利用时间分辨Ar的K壳层发射光谱诊断内爆靶丸芯区电子温度的时间演化过程

Evolution of indirect-drive-implosion core electron temperature determined by time-resolved X-ray Ar K-shell spectroscopy

在神光Ⅱ装置上的内爆实验中,通过在充氘气(D2)的靶丸中掺入氩(Ar)元素,利用晶体谱仪配条纹相机测量得到了内爆停滞阶段Ar的K壳层发射光谱随时间的变化。在实验中,观测到Ar的Heα,Heβ以及Lyα线发射,持续时间大约200ps。用Heα线与Lyα线强度比值来推断靶丸芯区电子温度。利用碰撞辐射模型,从理论上计算出Heα线与Lyα线强度比值随电子温度、数密度的变化。通过将实验上观测到的Heα线与Lyα线强度比与理论计算值相比较,获得了芯区电子温度随时间的演化。并计算比较了不同电子密度条件下推断出来的电子温度的差异,证明诊断电子温度的方法对电子数密度的变化不敏感。利用逃逸因子修正了自吸收效应,从计算的结果可以看出在目前的实验中Heα线和Lyα线是光学薄的。

Time-resolved X-ray spectroscopy has been used to study the implosion physics of indirectly driven inertial confinement fusion experiments on the SG Ⅱ laser facility. Through the use of high-Z dopants （Ar） in D2 gas,K-shell emissions,which provide information on core conditions,were recorded by streaked X-ray crystal spectrometer. Evolution of core electron temperatures was then deduced by comparing the line intensity ratio of the Heα to Lyα resonance lines inferred from experiments with that obtained by theoretical calculations,and self-absorption effects are corrected by the escape factor. The results show that this method for electron temperature diagnosis is not sensitive to the variation of electron density,and the Heα and Lyα lines are optically thin in current experiments.