# The high density $\gamma$-ray emission and dense positron production via multi-lasers driven circular target

## TL;DR

This paper demonstrates that a circular diamond-like carbon target irradiated by multiple high-intensity lasers significantly enhances gamma-ray emission and dense positron production, with potential applications in various scientific fields.

## Contribution

The study introduces a novel circular target design and laser configuration that substantially improves gamma-ray and positron yields compared to traditional methods.

## Key findings

- Achieved gamma-photon density of 5164 n_c with multi-lasers and circular target.
- Produced 2.7 x 10^{11} positrons with 230 MeV energy.
- Enhanced gamma-ray and positron production efficiency through target and laser optimization.

## Abstract

A diamond-like carbon circular target is proposed to improve the $\gamma$-ray emission and pair production with lasers intensity of $8\times 10^{22} ~\mathrm{W/cm^2}$ by using two-dimensional particle-in-cell simulations with quantum electrodynamics. It is found that the circular target can significantly enhance the density of $\gamma$-photons than plane target when two colliding circularly polarized lasers irradiate the target. By multi-lasers irradiate the circular target, the optical trap of lasers can prevent the high energy electrons accelerated by laser radiation pressure from escaping. Hence, high density as $5164 n_c$ $\gamma$-photons is obtained through nonlinear Compton back-scattering. Meanwhile, $2.7 \times 10^{11}$ positrons with average energy of $230 ~\mathrm{MeV}$ is achieved via multi-photon Breit-Wheeler process. Such ultrabright $\gamma$-ray source and dense positrons source can be useful to many applications. The optimal target radius and laser mismatching deviation parameters are also discussed in detail.