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Description: Sensitive (0.15 ppm) and unambiguous detection of carbon monoxide is reported and a comparison of acoustically resonant and nonresonant detectors is given. The pressure dependence of the optoacoustic signal is discussed in the context of atmospheric absorption.
Date: October 1, 1977
Creator: Gerlach, R. & Amer, N.M.
Partner: UNT Libraries Government Documents Department

Experimental observation of resonance effects in intensely irradiated atomic clusters

Description: We have resolved the expansion of intensely irradiated atomic clusters on a femtosecond time scale. These data show evidence for resonant heating, similar to resonance absorption, in spherical cluster plasmas.
Date: July 10, 1998
Creator: Ditmire, T.; Komashko, A.; Perry, M. D.; Rubenchik, A. M. & Zweiback, J.
Partner: UNT Libraries Government Documents Department

High-T measurements in reflected shock waves of rate constants for D + CH3 and D + H2 : comparisons with theory.

Description: D-atom atomic resonance absorption spectrometric (ARAS) detection has been used to study the thermal decomposition of C{sub 2}D{sub 5}I to give C{sub 2}D{sub 5}-radicals in {approx}70% yield (924-1370 K). C{sub 2}D{sub 5} then decomposes to give C{sub 2}D{sub 4} + D effectively instantaneously on the time scale of the bimolecular kinetics experiments. The concurrent thermal decompositions of both C{sub 2}D{sub 5}I and CH{sub 3}I can then be used to prepare well-defined initial concentrations of both D-atoms and CH{sub 3}-radicals. Experiments were performed by observing absolute [D] depletion and [H] formation. The results were initially modeled with a 33 step mechanism; however, because of the high sensitivity for H- and/or D-detection, the mechanism could be reduced to four reactions, all of which are known except the exchange reaction, D + CH{sub 3} {yields} CH{sub 2}D + H. The rate constants were found to be temperature independent with k = (2.20 {+-} 0.22) x 10{sup -10} cm{sup 3} molecule{sup -1} s{sup -1} for 1294 {le} T {le} 1753 K. The present data have been combined with earlier lower temperature determinations, and the resultant database has been compared with unimolecular rate theory results. From theory, k = kk{sub {infinity}}<k{sub f{var_epsilon}}/(k{sub f{var_epsilon}} + k{sub f{var_epsilon}})> = k{sub {infinity}}F. Using the frequencies and structures given in Seakins et al. and Sutherland et al., we find F(300 K) is 0.928 (in good agreement with Seakins et al.), and at higher-T, F(1800 K) = 0.857. Klippenstein, Goergievski, and Harding find, from recent extensive theoretical calculations, values for F varying from 0.92 to 0.79 over the same T-range. Reliable values for the high-pressure limiting rate constant for methane dissociation at high-T can now be inferred from the present study.
Date: July 9, 2002
Creator: Michael, J. V.; Su, M.-C. & Sutherland, J. W.
Partner: UNT Libraries Government Documents Department

Thermal decomposition studies of halogenated organic compounds

Description: Thermal decomposition results for CCl{sub 4}, CHCl{sub 3}, CH{sub 2}Cl{sub 2}, CH{sub 3}Cl, C{sub 3}H{sub 3}Cl, CFCl{sub 3}, CF{sub 2}Cl{sub 2}, CF{sub 3}Cl, CF{sub 2}HCl, CF{sub 3}I, CH{sub 3}I, C{sub 2}H{sub 5}I, C{sub 6}H{sub 5}I, and CCl{sub 2}O are presented. The results were obtained by shock tube techniques coupled with optical spectroscopic detection of transient species formed from dissociation. The method is illustrated with the CH{sub 3}I (+ Kr) {yields} CH{sub 3} + I (+ Kr) reaction where decomposition was monitored using I-atomic resonance absorption spectrometry (ARAS). Modern unimolecular rate theoretical analysis has been carried out on the present cases, and the conclusions from these calculations are discussed. Lastly, the possible destruction of halo-organics by incineration is considered and some implications are discussed.
Date: June 1, 1997
Creator: Michael, J.V. & Kumaran, S.S.
Partner: UNT Libraries Government Documents Department

C{sub 2}D{sub 5}I dissociation and D + CH{sub 3} {yields} CH{sub 2}D + H at high temperature : implications to the high pressure rate constant for CH{sub 4} dissociation.

Description: The shock tube technique with H- and D-atom atomic resonance absorption spectrometry (ARAS) detection has been used to study the thermal decomposition of C{sub 2}D{sub 5}I and the reaction, CH{sub 3} + D'' CH{sub 2}D + H, (1) over the temperature ranges, 924-1370 K and 1294-1753 K, respectively. First-order rate constants for the thermal decomposition of C{sub 2}D{sub 5}I can be expressed by the Arrhenius equation, logk{sub C2D5I} = (10.397 {+-} 0.297) - (7700 {+-} 334 K)/T, giving k{sub C2D5I} = 2.49 x 10{sup 10} exp(-17729 K/T) s{sup -1}. The branching ratio between product channels, C{sub 2}D{sub 5} + I and C{sub 2}D{sub 4} + DI, was also determined. These results coupled with the fast decomposition of C{sub 2}D{sub 5} radicals were then used to specify [D]{sub t} in subsequent kinetics experiments with CH{sub 3} where [CH{sub 3}]{sub 0} was prepared from the concurrent thermal decomposition of CH{sub 3}I. Within experimental error, the rate constants for reaction (1) were found to be temperature independent with k{sub 1} = (2.20 {+-} 0.22) x 10{sup -10} cm{sup 3} molecule{sup -1} s{sup -1}. The present data have been combined with earlier lower temperature determinations and the joint database has been examined with unimolecular rate theory. The implications of the present study can be generalized to supply a reliable value for the high-pressure limiting rate constant for methane dissociation.
Date: December 13, 2001
Creator: Su, M.-C. & Michael, J. V.
Partner: UNT Libraries Government Documents Department

Critical Density Interaction Studies

Description: Experiments have been performed to study the propagation of intense laser pulses to high plasma densities. The issue of self-focusing and filamentation of the laser pulse as well as developing predictive capability of absorption processes and x-ray conversion efficiencies is important for numerous programs at the Laboratory, particularly Laser Program (Fast Ignitor and direct-drive ICF) and D&NT (radiography, high energy backlighters and laser cutting). Processes such as resonance absorption, profile modification, linear mode conversion, filamentation and stimulated Brillouin scattering can occur near the critical density and can have important effects on the coupling of laser light to solid targets. A combination of experiments have been used to study the propagation of laser light to high plasma densities and the interaction physics of intense laser pulses with solid targets. Nonparaxial fluid codes to study nonstationary behavior of filamentation and stimulated Brillouin scattering at high densities have also been developed as part of this project.
Date: February 14, 2001
Creator: Young, P; Baldis, H A; Cheung, P; Rozmus, W; Kruer, W; Wilks, S et al.
Partner: UNT Libraries Government Documents Department

Cavity resonance absorption in ultra-high bandwidth CRT deflection structure

Description: An improved ultra-high bandwidth helical coil deflection structure for a cathode ray tube is described comprising a first metal member having a bore therein, the metal walls of which form a first ground plane; a second metal member coaxially mounted in the bore of the first metal member and forming a second ground plane; a helical deflection coil coaxially mounted within the bore between the two ground planes; and a resistive load disposed in one end of the bore and electrically connected to the first and second ground planes, the resistive load having an impedance substantially equal to the characteristic impedance of the coaxial line formed by the two coaxial ground planes to inhibit cavity resonance in the structure within the ultra-high bandwidth of operation. Preferably, the resistive load comprises a carbon film on a surface of an end plug in one end of the bore.
Date: May 15, 1991
Creator: Dunham, M. E. & Hudson, C. L.
Partner: UNT Libraries Government Documents Department

Experimental test of resonant absorption theory. Progress report, July 1, 1978--September 30, 1978

Description: Engineering of the various components of the experiment is discussed, and the first experiments are described. In the last three months engineering has been virtually completed on all aspects of this experiment, and the various components of the apparatus have been successfully integrated and utilized.
Date: October 1, 1978
Creator: Yablonovitch, E
Partner: UNT Libraries Government Documents Department

Partial Safety Analysis for a Reduced Uranium Enrichment Core for the High Flux Isotope Reactor

Description: A computational model of the reactor core of the High Flux Isotope Rector (HFIR) was developed in order to analyze non-destructive accidents caused by transients during reactor operation. The reactor model was built for the latest version of the nuclear analysis software package called Program for the Analysis of Reactor Transients (PARET). Analyses performed with the model constructed were compared with previous data obtained with other tools in order to benchmark the code. Finally, the model was used to analyze the behavior of the reactor under transients using a different nuclear fuel with lower enrichment of uranium (LEU) than the fuel currently used, which has a high enrichment of uranium (HEU). The study shows that the presence of fertile isotopes in LEU fuel, which increases the neutron resonance absorption, reduces the impact of transients on the fuel and enhances the negative reactivity feedback, thus, within the limitations of this study, making LEU fuel appear to be a safe alternative fuel for the reactor core.
Date: April 1, 2009
Creator: Primm, Trent & Gehin, Jess C
Partner: UNT Libraries Government Documents Department

Manganese bath systematic effects in measurements of nu-bar and eta

Description: Measurements using the manganese bath technique are central to the discrepancy that has existed between measured values of $nu$-bar for $sup 252$Cf. Manganese bath measurements of $nu$-bar belong to the lower group of values, while the eta measurements are consistent with the higher $nu$-bar values. A three-part study was performed to see if the discrepancy could be explained by differences in manganese bath techniques: (1) A $sup 252$Cf source previously calibrated by De Volpi was calibrated in the MTR manganese bath; (2) The recommendations made by De Volpi for altering the MTR eta values were carefully considered; and (3) The results of the Monte Carlo calculation of the MTR experiments, carried out at Bettis Atomic Power Laboratory, were examined in detail. The study produced insignificant changes in the eta values. (6 tables) (auth)
Date: January 1, 1975
Creator: Smith, J.R.
Partner: UNT Libraries Government Documents Department

Experimental test of resonant absorption theory. Final report, January 1, 1978-December 31, 1979

Description: This experimental research has probed the nature of resonant absorption (RA) of laser light by laser-produced plasmas. The plasmas were created by optical breakdown of a shockfront produced in an electrothermal shock tube. This procedure allows the density structure of the plasma, and in particular, the orientation of the plasma critical-density surface, to be reproducibly formed from one shot to the next. Thus, for the first time, RA has been controllably and reproducibly studied in isolation from other plasma physics. The angular distribution of fast electrons emitted by RA and wavebreaking has been studied, and it is observed that the emission is directed in a narrow cone centered on the shockfront density-gradient vector, in agreement with the theory of wavebreaking.
Date: May 1, 1979
Creator: Yablonovitch, E
Partner: UNT Libraries Government Documents Department

Successive collision calculation of resonance absorption (AWBA Development Program)

Description: The successive collision method for calculating resonance absorption solves numerically the neutron slowing down problem in reactor lattices. A discrete energy mesh is used with cross sections taken from a Monte Carlo library. The major physical approximations used are isotropic scattering in both the laboratory and center-of-mass systems. This procedure is intended for day-to-day analysis calculations and has been incorporated into the current version of MUFT. The calculational model used for the analysis of the nuclear performance of LWBR includes this resonance absorption procedure. Test comparisons of results with RCPO1 give very good agreement.
Date: July 1, 1980
Creator: Schmidt, E. & Eisenhart, L.D.
Partner: UNT Libraries Government Documents Department

Fixed-wavelength R2PI/tandem mass spectrometry for mixture analysis in the quadrupole ion trap

Description: Many aromatic molecules have strong absorption bands in the uv which are rather broad at room temperature; the ionization potentials for many such polyatomics are also often less than 9 eV. Therefore, they can be ionized with high efficiency by resonance enhanced two-photon ionization (R2PI) using the frequency-quadrupled output of the Nd:YAG laser at 266 nm (4.7 eV). Because the degree of fragmentation accompanying R2PI is a function of laser power, mass spectrometric analysis of such fragments also can often improve the specificity of the overall analysis. However, in the case of organic mixture analysis, the complexity of R2PI/fragmentation mass spectra may compromise compound identification tandem mass spectrometry (MS/MS) can also enhance the specificity of analysis over that provided by a single stage of mass spectrometry. Although R2PI/fragmentation and MS/MS can yield complementary data, situations may often occur in which the spectra reveal no unique structural information. Nevertheless, the combination of R2PI and MS/MS can still provide an advantage over the use of R2PI alone.
Date: January 1, 1991
Creator: Goeringer, D.E.; Glish, G.L. & McLuckey, S.A.
Partner: UNT Libraries Government Documents Department

Experimental test of resonant absorption theory. Progress report, July 1-September 30, 1979

Description: The scaling of the hot electron temperature, T/sub h/, with laser intensity, I, has been studied with the laser-shockfront interaction apparatus. The preliminary result for 500 psec laser pulses of intensity I approx. 10/sup 14/ W/cm/sup 2/ is T/sub h/ infinity I/sup ..cap alpha../, where ..cap alpha.. = .35 to .40.
Date: October 1, 1979
Creator: Yablonovitch, E
Partner: UNT Libraries Government Documents Department

Laser-plasma coupling

Description: The following topics are discribed: (1) ionization of target, (2) electromagnetic wave propagation in plasma, (3) collisional absorption, (4) light absorption in collisionless plasma, (5) resonance absorption, (6) instabilities, (7) Brillowin instability, and (8) some other effects. (MOW
Date: November 14, 1978
Creator: Kruer, W.L.
Partner: UNT Libraries Government Documents Department

Enhanced energy deposition symmetry by hot electron transport

Description: High energy electrons produced by resonance absorption carry the CO/sub 2/ laser energy absorbed in a laser fusion pellet. The symmetrization that can be achieved by lateral transport of the hot electrons as they deposit their energy is discussed. A K/sub ..cap alpha../ experiment shows a surprising symmetrization of energy deposition achieved by adding a thin layer of plastic to a copper sphere. Efforts to numerically model this effect are described. (MOW)
Date: January 1, 1981
Creator: Wilson, D.; Mack, J.; Stover, E.; VanHulsteyn, D.; McCall, G. & Hauer, A.
Partner: UNT Libraries Government Documents Department

Surfaces in the interaction of intense long wavelength laser light with plasmas

Description: The role of surface in the interaction of intense CO/sub 2/ laser light with plasmas is reviewed. The collisionless absorption of long wavelength light is discussed. Specific comments on the role of ponderomotive forces and profile steepening on resonant absorption are made. It is shown that at intensities above 10/sup 15/W/cm/sup 2/ the absorption is determined by ion acoustic-like surface modes. It is demonstrated experimentally that harmonics up to the forty-sixth can be generated in steep density profiles. Computer simulations and theoretical mechanisms for this phenomena are presented. The self generation of magnetic fields on surfaces is discussed. The role these fields play in the lateral transport of energy, the insulation of the target from hot electrons, and the acceleration of fast ions is discussed.
Date: January 1, 1985
Creator: Jones, R.D.
Partner: UNT Libraries Government Documents Department

Currents generated by lower hybrid waves

Description: Electron currents can be driven in a linear plasma by the absorption of lower hybrid waves excited primarily in one direction. Current-drive has been demonstrated both for collisional and resonant-electron absorption. The magnitude of the excited currents is compared with the predictions from an electron kinetic equation with a Lorentz collision operator in the regime k/sub parallel to/v/sub te//..omega..<<1.
Date: April 1, 1981
Creator: McWilliams, R. & Motley, R.W.
Partner: UNT Libraries Government Documents Department