毛细管快放电中的管壁烧蚀

Experimental Investigation on Ablation Character of Capillary Discharge

介绍了一台毛细管快放电软X射线激光实验装置 ,包括Marx发生器 ,Blumlein传输线和毛细管放电室等。在充入相同气压的气体 ( 70～ 90Pa)和相同主脉冲 (电流峰值 30kA ,上升沿 30ns)放电条件下 ,通过观测其放电后的真空紫外波段辐射 ,对分别采用该装置固有的幅值为 7kA和外加的幅值为 30A的两种预脉冲时 ,聚乙烯毛细管和陶瓷毛细管的管壁烧蚀情况进行了研究。实验结果表明 ,采用 7kA预脉冲和聚乙烯毛细管时 ,管壁烧蚀量大 ,导致真空紫外波段的积分谱呈连续状 ;而采用 10～ 30A的预脉冲和高纯度陶瓷毛细管时 ,则有效地减少了管壁烧蚀量 ,谱线分辨性好。为进一步提高X射线激光能量转换效率、获得均匀等离子体柱、进而获得激光放大提供了依据。

A capillary discharge setup, consisting of a Marx generator system, main switch, Blumlein transmission line and pre-pulse circuit, has been developed . This device is designed to excite electron collision pumping scheme XUV laser in Ne like Ar at 46.9 nm. The ablation characteristics of the discharged capillary are experimentally investigated by measuring VUV emission from the capillary discharged. The ablation of capillary wall for polythene and alumina material is studied at inherent pre pulse (7 kA) of the Blumlein transition line (BIL) and at pre pulse of 20～30 A respectively under the same main current of 30 kA having a rising time of 30 ns. The reason of the plentiful ablation is that there exist high electric fields for inherent pre pulse, which cause an inhomogenous channel spark near the wall. The experiment results indicate that the inherent pre pulse of BTL on grounding inductance is too large to create uniform plasma columns. In the case of 20 A pre pulse the background emission decreased remarkably and the radiations is discriminable. In the experiments, only when the pre pulse is less than 100 A, for alumina capillary, can the ablation be greatly reduced.