Modeling of the driver transverse profile for laser wakefield electron acceleration at APOLLON Research Facility

TL;DR

This paper demonstrates that incorporating measured laser transverse asymmetries into PIC simulations significantly improves the accuracy of modeling electron acceleration in laser wakefield experiments at the APOLLON facility.

Contribution

The study introduces a method to accurately retrieve the laser electric field from fluence measurements and shows that including these asymmetries in simulations enhances agreement with experimental results.

Findings

PIC simulations with measured laser asymmetries match experimental electron spectra

Laser focal spot asymmetries affect electron charge and energy

Modified Gerchberg-Saxton algorithm effectively retrieves laser electric field

Abstract

The quality of electron bunches accelerated by laser wakefields is highly dependant on the temporal and spatial features of the laser driver. Analysis of experiments performed at APOLLON PW-class laser facility shows that spatial instabilities of the focal spot, such as shot-to-shot pointing fluctuations or asymmetry of the transverse fluence, lead to charge and energy degradation of the accelerated electron bunch. It is shown that PIC simulations can reproduce experimental results with a significantly higher accuracy when the measured laser asymmetries are included in the simulated laser's transverse profile, compared to simulations with ideal, symmetric laser profile. A method based on a modified Gerchberg-Saxton iterative algorithm is used to retrieve the laser electric field from fluence measurements in vacuum in the focal volume, and accurately reproduce experimental results using PIC simulations, leading to simulated electron spectra in close agreement with experimental results, for the accelerated charge, energy distribution and pointing of the electron beam at the exit of the plasma.