The investigation programme of plasma discharge on HL-2A Tokamak

The area of plasma breakdown on HL-2A with pure Ohmic discharge is on the low field side(LFS) where the field null configuration is located, and the emission of Dα which was measured by CCD camera confirms the plasma formation area, the current of Vertical Field(VF) is an important factor to facilitate plasma breakdown. The effect of the prefill pressure on plasma breakdown is studied carefully by scan the prefill pressure, high and low prefill pressure will make the discharge failure, only in a appropriate range of the pressure can have reproducible prompt discharge. A new plasma start-up scenario has been introduced for bad wall condition, the result demonstrates that it can be successful for plasma breakdown even if the vaccum vessel asorbed a lot of impurties.