脉冲离子束流聚焦装置的研制

Development of Focusing Device Used in Pulse Ion Beam

用小型化的质量分析系统进行脉冲离子束流实验研究时,从真空弧离子源中引出的束流脉冲幅度大、能量低,由于空间电荷效应使脉冲束流发散度很大,使得离子束流成分分析的不确定度增大。为克服在有限的空间范围内脉冲离子束流聚焦的困难,研制了一种新的双限束光阑三膜片透镜离子束流聚焦装置。双限束光阑着重减少束流发射度,三膜片透镜则适合小尺度空间的脉冲束流聚焦。计算机模拟的结果符合这种大脉冲离子束流聚焦的设计思想。磁质谱仪应用该聚焦装置后,发散到质量分析器分析盒上的脉冲离子束流幅值从未加聚焦前的115mA减少至0.06mA,脉冲离子束流质量分析的不确定度降低。

In the experiment research of the pulse ion beam using small mass analysis system, the pulse beam is extracted from vacuum arc ion source with high beam current pulse amplitude and low energy. The space charge effect can make beam diverge rapid- ly, and this will result in large uncertainty in the analysis of hydrogen ion beam compo- sition. In order to overcome the difficulty to focus pulse ion beam in narrow interspace range, a new ion beam focusing device with double limit beam diaphragm and three- flakelet electrostatic lens was developed. The double limit beam diaphragm is mainly used to reduce beam divergence. The three-flakelet electrostatic lens is very fit for pulse ion beam focusing in small size vessel. The computer procedure simulation was in accord with the design idea for focusing the high pulse ion beam. Using this focusing device in magnet mass spectrograph, ion beam current pulse amplitude to diverge into analysis box of the mass analyzer is reduced to 0.06 mA. The uncertainty of pulse ion beam mass analysis decreases.