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Detection of transient fluorine atoms

Description: A KrF eximer laser with a fluence of 50 mJ/cm/sup 2/ was used to photolyze either uranium hexafluoride or molecular fluorine, yielding a transient number density of fluorine atoms. The rise and decay of the atomic fluorine density was observed by transient absorption of a 25-..mu..m Pb-salt diode laser. To prevent the diode laser wavelength from drifting out of resonance with the atomic fluorine line, part of the beam was split off and sent through a microwave discharge fluorine atom cell. This allowed a wavelength modulation-feedback technique to be used to lock the diode laser wavelength onto the atomic line. The remaining diode laser beam was made collinear with the eximer laser beam using a LiF window with a 45/sup 0/ angle of incidence to reflect the infrared beam while transmitting most of the uv beam. Using this setup along with a transient digitizer to average between 100 and 200 transient absorption profiles, fluorine atom number densities on the order of 10/sup 14/ cm/sup -3/ in a 1.7 m pathlength were detected. The signals observed were about a factor of two less than expected from known photolysis and atomic fluorine absorption cross-sections. 2 refs., 4 figs.
Date: January 1, 1986
Creator: Loge, G.W.; Nereson, N. & Fry, H.A.
Partner: UNT Libraries Government Documents Department

Detonation chemistry apparatus experiments with nonreactive liquids, reactive liquids, and a reactive solid

Description: The detonation chemistry apparatus was designed to analyze the results of detonating small quantities of explosives or the results of rapidly mixing reactants. The diagnostics are rapid Schlieren photography of the emitted plume (up to 10 photographs per microsecond) and rapid mass spectroscopy (12 {micro}s per scan). The authors report here the results of a series of experiments with two liquids that do not react exothermically and another series with liquids that do react exothermically. They also report some experiments with a solid reactant, Teflon.
Date: May 1, 1996
Creator: Lyman, J.; Fry, H.; Breshears, D. & Romero, J.
Partner: UNT Libraries Government Documents Department

Use of multivariate regression for analysis of CO{sub 2} laser lidar data from long pathlengths in ambient atmosphere

Description: Until recently use of lasers for long path absorption measurements has relied on using differential absorption at two wavelengths to look for one species at a time in the atmosphere. With the advent of multi-line CO{sub 2} lasers it is now feasible to generate 30 to 40 lines in a rapid burst to look for spectra of all the chemical species that may be present. Measurements have been made under relatively constant meteorological conditions in a summertime desert environment with a multi-line tunable laser. Multivariate regression analysis of this data shows that the spectra can be accurately fit using a small number of spectral factors or eigenvectors of the time dependent spectral data matrix. The factors can be rationalized in terms of lidar system effects and atmospheric composition changes.
Date: August 1, 1997
Creator: Sander, R.K.; Quagliano, J.R. & Fry, H.
Partner: UNT Libraries Government Documents Department

Assessment of Infrared Remote Chemical Sensing Systems with Numeric Simulations

Description: A general approach to the evaluation of remote chemical sensors is described that can be used to provide evaluation of the chemical detection in a particular chemical scenario. It will be used to make comparisons of a CO{sub 2} laser differential absorption lidar sensor and a passive thermal FTIR sensor. The focus of the study will be to evaluate the advantage of the FTIR sensor's increased spectral coverage and number of frequency channels.
Date: November 1, 1998
Creator: Fry, H.; McVey, B. & Schmitt, M.
Partner: UNT Libraries Government Documents Department

Detonation reaction steps frozen by free expansion and analyzed by mass spectrometry

Description: Detonation reactions in small pellets of explosive are frozen by free expansion into a large vacuum chamber and analyzed by time-of-flight mass spectrometry. Sensitive explosives like PETN, RDX, and HMX show rapidly evolving reaction zones and mostly simple products like H[sub 2]O, CO, N[sub 2], and CO[sub 2]. Less sensitive explosives like TATB, HNS, and TNT show slower evolution of the reaction zone, and more complex products in addition to the simple ones seen in PETN. Isotopic substitution shows that the more complex products contain moderate amounts of NH[sub 3], HCN, NO, HNCO, and NO[sub 2]. Other observations include polymerization of aromatic explosive molecules, adducts to the explosive molecules, and explosive molecules with functional groups missing. The more complex products are reservoirs of unreleased energy that may affect performance.
Date: January 1, 1993
Creator: Greiner, N.R.; Fry, H.A.; Blais, N.C. & Engelke, R.P.
Partner: UNT Libraries Government Documents Department

Chemical identification using Bayesian model selection

Description: Remote detection and identification of chemicals in a scene is a challenging problem. We introduce an approach that uses some of the image's pixels to establish the background characteristics while other pixels represent the target for which we seek to identify all chemical species present. This leads to a generalized least squares problem in which we focus on 'subset selection' to identify the chemicals thought to be present. Bayesian model selection allows us to approximate the posterior probability that each chemical in the library is present by adding the posterior probabilities of all the subsets which include the chemical. We present results using realistic simulated data for the case with 1 to 5 chemicals present in each target and compare performance to a hybrid of forward and backward stepwise selection procedure using the F statistic.
Date: January 1, 2002
Creator: Burr, Tom; Fry, H. A. (Herbert A.); McVey, B. D. (Brian D.) & Sander, E. (Eric)
Partner: UNT Libraries Government Documents Department

Nucleation and condensation model development

Description: This is a final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The purpose of this project was to bring to maturity a theoretical and experimental capability of the Laboratory to perform basic research in nucleation and condensation of water vapor. This report provides a general description of this capability and summarizes specific work in two areas: development and use of a combustive flow facility (CFF) to measure water monomer depletion in a supersonic nozzle and nucleation pulse experiments for investigation of transport effects on water droplet growth dynamics. The later work was performed in collaboration with Dr. Wehrner Strey in Goettingen, Germany. Preliminary water absorption data from the CFF experiment are presented. The nucleation pulse data is described along with an analysis that shows under the condition of the experiment the growth rate of water droplets is limited by monomer diffusion.
Date: September 1, 1996
Creator: Fry, H.; Lyman, J.; Breshears, D.; Zerkle, D.; Wilson, C.; Hewitt, C. et al.
Partner: UNT Libraries Government Documents Department

A laboratory scale supersonic combustive flow system

Description: A laboratory scale supersonic flow system [Combustive Flow System (CFS)] which utilizes the gaseous products of methane-air and/or liquid fuel-air combustion has been assembled to provide a propulsion type exhaust flow field for various applications. Such applications include providing a testbed for the study of planar two-dimensional nozzle flow fields with chemistry, three-dimensional flow field mixing near the exit of rectangular nozzles, benchmarking the predictive capability of various computational fluid dynamic codes, and the development and testing of advanced diagnostic techniques. This paper will provide a detailed description of the flow system and data related to its operation.
Date: February 1, 1995
Creator: Sams, E. C.; Zerkle, D. K.; Fry, H. A. & Wantuck, P. J.
Partner: UNT Libraries Government Documents Department

Department of Defense/Department of Energy joint demilitarization technology demonstration program executive summary of Phase II demonstrations: The low-pressure rocket motor burns in X-Tunnel

Description: Three low-pressure rocket motor burn tests were executed in May--June 1997 time frame at the X-tunnel complex located on the Department of Energy's Nevada Test Site.
Date: December 1999
Creator: Bellow, B. W.; Moeller, A. E.; Steele, D.; Williams, S. M.; Heinle, R. L.; Pruneda, C. O. et al.
Partner: UNT Libraries Government Documents Department