FEL2026 - 42nd International Free Electron Laser Conference

High-Repetition-Rate Tunable UV Laser System for External Seeding of FLASH

MOP29

24 Aug 2026, 16:00

2h

Poster Presentation Session 5: Seeded FEL Monday Poster Session

Speaker

Ingmar Hartl (Deutsches Elektronen-Synchrotron DESY)

Description

We present recent progress on the SLASH laser system, a high-repetition-rate tunable femtosecond UV laser developed for external seeding of the FLASH free-electron laser (FEL). The system features a dual-branch architecture: a third-harmonic generation arm (343 nm) and a tunable OPCPA-based arm (297–317 nm), enabling flexible pulse control for advanced seeding schemes like echo-enabled harmonic generation (EEHG). Two about 30 and 40 meter long UHV beam transport lines deliver synchronized UV pulses to the accelerator, with 600 µm waist radius in the two modulator structures, where overlap with the electron beam was established. These developments mark a key milestone toward externally seeded operation at FLASH.