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Jack WatrousNumerEx A magnetron concept using field emission cathodes has been modeled with the Air Force Research Laboratory particle-in-cell code ICEPIC and the 2D particle trajectory simulation Lorentz2E. In this approach, field emitters are used to provide a distributed cathode in place of a traditional thermionic cathode. The emitters are placed below the interaction space in a shielded structure. The cathode is comprised of facet plates with slits to protect the emitters. Simulation of an L-band rising sun magnetron shows that the faceted magnetron will oscillate using both five and ten facet cathodes. The startup times are very similar to that of a cylindrical cathode magnetron. The electron trajectories of the shielded slit structure have been modeled, and the results indicate that electrons can be injected through the slits and into the interaction space using lateral edge emitters and a pusher electrode design.

A rotating field antenna set — a pair of two closely spaced dual half-turn antennas — is used to tailor the azimuthal spectrum of the antenna field. It is demonstrated that the azimuthal mode of ICRF waves can be controlled by proper phasing of the antenna set. Ion heating is shown to be strongly dependent on the azimuthal mode number. When the antenna set is operated in the m = −1 (left rotating) mode, the m = −1 modified ion cyclotron wave is selectively excited, resulting in efficient ion heating.

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