New Development of Cesium-Free Negative Ion Sources Based on Plasma-Assisted Catalytic Ionization Method

结合中性粒子束注入加热用无铯负离子源的研发，研究了等离子体辅助催化电离法负氢离子的产生机理。当放电产生的正离子照射到金属表面并且其中一些穿过金属孔时，从照射平面的背面产生负离子。被照射的金属采用多孔镍、某些元素制成的金属栅格、或单孔铝制成的等离子栅格。发现负离子产生的主要过程不是由于快速正离子与吸附的氢原子碰撞而产生的解吸电离，而是慢速正离子在金属表面的中和和负电离。

Production mechanism of negative hydrogen ions in a plasma-assisted catalytic ionization method is investigated in connection with research and development of cesium-free negative ion source for neutral particle beam injection heating. When positive ions produced by discharge are irradiated onto a metal surface and some of them pass through the metal aperture, negative ions are produced from the back of the irradiation plane. The irradiated metal is used a porous nickel, metal grids made of some elements, or a plasma grid made of aluminum with single aperture. The dominant process of negative-ion production is found not to be desorption ionization owing to collision of fast positive ions with adsorbed hydrogen atoms but neutralization and negative ionization of slow positive ions on the metal surface.