Experimental results of plasma breakdown and flux optimization on HL-2A Tokamak☆

The plasma breakdown in HL-2A is found to match the Paschen law similar to the other tokamaks. It is also found on HL-2A that the breakdown time is about 10 ms, which is a little short for its high toroidal electric field (E ∼ 1.0–2.0 Vm⁻¹), and the breakdown happens when the criterion of E × L (connection length) is about 33 V relative to a theoretical prediction of 67 V. Flux consumption optimization is achieved by scanning the loop voltage with identical target plasma current and heating with LHCD in the ramp-up phase. Based on Ohmic Heating during ramp-up phase, the limiter configuration consumes more flux than the divertor configuration. Adding LHCD during ramp-up phase reduces overall flux consumption.