Pulsed glow discharge for surface treatment

The transition of high-current glow to an arc and the energy dissipated on the glow phase caused by static breakdown in uniform-field gaps of up to 2 cm has been investigated in dry-air at gas pressures of 1–20 Torr. A low inductance capacitor of 1.89µF and a discharge apparatus with a co-axial configuration were used to produce a transient glow discharge with a current in excess of 400 A. Results showed that the high-current glow discharge occurred at a cathode current density of 3.2 A/cm², which is almost two orders larger than the predicted value from Cu-air normal glow data of jn=240×10⁻⁶ p² [A/cm²]. The transition from the glow to an arc starts to develop in the discharge region near the cathode. The energies dissipated in the discharge or in the cathode fall region during the glow phase depend on the gas pressure and/or the gap length. However, the dissipated energy density in the cathode fall region during the glow phase is almost constant with the gas pressure and the gap length, with a value of 0.035 J/cm³ used in the experiment.