Characterization of supersonic and subsonic gas targets for laser wakefield electron acceleration experiments

S Lorenz,M Nevrkla,E Chacon-Golcher,G Grittani,F Nawaz,C M Lazzarini,J Limpouch,T Levato,L Vilanova

doi:10.1063/1.5081509

Abstract

The choice of the correct density profile is crucial in laser wakefield acceleration. In this work, both subsonic and supersonic gas targets are characterized by means of fluid-dynamic simulations and experimental interferometric measurements. The gas targets are studied in different configurations, and the density profiles most suitable for laser wakefield acceleration are discussed.

Highlights

Laser wakefield acceleration (LWFA)1–4 is the most compact technique for producing ultrashort GeV-class electron beams.5–7 LWFA is based on exciting a plasma wave in an underdense plasma by the ponderomotive force of an intense laser pulse
We demonstrated, by benchmarking with experimental measurements, that our fluid-dynamic simulations can predict the density profiles of gas targets in both the supersonic and subsonic regimes
These simulations can be used for designing new gas targets and for evaluating their performance in different configurations

Summary

Introduction

Laser wakefield acceleration (LWFA) is the most compact technique for producing ultrashort (fs) GeV-class electron beams. LWFA is based on exciting a plasma wave in an underdense plasma by the ponderomotive force of an intense laser pulse (with normalized vector potential a0 $ 1). A strong electrostatic field in the plasma wave accelerates the electrons.. A longitudinal plasma density downramp can be used to improve the stability of the electron beam. This scheme is, at the same time, very efficient and easy to implement.. Superior beam quality is obtained by restricting the electron injection to the accelerating phase in the density downramp region. In the recently growing field of LWFA at reduced laser energies of few mJ (#10 mJ, needed to increase the repetition rate to $1 kHz), it is crucial to achieve a much higher plasma density for electron acceleration, while at the same time keeping the quantity of gas released in the vacuum chamber as small as possible

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