Time-resolved measurements of the gas temperature in a H2/CH4 medium pressure microwave 915 MHz pulsed plasma

Experimental measurements of the time variation of gas temperature in a non-equilibrium hydrogen-methane microwave plasma operating at medium pressure and under pulsed mode are presented. The hydrogen plasma is created using a 915 MHz microwave generator at an input microwave power up to 17 kW and the gas temperature is determined from the rotational distribution of the G (1)Sigma(g)(+) excited state of H-2 (T(G)). In continuous discharge, the rotational temperature T(G) of H-2 (G(1)Sigma(g)(+)) is found to be nearly equal to the gas temperature determined from rotational distribution of the a (3)Pi(u) metastable state Of C-2 molecule obtained from absorption spectroscopy. The time evolution of H-2(G (1)Sigma(g)(+)) rotational distribution in pulsed discharges reaches a Boltzmann equilibrium only 100 mus after the beginning of the pulse. Variations of the T(G) in-pulse value as a function of pressure, volumetric power density and gas velocity is studied.