COHERENT, TUNABLE, CYCLOTRON MODE OSCILLATIONS IN A SMOOTH-BORE MAGNETRON.
FLORIDA UNIV GAINESVILLE ELECTRON DEVICES LAB
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Coherent CW oscillations are generated in a smooth-bore magnetron when the end plates are operated at anode potential allowing the electrons of the discharge to stream axially to them. These oscillations, which occur in a coaxial cavity whose lowest order resonance TEM is about 8.5 GHZ, are continuously tunable from 700 MHZ to 3 GHZ by varying the magnetic field. The frequency is nearly, but not exactly, the electron cyclotron frequency. For this reason, this oscillation is referred to as the cyclotron mode, to distinguish it from other modes which are observed to appear only with critical values of discharge current and magnetic field. The device operates well below Hull cut-off conditions, and the flow of current to the end plates under such conditions requires a scattering mechanism leading to a collision term in the transport equations. The scattering mechanism postulated by Mouthaan and Susskind, based on an inherent instability in crossed-field electron streams exposed by Buneman, leads to theoretical volt-ampere characteristics qualitatively and quantitatively in good agreement with those measured. A non-linear analysis of the electron discharge resulting is presented. A small signal analysis of the normal modes of a sheet beam of electrons streaming with constant DC velocity at the Hall angle is developed. Six normal modes are exposed, all of which are coupled as a consequence of space-charge fields. Author
- Electrical and Electronic Equipment
- Nuclear Physics and Elementary Particle Physics