A High Power CW Input Coupler with Reduced Static and Dynamic Losses

One group of critical components of the eRHIC project are SRF cavities operating at 647 MHz. The cavities require couplers that can reliably operate at CW levels of power approaching 30-50 kW. Euclid Techlabs proposes to develop couplers for 650 MHz range but average power up to 100 kW that will allow their use for the eRHIC project. The goal of the proposed project is to increase coupler reliability by building and testing a novel coupler design concept which does not require a copper coating. The novel design employs an RF shield to significantly decrease magnetic fields on the outer wall of the coupler, thereby reducing induced currents to a level where copper plating is no longer needed. An important side benefit is that the new design has substantially smaller cryogenic losses, both static and dynamic. The goal of Phase I will be choosing the design that is most cost effective both to build for the 647 MHz frequency range. We plan to develop a new conceptual design at 650 MHz of 100 kW average power coupler using solid copper shield modifications. We plan to carry out electrodynamic modeling of the new version of the 647-650 MHz coupler including bandwidth simulations and electric and magnetic field magnitude analysis; multipactor modeling for the proposed 650 MHz coupler design to prevent multipactor development on the coupler metal surface, and conduct a thermal analysis. Commercial Applications and Other Benefits: The proposed work seeks to mitigate the significant risk associated with high average power RF couplers for SRF cavities, key elements of both large science accelerators and advanced industrial SRF electron accelerators. Couplers with reduced heat leak will enable high energy SRF machines and compact industrial accelerators cooled by cryocoolers, therefore significantly improve the operational reliability of power couplers in superconducting accelerators.