Dozias Sebastien

The propagation velocity modification of μs helium plasma gun (PG) discharge with nitrogen gas admixture in the helium buffer is studied in relation with ionization front imaging and helium-nitrogen plasma features. From 0,1 % to 0,8 % of N2, the ionization front is faster, more extended and with strong luminous intensity, compared to the high purity helium. The velocity has an optimum, for approximately 0,3 % of N2. Above 0,3 %, the velocity is progressively slowing down, and finally gets slower than the pure helium case above 0,9 %. The velocity evolution may be linked with kinetic and energy transfer predominantly on N2+ or N2 according to the increase of N2 %. Consequently, a local reinforcement of electric field in the front of the discharge is suspected for low N2 percentage, involving velocity increase of the discharge.