Preliminary particle scoop limiter measurements in PDX

Abstract

A plasma edge particle scoop limiter has been installed on the equator of the Princeton Divertor Experiment (PDX), a large tokamak. The scoop limiter is unique in that it is designed such that the plasma plugs the entrance throat, thereby impeding the return flow of neutralized gas to the discharge. Neutral-gas pressures of the order of 50 μm were measured inside the scoop. The pressure dependence on electron density in the scrape-off plasma at the throat entrance was stronger than linear.