Resistive wall modes in the setting-up phase of a reversed field pinch

Resistive wall modes during the setting-up phase of a reversed field pinch have been investigated in an experiment (Reversatron II [IEEE Trans. Plasma Sci. PS-16, 667 (1988)]) operated without a conducting shell. The time for the vertical field to penetrate the vacuum chamber (4 μsec) is much shorter than the rise time of the plasma current (100 μsec). The discharges, when compared to discharges in the same device with a conducting shell, have a greater resistance and lower plasma current. Magnetic probes indicate the growth of a strong ‖n‖=6 helical kink resonant with the field on axis.