Recent LHCD experiments on HL-2A and LHCD system development on HL-2M

Abstract

This paper presents recent Lower Hybrid Current Drive (LHCD) progress in SWIP, including the experiments on HL-2A and system development on HL-2M. The 3.7GHz LHCD system was built on HL-2A, where the first Lower Hybrid Wave (LHW) coupling to H-mode plasma experiment via Passive-Active Multijunction (PAM) launcher was carried out. The coupled power has been increased much from 470kW to 1400kW since 2014. The LHW power became more and more important in the H-mode discharges on HL-2A in the past 4 years. In 2018, 1.1s ELMy H-mode was achieved with the help of Neutral Beam Injection (NBI) and LHW injection. However, The LHCD experiments showed distinct characteristic on HL-2A, i.e. no full non-inductive current drive (loop voltage never dropped below 0.3V) and counter-current drive effect found in the situation of co-current drive spectrum. Full non-inductive current drive was finally obtained after the spectrum turned opposite. Besides those achievements, the abnormal LHCD phenomenon discussion, full non-inductive current drive experiments, co-current and counter-current comparison, LHW deposition and mechanism of LHCD ELM mitigation are described. At the same time, a 4MW LHCD system is planned to be constructed on HL-2M. A 2MW LHCD system has been developed for HL-2M tokamak until now. Four TH2103C1 klystrons, transmission lines and a 4MW FAM antenna are included in this system. The other part will be built soon.