High brightness, symmetric electron bunch generation in a plasma wakefield accelerator via a radially-polarized plasma photocathode

TL;DR

This paper proposes a novel radially-polarized plasma photocathode scheme that produces high-brightness, symmetric electron bunches, with comprehensive modeling and optimization demonstrating its advantages over linear polarization.

Contribution

The study introduces a radially-polarized laser scheme for plasma photocathodes, enhancing electron bunch brightness and symmetry, supported by detailed modeling and optimization.

Findings

Radially-polarized laser pulses yield higher brightness electron bunches.

Optimized scheme achieves symmetric transverse emittance.

Comparison shows superiority over linearly-polarized pulses.

Abstract

The plasma photocathode has previously been proposed as a source of ultra-high-brightness electron bunches within plasma accelerators. Here, the scheme is extended by using a radially-polarized ionizing laser pulse to generate high-charge, high-brightness electron bunches with symmetric transverse emittance. Efficient start-to-end modelling of the scheme, from ionization and trapping until drive bunch depletion, enables a multi-objective Bayesian optimisation routine to be performed to understand the performance of the radially-polarized plasma photocathode, quantify the stability of the scheme, and explore the fundamental relation between the witness bunch charge and its emittance. Comparison of plasma photocathodes driven by radially- and linearly-polarized laser pulses show that the former yields higher brightness electron bunches when operating in the optimally-loaded regime.