Brilliant attosecond γ-ray emission and high-yield positron production from intense laser-irradiated nano-micro array

Abstract

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 a 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 a laser intensity of 8 × 1023 W/cm2, ∼27% of the laser energy is transferred successfully into γ-rays and ∼0.7% of the laser energy into the positrons. As a consequence, ultra-short (∼440 as) and ultra-brilliant (∼1024 photons s−1 mm−2 mrad−2 per 0.1%BW at 15 MeV) γ-ray burst and high-yield (1.48 × 1011) and overdense (∼1022 cm−3) positron bunches are generated. We found a sub-linear scaling of laser-to-photon conversion efficiency (∝I00.75) and a superlinear scaling of laser-to-positron conversion efficiency (∝I02.5) with the laser intensity. Multi-dimensional particle-in-cell simulations show that particle (γ photon and positron) generation can be manipulated by the laser-focusing position and NMA's length and spacing. Optimal conditions for particle generation in NMAs are obtained, indicating that microwire arrays have the advantage over nanowire arrays in particle generation in the extreme laser fields. Furthermore, positron annihilation effects in the high-energy-density (HED) environment are discussed. The scheme using NMAs would provide effective avenues toward investigating attosecond nuclear science and HED physics with the coming 10 PW laser facilities.