Improved beta (local beta >1) and density in electron cyclotron resonance heating on the RT-1 magnetosphere plasma

Abstract

This study reports the recent progress in improved plasma parameters of the RT-1 device.Increased input power and the optimized polarization of electron cyclotron resonance heating (ECRH) with an 8.2 GHz klystron produced a significant increase in electron beta, which is evaluated by an equilibrium analysis of Grad-Shafranov equation.The peak value of the local electron beta e was found to exceed 1.In the high beta and high-density regime, the density limit was observed for H, D, and He plasmas.The line average density was close to the cutoff density for 8.2 GHz ECRH.When the filling gas pressure is increased, the density limit still exists even at the low beta region.This result indicates the density limit is caused by the cutoff density rather than the beta limit.From the analysis of interferometer data, we found that inward diffusion causes a peaked density profile beyond the cutoff density.