Pulsed radiation generation in closed and open cavity gyrotrons

Summary form only given, as follows. Recent nonlinear, time-dependent studies indicate that radiation pulses can be generated using a tapered closed-cavity gyrotron oscillator. A cavity composed of a radially tapered section and a straight section of waveguide is designed, built and cold-tested. The resonant TE/sub 11n/ modal set is almost equally spaced in frequency. Using a sinusoidal current density modulation with an amplitude of 5% of the DC current and frequency of 280 MHz (the inter-mode frequency spacing), the simulation results show radiation output in a train of narrow pulses (/spl sim/1 ns) at a 280 MHz repetition rate. Pulsed radiation using an open-cavity (quasi-optical) cavity gyrotron is under investigation. In this case the electron beam passes through a Fabry-Perot resonator and modes are typically weakly coupled. Velocity or current density modulation at half of the bounce frequency in cavity is used to generate short-pulse periodic output from the quasi-optical gyrotron. Numerical simulations based on slow time scale equations for the electron momentum and the amplitude and phase of the electromagnetic field are presented.