PROPERTIES OF THIN BORON COATINGS FORMED DURING DEUTERATED-BORONIZATION IN JT-60

Since 1992, the boronization using B10H14 (decaborane-based boronizati on) has been utilized in JT-60 once or twice a year. It is very effect ive in reducing both the impurities, like oxygen and carbon, in the pl asma and in recycling fuel particles. However, we needed similar to 50 0 discharges to exchange hydrogen in the boron film for deuterium, aft er the boronization using only He for a dilution gas. Using a mixed-di lution gas of He and deuterium, we made the boronized film on JT-60 fi rst wall (deuterated-boronization). A typical composition of working g as was 2% B10H14, 38% D-2 and 60% He, which was used in a flow through situation. The amounts of hydrogen and deuterium in the boronized fil m were evaluated to be similar to 5 and similar to 30 at%, respectivel y. In addition, the deuteration factor of D/(H + D) in the first plasm a after the boronization increased from less than 0.2 to 0.8. Thus, we can drastically reduce the number of the conditioning discharges from similar to 500 to similar to 50 for the isotope-exchange before D pla sma experiments.