Stable equilibrium configuration of reversed-field pinch with the partially-relaxed-state condition jp= αBp/μ0

The stability of a partially-relaxed-state model of the reversed-field pinch (RFP) with the condition j p = αB p /μ 0 is investigated numerically. An F-θ stability diagram obtained here suggests that, to obtain a stable high-β RFP plasma experimentally, it is necessary to operate the RFP with a relatively high field reversal ratio, F, and a medium pinch parameter, θ, e.g. F ⪅ − 1 and θ ⪅ 2.0. It is also suggested that, to confine a stable RFP plasma for long periods, the state of the RFP plasma should be kept inside a stable region in the F-θ stability diagram by field control. Numerical results on the influence of toroidal effects on stability show that the β ax –value of the marginally stable configuration with F = 0 with respect to the high-m localized modes decreases with increasing inverse aspect ratio , e.g. β ax at = 1/3 is about 70% of that at = 0 (i.e. a cylindrical plasma).