Hollow cathode discharges (HCDs) have found a wide variety of applications for trace elemental analysis with the use of spectroscopic techniques such as atomic emission spectroscopy (AES), atomic absorption spectroscopy (AAS), and atomic fluorescence spectroscopy (AFS). In AES, the emission intensity output: of an HCD is rather limited compared to the emission intensity output of other electrical discharges. There are numerous ways by which the emission signal in HCDs can be increased. These ways include the application of external fields such as microwaves, radio-frequency, or magnetic fields. Reducing the diameter of the hollow to <2 mm was observed to give a substantial enhancement in the emission intensity, and such a discharge is referred to as a microcavity HCD.
A. R. Raghani, B. W. Smith, and J. D. Winefordner, "Spectroscopic Evaluation of a Miniature Microcavity Cylindrical Magnetron Source for Atomic Emission Spectroscopy," Appl. Spectrosc. 50, 417-420 (1996)