Tenure Progress Talk: High Brightness Electron Sources for SwissFEL

by Dr Thomas Geoffrey Lucas (PSI - Paul Scherrer Institut)

Tuesday 10 Jun 2025, 17:00 → 18:00 Europe/Zurich

WBGB/019

Future upgrades to SwissFEL demand significant increases in electron bunch brightness to realise higher x-ray brilliance. According to Liouville’s Theorem, this brightness is fundamentally constrained by the initial beam quality at the photocathode. In this talk, within the framework of the EU project iFAST, I will present the development and high-power testing, conducted at PSI (in WLHA), of a novel traveling-wave RF photogun demonstrating cathode gradients exceeding 160 MV/m. This technology could enable a threefold improvement in 5D brightness compared to the existing SwissFEL electron source.

In addition to increasing source brightness, we investigate the impact of intrabeam scattering (IBS) on these electron sources, which has emerged as a critical factor limiting FEL performance. Using a newly developed simulation framework, we quantify the influence of IBS in both the current SwissFEL gun and the new traveling-wave photogun. Our results show that IBS imposes a fundamental constraint on achievable sliced energy spread which will greatly impact bunch compression downstream. These results highlight the importance of increasing the peak current at the source to mitigate downstream compression.