Microwave Breakdown of Air by Nanosecond and Subnanosecond Ka-Band Pulses

The initial stage of atmospheric air breakdowns in Ka-band pulsed microwave fields was observed for the microwave power increasing to a maximum within a characteristic time of ~300 ps. Pulsed microwaves were produced by relativistic BWOs with output powers of ~170 and ~500 MW (4-ns and 300-ps FWHMs, respectively). The effects of air breakdown in the fields of microwave pulses of this type are pronounced when the radiation is extracted through the vacuum window of a horn antenna and when it is channeled in passing through waveguides and quasi-optical lines. Of particular interest are modes in which repetitive pulsed microwaves are generated.