基于粒子云网格计算方法, 对质子束轰击靶面产生二次电子的效应进行了模拟研究, 得到了不同电场强度对质子束的品质以及其产生的二次电子的数量的影响。研究表明, 50 kV电压下, 质子束束腰宽度1.8 mm, 并有近10%的质子束打在阴极侧壁上; 150 kV电压下, 质子束束腰宽度1.2 mm。这说明, 抽取电场强度小时质子束分散, 其束流品质下降; 抽取电场强度大时质子束紧凑。通过调控抽取、加速电压, 可以有效地控制到靶质子流的聚散状况, 以及由此产生的二次电子的强度及分布。

Using the technique of Particle-In-Cell to simulate the secondary electron effect of proton beams bombarding the target surface, we obtained the results of the quality of proton beams and the quantity of secondary electrons affected by the extracted voltage. From which, we find that the width of proton beams’ waist is 1.8 mm at 50 kV and 1.2 mm at 150 kV. Therefore, the proton beams become dispersed at lower voltages and compact at higher voltages. Adjusting the extracted voltage between acceleration areas, we can control the quality of proton beams.