The Influence of Gas Pressure on the H[sub α] Line Shape in the Gap of Dielectric Barrier Discharge Generated in Helium—Hydrogen Gas Mixtures

Abstract

In a gas mixture consisting of 99.5% of helium and 0.5% of molecular hydrogen, dielectric barrier discharges are generated by applying AC voltage to two electrodes, deposited on the outward surfaces of the ceramic plates. The two ceramic plates made of BaTiO3 form a slit-like discharge gap of 0.5 mm (distance between the inward ceramic surfaces). The radiation of the hydrogen Hα spectral line emitted from this gas gap is studied, applying gas pressures from 4 kPa to 60 kPa. The Hα line shapes emitted from this gap are measured with spectral and spatial resolution (in the direction perpendicular to the ceramic surface). The light detection system, equipped with a chopper (synchronized with the feeding voltage) allows light polarization sensitive measurements to be performed. The observed large broadening of the Hα profile is attributed mainly to the linear Stark effect. On the basis of analyzed Hα line shapes the electric field strengths in the gas gap at different pressures are determined.