61st Annual Gaseous Electronics Conference
Volume 53, Number 10
Monday–Friday, October 13–17, 2008;
Dallas, Texas
Session RR2: Lighting Plasmas
1:30 PM–3:00 PM,
Thursday, October 16, 2008
Room: Salon A-D
Chair: D. Leonhardt, Fusion UV Systems, Inc.
Abstract ID: BAPS.2008.GEC.RR2.3
Abstract: RR2.00003 : Continuum Processes in High and Ultra High Pressure Lamps*
2:00 PM–2:30 PM
Preview Abstract
Abstract
Author:
J.E. Lawler
(University of Wisconsin)
The growing use of Ultra High Pressure (UHP) lamps for projection
applications has motivated studies of thermal or LTE Hg plasmas in a
peculiar region of parameter space. These UHP lamps, which are
now commonly
found in conference room projectors and large screen TVs, operate
with Hg
pressures $>$ 200 bar, electron densities $\sim $1.0E18 / cc, and
power
densities $>$ 1.0E5 W/cc. Such lamps were developed to couple the
maximum
amount of light into small etendue LCD projection systems. Unlike
most other
plasmas in similar parts of parameter space, the plasmas in UHP
lamps are
steady-state. A greater variety of diagnostic techniques and more
accurate
measurements are possible in UHP lamp plasmas. Continuum
processes are much
more important in both the opacity and power balance of UHP lamps
than they
are in typical ($<$ 20 bar) High Intensity Discharge (HID) lamps.
Electron +
Hg atom bremstrahlung dominates ($\sim $90{\%}) the near IR
emission from
UHP lamps [1]. Quasi-molecular absorption at $>$ 200 bar yields
substantial
opacity and results in minimal UV emission from UHP lamps [2, 3].
There are
additional physics issues in the 200 bar to 1 kbar range: e.g.
(1) spectral
line broadening of the few remaining Hg transitions including the
breakdown
of the single perturber approximation of line broadening theory,
(2) free
electron continuum processes including the breakdown of the
binary collision
approximation, and (3) the effect of strong coupling of the
plasma on
radiative processes. A more quantitative understanding of
electron + Hg atom
bremsstrahlung in UHP lamps has resulted in a better
understanding of near
IR losses from widely used, lower pressure metal-halide HID lamps.
\newline
[1] Lawler JE, Koerber A, and Weichmann U 2005 J. Phys. D: Appl.
Phys. 38,
3071.
\newline
[2] Wharmby D 2008 J. Phys. D: Appl. Phys. in press.
\newline
[3] Kato M, Kane J, and Lawler JE 2008 J. Phys. D: Appl. Phys.
submitted.
*Supported by NSF CTS 0613277.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2008.GEC.RR2.3