Improved Magnetron Injection Guns for Gyrotrons

75258S Gyrotrons and gyroklystrons, used for high power RF applications in the DOE Fusion Program, are being adversely impacted by poorly performing cathodes for which the current emission is not uniform over the entire surface. Poorly performing cathodes adversely impact all RF vacuum electron devices, including those used for accelerators, radar, communications, medical applications, and industrial heating. This project will determe the specific causes of poor cathode performance and developing cost effective solutions. In particular, controlled porosity cathodes will be developed to address problems with uniform work function of the emitter surface. Improved mechanical and thermal designs will provide uniform emitter temperatures and lower the cost of cathode assemblies. Phase I identified specific causes of temperature variation in magnetron injection guns and established a preliminary thermal model to analyze the problems and develop practical solutions. A concept for manufacturing controlled-porosity cathodes was developed and experimentally verified. Phase II will complete the development of controlled-porosity cathodes by defining specific processes for determining pore size and density. The results will be correlated with the barium diffusion rate to allow an optimal design, based on current density and lifetime requirements. Techniques for improved thermal performance will be developed and experimentally tested. The mechanical design of cathode heater assemblies will be improved to simplify the construction process. Commercial Applications and Other Benefits as described by the applicant: The results of this project should reduce the cost and risk in the manufacture of cathodes for all vacuum electron devices. The concepts will be applied to magnetron injection guns for gyrotrons, which represents the greatest challenge. Successful completion should reduce the risk and improve the performance of gyrotrons for fusion, accelerators, defense, and industrial applications, with subsequent reductions in cost.