A 28 GHz gyrotron with a permanent magnet system

Abstract The design and experimental results of a 28 GHz, TE02 mode gyrotron with a permanent magnet system are presented. The permanent magnet system provided the axial magnetic field of about 5.3 kG, which is required to operate the 28 GHz gyrotron at the second cyclotron harmonic. Supplementary coils were wound directly around the gyrotron to adjust the main and the electron gun magnetic fields to optimize the oscillation for each electron beam voltage and current. An output power of 11.6 kW was obtained at a beam voltage of 30 kV with a beam current of 1.5 A, corresponding to an efficiency of 25.8%. The experimental results were in good agreement with the calculated results.