An overview of recent HL-2A experiments

Abstract

For the firsttime supersonic molecular beam injection (SMBI) and cluster jet injection (CJI) were applied to mitigate edge-localized modes (ELMs) in HL-2A successfully. The ELM frequency increased by a factor of 2-3 and the heat flux on the divertor target plates decreased by 50% on average after SMBI or CJI. Energetic particle induced modes were observed in different frequency ranges with high-power electron cyclotron resonance heating (ECRH). The high frequency (200-350kHz) of the modes with a relatively small amplitude was close to the gap frequency of the toroidicity-induced Alfven eigenmode. The coexistent multi-mode magnetic structures in the high temperature and low-collision plasma could affect the plasma transport dramatically. Long-lived saturated ideal magnetohydrodynamic instabilities during strong neutral beam injection heating could be suppressed by high-power ECRH. The absolute rate of nonlinear energy transfer between turbulence and zonal flows was measured and the secondary mode competition between low-frequency (LF) zonal flows (ZFs) and geodesic acoustic modes (GAMs) was identified, which demonstrated that ZFs played an important role in the L-H transition. The spontaneously generated E × Bshear flow was identified to be responsible for the generation of a large-scale coherent structure (LSCS), which provided unambiguous experimental evidence for the LSCS generation mechanism. New meso-scale electric potential fluctuations (MSEFs) at frequency f ∼ 10.5 kHz with two components of n = 0 and m/n = 6/2were also identified in the edge plasmas for the first time. The MSEFs coexisted and interacted with magnetic islandsof m/n = 6/2, turbulence and LF ZFs.

Three dimensional measurements of Geodesic Acoustic Mode with correlation Doppler reflectometers

“…Recently, the microwave reflectometers, especially the Doppler reflectometers have been developed in the HL-2A Tokamak [12], whose major and minor radius are R = 1.65 m and a = 0.4 m [13] multi-channel systems are dedicated to routinely measure the turbulence with high spatiotemporal resolution not only in the edge but also in the core of plasma. Figure 1 shows the characteristic frequencies on the equatorial plane for a HL-2A plasmas.…”

Design and construction of high-frequency magnetic probe system on the HL-2A tokamak

“…7 HL-2A (R = 1.65m, a = 0.4m) is a middle tokamak with auxiliary heating of 3MW neutral beam injection (NBI), 5MW electron cyclotron resonance heating/current drive (ECRH/CD) and 2MW lower hybrid current drive (LHCD). 8 Toroidal Alfvén eigenmodes (TAEs) and other high frequency MHD instabilities have been observed in the experiments. 9 The frequency of those modes is higher than 200 kHz, which exceeds the resonant peak of the standard probes (130 kHz) on HL-2A.…”

Study of energetic particle physics with advanced ECEI system on the HL-2A tokamak

“…The HL-2A device is a medium-sized circular tokamak with a major radius Rax = 165 cm, minor radius a = 40 cm and a closed diverteor, which can be operated in either a limiter configuration or a single null (SN) divertor configuration [16]. The achieved operation parameters are plasma current of Ip = 450 kA, toroidal magnetic field of Bt = 2.7 Tesla, electron and ion temperature of 5 keV and 2.8 keV, respectively, and a line averaged plasma density of ~ 8 × 10…”