Text-U error field measured from and dynamics

摘要

A new method is described for determining error field strengths using the dynamics of a rotating m = 2, n = 1, resistive MHD tearing mode as observed on TEXT-U. A set of external saddle coils induces a magnetic field whose m = 2, n=1 component is either in phase or out of phase spatially with the intrinsic m =2, n=1 error field. This experimentally applied field, combined with the pre-existing error field, decelerates the plasma rotation by coupling to the tearing mode and induces a locked mode. The time evolution of the average rotation frequency to the tearing mode amplitudes of a Mirnov signal observing the tearing mode are predicted analytically.