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Split Higher Order Modes in superconducting cavities

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Abstract

Split resonances are a common appearance in superconducting cavities and are studied here on the specific examples of the TE11 and TM11- like dipole resonances in five-cell copper models of the Brookhaven ERL and BNL3 cavities. The BNL3 was designed to be suitable for the envisioned high-intensity projects at this laboratory. Achieving the required high current performance depends on avoiding beam-breakup instabilities by minimizing the Higher Order Modes (HOM) Q-values. This was attempted in the design phase and will be done with appropriate mode dampers in operation. The availability of a copper model provided the convenient opportunity to confirm the design and to study potentially nefarious high-Q resonances. The appearance of split resonances impeded the HOM identification and the theoretical interpretation as ellipticity deformation is presented in this paper. Copyright © 2013 by JACoW- cc Creative Commons Attribution 3.0 (CC-BY-3.0).

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