# Optimal Parameters for Radiation Reaction Experiments

## TL;DR

This paper identifies optimal experimental parameters for observing quantum radiation reaction effects in high-intensity laser-electron interactions, emphasizing the electron energy spread as a key distinguishing factor between models.

## Contribution

It provides a simulation-based framework to determine experimental conditions that can differentiate classical and quantum radiation reaction models.

## Key findings

- Photon spectrum energy distinguishes classical and quantum models.
- Electron energy spread change differentiates stochastic and deterministic quantum models.
- Experiments with 500 MeV electrons at a_0=10 can differentiate models in under 30 shots.

## Abstract

As new laser facilities are developed with intensities on the scale of 10^22 - 10^24 W cm^-2 , it becomes ever more important to understand the effect of strong field quantum electrodynamics processes, such as quantum radiation reaction, which will play a dominant role in laser-plasma interactions at these intensities. Recent all-optical experiments, where GeV electrons from a laser wakefield accelerator encountered a counter-propagating laser pulse with a_0 > 10, have produced evidence of radiation reaction, but have not conclusively identified quantum effects nor their most suitable theoretical description. Here we show the number of collisions and the conditions required to accomplish this, based on a simulation campaign of radiation reaction experiments under realistic conditions. We conclude that while the critical energy of the photon spectrum distinguishes classical and quantum-corrected models, a better means of distinguishing the stochastic and deterministic quantum models is the change in the electron energy spread. This is robust against shot-to-shot fluctuations and the necessary laser intensity and electron beam energies are already available. For example, we show that so long as the electron energy spread is below 25%, collisions at a_0 = 10 with electron energies of 500 MeV could differentiate between different quantum models in under 30 shots, even with shot to shot variations at the 50% level.