Hollow Cathode Discharges: Analytical Applications

The low pressure glow discharges considered in this paper are the hollow cathode (Paschen), and the flat cathode (Grimm). Both discharges have similar voltage-current characteristics which are responsible for their radiation stability. The analytical sample is supplied to the discharge through a sputtering mechanism which provides a stable and non-selective source of particles. Some of the fundamental properties of the glow discharge and sputtering phenomena will be discussed, including the relation between the geometry of the discharge, and the nature and pressure of sustaining gas, and current, on the emission characteristics of the discharges. These will he followed by a description of the conventional instrumentation developed for analytical purposes using the hollow cathode and flat discharge. A description of the hollow cathode developed at the National Bureau of Standards (NBS) will follow. The techniques used for the introduction of various conductive and nonconductive materials into the discharge will be discussed. The use of these discharges will be illustrated with examples taken from the literature and from the measurements performed at NBS. The paper will conclude with a discussion of possible future developments of low pressure glow discharges. A collection of references to works on low pressure glow discharges, containing 690 entries, concludes this work.