预脉冲对超短激光与薄膜靶相互作用加速产生质子的影响  

Influence of Laser Prepulse on Proton Acceleration Using Ultra-short Laser Interaction With Thin-Foil

作　　者：路建新[1] 兰小飞[1] 席晓峰[1] 王雷剑[1] 黄永盛[1] 杨大为[1] 汤秀章[1] 

机构地区：[1]中国原子能科学研究院核技术应用研究所,北京102413

出　　处：《原子能科学技术》2013年第4期637-640,共4页Atomic Energy Science and Technology

基　　金：国家自然科学基金资助项目(10834008;11105234);973计划资助项目(2011CB808104)

摘　　要：采用波长为744nm、聚焦功率密度为6×1016 W/cm2的超短激光分别与两种不同厚度的铝薄膜靶相互作用,根据鞘层加速机制在靶后法线方向测量质子束角分布和能谱随靶厚度的变化,研究了预脉冲对质子加速的影响。随着薄膜靶厚度的降低,质子计数迅速增加,但当薄膜靶厚度太薄时,激光预脉冲形成的预等离子体影响了薄膜靶的面型,导致质子横向发散角迅速增加,而薄膜靶面型的破坏减少了激光与等离子体相互作用过程中的电子回流,从而降低了超热电子的产生和鞘层加速电场的维持,影响了质子的加速能谱。因此,超短脉冲激光与薄膜靶相互作用加速产生质子束,应尽量降低预脉冲,不能采用太薄的薄膜靶,以避免预等离子体影响薄膜靶的面型,导致质子的能量降低、发散角增大。Influence of laser prepulse on ultra-short laser-driven proton acceleration was investigated by different spatial distributions and energy spectra between different foil- targets, and spatial distribution and energy spectrum were measured at the normal direc- tion of target rear according to the target normal sheath acceleration （TNSA）. The laser wavelength is 744 nm and peak focal intensity is about 6×10^16 W/cm2. Proton amount increased with decreasing the target thickness, but the divergence angle also increased with decreasing the target thickness as a result of the target surface-shape destroyed by the laser prepulse. The energy spectra recorded by a Thomson mass spectrometer were also influenced by the decrease of hot electron recycling attributed to the destroyed sur- face-shape. The results show that the foil target in the laser-driven proton accelerationexperiments can not be too thin.

关 键 词：超短激光 预脉冲 质子 薄膜靶 

分 类 号：O434[机械工程—光学工程] TL65[理学—光学]