Three-dimensional Particle-In-Cell (PIC) simulations of a conventional, strapped, oven magnetron, including the effect of periodic variations in the insulating magnetic field

Summary form only given. We report on three-dimensional simulations of a conventional oven magnetron, operating at near 2.5 GHz, performed with the parallel Particle-In-Cell (PIC) code ICEPIC. Including the details of strapping, thermionic emission, and output power extraction, the calculations produce excellent agreement with experimentally observed quantities such as frequency, anode current, and output power. The self-oscillation condition, mode competition, and growth rate of the pi mode is examined as a function of cathode current, and found to agree with experimental results. Specifically, the details of spoke formation under various emission assumptions (thermionic and space charge limited emission) discussed. Finally, the inclusion of permanent magnets to produce a periodic variation in the strength of the confining magnetic field is shown to greatly reduce the time to steady-state operation in the pi mode, even at very low levels of cathode current. The physics of this situation, and the implications on the noise production of the device, discussed.