At the European XFEL, an ultrashort-pulse UV laser is used to release electrons from a cesium telluride photocathode. These electron beams are tightly focused and accelerated for use in Free-Electron Lasers (FELs). Eureca sensors with removed protective windows are employed to monitor the laser position and profile with high precision.

Because standard sensor windows strongly absorb UV radiation, specially modified cameras with removed front glass are essential. These sensors enable high-resolution beam profile imaging in the deep UV range, a critical requirement for photocathode-based injector operation.

NEPAL – The New Photocathode Laser System

The NEPAL system ("Next Generation Photocathode Laser") delivers flexible pulse shaping and adjustable durations. It supports various operational modes of the FEL and enables tailored laser delivery, from intense single pulses to modulated profiles for advanced beam manipulation.

You can find closer information in this paper: 

https://bib-pubdb1.desy.de/record/607066/files/MOPG47.pdf?version=1

Research Group FS-LA

The FS-LA group ("Laser Operations and User Support") specializes in laser systems for particle accelerators. Their work includes the operation of the laser infrastructure at European XFEL and FLASH, photocathode R&D, advanced pulse shaping techniques, and integration into the high-precision timing systems of the accelerator complex.