Recent work on an improved vacuum diode for an annular beam amplifier and initial results of rf extraction

Summary form only given. Development work is underway on a high current (16 kA), mildly relativistic (400 kV), L-band Klystron source. The electron beam diode and rf extraction circuits are two key areas in this work. The diode is to provide approximately 7 GW of electron beam power for 1 microsecond for partial conversion to rf energy by a 2 or 3 cavity Klystron amplifier system. The present configuration will be shown. Results of calculations for the magnetic beam optics, electrostatic potential structure, and self-consistent emission PIC simulations will be presented. Experimental results will be shown of the vacuum diode performance. The intense beam emitted by the diode presents unique design complications in connection with extraction of rf power. Various considerations are discussed such as the trade-offs between beam potential and kinetic energies, optimum shunt, impedance values, and advantages of discrete vs. distributed circuits. The various circuits that have been considered include conventional single gap designs, a distributed interaction structure, and a single gap triaxial circuit. Designs have been analyzed using analytical methods, rf codes, and particle in cell simulations. A description of the experimental hardware is given along with results of cold tests and power extraction results.