Corona discharge as a temperature probe of atmospheric air microwave plasma jet

We developed and tested a new method for temperature measurements of near-LTE air plasmas at atmospheric pressure. This method is specifically suitable for plasmas at relatively low gas temperature (800-1700 K) with no appropriate radiation for direct spectroscopic temperature measurements. Corona discharge producing cold non-equilibrium plasma is employed as a source of excitation and is placed into the microwave plasma jet. The gas temperature of the microwave plasma jet is determined as the rotational temperature of N2⁎ produced in the corona discharge. The corona probe temperature measurement was tested by the use of a thermocouple. We found a fairly good agreement between the two methods after correcting the thermocouple measured temperatures for radiative losses. The corona probe method can be generally applied to determine the temperature of the near-LTE plasmas and contrary to the thermocouple it can be used for higher plasma temperatures and is not affected by radiative losses and problems of interaction with the microwave plasma and electromagnetic fields.

► New method for temperature measurements of near-LTE atmospheric air plasmas developed. ► Suitable for plasmas with no radiation for direct emission spectroscopy measurements. ► Corona discharge put in the MW plasma excites N2-rotational temperature measurement. ► Comparison of corona probe and thermocouple temperatures showed fairly good agreement. ► Corona probe suitable also for higher temperatures and more reliable than thermocouple.