Optimisation of the pointing stability of laser-wakefield accelerated electron beams

TL;DR

This paper investigates the factors affecting the pointing stability of laser-wakefield accelerated electron beams, demonstrating that gas-cells improve stability and residual laser dispersion influences beam offset, with implications for optimizing laser systems.

Contribution

It provides a comprehensive experimental analysis identifying key factors affecting beam pointing stability and proposes residual laser dispersion as a diagnostic tool.

Findings

Gas-cells offer more stable electron generation than gas-jets.

Shot-to-shot pointing fluctuation is below 1 mrad.

Residual angular dispersion causes a measurable electron beam offset.

Abstract

Laser-wakefield acceleration is a promising technique for the next generation of ultra-compact, high-energy particle accelerators. However, for a meaningful use of laser-driven particle beams it is necessary that they present a high degree of pointing stability in order to be injected into transport lines and further acceleration stages. Here we show a comprehensive experimental study of the main factors limiting the pointing stability of laser-wakefield accelerated electron beams. It is shown that gas-cells provide a much more stable electron generation axis, if compared to gas-jet targets, virtually regardless of the gas density used. A sub-mrad shot-to-shot fluctuation in pointing is measured and a consistent non-zero offset of the electron axis in respect to the laser propagation axis is found to be solely related to a residual angular dispersion introduced by the laser compression system and can be used as a precise diagnostic tool for compression oprtimisation in chirped pulse amplified lasers.