EXPERIMENTAL CHARACTERISATION OF THE

1
EXPERIMENTAL CHARACTERISATION OF THE
HIGH-PRESSURE METAL-HALIDE Na-Sc-Hg
DISCHARGE Z. Miokovic1 and D. Veza Physics
Department, Faculty of Science, Uni-Zagreb,
Bijenicka 32, HR-10002 Zagreb, Croatia
(veza_at_phy.hr) 1Faculty of Electrical Engineering,
Uni-Osijek, K. Trpimira 2B, 31000 Osijek, Croatia
(zeljka_at_etfos.hr)

• 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
Abels inversion
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.
Fig. 4. The sodium 52S1/2 ? 32P1/2,3/2 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.
Fig. 1. Experimental arangement LPL-low
pressure lampHPL-high pressurelamp R-folding
mirror L-lens F-cut of filter T-translator
SM-spherical mirror M-monochromator
PMT-photomultiplierA/D - analog-to-digital
converter PC-personal computer
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 I1(?) with single plasma
length, and the dotted line represents the
measured line profile I2(?) with double plasma
length. To obtain the line profile for optically
thin case the measured profile I1(?) is
multiplied by the correction factor K?. The
dashed line is the corrected line profile I1C(?).
RESULTS
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.6. The comparison of our measured Stark
shift de of sodium 52S1/2 ? 32P1/2,3/2 line at
615 nm, radiated from HP 400W metal-halide
Na-Sc-Hg discharge with calculations by Griem.
The 52S1/2? 32P1/2,3/2 line was used as the
calibration line to deliver values of electron
densities Ne 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 - 8000 K.
• Electron density is determined by measuring the
  Stark shift of the sodium 5 2S1/2 ? 3 2P1/2, 3/2
  spectral line. Electron densities are in the
  range of 71015 - 1.5 1016 cm-3.
• Line-shifts of the sodium 5 2S1/2 ? 3 2P1/2, 3/2
  transition show an almost linear dependence on
  the electron density.

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.
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)