Discrepancies reported in the literature between numerical predictions and experimental measurements in low-pressure Hg discharges at high current densities are considered. A one-dimensional fluid model and recent spectroscopic and Langmuir probe measurements are combined in a semi-empirical way to individually examine components of the positive column power balance and the discharge conductivity. At a Hg vapor pressure of 0.81 Pa (6.1 mtorr) and a current density of 300 mA/cm2, previous discrepancies in the power balance and discharge conductivity are simultaneously resolved by assuming a higher electron density than measured experimentally. The importance of radial cataphoresis under these conditions, particularly with regard to radiation transport, is highlighted. The magnitude of radial cataphoresis under the moreextreme conditions of lower Hg vapor pressures and/or higher current densities is not fully understood. This work is of particular interest for the design of electrodeless fluorescent lamps operating at high current densities.
Citation: Journal of Physics D-Applied Physics
Pub Type: Journals
electrodeless discharge, fluorescent lamp, Hg discharge, light source, low-pressure discharge, optical spectroscopy, plasma, plasma model, positive column