An electron gun for a sheet beam klystron

Calabazas Creek Research, Inc. is developing rectangular, gridded, thermionic, dispenser-cathode gun for sheet beam devices. The first application is expected to be klystrons for use in advanced particle accelerators and colliders. The current generation of accelerators typically use klystrons with a cylindrical beam generated by a Pierce-type electron gun. As RF power is pushed to higher levels, space charge forces in the electron beam limit the amount of current that can be transmitted at a given voltage. The options are to increase the beam voltage leading to problems with X-ray shielding and modulator and power supply design, or to develop new techniques for lowering the space charge forces in the electron beam. The current program addresses issues related to beam formation at the emitter surface, design and implementation of shadow and control grids in a rectangular geometry, and is directed toward a robust, cost-effective, and reliable mechanical design. A prototype device will be developed that will operate at 415 kV, 250 A and be designed for an 80 MW, X-Band, sheet-beam klystron. The cathode will have 100 cm² of cathode area with an average cathode current loading of 2.5 A/cm². For short pulse formation, the use of a grid was chosen. We will report the electrostatic and beam optics design in both 2- and 3-D as well as a thermal-mechanical analysis of the cathode region.