Partial EEDF analysis and electron diagnostics of atmospheric-pressure argon and argon–helium DBD plasma
Thijs van der Gaag, Atsushi Nezu, Hiroshi Akatsuka
Abstract
Abstract Partial arbitrary electron energy distribution function (EEDF) results for cold atmospheric-pressure plasma are reported. The EEDF is obtained using the visible bremsstrahlung inversion (VBI) method. This machine learning method requires only optical emission spectroscopy (OES) measurement and a momentum transfer cross section to determine a partial EEDF. Numerical EEDF of a pure-argon dielectric barrier discharge dataset with changing peak-to-peak voltage and a helium–argon discharge with changing mixture ratio are reported. Resemblance between the numerical EEDF and a two-temperature Maxwell distribution is observed and a simplified three-point numerical EEDF is obtained. The electron temperature and relative electron number density for the bulk and high-energy electron populations are measured. The bulk electron temperature was consistently 0.3 eV. For pure argon, the high-energy electron temperature decreased exponentially from 3 to 2.2 eV with increasing peak-to-peak voltage from 3.6 to 6.3 kV. For the helium–argon dataset, the high-energy electron temperature decreased linearly from 4.2 to 2.2 eV with increasing argon fraction 25%–100%. From an OES measurement, the arbitrary EEDF can be observed by utilization of the VBI method. Based on this numerical EEDF, appropriate assumptions can be applied to simplify the quantification of electron diagnostics.