Overmoded Waveguide Components for High-Power RF

High-power applications of rf often require the use of overmoded waveguide to reduce the probability of rf breakdown by lowering surface fields, as well as to reduce the attenuation due to ohmic losses in transporting the power from the point of generation to the point of use. This is particularly true in the development of warm linear collider designs, such as NLC, JLC, and CLIC, especially the former two which involve extensive rf pulse compression / power distribution systems. Transitioning to and from overmoded waveguide and manipulating rf in such systems requires specialized components in whose design care must be taken to avoid parasitic mode loss and excessive field enhancement. Although fixed frequency operation means modest bandwidth requirements, power levels up to several hundred megawatts must be accommodated, and efficiency is important. Consequently, physicists working at laboratories engaged in the above efforts have produced a number of novel waveguide components in the past several years. These include tapers, mode converters, bends, directional couplers, power splitter/combiners, switches, phase shifters, etc. Often the circular TE01 mode is used for its lack of surface electric field and low attenuation. A class of components using planar geometries for over-height rectangular waveguide has been developed at the Stanford Linear Accelerator Center. The current paper describes a few additional passive high-power components that have not been presented elsewhere -way power splitter, fractional directional couplers and tap-offs. These were designed at X-band as part of the NLC R&D, but may find wider application.