Stability condition of resistive flute mode in toroidal RFP

The stability condition of reversed field pinch (RFP) with respect to the resistive flute mode (g-mode) is obtained by reexamining the Mikhajlovskij's criterion. Axialsymmetric toroidal RFP has stability effect near the point of field reversal due to the displacement of the center of the magnetic surface relative to the magnetic axis. The permissible maximum beta value of plasma having rather small conductivity is 4.0 to 5.5 % near field reversal, or 6.2 to 8.6 % on magnetic axis. In taking account of the high conductivity corresponding to 5 eV, beta value of 20% can be permitted with the growth rate less than the field diffusion rate. (author)