Progress on high-power magnetrons and vircators

The PI Microwave Group is studying two very different types of High-Power Microwave Sources: Relativistic Magnetrons and Virtual Cathode Oscillators. The vircator is a broad band tunable microwave source producing short pulses with a 1 GHz bandwidth. The frequency is tunable using the AK gap, efficiency is ≅ 1%. In a high current diode the dominant radiation mechanism is the oscillation of the virtual cathode, not the reflexing of electrons. Radiation occurs after diode pinch and is accompanied by partion of the electron population into a reflexing electron component and a propagating beam component. Recent experiments have studied the interaction of the vircator with a resonant cavity. The cavity suppress frequencies not in resonance with the cavity modes and thereby limits bandwidths to less than 100 MHz. Overall efficiency is improved by a factor of about 4 by non-linear feedback interaction between the cavity and the oscillating virtual cathode. Magnetrons are a fixed frequency, high-power source with a narrow bandwidth. Recent experiments have extracted power from six waveguides of a 2.8 GHz device operating in the π mode. Configurations using this multi-arm device for production of propagating pulses are described