Surface Films to Suppress Field Emission in High-Power Microwave Components

75119-The achievement of high microwave fields in next-generation high-energy particle accelerators will require, among other things, that field emission and breakdown be held to within strict upper limits. One means to achieve this goal is to devise rugged thin-film coatings for vulnerable copper surfaces, providing a higher work function than copper alone. This project will evaluate a variety of candidate thin-film coating materials for inhibiting field emission in high-power microwave components and develop recipes for applying these coatings to copper test blanks. Phase I will develop a variety of thin-film materials, including the possible use of intermediate adhesion layers and outer anti-oxidizing layers, for application to copper test blanks. An X-band test cell will be designed to achieve a microwave electric field strength on the coated test blanks that is more than double the field strength on other surfaces in the test cell. A non-high-vacuum model of the test cell will be built and cold-tested. Ultimately, comparisons will be made between the thresholds for microwave breakdown (as well as the rates of breakdown above threshold) in coated and uncoated test blanks; the difference in performance of the various coating materials also will be examined. Commercial Applications and Other Benefits as described by the awardee: Thin-film coatings on high-power microwave components should extend the parameter range over which the components can be used, especially in high-power installations at accelerators. Other applications requiring high-power microwaves include radar and high-power microwave industrial processing.