飞秒激光-薄膜靶相互作用中超热电子产额和激光转化效率

 在激光能量130 mJ（靶面），脉宽60 fs，波长800 nm，对比度1∶10^-6，激光与靶法线成45°夹角，P偏振，靶面激光峰值功率密度约为7.0×10¹⁷ W·cm^-2，无预脉冲的条件下，采用电子谱仪与经γ标准源标定的LiF热释光探测器（TLD）相配合，测量了飞秒激光-薄膜靶相互作用中产生的超热电子能谱。根据所测的能谱，推算出超热电子的产额和激光能量转化为超热电子能量的效率，在靶法线方向分别为1.19×10¹⁰/sr和4.55%/sr，在激光反射方向分别为1.83×10⁹/sr和0.76%/sr。结果显示，不同方向的超热电子产额和激光转化效率有所不同，原因在于激光-等离子体相互作用产生的超热电子构成各向异性的分布。

Yield of hot electrons and conversion efficiency of laser energy in femtosecond laser-foil targets

The energy spectra of hot electrons have been measured using the magnetic spectrometers, fitted with the LiF thermoluminescent dosimeter (TLD) which were calibrated using Cs~(137) γ-ray sources, in the interaction of a 130 mJ, 60 fs, 800 nm, 1∶10~(-6), 7.0×10~(17) W·cm~(-2) P-polarized laser incidence on Cu foil target at an angle of 45° with respect to the target normal without any prepulse. The yield of hot electrons and the conversion efficiency of laser energy to energy of hot electrons are 1.19×10~(10)/sr and 4.55%/sr at the normal of target and are 1.83×10~9/sr and 0.76%/sr at the specular direction of laser, which were deduced from the energy spectra of hot electrons. They were different at various direction because of the hot electrons produced in the interaction of laser-plasma constituted an anisotropy distribution.