Time resolved temperature measurements in a H-2 high power pulsed discharge

A hydrogene plasma is generated in a cavity by a short pulse (10 mu s), hig h peak power (2-8 kW) microwave discharge. The time evolution of rotational and kinetic temperature are compared. Both kinetic temperatures of atoms a nd molecules are determined by optical emission spectroscopy (Doppler broad ening). The medium is strongly in non equilibrium, particularly during the breakdown, at the beginning of the pulse, due to the existence of strong el ectric field; this electric field induces a stark splitting of the Balmer a lpha line. During the breakdown, the rotational distribution is far from th e Boltzmann law, and progressively reaches an equilibrium within 10 mu s. T he molecular temperature increases sharply from 300 to 900 K, at the beginn ing of the pulse but remains lower than the atomic temperature (1800 K). In order to explain these results, we check different possible mechanisms for the kinetic energy transfer to the neutrals.