Experiments with a biased pump limiter on the HL-1 tokamak

Experiments with a biased pump limiter of positive potential have been performed on the HL-1 tokamak. The line averaged density ¯n e increases by 50%. The D α (or H α ) light from the plasma edge decreases a little (10%). The particle flux signal taken at the plasma edge decreases by 50%. The OVI signal at the edge increases by 60% and the loop voltage increases by 20%. The particle flux signal in the throat decreases by 60%. The particle confinement time τ p * increases by 50–100%, the energy confinement time τ E increases by 20–40%. But the CIII, CrI lines near the neutralizer plate increase for both positive and negative biasing. Generally, effects with negative biasing are much less pronounced than with positive biasing. For example, the line averaged density n e increases by 25% only with a negative biasing of 200 V.