Novel hom damper design for high current srf cavities*

The ERL-Ring eRHIC design incorporates a new high current (50 mA), multi-pass (6 passes) ERL, generating 5-18 GeV electron beams to collide with the ion beams of the existing RHIC. One critical challenge for eRHIC is to damp HOMs. The average HOM power is up to 8 kW per cavity, potentially much more if the electron beam spectrum overlaps with cavity HOM spectrum. We present a novel HOM damping scheme, employing ridge waveguides, which is able to well damp both longitudinal and transversal modes. This paper will describe the design of the HOM damping scheme, including RF design, HOM damping results, progress of prototyping.