FEL2026 - 42nd International Free Electron Laser Conference

Session

SASE FEL (Invited)

TUX

25 Aug 2026, 08:30

27. Reverse undulator tapering for polarization control and short pulse generation (TUX01)

Evgeny Schneidmiller (Deutsches Elektronen-Synchrotron DESY)

25/08/2026, 08:30

Session 4: SASE FEL

Invited Oral Presentation

Reverse undulator taper is a unique method allowing to strongly suppress radiation intensity at the exit of SASE undulator while maintaining microbunching at a significant level. Recently, it was used to generate high-purity circularly polarized radiation from dedicated afterburners (Apple-X at the European XFEL and Apple-III at FLASH, the latter operates at the 3rd harmonic of SASE...

110. Sub-Femtosecond X-ray Free-Electron Laser Driven by Additional Bunch Compression via Reverse-Energy Chirp at SACLA (TUX02)

Eito Iwai (Japan Synchrotron Radiation Research Institute, RIKEN SPring-8 Center)

25/08/2026, 08:50

Session 4: SASE FEL

Invited Oral Presentation

We demonstrate sub-femtosecond hard X-ray free-electron laser (XFEL) pulse generation at SACLA, achieved through a robust and flexible scheme for additional electron bunch compression. The method leverages a reverse-energy chirp, driven by wakefields within the accelerating structures and longitudinal space charge effects. By employing a tunable R56 optics in a two Double Bend Achromat (DBA)...

169. Coherent Twin-Pulse Generation at XFELs: Dual- Injector-Laser Production of Electron Bunch Pairs for SASE, HXRSS and PWFA (TUX03)

Ingmar Hartl (Deutsches Elektronen-Synchrotron DESY)

25/08/2026, 09:10

Session 4: SASE FEL

Invited Oral Presentation

The recently commissioned dual NEPAL photocathode laser systems at EuXFEL and FLASH enable the generation of twin electron bunches with unprecedented flexibility. Each laser pulse can be independently tuned in pulse energy, temporal and longitudinal profile, and relative timing, allowing for electron bunch production in the same or any two 0.77 ns spaced RF buckets. This capability unlocks...