Development of a High-brightness Field-Emission Superconducting RF Gun

Field emission cathodes are well known in the field of electron microscopy and extensively used because their very small source size (e.g.: sharpened end of a needle) can lead to very high- brightness electron beams. Recently, important developments in field-emission arrays have made them a viable option for the generation of high-quality beams with improved current as compared to a single tip. An RF electron gun based on a field-emitter cathode could produce high-brightness bunches and maintain their quality by accelerating them rapidly in high electric fields. Such a gun that was also superconducting could, in turn, support those high fields at full duty factor for increased current with minimal dissipative losses. This SBIR proposal seeks to build on the experience gained at Niowave, Inc. in superconducting quarter-wave resonator electron guns and the technology in field-emitter arrays developed at Vanderbilt University to develop a novel high-brightness gun. Depending on the size of the emitter (from a single tip to an array of aligned tips), a number of important applications are foreseen, from electron microscopy and high-frequency microwave generation to high-brilliance x-ray sources. The quarter-wave design offers flexibility in cathode choice because the cathode stalk can be mechanically and thermally isolated from the superconducting niobium cavity.