Simulation and analysis of a reentrant planar magnetron

The self-consistent PIC code MAGIC, has been used to simutate a planar magnetron with a reentrant boundary condition. The dimensions of the gap and slow-wave structure were selected to give a pi-mode resonance at 18 GHz. Simulations of a ten-vane structure were performed both with and without energy extraction. As a result of the soliton theory applied to the Cross Field Devices (CFD´s) the early time behavior of the space-charge layer is thought to be dominated by a long wavelength modulational instability (1). A space harmonic analysis of the TM fields was performed to obtain the growth rates of the low order space harmonic modes. Phase locking of the electrons leads to enhanced RF fields as energy is exchanged. The enhanced electric fields promote growth of the shorter wavelength modes. In addition, a space harmonic analysis of the energy density was made to determine the power spectra of the space-charge layer. The observed power law is consistent with that predicted for the turbulent spectrum of an imcompressible fluid.