神龙一号直线感应加速器(LIA)产生的强流高功率的脉冲电子束与 X光转换靶作用后可以产生高剂量的X光,同时由于转换靶的被烧蚀破坏在靶面产生回流离子,该回流离子的存在影响到电子束的聚焦。设计了4套法拉第筒及其对应的偏压电路,法拉第筒被放置在神龙一号X光转换靶上游不同位置,分布在电子束轴线两侧,电路设计最高偏压为1 kV;对神龙一号LIA 的X光转换靶面产生的回流离子进行了实验测量,分别得到回流正离子密度约在1021/m3,离子运动速度可达2～3 mm/s。计算比较表明,该离子流强度与神龙一号靶前电子束流相差很大,只有电子束流强的0.27%,对神龙一号电子束聚焦不会造成影响。

The Dragon-Ilinear induction accelerator(LIA) uses mm level diameter pulsed electron beam to strike the bremsstrahlung converter target to generate X-ray,which generates the backstreaming ions as well. Four Faraday cups are combined to collect backstreaming ions produced at the bremsstrahlung converter target of the Dragon-ILIA. Experiment and calculation results show that the backstreaming positive ions density and velocity are about 1021/m3 and 2～3 km/s,respectively.The calculated results show that the intensity of the backstreaming positive ion beam is only 0.27% of that of the targeting electron beam,thus the backstreaming ions would not affect the focus of the electron beam.