• G.M. wang, J.-E. Chen, Y.T. Ding, J. Hao, S.L. Huang, L. Lin, X.Y. Lu, S.W. Quan, L.F. Wang, R. Xiang, B.C. Zhang, K. Zhao, F. Jiao, D. Xie, L. Yang, F. Zhu, C. Liu, F. Wang, W. Xu, Z. Liu
  PKU/IHIP, Beijing
• Y.G. Wang
  Peking University, School of Physics, Beijing

Funding: NSFC, MOST of China

Beam loading experiments on DC-SC photoinjector test facility have been finished at 4.4 K. Upon the present experiments, the gradient of 6 MV/m is achieved. The maximum energy gain is 1.1 MeV at 4.4 K. With average beam current of 270 mA, the measured rms emittance is about 5 mm-mrad at the beam energy of 500 keV. Experiments on the test facility has validated that the DC-SC photoinjector is a good choice to provide moderate average current electron beams with low bunch charge and very high repetition rate.

• S. Zhang, D. Hardy, G. Neil, M.D. Shinn
  Jefferson Lab, Newport News, Virginia

Funding: This work supported by the Office of Naval Research, the Joint Technology Office, the Commonwealth of Virginia, the Air Force Research Laboratory, and by DOE Contract DE-AC05-84ER40150.

We report the characterization and performance of a diode-pumped, high-power, picosecond laser system designed for high-current photo-cathode accelerator injector at repetition rates of both 75MHz and 750MHz. Our characterization includes measurement of the system's amplitude stability, beam quality, pulsewidth, and phase noise for both frequencies.

• T.  Kamps, V. Duerr, K. Goldammer, D. Kraemer, P. Kuske, J. Kuszynski, D. Lipka, F. Marhauser, T. Quast, R. Richter
  BESSY GmbH, Berlin
• P. Evtushenko
  Jefferson Lab, Newport News, Virginia
• U. Lehnert, P. Michel, J. Teichert
  FZR, Dresden
• I. Will
  MBI, Berlin

Funding: Funded by the Bundesministerium für Bildung und Forschung, the State of Berlin and the Zukunftsfonds Berlin

A superconducting rf photo electron injector (SRF gun) is currently under construction by a collaboration between BESSY, DESY, FZR and MBI. The project aims at the design and setup of an CW SRF gun including a diagnostics beamline for the ELBE FEL and to address R&D issues on low emittance injectors for future light sources such as the BESSY FEL. Of critical importance for the injector performance is the control of the electron beam parameters. For this reason a compact diagnostics beamline is under development serving a multitude of operation settings ranging from low-charge (77pC), low-emittance (1 pi mm mrad) mode to high-charge (2.5nC) operation of the gun. For these operation modes beam dynamics simulations are resulting in boundary conditions for the beam instrumentation. Proven and mature technology is projected wherever possible, for example for current and beam position monitoring. The layout of the beam profile and emittance measurement systems is described. For the bunch length, which varies between 5 and 50 ps, two schemes using Electro-optical sampling and Cherenkov radiation are detailed. The beam energy and energy spread is measured with an especially designed 180 degree spectrometer.

• S. Schreiber
  DESY, Hamburg

The VUV-FEL is a free electron laser user facility being commissioned at DESY in Hamburg. In the current configuration, the linac accelerates an electron beam up to 800 MeV. The injector is a crucial part of the linac, since it has to generate and maintain a high brightness electron beam required for SASE operation. The injector includes a laser driven RF gun, a booster section, a bunch compressor, and diagnostic sections. The good performance of the injector was crucial for the first lasing of the VUV-FEL at a wavelength of 32 nm in January 2005. We report on the present layout of the injector, the properties of the electron beam and on upgrade plans scheduled in the near future.

• V. Miltchev
  DESY Zeuthen, Zeuthen

Funding: This work has partly been supported by the European Community, contract numbers RII3-CT-2004-506008 and 011935, and by the 'Impuls- und Vernetzungsfonds' of the Helmholtz Assciation, contract number VH-FZ-005

The high electron beam quality needed for SASE FEL processes requires considerable effort in characterisation and improvement of the electron source. The Photo Injector Test Facility at Zeuthen (PITZ) was built to study the production of minimum transverse emittance electron beams for Free Electron Lasers. In this work we present a study on the detailed reconstruction of the transverse phase space density distribution of electron beams at various operating conditions at PITZ. Transverse emittance values containing only a certain fraction of all particles in the distribution (core emittance) will be estimated for different operating conditions and the results will be compared with simulations.

• L. Catani, E. Chiadroni, A. Cianchi
  INFN-Roma II, Roma
• M. Castellano, G. Di Pirro, D. Filippetto, C. Vicario
  INFN/LNF, Frascati (Roma)
• M.V. Hartrott
  BESSY GmbH, Berlin
• M. Krasilnikov, A. Oppelt, F. Stephan
  DESY Zeuthen, Zeuthen

For the SPARC Project a novel diagnostic device, called "Emittance-meter", has been conceived and constructed to perform a detailed study of the emittance compensation process in the SPARC photo-injector and to optimize the RF-gun and the accelerator working point. It consists of a movable emittance measurement system, based on the 1D pepper-pot method, installed between two long bellows with the possibility to scan a region 1.5 m long downstream the RF-gun. The construction of the device was completed in the first part of this year and a series of laboratory tests, to evaluate its performances, were carried out in Spring 2005. At the beginning of the summer the complete system was moved to DESY at Zeuthen to be installed on the Photo Injector Test Facility PITZ. After the commissioning it will used for measurements of the PITZ electron beam in the framework of a collaboration between the SPARC and PITZ Projects aiming on studies and operations with photo injectors.

• C.J. Bocchetta, D. Bulfone, P. Craievich, G. D'Auria, M.B. Danailov, G. De Ninno, S. Di Mitri, B. Diviacco, M. Ferianis, A. Gomezel, F. Iazzourene, E. Karantzoulis, G. Penco, M. Trovo
  ELETTRA, Basovizza, Trieste
• J.N. Corlett, W.M. Fawley, S.M. Lidia, G. Penn, A. Ratti, J.W.  Staples, R.B. Wilcox, A. Zholents
  LBNL, Berkeley, California
• M. Cornacchia, P. Emma, Z. Huang, J. Wu
  SLAC, Menlo Park, California
• W. Graves, F.O. Ilday, F.X. Kaertner, D. Wang, T. Zwart
  MIT, Middleton, Massachusetts
• F. Parmigiani
  Universita Cattolica-Brescia, Brescia

We describe the machine layout and major performance parameters for the FERMI FEL project funded for construction at Sincrotrone Trieste, Italy. The project will be the first user facility based on seeded harmonic cascade FELs, providing controlled, high peak-power pulses. With a high-brightness rf photocathode gun, and using the existing 1.2 GeV S-band linac, the facility will provide tunable output over a range from ~100 nm to ~10 nm, with pulse duration from 40 fs to ~ 1ps, and with fully variable output polarization. Initially, two FEL cascades are planned; a single-stage harmonic generation to operate > 40 nm, and a two-stage cascade operating from ~40 nm to ~10 nm or shorter wavelength. The output is spatially and temporally coherent, with peak power in the GW range. Lasers provide modulation to the electron beam, as well as driving the photocathode and other systems, and the facility will integrate laser systems with the accelerator infrastructure, including a state-of-the-art optical timing system providing synchronization of rf signals, lasers, and x-ray pulses. Major systems and overall facility layout are described, and key performance parameters summarized.