Speaker
Description
SRF technology enables particle accelerators to operate with greater average beam currents and higher duty cycles. In these regimes parasitic excitation of the cavity High Order Mode (HOM) spectrum becomes the limiting factor due to extra RF losses and the beam instabilities. We discuss the limitations of HOMs for large accelerator projects such as the Fermilab MI upgrade and the proposed future circular and linear colliders EIC and ILC. A new compact HOM damper concept would provide required HOM suppression. The idea is based on using an oversized coaxial line with a half-septum insert directly connected to the axial region of the SRF cavity. Such radially sectioned coaxial acts as a low-pass filter for the operating mode, while remaining transparent for the HOMs. Implementations of this design for the accelerating and crab cavities developed for the ILC, MI and EIC machines, respectively, are discussed. We pay particular attention to evaluating limiting factors such as multipactor phenomena in the coaxial line, suppression of arbitrary polarizations of dipole HOMs, and the possibility of integrating the proposed designs with proven solutions for broadband HOM absorbers.
Funding Agency
US Department of Energy
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