Transition of the radial electric field by electron cyclotron heating in the CHS heliotron/torsatron

Abstract

The transition of a radial electric field from a negative to a positive value is observed in the compact helical system when the electron loss is sufficiently enhanced by the superposition of the off-axis second harmonic electron cyclotron heating on the neutral beam heated plasmas. Existence of the threshold for the enhanced particle flux required to cause the transition is experimentally certified. The observed threshold is compared with a theoretical prediction.