Paper PS-TuP11
Electron Beam Generated Produced Plasmas Produced in Oxygen: Measurements and Simulations

Tuesday, October 22, 2019, 6:30 pm, Room Union Station B

The U.S. Naval Research Laboratory (NRL) has developed a processing system based on an electron beam-generated plasma. Unlike conventional discharges produced by electric fields (DC, RF, microwave, etc.), ionization is driven by a high-energy (1-3 keV) electron beam, an approach that can yield very different plasma properties than conventional plasma processing systems. Electron beam-generated plasmas are broadly characterized by high charged particle densities (10¹⁰- 10¹² cm^-3), low electron temperatures (0.3 - 1.0 eV), and in reactive gas backgrounds, a relatively low radical production rate compared to discharges. When produced in oxygen backgrounds, this combination of features leads to a surprisingly large density of O⁺ ions. In this work, we combine plasma diagnostics and modeling to characterize the spatial evolution of electron beam generated plasmas produced in oxygen as a function of operating parameters such as beam energy, beam current and pressure. Measurements of ion fluxes at adjacent surfaces indicate the large O⁺ ion densities can lead to O⁺/O₂⁺ flux ratios that far exceed one. The modeling results capture salient features of the plasma and provide a better understanding of plasma kinetics that lead to the measured ion flux ratios. This work is partially supported by the Naval Research Laboratory base program.