It has been shown that self-sustained normal dc atmospheric pressure glow discharge (APGD) in helium exists in a large range of current values from 100 µA to 10 A. The plasma of this discharge is weakly ionized (one thousandth part of a per cent) and is non-equilibrium. The plasma non-equilibrium degree in the positive column depends on the discharge current values. Parameters of the cathode region stay constant over the whole current range of normal APGD.

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It is shown that the cathode temperature has a significant influence on the properties of the cathode fall in a self-sustained, normal, dc, atmospheric pressure glow discharge in helium and, in particular, on the electric field distribution, the thickness of the cathode fall layer, the current density and the gas temperature. An increase in the cathode temperature leads to an increase in the gas temperature and cathode fall thickness, a decrease in the current density and a modification in the radial distribution of the electric field close to the cathode surface. A discussion based on a one-dimensional model of the cathode fall region including gas heating is presented.

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