HOM Damping of Ares Cavity System for SuperKEKB

The ARES cavity system, developed to minimize the coupled-bunch instability due to the accelerating mode, is one of the decisive edges of KEKB. Its RF scheme is a coupled-cavity system where an accelerating cavity is coupled with a large energy storage cavity via a coupling cavity between. The accelerating cavity, itself, is a HOM-damped structure smoothly embedded into the whole coupled-cavity scheme. Currently, the total HOM power dissipated in the RF absorbers per cavity is 5.6 kW for the KEKB LER with beam current of 1.6 A. For SuperKEKB aiming at the luminosity frontiers far beyond 10³⁵cm^-2s^-1, the total HOM power per cavity is estimated about 95 kW for the LER with the design beam current of 9.4 A. This article reports the design of a HOM-damped structure for the SuperKEKB ARES cavity, together with related R&D activities.