Evaluation of real-time non-invasive diagnostic tools for the monitoring of a pilot scale atmospheric pressure plasma system

A set of real-time non-invasive multivariate analysis tools were evaluated using LabVIEW software for the process monitoring of an atmospheric pressure plasma system. During system operation, it was observed that the optical and electrical properties are subject to a deterministic jitter effect caused by momentary changes in the discharge characteristics. This temporal jitter in the voltage, current and frequency of the applied power to an atmospheric pressure plasma was monitored to assess the plasma processing conditions. Electrical diagnostic tools were used to determine the transition of the plasma from the primary glow mode to the secondary glow mode and were correlated with photo diode (PD) analysis of the plasma. Intensified charge-coupled device (ICCD) imaging of the plasma was also used to distinguish between glow and Townsend discharge properties at low applied powers (400 W). The electrical observations were recorded in real time, plotted on a principal component analysis (PCA) loading plot and analysed using non-parametric cluster analysis (NPCA). It was observed from the plotted electrical parameters that data clusters were formed which relate to both the geometry of the atmospheric plasma chambers and the mode of plasma operation. The development of these tools facilitates real-time analysis of this reel-to-reel atmospheric pressure plasma processing system.