The Nanosecond Impulsive Breakdown Characteristics of Air, N₂ and CO₂ in a Sub-mm Gap

The present paper investigates the breakdown characteristics—breakdown voltage, with breakdown occurring on the rising edge of the applied HV impulses, and time to breakdown—for gases of significance that are present in the atmosphere: air, N₂ and CO₂. These breakdown characteristics have been obtained in a 100 µm gap between an HV needle and plane ground electrode, when stressed with sub-µs impulses of both polarities, with a rise time up to ~50 ns. The scaling relationships between the reduced breakdown field <i>E_tip</i>/<i>N</i> and the product of the gas number density and inter-electrode gap, <i>Nd</i>, were obtained for all tested gases over a wide range of <i>Nd</i> values, from ~10²⁰ m⁻² to ~10²⁵ m⁻². The breakdown field-time to breakdown characteristics obtained at different gas pressures are presented as scaling relationships of <i>E_tip</i>/<i>N</i>, <i>Nd</i>, and <i>Nt_br</i> for each gas, and compared with data from the literature.