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LiF在激光驱动高压实验中是比较常见的窗口材料,其在冲击下透射或反射可见诊断光是作为窗口材料的重要特性.在神光Ⅲ原型激光装置上开展了带LiF窗口的铝样品准等熵压缩实验,采用任意反射面速度干涉仪诊断获得准等熵压缩样品(CH/Al/LiF)的反射率.实验结果表明在准等熵压缩后期反射率诊断出现致盲现象.为此,建立了带透明窗口的样品对诊断光的反射率模型,模型考虑了窗口LiF的透明性变化.模型计算的CH/Al/LiF样品对可见光的反射率时间演化过程与实验结果符合较好.研究结果表明:LiF中压缩波追赶逐渐形成强冲击波,显著降低了LiF的透明性,并最终发生致盲现象;第一性原理方法所给出的LiF的能带间隙偏低1—2 eV;该实验中,LiF的透明性完全消失时,LiF中波头处的温度约为l eV,压力为2—3 Mbar.
LiF is a relatively common window material in laser-driven high-voltage experiments, which is transmitted or reflected under impact as an important feature of the window material.An aluminum sample with LiF window Entropy compression experiment, and the reflectivity of the quasi-isentropic-compressed sample (CH / Al / LiF) was obtained by using an arbitrary reflection surface velocity interferometer.The experimental results show that the reflectivity of the quasi-isentropic compression is blinded.Therefore, The model of the reflectivity for the diagnostic light with a transparent window was taken into consideration in the model and the transparency of the LiF window was taken into account in the model.The temporal evolution of the reflectivity of visible light in the CH / Al / LiF sample calculated by the model was in good agreement with the experimental results It is shown that the compressional wave in LiF catches up gradually to form a strong shock wave, which obviously reduces the transparency of LiF and eventually leads to blinding. The LiF band gap given by the first-principle method is 1-2 eV lower. , The transparency of LiF disappears completely, the temperature of the wave front in LiF is about 1 eV and the pressure is 2-3 Mbar.