Transport and fluctuations in reversed field pinches

Abstract

In the reversed field pinch various turbulent transport mechanisms might be simultaneously active, including MHD flow effects, free-streaming in a stochastic magnetic field, direct transfer of fluctuating energy to ions, and electrostatic fluctuation driven transport. By comparing fluctuations and transport in the RFP to that in the related toroidal configurations of the tokamak and stellarator, a greater understanding of toroidal confinement in general might be achieved. In addition to particle and energy transport, current transport sustains the reversed field magnetic configuration and constitutes the dynamo effect. Recent results are available from RFP experiments on electrostatic fluctuations, anomalous ion heating, the presence of free-streaming fast electrons, and the extension of these effects to plasmas of large size. The reactor promise of the RFP is based upon the conjecture that the beta value will remain high and the resistance scaling classical, as has been the case in past experiments. One might expect beta to be limited by resistive interchange turbulence. The MST, RFX, and ZTH experiments will form a sequence of devices to test this scaling conjecture to large size and large current values.