Development of Miniature Sheet Beam Plasma Cathodes for Rapid Prototyping of Submillimeter Wave Sources

Recent interest in the development of submillimeter-wave sources has been motivated by the need for high resolution imaging systems. These systems will require power levels that only vacuum electronics technology can currently provide. In support of these efforts, new design codes that treat the electrodynamics of particles in 3D fields and mode competition in planar slow-wave structures are under development. However, the cost of new electron guns for these applications can be prohibitively high, particularly in the early stages of a program where many technological and scientific issues still must be addressed or have not been identified. We have proposed the development of a rapid prototyping facility for hot testing new submillimeter wave structures. We also intend to provide useful data for verifying the new codes. The advantage of this concept stems from the electron source, which is a gridded plasma cathode. The gun is capable of generating current densities of more than 1 kA/cm² in a nominal vacuum (~10^-5.Torr). The source is mounted in a vacuum chamber equipped with a large access lid, multiple vacuum ports, electrical feeds, probe micropositioner and a turbo-molecular pump. The time to cycle the vacuum station in order to make changes to an experiment and bring the gun back into operation can be as little as 15 minutes. We will present an overview of the test facility and discuss the gun work in detail. A plasma cathode which generates a 0.15x3 mm sheet beam has been designed, constructed and is now undergoing testing. The results of experiments on variable perveance operation, the current-voltage characteristics and beam current distribution and propagation will be presented.