• S. Reiche, R. Abela, B. Beutner, H.-H. Braun, B. Patterson, M. Pedrozzi
  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.

• B. Beutner
  PSI, Villigen

The planned SwissFEL facility will supply coherent, ultra-bright, and ultra-short XFEL photon beams covering a wide wavelength range from 0.1 nm to 7 nm, with nominal beam emittances in the range from 0.18 to 0.43 mm mrad. At the 250 MeV Injector test facility for the SwissFEL the beam quality will be studied to confirm the feasibility of the XFEL requirements. In order to understand and optimise the electron beam, precise measurements of the beam properties are essential. The diagnostics setup consists of various quadrupoles for phase advance scans and a 3.5-cell FODO lattice. Included in the diagnostic setup is a transverse deflecting RF structure for longitudinal resolved measurements. In this paper the techniques for emittance and Twiss parameter reconstruction are discussed. The focus is on transport matrix inversion and tomographic phase space reconstruction using the maximum entropy algorithm. The layout of the diagnostic section, the electron optics setup, and the strategy for measurements of the emittance are presented. Data on the systematic error concerning beam size measurement errors and beam energy uncertainties complete this summary.

• G.L. Orlandi, B. Beutner, R. Ischebeck, V. Schlott, B. Steffen
  PSI, Villigen

Diagnostics with a transverse spatial resolution in the order or even higher than the intrinsic limit of the traditional OTR light spot imaging techniques is required for high energy and low emittance electron beams by FEL driver linac. High resolution measurements of the beam transverse size can be performed by moving the radiation detection from the space of the electron transverse coordinates to the Fourier conjugate space of the radiation angular distribution. The development of such a new diagnostic technique is related to the experimental investigation of the beam transverse size effects in the angular distribution of the OTR spectral intensity. The status of the experimental investigation of such a phenomenon at the SwissFEL project and the main features of such a new diagnostic technique will be presented.

• A. Oppelt, R. Abela, B. Beutner, B. Patterson, S. Reiche
  PSI, Villigen

A powerful THz source is being considered for THz-pump / X-ray probe experiments at the planned SwissFEL. The source should deliver half-cycle pulses of less than 1 ps duration with an energy of 100 μJ in a focal region of 1 mm². Design considerations and simulations for such a source fulfilling the challenging parameter combination will be presented.

• R. Ganter, B. Beutner, S. Binder, H.-H. Braun, M. Broennimann, M. Dach, T. Garvey, C.H. Gough, C.P. Hauri, M. Heiniger, R. Ischebeck, S. Ivkovic, Y. Kim, E. Kirk, F. Le Pimpec, K.B. Li, R. Luescher, P. Ming, A. Oppelt, M. Paraliev, M. Pedrozzi, J.-Y. Raguin, L. Rivkin, T. Schietinger, T. Schilcher, B. Steffen, S. Tsujino, A.F. Wrulich
  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.