Mechanical divertor experiments in Macrotor

The feasibility of pumped limiters has been demonstrated on the Macrotor tokamak using both small neutral collection probes (2.5 cm diameter) and a large-area limiter (20 cm × 60 cm). Neutral pressures due to particle accumulation have reached as high as 8 microns. The particle removal efficiency of the neutral collection probes was measured to be 17% and estimated to be greater than 50% in the large-area limiter case. A quadratic dependence of the pressure on plasma density is observed.