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Kneisel, P.

Paper Title Page
THP043 Preliminary Results from Multi-Cell Seamless Niobium Cavities Fabricated by Hydroforming 882
  • W. Singer, I. Jelezov, A. Matheisen, X. Singer
    DESY, Hamburg
  • G. Ciovati, P. Kneisel, M. Morrone
    JLAB, Newport News, Virginia

Funding: This manuscript has been partially authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The technology of forming multi-cell seamless niobium cavities has been developed at DESY within the European CARE (Coordinated Accelerator Research in Europe) program. Three cell units have been manufactured successfully and a 9-cell cavity has recently been completed from three sub-sections and will be tested in the near future. Meanwhile, we have equipped two 3-cell units – one center unit of a 9-cell cavity and one end-unit – with niobium beam pipes, have tuned these units and carried out cryogenic rf tests after standard bcp surface treatments had been applied to these cavities. In addition, we will take temperature maps with Jlab's two-cell thermometry system; since in cavities fabricated by 'standard' methods such as deep drawing of half cells and electron beam welding cavity performance limitations have often been found at or near equator welds. It will be of particular interest to compare the seamless cavity quench locations to those from standard cavities. This contribution will report about the cryogenic test results and the T-mapping findings.

THP044 Coaxial Coupling Scheme for Fundamental and Higher Order Modes in Superconducting Cavities 885
  • J.K. Sekutowicz, G. Ciovati, P. Kneisel
    JLAB, Newport News, Virginia
  • L. Xiao
    SLAC, Menlo Park, California

Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Higher Order Modes generated by a particle beam passing through a superconducting accelerating cavity have to be damped to avoid beam instabilities. A coaxial coupler located in the beam pipes of the cavities provides for better propagation of HOMs and strong damping in appropriate HOM dampers. The whole damping device can be designed as a detachable system. If appropriately dimensioned, the rf currents can be minimized at the flange position. Additionally, the coaxial system also provides efficient coupling of fundamental mode rf power into the superconducting cavity. Compared to presently available solutions for HOM damping, this scheme provides for several advantages: stronger HOM damping, flangeable solution, exchangeability of the HOM damping device on a cavity, less complexity of the superconducting cavity, possible cost advantages. This contribution will describe the results of room temperature measurement and discuss modeling, which resulted in an optimized layout of a cavity-coupler system.