Spatially Distributed Electron Beam Gun for High Pulse Repetition Rate Operation

AbstractWe propose to design an electron gun to produce a 20 kV and 1 A spatially distributed (aspect ratio of 5:1) electron beam for use in a Ka-Band slow-wave device. We will develop a compact periodic permanent magnet focusing system to transport this beam over a minimum distance of 10 cm. A multi-stage depressed collector will be designed to recover energy from the spent beam while minimizing the effect of the collector depression on the RF operation of the tube. We will investigate the use of novel high current density scandium nanopowder cathode technology to achieve > 20 amp per square centimeter emission density at the cathode to result in a highly laminar beam to improve the overall beam transport and efficiency. The goal will be to achieve this current density at operating temperatures of ?800°C for lifetime. This work will include complete mechanical design of the electron gun and a beam stick followed by thermal and structural analysis.