Preliminary results of ELMy H-mode experiments on the HL-2A tokamak

Abstract

Typical ELMy H-mode discharges have been achieved on the HL-2A tokamak with combined auxiliary heating of NBI and ECRH. The minimum power required is about 1.1 MW at a density of 1.6 × 10 19 m −3 and increases with a decrease in density, almost independent of the launching order of the ECRH and NBI heating. The energy loss by each edge localized mode (ELM) burst is estimated to be lower than 3% of the total stored energy. At a frequency of typically 400 Hz, the energy confinement time is only marginally reduced by the ELMs. The supersonic molecular beam injection fuelling is found to be beneficial for triggering an L-H transition due to less induced recycling and higher fuelling efficiency. The dwell time of the L-H transition is 20-200 ms, and tends to decrease as the power increases. The delay time of the H-L transition is 10-30 ms for most discharges and is comparable to the energy confinement time. The ELMs with a period of 1-3 ms are sustained for more than ten times the energy confinement time with enhanced confinement factor H 89 > 1.5, which tends to decrease with the total heating power. The confinement time in the H-mode discharges increases with plasma current approximately linearly.

Investigation of statistical characterization of radial turbulence in the edge of HuanLiuqi-2A plasma with visible spectroscopy diagnostic

“…Its major and minor radius are R = 1.65 m and a = 0.4 m, respectively, toroidal magnetic field B t = 2.8 T, plasma current I p = 480 kA, line averaged electron density ͑1-8͒ ϫ 10 19 m −3 , edge safety factor q a =3-5, and a discharge duration of ϳ3.0 s. 11 The visible optical diagnostic system for edge turbulence measurement mainly consists of three lenses which are designed to reduce spherical aberration and coma, an interference filter for D ␣ line emission, and a photodiodes detector array which has 46 available channels. The distance between the detectors and the object plane is 110 cm.…”

Energy deposition onto HL-2A divertor plates in ELMy H-mode discharges using infrared thermography

“…The HL-2A tokamak (with major radius R = 1.65 m and minor radius a = 0.4 m) has two rather closed divertor chambers [6,7], however the lower single null (LSN) divertor configuration is used in this experiment. An IR camera which is sensitive to radiation wavelengths between 8 lm and 9 lm, has been developed to measure the evolution of the surface temperature on the outer divertor plates on HL-2A [8,9].…”

Internal transport barrier triggered by non-linear lower hybrid wave deposition under condition of beam-driven toroidal rotation

“…Routine stable H-mode discharge has been realized since 2009. 12 Here, we model the HL-2A discharge to explore the dynamics of ITB development.…”