准直准单能靶面电子加速实验研究  

Generation of collimated quasi-monoenergetic target surface electron beams in laser solid interaction

作　　者：马勇[1] 李明华[1] 陈黎明[1] 

机构地区：[1]中国科学院物理研究所,光物理重点实验室,北京100190

出　　处：《中国科学：物理学、力学、天文学》2015年第2期103-108,共6页Scientia Sinica Physica,Mechanica & Astronomica

基　　金：国家重点基础研究发展计划(编号:2013CBA01501);科技部国家重大科学仪器设备开发专项(编号:2012YQ120047);国家自然科学基金(批准号:11334013,11121504);中国科学院重点资助项目

摘　　要：实验上使用大能量、亚ps激光脉冲大角度入射固体靶,获得了沿靶面方向定向传播、发散角仅有2°、峰值能量为3–4 Me V的准直、准单能电子束.实验发现激光对比度对靶面电子束的产生起到了至关重要的作用,最佳的对比度为5×10-6.在此最优化条件下,通过背向散射光谱分析发现,共振吸收激发的等离子体波加速可能是电子的主要加速机制.探针光阴影成像及等离子体自发光的精细结构显示,预脉冲与固体靶相互作用中产生了尺度100μm左右的过临界密度预等离子体.这种等离子体的作用类似于等离子体反射镜,使得激光脉冲被限制在预等离子体区与靶面之间,因而最终造成了电子束沿靶面方向的导引.这种靶面电子束因其合适的能量范围、高度的准直性及沿靶面方向定向传播的特性有望在惯性约束聚变尤其是锥靶快点火中得到应用.Collimated quasi-monoenergetic target surface electron beams with divergence angle as small as 2° and energy peaked at 3-4 MeV were first generated in 200 TW sub-picoseconds laser interacted with solid target. We found that the laser contrast plays an important role in generating such kind of target surface electron beams. Resonant absorption might be the main heating regime through Back Scattering spectra analyses. Fine structures of shadow imaging of probe beam and plasma self-emission illustrate that over dense pre-plasma were generated. Such pre-plasma acts as a plasma reflective mirror which confines the main pulse propagating in the channel between pre-plasma and target surface and eventually guiding the electron beams along target surface. Such kind of electron beams might be used as an igniter in inertial confinement fusion, especially in the fast ignition concept.

关 键 词：超短超强激光 等离子体 靶面电子加速 

分 类 号：O572.322[理学—粒子物理与原子核物理]