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 he lium 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 t hat 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 observe d. A small H/B atomic ratio and low levels in the light impurity provi ded high ion temperature and low density plasmas by neutral beam injec tion heating.