The influence of a solid dielectric spacer on electron avalanches in nitrogen at atmospheric pressure

The temporal development of prebreakdown electron currents in nitrogen at atmospheric pressure and in a uniform electric field is investigated. These gap currents were determined by observation of changes in potential across a resistor in series with the one cm. long gap. While in previous work avalanche initiating electrons were released mainly through the use of spark gap radiation, here a short duration nitrogen laser pulse released electrons from the cathode. It has been found that the bridging of the gap by a solid, cylindrical insulating spacer alters the electron avalanche growth. A theoretical model is proposed to account for this previously unreported modification.