• W. Singer, S. Aderhold, J. Iversen, G. Kreps, L. Lilje, A. Matheisen, X. Singer, H. Weise
  DESY, Hamburg
• M. Pekeler, J.Sch. Schwellenbach
  ACCEL, Bergisch Gladbach
• F. Schoelz, B. Spaniol, E. Stiedl
  W.C. Heraeus GmbH, Materials Technology Dept., Hanau

A test program of 1.3 GHz TESLA shape 9-cell large grain (LG) resonators for the European XFEL project was started at DESY. The main aim is to find out whether or not the choice of LG material could be an option for the fabrication of approx. 800 XFEL resonators. Several aspects are under investigation and will be compared with the conventional polycrystalline material option. One of the aspects is the material issue: could the required amount of LG niobium be produced at industry in a cost effective and reliable manner? The second issue is the fabrication of cavities: could the series production of resonators be done on the level of required accuracy and costs? The third one is the performance issue: what is the appropriate treatment for reproducibly achieving the specified XFEL accelerating gradients? Development of the LG disc production was done within the framework of the R&D program of DESY and W. C. HERAEUS. Eleven resonators are produced at the company ACCEL. Up to now three resonators are RF-tested vertically. The He-vessel was welded onto one of the resonators which passed the horizontal RF-test. The data and perspectives of the LG cavity application are discussed.

• A. Bosotti, R. Paparella
  INFN/LASA, Segrate (MI)
• C. Albrecht, L. Lilje
  DESY, Hamburg

Cavity tuners are needed to precisely tune the resonant frequency of TESLA SC cavities for European XFEL linac. Although several units of the currently used device, originally designed at Saclay for TTF and then developed at DESY, have been manufactured and tested so far, a permanent installation like the XFEL poses higher requirements in terms of reliability and reproducibility. XFEL indeed requires about {10}00 tuners to be produced in a relatively short time and then to simultaneously work in cryogenic environment, each of them being equipped with a stepper motor driving unit and two piezoelectric actuators. In this frame, an acceptance test procedure, here presented, has been studied, its main goal being the cross-check of issues affecting reliability: installation, mechanical coupling of active elements to cavity, motor and fast actuators functionality. An electronic equipment has been developed for driving signals, sensors and data management, specifically aiming toward an automatic and user-friendly routine in view of a large scale application. The procedure has been then applied for calibration purposes of a sample cavity assembly, the experimental results are also presented.

• N. Ohuchi, H. Hayano, N. Higashi, H. Nakai, K. Tsuchiya, A. Yamamoto
  KEK, Ibaraki
• T.T. Arkan, H. Carter, M.S. Champion, J. Grimm, J.S. Kerby, D.V. Mitchell, T.J. Peterson, M.C. Ross
  Fermilab, Batavia
• S. Barbanotti, C. Pagani, P. Pierini
  INFN/LASA, Segrate (MI)
• L. Lilje
  DESY, Hamburg

In an attempt at demonstrating an average field gradient of 31.5 MV/m as per the design accelerating gradient for ILC, a program called S1-Global is in progress as an international research collaboration among KEK, INFN, FNAL, DESY and SLAC. The S1-Global cryomodule will contain eight superconducting cavities from FNAL, DESY and KEK. The cryomodule will be constructed by joining two half-size cryomodules, each 6 m in length. The module containing four cavities from FNAL and DESY will be constructed by INFN. The design of this module is based on an improved 3rd generation TTF design. KEK will modify the 6-meter STF cryomodule to contain four KEK cavities. The designs of the cryomodules are ongoing between these laboratories, and the operation of the system is scheduled at the KEK-STF from June 2010. In this paper, the S1-Global cryomodule plan and the module design will be presented. ‘S1-Global collaboration’ as a co-author.