title: Electron bunch timing with femtosecond precision in a superconducting free-electron laser.
abstract: High-gain free-electron lasers (FELs) are capable of generating femtosecond x-ray pulses with peak brilliances many orders of magnitude higher than at other existing x-ray sources. In order to fully exploit the opportunities offered by these femtosecond light pulses in time-resolved experiments, an unprecedented synchronization accuracy is required. In this Letter, we distributed the pulse train of a mode-locked fiber laser with femtosecond stability to different locations in the linear accelerator of the soft x-ray FEL FLASH. A novel electro-optic detection scheme was applied to measure the electron bunch arrival time with an as yet unrivaled precision of 6 fs (rms). With two beam-based feedback systems we succeeded in stabilizing both the arrival time and the electron bunch compression process within two magnetic chicanes, yielding a significant reduction of the FEL pulse energy jitter.
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany. florian.loehl@cornell.edu
authors.forename: F
authors.initials: F
authors.lastname: Löhl
authors.forename: V
authors.initials: V
authors.lastname: Arsov
authors.forename: M
authors.initials: M
authors.lastname: Felber
authors.forename: K
authors.initials: K
authors.lastname: Hacker
authors.forename: W
authors.initials: W
authors.lastname: Jalmuzna
authors.forename: B
authors.initials: B
authors.lastname: Lorbeer
authors.forename: F
authors.initials: F
authors.lastname: Ludwig
authors.forename: K-H
authors.initials: KH
authors.lastname: Matthiesen
authors.forename: H
authors.initials: H
authors.lastname: Schlarb
authors.forename: B
authors.initials: B
authors.lastname: Schmidt
authors.forename: P
authors.initials: P
authors.lastname: Schmüser
authors.forename: S
authors.initials: S
authors.lastname: Schulz
authors.forename: J
authors.initials: J
authors.lastname: Szewinski
authors.forename: A
authors.initials: A
authors.lastname: Winter
authors.forename: J
authors.initials: J
authors.lastname: Zemella