The A6 (six cavity) magnetron operated at relativistic voltages is investigated using three-dimensional particle-in-cell simulation. Previous experiments [A. Palevsky and G. Bekefi, Phys. Fluids 22, 986 (1979)] are repeated numerically for the purpose of ascertaining fidelity of code results in addition to obtaining insight into magnetron operation at high voltage. Simulations produce all qualitative behavior observed in experiments, with good quantitative agreement in most cases. This numerical study also reveals details concerning mode control, the cause and prevention of leakage current, and voltage scaling in the A6. It is shown that: (1) leakage current substantially reduces efficiency, (2) elimination of leakage current using cathode endcaps substantially increases efficiency, and (3) the functional dependence of operating voltage on applied magnetic field may depart from conventional scaling at very high voltage. (C) 1999 American Institute of Physics. [S1070-664X(99)01902-3]. [References: 17]
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