An economical supersonic CW HF laser testbed

Sentman, L. H.; Theodoropoulos, P.; Nguyen, Thanh-Phuong; Carroll, David L.

doi:10.2514/6.1989-1898

Cited by 5 publications

(8 citation statements)

References 2 publications

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“…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: 55%

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: Chapter 3 Experimental Apparatus and Proceduresmentioning

confidence: 55%

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

et al. 2004

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“…However, if stimulated process is fast enough compared to high vibration level deactivation rate, these lines could also surpass threshold and get lasing. Type II device's lasing lines distribute show nothing abnormal, they are P1(6)-P1(9), P2(5)-P2 (11) for Helium dilute, and P1(7)-P1(9), P2(6)-P2 (12) for Nitrogen dilute. Compared with type II device, supersonic array device's lower rotational quantum number transitions prevails higher ones and strongest transitions peaks with lower rotational quantum number.…”

Section: Spectra Distributionmentioning

confidence: 96%

“…We proposed that since high voltage dc-discharge tube's plenum pressure is much lower than arc and combustors, it's allowed realistic supersonic Mach number would be much lower too, hence, the difference between Helium and Nitrogen dilute will not be significant as high Mach number device. Sentman et al had transformed a Helios dc-discharge-driven device to supersonic array nozzle version, however, the power and efficiency was not increased as they expected, he assumed that F atom recombination increase should take the responsibility due to discharge tube pressure increase [11]. However, since F atom's recombination is a typical three body process and could only be significant under atmospheric pressure conditions, the assumption need further discussed.…”

Section: Introductionmentioning

confidence: 95%

Development of efficient nitrogen diluted discharge-driven HF CW chemical laser

Wang

Chen

Zhang

et al. 2013

XIX International Symposium on High-Power Laser Systems and Applications 2012

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Efficient Nitrogen diluted HF/DF laser with cryogenic adsorption provides a possible way to realize compact and relative high power mid-infrared laser system. Driven by only one dc-discharge tube, 117 Watt laser power, total e-o efficiency of 6.6% in HF case, and that stands four to five-fold increase had been achieved with Nitrogen dilute by careful designed supersonic nozzle array gain generator. Spectra, gain distribution, and chemiluminescence are further investigated to explain the enhancing mechanism.

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“…The oscillations were also observed in the UIUC supersonic cw chemical laser. 7 In response to these experiments, numerical simulations were performed and a mechanism was proposed. 5,6 The time-dependent oscillations of the laser power result from a competition between chemical pumping and radiative deactivation due to lasing.…”

Section: Previous Experiments and Calculationsmentioning

confidence: 99%

“…The flow rates for optimal performance of the SSL are: 7 He=0.0425 gm/s, O 2 =0.135 gm/s, SF 6 =1.54 gm/s, and H 2 =0.0535 gm/s. Initial testing 7 of the UIUC SSL demonstrated 40 ns oscillations for all scraper mirror slit widths ranging from 1 to 10 mm.…”

Section: Experimental Measurement Of Time-dependent Oscillationsmentioning

confidence: 99%

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

Mayer

Palla

Sentman

et al. 2005

36th AIAA Plasmadynamics and Lasers Conference

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dependent oscillations are the result of a competition between chemical pumping and radiative deactivation of the upper laser levels of HF due to lasing. The oscillations occur only if the medium is not strongly coupled to the optical fields diffractively or geometrically. Three new experiments were suggested to verify the proposed mechanism by varying the geometric and diffractive coupling of the optical field to the gain medium. 5,6 In this study, the proposed mechanism is tested by performing the three proposed experiments using the UIUC cw HF supersonic chemical laser. Time-dependent oscillations may decrease the average total power that may be extracted from high-energy chemical laser unstable resonators. The need to maximize performance of such systems motivates the study of the time-dependent oscillations.

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An economical supersonic CW HF laser testbed

Cited by 5 publications

References 2 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

Development of efficient nitrogen diluted discharge-driven HF CW chemical laser

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

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