We report the observation of longitudinal filamentation of an electron-positron pair plasma in a beam-driven QED cascade. The filaments are created in the “pair-reflection” regime, where the generated pairs are partially stopped and reflected in the strong laser field. The density filaments form near the center of the laser pulse and have diameters similar to the laser wavelength. They develop and saturate within a few laser cycles and do not induce sizable magnetostatic fields. We rule out the onset of two-stream instability or Weibel instability and attribute the origin of pair filamentation to laser ponderomotive forces. The small plasma filaments induce strong scattering of laser energy to large angles, serving as a signature of collective QED plasma dynamics.

中文翻译：

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光束驱动 QED 级联中的成对丝化和激光散射

我们报告了在光束驱动 QED 级联中电子-正电子对等离子体纵向丝化的观察。灯丝是在“对反射”状态下产生的，其中生成的对在强激光场中部分停止并反射。密度丝在激光脉冲中心附近形成，其直径与激光波长相似。它们在几个激光周期内形成并饱和，并且不会产生相当大的静磁场。我们排除了双流不稳定性或韦贝尔不稳定性的出现，并将成对丝化的起源归因于激光有质动力。小等离子体灯丝引起激光能量向大角度的强烈散射，作为集体 QED 等离子体动力学的标志。