飞秒激光产生的X射线双光谱成像

在微介观诊断中往往因为空间限制，选择具有亮度高、单色性好、对比度强的特征谱线，而忽略了轫致辐射谱线。率先实验设计了特征谱线和轫致辐射谱线的双光谱诊断X射线光源的方法，在中国工程物理研究院“星光Ⅲ”激光装置飞秒激光束靶室上进行实验，激光功率密度大于1.6×1018 W/cm2，脉宽为30 fs，45°入射靶面。在入射靶前侧，设计了用于特征光谱成像的针孔成像光路，获得Cu纳米颗粒靶产生的特征X射线的焦斑图像，为76 μm，大于刃边方法测得半径为54 μm的焦斑。在靶后侧，设计了轫致辐射成像光路，利用PIX射线CCD获得2×5的圆形Ta组图像。实验表明，利用双光谱成像设计合理，适合微介观材料动态诊断，提高诊断效率。

X-ray dual-spectrum imaging produced by femtosecond laser

To obtain an X-ray source to diagnose micro-mesoscopic state of material with high brightness, good monochromaticity and good contrast in pump-probe technology, and to often ignore the bremsstrahlung line, hence we designed a dual-spectrum diagnostic X-ray source experiments using characteristic and bremsstrahlung spectra. The experiment was carried out on the femtosecond laser beam of the “Xingguang Ⅲ” laser facility of China Academy of Engineering Physics. The laser power density is more than 1.6×1018 W/cm2, with the pulse width of 30 fs by 45° to the target surface. On the other side of the target normal line, the pinhole imaging optical path for characteristic spectral imaging was designed to obtain the focal spot image of 76 μm from the characteristic X-ray generated by the Cu nanoparticle target, larger than the average focus spot of 54 μm obtained by the knife-edge method. On the back side of the Cu target, the bremsstrahlung imaging optical path was designed, and the PIX-ray CCD was used to obtain 2×5 circular Ta group images. Experiments show that the dual-spectral imaging design is reasonable, which is suitable for dynamic diagnosis of micro-mesoscopic materials, and improve diagnosis efficiency.