Modeling and experimental comparison of pulsed-DC driven low-pressure plasma discharge in a metal tube

Abstract

High-voltage pulsed-DC can be used to deposit films on the inner surfaces of tubes and pipes. However, the characteristics of the plasma discharge in the tubes and mechanisms of film deposition are not well understood. In this study, a discharge is formed in a metal tube inserted with a coaxial anode by microsecond (μs) pulsed power to explore the influence of the pulse parameters on the plasma characteristics, including the temporal and spatial evolution near the tube walls experimentally and by simulation. The discharge waveform is monitored by a voltage-current probe to analyze the impact of the electrical characteristics on the plasma. The plasma properties are diagnosed by a Langmuir probe and numerically calculated by the fluid model. The source voltage and current jointly influence the plasma density and electron temperature, and secondary electron emission by energetic ion bombardment affects not only the distribution of electron density measured by the probe, but also the temporal distribution during the pulse-on and pulse-off time. The electron temperature varies conversely with the density from the plasma zone to the cathode suggesting the typical glow discharge in the pulsed-DC tube. Secondary electron emission is created at a higher discharge frequency, and a sustained plasma between pulse cycles appears to be produced at a higher frequency. The results impart information about the pulsed-DC driven plasma discharge at low pressure as well as the role energetic ions play on the cathode and elucidate the mechanisms of plasma deposition on the interior tube wall.