In situ high resolution real-time quantum efficiency imaging for photocathodes

TL;DR

This paper introduces a scalable in situ real-time imaging technique for quantum efficiency of photocathodes, enabling detailed surface analysis and dynamic performance monitoring at micron resolution.

Contribution

It presents a novel method combining uniform illumination and magnetic focusing to observe quantum efficiency variations in real time.

Findings

Micron-scale resolution of quantum efficiency in gallium arsenide photocathodes.

Detection of inhomogeneity and dynamic changes in quantum efficiency.

Observation of unexpected uneven decrease in quantum efficiency.

Abstract

Aspects of the preparation process and performance degradation are two major problems of photocathodes. The lack of a means for dynamic quantum efficiency measurements results in the inability to observe the inhomogeneity of the cathode surface by fine structural analysis and in real time.Here we present a simple and scalable technique for in situ real-time quantum efficiency diagnosis. An incoherent light source provides uniform illumination on the cathode surface, and solenoid magnets are used as lens for focusing and imaging the emitted electron beam on a downstream scintillator screen, which converts the quantum efficiency information into fluorescence intensity distribution. The microscopic discontinuity and the dynamic changes of the quantum efficiency of a gallium arsenide photocathode are observed at a resolution of a few microns. An unexpected uneven decrease of the quantum efficiency is also recorded. The work demonstrates a new observation method for photoemission materials research.