双预脉冲和弯曲靶对X射线激光输出特性的影响

Impact of double prepulses and curved target on X-ray laser output intensity

为了探索低泵浦能量下得到X射线激光(XRL)并提高其输出强度的方法,对弯曲靶技术和双预脉冲技术进行了理论分析和数值模拟,模拟结果表明第二预脉冲与第一预脉冲间隔2 ns,主脉冲与第二预脉冲间隔5 ns时效果等离子体增益的时空特性曲线最好。随后在“星光II”激光装置上进行了双预脉冲驱动类氖铬(J=0-1,3p-3s跃迁)XRL实验,得到了28．5 nm的单线X射线激光,结果表明在脉冲结构和泵浦总能量不变情况下XRL输出强度主要与第二预脉冲强度有关,实验结果很好地符合了数值模拟结果．

With aim to enhance the output intensity of X-ray laser （XRL） under the condition of low pump energy, theoretical analysis and numerical simulation were presented on double prepulses and also curved target techniques. The simulation results indicate there is a good pulse structure of 2 ns/5 ns （2nd prepulse dalay/main pulse delay） that can optimize the gain area of plasma. The XRL experiment of Ne like Cr （J=0-1, 3p-3s transition） pumped by the double prepulse was performed on ＂ XingGuang Ⅱ ＂ laser, and a 28.5 nm single line XRL was achieved, as well as other significant results. The XRL output intensity shows much reliance on the last prepulse energy when the delay time is fixed. The experimental and calculation results show good consistency.