The features of the electron heat transport during high power ECRH & SMBI on HL-2A

Abstract

With high power ECRH and supersonic molecular beam injection (SMBI), the electron heat transport has been investigated on HL-2A. This paper will show features of the electron transport during ECRH, especially new non-local phenomena triggered by SMBI, in which an electron transport barrier is formed and the confinement is improved. The diffusion coefficient both from steady-state analysis (χhp) and the heat pulse propagation (χpb) increase with the ECRH power and decrease with the electron density, which is in agreement with the L-mode scaling. The ratio χhp/χpb is about 2.8 in Ohmic discharges; it increases to 3.3 with low power ECRH and decreases to 1.7 with the high power ECRH. The non-local transport phenomena induced by SMBI have been observed firstly on HL-2A. The density limit beyond which the phenomena disappear is apparently higher in the ECRH regime than in the Ohmic regime. Both the bolometer radiation and the Haemission decrease when the non-local effect appears. After the appearance of the non-local effect, it can be found that the region outside r/a ∼ 0.5, just like usual result, is cooled by SMBI, while the core Te increasing gives a surprise. The core Te is increased by about 18 %. This suggests that the injection of SMBI triggers the internal transport barriers.