IPAC'26 - the 17th International Particle Accelerator Conference

Upgrade of the High Repetition Rate FEL FLASH to allow simultaneous SASE and External Seeding Operation

THP2073

21 May 2026, 16:00

2h

C.I.D

Poster Presentation MC2.A06: Free Electron Lasers (FELs) Poster session

Speaker

Katja Honkavaara (Deutsches Elektronen-Synchrotron DESY)

Description

The Free-Electron Laser FLASH at DESY has provided more than 20 years XUV and soft x-ray SASE radiation for user experiments. In order to keep FLASH as a state-of-the-art FEL, the refurbishment and upgrade project FLASH2020+ was launched. The latest upgrade has been a complete replacement of the FLASH1 beamline in a 14 months shutdown in 2024/25. The new external seeded FLASH1 will provide fully coherent radiation at up to MHz bunch repetition rate (burst). Moreover, the new APPLE-III type undulators enable full polarization control. In addition, FLASH1 hosts, as before, a THz source. FLASH2 continues unchanged in SASE operation. The commissioning of the upgraded facility started in August 2025, and since November FLASH2 is back in user operation. Commissioning of seeding at FLASH1 continues in parallel to FLASH2 user experiments.