Investigation of RF and DC plasma electron sources for material processing applications

Abstract

This work presents the design, development and experimental results obtained from an RF plasma cathode Electron Beam (EB) gun for material processing applications. EB currents of up to 38 mA at –60 kV were extracted and correlated to Optical Emission Spectroscopy (OES) measurements. OES measurements and Argon II ratios were used to compare hollow and flat electrode designs as well as to examine changes in other key plasma parameters (i.e. plasma pressure and excitation power). The spectroscopic measurements and Argon II ratios indicated a higher ionization rate for the hollow electrode geometries and plasma parameters that generated larger EB currents (i.e. higher excitation power and lower pressure). The RF plasma cathode gun was compared to a DC plasma cathode gun. The DC plasma cathode produced larger currents than the RF plasma chamber. This result agreed with the OES measurements, which showed a higher ionisation in the DC plasma.