Seeding cesium is an important means to increase beam current for a negative ion source on neutral beam systems. In order to investigate deposition distribution of cesium in an RF-driven negative ion source, experiments applied quartz crystal microbalances as sensors have been conducted. The experiments had four phases: (1) cleaning of impurities; (2) static cesium seeding; (3) cesium seeding with heating of the negative ion source; (4) cesium seeding with plasma and heating of the negative ion source. The experimental results indicate that the deposition of impurities keeps stable after long-term cleaning by plasma and has no influence on the cesium seeding experiment. Amount of cesium deposits into the gap between the flange of the diffusion chamber and that of the extraction system. Seeding cesium with plasma and heating of the diffusion chamber can increase cesium deposition to the plasma grid significantly. For long-pulse operation of an RF-driven negative ion source, heating of the flange of the diffusion chamber is also necessary.

Radio frequency negative ion source, Cesium deposition, Temperature control, Cesium injection

在负离子源中馈铯是提升应用于中性束系统的负离子源的输出束流的一个重要手段，为了分析射频驱动负离子源中铯沉积的空间分布和时间演化，使用了石英晶体微天平作为传感器开展了初步实验。实验分为 4 个阶段开展：(1) 杂质清洗；(2) 静态馈铯；(3) 负离子源加热条件下的馈铯；(4) 在等离子体放电和负离子源加热条件下的馈铯。实验结果说明，经历长时间的放电清洗之后，传感器上的杂质沉积保持稳定，对馈铯实验不产生影响。馈铯过程中铯容易淤积在扩展腔法兰和加速系统法兰之间的空腔中。在等离子体和负离子源加热的共同作用条件下，铯在等离子体电极表面的沉积会得到大幅度的提升。对于负离子源的长脉冲运行来讲，不仅需要对负离子源的腔壁进行加热，对于法兰的加热也是必要的。

射频负离子源, 铯沉积, 温度控制, 铯注入