Hu Huaichuan

Recent Results of LHCD Experiments in EAST

Lower hybrid wave (LHW)-plasma coupling and lower hybrid current drive (LHCD) experiments in divertor, including single-null and double-null, and limiter configurations were conducted systematically in EAST. A maximum power for launched LHW is 1.4 MW and the plasma current with LHCD is about 1 MA. It is indicated that the coupling is best in limiter configuration, then in single-null one, while worst in double-null one. Study in current drive efficiency by a least squares fit shows that there is no obvious difference in drive efficiency between the double-null and the single-null cases, whereas the efficiency is a slightly lower in the limiter case. The effect of plasma density on the current drive efficiency is due to the influence of density on impurity concentration.

Study of Bridging of the Spectral Gap in the Lower Hybrid Wave Current Drive in the HT-7 Tokamak

An additional lower hybrid wave (LHW) with a higher refractive index (N//) was investigated in the HT-7 tokamak to bridge the spectral gap. It was found that the spectral gap between the wave and the electrons in the outer region was bridged by the additional wave with a higher N// spectrum. The results showed that the sawteeth oscillation was suppressed by launching the additional wave, and that the power deposition profile was moved outwards and the current profile was broadened due to the application of the additional wave. Our study indicates that the spectral gap may be bridged by an additional wave with a higher N// spectrum in the outer region.