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(EX/P4-01) Ion Heating and Profile Relaxation During Sawtooth Crashes in the MST Reversed Field Pinch

G. Fiksel1), A.F. Almagri1), J.K. Anderson1), T.M. Biewer1), A.P. Blair1), D.L. Brower2), B.E. Chapman1), D. Craig1), D.J. Den Hartog1), W.X. Ding2), C.B. Forest1), C.C. Hegna1), R. Gatto1), J. Goetz1), K.J. McCollam1), V.V. Mirnov1), R. O'Connell1), S.C. Prager1), J.C. Reardon1), J.S. Sarff1), P.W. Terry1), S.D. Terry2)
 
1) University of Wisconsin-Madison, Madison, WI, USA
2) Electrical Engineering Department, University of California-Los Angeles, CA, USA

Abstract.  Very robust and global phenomena associated with sawtooth crashes are studied in a reversed field pinch plasma. These phenomena are: anomalous ion heating, current profile relaxation, and plasma momentum profile relaxation. We have implemented new sophisticated diagnostics to characterize these processes with good spatial and temporal resolution. The majority ion temperature is measured with the Rutherford scattering diagnostic and the minority ion temperature is measured with charge exchange recombination spectroscopy. At the sawtooth crash the ion temperature almost doubles and a significant fraction of the equilibrium magnetic field energy is transferred into the ion thermal energy. The profile of the parallel current (inferred via laser polarimetry) flattens after the sawtooth crash which provides the most complete evidence of plasma relaxation toward a Taylor state. At the sawtooth crash we observe transport and relaxation both of the plasma toroidal and parallel momentum. The flattening of the parallel plasma momentum profile is in a good agreement with the theoretical predictions of two-fluid MHD.

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IAEA 2003