Author: Horan, D.
Paper Title Page
THPB088 20 kW CW Power Couplers for the APS-U Harmonic Cavity 1346
 
  • M.P. Kelly, A. Barcikowski, Z.A. Conway, D. Horan, M. Kedzie, S.H. Kim, P.N. Ostroumov
    ANL, Argonne, Illinois, USA
  • S.V. Kutsaev
    RadiaBeam, Santa Monica, California, USA
  • J. Rathke
    AES, Medford, New York, USA
 
  Funding: This work supported by the U.S. DOE, Office of Nuclear Physics, Contract No. DE-AC02-06CH11357. This research used resources of ANL’s ATLAS facility, which is a DOE Office of Science User Facility.
A pair of 20 kW CW adjustable RF power couplers optimized for 1.4 GHz have been designed and are being built as part of the APS-U bunch lengthening system. The system uses one superconducting RF cavity to be installed into the APS Upgrade electron storage ring and will provide a tremendous practical benefit to the majority of users by increasing the beam lifetime by 2-3 times. The 80 mm diameter, 50 Ω coaxial couplers include 4 cm (~20 dB) of adjustability. This allows optimization of bunch lengthening for a range of storage ring beam currents and fill patterns while, simultaneously, maintaining the required 0.84 MV harmonic cavity voltage. To provide bunch lengthening, the cavity/coupler system must extract RF power (up to 32 kW) from the beam. Each coupler will transmit roughly half of the total extracted power to external water-cooled loads. The design extends upon on a well-tested ANL two RF window concept, using a pair of simple rugged 80 mm diameter alumina disks. A new feature is the ‘hourglass-shaped’ inner conductor chosen to maximize transmission at 1.4 GHz. Results of electromagnetic and thermal simulations, as well as, prototyping and initial RF testing are presented.
 
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