A study of radial cataphoresis and ion densities in high power density Hg-Ar discharges

A synchrotron radiation absorption experiment was used to measure the absolute density of ground level Hg atoms and Hg+ ions in Hg-Ar discharge plasmas at high power densities. Ion densities from this experiment were tested using microwave interferometry and compared with Langmuir probe measurements of the electron density. Radial cataphoresis was observed in this experiment and compared with model predictions. The agreement was satisfactory between the experiment and model. The role of cataphoresis in the power balance of Hg-Ar plasmas was further explored in the research described in the companion paper (Lister et al. 2004 J. Phys. D: Appl. Phys. 37: 3099-3106)