Energy Loss of High-Energy Particles in Particle-in-Cell Simulation

TL;DR

This paper investigates how high-energy particles lose energy in particle-in-cell simulations, revealing that the energy loss is exaggerated due to limited particle numbers and emphasizing the need for larger particle counts in simulations.

Contribution

It demonstrates that energy loss in PIC simulations mirrors real plasma behavior but is artificially amplified by low particle numbers, impacting simulation accuracy.

Findings

Energy loss rate depends on plasma electron count within the skin depth volume.

Artificial energy loss can be significantly exaggerated in PIC simulations.

Increasing particle numbers reduces artificial energy loss effects.

Abstract

When a charged particle moves through a plasma at a speed much higher than the thermal velocity of the plasma, it is subjected to the force of the electrostatic field induced in the plasma by itself and loses its energy. This process is well-known as the stopping power of a plasma. In this paper we show that the same process works in particle-in-cell (PIC) simulations as well and the energy loss rate of fast particles due to this process is mainly determined by the number of plasma electrons contained in the electron skin depth volume. However, since there are generally very few particles in that volume in PIC simulations compared with real plasmas, the energy loss effect can be exaggerated significantly and can affect the results. Therefore, especially for the simulations that investigate the particle acceleration processes, the number of particles used in the simulations should be chosen large enough to avoid this artificial energy loss.