EXPERIMENTAL CHARACTERISATION OF THE HIGH-PRESSURE METAL-HALIDE Na-Sc-Hg DISCHARGE Z. Miokovic 1 and D. Veza Physics Department, Faculty of Science, Uni-Zagreb, Bijenicka 32, HR Zagreb, Croatia 1 Faculty of Electrical Engineering, Uni-Osijek, K. Trpimira 2B, Osijek, Croatia MOTIVATION Better and more complete understanding of physics and chemistry of metal-halide discharge Metal-halide high intensity discharges play an increasing role as light sources Importance of atomic plasma parameters for modeling high-pressure discharges and optimization of metal-halide and alkali lamps An increasing interest for the plasma broadening of isolated non-hydrogenic lines of neutral atoms EXPERIMENT EXPERIMENT RESULTS RESULTS Fig.6.: Fig.6.: The comparison of our measured Stark shift d e of sodium 5 2 S 1/2 3 2 P 1/2,3/2 line at 615 nm, radiated from HP 400W metal-halide Na-Sc-Hg discharge with calculations by Griem. The 5 2 S 1/2 3 2 P 1/2,3/2 line was used as the calibration line to deliver values of electron densities N e at different currents through the discharge. -experiment, full line - theory (Griem, 1964) CONCLUSIONS Electron temperature is determined by Boltzmann plot method. Depending on discharge load and on the location in the discharge, the temperature is in the range of 6000 K K. Electron density is determined by measuring the Stark shift of the sodium 5 2 S 1/2 3 2 P 1/2, 3/2 spectral line. Electron densities are in the range of 7· ·10 16 cm -3. Line-shifts of the sodium 5 2 S 1/2 3 2 P 1/2, 3/2 transition show an almost linear dependence on the electron density. References [1] G. H. Reiling, JOSA 54, 532 (1964) [2]J. T. Dakin, T. H. Rautenberg, Jr. and E. M. Goldfield, J. Appl. Phys. 66 (9), 4074 (1989) [3]J. F. Waymounth, Electric Discharge Lamps (MIT, Cambridge, 1971) [4]H. Ywicker, in Plasma Diagnostics, p.214, ed. By W. Lochte-Holtgreven(Wiley, NY 1968) [5]W. L. Wiese, R. H. Huddleston, S. L. Leonard (Eds.), Plasma Diagnostics Techniques, Academic Press, NY, (1965) [6]H. R. Griem, Plasma Spectreoscopy, McGraw-Hill, New York (1964) Fig. 4.: Fig. 4.: The sodium 5 2 S 1/2 3 2 P 1/2,3/2 atomic lines measured from the HP 400W metal-halide Na-Sc-Hg discharge at the current of 3.4A. The upper part shows the sodium atomic lines measured from the low-pressure (LP) sodium spectral lamps (reference source, unshifted lines). The lower part represents the recorded spectral lines mesured, simultaneously, from the HP discharge and LP discharge. Abels inversion Fig. 3. Fig. 3. To determine the discharge temperature optically thin spectral lines wereused. The self-absorption test for spectral lines has been made by placing a concave spherical mirror behind the discharge to double the optical path length (Fig.1.). The correction for self-absorption is calculated by [5]. The solid line represents the measured line profile I 1 ( ) with single plasma length, and the dotted line represents the measured line profile I 2 ( ) with double plasma length. To obtain the line profile for optically thin case the measured profile I 1 ( ) is multiplied by the correction factor K. The dashed line is the corrected line profile I 1 C ( ). Fig. 6. Fig. 6. The electron densities are shown as a function of the current through the discharge. The electron densities show approximately a linear dependence on the discharge current. Fig. 5. The emission coefficients for the center of the discharge, of optically thin scandium spectral lines, were introduced into the Boltzmanns plot. From the slope of the regression line the electron temperature was deduced ( full line ). Dotted line - the interval of confidence according to statistical analysis. Fig. 1. Experimental arangement : LPL-low pressure lamp;HPL-high pressurelamp; R-folding mirror; L-lens; F-cut of filter; T-translator; SM-spherical mirror; M-monochromator; PMT-photomultiplier;A/D - analog-to-digital converter; PC-personal computer Fig. 2. Emission spectroscopy technique was used to measure the discharge temperature and densities of radiating atoms [3, 4]. The lateral intensity distribution, emitted by axially symmetrical plasma source, is measured. The radial intensity distribution is calculated using Abel inversion technique. The calibration of the system response has been made using a tungsten ribbon lamp.