Speaker
Description
High-order mode (HOM) damping is a critical aspect of ensuring beam stability and operational reliability in the future circular collider (FCC-ee). The FCC-ee RF system must accommodate a wide range of beam parameters, covering working points from the Z energy level, with Ampere-level beam currents, up to the $\mathrm{t\bar{t}}$ energy, with a total RF voltage of 11.3 GV. This presentation will discuss the HOM damping strategies developed for the FCC-ee superconducting cavities. For the 2-cell 400 MHz cavities used at collider working points, the damping scheme is designed to strongly suppress HOMs and extract kilowatts of HOM power, which is particularly crucial at the Z working point. This is achieved through a combination of coaxial HOM couplers and beamline absorbers (BLA). For $\mathrm{t\bar{t}}$ operation and the booster, the smaller beam currents allow the use of 6-cell 800 MHz cavities with a damping strategy comprised of coaxial couplers and BLAs. The presentation will cover the FCC-ee RF system baseline, the damping strategy for each working point, sensitivity analysis of the cavities, and the current challenges in the design.
