Adjustable input couplers for both normal conducting (NC) and superconducting (SC) RF cavities are among the highest priorities for advanced accelerators at DOE user facilities. However, existing adjustable couplers are severely limited by the range of coupling coefficients, as well as by their size and complexity. This project will undertake a novel approach for designing RF couplers, which will impact the variation of the standing wave ratio (SWR) by more than an order of magnitude during operation. The design is based on the introduction of capillary dielectric tubes or fluid-filled volumes adjacent to, but separated by window(s) from, the coupler. The proposed method of in situ adjustment of the external Q will provide a simple and flexible means of meeting the performance requirements of a large variety of vacuum electronics devices. Commercial Applications and other Benefits as described by the awardee If successful, the new technology should significantly improve the performance, and provide enhanced flexibility, of heavily loaded accelerating structures and high power RF sources. Facilities and projects such as energy recovery linacs (ERLs), upgrades of existing machines such as CEBAF and APS, and future particle colliders (such as the ILC) would be greatly impacted.
