大功率负离子源铯注入对负离子产额影响的实验研究

Experimental study on the effect of cesium injection on negative ion yield of high power negative ion source

铯注入可显著降低射频负离子源等离子体电极(Plasma Grid,PG)金属表面逸出功,促进H−离子的表面产生,是提高射频负离子源H−离子产额的有效手段。依托强流射频负离子源综合测试平台,以H−离子表面产生机制、铯注入作用机制为理论基础,以H−离子引出电流、电子引出电流及铯852 nm特征谱线相对强度等数据为依据;通过控制PG板温度和铯注入速率,本实验探究在铯注入条件下,PG板温度和铯注入速率对射频负离子源H−离子产额的影响作用。实验结果表明:铯注入可有效提高H−离子产额,且在当前实验条件下,PG温度在180~200℃范围时,H−离子转换速率最大;在铯注入温度为250℃/270℃时,约162 min后,H−离子转换速率达到动态平衡。

[Background]Cesium injection can significantly reduce the work function of plasma grid surface of the radio frequency(RF)negative ion source,which is an effective way to promote the surface generation and improve the yield of H−ions.[Purpose]This study aims to find the impact of the temperature of plasma grid(PG)and the cesium injection velocity on the yield of H−ions under the condition of cesium injection.[Methods]Based on the experimental platform of high power radio frequency negative ion source,the mechanism of H−ions surface generation and cesium injection were the theoretical basis,the current of H−ions,electron current and the relative strength of cesium characteristic spectral line were taken as numerical benchmarks.The effects of PG plate temperature and cesium injection rate on the yield of RF negative H−ion source were investigated by emperiments.[Results&Conclusions]Under current experimental conditions,cesium injection has the best effect when the PG temperature is in the range of 180~200℃.The H−ions conversion rate reaches dynamic equilibrium after about 162 min when the temperature of cesium injection is 250℃/270℃.