飞秒激光中超热电子束的传输特性

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(OTR)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100μm的Ta靶背表面观测到渡越辐射(TR)光斑呈现较平滑的圆形结构,而且中心亮度高于周围,这显然包含了非相干与相干渡越辐射的成分,与理论模拟结果比较接近;在复合靶10μm Ta+20μm Cu+1μm Ta背表面观测到TR光斑虽然也呈现大致的圆形结构,但光斑极不均匀,中间有很明显的光斑分裂,大约有两个分离的光斑出现.所有这些现象反映了超热电子束的传输特性.

Transport Characteristics of Superhot Electron Bunches in Femtosecond Laser

For exploring the transport characteristics of superhot electron bunches,the integrated image patterns of optical transition radiation(OTR) were measured at the normal direction of the rear side of targets in the optical CCD camera.The experiment was carried out on the 100 TW laser.The luminescence sign on target surface was brought to the slit of CCD.The transition radiation from the rear side of the target Ta with 100 μm thickness showed a smooth round structure with the center's brightness being higher than that of the around,which included incoherent transition radiation(ITR) and coherent transition radiation(CTR).This was close to the results of the theoretical simulations.The transition radiation from the rear side of the target 10 μm Ta + 20 μm Cu+1 μm Ta showed a ring structure and the facula was bigger and non-uniform with about two separate faculae.These results of the transition radiation could indicate some characteristics of the superhot electron bunches.