Mode Launcher Design for the Multi-moded DLDS

The DLDS (Delay Line Distribution System) power deliv- ery system proposed by KEK combines several klystrons to obtain the high peak power required to drive a TeV scale linear collider. In this system the combined klystron out- put is subdivided into shorter pulses by proper phasing of the sources, and each subpulse is delivered to various ac- celerator sections via separate waveguides. A cost-saving improvement suggested by SLAC is to use a single multi- moded waveguide to deliver the power of all the subpulses. This scheme requires a mode launcher that can deliver each subpulse by way of a different waveguide mode through se- lective phasing of the sources when combining their power. We present a compact design for such a mode launcher that converts the power from four rectangular waveguide feeds to separate modes in a multi-moded circular guide through coupling slots. Such a design has been simulated and found to satisfy the requirements for high efficiency and low sur- face fields.