HL-2A Experiments Scenarios for 2008


The total auxiliary heating designed power on HL-2A was up to 4.5 MWNBI/1.5MW, ECRH/2MW, and LHCD/1MW. The achieved ECRH and NBI power in the experimental campaign was over 1.6 MW and 1.0 MW respectively. In 2008, with the application of high power NBI, ECRH and effective SMBI technique, the synergetic heating systems NBIECRHLHCDwere used to fulfill the plasma heating and current drive. The physical task was focused on plasma confinement and transport, edge plasma and turbulence, energetic particle physics and impurity transport.

1In the HL-2A divertor discharges, by using high power ECRH and NBI heating, the supershot discharges were achieved, which were characterized by peak electron density profile. The corresponding plasma energy confinement time made a marked improvement.

2The low frequency zonal flowsZFin 05 kHz, the associated geodesic acoustic modeGAMoscillations in 10 kHz, with the toroidal mode number approaching zero, were observed in the float potential spectrum of Langmuir probe diagnostic system for the first time. Analysis showed both the ZF and the GAM existed in the edge region of HL-2A plasma. These results attracted worldwide attention. 

3A blob is a coherent structure extending in a fila- mentary way along a magnetic field line, characterized by a density much higher than the ambient density and leaving the plasma at a high radial velocity. By using a fast scanning pneumatic-driven Langmuir probe system, the blobs were observed. Some important parameters, such as its radial distribution of poloidal wave number, radial velocity and poloidal velocity were measured with half-overlapped time-window and two-point spectrum analysis techniques.  

    4SMBI fueling technique was improved in 2008. With microwave reflectormetry and hydrogen atom radiation diagnostic system, the injection penetration, particle deposition distribution and fueling efficiency were explored. It is prepared for the future pedestal fueling injection.    

5A neoclassical tearing mode with mode m/n2/1 was observed in the high power ECRH discharges in China for the first time. It degrades plasma confinement by decreasing plasma beta by about 18%. The analysis showed the non-linear growth evolution of magnetic island was in consistent with  the theoretical prediction. For the seed magnetic island, control with ECRH for destabilizing large sawtooth caused by neutral beam heating was achieved. It is one of the key issues of NTMs controlling in the world. 

6The fish-bone turbulence continued to be investigated during the ECRH and NBI discharges. By using a newly installed CdTe spectrometer diagnostic system, the relation between fish-bone turbulence and energetic electron spectrum was studied. The chirping behavior in fish-bone frequency and jumping of mode frequency were newly observed.

7The shear Alfven eigen mode, which was excited with sideband resonance by neutral beam injection caused energetic ions, was studied. Observed pitch-fork phenomena and BAE mode excited by large magnetic island coupling to GAM curvature provided the experimental base for the energetic ions dynamic research.