In the laser plasma interaction of quantum electrodynamics (QED)-dominated regime, γ-rays are generated due to synchrotron radiation from high-energy electrons traveling in a strong background electromagnetic field. With the aid of 2D particle-in-cell code including QED physics, we investigate the preplasma effect on the γ-ray generation during the interaction between an ultraintense laser pulse and solid targets. We found that with the increasing preplasma scale length, the γ-ray emission is enhanced significantly and finally reaches a steady state. Meanwhile, the γ-ray beam becomes collimated. This shows that, in some cases, the preplasmas will be piled up acting as a plasma mirror in the underdense preplasma region, where the γ-rays are produced by the collision between the forward electrons and the reflected laser fields from the piled plasma. The piled plasma plays the same role as the usual reflection mirror made from a solid target. Thus, a single solid target with proper scale length preplasma can serve as a manufactural and robust γ-ray source.

中文翻译：

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用前等离子从超强激光照射的固体目标产生伽马射线

在以量子电动力学 (QED) 为主的激光等离子体相互作用中，γ 射线是由在强背景电磁场中传播的高能电子的同步辐射产生的。借助包括 QED 物理在内的二维粒子细胞代码，我们研究了在超强激光脉冲与固体目标之间的相互作用过程中，前等离子体对 γ 射线产生的影响。我们发现随着前等离子体尺度长度的增加，γ射线发射显着增强并最终达到稳定状态。同时，γ射线束被准直。这表明，在某些情况下，前等离子体将作为等离子体镜堆积在低密度的前等离子体区域中，其中γ射线是由前向电子与堆积等离子体的反射激光场之间的碰撞产生的。堆积的等离子体与通常由固体目标制成的反射镜所起的作用相同。因此，具有适当尺度长度的前等离子体的单个固体靶可以用作制造和稳健的 γ 射线源。