IMPURITY BEHAVIOR IN BORONIZED HELIOTRON-E

Changes of impurity behavior and plasma performances by a boronization were investigated in Heliotron E. A 2.45 GHz ECH boronization with helium and decaborane at B = 0.046 T was developed. The concentration of H/B atomic ratio in the deposited boron layer was much smaller than that of conventional de glow discharges and the typical value was 0.1. The light impurity, oxygen and carbon, decreased drastically, but the reduction of the metallic impurity, iron and chromium, was not observed. A small H/B atomic ratio and low levels in the light impurity provided high ion temperature and low density plasmas by neutral beam injection heating.