利用渡越辐射研究超热电子束的传输特性
Transport characteristic of hot electron bunches in solid targets by transition radiation
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摘要: 为了探索超热电子束的传输特性，利用光学CCD相机在靶背法线方向测量了光学渡越辐射积分成像图案。实验在100 TW掺钛蓝宝石激光器上进行，飞秒激光与固体靶作用后，靶表面发光信号由空间分辨装置聚焦成像并引到CCD狭缝上。在厚度为20 μm的Ta靶背表面观测到渡越辐射光斑呈现较平滑的圆形结构，而且中心亮度高于周围，这包含了非相干与相干渡越辐射的成分，与理论模拟结果接近；在厚度为100 μm的Ta靶背表面观测到渡越辐射光斑呈现出星状结构，光斑较小，与高能质子发射出现的星状结构极其相似；在复合靶背表面观测到渡越辐射光斑虽然也呈现大致的圆形结构，但光斑较大，而且极不均匀，中间有很明显的光斑分裂。Abstract: For exploring the transport characteristic of hot electron bunches, the integrated image pattern of optical transition radiation were measured at the normal direction of the rear side of targets employing the optical CCD camera. The experiment was carried out on the 100 TW laser. The transition radiation facula on the rear side of a 20 μm thick target Ta was a smooth round structure with the center brighter than the periphery, indicating incoherent transition radiation and coherent transition radiation, which is close to the results of the theoretical simulations. For a 100 μm thick target Ta, the facula was a star-structure and became smaller, which resembles a star-structure of the energetic proton emission. For a 10 μm Ta + 10 μm Cu+5 μm Ta composite target, the facula was a ring s
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