强激光辐照纳微阵列产生的高亮度阿秒γ射线辐射与高产额正电子产生
Brilliant attosecond γ-ray emission and high-yield positron production from intense laser-irradiated Nano-Micro array
AI总结：
本研究提出超强激光辐照带衬底纳微阵列的新方案，可高效产生超短超亮阿秒γ射线与超稠密高产额正电子，揭示了转换效率的标度规律与调控方法，为阿秒核科学和高能量密度物理研究提供新途径。
摘要：
我们研究了一种实现高亮度阿秒γ射线辐射与高产额正电子产生的新方案，该方案通过将超强激光脉冲入射到带有衬底的纳微阵列（Nano-Micro array, NMA）上来实现。该方案能够有效实现电子加速与对撞几何构型，进而以高转换效率产生γ射线闪光和正电子团。在激光强度I₀ = 8×10²³ W/cm²的条件下，约27%的激光能量成功转移到γ射线中，约0.7%的激光能量转移到正电子中。最终产生了超短（~440阿秒）、超高亮度（~10²⁴ 光子·秒⁻¹·毫米⁻²·毫弧度⁻² / 0.1%带宽 @ 15 MeV）的γ射线脉冲，以及高产额（1.48×10¹¹个）、超稠密（~10²² cm⁻³）的正电子团。我们发现，激光到光子的转换效率与激光强度呈亚线性标度关系（正比于I₀⁰·⁷⁵），而激光到正电子的转换效率与激光强度呈超线性标度关系（正比于I₀²·⁵）。多维粒子模拟（particle-in-cell simulations）结果表明，γ光子与正电子的产生可通过激光聚焦位置、NMA的长度和间距进行调控。我们得到了NMA中粒子产生的最优条件，表明在极端激光场下，微线阵列比纳米线阵列在粒子产生方面更具优势。此外，我们还讨论了高能量密度（high-energy-density, HED）环境中的正电子湮灭效应。利用NMA的方案将为借助即将建成的10拍瓦激光装置开展阿秒核科学与高能量密度物理研究提供有效途径。
英文摘要：
We investigate a novel scheme for brilliant attosecond γ-ray emission and high-yield positron production, which is accomplished with an ultra-intense laser pulse incident upon a Nano-Micro array (NMA) with substrate incorporated. This scheme is able to realize effectively electron acceleration and colliding geometry. Both the γ-ray flash and positron bunch are then generated with high conversion efficiency. At laser intensity of I_0 = 8 times 10^{23} W/cm^2, ~27% of the laser energy is transferred successfully into the γ-rays, and ~0.7% of the laser energy into the positrons. As a consequence, ultra-short (~440 as) and ultra-brilliant (~10^{24} photons s^{-1} mm^{-2} mrad^{-2} per 0.1%BW @ 15 MeV) γ-ray burst, and high-yield (1.48 times 10^{11}) and overdense (~10^{22} cm^{-3}) positron bunch are generated. We found a sub-linear scaling of laser-to-photon conversion efficiency (proportional to I_0^{0.75}) and a super-linear scaling of laser-to-positron conversion efficiency (proportional to I_0^{2.5}) with the laser intensity. Multi-dimensional particle-in-cell simulations show that particle (γ photon and positron) generation can be manipulated by laser-focusing position, and NMA's length and spacing. Optimal conditions for particle generation in NMAs are obtained, indicating that microwire array has the advantage over nanowire array in particle generation in the extreme laser fields. Furthermore, positron annihilation effect in high-energy-density (HED) environment is discussed. The scheme using NMAs would provide effective avenues toward investigating attosecond nuclear science and HED physics with the coming 10 PW laser facilities.
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