Operation of HL-2A tokamak

The operation conditions have been improved via developing new technologies and improving the hardware on HL-2A tokamak in recent years. The ECRH system has been upgraded to 3 MW/68 GHz, the supersonic molecular beam injection (SMBI) fuelling technique has been developed further, and clusters can be formed in the SMB by cooling the gas to around liquid nitrogen temperature, so that deeper penetration can be achieved. Besides, there are about 30 kinds of diagnostics developed on HL-2A to measure the plasma parameters. These diagnostic systems include magnetics, microwave reflectometry, CXRS, Thomson scattering, FIR interferometer etc. Some of them were specially designed for the physics experiments. For example, a novel design of Langmuir probes was developed to study the 3-D structure of zonal flows. With these hardware development and improvement, new experimental results have been achieved in the fields of turbulence, transport, MHD instabilities and energetic particle dynamics. In particular, the ELMy H-mode has been achieved by combining the auxiliary heating of NBI and ECRH, SMBI is beneficial for the L-H transition and the H-mode operation on HL-2A, and suitable for studying particle transport and controlling the ELMs during H-mode discharges due to its deep and local injection features and good controllability. Besides, the three dimensional spectral structures of the low frequency zonal flow and quasi-mode, which were predicted by theory and simulation, have been observed simultaneously. The beta-induced Alfvén eigenmodes (BAEs), excited by large magnetic islands (m-BAE) and by energetic electrons (e-BAE), are investigated, these phenomena are under further study.