RF离子源引出特性的研究

 为了使RF离子源具有良好的引出特性，测试了吸极几何参数、振荡器板压和引出电压对离子源聚焦度的影响，对实验结果进行了分析。在其它参数不变的情况下，吸极的外径D与内径d之比存在最佳值，增加D/d，有利于过聚焦的离子束恢复聚焦状态。吸极的长度为L，石英套管比吸极长l。当l/D增大时，聚焦度上升，引出束流下降。L/d之比减小时，聚焦度增大。当L/d小于4时，聚焦度增加趋势变缓。综合考虑聚焦度、引出束流和气压，D/d，l/D，L/d适宜的选择范围分别为1.6～2.1，0.7～1.1,4～7。增加振荡器功率会使离子束呈弱聚焦，而增加引出电压会使离子束呈过聚焦。振荡器功率和引出电压都存在最佳值。

Extraction property of RF ion source

Effects of the geometry parameters of drawing electrode,oscillator plate voltage and extraction voltage on the focusing degree of ion source are measured and the experimental results are analyzed to ensure the quality extraction of the RF ion source.On the condition that the other parameters keep unchanged,the ratio of the outer diameter D to its inner diameter d of the drawing electrode has an optimum value.The increase of D/d is beneficial to the re-focusing of over-focusing ion beam.The length of the drawing electrode is L and the quartz pipe is l longer than the drawing electrode.The increase of l/D leads to the increase of focusing degree and the decrease of extraction beam intensity.Focusing degree rises with the decrease of L/d and the rising tendency slows down when L/d is smaller than 4.The suitable ranges of D/d,l/D and L/d are respectively 1.6~2.1,0.7~1.1 and 4~7 on the comprehensive consideration about focusing degree,extraction beam intensity and pressure.Increasing oscillator power can make ion beam weakly focus and increasing extraction voltage can make ion beam over focus.