A possible mechanism of current termination in a reversed field pinch

A rapid growth of magnetic fluctuations resulting from the m=1 and m=2 modes and succeeding stop of rotation of these modes have been found as the precursor phenomena of current termination in the STP‐3(M) [Trans. Inst. Elec. Eng. Jpn. 107‐B, 469 (1987)] reversed field pinch. By deepening the field reversal at the wall, these precursors disappear and the current duration becomes much longer. It is found that sudden current termination is caused by a rapid growth of resistive tearing modes mainly because of nonlinear coupling of the m=1 mode.