Optimization of laser-plasma injector via beam loading effects using ionization-induced injection

TL;DR

This paper demonstrates how tailoring the density profile and nitrogen concentration in a gas cell can optimize laser-plasma accelerators to produce high-quality electron beams with specific energy and spread.

Contribution

It introduces a method to control electron beam properties via beam loading effects and density profile tailoring in ionization-induced injection.

Findings

Achieved 150 MeV electron beams with 4% energy spread.

Controlled electron injection through nitrogen concentration tuning.

Demonstrated robustness of the optimized configuration.

Abstract

Simulations of ionization induced injection in a laser driven plasma wakefield show that high-quality electron injectors in the 50-200 MeV range can be achieved in a gas cell with a tailored density profile. Using the PIC code Warp with parameters close to existing experimental conditions, we show that the concentration of $\mathrm{N_2}$ in a hydrogen plasma with a tailored density profile is an efficient parameter to tune electron beam properties through the control of the interplay between beam loading effects and varying accelerating field in the density profile. For a given laser plasma configuration, with moderate normalized laser amplitude, $a_0=1.6$ and maximum electron plasma density, $n_{e0}=4\times 10^{18}\,\mathrm{cm^{-3}}$, the optimum concentration results in a robust configuration to generate electrons at 150~MeV with a rms energy spread of 4\% and a spectral charge density of 1.8~pC/MeV.