Ueno A, Oguri H, Ikegami K, Namekawa Y, Ohkoshi K
J-PARC Center, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195, Japan.
Rev Sci Instrum. 2010 Feb;81(2):02A720. doi: 10.1063/1.3271243.
The following interesting experimental results observed in Japan Proton Accelerator Research Complex (J-PARC) H(-) ion-source developments are reviewed. It was proven that almost all of H(-) ions were produced with surface reactions in cesium (Cs)-free J-PARC H(-) ion-sources. The world's most intense class H(-) ion current of 38 mA in Cs-free ion sources for a high-energy linac was attained by an optimal shape and high temperature of the plasma electrode (PE), usage of a lanthanum hexaboride (LaB(6)) filament, and a newly devised high-power constant-current pulsed-arc power supply indispensable for it. It was also proven that the H(-) ion current could be increased to more than 40 mA by optimizing LaB(6)-filament shape. The surface elemental analysis of the PE after operation with a LaB(6)-filament showed that it was coated by boron (B) 95.5%, lanthanum (La) 2.5%, and oxygen (O) 1.9%. The H(-) ion current decreased by about 20% when a tungsten (W) filament was used instead of a LaB(6)-filament. The H(-) ion current could not be increased by seeding cesium (Cs) if the LaB(6)-filament was used. On the other hand, it was increased to more than 70 mA with much lower arc current of 150 A if Cs was seeded when a W-filament was used.
本文回顾了在日本质子加速器研究中心（J-PARC）H⁻离子源开发过程中观察到的以下有趣实验结果。事实证明，在无铯的J-PARC H⁻离子源中，几乎所有的H⁻离子都是通过表面反应产生的。通过优化等离子体电极（PE）的形状和提高其温度、使用六硼化镧（LaB₆）灯丝以及为此专门设计的高功率恒流脉冲电弧电源，在用于高能直线加速器的无铯离子源中实现了世界上最强的38 mA H⁻离子流。还证明了通过优化LaB₆灯丝形状，H⁻离子流可以增加到40 mA以上。使用LaB₆灯丝运行后对PE进行的表面元素分析表明，其表面涂层成分为硼（B）95.5%、镧（La）2.5%和氧（O）1.9%。当使用钨（W）灯丝代替LaB₆灯丝时，H⁻离子流下降了约20%。如果使用LaB₆灯丝，注入铯（Cs）并不能增加H⁻离子流。另一方面，当使用W灯丝并注入Cs时，在低得多的150 A电弧电流下，H⁻离子流增加到了70 mA以上。
