Development of a broadband HOM load for the 714-MHz HOM-damped cavity

A 714-MHz higher-order-mode (HOM) damped cavity was developed at KEK, and two cavities of this design are under operation in the Accelerator Test Facility (ATF) damping ring. Each cavity is equipped with four waveguide ports to extract HOM power. In order to achieve the very low HOM impedance required for the damping ring, each waveguide port should be terminated by a broadband, low-reflection load. We have developed a broadband HOM load for this purpose. We describe the design, construction and RF characteristics of the HOM load.