脉冲Nd∶YAG激光诱导钼等离子体UTA辐射特性研究

Analysis of UTA Spectra of Nd∶YAG Pulse Laser Produced Mo Plasmas

利用Nd∶YAG激光作用于真空腔内的高纯固体钼(Mo)靶产生等离子体,并测量了不同脉冲激光功率密度下Mo等离子体在2~9nm范围内的时间积分光谱。基于碰撞辐射平衡模型(CRM)和Cowan程序计算得到不可分辨跃迁峰(UTA)原子光谱数据,并假设谱线展宽为高斯线形,获得了在不同电子温度和电子密度下的理论模拟光谱,模拟光谱与实验光谱吻合的较好。实验与理论研究光谱表明:MoⅩⅥ-MoⅩⅫ离子的3d-4f不可分辨跃迁峰位于水窗波段,通过控制脉冲激光参数和采用合适的等离子体约束条件,获得水窗辐射波段Mo离子的高丰度布居,有望将激光Mo等离子用于单脉冲活体细胞显微成像水窗光源。

The high purity molybdenum(Mo)sample were irradiated with the Nd∶YAG pulse las er t o generate plasmas in a vacuum chamber.The time integrated emission spectrosco py of laser produced Mo plasmas was measured in the spectral range of 2~9 nm us ing different laser power density.Based on collision-radiative model(CRM)an d unresolved transition arrays(UTA)data of highly charged Mo ions calculated w ith Cowan code,the theoretical synthetic spectra at different electron tempera tu re and electron density were obtained assuming individual spectral line obeyed G aussian broadening.Fair agreements between simulated and experimental spectra h ave been achieved.Experimental and theoretical spectra show that the UTAs of 3d-4f transitions in MoⅩⅥ-ⅩⅫions have several peak s lying in water wi ndow region.By controlling the laser pulse parameters and optimizing the plasma s confinement conditions,it is expected to obtain high ion fraction of highly charged Mo ions irradiating photons in water window wavelength region,showing the potential for water window living cell microscopic imaging sources in the fut ure.