Experimental Study of Plasma Breakdown by Toroidally Injected Electron Cyclotron Waves in Heliotron J

Abstract

Plasma breakdown using electron cyclotron waves with toroidally inclined launch has been studied experimentally in the stellarator/heliotron device, Heliotron J. The experimental results show that the second harmonic X-mode breakdown has a weak dependence on the parallel refractive index, N_ll, for the small toroidal injection angle range. When the fundamental resonance exists inside the vacuum chamber, the breakdown occurs quickly, independent of the toroidal injection angle.