Growth of resistive wall modes in an RFP

Experiments have been performed on the Reversatron 11 RFP to study the growth of m = l kink modes with thick and thin shells. The thick shell has a magnetic penetration time comparable to the discharge duration of 600 psec and the thin shell has a penetration time of 200 μsec. Toroidal mode numbers from n = -12 to +12 are resolved. Dimensionless growth rates γτs from 0.5 to 2.0 are found for most mode numbers. Linear theory is found to predict the important modes, if not the growth rates which are affected by nonlinearities. During the setting-up phase of the discharge the MHD dynamo modes have the largest amplitude and during the sustainment phase the external kinks are large