PSI, Villigen
The X-ray FEL facility SwissFEL, currently planned at the Paul Scherrer Institut, is primarily based on the SASE operation of a hard (1-7 Å) and soft (7-70 Å) X-ray beamline. However the soft X-ray FEL beamline is foreseen to allow for seeding down to 1 nm. The intrinsic shot noise in the electron bunch demands excellent state-of-the-art seeding sources and strategies. This presentation discusses various seeding options for the PSI-XFEL and evaluates them regarding performance and risk of implementation.
PSI, Villigen
The Paul Scherrer Institute is currently proposing a X-ray Free-electron Laser facility operating in the wavelength range of 0.1 to 7 nm. The overall design aims for a compact layout and relies on a low emittance electron beam and short period undulator. As an initial step, a 250 MeV is currently under construction to demonstrate a high brightness electron beam sufficient for operating the SwissFEL. An extension of the 250 MeV injector is under construction to test additional key components for the SwissFEL. Those are prototypes of the in-vacuum undulator modules as well as the proof-of-principle demonstration of echo-enabled harmonic generation as a possible seeding option for the SwissFEL at 1 nm. The combination of seeding and prototype undulator module allows for saturation of the FEL at 50 nm and first experiments with FEL radiation at the PSI.
PSI, Villigen
The Paul Scherrer Institut is proposing an X-ray FEL facility, providing a wavelength range between 1 Angstrom to 7 nm. The major mode of operation is SASE with a supplemental seeding option for wavelength down to 1 nm. In addition a low charge operation of about 10 pC is considered to achieve single spike operation in the soft X-ray regime and thus overcoming the limitation of seeding sources at that wavelength. This presentation discusses the basic operation as well expected stability of the performance in energy and spectral power.
PSI, Villigen
Recently, several groups suggested a new FEL operation mode with low single bunch charge to generate sub-fs long longitudinal coherent XFEL photon pulses, so called single spike lasing mode. At PSI, we studied this mode to generate single spike XFEL photon beams at 1 nm and 0.1 nm. We report several critical issues which we found with such an operation mode, namely, ultra-tight RF jitter tolerances, alignment tolerances, and challenging beam diagnostic specifications for the stable single spike lasing mode.
PSI, Villigen
In the frame of the SwissFEL project, an electron gun based on diode acceleration followed by a two cell RF cavity is under test at PSI. The diode consists of a photocathode / anode assembly and is driven with a voltage pulse of 500 kV maximum in 200 ns FWHM . The metal photocathode is illuminated by a Nd:YLF laser operating at 262 nm wavelength with a pulselength of 10 to 35 ps (FWHM) producing electron bunches of up to 200 pC. The distance from cathode to anode can be varied from 0 to 30 millimeters with a typical cathode field of 50 MV/m during the commissioning phase. Electrons leave the diode through an anode aperture and enter a two cells RF Cavity (1.5 GHz), which accelerates the beam to a maximum energy of 5 MeV. Beam characteristic measurements are presented and compared with simulations.