超短超强激光与固体靶相互作用中背表面光发射的实验研究

Experimental study of optical emission from the rear surface in ultrashort ultra-intense laser interaction with solid targets

从金属箔背表面测量了超热电子穿越固体靶产生的光发射.光发射积分成像图案呈圆环状,在圆环边缘附近出现局部化明亮光信号确定为光学渡越辐射;光发射光谱在300—500nm之间出现一系列非周期锐利尖峰,在400nm(2ω)附近的尖峰较明显,这个光发射取决于v×B加热机制产生的超热电子束的微束团引起的相干渡越辐射,(v为电子电度,B为磁场强度),光强随靶厚度的增加而减小.

Optical emission generated by hot electrons passing through solid targets is measured from the rear surface of a metallic foil. The integrated image taken by CCD camera shows that the optical emission forms a ring, on the edge of the ring there is a bright localized signal, which is the optical transition radiation （OTR）. The optical emission spectrum shows a series of sharp nonperiodic peaks between 300-500nm, obviously near 400nm（2ω）. The sharp peaks are ascribed to the coherent transition radiation （CTR） of hot electron-beam microbunching generated by ν× B acceleration mechanism. The OTR intensity decreases with the increase of the target thickness.