Effect of lower hybrid current drive on pedestal instabilities in the HL-2A tokamak

Abstract

Edge localized mode (ELM) mitigation with lower hybrid current drive (LHCD) has been observed in the HL-2A tokamak. This mitigation effect is very sensitive to the parameters as the plasma density and the LHCD absorbed power, i.e., more easily to be observed for high density and large LHCD absorbed power. The divertor peak heat load released by ELM has been significantly reduced during the mitigation phase. The pedestal density gradient is slightly reduced during ELM mitigation, and the plasma rotation velocity and ion temperature are significantly reduced by LHCD. It has been found that the ELM mitigation is not synchronized with the LHCD, while it is synchronized with the increase of the pedestal turbulence, showing that the enhancement of the transport due to the pedestal turbulence can be the direct cause of the ELM mitigation.