The power output of a black body solar-pumped laser as a function of time (computer graphic solutions) and under steady state conditions (analytic conditions); computer analyses of polymerization using lasers; and metallic sodium as a laser medium were studied

Fong, Z. S.

Harries, W. L.

English

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https://ntrs.nasa.gov/search.jsp?R=19850018895 2020-03-20T19:04:34+00:00Z
(N&S1 —CR-175801) THEORETICAL STUDIES 0 7 	 V85-27206
SOLAR-PUMPED LASERS PzogrQss Report, 16
Jul. 1984 — 15 Jan. 1985; (Old Dorinion
Univ., Norfolk, Va.) 4 p HC 1G2/fl F A01	 Unclas
CSCL 203 G3/36 15135
DEPARTMENT OF PHYSICS
SCHOOL OF SCIENCES AND HEALTH PROFESSIONS
OLD DOMINION UNIVERSITY
NORFOLK, VIRGINIA
Technical Report PTR 85-2
THEORETICAL STUDIES OF SOLAR-PUMPED LASERS
By
Wynford L. Harries, Principal Investigator
and
Zeng-Shevan Fong, Graduate Research Assistant
Progress Report
For the period July 16, 1984 to January 15, 1985
Prepared for the
National Aeronautics and Space 'Administration
Langley Research Center
Hampton, Virginia 23665
Under
Research Grant NSG 1568
W. E. Meador, Technical Monitor
Space Systems Division
Submitted by the
Old Dominion University Research Foundation
P.Q. Box 6369
Norfolk, Virginia 23508
January 1985
^I
_	 --------^--.F-
r	 i
THECRETICAL STUDIES OF SOLAR PUMPED LASERS
By
Wynford L. Harried and Zeng-Shevan Fong2
SUMMARY
The paper "Kinetic Modeling of an 18r Solar Pumped La yer," by W. L.
Harries and W, E. Meador, has appeared in Space Solar Power Review, Vol. 4,
pp 189-202, 1983. The paper was accepted in June 1983 but, due to delays at
Pergamnon Press, the issue did not appear until December 1984.
A paper "Criteria for the Evaluation and Comparison of Laser Solar
Energy Converter Systems," by W. L. Harries, was sut-mitted to the AIAA Jour-
nal of Propulsion and Power.
The work for the period July 1984 to January 1985 can be divided under
these headings:
1) Continued Investigations of Black-Body Solar Pumped Lasers;
2) Computer analyses of Polymerization using Lasers;
3) Investigations of metallic sodium as a laser medium.
INVESTIGATIONS OF BLACK-BODY SOLAR PUMPED LASERS
The report for January 1984 to July 1984 (PTR 84-4) had an analysis of
a CO2
 black-body pumped laser. The power output of the laser was esti-
lated both as a function of time (computer graphic solutions) and under
steady state conditions (analytic solutions).
	
A considerable amount of
experimental data on such lasers was available from the work of R. J. Insuik
and W. H. Christiansen, IEEE J. Quantum Electronics, QE-20, 622 (1984). In
'Eminent Professor, Department of Physics, Old Dominion University, Norfolk,
Virginia 23508.
2 Graduate Research Assistant, Department of Physics, Old Dominion Univer-
sity, Norfolk, Virginia 23508
i
k It
Aaddition, R. J. Insuik had also very kindly made available her Ph.D. thesis.
Our analysis had included the new effect of the heating of the gases which
filled the lowe r laser level.
Qualitative agreement had been obtained between theory and experiment
for steady output power versus gas pressure and different olack-body temper-
ature; however, the theory indicated much too high an output at low pres-
sures. The agreement between power output and black-body temperature was
fair, and the analysis also correctly showed a drop in power as the gas tem-
perature ii ,creased.	 There was lack of agreement between the analytical
results and the outputs for different gas mixtures of COy, He, Ar.
Hence, the analytical results were considered preliminary and tentative.
The analysis suffers the disadvantage that the rate coefficients and
absorption cross sections are not well known. 	 Diffusion to the walls had
been included already, and a new assumption was made that there was a finite
probability that a collision of a particle in the upper laser level with the
	 i
wall resulted in the particle being transferred to the lower laser level
CCZ (001) , COZ (100).	 This seemed to reduce the output at low pressures to
agree with the experiment. The effect of using larger values of the absorp-
tion cross section was tried. This had the effect, as had bean suggested by
Insuik, of absorption in the outer gas layers of the laser at higher gas
pressures. Despite improved agreement at the "standard pressure," however,
the effect of varying the gas ratios still showed a discrepancy between
theory and experiment. The investigation continues.
COMPUTER ANALYSES OF POLYMERIZATION USING LASERS
This investigation was strictly not part of studies of solar energy
2
11
conversion using lasers, but the techniques used in computer graphic solu-
tions of several time dependent simultaneous equations could tie immediately
applied, and were used in several instances. 	 i
INVESTIGATIONS OF METALLIC SODIUM AS A LASER MEDIUM
The possibility of using metallic vapors as laser media was still stud-
ied because such lasers would operate at high temperatures, and this would
reduce the weight of the radiator. Accordingly, experimental measurements
are being made of the absorptijn of visible light in sodium vapor to obtain
cross sections as functions of wavelength for the transitions X + A, X
B, and X - C. The experiments, performed in a heat pipe arrangement, are
done in a higher temperature regime than those found in the literature, and
are continuing.
ACKNOWLEDGEMENTS
i
The authors acknowledge useful discussions with Drs. Meador and Jalufka
of NASA Langley Research Center, with Ur. L. Zapata of Miami University,
Oxford, Ohio, and Ms. R. Insuik of the University of Washington, Seattle,
Washington.
in
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Theoretical studies of solar-pumped lasers

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