Laboratori Nazionali di Frascati, 00044 Frascati, Italy.
Racah Institute of Physics, Hebrew University, 91904 Jerusalem, Israel.
Sci Rep. 2016 Oct 7;6:35000. doi: 10.1038/srep35000.
Highly energetic electrons are generated at the early phases of the interaction of short-pulse high-intensity lasers with solid targets. These escaping particles are identified as the essential core of picosecond-scale phenomena such as laser-based acceleration, surface manipulation, generation of intense magnetic fields and electromagnetic pulses. Increasing the number of the escaping electrons facilitate the late time processes in all cases. Up to now only indirect evidences of these important forerunners have been recorded, thus no detailed study of the governing mechanisms was possible. Here we report, for the first time, direct time-dependent measurements of energetic electrons ejected from solid targets by the interaction with a short-pulse high-intensity laser. We measured electron bunches up to 7 nanocoulombs charge, picosecond duration and 12 megaelectronvolts energy. Our 'snapshots' capture their evolution with an unprecedented temporal resolution, demonstrat- ing a significant boost in charge and energy of escaping electrons when increasing the geometrical target curvature. These results pave the way toward significant improvement in laser acceleration of ions using shaped targets allowing the future development of small scale laser-ion accelerators.
在短脉冲高强度激光与固体靶相互作用的早期阶段，会产生高能量电子。这些逃逸粒子被认为是皮秒级现象的核心，如基于激光的加速、表面处理、强磁场和电磁脉冲的产生。增加逃逸电子的数量有助于所有情况下的后期过程。到目前为止，这些对于先驱者们来说很重要的证据都是间接记录的，因此无法对控制机制进行详细研究。在这里，我们首次报告了通过短脉冲高强度激光与固体靶相互作用直接测量从固体靶中射出的高能电子。我们测量了高达 7 纳库仑电荷量、皮秒持续时间和 1200 兆电子伏特能量的电子束。我们的“快照”以前所未有的时间分辨率捕获了它们的演化，当增加几何目标曲率时，逃逸电子的电荷量和能量显著增加。这些结果为使用成形靶提高激光离子加速铺平了道路，允许未来开发小型激光离子加速器。
