Book Description

A new plasma-surface interactions research facility: PISCES-B has been designed and constructed at University of California, Los Angeles. The entire vacuum chamber is bakable and a base pressure of the order of 10−8 Torr is attainable using two turbo molecular pumps with a total pumping speed of 6000 l/s. The PISCES-B facility can generate continuous plasmas of argon, helium, hydrogen, deuterium and nitrogen. The density of these plasmas ranges from 1 x 10−11 to 3 x 10−13 cm−3 and the electron temperature ranges from 3 to 51 eV. The plasma bombardment flux to a target surface inserted in the plasma column can be varied from 1 x 1017 to 8 x 1018 ions cm−2 s−1. Due to the high pumping speed, the neutral pressure of the working gas during plasma generation is controllable in the wide range from 3 x 10−5 to 1 x 10−3 Torr. These conditions are similar to those seen at the limiter and divertor areas in toroidal fusion devices. Using the PISCES-B facility, first materials erosion experiments have been conducted on 3% boronized graphites and iso-graphites as the reference materials. The chemical sputtering yield due to hydrogen plasma bombardment at 300 eV for 3% boronized graphite has been found to be about 30% smaller than that for iso-graphites at temperatures from room temperature to 900°C. Also, radiation enhanced sublimation due to hydrogen plasma bombardment at 400 eV is found to be suppressed by 20-30% for 3% boronized graphite at temperatures up to 1300°C. No significant surface composition change is observed after hydrogen plasma bombardment to a fluence of the order of 1022 ions cm−2. 30 refs., 9 figs., 2 tabs.