重离子激发解吸测试装置设计与调试

束流与真空管壁碰撞后从腔体表面解吸出一定数量的分子和离子, 解吸出的粒子使加速器系统的真空度下降, 进而会影响束流的寿命。在重离子加速器中, 为了降低动态真空对束流的影响, 需找出一种低解吸率材料作为准直器镀膜材料。因此, 不同材料的解吸率测量已成为重离子加速器真空系统设计的关键所在。本文首先介绍了基于中科院近代物理研究所320 k V高电荷态离子综合研究实验平台设计的解吸率测量装置, 并利用Molflow+真空分析软件计算了该测试装置的静态真空分布。其次以无氧铜为测试靶材进行了解吸率实验研究, 得出了束流轰击靶材时动态真空变化的趋势, 同时计算了无氧铜在不同能量和不同流强Xe¹⁰⁺和O⁺束流作用下的解吸率和相对应的电子能损。结果表明粒子解吸引起的动态真空变化较明显, 无氧铜解吸率随着入射束流能量的增加而增加, 而且在长时间束流作用时会出现束流清洗效应, 即解吸出的粒子在束流长时间轰击下逐渐减少。电子能损的平方和解吸率成正比例关系, 与相关文献的结论一致, 说明实验装置运行稳定, 获得的数据具有一定的参考意义。

Surface Desorption Induced by Heavy Ion Bombardment:A Simulation and Experimental Study

Herein, we addressed theproblem ofpressure build-up inheavy ion accelerator, originated from bombardment of heavy ion beamon vacuum chamber walls. Desorption of the adsorbed molecules/ions on oxygen-free Cu-surfaces was theoretically analyzed, numerically simulated with software Molflow + and experimentally investigated with the lab-built test platform. The impact of the properties of Xe¹⁰⁺ and O⁺ beams on the electronic energy loss, desorption yields and dynamic changes in pressure was investigated. The results show that the energy and intensity of the ion beams significantly affected the dynamic changes in pressure. For example, as the energy increased, the desorption yields increased; bombardment for a long time resulted in beam scrubbing effect, i. e. a decrease of the gases desorption yield. Moreover, the square of electronic energy loss was proportional to the desorption yields. The measured results were in good agreement with those reported in literature.