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(EX1/1) Progress Towards Confinement Improvement Using Current Profile Modification in the MST Reversed Field Pinch

C. B. Forest¹⁾, J. K. Anderson¹⁾, T. M. Biewer¹⁾, D. Brower²⁾, B. E. Chapman¹⁾, P. K. Chattopadhyay¹⁾, D. Craig¹⁾, N. C. Crocker¹⁾, D. J. Den Hartog¹⁾, G. Fiksel¹⁾, R. W. Harvey³⁾, Y. Jiang²⁾, N. E. Lanier¹⁾, R. O'Connell¹⁾, S. C. Prager¹⁾, E. Uchimoto⁴⁾, J. S. Sarff¹⁾, A. P. Smirnov⁵⁾, M. A. Thomas^1)
 
1) MST Group, Department of Physics, University of Wisconsin, Madison WI USA
²⁾ University of California, Los Angeles, CA USA
³⁾ CompX, Del Mar, CA USA
⁴⁾ Department of Physics and Astronomy, University of Montana, Missoula, MT USA
⁵⁾ Moscow State University, Moscow, Russia

Abstract.  Recent current profile modification experiments on the MST reversed field pinch have resulted in improved performance and elucidated the role of the current profile in determining confinement. During transient experiments in which the current profile is modified inductively, new profile measurements show that both the electron thermal diffusivity and particle diffusivity can decrease by more than an order of magnitude compared to standard plasmas. Concurrent with this improvement in energy confinement, density fluctuations associated with core-resonant tearing modes are reduced by more than an order of magnitude over the entire plasma cross-section. Edge resonant modes (poloidal mode number m=0) are shown to affect confinement and are controllable by current drive in the extreme plasma edge-indicating the significance of edge modes in addition to the core-resonant m=1 modes. Finally, experiments are underway to demonstrate new non-inductive current profile control techniques using lower hybrid waves and electron Bernstein waves.

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