The Low Frequency Impedance of the Cathode Fall Region†

Tho radio frequency impedance of a gas discharge is derived in terms of the plasma parameters introduced in an earlier paper (Severin 1963). As this frequency region is centred around the ion plasma frequency, it is especially of interest for the study of the ionic properties of the cathode fall region. It is shown that the modulated electron current, the a.c. component of tho ion donsity times d.c. velocity current, and the vacuum displacement current are the pertinent currents flowing in this frequency region. A resonance frequency is shown to be correlated to the transit time t.