Bonn 2000 – scientific programme

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P: Plasmaphysik

P I: HV I

P I.1: Invited Talk

Monday, April 3, 2000, 14:40–15:20, HS IX

Mercury-Free High Pressure Discharge Lamps — •Matthias Born — Philips Research Labs, Weisshausstr. 2, D-52066 Aachen

The replacement of mercury by metallic zinc in high pressure discharges is investigated. The physical and chemical properties of mercury and zinc containing plasmas without and with addition of metal halides are discussed. Experiments are performed using envelopes of polycrystalline aluminaoxide (PCA) in order to establish buffer gas pressures of up to 40 bars. The stationary energy balance is solved for cylindrical discharge geometries. The basic transport data, i.e. electrical and thermal conductivites are determined, the latter including chemical chemical and translational contributions as well as heat transfer due to radiation diffusion. In addition, radiative transport calculations are based upon spectral line broadening due to resonance-, van der Waals- and Stark-effect. These parameters are derived from measurements of absolute and spectrally resolved side-on radiances of several atomic transitions. The replacement of mercury by zinc in metal halide systems, i.e. NaI-DyI3-TlI, results in nearly the same spectra and electrical field strengths whith only little variation of the discharge geometry. In the mercury-free case, increased radiative cooling is observed due to larger wall temperatures and particle densities.