类锂铝10.57和15.47纳米X光激光增益研究

Li -LIKE Al XI (10.57 AND 15.47nm)X -RAY LASER GAIN EXPERIMENTS

在LF-11(10^(11)W)激光装置上,开展了类锂铝(Al^(10+))的X光激光实验研究。实验中,激光器运行在线聚焦工作状态,波长1.06μm,脉冲宽度约为200ps,能量约20J。线聚焦长12mm,宽约100μm。实验中使用了厚铝靶(1.2μm)和薄膜铝靶(60和94.7nm),用时间积分掠入射光栅谱仪测量线状等离子体轴向XUV谱,用针孔照相机监视线聚焦状态。结果表明,Al^(10+)离子的10.57(3d-5f)和15.47(3d-4f)nm线的强度随等离子体的长度呈现明显的非线性增长。这两条激光跃迁线,用60nm铝靶时,增益系数分别为3.18和2.26cm^(-1);用1.2μm铝靶时,增益系数分别为1.67和0.91cm^(-1);用94.7nm铝靶时,波长为10.57nm线的增益系数为1.78cm^(-1)。说明厚度合适的薄膜靶能获得较高的增益。

Soft x-ray laser gain experiments using Li-like Al XI ions were carried out on the LF -11 (1011 W)laser facility. The single beam of Nd-glass laser was operated at 1.06μm over an energy range of 17-25J for a 200ps pulse. A 100μm- wide and 12mm-long focused line was produced by means of a cylindrical -aspherical lens system. The aluminum targets were slabs and exploding foils (60nm and 94.7nm thick). The extreme ultraviolet spectra (time-integrated) in a region of 2-32nm were recorded on kodak SWR film with a 1 -m grazing -incidence spectrograph. An x -ray pinhole camera photographed the hot plasma in the axial direction. Amplified spontaneous emission was obtained for 10.57nm (3d-5f) and 15.47 nm(3d-4f) transitions of Li -like Al XI ions. The rapid increase of the intensities of the two spectral lines with the target length is very apparent. The gain coefficient of 10.57nm (3d-5f)was 1.78cm-1 for the 94.7nm exploding foil targets. The gain coefficients of 10.57nm (3d-5f)and 15.47nm(3d-4f) were 1.67cm-1 and 0.96cm-1 for 1.2μm targets respectively. Those were 3.18cm-1 and 2.26cm-1 for 60nm exploding foil targets respectively. The result confirms that suitable exploding foil targets can create higher gain coefficient.