Generation of subnanosecond electromagnetic pulses by a meter-long laboratory spark discharge: A source in the near-cathode region

Ultra-wideband (UWB) subnanosecond electromagnetic pulses (EMPs) generated by a 1.3 m long positive spark discharge with a Marx generator having an operating voltage of about 1 MV are studied experimentally. Special electric and magnetic probes, which allow reproducing reliably the waveforms of subnanosecond pulses, were used to establish that the main component of the gigahertz radiation has the form of a UWB EMP with a duration of about 350 ± 150 ps and a rise time of about 200 ± 100 ps. The reception of EMPs by several spaced probes with synchronous high-speed photography makes it possible to localize the radiation source near the grounded electrode, i.e., the discharge cathode, and to associate the time of EMP emission with the start of a counterstreamer when the streamer corona of the positive high-voltage electrode (anode) approaches the grounded cathode. The results of these experiments, as well as a series of other works carried out in recent years, allow us to assert that the generation of subnanosecond UWB EMPs is a universal effect that develops in the near-cathode region of long spark discharges and is presumably caused by the formation of subnanosecond electron avalanches.