[NWP.019] Radial Cataphoresis in Hg-Ar Fluorescent Lamp Discharges at High Power Density

Radial cataphoresis is a process in which the lower ionization potential atoms (Hg) are preferentially ionized and expelled from a multi-component (Hg-Ar) discharge. This process is important at high power densities which occur in some types of fluorescent lamps (e.g. the electrodeless Endura/Icetron lamp developed at Osram Sylvanic Inc.). Recent attempts to reconcile extensive absolute measurements on Icetron lamp discharges with self-consistent numerical models were only partially successful [2]. Radial catphoresis as well as some other high power density phenomena need to be re-examined. We have set up an axial absorption experiment at 185 nm on the ground level Hg atoms in an operating Icetron lamp. The High Sensitivity Absorption Spectroscopy (HSAS) facility at the Synchrotron Radiation Center in Stoughton WI is used in this study. The HSAS facility provides an intense synchrotron radiation continuum, very high spectral resolving powers from a 3 m focal length vacuum echelle spectrometer, and superb S/N ratios from a CCD detector array. Preliminary results will bepresented and discussed. [1] Supported by the NSF amp; USHIO Inc. Experimental lamp provided by OSRAM-SYLVANIA Inc. [2] J. J. Curry, G. G. Lister, J. E. Lawler, J. Phys. D: Appl. Phys. 35, 2945 (2002) Experimental Lamp Experimental lamp has two flat HIGH QUALITY Suprasil windows at the end of one arm. No phosphor Ar 40Pa(300mTorr) + Liquid Hg Hg pressure is controlled by tip temperature. 36.8 cm SR BEAM OUTLET WINDOW INLET WINDOW To SPECTROMETER