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Weixing Ding ( 丁卫星） in collaboration with

Flow generation driven by magnetic perturbations in a toroidal plasma Intrinsic Flow from Magnetic-Fluctuation-Driven Kinetic Stress in a Magnetically-Confined Toroal Plasma. Weixing Ding ( 丁卫星） in collaboration with D. Brower, L. Lin, W.F. Bergerson, A. Almagri, B. Chapman, G. Fiksel,

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Weixing Ding ( 丁卫星） in collaboration with

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  1. Flow generation driven by magnetic perturbations in a toroidal plasmaIntrinsic Flow from Magnetic-Fluctuation-Driven Kinetic Stress in a Magnetically-Confined Toroal Plasma Weixing Ding (丁卫星） in collaboration with D. Brower, L. Lin, W.F. Bergerson, A. Almagri, B. Chapman, G. Fiksel, D.J. Den Hartog, J.S. Sarff and the MST Group Department of Physics & Astronomy, University of California Los Angeles Department of Physics, University of Wisconsin, Madison Sixth US-PRC Workshop, San Diego, CA

  2. Madison Symmetric Torus - MST MST Reversed-Field Pinch (RFP) is toroidal configuration with relatively weak toroidal magnetic field BT ( i.e., BT ~ Bp) For plasma w/o current profile control R0 = 1.5 m, a = 0.51 m, Ip ~400 kA ne ~ 1019 m-3 ,Te~Ti~400eV

  3. Ohmic discharge Ip Intrinsic Flow: self-generated during plasma discharge in the core dbq: (m,n)=(1,6) dbq: (m,n)=(0,1)

  4. Parallel Flow Spatial Profile on MST parallel flow reverses direction at r/a~0.5r/a~0.6 (Flow profile is obtained by Rutherford scattering, mode velocity and edge probe )

  5. Magnetic fluctuations play important role in RFP Plasmas Te ~ Ti ~ 400 eV m/n noise r (m) Tearing modes and broadband magnetic turbulence - island overlap leads to stochastic field dominant, core resonant modes m=1, n=6,7,8,9,…

  6. Multiple Fluctuation-Induced Effects on Flow Parallel momentum components Maxwell Stress Momentum Change Reynolds stress Kinetic stress damping Without External Momentum Sources, fluctuation-induced torques play most important role in flow generation and flow damping.

  7. Momentum flux in radial direction due to particles free streaming along fluctuating magnetic field lines: Kinetic stress （动力胁强）

  8. Multi-measurements enable us to determine the kinetic stress Investigate balance between kinetic stress and inertial term - simple momentum balance Motional Stark effect Laser (differential) interferometer ( ) Laser Faraday rotation Rutherford Scattering (bulk deuterium ions), CHERS (impurity) Thomson scattering

  9. Interferometer density fluctuations Faraday rotation magnetic field fluctuations FIR Laser Polarimeter-Interferometer System MST • chords, Dx ~ 8 cm, phase ~ 0.05 deg. degree, time response ~ 1 s + 32+8 magnetic coils toroidal-poloidal array (m,n) Ding, Brower, et al., PRL(2003),(2004),(2009), RSI(2004),(2008)

  10. 2-D Space-Time Image of Fluctuations using combined interferometry and Faraday polarimetry 2pR

  11. (1.6) mode density and magnetic fluctuation spatial profile Density fluctuations Faraday fluctuations Inversion: parameterized fitting

  12. Kinetic Stress Profile (away from sawtooth crash) r/a=0.2 (m,n)=1,6-15 kinetic stress has same sign, spatial distribution as flow profile, independent of flow.

  13. Measurements of Intrinsic Flow and Kinetic Stress during Enhanced Confinement (PPCD) During PPCD, RFP has tokamak-like confinement Intrinsic Flow PPCD Flow correlates with density and magnetic fluctuations Kinetic stress t=15-20 ms Intrinsic flow and Kinetic stress track changes in fluctuation amplitudes

  14. Advanced Faraday Rotation System on C-Mod Resistive Ballooning Tearing By Irby, Peng. Bergenson, Brower,Ding et al Time [s] Time (sec) Faraday Rotation Fluctuations are measured on C-Mod, providing new opportunity to study flow in Tokamaks

  15. Both EAST and HL-2A in China have developed Faraday rotation measurements with radial access, which allows direct measurement of radial magnetic fluctuations. Radial Magnetic Fluctuations on EAST and HL-2A To investigate the role of fast particle modes on plasma rotation.

  16. Summary • Kinetic stress, the correlated product between density fluctuations and magnetic fluctuations, acts to drive plasma flow • Kinetic stress is consistent with observed flow generation - spatial distribution, direction and amplitude of force • In PPCD plasmas with good (tokamak-like) confinement, (1) core flow is reduced and momentum confinement increases when density and magnetic fluctuations are suppressed (2) flow dynamics likely governed by additional effects (es turbulence) in addition to magnetic fluctuation driven kinetic stress .

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