Simulation and Experimental Verification of an Argon DC Glow Discharge

A coordinated experimental-simulation study was carried out to explore the relationship between plasma conditions and ion angular energy distributions incident on a DC glow discharge cathode. Langmuir probe measurements of the Electron Energy Distribution Functions (EEDF) validated a COMSOL simulation’s accuracy which confirmed the proper methodology for reproducing discharge dynamics. 1 The simulation was a coupling between COMSOL’s Plasma module and Boltzmann Equation, Two-Term Approximation module allowing for accurate calculations of the Townsend coefficients. Proper Townsend coefficients are necessary to represent the kinetics of DC discharges with low ionization fractions and species mobility that are highly dependent on the electric field, e.g., ions transiting the plasma sheath. The EEDFs were measured along the cathode dark space and negative glow regions using the Druyvesteyn method. 2 After the trend of EEDFs were validated, the model was expanded to extract ion angular energy distributions in conditions where measuring plasma properties became no longer feasible.