LULI-CNRS, Ecole Polytechnique, CEA, Université Paris-Saclay, F-91128 Palaiseau cedex, France.
Centre for Plasma Physics, School of Mathematics and Physics, The Queen's University of Belfast, Belfast BT7 1NN, United Kingdom.
Phys Rev Lett. 2019 Jan 18;122(2):025001. doi: 10.1103/PhysRevLett.122.025001.
The propagation of fast electron currents in near solid-density media was investigated via proton probing. Fast currents were generated inside dielectric foams via irradiation with a short (∼0.6 ps) laser pulse focused at relativistic intensities (Iλ^{2}∼4×10^{19} W cm^{-2} μm^{2}). Proton probing provided a spatially and temporally resolved characterization of the evolution of the electromagnetic fields and of the associated net currents directly inside the target. The progressive growth of beam filamentation was temporally resolved and information on the divergence of the fast electron beam was obtained. Hybrid simulations of electron propagation in dense media indicate that resistive effects provide a major contribution to field generation and explain well the topology, magnitude, and temporal growth of the fields observed in the experiment. Estimations of the growth rates for different types of instabilities pinpoints the resistive instability as the most likely dominant mechanism of beam filamentation.
通过质子探测研究了近固体密度介质中快电子电流的传播。通过将短（约 0.6 ps）激光脉冲聚焦在相对论强度（Iλ^{2}∼4×10^{19} W cm^{-2} μm^{2}）下辐照介电泡沫，在介电泡沫内部产生了快电流。质子探测提供了对电磁场演变和相关净电流的时空分辨特征的直接探测，这些探测是在目标内部进行的。光束分裂的渐进增长在时间上得到了分辨，并且获得了关于快电子束发散的信息。在密集介质中电子传播的混合模拟表明，电阻效应对场的产生有很大的贡献，并且很好地解释了实验中观察到的场的拓扑结构、大小和时间增长。对不同类型不稳定性的增长率的估计表明，电阻不稳定性是束分裂的最可能的主导机制。
