# High-Energy Radiation and Pair Production by Coulomb Processes in Particle-In-Cell Simulations

## TL;DR

This paper introduces a Monte Carlo method integrated into particle-in-cell simulations to model high-energy photon and pair production processes, accounting for screening effects in plasmas, validated through tests and applied to electron transport in solid foils.

## Contribution

The paper develops a novel Monte Carlo implementation of Bremsstrahlung, Bethe-Heitler, and Coulomb Trident processes within PIC simulations, including screening effects and a pairwise interaction algorithm.

## Key findings

- Validated the Monte Carlo implementation with multiple tests.
- Demonstrated the significance of plasma expansion on electron energy losses.
- Provided insights into photon and pair production during high-energy electron transport.

## Abstract

We present a Monte Carlo implementation of the Bremsstrahlung, Bethe-Heitler and Coulomb Trident processes into the particle-in-cell (PIC) simulation framework. In order to address photon and electron-positron pair production in a wide range of physical conditions, we derive Bremsstrahlung and Bethe-Heitler cross sections taking account of screening effects in arbitrarily ionized plasmas. Our calculations are based on a simple model for the atomic Coulomb potential that describes shielding due to both bound electrons, free electrons and ions. We then describe a pairwise particle interaction algorithm suited to weighted PIC plasma simulations, for which we perform several validation tests. Finally, we carry out a parametric study of photon and pair production during high-energy electron transport through micrometric solid foils. Compared to the zero-dimensional model of J. Myatt et al. [Phys. Rev. E 76, 066409 (2009)], our integrated one-dimensional simulations pinpoint the importance of the electron energy losses resulting from the plasma expansion.