Characteristics of a high-current transient glow discharge in dry air

The transition of a high-current glow to an are and the energy dissipation during the glow phase have been investigated in dry air by static breakdown. The measurements have been made for uniform-field gaps up to 2 cm at gas pressures of 1-20 Torr. A low-inductance capacitor of 1.89 mu F and a discharge circuit with a coaxial system were used to produce a transient glow discharge with a current in excess of 400 A. The experimental results showed that the high-current glow discharge occurred at a cathode current density of 3.2 A cm(-2), which is almost two orders larger than the value deduced from the formula for Cu-air normal glow; j(n) = 240 x 10(-6) p(2), where j(n) and p are the current density and gas pressure, respectively. The transition from the glow to an are starts to develop in the discharge legion near the cathode. The energies dissipated in the discharge or in the cathode fall region during the Slow phase depend on the gas pressure and/or the electrode separation. However, the dissipated energy density in the cathode fall region during the glow phase is independent of the gas pressure and the electrode separation, and is approximately 0.035 J cm(-3) in the present experiment.