Studies of large-size (R = ., *, u,,,_, ,,,I.,.,.,_,..,,,.,,,,. ,.,.,,,,,,..,,,,,,_. ,..., .,,,...,,,_., ,,,,,_ ,,q, ,.m.,,,,,.,, ,,,..,m.,,,,q,_,,..i,_mt,,,ql_.HIm,,I m,,_..q_lHHIWlill_lnl'l_ll_iln n nmlmq IIImH_ __ll'ili_i'll_flqHIlaq_l _li_q_ll_m_lll_ll'_l_' }]ml I_ll_l'_i_ll_lq'll$lll_'_qll_tli_H'_l_ and superthermal electrons. Initial profile control experiments have begun using insertable biased probes and plasma guns. The toroidal field capacity of MST will be upgraded during Summer, 1993 to allow low-current tokamak operation as well as improved RFP operation.1

Studies of large-size (R = 1.5 m, a = 0.5 m), moderate current (I < 750 kA) reversed-field pinch (RFP) plasmas are carried out in the Madison Symmetric Torus in order to evaluate and improve RFP confinement_ study general toroidal plasma MHD issues, determine the medlanism of the RFP dynamo, and measure fluctuation-induced transport and anomalous ion heating. MST confinement has been improved by reduction of magnetic field errors with correction coils in the primary circuit and reduction of impurities using boronization; high densities have been achieved with hydrogen pellet injection. MHD tearing modes with poloidal mode number m = 1 and toroidal mode numbers n = 5-7 are prevalent and nonlinearly couple to produce sudden relaxations akin to tokamak sawteeth. Edge fluctuation-induced transport has been measured with a variety of insertable probes. Ions exhibit anomalous heating, with increases of ion temperature occuring during strong MHD relaxation. The RFP dynamo has been studied with attention to various possible mechanisms, including motion-EMF drive, the Hall effect,