Optimization of Particle Control by Boronization

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We proposed a new method of boronization using less hazardous solid decaborane and obtained the following results on the coating technique, evaluation of boron films and the boronization effects.1. Development of Coating Techniques : Instead of toxic explossive diborane, a new solid boride (decaborane) was used under of the sublimation in vacuum. In addition, we established a boronization technique based on thermal CVD without discharge decomposition. A comparison between plasma CVD and thermal CVD was made for decaborane and diborane.2. Control of Hydrogen Content of Boron Film : A hydrogen content to be a measure of recycling was evaluated by resonant nuclear reaction analysis. The H content drastically decreased with increasing a wall temperature and also as a result of ion bombardment. Deuterized boronization by isotope exchange from H to D was accomplished by the way where D_2 is admixed in boron hydride gas or the film surface is conditioned by a D_2 glow discharge.3. Boronization Effects : Basic experimetns were performed to test the hydrogen recycling and the oxygen gettering after boronization.Finally, the decaborane-based boronization we proposed have been used in JT-60U, Heliotron E, and so on.