First Plasma Experiment of Electron Cyclotron Resonance Heating by Optical Vortex Beam in Heliotron J

Abstract

Plasma experiments on electron cyclotron resonance heating (ECRH) using a high-power optical vortex beam (OVB) have been demonstrated for the first time in the Heliotron J stellarator/heliotron device. The OVB is generated by a spiral phase plate in a 70 GHz ECRH system. Plasmas are successfully sustained up to the second harmonic extraordinary (X) mode cut-off density. Virtually identical performance in terms of stored energy and density limits confirms the injection of the OVB as a heating tool comparable to Gaussian beams. These first results showed that the OVB is a possible method for the research on wave and plasma physics in magnetically confined fusion systems.