Ionization injection in a laser wakefield accelerator subject to a transverse magnetic field

TL;DR

This paper explores how an external transverse magnetic field influences ionization injection in laser wakefield accelerators, leading to improved electron beam quality and acceleration efficiency through theoretical and simulation studies.

Contribution

It demonstrates that a transverse magnetic field modifies injection dynamics, reduces energy spread, and enhances electron beam charge and energy in LWFA.

Findings

Injection occurs over a shorter distance with a magnetic field.

Beam loading is compensated, reducing energy spread.

Electron charge and peak energy are increased.

Abstract

The effect of an external transverse magnetic field on ionization injection of electrons in a laser wakefield accelerator (LWFA) is investigated by theoretical analysis and particle-in-cell simulations. On application of a few tens of Tesla magnetic field, both the electron trapping condition and the wakefield structure changes significantly such that injection occurs over a shorter distance and at an enhanced rate. Furthermore, beam loading is compensated for, as a result of the intrinsic trapezoidal-shaped longitudinal charge density profile of injected electrons. The nonlinear ionization injection and consequent compensation of beam loading lead to a reduction in the energy spread and an enhancement of both the charge and final peak energy of the electron beam from a LWFA immersed in the magnetic field.