Studies of challenge in lower hybrid current drive capability at high density regime in experimental advanced superconducting tokamak

Abstract

Aiming at a fusion reactor, two issues must be solved for the lower hybrid current drive (LHCD), namely good lower hybrid wave (LHW)-plasma coupling and effective current drive at high density. For this goal, efforts have been made to improve LHW-plasma coupling and current drive capability at high density in experimental advanced superconducting tokamak (EAST). LHW-plasma coupling is improved by means of local gas puffing and gas puffing from the electron side is taken as a routine way for EAST to operate with LHCD. Studies of high density experiments suggest that low recycling and high lower hybrid (LH) frequency are preferred for LHCD experiments at high density, consistent with previous results in other machines. With the combination of 2.45 GHz and 4.6 GHz LH waves, a repeatable high confinement mode plasma with maximum density up to 4.5 × 10 19 m −3 was obtained by LHCD in EAST. In addition, in the first stage of LHCD cyclic operation, an alternative candidate for more economical fusion reactors has been demonstrated in EAST and further work will be continued.

Predictive simulations of operation scenarios for EAST with METIS code

“…The existing LHCD system has already demonstrated its capabilities for long pulse operation. In particular, the high edge temperature and the high LH frequency (4.6 GHz) show an enhanced CD efficiency compared with the low edge temperature and LH frequency (2.45 GHz) due to the reduced PI effect, and it is of benefit to high-density SS H-mode operation (Ding et al 2017). Optimizing the use of the LHCD system in combination with ECCD, ICRF and NBI, the EAST will benefit the physics basis for SS H-mode operation of ITER.…”

Observations of xenon spectra on the EAST x-ray crystal spectrometer for high-temperature plasma diagnostics

“…The basic plasma parameters and the heating conditions of the representative high T e shot (SN 113 711) are shown in table 2 and figure 2. In this series of shots, higher electron cyclotron resonance heating (ECRH) injection powers [21], higher lower hybrid wave (LHW) injection powers [22], and lower electron densities compared to the normal shots are applied. The neutral beam injection (NBI) beams are not active in these shots.…”