Confinement Studies during LHCD and LHW Ion Heating on HL-1M

Confinement Studies during LHCD and LHW Ion Heating on HL-1M LHCD experiments were conducted on HL-1M in the past years. The LHW system is composed of a 2×12 multijunction launcher and two klystrons of 500kW. The confinement improvement by LHCD was confirmed on HL-1M. The investigations on the relationship between the confinement and the edge plasma phenomena were carried out. The confinement improvement seems to be related with the production of radial electron field during LHCD. Recently several distinctive phenomena related with plasma confinement were observed during LHCD. These phenomena include an ELM-like perturbation in boundary plasma and a sudden collapse of soft-X ray radiation from central plasma. Usually ELM mode was obtained in divertor configuratin, while on HL-1M the ELM mode was trigged by LHCD in limiter configuration. Moreover, at high density, distinct ion heating by LHW was observed. Analyses shows that the parameter decay instability seems to play a role in the mechanism of the ion heating. 1. Introduction HL-1M is a circular cross-section tokamak with R=102cm, a=26cm. Up to now, ECRH, LHCD, NBI, ICRH and pellet injection experiments have been conducted on HL-1M. Advanced wall condition techniques such as boronization, siliconization and lithium coating have been used. Among them the siliconization is the most successful and most frequent-used wall condition technique on HL- 1M. The wall conditioning enhanced plasma merits greatly. In this paper we only concentrate on the confinement improvement by LHCD and ion heating by LHW. LHCD was investigated extensively in many fusion devices not only as a promising method of non- inductive current drive but also as a effective way to control plasma profile and to improve the confinement of plasma. LHCD experiments were conducted on HL-1M in past a few years with a LHW system, composed of a 2×12 multijunction launcher and two klystrons of 500kW. Recently for LHCD experiments on HL-1M, more attentions were paid to the confinement improvements by LHCD and the its mechanism. We carried out investigation on the relationship between the confinement and the edge plasma phenomena. Several distinctive phenomena related with plasma confinement were observed during LHCD. These phenomena include an ELM-like perturbation in boundary plasma and a sudden collapse of soft-X ray radiation from the central plasma. Moreover, at high density, distinct ion heating by LHW was observed.