Diagnosis on the Plasma Parameters of an Atmospheric Pressure Uniform Discharge Operated in Open Air

A direct-current excited uniform discharge is initiated in a 3 cm argon gap in the open air. The negative slope of the voltage-current curve indicates that a normal glow discharge is realized. The diameter of the negative glow increases and that of the positive column decrease with increasing the discharge current. However, the current density is almost constant for the negative glow and it increases for the positive column with increasing the discharge current. The plasma parameters, such as the excited temperature, the vibrational temperature and the electron density, are calculated by optical emission spectroscopy method. Results show that the excited electron temperature keeps almost constant with increasing the discharge current, while both the vibrational temperature and the electron density increase with increasing the discharge current.