We propose to use a 10 petawatt (PW) laser irradiating onto a target with a concave surface, which can focus the laser beam and attain a more intense laser field, so as to increase both the yield and mean energy of emitted γ-rays. 2D particle-in-cell simulation results show that the peak electric field after the reflection of the laser from the target in this new scheme can reach ∼ 1.8 times as high as that in the plane target case. Such an enhanced laser field enables an increase in the number of hot electrons in front of the incident plane and raises the probability rate of generating high-energy γ-rays significantly by non-linear Compton scattering. As a result, 1.5 × 10 13 γ photons with a mean energy of 9.2 MeV are obtained. These photons mainly point toward two directions and distribute in pulses with the duration of each pulse of ∼ 400 as. A brightness as high as 3.6 × 10 25 photons / ( mm 2 mrad 2 s 0.1 % BW ) is obtained in one pulse. Compared to no positron observed for a plane target, a positron yield of 3.0 × 10 8 can be achieved in this new scheme.

中文翻译：

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超强激光与凹面目标相互作用产生的高能 γ 射线密集

我们建议使用 10 拍瓦 (PW) 激光照射具有凹面的目标，它可以将激光束聚焦并获得更强烈的激光场，从而增加发射的 γ 射线的产量和平均能量。二维粒子胞内模拟结果表明，在这种新方案中，激光从目标反射后的峰值电场可以达到平面目标情况下的 1.8 倍。这种增强的激光场能够增加入射平面前的热电子数量，并通过非线性康普顿散射显着提高产生高能γ射线的概率。结果，获得了平均能量为9.2 MeV的1.5 × 10 13 γ光子。这些光子主要指向两个方向并以脉冲形式分布，每个脉冲的持续时间约为 400 as。在一个脉冲中获得高达 3.6 × 10 25 光子/（mm 2 mrad 2 s 0.1 % BW）的亮度。与没有观察到平面目标的正电子相比，在这个新方案中可以实现 3.0 × 10 8 的正电子产率。