Performance of Multipactor Coatings Applied Using Atomic Layer Deposition

Multipactor emission can be as serious problem for high power RF devices, particularly RF windows. It can lead to destructive heating of the ceramic or arcing on the window surface. This is typically addressed by sputtering a thin layer of titanium nitride on the vacuum side of the window ceramic. This works well for relatively small ceramics but leads to poor uniformity over large surfaces. High power RF windows are required at 704 MHz, which require windows approximately 23 inches in diameter. This is larger than can be reliably coated using sputtering. This research is developing technology to apply Multipactor suppression coatings using Atomic Layer Deposition (ALD), which provides unprecedented control of the coating thickness and uniformity. It is independent of surface area and allows coating of multiple surfaces in parallel, with associated cost reduction. In addition, ALD bonding is stronger than that provided by sputtering, leading to more robust protection. This presentation will describe the ALD system and process. Test structures were fabricated, and the RF loss and secondary electron yield were measured. The measurement system and results will also be presented.