A Masked Photocathode in a Photoinjector

TL;DR

This paper introduces a masked photocathode design within a photoinjector that simplifies photocathode replacement, reduces dark current, and mitigates beam emittance growth by using an electrode with a small hole as a shield.

Contribution

The paper presents a novel masked photocathode configuration that enhances ease of replacement and beam quality in photoinjectors, addressing limitations of traditional mounting methods.

Findings

Easier photocathode replacement via rotation behind the electrode

Reduction in dark current and secondary electron emission

Transverse laser beam cut-off reduces emittance growth

Abstract

In this paper, we propose a masked photocathode inside a photoinjector for generating high brightness electron beam. Instead of mounting the photocathode onto an electrode, an electrode with small hole is used as a mask to shield the photocathode from the accelerating vacuum chamber. Using such a masked photocathode will make the replacement of photocathode material easy by rotating the photocathode behind the electrode into the hole. Furthermore, this helps reduce the dark current or secondary electron emission from the photocathode material. The masked photocathode also provides transverse cut-off to a Gaussian laser beam that reduces electron beam emittance growth from nonlinear space-charge effects.