强激光与固体靶相互作用所致硬X射线剂量和能谱的实验测量

摘要

为了研究强激光与固体靶相互作用产生的电离辐射危害,本文在星光Ⅲ 300 TW强激光装置上开展了一系列激光打靶实验.实验使用的激光功率密度为5×1018～4×1019 W/cm2,激光脉冲能量为60～153 J,靶为直径1 mm、厚度1 mm的Ta圆柱,本文分别对X射线剂量、X射线能谱和超热电子能谱进行了测量.实验结果表明,测量到的单发最大X射线剂量约为16.8 mSv,靠近激光传播方向(0°),距靶50 cm处;激光0°方向的X射线剂量随激光功率密度的增加而显著增加,激光90°方向的X射线剂量随激光功率密度的变化相对较小;测量到的X射线能谱可大致用含有两个X射线温度的指数分布函数描述,其中0°方向测量到的X射线温度为0.4～1.15 MeV,90°方向测量到的X射线温度为0.25～0.54 MeV;实测超热电子温度与Wilks定标率符合较好.%To study the radiological hazards from intense laser-solid target interactions,a series of laser-target experiments were carried out on the XG Ⅲ 300 TW laser systems.The laser intensity is 5×1018-4×1019 W/cm2 and the laser energy is 60-153 J.The target is Ta cylinder with thickness of 1 mm and diameter of 1 mm.The X-ray dose,X-ray spectrum,and hot electron spectrum were measured respectively.The results show that the X-ray dose up to 16.8 mSv is measured at 50 cm close to the laser propagation direction (0°).The X-ray dose at 0° increases significantly with the laser intensity,while the X-ray dose at 90° is less correlated to the laser intensity.The measured X-ray spectrum can be approximately described as an exponential distribution with two X-ray temperatures ranged from 0.4 to 1.15 MeV at 0° and from 0.25 to 0.54 MeV at 90°.The measured hot electron temperature is consistent with the predicted electron temperature by Wilks law.