The Dynamics of Flux Amplification of Coaxial Helicity Injection on the HIT-II Spherical Torus

Internal magnetic probing results are combined with external magnetics, bolometry and injector circuit measurements to provide a detailed description of the dynamics of a Coaxial Helicity Injected (CHI) ST demonstrating poloidal flux amplification. The relaxation process is characterized by an initial, sub-\textit{ms} phase of rapid flux and plasma current buildup, a slower, \textit{ms} time scale phase of steady current buildup and a stagnation phase in which helicity drive is balanced by losses which is strongly associated with a large amplitude edge mode activity. Flux amplification behavior over an extensive parameter range is presented in juxtaposition to non-relaxation CHI discharges. Possible explanations for the observed relaxation and flux amplification will be discussed.