New plasma-surface interactions research facility: PISCES-B and first materials erosion experiments on boronized graphite.

摘要

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(sup (minus)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 (times) 10(sup (minus)11) to 3 (times) 10(sup (minus)13) cm(sup (minus)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 (times) 10(sup 17) to 8 (times) 10(sup 18) ions cm(sup (minus)2) s(sup (minus)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 (times) 10(sup -5) to 1 (times) 10(sup -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(degree)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(degree)C. No significant surface composition change is observed after hydrogen plasma bombardment to a fluence of the order of 10(sup 22) ions cm(sup (minus)2). 30 refs., 9 figs., 2 tabs.