title: Two-color operation of a free-electron laser with a tilted beam.
abstract: With the successful operation of free-electron lasers (FELs) as user facilities there has been a growing demand for experiments with two photon pulses with variable photon energy and time separation. A configuration of an undulator with variable-gap control and a delaying chicane in the middle of the beamline is proposed. An injected electron beam with a transverse tilt will only yield FEL radiation for the parts which are close to the undulator axis. This allows, after re-aligning and delaying the electron beam, a different part of the bunch to be used to produce a second FEL pulse. This method offers independent control in photon energy and delay. For the parameters of the soft X-ray beamline Athos at the SwissFEL facility the photon energy tuning range is a factor of five with an adjustable delay between the two pulses from -50 to 950 fs.
authors.affiliation: Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland.
authors.forename: Sven
authors.initials: S
authors.lastname: Reiche
authors.affiliation: Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland.
authors.forename: Eduard
authors.initials: E
authors.lastname: Prat
keywords: free-electron laser; simulations; undulator beamline design