal ion Landau resonances, these results reveal a new energy channel that contributes to the damping of Alfvénic instabilities and the noncollisional heating of bulk ions, with potentially important consequences for confinement and fusion performance.

  5. Movable multi-probes for plasma boundary measurement in Sino-UNIted Spherical Tokamak.

    PubMed

    Chai, Song; Wang, Wenhao; Tan, Yi; Gao, Zhe

    2014-11-01

    A novel movable multi-probes is developed to get local magnetic and electrostatic profiles on Sino-UNIted Spherical Tokamak (SUNIST). This multi-probes combines a four-tips Langmuir probe, a magnetic coil, and a retarding field energy analyzer (RFEA). It can be used to simultaneously measure the poloidal magnetic field Bp, electric field Er, electron temperature Te, electron density ne, and ion temperature Ti. Its small overall size (20 × 20 × 38 mm(3)) enables the movable multi-probes to measure the magnetic and electrostatic profiles in high spatial resolution, with negligible impact to plasma in SUNIST. This paper presents the design of the movable multi-probes, in particular, details of RFEA for reliable ion energy measurements. Preliminary experimental results of the movable multi-probes are given as well.

  6. Toroidal rotation of multiple species of ions in tokamak plasma driven by lower-hybrid-waves

    SciTech Connect

    Zuo Yang; Wang Shaojie; Pan Chengkang

    2012-10-15

    A numerical simulation is carried out to investigate the toroidal rotation of multiple species of ions and the radial electric field in a tokamak plasma driven by the lower-hybrid-wave (LHW). The theoretical model is based on the neoclassical transport theory associated with the anomalous transport model. Three species of ions (primary ion and two species of impurity ions) are taken into consideration. The predicted toroidal velocity of the trace impurities during the LHW injection agrees reasonably well with the experimental observation. It is shown that the toroidal rotation velocities of the trace impurity ions and the primary ions are close, therefore the trace impurity ions are representative of the primary ions in the toroidal rotation driven by the LHW.

  7. Method for determining fast-alpha-particle confinement in tokamak plasmas using resonant nuclear reactors

    SciTech Connect

    Cecil, F.E.; Zweben, S.J.; Medley, S.S.

    1986-03-01

    The resonant nuclear reactions D(..cap alpha..,..gamma..)/sup 6/Li, /sup 6/Li(..cap alpha..,..gamma..)/sup 10/B, and /sup 7/Li(..cap alpha..,..gamma..)/sup 11/B are examined as diagnostics of fast-alpha-particle confinement in tokamak plasmas. Gamma rays from these resonant reactions with energies from 2.1 MeV to 9.2 MeV may be used to infer the alpha-particle population between energies of 0.4 MeV and 2.6 MeV. The ratio of these alpha-burnup reactions to the reactions T(D,..gamma..)/sup 5/He and /sup 3/He(D,..gamma..)/sup 5/Li provides a technique for the measurement of alpha confinement.

  8. Ecological environment of the proposed site for the Compact Ignition Tokamak at Princeton Plasma Physics Laboratory

    SciTech Connect

    Not Available

    1987-12-01

    This report gives a description of the exological environment of D-site and the surrounding area at Princeton Plasma Physics Laboratory (PPPL) near Princeton, New Jersey. D-site at PPL is the proposed location for construction of a new fusion test facility, the Compact Ignition Tokamak (CIT). This report was prepared as supplemental information for an Environmental Assessment for the proposed CIT at PPL. The report characterizes the vegetation and wildlife occuring at and near the site and describes the water quality and aquatic ecology of Bee Brook. No threatened or endangered plant or animal species are known to occur in the area, although suitable habitat exists for some species. The occurrence of a forested wetland north of the site is discussed. 9 refs., 2 figs.

  9. Experimental Study on Electromagnetic Interactions between Plasmas and a Vacuum Vessel during Disruptions in the Hitachi Tokamak HT-2

    NASA Astrophysics Data System (ADS)

    Abe, Mitsushi; Takeuchi, Kazuhiro; Fukumoto, Hideshi; Shimizu, Masashi; Otsuka, Michio

    1990-02-01

    Electromagnetic interactions between plasmas and a vacuum vessel during disruptions are examined experimentally in the Hitachi tokamak HT-2. Eddy currents which flow in the toroidal direction and poloidal coil currents are determined from the measured magnetic data. The currents enable calculation of the electromagnetic force on the vacuum vessel and resistively dissipated magnetic energy. Eddy currents and electromagnetic forces are mainly due to the plasma displacement (shell effect), not decay of the plasma current. Large plasma current quench rate -dIP/dt is associated with scraping of the plasma by the inner limiter through the rapid plasma radial movement, and the decay rate in circular plasma is twice as large as that in elongated plasma. The magnetic energy dissipation is mainly due to the eddy current of the net toroidal current mode which is induced by large current quench rate.

  10. Bootstrap current for the edge pedestal plasma in a diverted tokamak geometry

    NASA Astrophysics Data System (ADS)

    Koh, S.; Chang, C. S.; Ku, S.; Menard, J. E.; Weitzner, H.; Choe, W.

    2012-07-01

    The edge bootstrap current plays a critical role in the equilibrium and stability of the steep edge pedestal plasma. The pedestal plasma has an unconventional and difficult neoclassical property, as compared with the core plasma. It has a narrow passing particle region in velocity space that can be easily modified or destroyed by Coulomb collisions. At the same time, the edge pedestal plasma has steep pressure and electrostatic potential gradients whose scale-lengths are comparable with the ion banana width, and includes a magnetic separatrix surface, across which the topological properties of the magnetic field and particle orbits change abruptly. A drift-kinetic particle code XGC0, equipped with a mass-momentum-energy conserving collision operator, is used to study the edge bootstrap current in a realistic diverted magnetic field geometry with a self-consistent radial electric field. When the edge electrons are in the weakly collisional banana regime, surprisingly, the present kinetic simulation confirms that the existing analytic expressions [represented by O. Sauter et al., Phys. Plasmas 6, 2834 (1999)] are still valid in this unconventional region, except in a thin radial layer in contact with the magnetic separatrix. The agreement arises from the dominance of the electron contribution to the bootstrap current compared with ion contribution and from a reasonable separation of the trapped-passing dynamics without a strong collisional mixing. However, when the pedestal electrons are in plateau-collisional regime, there is significant deviation of numerical results from the existing analytic formulas, mainly due to large effective collisionality of the passing and the boundary layer trapped particles in edge region. In a conventional aspect ratio tokamak, the edge bootstrap current from kinetic simulation can be significantly less than that from the Sauter formula if the electron collisionality is high. On the other hand, when the aspect ratio is close to unity

  11. Bootstrap current for the edge pedestal plasma in a diverted tokamak geometry

    SciTech Connect

    Koh, S.; Choe, W.; Chang, C. S.; Ku, S.; Menard, J. E.; Weitzner, H.

    2012-07-15

    The edge bootstrap current plays a critical role in the equilibrium and stability of the steep edge pedestal plasma. The pedestal plasma has an unconventional and difficult neoclassical property, as compared with the core plasma. It has a narrow passing particle region in velocity space that can be easily modified or destroyed by Coulomb collisions. At the same time, the edge pedestal plasma has steep pressure and electrostatic potential gradients whose scale-lengths are comparable with the ion banana width, and includes a magnetic separatrix surface, across which the topological properties of the magnetic field and particle orbits change abruptly. A drift-kinetic particle code XGC0, equipped with a mass-momentum-energy conserving collision operator, is used to study the edge bootstrap current in a realistic diverted magnetic field geometry with a self-consistent radial electric field. When the edge electrons are in the weakly collisional banana regime, surprisingly, the present kinetic simulation confirms that the existing analytic expressions [represented by O. Sauter et al., Phys. Plasmas 6, 2834 (1999)] are still valid in this unconventional region, except in a thin radial layer in contact with the magnetic separatrix. The agreement arises from the dominance of the electron contribution to the bootstrap current compared with ion contribution and from a reasonable separation of the trapped-passing dynamics without a strong collisional mixing. However, when the pedestal electrons are in plateau-collisional regime, there is significant deviation of numerical results from the existing analytic formulas, mainly due to large effective collisionality of the passing and the boundary layer trapped particles in edge region. In a conventional aspect ratio tokamak, the edge bootstrap current from kinetic simulation can be significantly less than that from the Sauter formula if the electron collisionality is high. On the other hand, when the aspect ratio is close to unity

  12. Bootstrap Current for the Edge Pedestal Plasma in a Diverted Tokamak Geometry

    SciTech Connect

    Koh, S.; Chang, C. S.; Ku, S.; Menard, J. E.; Weitzner, H.; Choe, W.

    2012-08-10

    The edge bootstrap current plays a critical role in the equilibrium and stability of the steep edge pedestal plasma. The pedestal plasma has an unconventional and difficult neoclassical property, as compared with the core plasma. It has a narrow passing particle region in velocity space that can be easily modified or destroyed by Coulomb collisions. At the same time, the edge pedestal plasma has steep pressure and electrostatic potential gradients whose scale-lengths are comparable with the ion banana width, and includes a magnetic separatrix surface, across which the topological properties of the magnetic field and particle orbits change abruptly. A driftkinetic particle code XGC0, equipped with a mass-momentum-energy conserving collision operator, is used to study the edge bootstrap current in a realistic diverted magnetic field geometry with a self-consistent radial electric field. When the edge electrons are in the weakly collisional banana regime, surprisingly, the present kinetic simulation confirms that the existing analytic expressions [represented by O. Sauter et al. , Phys. Plasmas 6 , 2834 (1999)] are still valid in this unconventional region, except in a thin radial layer in contact with the magnetic separatrix. The agreement arises from the dominance of the electron contribution to the bootstrap current compared with ion contribution and from a reasonable separation of the trapped-passing dynamics without a strong collisional mixing. However, when the pedestal electrons are in plateau-collisional regime, there is significant deviation of numerical results from the existing analytic formulas, mainly due to large effective collisionality of the passing and the boundary layer trapped particles in edge region. In a conventional aspect ratio tokamak, the edge bootstrap current from kinetic simulation can be significantly less than that from the Sauter formula if the electron collisionality is high. On the other hand, when the aspect ratio is close to unity

  13. Ion cyclotron emission from fusion-born ions in large tokamak plasmas: a brief review from JET and TFTR to ITER

    NASA Astrophysics Data System (ADS)

    Dendy, R. O.; McClements, K. G.

    2015-04-01

    Ion cyclotron emission (ICE) was the first collective radiative instability, driven by confined fusion-born ions, observed from deuterium-tritium plasmas in JET and TFTR. ICE comprises strongly suprathermal emission, which has spectral peaks at multiple ion cyclotron harmonic frequencies as evaluated at the outer mid-plane edge of tokamak plasmas. The measured intensity of ICE spectral peaks scaled linearly with measured fusion reactivity in JET. In other large tokamak plasmas, ICE is currently used as an indicator of fast ions physics. The excitation mechanism for ICE is the magnetoacoustic cyclotron instability (MCI); in the case of JET and TFTR, the MCI is driven by a set of centrally born trapped fusion products, lying just inside the trapped-passing boundary in velocity space, whose drift orbits make large radial excursions to the outer mid-plane edge. Diagnostic exploitation of ICE in future experiments therefore rests in part on deep understanding of the MCI, and recent advances in computational plasma physics have led to substantial recent progress, reviewed here. Particle-in-cell simulations of the MCI, with fully kinetic ions and electrons, were reported in 2013, using plasma parameters for JET ICE observations. The hybrid approximation for plasma simulations, where ions are treated as particles and electrons as a neutralising massless fluid, was then applied and reported in 2014. These simulations extend previous studies deep into the nonlinear regime of the MCI, and corroborate predictions by linear analytical theory, thereby strengthening further the link to ICE measurements. ICE is a potential diagnostic for confined alpha-particles in ITER, where measurements of ICE could yield information on energetic ion behaviour supplementing that obtainable from other diagnostics. In addition, it may be possible to use ICE to study fast ion redistribution and loss due to MHD activity in ITER.

  14. Advances in multi-megawatt lower hybrid technology in support of steady-state tokamak operation

    NASA Astrophysics Data System (ADS)

    Delpech, L.; Achard, J.; Armitano, A.; Artaud, J. F.; Bae, Y. S.; Belo, J. H.; Berger-By, G.; Bouquey, F.; Cho, M. H.; Corbel, E.; Decker, J.; Do, H.; Dumont, R.; Ekedahl, A.; Garibaldi, P.; Goniche, M.; Guilhem, D.; Hillairet, J.; Hoang, G. T.; Kim, H. S.; Kim, J. H.; Kim, H.; Kwak, J. G.; Magne, R.; Mollard, P.; Na, Y. S.; Namkung, W.; Oh, Y. K.; Park, S.; Park, H.; Peysson, Y.; Poli, S.; Prou, M.; Samaille, F.; Yang, H. L.; The Tore Supra Team

    2014-10-01

    It has been demonstrated that lower hybrid current drive (LHCD) systems play a crucial role for steady-state tokamak operation, owing to their high current drive (CD) efficiency and hence their capability to reduce flux consumption. This paper describes the extensive technology programmes developed for the Tore Supra (France) and the KSTAR (Korea) tokamaks in order to bring continuous wave (CW) LHCD systems into operation. The Tore Supra LHCD generator at 3.7 GHz is fully CW compatible, with RF power PRF = 9.2 MW available at the generator to feed two actively water-cooled launchers. On Tore Supra, the most recent and novel passive active multijunction (PAM) launcher has sustained 2.7 MW (corresponding to its design value of 25 MW m-2 at the launcher mouth) for a 78 s flat-top discharge, with low reflected power even at large plasma-launcher gaps. The fully active multijunction (FAM) launcher has reached 3.8 MW of coupled power (24 MW m-2 at the launcher mouth) with the new TH2103C klystrons. By combining both the PAM and FAM launchers, 950 MJ of energy, using 5.2 MW of LHCD and 1 MW of ICRH (ion cyclotron resonance heating), was injected for 160 s in 2011. The 3.7 GHz CW LHCD system will be a key element within the W (for tungsten) environment in steady-state Tokamak (WEST) project, where the aim is to test ITER technologies for high heat flux components in relevant heat flux density and particle fluence conditions. On KSTAR, a 2 MW LHCD system operating at 5 GHz is under development. Recently the 5 GHz prototype klystron has reached 500 kW/600 s on a matched load, and studies are ongoing to design a PAM launcher. In addition to the studies of technology, a combination of ray-tracing and Fokker-Planck calculations have been performed to evaluate the driven current and the power deposition due to LH waves, and to optimize the N∥ spectrum for the future launcher design. Furthermore, an LHCD system at 5 GHz is being considered for a future upgrade of the ITER

  15. Design and Preliminary Results of a Feedback Circuit for Plasma Displacement Control in IR-T1 Tokamak

    SciTech Connect

    TalebiTaher, A.; Ghoranneviss, M.; Tarkeshian, R.; Salem, M. K.; Khorshid, P.

    2008-04-07

    Since displacement is very important for plasma position control, in IR-T1 tokamak a combination of two cosine coils and two saddle sine coils is used for horizontal displacement measurement. According to the multiple moment theory, the output of these coils linearly depends to radial displacement of plasma column. A new circuit for adding these signals to feedback system designed and unwanted effects of other fields in final output compensated. After compensation and calibration of the system, the output of horizontal displacement circuits applied to feedback control system. By considers the required auxiliary vertical field, a proportional amplifier and driver circuit are constructed to drive power transistors these power transistors switch the feedback bank capacitors. In the experiment, a good linear proportionality between displacement and output observed by applying an appropriate feedback field, the linger confinement time in IR-T1 tokamak obtained, applying this system to discharge increased the plasma duration and realizes repetitive discharges.

  16. Design of a magnetic shielding system for the time of flight enhanced diagnostics neutron spectrometer at Experimental Advanced Superconducting Tokamak

    SciTech Connect

    Cui, Z. Q.; Chen, Z. J.; Xie, X. F.; Peng, X. Y.; Hu, Z. M.; Du, T. F.; Ge, L. J.; Zhang, X.; Yuan, X.; Fan, T. S.; Chen, J. X.; Li, X. Q. E-mail: guohuizhang@pku.edu.cn; Zhang, G. H. E-mail: guohuizhang@pku.edu.cn; Xia, Z. W.; Hu, L. Q.; Zhong, G. Q.; Lin, S. Y.; Wan, B. N.

    2014-11-15

    The novel neutron spectrometer TOFED (Time of Flight Enhanced Diagnostics), comprising 90 individual photomultiplier tubes coupled with 85 plastic scintillation detectors through light guides, has been constructed and installed at Experimental Advanced Superconducting Tokamak. A dedicated magnetic shielding system has been constructed for TOFED, and is designed to guarantee the normal operation of photomultiplier tubes in the stray magnetic field leaking from the tokamak device. Experimental measurements and numerical simulations carried out employing the finite element method are combined to optimize the design of the magnetic shielding system. The system allows detectors to work properly in an external magnetic field of 200 G.

  17. Design of a magnetic shielding system for the time of flight enhanced diagnostics neutron spectrometer at Experimental Advanced Superconducting Tokamak.

    PubMed

    Cui, Z Q; Chen, Z J; Xie, X F; Peng, X Y; Hu, Z M; Du, T F; Ge, L J; Zhang, X; Yuan, X; Xia, Z W; Hu, L Q; Zhong, G Q; Lin, S Y; Wan, B N; Fan, T S; Chen, J X; Li, X Q; Zhang, G H

    2014-11-01

    The novel neutron spectrometer TOFED (Time of Flight Enhanced Diagnostics), comprising 90 individual photomultiplier tubes coupled with 85 plastic scintillation detectors through light guides, has been constructed and installed at Experimental Advanced Superconducting Tokamak. A dedicated magnetic shielding system has been constructed for TOFED, and is designed to guarantee the normal operation of photomultiplier tubes in the stray magnetic field leaking from the tokamak device. Experimental measurements and numerical simulations carried out employing the finite element method are combined to optimize the design of the magnetic shielding system. The system allows detectors to work properly in an external magnetic field of 200 G.

  18. Prospects for Tokamak Fusion Reactors

    SciTech Connect

    Sheffield, J.; Galambos, J.

    1995-04-01

    This paper first reviews briefly the status and plans for research in magnetic fusion energy and discusses the prospects for the tokamak magnetic configuration to be the basis for a fusion power plant. Good progress has been made in achieving fusion reactor-level, deuterium-tritium (D-T) plasmas with the production of significant fusion power in the Joint European Torus (up to 2 MW) and the Tokamak Fusion Test Reactor (up to 10 MW) tokamaks. Advances on the technologies of heating, fueling, diagnostics, and materials supported these achievements. The successes have led to the initiation of the design phases of two tokamaks, the International Thermonuclear Experimental Reactor (ITER) and the US Toroidal Physics Experiment (TPX). ITER will demonstrate the controlled ignition and extended bum of D-T plasmas with steady state as an ultimate goal. ITER will further demonstrate technologies essential to a power plant in an integrated system and perform integrated testing of the high heat flux and nuclear components required to use fusion energy for practical purposes. TPX will complement ITER by testing advanced modes of steady-state plasma operation that, coupled with the developments in ITER, will lead to an optimized demonstration power plant.

  19. Theory of isolated, small-scale magnetic islands in a high temperature tokamak plasma

    SciTech Connect

    Connor, J.W.; Wilson, H.R.

    1995-12-01

    A theory for the existence of noninteracting small-scale, ``drift`` magnetic islands in a high temperature tokamak plasma is presented. This situation contrasts with that discussed by Rebut and Hugon [Plasma Phys. Controlled Fusion {bold 33}, 1085 (1991)] which involves a background ``sea`` of magnetic turbulence caused by island overlap. The islands are driven by the effect of finite ion Larmor radius on the particle drifts and they propagate with a velocity comparable to the diamagnetic velocity. In contrast with the work of Smolyakov [Plasma Phys. Controlled Fusion {bold 35}, 657 (1993)] collisions are assumed to be rare. Although the saturated island size is independent of the collision frequency in the model discussed here, collisions play a crucial role in determining the frequency of the magnetic islands. An estimate is made of the anomalous heat transport which results from the fluctuations in the electrostatic potential associated with these magnetic islands. The predicted thermal diffusivity has several, but not all, of the characteristics of the Rebut--Lallia--Watkins transport model. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  20. Plasma facing components: a conceptual design strategy for the first wall in FAST tokamak

    NASA Astrophysics Data System (ADS)

    Labate, C.; Di Gironimo, G.; Renno, F.

    2015-09-01

    Satellite tokamaks are conceived with the main purpose of developing new or alternative ITER- and DEMO-relevant technologies, able to contribute in resolving the pending issues about plasma operation. In particular, a high criticality needs to be associated to the design of plasma facing components, i.e. first wall (FW) and divertor, due to physical, topological and thermo-structural reasons. In such a context, the design of the FW in FAST fusion plant, whose operational range is close to ITER’s one, takes place. According to the mission of experimental satellites, the FW design strategy, which is presented in this paper relies on a series of innovative design choices and proposals with a particular attention to the typical key points of plasma facing components design. Such an approach, taking into account a series of involved physical constraints and functional requirements to be fulfilled, marks a clear borderline with the FW solution adopted in ITER, in terms of basic ideas, manufacturing aspects, remote maintenance procedure, manifolds management, cooling cycle and support system configuration.

  1. Neoclassical transport theory in a tokamak plasma with large spatial gradients

    SciTech Connect

    Chang, C.S.

    1996-12-31

    Usual neoclassical theories assumed that the spatical inhomogeneity of the plasma was weak. Specifically, this included the following two strong assumptions: banana width was negligible compared to the radial gradient scale length and variation of any physical quantity along the field line was small. This led to the simplification that the spatial inhomogeneity itself did not affect the fundamental transport processes. However, there have been many experimental suggestions that the spatial inhomogeneity may not be small. Firstly, both H-mode and ERS mode experiments have indicated that the finite banana width effect may be important to understand the plasma transport processes. Secondly, the RF and auxiliary heating processes may be sufficiently localized in space so that we may need to consider a strongly inhomogeneous heating effect along the field lines. In the present work we develop a modified neoclassical theory, in parallel with the old theories, which can include the finite banana width effect and the inhomogeneous heating effect. Several new and significant transport terms have been identified, which can play important roles in the understanding of the fundamental transport processes in a tokamak plasma.

  2. Edge Biasing of SINP-Tokamak Plasma in High-Q Regime

    NASA Astrophysics Data System (ADS)

    Pal, Rabindranath; Basu, Debjyoti

    2009-11-01

    In high q regime (qedge=5-7) of SINP-TOKAMAK [an iron-core device having major and minor radii of 30 and 7.5 cm, respectively and Btoroidal = 1.2 Tesla] fast edge biasing experiment is carried out introducing a Molybdenum electrode of 5mm in diameter, radially positioned at 7.0 cm. Biasing seems to cause a change in plasma current density profile forming a negative shear in the region 6.4-6.9 cm and it leads to better confinement and longer duration of plasma current as was observedfootnotetextGhosh J., Pal R., Chattopadhyay P. K. and Basu D. 2007 Nucl. Fusion 47 331 also in very low q (VLQ) regimes of the same machine. The electrode current drawn in this regime is about 5-10 amp. Lowering of Hα signal and loop voltage is also observed indicating better confinement, independently confirmed by diamagnetic loop too. On applying bias, electron density and temperature profile develop sharper gradient near the edge. Interestingly, electrostatic and magnetic fluctuations, observed by inserting electric and magnetic probes in the edge plasma, are suppressed in the inner region (6.4-6.8 cm) in the frequency range of 30-70 kHz by the effect of electrode biasing.

  3. Particle confinement of pellet-fuelled H-mode plasmas in the Mega Ampere Spherical Tokamak

    NASA Astrophysics Data System (ADS)

    Valovič, M.; Axon, K.; Garzotti, L.; Saarelma, S.; Thyagaraja, A.; Akers, R.; Gurl, C.; Kirk, A.; Lloyd, B.; Maddison, G. P.; Patel, A.; Shibaev, S.; Scannell, R.; Taylor, D.; Walsh, M.; MAST Team

    2008-07-01

    This paper quantifies the particle confinement of pellet-fuelled plasmas in the Mega Ampere Spherical Tokamak (MAST). The dataset is restricted mostly to neutral beam heated plasmas and to shallow pellets launched from the high field side. It is shown that the pellet deposition can be explained only by invoking the ∇B drift of the pellet ablatant. The pellet creates a zone with positive density gradient and increased temperature gradient. Simulations show that these changes could increase the level of micro-turbulence and thus enhance further the penetration of pellet-deposited particles towards the core. Post-pellet dynamics of the density profile is characterised by the pellet retention time τpel. It is shown that τpel correlates with the status of the edge transport barrier (L-mode or H-mode) and decreases rapidly for pellet deposition radius rpel approaching the plasma edge. For ELMy H-mode and ITER-like pellets, rpel ≈ 0.8a, the pellet retention time is about 20% of the energy confinement time. The fuelling requirement by the pellets for ITER is discussed.

  4. Study of improved confinement by a stepwise increase of the input heating power for tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Asif, Muhammad; Mohamed, Mabruka; Kim, Eun-Jin

    2016-09-01

    This paper is an extension of the brief study by Sarah Douglas et al. [Phys. Plasmas 20 (2013) 114504] where in the study a sinusoidal perturbation of the heating power has been studied. In this paper a stepwise increase of the heating power and its influence on the L-H transition are studied. Using a function, Atanh(t/T) for the transition of input heating power for tokamak plasmas, i.e. the addition of the perturbation, Atanh(t/T), to constant power q0 is shown to promote the confinement, leading to the L-H transition at a lower value of q0, as compared to the case of constant q0 without the Atanh(t/T) perturbation. It is seen that the input heating power Q that consists of constant part q0 in addition to a function Atanh(t/T) provides the L-H transition for relatively small A and much wider range values of 1/T as compared to Sarah Douglas et al. [Phys. Plasmas 20 (2013) 114504].

  5. Neoclassical toroidal plasma viscosity in the vicinity of the magnetic axis in tokamaks with broken symmetry

    NASA Astrophysics Data System (ADS)

    Shaing, K. C.; Lee, H.; Seol, J.; Aydemir, A. Y.

    2015-08-01

    Theory for neoclassical toroidal plasma viscosity in the low collisionality regime is extended to the vicinity of the magnetic axis in tokamaks with broken symmetry. The toroidal viscosity is induced by particles drifting off the perturbed magnetic surface under the influence of the symmetry breaking magnetic field. In the region away from the magnetic axis, the drift orbit dynamics is governed by the bounce averaged drift kinetic equation in the low collisionality regimes. In the vicinity of the magnetic axis, it is the drift kinetic equation, averaged over the trapped particle orbits, i.e., potato orbits, that governs the drift dynamics. The orbit averaged drift kinetic equation is derived when collision frequency is low enough for trapped particles to complete their potato trajectories. The resultant equation is solved in the 1 /ν regime to obtain transport fluxes and, thus, toroidal plasma viscosity through flux-force relation. Here, ν is the collision frequency. The viscosity does not vanish on the magnetic axis, and has the same scalings as that in the region away from magnetic axis, except that the fraction of bananas is replaced by the fraction of potatoes. It also has a weak radial dependence. Modeling of plasma flow velocity V for the case where the magnetic surfaces are broken is also discussed.

  6. Injection of electrons with predominantly perpendicular energy into an area of toroidal field ripple in a tokamak plasma to improve plasma confinement

    DOEpatents

    Ono, Masayuki; Furth, Harold

    1993-01-01

    An electron injection scheme for controlling transport in a tokamak plasma. Electrons with predominantly perpendicular energy are injected into a ripple field region created by a group of localized poloidal field bending magnets. The trapped electrons then grad-B drift vertically toward the plasma interior until they are detrapped, charging the plasma negative. Calculations indicate that the highly perpendicular velocity electrons can remain stable against kinetic instabilities in the regime of interest for tokamak experiments. The penetration distance can be controlled by controlling the "ripple mirror ratio", the energy of the injected electrons, and their v.sub..perp. /v.sub.51 ratio. In this scheme, the poloidal torque due to the injected radial current is taken by the magnets and not by the plasma. Injection is accomplished by the flat cathode containing an ECH cavity to pump electrons to high v.sub..perp..

  7. Advanced limiter test (ALT-1) in the TEXTOR tokamak: concept and experimental design

    SciTech Connect

    Conn, R.W.; Grontz, S.P.; Prinja, A.K.; Gauster, W.B.; Malinowski, H.E.; Pontau, A.E.; Blewer, R.S.; Whitley, J.B.; Dippel, K.H.; Fuchs, G.

    1983-01-01

    The concept and experimental design of a pump-limiter for the TEXTOR tokamak is described. The module is constructed of stainless steel with a compound curvature head designed to limit the maximum heat flux to 300 W/cm/sup 2/. The head is made of TiC-coated graphite containing a variable-aperture slot to admit plasma to a deflector plate for ballistic pumping action. The assembly is actively pumped using Zr-Al getters with an estimated hydrogen pumping speed of 3 x 10/sup 4/ 1/s. The aspect ratio of the pump duct and the length of the plasma channel are both variable to permit study of plasma plugging, ballistic scattering, and enhanced gas-conduction effects. The module can be moved radially by 10 cm to permit its operation either as the primary or secondary limiter. Major diagnostics include Langmuir and solid state probes, bolometers, infrared thermography, thermocouples, ion gauges, manometers, and a gas mass analyzer.

  8. Multiscale gyrokinetics for rotating tokamak plasmas: fluctuations, transport and energy flows.

    PubMed

    Abel, I G; Plunk, G G; Wang, E; Barnes, M; Cowley, S C; Dorland, W; Schekochihin, A A

    2013-11-01

    This paper presents a complete theoretical framework for studying turbulence and transport in rapidly rotating tokamak plasmas. The fundamental scale separations present in plasma turbulence are codified as an asymptotic expansion in the ratio ε = ρi/α of the gyroradius to the equilibrium scale length. Proceeding order by order in this expansion, a set of coupled multiscale equations is developed. They describe an instantaneous equilibrium, the fluctuations driven by gradients in the equilibrium quantities, and the transport-timescale evolution of mean profiles of these quantities driven by the interplay between the equilibrium and the fluctuations. The equilibrium distribution functions are local Maxwellians with each flux surface rotating toroidally as a rigid body. The magnetic equilibrium is obtained from the generalized Grad-Shafranov equation for a rotating plasma, determining the magnetic flux function from the mean pressure and velocity profiles of the plasma. The slow (resistive-timescale) evolution of the magnetic field is given by an evolution equation for the safety factor q. Large-scale deviations of the distribution function from a Maxwellian are given by neoclassical theory. The fluctuations are determined by the 'high-flow' gyrokinetic equation, from which we derive the governing principle for gyrokinetic turbulence in tokamaks: the conservation and local (in space) cascade of the free energy of the fluctuations (i.e. there is no turbulence spreading). Transport equations for the evolution of the mean density, temperature and flow velocity profiles are derived. These transport equations show how the neoclassical and fluctuating corrections to the equilibrium Maxwellian act back upon the mean profiles through fluxes and heating. The energy and entropy conservation laws for the mean profiles are derived from the transport equations. Total energy, thermal, kinetic and magnetic, is conserved and there is no net turbulent heating. Entropy is produced

  9. Modification of tokamak edge plasma turbulence and transport by biasing and resonant helical magnetic field.

    PubMed

    Lafouti, Mansoureh; Ghoranneviss, Mahmood; Meshkani, Sakineh; Salar Elahi, Ahmad

    2013-05-01

    In this paper, both Resonant Helical magnetic Field (RHF) and limiter biasing have been applied to the tokamak. We have investigated their effects on the turbulence and transport of the particles at the edge of the plasma. The biased limiter voltage has been fixed at 200 V and RHF has L = 2 and L = 3. Also, the effects of the time order of the application of RHF and biasing to the tokamak have been explored. The experiment has been performed under three conditions. At first, the biasing and RHF were applied at t = 15 ms and at t = 20 ms. In the next step, RHF and biasing were applied at t = 15 ms and t = 20 ms, respectively. Finally, both of them were turned on at t = 15 ms until the end of the shot. For this purpose, the ion saturation current (I(sat)) and the floating potential (V(f)) have been measured by the Langmuir probe at r/a = 0.9. Moreover, the power spectra of I(sat) and floating potential gradient (∇V(f)), the coherency, the phase between them, and the particle diffusion coefficient have been calculated. The density fluctuations of the particles have been measured by the Rake probe and they have been analyzed with the Probability Distribution Function (PDF) technique. Also the particle diffusion coefficient has been determined by the Fick's law. The results show that, when RHF and biasing were applied at the same time to the plasma (during flatness region of plasma current), the radial particle density gradient, the radial particle flux, and the particle diffusion coefficient decrease about 50%, 60%, and 55%, respectively, compared to the other conditions. For more precision, the average values of the particle flux and the particle density gradient were calculated in the work. When the time is less than 15 ms, the average values of the particle flux and the particle density gradient are identical under all conditions, but in the other time interval they change. They reduce with the simultaneous application of biasing and RHF. The same results obtain

  10. Plasma Heating: An Advanced Technology

    NASA Technical Reports Server (NTRS)

    1994-01-01

    The Mercury and Apollo spacecraft shields were designed to protect astronauts from high friction temperatures (well over 2,000 degrees Fahrenheit) when re-entering the Earth's atmosphere. It was necessary to test and verify the heat shield materials on Earth before space flight. After exhaustive research and testing, NASA decided to use plasma heating as a heat source. This technique involves passing a strong electric current through a rarefied gas to create a plasma (ionized gas) that produces an intensely hot flame. Although NASA did not invent the concept, its work expanded the market for commercial plasma heating systems. One company, Plasma Technology Corporation (PTC), was founded by a member of the team that developed the Re-entry Heating Simulator at Ames Research Center (ARC). Dr. Camacho, President of PTC, believes the technology has significant environmental applications. These include toxic waste disposal, hydrocarbon, decomposition, medical waste disposal, asbestos waste destruction, and chemical and radioactive waste disposal.

  11. Two dimensional electron cyclotron emission imaging study of electron temperature profiles and fluctuations in Tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Deng, Bihe

    An innovative plasma diagnostic technique, electron cyclotron emission imaging (ECEI), was successfully developed and implemented on the TEXT-U and RTP tokamaks for the study of plasma electron temperature profiles and fluctuations. Due to the high spatial and temporal resolution of this new diagnostic, plasma filamentation was observed during high power electron cyclotron resonance heating (ECRH) in TEXT-U, and was identified as multiple rotating magnetic islands. In RTP, under special plasma conditions, evidence for magnetic bubbling was first observed, which is characterized by the flattening of the electron temperature and pressure profiles over a small annular region of about 1-2 cm extent near the q = 2 surface. More important results arose from the detailed study of the broadband plasma turbulence in TEXT-U and RTP. With the first measurements of poloidal wavenumbers and dispersion relations, turbulent Te fluctuations in the confinement region of TEXT-U plasmas were identified as electron drift wave turbulence. The fluctuation amplitude is found to follow the mixing length scaling, and the fluctuation-induced conducted- heat flux can account for the observed anomalous energy transport in TEXT-U. In RTP, detailed ECEI study of broadband Te fluctuations has shown that many characteristics of the observed fluctuations are consistent with the predictions of toroidal ηi mode theory. These include the global dependence of the fluctuation frequency and amplitude on the plasma density and current. The measured isotope and impurity scalings quantitatively match the predictions of toroidal ηi mode theory. The ECEI measurements in combination with ECRH modification of T e profiles argue against the Te gradients serving as the driving force of the turbulence. With the detailed 2- D measurements of the fluctuation distribution over the plasma minor cross-section, large scale, coherent structures similar to the eigenmode structures predicted by toroidal ηi mode theory

  12. Compressional Alfvén and ion-ion hybrid waves in tokamak plasmas with two ion species

    NASA Astrophysics Data System (ADS)

    Oliver, H. J. C.; Sharapov, S. E.; Akers, R.; Klimek, I.; Cecconello, M.

    2014-12-01

    Compressional Alfvén and ion-ion hybrid waves excited by energetic beam ions are studied in plasmas with two ion species. In our experiment, a hydrogen-deuterium (H-D) plasma is used to produce instabilities similar to those likely to be present in the burning deuterium-tritium plasmas of future tokamaks. Modes are suppressed in the deuterium cyclotron frequency range with increasing hydrogen gas puffing. In plasmas with H/D concentrations of 2.57 or higher, short-lived modes with small and predominantly negative toroidal mode numbers are observed at frequencies ω/ωβD0 ≈ 2.25, where ωβD0 = ωβD(R0) is the on-axis deuterium cyclotron frequency. These are the highest mode frequencies yet detected in the ion cyclotron range in a spherical tokamak. Modeling of the transparency regions and plasma resonances using the cold plasma dispersion relation explains the observed features. Mode conversion at ion-ion hybrid resonances and subsequent kinetic damping is believed to be responsible for mode suppression. The high frequency modes are present due to excitation by wave-particle resonances within the transparency region for high hydrogen concentrations. The absence of other wave-particle resonances explains significant features of our experiment. This technique has possible applications in plasma heating, current drive and real-time diagnosis of relative ion concentration in the plasma core.

  13. Measurement of plasma diamagnetism in the SINP tokamak by a flux loop system inside the vacuum vessel

    NASA Astrophysics Data System (ADS)

    Saha, S. K.; Kumar, R.; Hui, A. K.

    2001-11-01

    Plasma diamagnetism has been measured in the SINP tokamak by a toroidal flux loop placed inside the vacuum vessel. The flux due to the strong toroidal field has been compensated for by a coplaner annular loop which encircles but does not contain the plasma column. The influence of the eddy currents in the vacuum vessel and the conducting shell in these loops has been calculated analytically by a circuit model using the theory of linear networks and compensated accordingly. This method has been shown to yield an almost exact compensation for toroidal flux (˜0.01%) as well as pickups from other fields. Typical results with plasma shots have been presented.

  14. Transport driven plasma flows in the scrape-off layer of ADITYA Tokamak in different orientations of magnetic field

    SciTech Connect

    Sangwan, Deepak; Jha, Ratneshwar; Brotankova, Jana; Gopalkrishna, M. V.

    2014-06-15

    Parallel plasma flows in the scrape-off layer of ADITYA tokamak are measured in two orientations of total magnetic field. In each orientation, experiments are carried out by reversing the direction of the toroidal magnetic field and the plasma current. The transport-driven component is determined by averaging flow Mach numbers, measured in two directions of the toroidal magnetic field and the plasma current for the same orientation. It is observed that there is a significant transport-driven component in the measured flow and the component depends on the field orientation.

  15. Collisional Damping of Electron Bernstein Waves and its Mitigation by Evaporated Lithium Conditioning in Spherical-Tokamak Plasmas

    SciTech Connect

    Diem, S. J.; Caughman, J. B.; Taylor, G.; Efthimion, P. C.; Kugel, H.; LeBlanc, B. P.; Phillips, C. K.; Preinhaelter, J.; Urban, J.

    2009-07-03

    The first experimental verification of electron Bernstein wave (EBW) collisional damping, and its mitigation by evaporated Li conditioning, in an overdense spherical-tokamak plasma has been observed in the National Spherical Torus Experiment (NSTX). Initial measurements of EBW emission, coupled from NSTX plasmas via double-mode conversion to O-mode waves, exhibited <10% transmission efficiencies. Simulations show 80% of the EBW energy is dissipated by collisions in the edge plasma. Li conditioning reduced the edge collision frequency by a factor of 3 and increased the fundamental EBW transmission to 60%.

  16. Collisional damping of electron bernstein waves and its mitigation by evaporated lithium conditioning in spherical-tokamak plasmas.

    PubMed

    Diem, S J; Taylor, G; Caughman, J B; Efthimion, P C; Kugel, H; LeBlanc, B P; Phillips, C K; Preinhaelter, J; Sabbagh, S A; Urban, J

    2009-07-01

    The first experimental verification of electron Bernstein wave (EBW) collisional damping, and its mitigation by evaporated Li conditioning, in an overdense spherical-tokamak plasma has been observed in the National Spherical Torus Experiment (NSTX). Initial measurements of EBW emission, coupled from NSTX plasmas via double-mode conversion to O-mode waves, exhibited <10% transmission efficiencies. Simulations show 80% of the EBW energy is dissipated by collisions in the edge plasma. Li conditioning reduced the edge collision frequency by a factor of 3 and increased the fundamental EBW transmission to 60%.

  17. High-pressure duo-multichannel soft x-ray spectrometer for tokamak plasma diagnostics

    SciTech Connect

    Schwob, J.L.; Wouters, A.W.; Suckewer, S.

    1987-03-01

    A high-resolution, time-resolving soft X-ray multichannel spectrometer (SOXMOS) that permits the simultaneous measurement of emission in two different spectral ranges has been developed and tested extensively for tokamak plasma diagnostics. The basic instrument is a high-resolution, interferometrically adjusted, extreme grazing incidence Schwob-Fraenkel duochromator. The instrument is equipped with two multichannel detectors that are adjusted interferometrically and scan along the Rowland circle. Each consists of an MgF/sub 2/ coated, funneled microchannel plate, associated with a phosphor screen image intensifier that is coupled to a 1024-element photodiode array by a flexible fibrer optic conduit. The total wavelength coverage of the instrument is 5 to 340/sup 0/ A with a measured resolution (FWHM) of about 0.2 A when equipped with a 600 g/mm grating, and 5 to 85 A with a resolution of about 0.06 A using a 2400 g/mm grating. The simultaneous spectral coverage of each detector varies from 15 A at the short wavelength limit to 70 A at the long wavelength limit with the lower dispersion grating. The minimum read-out time for a full spectral portion is 17 ms, but several individual lines can be measured with 1 ms time resolution by selected pixel readout. Higher time resolution can be achieved by replacing one multichannel detector with a single channel electron multiplier detector. Examples of data from the PLT and TFTR tokamaks are presented to illustrate the instrument's versatility, high spectral resolution, and high signal-to-noise ratio even in the 10 A region. 44 refs., 20 figs.

  18. ITER Plasma at Electron Cyclotron Frequency Domain: Tokamak Core Plasma Diagnostics Based on the Synergy of Stimulated Raman and Brillouin Scatterings

    NASA Astrophysics Data System (ADS)

    Stefan, V. Alexander

    2012-10-01

    A novel plasma diagnostic method is proposed based on the synergy of stimulated Raman and Brillouin scatterings. A nonlinear plasma mode is excited in a 4-wave coupling,footnotetextV. Alexander STEFAN, Nonlinear Electromagnetic Radiation Plasma Interactions, (S-U-Press, 2008). leading to the appearance of suprathermal electrons and accelerated ions at the plasma edgefootnotetextV. Alexander Stefan, Abstract: D1.00018 : ITER Plasma at Electron Cyclotron Frequency Domain: Stimulated Raman Scattering off Gould-Trivelpiece Modes and Generation of Suprathermal Electrons and Energetic Ions; Bulletin of the American Physical Society APS April Meeting 2011 Volume 56, Number 4. with the parameters directly dependent on the plasma parameters in the core of tokamak. Accordingly, plasma diagnostic in the core region, (ion temperature), can be performed by the diagnostics of suprathermal electrons and accelerated ions at the edge plasma.

  19. Spectroscopic imaging system for quantitative analysis of the divertor plasma of the Tokamak de Varennes

    SciTech Connect

    Meo, F.; Stansfield, B.L.; Chartre, M.; de Villers, P.; Marchand, R.; Ratel, G.

    1997-09-01

    A toroidally viewing spectroscopic imaging system has been developed for the Tokamak de Varennes providing measurements of the poloidal distribution of the absolute radiated power of deuterium and impurity species in the upper divertor region. Real time digitization is achieved using a low cost PC based digital imaging system. This system is used to obtain measurements of the divertor strike point as well as the shape of the flux surfaces in the divertor. The diagnostic{close_quote}s excellent spatial resolution and toroidal view provides an opportunity to quantitatively compare the measured two dimensional (2D) radiated power distribution to that calculated from 2D Monte Carlo transport codes. These 2D images provide unique and valuable information on the physics of local plasma interactions with divertor components and particle transport in a closed divertor. Additionally, by using two cameras simultaneously, the line ratio technique can be applied to the images to estimate plasma parameters in the divertor. {copyright} {ital 1997 American Institute of Physics. }

  20. Transport analysis of high radiation and high density plasmas in the ASDEX Upgrade tokamak

    NASA Astrophysics Data System (ADS)

    Casali, L.; Bernert, M.; Dux, R.; Fischer, R.; Kallenbach, A.; Kurzan, B.; Lang, P.; Mlynek, A.; McDermott, R. M.; Ryter, F.; Sertoli, M.; Tardini, G.; Zohm, H.

    2014-12-01

    Future fusion reactors, foreseen in the "European road map" such as DEMO, will operate under more demanding conditions compared to present devices. They will require high divertor and core radiation by impurity seeding to reduce heat loads on divertor target plates. In addition, DEMO will have to work at high core densities to reach adequate fusion performance. The performance of fusion reactors depends on three essential parameters: temperature, density and energy confinement time. The latter characterizes the loss rate due to both radiation and transport processes. The DEMO foreseen scenarios described above were not investigated so far, but are now addressed at the ASDEX Upgrade tokamak. In this work we present the transport analysis of such scenarios. Plasma with high radiation by impurity seeding: transport analysis taking into account the radiation distribution shows no change in transport during impurity seeding. The observed confinement improvement is an effect of higher pedestal temperatures which extend to the core via stiffness. A non coronal radiation model was developed and compared to the bolometric measurements in order to provide a reliable radiation profile for transport calculations. High density plasmas with pellets: the analysis of kinetic profiles reveals a transient phase at the start of the pellet fuelling due to a slower density build up compared to the temperature decrease. The low particle diffusion can explain the confinement behaviour.

  1. Impact of the background toroidal rotation on particle and heat turbulent transport in tokamak plasmas

    SciTech Connect

    Camenen, Y.; Peeters, A. G.; Casson, F. J.; Hornsby, W. A.; Snodin, A. P.; Angioni, C.; Strintzi, D.

    2009-01-15

    Recent developments in the gyrokinetic theory have shown that, in a toroidal device, the Coriolis drift associated with the background plasma rotation significantly affects the small scale instabilities [A. G. Peeters et al., Phys. Rev. Lett. 98, 265003 (2007)]. The later study, which focuses on the effect of the Coriolis drift on toroidal momentum transport is extended in the present paper to heat and particle transport. It is shown numerically using the gyrokinetic flux-tube code GKW[A. G. Peeters and D. Strintzi, Phys. Plasmas 11, 3748 (2004)], and supported analytically, that the Coriolis drift and the parallel dynamics play a similar role in the coupling of density, temperature, and velocity perturbations. The effect on particle and heat fluxes increases with the toroidal rotation (directly) and with the toroidal rotation gradient (through the parallel mode structure), depends on the direction of propagation of the perturbation, increases with the impurity charge number and with the impurity mass to charge number ratio. The case of very high toroidal rotation, relevant to spherical tokamaks, is investigated by including the effect of the centrifugal force in a fluid model. The main effect of the centrifugal force is to decrease the local density gradient at the low field side midplane and to add an extra contribution to the fluxes. The conditions for which the inertial terms significantly affect the heat and particle fluxes are evidenced.

  2. Plasma diagnostics in spherical tokamaks with silicon charged-particle detectors

    NASA Astrophysics Data System (ADS)

    Netepenko, A.; Boeglin, W. U.; Darrow, D. S.; Ellis, R.; Sibilia, M. J.

    2016-11-01

    Detection of charged fusion products, such as protons and tritons resulting from D(d, p) t reactions, can be used to determine the position and time dependent fusion reaction rate profile in spherical tokamak plasmas with neutral beam heating. We have developed a prototype instrument consisting of 6 ion-implanted-silicon surface barrier detectors combined with collimators in such a way that each detector can accept 3 MeV protons and 1 MeV tritons and thus provides a curved view across the plasma cross section. The combination of the results from all six detectors will provide information on the spatial distribution of the fusion reaction rate. The expected time resolution of about 1 ms makes it possible to study changes in the reaction rate due to slow variations in the neutral beam density profile, as well as rapid changes resulting from MHD instabilities. Details of the new instrument, its data acquisition system, simulation results, and electrical noise testing results are discussed in this paper. First experimental data are expected to be taken during the current experimental campaign at NSTX-U.

  3. Energetic-particle-induced electromagnetic geodesic acoustic mode in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Wang, Lingfeng; Dong, J. Q.; He, Zhixiong; He, Hongda; Shen, Y.

    2014-07-01

    Energetic-particle-induced kinetic electromagnetic geodesic acoustic modes (EKEGAMs) are numerically studied in low β (=plasma pressure/magnetic pressure) tokamak plasmas. The parallel component of the perturbed vector potential is considered along with the electrostatic potential perturbation. The effects of finite Larmor radius and finite orbit width of the bulk and energetic ions as well as electron parallel dynamics are all taken into account in the dispersion relation. Systematic harmonic and ordering analysis are performed for frequency and growth rate spectra of the EKEGAMs, assuming ( k ρ i ) ˜ q - 3 ˜ β ≪ 1, where q, k, and ρi are the safety factor, radial component of the EKEGAMs wave vector, and the Larmor radius of the ions, respectively. It is found that there exist critical βh/βi values, which depend, in particular, on pitch angle of energetic ions and safety factor, for the mode to be driven unstable. The EKEGAMs may also be unstable for pitch angle λ 0 B < 0.4 in certain parameter regions. Finite β effect of the bulk ions is shown to have damping effect on the EKEGAMs. Modes with higher radial wave vectors have higher growth rates. The damping from electron dynamics is found decreasing with decrease of the temperature ratio Te/Ti. The modes are easily to be driven unstable in low safety factor q region and high temperature ratio Th/Ti region. The harmonic features of the EKEGAMs are discussed as well.

  4. Core turbulent transport in tokamak plasmas: bridging theory and experiment with QuaLiKiz

    NASA Astrophysics Data System (ADS)

    Bourdelle, C.; Citrin, J.; Baiocchi, B.; Casati, A.; Cottier, P.; Garbet, X.; Imbeaux, F.; Contributors, JET

    2016-01-01

    Nonlinear gyrokinetic codes allow for detailed understanding of tokamak core turbulent transport. However, their computational demand precludes their use for predictive profile modeling. An alternative approach is required to bridge the gap between theoretical understanding and prediction of experiments. A quasilinear gyrokinetic model, QuaLiKiz (Bourdelle et al 2007 Phys. Plasmas 14 112501), is demonstrated to be rapid enough to ease systematic interface with experiments. The derivation and approximation of this approach are reviewed. The quasilinear approximation is proven valid over a wide range of core plasma parameters. Examples of profile prediction using QuaLiKiz coupled to the CRONOS integrated modeling code (Artaud et al 2010 Nucl. Fusion 50 043001) are presented. QuaLiKiz is being coupled to other integrated modeling platforms such as ETS and JETTO. QuaLiKiz quasilinear gyrokinetic turbulent heat, particle and angular momentum fluxes are available to all users. It allows for extensive stand-alone interpretative analysis and for first principle based integrated predictive modeling.

  5. A study of tearing modes via electron cyclotron emission from tokamak plasmas

    SciTech Connect

    Ren, C.

    1998-07-01

    This thesis studies several tearing mode problems from both theoretical and experimental points of view. A major part of this thesis is to demonstrate that Electron Cyclotron Emission (ECE) is an excellent diagnostic for studying an MHD mode structure and its properties in a tokamak plasma. It is shown that an MHD mode can be detected from the electron temperature fluctuations measured by ECE. The amplitude and phase profiles of the fluctuations contain detailed information about the mode structure. The ECE fluctuation phase profile indicates the magnetic island deformation due to the combination of sheared flow and viscosity. A model is presented to relate qualitatively the observed phase gradient to the local magnetic field, flow velocity shear and viscosity in a 2D slab geometry, using an ideal Ohm`s law and the plasma momentum equation including flow and viscosity. Numerical solution of the resultant Grad-Shafranov-like equation describing the deformed island shows that the experimentally observed value of the phase gradient can be obtained under realistic parameters for the shear in the flow velocity and viscosity. A new approach to the tearing mode stability boundary and saturation level is also presented.

  6. Analytical and numerical study of the transverse Kelvin-Helmholtz instability in tokamak edge plasmas

    NASA Astrophysics Data System (ADS)

    Myra, J. R.; D'Ippolito, D. A.; Russell, D. A.; Umansky, M. V.; Baver, D. A.

    2015-11-01

    Sheared flows perpendicular to the magnetic field can be driven by Reynolds stresses or ion pressure gradient effects and can potentially influence the stability and turbulent saturation level of edge plasma modes. On the other hand, such flows are subject to the transverse Kelvin-Helmholtz (KH) instability. Here, we first review the linear theory of KH instabilities with an analytic model in the asymptotic limit of long wavelengths compared with the flow scale length. The analytic model treats sheared ExB flows, ion diamagnetism, density gradients and parallel currents in a slab geometry, enabling a unified summary of some well-known results. Second, the important role of realistic toroidal geometry is explored numerically using the 2DX eigenvalue code for KH modes both inside and outside the separatrix. Preliminary results indicate that KH modes are often stable in edge tokamak plasmas, but can also be unstable in some interesting cases. Implications for reduced edge turbulence modeling codes will be discussed. Work supported by US DOE grant DE-FG02-97ER54392.

  7. Pre-Results of the Real-Time ODIN Validation on MARTe Using Plasma Linearized Model in FTU Tokamak

    NASA Astrophysics Data System (ADS)

    Sadeghi, Yahya; Boncagni, Luca

    2012-06-01

    MARTe is a modular framework for real-time control aspects. At present time there are several MARTe systems under development at Frascati Tokamak Upgrade (Boncagni et al. in First steps in the FTU migration towards a modular and distributed real time control architecture based on MARTe and RTNet, 2010) such as the LH power percentage system, the gas puffing control system, the real-time ODIN plasma equilibrium reconstruction system and the position/current feedback control system (in a design phase) (Boncagni et al. in J Fusion Eng Design). The real-time reconstruction of magnetic flux in FTU tokamak is an important issue to estimate some quantities that can be use to control the plasma. This paper addresses the validation of real-time implementation of that task on MARTe.

  8. A comparative study of ideal kink stability in two reactor-relevant tokamak plasma configurations with negative and positive triangularity

    NASA Astrophysics Data System (ADS)

    Ren, Jing; Liu, Yueqiang; Liu, Yue; Medvedev, S. Yu; Wang, Zhirui; Xia, Guoliang

    2016-11-01

    The effects of an ideal/resistive conducting wall, the drift kinetic resonances, as well as the toroidal plasma flow, on the stability of the ideal external kink mode are numerically investigated for a reactor-relevant tokamak plasma with strongly negative triangularity (NTR) shaping. Comparison is made for a similar plasma equilibrium, but with positive triangularity (PTR). It is found that the ideal wall stabilization is less efficient for the kink stabilization in the NTR plasma due to a less ‘external’ eigenmode structure compared to the PTR plasma. The associated plasma displacement in the NTR plasma does not ‘balloon’ near the outboard mid-plane, as is normally the case for the pressure-driven kink-ballooning instability in PTR plasmas, but being more pronounced near the X-points. The toroidal flow plays a similar role for the kink stability for both NTR and PTR plasmas. The drift kinetic damping is less efficient for the ideal external kink mode in the NTR plasma, despite a somewhat larger fraction of the particle trapping near the plasma edge compared to the PTR equilibrium. However, the drift kinetic damping of the resistive wall mode (RWM) in the NTR plasma is generally as efficient as that of the PTR plasma, although the RWM window, in terms of the normalized pressure, is narrower for the NTR plasma.

  9. Tokamak Systems Code

    SciTech Connect

    Reid, R.L.; Barrett, R.J.; Brown, T.G.; Gorker, G.E.; Hooper, R.J.; Kalsi, S.S.; Metzler, D.H.; Peng, Y.K.M.; Roth, K.E.; Spampinato, P.T.

    1985-03-01

    The FEDC Tokamak Systems Code calculates tokamak performance, cost, and configuration as a function of plasma engineering parameters. This version of the code models experimental tokamaks. It does not currently consider tokamak configurations that generate electrical power or incorporate breeding blankets. The code has a modular (or subroutine) structure to allow independent modeling for each major tokamak component or system. A primary benefit of modularization is that a component module may be updated without disturbing the remainder of the systems code as long as the imput to or output from the module remains unchanged.

  10. Particle simulations on ion loss at the edge of a tokamak plasma with the radial electric fields

    SciTech Connect

    Ido, Suhnji; Kashiwagi, Mieko

    1995-04-01

    Particle orbit simulations are carried out to study the ion orbits and loss at the edge of a tokamak plasma. The ion loss conditions are examined as a function of {upsilon}{sub PLL}/{upsilon}{sub 0} and the distance of ion launching points form the magnetic separatrix. The simulation results are compared with the theoretical ones. Good agreements and detailed features are shown in the simulations. 8 refs., 6 figs.

  11. Numerical study of compressibility effects on the reversed shear Alfvén eigenmode in tokamak plasma

    SciTech Connect

    Yu, Limin; Zhang, Xianmei; Sheng, Zheng-Mao

    2013-08-15

    Compressibility effects on the reversed shear Alfvén eigenmode in tokamak plasma are studied numerically. It is shown that compressibility is favorable for the existence of the reversed shear Alfvén eigenmode even without the pressure gradient, and the frequency of the reversed shear Alfvén eigenmode is modified by the geodesic frequency, which is consistent with an analytical theory.

  12. Advances and Challenges in Computational Plasma Science

    SciTech Connect

    W.M. Tang; V.S. Chan

    2005-01-03

    Scientific simulation, which provides a natural bridge between theory and experiment, is an essential tool for understanding complex plasma behavior. Recent advances in simulations of magnetically-confined plasmas are reviewed in this paper with illustrative examples chosen from associated research areas such as microturbulence, magnetohydrodynamics, and other topics. Progress has been stimulated in particular by the exponential growth of computer speed along with significant improvements in computer technology.

  13. Characterization of Plasma Gun with TiH2/C60 Cartridge for Disruption Mitigation in Tokamaks

    NASA Astrophysics Data System (ADS)

    Bogatu, I. N.; Thompson, J. R.; Galkin, S. A.; Kim, J. S.; HyperV Technologies Corp. Team

    2011-10-01

    Impurity injection for disruption mitigation in tokamaks must be faster than growth time of plasma instabilities, requires sufficient mass to get critical electron density, high penetrability, and large assimilation fraction in the core plasma, with rapid impurity redistribution over the whole plasma. FAR-TECH, Inc. proposed the innovative idea to use hyper-velocity (>30 km/s), high-density (>1023 m-3) C60/C plasma jets with high ram pressure to deliver the impurity mass in <1 ms. For this purpose C60 powder explosively sublimated into molecular gas, from a solid state, pulsed power driven TiH2/C60 injector cartridge is ionized and accelerated in a plasma accelerator. We report the complete characterization of the TiH2/C60 cartridge with 5 kJ capacitive driver which demonstrated the capability of producing >30 mg of C60 gas in <0.5 ms. In addition we present the construction and testing status of a 100 kJ coaxial plasma gun (~35 cm length) prototype with TiH2/C60 cartridge for a small scale, proof-of-principle experiment on a tokamak. Work supported by the US DOE DE-FG02-08ER85196 grant.

  14. Development of advanced superconducting coil technologies for the National Centralized Tokamak

    NASA Astrophysics Data System (ADS)

    Kizu, K.; Miura, Y. M.; Tsuchiya, K.; Ando, T.; Koizumi, N.; Matsui, K.; Sakasai, A.; Tamai, H.; Matsukawa, M.; Ishida, S.; Okuno, K.

    2005-11-01

    Advanced technologies for fabrication of superconducting coils have been developed for the National Centralized Tokamak which is based on modification of JT-60. One of the technologies developed is the application of the react-and-wind (R&W) method of fabrication of a Nb3Al D-shaped coil. The bending strain of 0.4% due to the R&W method did not affect the critical current characteristics. This finding indicates the possibilities that the manufacturing cost of large size coils can be reduced further by downsizing the heat treatment furnace, and large complicated shape coils can be manufactured by using the Nb3Al conductor. Another technology is an advanced winding technique for the reduction of the ac losses of Nb3Sn coils by loading bending strain on the conductor. It was found that 0.2% bending strain is enough to reduce the ac losses to one-fifth at the virgin state. The newly developed NbTi conductor attained both (i) low ac loss of 116 ms in coupling time constant and (ii) low cost owing to the stainless steel wrap of the sub-cables and Ni plated NbTi strands with 11 µm filaments.

  15. Response to 'Comment on 'Continuum modes in rotating plasmas: General equations and continuous spectra for large aspect ratio tokamaks' '[Phys. Plasmas 19, 064701 (2012)

    SciTech Connect

    Lakhin, V. P.; Ilgisonis, V. I.

    2012-06-15

    The equations for the continuous spectra derived in our paper [V. P. Lakhin and V. I. Ilgisonis, Phys. Plasmas 18, 092103 (2011)] can be reduced to the matrix form used by Goedbloed et al.[Phys. Plasmas 11, 28 (2004)]. It is shown that the assumptions made in our paper provide the elliptic flow regime and guarantee the existence of plasma equilibrium with nested magnetic surfaces of circular cross-section. The new results on magnetohydrodynamic instabilities of such tokamak equilibria obtained in our paper but absent in the paper by Goedbloed et al. are emphasized.

  16. Magnetic confinement experiment. I: Tokamaks

    SciTech Connect

    Goldston, R.J.

    1995-08-01

    Reports were presented at this conference of important advances in all the key areas of experimental tokamak physics: Core Plasma Physics, Divertor and Edge Physics, Heating and Current Drive, and Tokamak Concept Optimization. In the area of Core Plasma Physics, the biggest news was certainly the production of 9.2 MW of fusion power in the Tokamak Fusion Test Reactor, and the observation of unexpectedly favorable performance in DT plasmas. There were also very important advances in the performance of ELM-free H- (and VH-) mode plasmas and in quasi-steady-state ELM`y operation in JT-60U, JET, and DIII-D. In all three devices ELM-free H-modes achieved nT{tau}`s {approximately} 2.5x greater than ELM`ing H-modes, but had not been sustained in quasi-steady-state. Important progress has been made on the understanding of the physical mechanism of the H-mode in DIII-D, and on the operating range in density for the H-mode in Compass and other devices.

  17. Simulation of EAST vertical displacement events by tokamak simulation code

    NASA Astrophysics Data System (ADS)

    Qiu, Qinglai; Xiao, Bingjia; Guo, Yong; Liu, Lei; Xing, Zhe; Humphreys, D. A.

    2016-10-01

    Vertical instability is a potentially serious hazard for elongated plasma. In this paper, the tokamak simulation code (TSC) is used to simulate vertical displacement events (VDE) on the experimental advanced superconducting tokamak (EAST). Key parameters from simulations, including plasma current, plasma shape and position, flux contours and magnetic measurements match experimental data well. The growth rates simulated by TSC are in good agreement with TokSys results. In addition to modeling the free drift, an EAST fast vertical control model enables TSC to simulate the course of VDE recovery. The trajectories of the plasma current center and control currents on internal coils (IC) fit experimental data well.

  18. Disruption avoidance in the SINP-Tokamak by means of electrode-biasing at the plasma edge

    SciTech Connect

    Basu, Debjyoti; Pal, Rabindranath; Ghosh, Joydeep; Chattopadhyay, Prabal K.

    2013-05-15

    Control of plasma disruption by a biased edge electrode is reported in SINP-Tokamak. The features that characterize a plasma disruption are reduced with increasing bias potential. The disruption can be completely suppressed with the concomitant stabilization of observed MHD modes that are allegedly precursors of the disruption. An m = 3/n = 1 tearing mode, which apparently causes disruption can be stabilized when a negative biasing potential is applied near the edge. These changes in the disruptive behavior with edge biasing are hypothesized to be due to changes in the current density profile.

  19. Resistive reduced MHD modeling of multi-edge-localized-mode cycles in Tokamak X-point plasmas.

    PubMed

    Orain, F; Bécoulet, M; Huijsmans, G T A; Dif-Pradalier, G; Hoelzl, M; Morales, J; Garbet, X; Nardon, E; Pamela, S; Passeron, C; Latu, G; Fil, A; Cahyna, P

    2015-01-23

    The full dynamics of a multi-edge-localized-mode (ELM) cycle is modeled for the first time in realistic tokamak X-point geometry with the nonlinear reduced MHD code jorek. The diamagnetic rotation is found to be instrumental to stabilize the plasma after an ELM crash and to model the cyclic reconstruction and collapse of the plasma pressure profile. ELM relaxations are cyclically initiated each time the pedestal gradient crosses a triggering threshold. Diamagnetic drifts are also found to yield a near-symmetric ELM power deposition on the inner and outer divertor target plates, consistent with experimental measurements.

  20. Self-Consistent Simulation of Turbulence and Transport in Tokamak Edge Plasmas

    SciTech Connect

    Rognlien, T D; Umansky, M V; Xu, X Q; Cohen, R H

    2003-09-03

    The status of coupling the fluid 3D turbulence code BOUT and the fluid plasma/neutral 2D transport code UEDGE is reported, where both codes simulate the edge region of diverted tokamaks from several cm inside the magnetic separatrix to the far scrape-off layer (SOL), thereby including the magnetic X-point. Because the characteristic time scale of the turbulence is short ({approx} 10{sup -5}-10{sup -4}s) and the profile evolution time scale can be long ({approx} 10{sup -2}-10{sup -1} s owing to recycling), an iterative scheme is used that relaxes the turbulent fluxes passed from BOUT to UEDGE and the profiles from UEDGE to BOUT over many coupling steps. Each code is run on its own characteristic time scale, yielding a statistically averaged steady state. For this initial study, the ion and neutral densities and parallel velocities are evolved, while the temperature profiles are stationary. Here the turbulence code is run in the electrostatic approximation. For this example of self-consistent coupling with strong L-mode-like turbulence, the ion flux to the main-chamber exceeds that to the divertor plates.