Investigation of microwave breakdown in the relativistic Cherenkov-type devices

Microwave breakdown is one of the main reasons which limit the power and the pulse duration of output radiation in microwave devices driven by high-current relativistic electron beams (REBs). At an RF field of more than 300 kV/cm, the microwave pulse duration is determined by the time of development of explosive emission (EE). At smaller field, the microwave breakdown is initiated by RF discharges or bombardment of a slow-wave structure (SWS) by charged particles. The present work is devoted to the peculiarities of such initiation. An X-band, E₀₁ -mode relativistic carcinotron operating with moderate power of output radiation was used as the tested device. The rated REB diameter in the SWS was 15 mm. The REB formed both in the coaxial diode conventional for relativistic electronics (edge cathode of 32 mm in diameter) and in the magnetron-injection gun with thermionic cathode (the emitter diameter 100 mm)