The Suppression of Radiation Reaction and Laser Field Depletion in Laser-Electron beam interaction

TL;DR

This study uses PIC simulations to show that radiation reaction effects are suppressed in tightly focused laser-electron interactions due to ponderomotive forces, which also cause laser energy depletion.

Contribution

It demonstrates the suppression of radiation reaction effects and laser energy depletion in tightly focused laser-electron interactions through detailed PIC simulations.

Findings

Radiation reaction effects are suppressed by ponderomotive forces.

Laser energy is absorbed and depleted during interaction.

Electron beam energy must be carefully chosen to observe RR effects.

Abstract

The effects of radiation reaction (RR) have been studied extensively by using the ultraintense laser interacts with the counter-propagating relativistic electron. At the laser intensity at the order of $10^{23}$ W/cm$^2$, the effects of RR are significant in a few laser period for a relativistic electron. However, the laser at such intensity is tightly focused and the laser energy is usually assumed to be fixed. Then, the signal of RR and energy conservation cannot be guaranteed. To assess the effects of RR in a tightly focused laser pulse and the evolution of the laser energy, we simulate this interaction with a beam of $10^9$ electrons by means of Particle-in-Cell (PIC) method. We observed that the effects of RR are suppressed due to the ponderomotive force and accompanied by a non-negligible amount of laser field energy reduction. This is due to the ponderomotive force that prevents the electrons from approaching the center of the laser pulse and leads to the interaction at weaker field region. At the same time, the laser energy is absorbed through ponderomotive acceleration. Thus, the kinetic energy of the electron beam has to be carefully selected such that the effects of RR become obvious.