Wang W-M, Gibbon P, Sheng Z-M, Li Y-T, Zhang J
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, CAS, Beijing 100190, China.
Beijing Advanced Innovation Center for Imaging Technology, Department of Physics, Capital Normal University, Beijing 100048, China.
Phys Rev E. 2017 Jul;96(1-1):013201. doi: 10.1103/PhysRevE.96.013201. Epub 2017 Jul 5.
We investigate how next-generation laser pulses at 10-200PW interact with a solid target in the presence of a relativistically underdense preplasma produced by amplified spontaneous emission (ASE). Laser hole boring and relativistic transparency are strongly restrained due to the generation of electron-positron pairs and γ-ray photons via quantum electrodynamics (QED) processes. A pair plasma with a density above the initial preplasma density is formed, counteracting the electron-free channel produced by hole boring. This pair-dominated plasma can block laser transport and trigger an avalanchelike QED cascade, efficiently transferring the laser energy to the photons. This renders a 1-μm scale-length, underdense preplasma completely opaque to laser pulses at this power level. The QED-induced opacity therefore sets much higher contrast requirements for such a pulse in solid-target experiments than expected by classical plasma physics. Our simulations show, for example, that proton acceleration from the rear of a solid with a preplasma would be strongly impaired.
我们研究了在由放大自发辐射（ASE）产生的相对论性欠稠密预等离子体存在的情况下，10 - 200拍瓦的下一代激光脉冲如何与固体靶相互作用。由于通过量子电动力学（QED）过程产生电子 - 正电子对和γ射线光子，激光打孔和相对论性透明受到强烈抑制。形成了一种密度高于初始预等离子体密度的对等离子体，抵消了打孔产生的无电子通道。这种以对为主的等离子体可以阻止激光传输并触发雪崩式QED级联，有效地将激光能量转移到光子上。这使得在该功率水平下，1微米标度长度的欠稠密预等离子体对激光脉冲完全不透明。因此，QED诱导的不透明度在固体靶实验中为此类脉冲设定了比经典等离子体物理预期更高的对比度要求。例如，我们的模拟表明，在有预等离子体的情况下，从固体后部进行质子加速会受到严重阻碍。
