High-pressure runaway-electron-preionized diffuse discharges in a nonuniform electric field

High-pressure nanosecond diffuse (volume) discharges in a nonuniform electric field are studied experimentally using a recording system with a ?100-ps time resolution. As the voltage pulse shrinks to a width of ≈100 ps, the initiation of a diffuse discharge without a source of additional ionization is facilitated; specifically, a runaway-electron-preionized diffuse discharge is ignited in atmospheric-pressure air in the case of short interelectrode gaps. It is found that a major energy deposit into the plasma of this discharge is from an abnormal glow discharge following a maximum of the gap voltage.