Dynamics of gas heating in a pulsed microwave nitrogen discharge at intermediate pressures

The time-resolved measurements of the rotational temperature in a pulsed microwave discharge in nitrogen in the range of pressures from 1 to 100 mbar are performed by means of the spectroscopic study of the rotational structure of the second positive system. The rotational temperature at the steady state ranges from 1000 to 3000 K depending upon the gas pressure. The equality between the rotational and gas temperatures is discussed. The time dependence of the temperature during the pulse is characterized by a fast (100 µs) heating time followed by saturation. The steady-state temperature at 100 mbar is lower than at 40 mbar. The results are analysed with the help of the heat balance equation, and the anomalous behaviour of the gas temperature at higher pressures is discussed. As the BaTiO 3 pellets are added inside the discharge, the gas temperature is reduced by half, which is caused by more effective gas cooling. Moreover, the pellets make it possible to obtain the discharge at pressures up to the atmospheric pressure.