A Nb TM010 MODE CAVITY WITH HIGH ELECTRIC FIELD AND Q0

Abstract

A superconducting Nb TM₀₁₀ mode cavity at 8.5 GHz machined from a single piece of reactor‐grade electron‐beam‐melted Nb to avoid joints had an unloaded Q (Q₀) of 2 × 10¹⁰. After some degradation in the Q₀, which took place as the microwave fields were increased, a high Q₀ of 1 × 10⁹ was obtained at a peak electric field on the cavity surface of 27 MV/m. These results were obtained by using ultrahigh‐vacuum firing and chemical polishing of the Nb cavity, and ultrahigh vacuum within the cavity during measurement. The high Q₀ at high electric field demonstrates the usefulness of superconducting Nb cavities for devices such as linear particle accelerators and rf separators.