Preparation and Characterisation of ‘Green’ Photocathodes for the Generation of High-Brightness Electron Beams

Student: Saransh Malhotra
Supervisors: Carsten P Welsch (UoL)
Institution: University of Liverpool

The quality of the electron beam in an accelerator is limited largely by that of the electron source. Fourth generation light sources such as the planned UK X-FEL and ultrafast electron diffraction projects require high-brightness electron sources.

The highest levels of electron beam quality are obtained using a photoemission based electron source or photoinjector, which is a photocathode electron source emitting into an accelerating electric field. Alkali metal and thin film photocathodes are ideal candidates for these applications as they demonstrate high levels of quantum efficiency (QE) and good operational lifetime, thus permitting long uninterrupted periods of user exploitation. The high levels of QE gives additional headroom in respect of illumination laser power to facilitate transverse and longitudinal laser pulse shaping, and thus maximise the electron beam brightness and quality.

This project will focus on development of techniques to manufacture high-performance thin-film photocathode electron sources for particle accelerators, modifying and expanding the deposition equipment and processes as necessary. The use of surfaces modified by techniques such as ion implantation will also be investigates. The goal is to identify the optimum materials and preparation techniques to achieve the highest levels of electron beam brightness, with the lowest intrinsic emittance and the longest operational lifetime.

The project will also continue the development and exploitation of the TESS Transverse Energy Spread Spectrometer for the characterisation of novel photocathode electron source materials.