What is it about?

Work to develop the optimum photocathode electron sources for particle accelerators is focussed on achieving high levels of cathode efficiency and operational robustness, and the lowest energy spreads which minimises the source (intrinsic) emittance. Naturally, experimental tools to measure this energy spread are essential to identify the best photocathode solution. The Transverse Energy Spread Spectrometer (TESS) is a robust and simple solution to this potentially difficult measurement. This paper gives a detailed summary of the TESS instrument following a series of significant upgrades which have increased its sensitivity and expanded its operational capabilities.

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Why is it important?

The minimisation of photocathode source emittance is crucial to maximise the performance of electron accelerators, and so achieve the highest possible levels of beam brightness. This in turn maximises the brightness of X-rays generated by the electron beam, and this is particularly attractive if the beam is used to drive an X-ray Free-Electron Laser (FEL). There is an additional benefit in that reducing the source emittance has the potential to reduce the overall size of the accelerator, and thus reduce its construction and operational costs.


TESS has developed into a simple and stable tool for the characterisation of photocathode performance, and is providing invaluable insights in our photocathode R&D programme in support of high-brightness electron beams and accelerator-driven light sources, particularly FELs.

Lee Jones
STFC Daresbury Laboratory

Read the Original

This page is a summary of: The measurement of photocathode transverse energy distribution curves (TEDCs) using the transverse energy spread spectrometer (TESS) experimental system, Review of Scientific Instruments, November 2022, American Institute of Physics,
DOI: 10.1063/5.0109053.
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