• G. D'Auria, P. Craievich, M. Ferianis, M.M. Milloch
  ELETTRA, Basovizza, Trieste
• dc. Cheever, T. Zwart
  MIT, Middleton, Massachusetts
• L.R. Doolittle, A. Ratti
  LBNL, Berkeley, California

The VUV soft x-ray FEL user facility, FERMI@Elettra, will use the existing 1.2 GeV linac to produce, in two separate phases, 100-40 nm and 40-10 nm, intense photon beams with single stage and double stage harmonic generation schemes respectively. To fulfill the stringent requirements of the project the present RF systems will be completely revised and upgraded. The work presented here describes the present performances of the system and plans for the linac upgrades to meet the required system specifications for FEL operation.

• W.H. Hwang, J. Choi, Y.J. Han, J.Y. Huang, H.-G. Kim, W.W. Lee
  PAL, Pohang, Kyungbuk

Funding: Work supported by MOST and POSCO.

In PALXFEL [1], the specification of the beam energy spread and rf phase is tighter than PLS Linac. We examined the rf performance in the present PLS 2.5GeV Linac. The beam energy is changed by cooling temperature, air condition, and modulator high voltage jitter. The main factor to change the beam energy is the rf phase drift by environmental conditions. We measured rf phase drift according to the variation of environmental condition and cooling temperature. We reduced the beam energy drift and the rf phase drift in long-term by improvement of cooling and air conditioning control system. Also, rf phase compensation system is needed for stable beam quality. This paper describes the microwave system for the PALXFEL the rf phase measurement and phase compensation system.

[1] Pohang Accelerator Laboratory, POSTECH Pohang 790-784, Korea

• J.-S. Oh, S. D. Jang, I.S. Ko, S. J. Kwon, W. Namkung, Y. G. Son, J.-H. Suh
  PAL, Pohang, Kyungbuk

Funding: Supported by the POSCO and the MOST, Korea

The PAL (Pohang Accelerator Laboratory) is persuading to construct a SASE-XFEL facility (PAL XFEL) that supplies coherent X-rays. The bright and stable electron beam is essential for the PAL XEL. The electron beams has to have an emittance of 1.2 mm-mrad, a peak current of 3.5 kA, and a low energy spread of 0.5 MeV. In order to provide reasonably stable SASE output, the RF stability of 0.02% rms is required for both RF phase and amplitude. This is a technologically challenging issue for PAL XFEL. An inverter technology is to be applied to charge the PFN of a new modulator. Therefore, a new inverter system should provide very stable charging performances. This paper presents the development of an ultra stable klystron-modulator with an inverter power supply.

• C. Pellegrini, J.B. Rosenzweig, G. Travish
  UCLA, Los Angeles, California
• V.A. Dolgashev, C.D. Nantista, S.G. Tantawi
  SLAC, Menlo Park, California

Funding: US Department of Energy

We describe a proposed high-gain FEL using an X-band microwave undulator and operating at a wavelength of about 0.5 μm. The FEL electron beam energy is 65 MeV. The beam is produced by the NLCTA X-band linac at SLAC, using an S-band high-brightness photoinjector. The undulator consists of a circular waveguide with an rf wave counter-propagating with respect to the electron beam. The undulator is powered with two high-power X-band klystrons and a dual-moded pulse compressor recently developed at SLAC. This system is capable of delivering flat-top rf pulses of up to 400 ns and a few hundred megawatts. The equivalent undulator period is 1.4 cm, the radius of the circular pipe is 1 cm, and the undulator parameter is about 0.4 for a helical undulator configuration, obtained using two cross-polarized TE modes, or larger for a planar configuration, using one rf polarization. The undulator is about four meters long. The FEL will reach saturation within this distance when operated in a SASE mode. We describe the FEL performance parameters, the undulator characteristics and tolerances. One main goal of the experiment is to demonstrate the feasibility of an rf undulator for high gain FELs.

• H. Ogawa, N. Sei, K.W. Watanabe, K. Y. Yamada, M.Y. Yasumoto
  AIST, Tsukuba, Ibaraki

Funding: This study was financially supported by the Budget for Nuclear Research of the Ministry of Education, Culture, Sports, Science and Technology, based on the screening and counseling by the Atomic Energy Commission, Japan.

At AIST, we have been making an effort to obtain FELs with an ultra-wide wavelength range from the vacuum ultraviolet (VUV) to the infrared (IR) on a compact storage ring NIJI-IV. Recently, performance of the NIJI-IV FEL was improved at the deep UV (DUV) around 200 nm and it became possible to make real-time observation of chemical reactions on the transition metal surfaces using the photoelectron emission microscopy (PEEM) combined with the DUV FELs. To observe dynamic behavior of the chemical reactions in detail, the FEL-PEEM system is being improved by optimizing experimental conditions. The performance of the system and the experimental results will be presented.

• 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.