Enhancement of runaway production in lower hybrid current driven plasma with IBW heating in the HT-7 tokamak

Abstract

Runaway production is observed to be enhanced in lower hybrid current driven (LHCD) plasmas during ion Bernstein wave (IBW) heating as compared with the LHCD only plasma in the HT-7 tokamak. The distortion of the electron distribution function is the effect of the quasilinear diffusions of two types of waves. IBWs modified the distribution function of the electrons by helping to fill the so-called lower hybrid wave (LHW) spectral gap for low parallel velocity. Thus the LHW was significantly coupled to the fast electrons produced by the IBW, and partial LHW power was absorbed on the first pass without significant n -upshift. The synergy interaction of two types of waves results in high electron parallel energy and enhanced quasilinear diffusion, which is favorable for the production of runaway electrons. This is directly related to the improvement of plasma performance in the operation mode of simultaneous injection of LHW and IBW power.

Development of hard X-ray spectrometer with full digital data acquisition for runaway electron studies at HL-2M

“…During the simultaneous application of Lower Hybrid Wave (LHW) and ECW, REs cannot be created when LH power is switched off, but it's observed to be enhanced when EC power is switched off [15]. Similar results are obtained in Hefei Torus 7 (HT-7) tokamak, where the control of RE production is realized by the combination of ion Bernstein wave and LHW [16,17].…”

Soft landing of runaway currents by ohmic field in J-TEXT tokamak

“…The spectrometer system contains several NaI scintillator detectors and a multichannel analyzer (MCA) with 0.5 ms time resolution and 512 channels energy resolution [34]. These scintillator detectors are used to measure the HXR emissions in the energy range of 0.4-10 MeV resulting from the thick target bremsstrahlung when REs are lost from the plasma and impact on the vessel walls [35][36][37]. However, the measurements of the HXR emissions during the RE plateau regime are much more challenging because HXR emissions could reach the rates of -10 10 5 6 countss 1 and higher.…”

Hot spot generated by non-thermal electrons just before disruption in HT-7 tokamak

“…The measurement of non-thermal electrons is performed mainly by hard X-ray radiation (HXR) which monitors the non-thermal electrons in the energy range of 30-300 keV [14] and by ECE which is used to investigate the non-thermal electrons confined in plasma [15]. SXR as an assistant tool is used to clarify the radiation spikes during energy quench and also to reconstruct the magnetic flux surface just before disruption.…”