• O. Kugeler, W. Anders, A. Frahm, S. Klauke, J. Knobloch, A. Neumann, D. Pflückhahn, S. Rotterdam, M. Schuster, S. Voronenko
  Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin

For CW applications of superconducting cavities, obtaining a high quality factor is an important issue, since the required cryogenic power drops inversely proportional to Q0. Q0 is limited by BCS-losses and static losses, i.e. impurities and trapped magnetic flux. With sufficient magnetic shielding for TESLA type cavities, typical values of 2*10¹⁰ are being achieved at 1.8K operating temperature. The flux trapping was monitored by cooling the cavity at different ambient magnetic fields. In another experiment we have observed a significant increase in the Q0 value of up to 50% when subjecting the cavity to an additional cryogenic cooling cycle. Quantitative results are being presented and possible explanations for the effects are being discussed.

Poster

• T. Kamps, W. Anders, A. Frahm, J. Knobloch, O. Kugeler, A. Neumann, T. Quast, M. Schenk, M. Schuster
  Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin
• M. Dirsat
  Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
• P. Kneisel
  JLAB, Newport News, Virginia
• R. Nietubyc
  The Andrzej Soltan Institute for Nuclear Studies, Centre Swierk, Swierk/Otwock
• T. Rao, J. Smedley
  BNL, Upton, Long Island, New York
• J.K. Sekutowicz
  DESY, Hamburg
• J. Teichert
  FZD, Dresden
• I. Will
  MBI, Berlin

In this paper we describe the R&D roadmap at HZB for the development of a high-brightness, high average current SRF electron gun for an energy-recovery linac based synchrotron radiation source.

• O. Kugeler, W. Anders, A. Frahm, S. Klauke, J. Knobloch, A. Neumann, M. Rohloff, M. Schuster
  Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin

The TTF-III input coupler was designed for pulsed operation at average power levels up to 5 kW. For CW-applications, higher power levels are desirable. Previous investigations have identified the connection between 4K and 78K section as the bottleneck for maximum usable power level. We have modified this section of the coupler by including a gas cooling. This setup was tested in a coupler-test-stand at room temperature. We have achieved stable operation at power levels up to 10kW which is sufficient for the field levels that are to be reached in the BerlinPro ERL. The results can be regarded as a worst case scenario, since the heat conductivity of all involved materials is rising significantly upon cooling to operating temperatures.

Poster