Impedance/frequency characteristics of glow discharges

Measurements of the small-signal impedance of glow-discharge tubes have been made over the frequency range 200c/s to 70Mc/s, for tubes having various cathode materials, electrode structures, gas pressures, gas fillings and direct-discharge currents. The results have been analysed using an extended form of a theory due to van Geel, developed by Benson and Chalmers, taking into account also the effects of the displacement current. Theory predicts that the impedance locus of a glow discharge is formed from several semicircular loci, each of which may be attributed to a delayed process in the discharge. The number of these loci, and the time constants associated with them, have been determined for tubes filled with pure neon, neon-argon mixtures and neon-krypton mixtures. The theory gives rise to an equivalent circuit for a glow discharge, and empirical formulas have been obtained for the various circuit elements.