PPPS-2013: Controlled Porosity Reservoir cathodes and photocathodes

Summary form only given. Controlled Porosity Reservoir (CPR) cathodes offer high current density operation with long life and superior emission uniformity [1]. Calabazas Creek Research, Inc. (CCR) recently delivered a 100 KW, X-Band, multiple beam klystron (MBK) with fifteen CPR cathodes operating at 30 A/cm² and is currently fabricating a magnetron injection gun and an annular beam klystron (ABK) using the cathodes. The high current density capability eliminated beam compression for the MBK and ABK, dramatically simplifying the design. CCR, in collaboration with the University of Maryland, implemented CPR technology into cesiated tungsten photocathodes. Photocathode tests demonstrated superior performance over previous designs with an increase in lifetime exceeding two orders of magnitude. Research improved theoretical modeling of Knudsen Flow and barium evaporation, leading to an advanced computational tool for designing CPR cathodes. Research is continuing to improve CPR cathode quality and fabrication procedures with the goal of reducing cost and increasing the applicability. CCR is developing small CPR thermionic cathodes for W-Band and THz RF sources and large cathodes for multi-megawatt klystrons at X-Band and L-Band. A gridded design is in development for a 5 MW, X-Band, RF source. The U.S. Department of Energy has funded development of CPR photocathodes using alternative materials. This program will investigate atomic layer deposition to modify the surface characteristics to increase quantum efficiency. The goal is to increase both the efficiency and the lifetime by 2-3 orders of magnitude. This presentation will describe improvements in CPR cathode quality and fabrication processes achieved during the last year. It will also describe the innovative photocathode configuration developed by UMD. Test results will be presented on cathode measurements as well as performance of devices using CPR cathodes.