Dynamic behavior of plasma space potential in toroidal helical plasmas

A heavy ion-beam probe (HIBP) is a diagnostic device which can measure plasma space potential with high spatial and temporal resolution, and the radial electric field can, in turn, be deduced from the potential profile. The fast time response of a 200 keV-beam HIBP installed on a compact helical system allows the study of fast phenomena such as transition, collapse and fluctuations, and static space potential profiles. Experimental results from the CHS-HIBP are presented with emphasis on the dynamic behavior of the space potential associated with electric field bifurcation and on-potential oscillations during bursting magnetohydrodynamic instabilities.