Ultra-low B-field magnetron operation at the drift-cyclotron resonance

In magnetrons operating near the Buneman-Hartree resonance ku-/spl omega/=0, u being the E/spl times/B drift velocity, the energy stored in the cyclotron motion is not converted into microwaves, and the efficiency decreases at low magnetic fields. By operating at the drift cyclotron resonance ku-/spl omega/=/spl Omega/, both the electrostatic and the cycloidal motion energy are converted to radiation and the efficiency increases at low magnetic fields. At optimum efficiency all normalized operation parameters are expressed solely in terms of the cyclotron-to-RF frequency ratio. For a specified anode circuit it is shown that the DC electric and magnetic field can be reduced by a factor 6-10 relative to the conventional operation, with electronic efficiency in the 50%-70% range. Moderate power S-band crossed field amplifier operation at 400 Gauss magnetic field is demonstrated by numerical simulations. UHF operation is conjectured at 40-50 Gauss produced by solenoids without iron cores.