Comparison of DC and SRF Photoemission Guns For High Brightness High Average Current Beam Production

TL;DR

This study compares DC and superconducting RF photoemission guns for high brightness, high average current electron beams, optimizing geometry and laser parameters to minimize emittance under realistic constraints.

Contribution

It introduces a multivariate genetic optimization approach to compare and optimize both gun types considering realistic operational constraints.

Findings

SRF and DC guns have comparable emittance performance with low-emittance photocathodes.

Optimized geometries and laser parameters significantly influence beam quality.

Performance depends on photocathode thermal emittance.

Abstract

A comparison of the two most prominent electron sources of high average current high brightness electron beams, DC and superconducting RF photoemission guns, is carried out using a large-scale multivariate genetic optimizer interfaced with space charge simulation codes. The gun geometry for each case is varied concurrently with laser pulse shape and parameters of the downstream beamline elements of the photoinjector to obtain minimum emittance as a function of bunch charge. Realistic constraints are imposed on maximum field values for the two gun types. The SRF and DC gun emittances and beam envelopes are compared for various values of photocathode thermal emittance. The performance of the two systems is found to be largely comparable provided low intrinsic emittance photocathodes can be employed.