Mode competition in harmonic magnicon amplifiers
- Naval Research Lab., Washington, DC (United States)
In the magnicon rf amplifier, the drive and gain cavities are cylindrical deflection cavities which operate in a rotating TM{sub 110}-mode and spin up an electron beam to high transverse momentum. As a result of the rotating-mode interaction, the electron beam entry point into the output cavity rotates about the axis at the drive frequency. The gyrotron-like output cavity can be operated at m times the drive frequency by using a mode with an azimuthal index of m., as this mode rotates at m{sup {minus}1} times its rf frequency, thus maintaining synchronism with the electron beam. Lowering the frequency of the deflection cavities allows lower rf fields, reducing cavity breakdown problems, lower magnetic fields, reducing magnet cost and complexity, and a larger electron beam, relaxing beam quality constraints. On the other hand, higher order azimuthal index magnicon modes interacting at higher order cyclotron interactions are subject to competition with nonsynchronous modes and are more sensitive to electron beam scanning angle spread. A time-dependent, multimode gyrotron code has been modified to examine competition in the output cavity between the phase-synchronous operating mode and other nonsynchronous modes which interact via the conventional gyrotron interaction. Calculations have been carried out for magnicons with TM{sub 410} and TE{sub 411} mode output cavities and include the effect of a spread in gyro-angles in the scanning electron beam.
- OSTI ID:
- 170226
- Report Number(s):
- CONF-950612--; ISBN 0-7803-2669-5
- Country of Publication:
- United States
- Language:
- English
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