Novel RF Couplers with Double Windows Design for the ILC

The ILC accelerator project will require several thousand superconducting radio frequency (RF) cavities with critical RF Input Couplers. These cavities require ultra-clean vacuum and surface cleanness; however, the breakage of a ceramic RF coupler window, with the consequent inrushing of air and contaminants, can have catastrophic effects on performance, and would require a time consuming and expensive overhaul of the accelerator. To eliminate or minimize this potential risk, the large particle accelerators are increasingly requiring a double windows design with a vacuum space between the two windows. However, the high cost of conventional double windows dictates the need for an innovative coupler design and efficient manufacturing. This project will develop a novel double-window RF coupler design that utilizes a combination of features, including selective capacitive coupling of the inner conductor, the removal of the bellows, and a permanent vacum system for the space between the double windows. In Phase I, the feasibility of the innovative double-window coupler for the ILC will be theoretically calculated for different alternatives, and the optimum solution will be selected for Phase II. In Phase II, a prototype coupler for the ILC will be designed, fabricated, and tested with high RF power. Commercial Applications and other Benefits as described by the awardee: Cost effective, operationally reliable, and system-simplified RF coupler designs should find wide use for many DOE projects besides the ILC. The technologies should have a very strong impact on the cost of the RF input couplers and associated equipment for the ILC project, and for the high RF products industry.