Experimental study of continuous wave hydrogen-fluoride chemical laser overtone performance

Carroll, David L.; Sentman, L. H.; Theodoropoulos, P.; Waldo, R.; Gordon, Shawn J.

doi:10.2514/3.11605

Cited by 13 publications

(5 citation statements)

References 7 publications

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“…This is done by altering the dissociation fraction of the F atom precursor molecule (SF^, F^, etc.) xmtil the model agrees with the experimental data (Carroll et al 1993;Sentman et al 1987). …”

Section: Previous Investigationssupporting

confidence: 78%

“…The laser nozzle design and experimental conditions are very similar to those of Sentman and co-workers (Carroll et al 1993;Sentman et al 1989b). The two most important differences are that in this research a slit nozzle rather than a nozzle bank is used, and the discharge used 20% Fa in helium rather than SFe + O2 as the F atom source.…”

Section: Chapter 3 Experimental Apparatus and Proceduresmentioning

confidence: 56%

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Spatially resolved sub-Doppler overtone gain measurements on a small-scale supersonic HF laser

et al. 2004

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Public reporting burden for this collection of information te Bstimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information. The overtone gain of a small-scale HF laser was measured using a sub-Doppler tunable diode laser system. Two-dimensional spatially resolved small signal gain and temperature maps were generated, which show a highly inhomogeneous gain medium indicating the dominant role that mixing of the fuel and oxidizer streams has in HF laser performance. The measured gain and temperature data were analyzed with the aid of a two-dimensional computational fluid dynamics code. To reduce uncertainty of important modeling input parameters, novel measurements of reactant concentration, flow velocity and gain length were made. Results show that reactant mixing mechanisms such as turbulence and large-scale vortex structures have a large effect on the gain averaged over a vertical profile while kinetic rate mechanisms such as reaction rate constants and reactant concentration have a greater effect on the maximum system gain. Overtone gain data measured while operating the laser saturated on the fundamental transitions are compared with fundamental lasing output spectra. In all cases, the data are consistent with an equilibrium rotational distribution.

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Section: Previous Investigationssupporting

confidence: 78%

Section: Chapter 3 Experimental Apparatus and Proceduresmentioning

confidence: 56%

Spatially resolved sub-Doppler overtone gain measurements on a small-scale supersonic HF laser

et al. 2004

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“…The rebaselined ORNECL-UR accurately predicts trends in total outcoupled power, oscillation period, and oscillation amplitudes as n p and N F were varied, but ORNECL-UR did not accurately predict the magnitude of the amplitude modulation. Since ORNECL was originally baselined to the vertically averaged measured zero power gain distributions in the UIUC SSL, 11,12 these vertically averaged gains may result in the calculated gains extending too far downstream. The ORNECL-UR under prediction of the magnitude of the amplitude of the time-dependent oscillations in SSL unstable resonators indicates the baselining to the zero power gain data should be revisited.…”

Section: Discussionmentioning

confidence: 99%

“…All cases were simulated using the 8.5% SF 6 dissociation which was determined by matching ORNECL calculations with zero power gain data for the UIUC supersonic laser. 11,12 ORNECL-UR calculations are listed in Table 1. ORNECL-UR was rebaselined 10 to correctly predict total outcoupled power for the M=2, L=100 cm X C =5 mm case (Case 2). The rebaselining was achieved by adjusting the percent dissociation of SF 6 in the arcs from 8.5% to 6.3% and by recalculating the fluid profiles.…”

Section: Simulation Of Resonator Geometries To Check the Proposedmentioning

confidence: 99%

Simulation of Time-Dependent Oscillations in a cw HF Chemical Laser Confocal Unstable Resonator

Palla

Sentman

Carroll

2005

36th AIAA Plasmadynamics and Lasers Conference

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“…until the model agrees with the experimental data. 18,19 Given the chemical and physical complexity of a typical HF laser, this technique can result in erroneous conclusions. An independent check upon the F atom concentration is needed.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen fluoride overtone laser: experimental methods of characterization

Wisniewski

Hewett

Manke

et al. 2004

High-Power Laser Ablation V

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The uncertainty in both the fluorine atom concentration and the gain length has inhibited the development of accurate and device independent models of HF overtone lasers. Furthermore, previous methods of measuring the small signal gain were cumbersome and could not easily generate spatial maps of the gain in the cavity. Experimental techniques have been developed to directly measure the concentration of fluorine atoms, the gain length and the small signal gain in a hydrogen fluoride 5 cm slit nozzle laser. A gas phase titration technique was utilized to measure the fluorine atom concentration using HCl as the titrant. The gain length was measured using a pitot probe to locate the interface of the primary flow with the high Mach number shroud flows. A tunable diode laser was utilized to perform small signal gain measurements on HF overtone (v=2 0) transitions.

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Experimental study of continuous wave hydrogen-fluoride chemical laser overtone performance

Cited by 13 publications

References 7 publications

Spatially resolved sub-Doppler overtone gain measurements on a small-scale supersonic HF laser

Spatially resolved sub-Doppler overtone gain measurements on a small-scale supersonic HF laser

Simulation of Time-Dependent Oscillations in a cw HF Chemical Laser Confocal Unstable Resonator

Hydrogen fluoride overtone laser: experimental methods of characterization

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