Modelling of the homogeneous barrier discharge in helium at atmospheric pressure

Numerical calculations of spatio-temporal characteristics of the homogeneous barrier discharge in helium are performed by means of a one-dimensional fluid model. The influence of the elementary processes on the discharge behaviour is studied by variation of the corresponding rate constants. The simulation and the analytical interpretation are carried out for two basic modes of the homogeneous barrier discharge, i.e. the Townsend and glow modes. The Townsend discharge is characterized by the absence of quasineutral plasma; several current peaks may occur during the half-cycle. The oscillations of the current are caused by a lag between the ion production nearby the anode and the subsequent ion-electron emission on the cathode. The specificity of the glow discharge is the development of a cathode region and a positive column during the breakdown, as well as the presence of quasineutral plasma in subsequent phases. The positive column occurs because the shielding of the external field by the plasma is not instantaneous. The dependence of the discharge behaviour on the external parameters, such as the amplitude and frequency of the applied voltage, discharge gap width, and thickness of dielectric barriers, is analysed. The mode of the discharge is governed mostly by the gap width and barrier thickness and depends weakly on the amplitude and frequency of the applied voltage. As the barriers are thin and the discharge gap is sufficiently wide, the glow mode occurs; otherwise, the discharge is Townsend.