M. V. Fazio, B. Carlsten, C. Fortgang, K. Habiger, E. Nelson,(LANL), B. Arfin, G. Caryotakis, A. Haase, G. Scheitrum (SLAC)
A one-gigawatt, annular beam klystron (ABK) is being developed by Los Alamos National Laboratory in collaboration with the Stanford Linear Accelerator Center (SLAC). The pulse length is 1 5s, the pulse repetition frequency 5 Hz, and the operating frequency is 1.3 GHz. The beam voltage and current are 800 kV and 4 kA. One of the most challenging aspects of the tube design is the electron gun that must produce a stable, high current, annular electron beam with reasonable lifetime and reliability. For reasonable extraction efficiency, a klystron operating in the high current regime must use an annular beam to avoid the electron kinetic energy loss caused by potential depression due to the high space charge. Achieving a stable electron beam with minimal scalloping is critical because the beam must flow within a few millimeters of the drift tube wall to minimize the beam potential depression. Since the gun parameters are considerably beyond the state-of the-art, an aggressive cathode and gun design is required. The magnetron injection gun (MIG) configuration was chosen over the Pierce geometry that is typically used in klystrons. The MIG design is based on modeling with several codes including DEMEOS, EGUN, and ISIS, and uses a dispenser cathode that will operate near the limit of the maximum emission current density for reasonable cathode lifetime. The tube is being built at the SLAC klystron fabrication facility. RF conditioning over several million pulses and full power testing will be performed at Los Alamos on the Banshee modulator which produces a 1 5s pulse length at 5 Hz pulse repetition frequency. The tube design, design issues, and status are presented.
* Work supported at LANL under U.S. DOE Contract W-7405-ENG-36
Comments or Questions to