RF Loads for the CLIC Multibunch Structure

The CLIC multibunch accelerating structure, called the TDS (Tapered Damped Structure), relies on heavy damping of higher-order modes. Each cell of the structure is damped by its own set of four individually-terminated waveguides. A compact, low-cost and large-bandwidth terminating load with a reflection coefficient below 0.05 has been developed for this application. The load consists of a silicon carbide pyramid centered in a tapered waveguide. The design process, including the technique used to measure complex permittivity, is described. Measurements made on scaled prototypes are presented.