D. C. surface discharge characteristics in mach 2 rarefied airflow

The paper describes a study of an electrical discharge in a supersonic rarefied air flow. The discharge is created by applying negative DC potential difference between two electrodes flush mounted on the surface of a quartz flat plate placed in Mach 2 continuous airflow. The electrodes are arranged in spanwise direction. Two discharges are studied. In the first one, the negative potential is applied to the electrode placed close to the leading edge. In the second one the potential is applied to the electrode placed close to the trailing edge. Current-voltage characteristics, spectroscopic analyses, electrostatic probe and surface thermal measurement will be presented. Luminous emission pattern and potential measurements show that the plasma is similar to a low pressure tube discharge modified by a nonuniform density field of the flow. A comparison between current voltage characteristics of the upstream and downstream discharge shows the effect of the density field on the discharge. Thermal and spectroscopic measurements also show that the plasma induces a surface and volume heatings.