超强脉冲激光辐照固体靶背表面的渡越辐射
Transition radiation from rear surface of solid targets irradiated by ultraintense laser pulse
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摘要: 在超强脉冲激光与固体靶相互作用中，利用光学CCD相机和光学多道分析仪，分别在固体薄膜靶背表面法线方向测量了渡越辐射（TR）积分成像图案和光谱。测量结果显示：TR空间分布图案呈圆环状，而辐射区域有发散角和光强分布；TR光谱在800 nm附近出现尖峰，是激光的基频波，这一现象归因于超热电子束在输运的过程中产生的微束团而引起的相干渡越辐射；如果考虑超热电子的产生和加热机制，共振吸收和真空加热对超热电子都有贡献，其中占主导地位的加热机制则是共振吸收对电子的加热。Abstract: The spatial pattern and spectrum of transition radiation have been measured at the normal direction from the rear surfaces of targets, employing an optical CCD camera and an OMA optical multichannel spectrometer on the 100 TW femtosecond laser facility.The spatial pattern presents a cirque shape, and the region of optical radiation has larger radiation angle and optical intensity distribution. The spectrum of transition radiation presents a sharp peak in the vicinity of 800 nm, which is the laser basic harmonic. That is the result of the coherent transition radiation generated by microbunches of hot electron beams produced in transport. The main acceleration of hot electrons comes from resonance absorption．
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