Electrical and Optical Signal Analysis of Pulse Powered Glow Discharge System

Abstract

The electrical and optical signal waveforms of nitrogen/hydrogen glow discharges used for plasma nitriding process were recorded and analyzed. The shape of the discharge voltage and current signals is dependent on the process parameters, pulse plasma generator properties and cathode geometry. It has been found that the dynamic parameters of the electrical signal waveforms contain information related to the charged particles generation, which is relevant to the homogeneity of different gas discharge surface treatment processes. On the other hand, information related to the active species generation responsible for thermochemical processes at the cathode surface is stored in the optical emission waveforms. The generation and quenching of the active ingredients during the voltage pulses switch on and off influence the shape of the emitted light signals. From the optical signal analysis it was found that the thermochemical processes are influenced by the plasma generator properties such as pulse duty cycle, frequency, applied discharge voltage level and process parameters like working gas composition, operating temperature and pressure.