Backlight imaging by X-ray irradiation from high-intensity femtosecond-laser driven gas targets
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摘要: 在拍瓦级飞秒激光装置上完成了两轮激光驱动甲烷气体靶的实验，用产生的X光源配合SCCD（转换屏+CCD相机）对小型金属器件背光成像，采用经验公式和PIC数值模拟方法分别预估了超热电子温度，得到X光能量分别为377 keV和130 keV，据此两轮实验分别选择1.3 mm和0.8 mm厚度的轫致辐射体。分析比较了两轮实验背光成像质量。通过对次轮实验图像中铝、铜金属台阶灰度值曲线的分析求得X光的能量分别为49 keV和92 keV，这表明采用PIC数值模拟方法得到的X光能量更加符合实验结果。Abstract: Two experiments of laser-driven methane jet are performed on a petawatt laser, and the X-ray emitted is used to backlight small-size metal objects with SCCD(scintillator screen + CCD camera). Converters with different thicknesses are chosen considering the temperature of hot electrons which is evaluated both by the empirical formula and by the particle-in-cell (PIC) code. The X-ray energies of 377 keV and 130 keV are estimated by the two methods respectively. Consequently, converters with 1.3 mm and 0.8 mm thicknesses are chosen. Photon energies of 49 keV and 92 keV are obtained by grayscale curves of aluminum and copper step-wedges in the second experiment. It is demonstrated that the photon energy deduced from the PIC code agrees with the experimental result.
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Key words:
- femtosecond laser /
- gas target /
- cluster /
- X-ray /
- hot electrons /
- energy spectrum
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