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Multipactor Study in the Coupler Region of the Diamond SCRF Cavities

DOI: 10.18429/JACoW-SRF2017-TUPB010 DOI Help

Authors: S. A. Pande (Diamond Light Source) , C. Christou (Diamond Light Source) , Pengda Gu (Diamond Light Source) , G. Burt (Lancaster University)
Co-authored by industrial partner: No

Type: Conference Paper
Conference: 18th International Conference on RF Superconductivity SRF2017
Peer Reviewed: No

State: Published (Approved)
Published: January 2018

Open Access Open Access

Abstract: The Diamond storage ring operates with two CESR-B type Superconducting RF cavities. The cavities suffer from trips with a sudden loss of accelerating field if operated above a certain voltage. Consequently the cavities are operated at voltages up to 1.4 MV for better reliability. These cavities are iris coupled and have fixed Qext. At these lower operating voltages, the optimum condition for beam loading is satisfied at powers around 100 kW. For operation at 300 mA with two cavities, the power needed per system exceeds 200 kW. Therefore 3 stub tuners are used to lower the Qext to move the optimum condition close to 200kW. Additionally, the step due to the difference in the height of the coupling waveguide on the cavity and that of the vacuum side waveguide on the window results in a standing wave between the cavity and the window even at matched operation. The 3 stub tuner further enhances this standing wave. Numerical simulation reveals that the standing wave field from the cavity penetrates into the coupling waveguide increasing the probability of multipactor and breakdown in the coupler region. The results of multipactor simulations in this region with CST Studio are discussed.

Journal Keywords: ion; cavity; pick-up; GUI; electron

Subject Areas: Technique Development

Technical Areas: RF