New Results of Supersonic Molecular Beam Injection on HL-2A

Recently, a new gas supply system with pressure measurements was installed in the Supersonic Molecular Beam Injection (SMBI) system on the HL-2A tokamak. The quantity of injected particles varies with parameters of SMBI has been measured. Using plasma density profile measured by the multi-channel high power DCN laser interferometer, the mean particle increment in the plasma could be calculated after an SMBI pulse. Fuelling efficiency is estimated as the particle increment of the plasma divided by the quantity of injected particles. Fuelling efficiency depends on Injection depth which is not only a key issue for fuelling techniques but also an important physical significance. The study on the penetration depth of SMBI has been carried out on the HL-2A tokamak through tangential D arrays. The D signals show that the SMB consists of a fast component (FC) and a slow component (SC) after passing through a conic nozzle, which is installed on SMB valve to improve the beam performance. The FC can penetrate more deeply such as 8.5 cm inside the separatrix, while the SC is around 4 cm inside the separatrix. Some valuable phenomena with SMBI fuelling in H-mode discharges on HL-2A are also presented.