Initial results from the scoop limiter experiment in PDX

A particle scoop limiter with a graphite face backed by a 50 liter volume for collecting particles was used in PDX. Experiments were performed to test its particle control and power handling capabilities with up to 5 MW of D0 power injected into D+ plasmas. Line average plasma densities up to 8 x 1013 cm-3 and currents up to 450 kA were obtained. Plasma densities in the scoop channels greater than 2 x 1013 cm-3 and neutral densities in the scoop volume greater than 5 x 1014 cm-3 were observed. There is evidence that recycling may have occurred in the scoop channels for several discharges with large line-averaged plasma density. At beam powers up to 2.5 MW, energy confinement times above 40 ms were deduced from magnetics measurements and from transport analysis. Pressures in the vacuum vessel were in the 10-5 Torr range, and recycling source neutral densities in the central plasma were low