A proposed 4 GHz, 60 kW transit-time oscillator operating at 18 kV beam voltage

A high-power transit-time oscillator operating at 4.0 GHz in the cylindrical-cavity TM/sub 010/ mode is proposed. Without requiring an externally applied magnetic field, the oscillator comprises a diode electron gun and a cylindrical cavity that are combined into a single unit that makes for a compact, lightweight device. The transit-time effect, which underlies the operation principle of the oscillator, is examined through a small-signal analysis from which a relation embodying the cavity length, resonant frequency, and cathode voltage is derived. Proper DC voltages of 18 kV are applied to the diode gun which runs in the space-charge-limited regime and produces a 27 A-current hollow electron beam. Output power is extracted axially from the system by aperture coupling the cavity to an external waveguide where outgoing travelling waves with 60 kW peak power are observed by means of 2.5 D particle-in-cell computer simulations.