Effect of Nitrogen Additive on Inhomogeneous Microwave Discharge in Hydrogen at Reduced Pressures

Abstract

The effect of a small nitrogen additive on a microwave discharge in hydrogen ignited near the antenna at a pressure of 1 Torr was studied by emission spectroscopy and visualization methods. It is shown that, in the presence of a nitrogen additive, the discharge shifts along the antenna toward the generator and the intensities of hydrogen spectral lines and bands near the antenna decrease. These results are qualitatively explained on the basis of the earlier 1D simulation of the discharge. The changes in the discharge parameters are caused by the replacement of the light \({\text{H}}_{3}^{ + }\) ion in hydrogen plasma with the heavy N₂H⁺ ion in a discharge in a hydrogen–nitrogen mixture. As a result, the rate of diffusive particle loss decreases, so that the discharge can exist in regions with a weaker microwave field.