PEFP HOM coupler design

A new type of coaxial higher-order mode (HOM) coupler with one hook and two stubs has been designed for PEFP SRF cavities to satisfy the HOM damping requirements of the superconducting RF (SRF) linac of the Proton Engineering Frontier Project (PEFP), and to overcome the notch frequency shift and feed-through tip melting issues. This paper presents details on the PEFP HOM coupler's structure, structure optimization, filter characteristics, electro-magnetic field distribution and a coupler installation tool.