Diagnosis of the DC Glow Discharge Plasma Generated Inside a Metallic Tube by Optical Emission Spectroscopy

Optical emission spectroscopy method was used to diagnose the normal dc glow discharge plasma generated inside a metallic tube. The active species in the plasma were identified. The electron excitation temperature in the plasma was determined by the Boltzmann plot method. The vibrational temperature of N-2 molecules in the plasma was determined by analyzing the emission spectrum lines of the N-2 second positive system (C-3 Pi(u)-> B-3 Pi(g).). The dependence of the electron excitation temperature and molecular vibrational temperature on the pressure was investigated. The experiment results show that in the Ar60%+N(2)40% glow discharge plasma at 20 Pa, the active species are the Ar atoms, Ar ions, second positive series of N-2 transitions and the first negative series of B-2 Pi(2)(u)-> X-2 Sigma(+)(g) transitons; the electron excitation temperature is (15 270+/-250) K, and the vibrational temperature of N-2 molecules is 3 290+/-100 K. The electron excitation temperature and molecular vibrational temperature decrease with increasing pressure. These results would give some valuable guide to the study on inner surface modification of metallic tubes.