Performance of the ZT-40M reversed-field pinch with an Inconel liner

Abstract

Modifications made to ZT-40 have substantially improved plasma parameters: pinch resistance has decreased by more than an order of magnitude, T/sub e/ has exceeded 300 eV, and with power crowbar operation > 20 ms steady-state discharges have been obtained. With a ..beta.. of approx. 0.1, and the assumptions of modified Bessel function magnetic-field profiles and classical ohmic heating the energy confinement time, approx. 0.2 ms, is close to that expected for the measured temperatures and discharge currents. A relaxation process (dynamo) sustains RFP profiles extending discharge lifetimes beyond the limit predicted by classical resistive diffusion. If the process continues to operate, a steady-state RFP is possible. Extension of the toroidal current risetime to the experiment's design limit (1.5 ms) indicates that RFPs can be formed at still longer risetimes with reasonable voltsecond and energy inputs facilitating the design of future experiments. These results represent a significant advance for the RFP concept toward a viable ohmic-heated magnetic-fusion system