Gallium Arsenide preparation and QE Lifetime Studies using the ALICE Photocathode Preparation Facility

TL;DR

This paper details a multi-stage preparation process for GaAs photocathodes, studying their QE stability and lifetime in a high-vacuum environment, supported by surface science analysis.

Contribution

It introduces an effective GaAs photocathode preparation method and provides comprehensive QE and lifetime stability data using advanced surface analysis techniques.

Findings

Successful multi-stage preparation improves photocathode stability.

QE and lifetime are maintained in ultra-high vacuum conditions.

Surface science techniques reveal atomic-level processes during activation.

Abstract

In recent years, Gallium Arsenide (GaAs) type photocathodes have become widely used as electron sources in modern Energy Recovery Linac based light sources such as the Accelerators and Lasers in Combined Experiments (ALICE) at Daresbury Laboratory and as polarised electron source for the proposed International Linear Collider (ILC). Once activated to a Low Electron Affinity (LEA) state and illuminated by a laser, these materials can be used as a high-brightness source of both polarised and un-polarised electrons. This paper presents an effective multi-stage preparation procedure including heat cleaning, atomic hydrogen cleaning and the activation process for a GaAs photocathode. The stability of quantum efficiency (QE) and lifetime of activated to LEA state GaAs photocathode have been studied in the ALICE load-lock photocathode preparation facility which has a base pressure in the order of 10^-11 mbar. These studies are supported by further experimental evidence from surface science techniques such as X-ray Photoelectron Spectroscopy (XPS) to demonstrate the processes at the atomic level.