Influence of impurities on the uniform atmospheric-pressure discharge in helium

The influence of small nitrogen impurities on the uniform barrier discharge at atmospheric pressure in helium is investigated by numerical simulation with a one-dimensional fluid model. The simulation results show that in different discharge modes the influence of impurities is completely different. For glow discharge, small impurities result in the breakdown voltage dropping and thus cause the decrease in charged particle densities and discharge current density. In the case of Townsend discharge, nitrogen impurities can lead to the increase of charged particle densities and discharge current density, and even the change of discharge mode, but do not have a distinct impact on the breakdown voltage. (C) 2005 American Institute of Physics.