Cathode-Sheath Model For Field Emission Sustained Atmospheric Pressure Discharges

The cathode-sheath region of a discharge in atmospheric pressure air with a flat copper cathode is numerically investigated by using a simple fluid model that takes into account non-local ionization. The effects of the cathode temperature are considered. Results are obtained in a wide current density range of 1-10(2)A/cm(2), which spans from normal glow discharge, through abnormal glow discharge, up to the early stages of the arcing transition. It is shown that the glow-to-arc transition arises from a field-emission instability at the cathode when the current density is larger than similar to 10 A/cm(2), i.e., when the cathode field exceeds a critical value of about 45 V/mu m for the conditions considered. It is also shown that the cathode temperature significantly influences the cathode-sheath region. The proposed model is validated by comparing the numerical results with available experimental data. Published under license by AIP Publishing.