• O. Grimm, J. Feldhaus, J. Rossbach, E. Saldin, E. Schneidmiller, M.V. Yurkov
  DESY, Hamburg

Funding: University of Hamburg

A special electromagnetic wiggler generating infrared radiation in the range 1-200 microns is planned to be installed at the DESY VUV-FEL in Hamburg by autumn 2006. The device is located after the FEL undulators, using the spent electron beam. The purpose is two-fold: first, it will serve longitudinal electron beam diagnostics, similar to other methods currently investigated using the coherent emission of radiation at wavelengths similar to the bunch length, and second it will be used as a powerful (100 MW peak) source for short (few ps) infrared radiation pulses. The natural, perfect synchronization with the VUV pulses will allow for pump-probe experiments with high timing precision. This paper will give an overview of the project, including the infrared beam transport line.

• H. Delsim-Hashemi, O. Grimm, J. Rossbach, H. Schlarb, B. Schmidt, P. Schmuser
  DESY, Hamburg
• A.F.G. van der Meer
  FOM Rijnhuizen, Nieuwegein

Funding: DESY

FEL facilities are pushing to achieve higher peak currents mainly by means of compressing bunches longitudinally. This process defines a machine parameter that has to be fine-tuned empirically. Among the operational types of diagnostic tools for longitudinal phase-space are those based on IR spectroscopy. The most commonly used IR spectrometers at the FEL facilities are operating in the scanning mode and are not fast enough to be applicable for monitoring bunch compression. On the other hand, any non-scanning spectrometer may suffer from the low intensity that is available from coherent IR radiation in short time intervals in different wavelengths. The proposed "Single Shot Spectrometer" is based on using gratings as dispersive elements. Pioneering tests with a transmission grating have shown the feasibility of the concept. In a second step, a version with "Reflective Blazed Grating" will be tested and should allow getting the maximum available signal for the whole spectrum and improved resolution. Parallel to the study of optical parts, an array of pyroelectric detectors with integrated multi-channel readout is under development.

• M. Huening, A. Bolzmann, H. Schlarb
  DESY, Hamburg
• J.C. Frisch, D.J. McCormick, M.C. Ross, T.J. Smith
  SLAC, Menlo Park, California
• J. Rossbach
  Uni HH, Hamburg

The design of the VUV-FEL at DESY demands bunch lengths in the order of 50 fs and below.For the diagnostic of such very short bunches a transverse deflecting RF structure (LOLA) has been installed which streaks the beam according to the longitudinal distribution. Tests in the VUV-FEL yielded a rich substructure of the bunches. The most pronounced peak in the has a rms length of approximately 50 fs during FEL operation and below 20 fs FWHM at maximum compression. Depending on the transverse focusing a resolution between 10^-50 fs was achieved.

• J.R. Roensch, J. Rossbach
  Uni HH, Hamburg
• K. Abrahamyan, G. Asova, J.W. Baehr, G. Dimitrov, H.-J. Grabosch, J.H. Han, S. Khodyachykh, M. Krasilnikov, S. Liu, V. Miltchev, A. Oppelt, B. Petrosyan, S. Riemann, L. Staykov, F. Stephan
  DESY Zeuthen, Zeuthen
• M.V. Hartrott, D. Lipka
  BESSY GmbH, Berlin

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 Association, contract number VH-FZ-005.

The main goal of the Photo Injector Test facility at DESY Zeuthen (PITZ) is to test and to optimize photo injectors for Free-Electron Lasers (FELs). The demands on such a photo injector are small transverse emittances, short bunches and a high bunch charge. A FEL is driven by an accelerator which consists of a rf gun followed by an acceleration section and a magnetic bunch compressor. For the effective bunch compression detailed studies of the longitudinal phase space have to be performed. The correlation between the positions of the particles in the bunch and their longitudinal momenta has to be understood and the non-linearities of the longitudinal phase space have to be analysed. A special apparatus for longitudinal phase space tomography at 5 MeV using a dipole, a Cherenkov radiator, an optical transmission line and a streak camera was developed. Results of longitudinal phase space measurements are presented and compared with simulations.

• A. Oppelt, K. Abrahamyan, G. Asova, J.W. Baehr, G. Dimitrov, U. Gensch, H.-J. Grabosch, J.H. Han, S. Khodyachykh, G. Klemz, M. Krasilnikov, S. Liu, V. Miltchev, B. Petrosyan, S. Riemann, L. Staykov, F. Stephan
  DESY Zeuthen, Zeuthen
• W. Ackermann, W.F.O. Muller, S. Schnepp, T. Weiland
  TEMF, Darmstadt
• D. Alesini, M. Boscolo, G. Di Pirro, M. Ferrario, D. Filippetto, L. Palumbo, C. Vicario
  INFN/LNF, Frascati (Roma)
• V. Boccone
  Humboldt Universität zu Berlin, Berlin
• L. Catani, E. Chiadroni, A. Cianchi
  INFN-Roma II, Roma
• K. Floettmann, S. Schreiber
  DESY, Hamburg
• T. Garvey
  LAL, Orsay
• M.V. Hartrott, E. Jaeschke, D. Kraemer, D. Lipka, F. Marhauser, R. Richter
  BESSY GmbH, Berlin
• P. Michelato, L. Monaco, C. Pagani, D. Sertore
  INFN/LASA, Segrate (MI)
• V.V. Paramonov
  RAS/INR, Moscow
• N. Pavel
  Humboldt University Berlin, Institut für Physik, Berlin
• J.R. Roensch, J. Rossbach
  Uni HH, Hamburg
• W. Sandner, I. Will
  MBI, Berlin
• I. Tsakov
  INRNE, Sofia

Funding: This work has been partly supported by the European Community, contract numbers RII3-CT-2004-506008 and 011935, and by the 'Impuls- und Vernetzungsfonds" of the Helmholtz Association, contract number VH-FZ-05.

Since December 2004, the photo injector test facility at DESY in Zeuthen (PITZ) has been upgraded. A normal conducting copper booster cavity has been installed and the diagnostics beamline has been strongly modified. An extended water cooling system has been installed and was successfully taken into operation. Actually, the new diagnostics elements are being commissioned. After the installation of the new 10 MW klystron in June/July, the gun can be conditioned towards higher average power, and the whole beamline including the booster will be taken into operation. First results from the commissioning phase including gun and booster conditioning are reported.