In a nitrogen plasma jet, atomic nitrogen is the longest lived radical species and, through recombination, gives rise to highly reactive excited nitrogen species. In this paper, the atomic nitrogen concentration in the effluent of a nitrogen-fed dielectric barrier discharge (DBD) is determined by using direct 2D imaging of the visible FPS emission. The relationship between radical production and the electrical characteristics of the discharge is assessed by making use of an electrical model which assumes only a part of the electrode area is discharged every half-cycle. For the pure nitrogen jet used here, the specific energy input per nitrogen atom is found to be 320 ± 20 eV atom-1, comparable to the specific energy for other atomic nitrogen sources in the literature. It is shown that the production efficiency of atomic nitrogen does not depend on the amplitude of the applied voltage of the DBD and any increase in radical production is due to an increase of the electrode area covered by the discharge, i.e. an increase in the number of microdischarges.
- dielectric barrier discharge
- electrical properties
- kinetic model
- optical emission spectroscopy