Confinement dynamics in the ZT-4-M RFP

Summary Form only given, as follows. It has been shown that typically one-third of the input power is accounted for by radiation as measured by bolometers. This radiated power fraction has been varied from 0.15 to 0.95 in impurity injection experiments with the global beta and tau /sub E/ values maintained to within a factor of two. This implies that the nonradiative confinement varied by a factor of five or more while the total confinement remained roughly the same. The fraction of the input power absorbed by fluctuations in the discharge is typically 0.2 to 0.3 in ZT-40M and correlates with the ion heating. Ion energy losses are dominated by recycling. Electrons are heated ohmically, and collisional coupling to the ions is relatively weak. Electron energy transport is dominated by a small number of energetic electrons moving along field lines to the edge. The field line wandering implied by this interpretation is consistent with the level of magnetic field fluctuation measured in the edge plasma.<>