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

Reference number: PPPR046


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.

In the first year of the project, you will be familiarised with the existing surface analysis and photocathode growth equipment, and the TESS used to characterise photocathode electron sources, and contribute to the commissioning of the new alkali metal photocathode growth facility. In subsequent years, you will focus on the growth and characterisation of photocathode sources with different compositions, seeking an optimum deposition solution, identifying new/improved electron sources, and publishing results wherever possible.

The work will take place predominantly at Daresbury Laboratory, mostly involving laboratory-based studies of photoemissive materials in our state-of-the-art VISTA laboratory. There will also be the opportunity to use other research facilities within the lab to further characterise these materials to investigate ultimate beam brightness achievable. The project gives excellent opportunities for high quality publications and for presenting results at national and international research workshops and conferences.

Throughout the project you will have access to the Cockcroft Institute’s comprehensive postgraduate training in accelerator science, as well as to targeted training in data science provided by the University of Liverpool with the Centre for Doctoral Training LIV.INNO. A 6-months industry placement will be part of your project and help broaden your research and career skills.

You will be working within the Accelerator Science and Technology Centre (ASTeC) and be part of the pan-European QUASAR Group. The studentship will be paid for up to 48 months at the standard RCUK level.