Measurement of the first Townsend's ionization coefficient for atmospheric pressure neon by a dielectric barrier discharge

Fast photography and optical emission spectroscopy are implemented in a 5 mm neon gap dielectric barrier discharge (DBD) at atmospheric pressure with quartz glass used as the dielectric layer. Results show that it starts with a Townsend discharge and ends at a sub-normal glow discharge in neon DBD. Based on the Townsend discharge, the first ionization coefficient of neon is measured. The measurements are consistent with those at low pressure. Optical emission spectroscopy indicates that the spectra are mainly composed of atomic lines of neon, molecular bands and molecular ion bands originating from inevitable gas impurities (mainly nitrogen). Moreover, spectral lines emitted from atomic neon corresponding to the transitions (2p⁵ 3p → 2p⁵ 3s) are predominant. Although the second positive system of N₂(C³Π_u → B³Π_g) is observed, their intensities are too weak compared with neon's spectrum. The molecular nitrogen ion line of 391.4 nm is observed. It reveals that Penning ionization between high energy neon excited states and the inevitable gas impurities plays an important role in the value of the α coefficient.