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Nonperturbative theory of double photoionization of the hydrogen molecule

Description: We present completely ab initio nonperturbative calculations of the integral and single differential cross sections for double photoionization of H2 for photon energies from 53.9 to 75.7 eV. The method of exterior complex scaling, implemented with B-splines, is used to solve the Schrodinger equation for a correlated continuum wave function corresponding to a single photon having been absorbed by a correlated initial state. The results are in good agreement with experimental integral cross sections.
Date: October 1, 2004
Creator: Vanroose, W.; Martin, F.; Rescigno, T.N. & McCurdy, C.W.
Partner: UNT Libraries Government Documents Department

Efficient use of Bayes` equations for fitting neutron-induced cross section and integral data

Description: Analysis of differential and integral neutron data requires the use of a fitting procedure such as Bayes` method, used in the analysis code SAMMY. In this paper, techniques for more efficient use of Bayes` method are described. A reformulation of Bayes` equations permits truly simultaneous fitting to multiple measurements without overhead costs required for calculating theoretical values simultaneously. Several techniques for properly including data covariances are also described.
Date: December 31, 1998
Creator: Larson, N.M.; Leal, L.C. & Derrien, H.
Partner: UNT Libraries Government Documents Department

A WIMS-NESTLE reactor physics model for an RBMK reactor

Description: This work describes the static neutronic calculations made for a three-dimensional model of an RBMK (Russian) reactor. Future work will involve the use of this neutronic model and a thermal-hydraulic model in coupled calculations. The lattice code, WIMS-D, was used to obtain the cross sections for the static neutronic calculations. The static reactor neutronic calculations were made with NESTLE, a three-dimensional nodal diffusion code. The methods used to establish an RBMK reactor model for use in these codes are discussed, and the cross sections calculated are given.
Date: August 1, 1996
Creator: Perry, R.T. & Meriwether, G.H.
Partner: UNT Libraries Government Documents Department

Inclusive muon and b quark production cross sections in p{bar p} collisions at {radical}s = 1.8 TeV

Description: We report on the measurement of inclusive muon and b quark production by the D0 collaboration in p{bar p} collisions at {radical}s = 1.8 TeV at the Fermilab Tevatron Collider. The results represent a refined analysis of the previously published 1992--93 data. We measure the muon cross section due to b quark decays over the kinematic range 4 < p{sub T}{sup {mu}} < 30 GeV/c and {vert_bar}y{sup {mu}}{vert_bar} < 0.8. The extracted b quark production cross section is consistent with next to leading order QCD predictions within theoretical and experimental errors. The improved inclusive b quark production cross section is 6.9 {plus_minus}0.1(stat) {plus_minus} 2.2(syst) {mu}b for p{sub T}{sup {mu}} > 6 GeV/c and {vert_bar}y{sup b}{vert_bar} < 1.0.
Date: July 1, 1995
Creator: Abachi, S.
Partner: UNT Libraries Government Documents Department

State-to-state dynamics of molecular energy transfer. Annual performance report, April 1, 1993--March 31, 1994

Description: During this budget period we have focussed our efforts toward completing experimental measurements of differential cross sections for fully-resolved state-to-state angular momentum transfer in NO + Ar collisions, including both the electronically adiabatic and nonadiabatic channels represented by: NO({sup 2}P{sub 1/2}, {nu} = 0,j = 1/2) + Ar {yields} NO({sup 2}P{sub l/2}, {nu} = 0,j{prime}) + Ar and NO({sup 2}P{sub 1/2}, {nu} = 0,j = 1/2) + Ar {yields} NO({sup 2}P{sub 3/2}, {nu} = 0,j{prime}) + Ar. We have also begun measurements of integral cross sections as a function of collision energy for state-resolved rotational excitation of the first triatomic molecule to be examined by this technique, in the system SO{sub 2} + He. Concurrently, we have also carried out collision experiments in the system SO{sub 2} + He. These are the first crossed molecular beam experiments on state-resolved rotational energy transfer of a triatomic molecule. State-to-state integral cross sections have been measured as a function of final rotational state at a fixed collision energy of 473 cm{sup {minus}1}, and as a function of collision energy for six selected final rotational states. Initial SO{sub 2} rotational temperatures less than 3K were achieved with 0.3 mole-% of the molecule seeded in 20 atm of He. State-selective detection of the scattered products was done by LIF on the strong C(122){l_arrow}X(000) transition at 445 nm, which has been analyzed by Yamanouchi et al. Because of the selection rules and nuclear spin statistics, the k{sub a}=0 and k{sub a}=l subbands dominate the LIF spectrum. This data is currently being analyzed and the collision dynamics modelled theoretically for comparison. Cross sections for vibrational excitation in this system proved to be too small to measure.
Date: November 30, 1993
Creator: Gentry, W. R.
Partner: UNT Libraries Government Documents Department

Criticality Benchmark Analysis of Water-Reflected Uranium Oxyfluoride Slabs

Description: A series of twelve experiments were conducted in the mid 1950's at the Oak Ridge National Laboratory Critical Experiments Facility to determine the critical conditions of a semi-infinite water-reflected slab of aqueous uranium oxyfluoride (UO2F2). A different slab thickness was used for each experiment. Results from the twelve experiment recorded in the laboratory notebook were published in Reference 1. Seven of the twelve experiments were determined to be acceptable benchmark experiments for the inclusion in the International Handbook of Evaluated Criticality Safety Benchmark Experiments. This evaluation will not only be available to handbook users for the validation of computer codes and integral cross-section data, but also for the reevaluation of experimental data used in the ANSI/ANS-8.1 standard. This evaluation is important as part of the technical basis of the subcritical slab limits in ANSI/ANS-8.1. The original publication of the experimental results was used for the determination of bias and bias uncertainties for subcritical slab limits, as documented by Hugh Clark's paper 'Subcritical Limits for Uranium-235 Systems'.
Date: November 1, 2009
Creator: Marshall, Margaret A. & Bess, John D.
Partner: UNT Libraries Government Documents Department

OSMOSE experiment representativity studies.

Description: The OSMOSE program aims at improving the neutronic predictions of advanced nuclear fuels through measurements in the MINERVE facility at the CEA-Cadarache (France) on samples containing the following separated actinides: Th-232, U-233, U-234, U-235, U-236, U-238, Np-237, Pu-238, Pu-239, Pu-240, Pu-241, Pu-242, Am-241, Am-243, Cm-244 and Cm-245. The goal of the experimental measurements is to produce a database of reactivity-worth measurements in different neutron spectra for the separated heavy nuclides. This database can then be used as a benchmark for integral reactivity-worth measurements to verify and validate reactor analysis codes and integral cross-section values for the isotopes tested. In particular, the OSMOSE experimental program will produce very accurate sample reactivity-worth measurements for a series of actinides in various spectra, from very thermalized to very fast. The objective of the analytical program is to make use of the experimental data to establish deficiencies in the basic nuclear data libraries, identify their origins, and provide guidelines for nuclear data improvements in coordination with international programs. To achieve the proposed goals, seven different neutron spectra can be created in the MINERVE facility: UO2 dissolved in water (representative of over-moderated LWR systems), UO2 matrix in water (representative of LWRs), a mixed oxide fuel matrix, two thermal spectra containing large epithermal components (representative of under-moderated reactors), a moderated fast spectrum (representative of fast reactors which have some slowing down in moderators such as lead-bismuth or sodium), and a very hard spectrum (representative of fast reactors with little moderation from reactor coolant). The different spectra are achieved by changing the experimental lattice within the MINERVE reactor. The experimental lattice is the replaceable central part of MINERVE, which establishes the spectrum at the sample location. This configuration leads to a uniform well-behaved system so that the reactor configuration is in the fundamental mode. In fact, an important ...
Date: October 10, 2007
Creator: Aliberti, G. & Klann, R.
Partner: UNT Libraries Government Documents Department

Annotated bibliography covering generation and use of evaluated cross section uncertainty files

Description: Literature references related to definition, generation, and use of evaluated cross section uncertainty (variance-covariance) files are listed with comments intended primarily to guide the reader toward materials of immediate interest. Papers are also cited that cover covariance information for individual experiments and that relate to production and use of multigroup covariance matrices. Titles are divided among several major categories.
Date: March 1, 1983
Creator: Peelle, R.W. & Burrows, T.W.
Partner: UNT Libraries Government Documents Department

Specifications for adjusted cross section and covariance libraries based upon CSEWG fast reactor and dosimetry benchmarks

Description: The present work proposes a specific plan of cross section library adjustment for fast reactor core physics analysis using information from fast reactor and dosimetry integral experiments and from differential data evaluations. This detailed exposition of the proposed approach is intended mainly to elicit review and criticism from scientists and engineers in the research, development, and design fields. This major attempt to develop useful adjusted libraries is based on the established benchmark integral data, accurate and well documented analysis techniques, sensitivities, and quantified uncertainties for nuclear data, integral experiment measurements, and calculational methodology. The adjustments to be obtained using these specifications are intended to produce an overall improvement in the least-squares sense in the quality of the data libraries, so that calculations of other similar systems using the adjusted data base with any credible method will produce results without much data-related bias. The adjustments obtained should provide specific recommendations to the data evaluation program to be weighed in the light of newer measurements, and also a vehicle for observing how the evaluation process is converging. This report specifies the calculational methodology to be used, the integral experiments to be employed initially, and the methods and integral experiment biases and uncertainties to be used. The sources of sensitivity coefficients, as well as the cross sections to be adjusted, are detailed. The formulae for sensitivity coefficients for fission spectral parameters are developed. A mathematical formulation of the least-square adjustment problem is given including biases and uncertainties in methods.
Date: June 1, 1979
Creator: Weisbin, C.R.; Marable, J.H.; Collins, P.J.; Cowan, C.L.; Peelle, R.W. & Salvatores, M.
Partner: UNT Libraries Government Documents Department

Investigation of the influence of the neutron spectrum in determinations of integral cross-section ratios

Description: Ratio measurements are routinely employed in studies of neutron interaction processes in order to generate new differential cross-section data or to test existing differential cross-section information through examination of the corresponding response in integral neutron spectra. Interpretation of such data requires that careful attention be given to details of the neutron spectra involved in these measurements. Two specific tasks are undertaken in the present investigation: (1) Using perturbation theory, a formula is derived which permits one to relate the ratio measured in a realistic quasimonoenergetic spectrum to the desired pure monoenergetic ratio. This expression involves only the lowest-order moments of the neutron energy distribution and corresponding parameters which serve to characterize the energy dependence of the differential cross sections, quantities which can generally be estimated with reasonable precision from the uncorrected data or from auxiliary information. (2) Using covariance methods, a general formalism is developed for calculating the uncertainty of a measured integral cross-section ratio which involves an arbitrary neutron spectrum. This formalism is employed to further examine the conditions which influence the sensitivity of such measured ratios to details of the neutron spectra and to their uncertainties. Several numerical examples are presented in this report in order to illustrate these principles, and some general conclusion are drawn concerning the development and testing of neutron cross-section data by means of ratio experiments. 16 refs., 1 fig., 4 tabs.
Date: November 1, 1987
Creator: Smith, D.L.
Partner: UNT Libraries Government Documents Department

US/UK actinides experiment at the Dounreay PFR. 1: Fission products

Description: The US and the United Kingdom have been engaged in a joint research program in which samples of higher actinides were irradiated in the 600-MW Dounreay Prototype Fast Reactor in Scotland. Analytical results using mass spectrometry and radiometry for actinides and fission products are now available for the samples in Fuel Pins 1 and 2 which were irradiated for 63 full-power days and for the samples in Fuel Pin 4 which were irradiated for 492 full-power days. Results from these three fuel pins are providing estimates of integral cross sections and fission yields.
Date: September 1, 1995
Creator: Raman, S. & Murphy, B.D.
Partner: UNT Libraries Government Documents Department

Neutron activation cross sections for copper, europium, hafnium, iron, nickel, silver, terbium and titanium from the Argonne, Los Alamos and Jaeri collaboration

Description: Several fast-neutron activation reactions for copper, europium, hafnium, iron, nickel, silver, terbium and titanium that are important to fusion energy have been investigated in three distinct neutron fields generated by accelerators at Argonne National Laboratory and Los Alamos National Laboratory, USA, and Japan Atomic Energy Research Institute, Tokai, Japan. Final differential cross-sections at 14.7 MeV and integral cross sections for the Be(d,n) thick-target spectrum produced by 7-MeV deutrons are reported here. Data have also been acquired for neutron energies near 10 MeV. However, these latter results will be made available after problems associated with determining the neutron-energy scale and interpreting the quasi-differential cross-sections measured near threshold are resolved.
Date: July 1, 1995
Creator: Meadows, J.W.; Smith, D.L.; Greenwood, L.R.; Haight, R.C.; Ideda, Y. & Konno, C.
Partner: UNT Libraries Government Documents Department

Atlas of photoneutron cross sections obtained with monoenergetic photons. Final edition, 1986

Description: In view of the need for a comprehensive compilation of photoneutron cross-section data, these monoenergetic-photon data are gathered together here and presented in a uniform format. This compilation updates and supersedes the earlier editions of this Atlas. A more complete compilation is being assembled by the photonuclear group at the National Bureau of Standards. 15 refs., 174 figs.
Date: June 1, 1986
Creator: Dietrich, S.S. & Berman, B.L.
Partner: UNT Libraries Government Documents Department

One and a half centered expansion for ion-atom collisions

Description: Fast ion-atom collisions in which charge transfer plays a dominant role have been traditionally treated by a two center expansion (TCE): the state wavefunction is approximated by a truncated set of Hilbert states centered on the target and projectile. This method is accurate but expensive in the use of computer time. A new method which allows charge transfer through variational time independent amplitudes, and target excitation and ionization through variational time dependent amplitudes is presented. The method retains the efficiency of a single centered expansion and yet reproduces the conventional TCE results in situations where charge transfer is dominant. Comparison to experiment is made.
Date: January 1, 1980
Creator: Reading, J.F.; Ford, A.L. & Becker, R.L.
Partner: UNT Libraries Government Documents Department

Measurement of the integral capture and fission cross sections for /sup 232/Th in the CFRMF

Description: The recent evaluation of the cross-section data bases for /sup 232/Th capture and fission emphasized significant normalization discrepancies between the available differential data. To help resolve the normalization discrepancies, the capture and fission integral cross sections were measured for /sup 232/Th in the fast neutron zone of the Coupled Fast Reactivity Measurements Facility (CFRMF). The cross sections are derived from the radiometric determination of the saturation reaction rates for fission and capture based on the Ge(Li) spectrometric measurement of the absolute gamma emission rates of the 537-keV and 1596-keV lines in the /sup 140/Ba - /sup 140/La decay and the 311.9-keV line in the /sup 233/Pa decay. For capture and fission, respectively, the measured integral cross sections are 291 mb +- 3% and 19.6 mb +- 5%. The ratios of the integral cross sections computed with ENDF/B-IV thorium cross sections and the CFRMF neutron spectrum to the above values are 0.99 for capture and 0.90 for fission. 19 references.
Date: January 1, 1979
Creator: Anderl, R.A. & Harker, Y.D.
Partner: UNT Libraries Government Documents Department

Measurements of scattering processes in negative ion-atom collisions. Technical progress report, 1 September 1992--31 August 1993

Description: This Technical Progress Report describes the progress made on the research objectives during the past twelve months. This research project is designed to provide measurements of various scattering processes which occur in H{sup {minus}} collisions with atomic (specifically, noble gas and atomic hydrogen) targets at intermediate energies. These processes include elastic scattering, single- and double-electron detachment, and target excitation/ionization. For the elastic and target inelastic processes where H{sup {minus}} is scattered intact, the experimental technique of Ion Energy-Loss Spectroscopy (IELS) will be employed to identify the final target state(s). In most of the above processes, cross sections are unknown both experimentally and theoretically. The measurements in progress will provide either experimentally determined cross sections or set upper limits to those cross sections. In either case, these measurements will be stringent tests of our understanding in energetic negative ion - atom collisions. In addition secondary negative particle emission yields for H{sup 0} on Cu in the 3 to 50 keV range are shown.
Date: May 1, 1993
Creator: Kvale, T. J.
Partner: UNT Libraries Government Documents Department

Part 1: Kinetic energy dependencies of selected ion-molecule reactions; Part 2: Photochemistry of (FSO sub 3 ) sub 2 , FSO sub 3 , and FNO

Description: In Part 1, guided ion beam mass spectroscopy is used to study the ion-molecule reactions O{sup +}({sup 4}S) + H{sub 2}(D{sub 2}, HD), (O{sup +}{sup 4}S) + N{sub 2}, C{sup +}({sup 2}P) + O{sub 2} and C{sup +}(P) + N{sub 2}. Integral reaction cross sections are measured as a function of kinetic energy in the center-of-mass frame. Reaction mechanisms and dynamics are examined, and the results are compared to the predictions of phase space theory. In some cases, thermochemistry for neutral and ionic species is derived. In Part 2, photoabsorption cross sections are measured for peroxydisulfuryl difluoride, (FSO{sub 3}){sub 2}, and the fluorosulfate radical, FSO{sub 3}. Photoabsorption cross sections of nitrosyl fluoride, FNO, are also measured, and the FNO absorption spectrum is analyzed and assigned. Spectral results for FNO are compared to the predictions and ab initio calculations and to those obtained for the isoelectronic compound HONO. 259 refs., 34 figs., 9 tabs.
Date: July 1, 1991
Creator: Burley, J.D.
Partner: UNT Libraries Government Documents Department

Cross sections for neutron-producing reactions induced by 6- and 10-MeV neutrons incident on /sup 10/B and /sup 11/B

Description: Using the time-of-flight technique, the /sup 10/B and /sup 11/B neutron emission spectra at incident neutron energies of 6.00 and 10.00 MeV for angles between 20/sup 0/ and 145/sup 0/ have been measured. Double differential cross sections and their integrated values have been extracted and are presented in tables and graphs. The integrated values (corrected for charged particle cross sections, if necessary) are in excellent agreement with measured total cross sections. 15 refs., 39 figs., 14 tabs.
Date: May 1, 1986
Creator: Drosg, M.; Lisowski, P.W.; Drake, D.M.; Hardekopf, R.A. & Muellner, S.M.
Partner: UNT Libraries Government Documents Department

Nonelastic-scattering cross sections of elemental nickel. [1. 3 to 4. 5 MeV]

Description: Neutron total cross sections of elemental nickel were measured from 1.3 to 4.5 MeV, at intervals of approx. 50 keV, with resolutions of 30 to 50 keV and to accuracies of 1 to 2.5%. Neutron differential-elastic-scattering cross sections were measured from 1.45 to 3.8 MeV, at intervals and with resolutions comparable to those of the total cross sections, and to accuracies of 3 to 5%. The nonelastic-scattering cross section is derived from the measured values to accuracies of greater than or equal to 6%. The experimental results are compared with previously reported values as represented by ENDF/B-V, and areas of consistency and discrepancy, noted. The measured results are shown to be in good agreement with the predictions of a model previously reported by the authors. 4 figures, 1 table.
Date: June 1, 1980
Creator: Smith, A.B.; Guenther, P.T. & Whalen, J.F.
Partner: UNT Libraries Government Documents Department

K-components for the approx. 1. 4-, approx. 1. 6-, and approx. 1. 7-MeV structures in the fission of /sup 232/Th + n

Description: Neutron-induced angle-integrated fission cross sections of /sup 232/Th were measured from 0.7 to 9 MeV with a nominal neutron energy resolution of 0.15 ns/m. Data were taken for the angular intervals 0 to 23.4/sup 0/, 0 to 33.7/sup 0/, 0 to 51.7/sup 0/, and 0 to 90/sup 0/. The structures at approx. 1.4, approx. 1.6, and approx. 1.7 MeV were interpreted in terms of rotational bands with K = 1/2, 3/2, and greater than or equal to 5/2. The approximate relative fission strengths for the K-bonds are in the proportion 1.7:2.4:1.0, 0.0:2.6:1.0, and 1.0:2.8:0.0 for the three structures, respectively.
Date: July 1, 1981
Creator: Auchampaugh, G.F.; Plattard, S.; Hill, N.W.; de Saussure, G.; Perez, R.B. & Harvey, J.A.
Partner: UNT Libraries Government Documents Department

Neutron-induced fission-cross-section measurements and calculations of selected transplutonic isotopes

Description: The neutron-induced fission cross sections of /sup 242m/Am and /sup 245/Cm have been measured over an energy range of 10/sup -4/ eV to approx. 20 MeV in a series of experiments at three facilities during the past several years. The combined results of these measurements, in which only sub-milligram quantities of enriched isotopes were used, yield cross sections with uncertainties of approximately 5% below 10 MeV relative to the /sup 235/U standard cross section used to normalize the data. We summarize the resonance analysis of the /sup 242m/Am(n,f) cross section in the eV region. Hauser-Feshbach statistical calculations of the detailed fission cross sections of /sup 235/U and /sup 245/Cm have been carried out over the energy region from 0.1 to 5 MeV and these results are compared with our experimental data.
Date: August 27, 1982
Creator: White, R.M. & Browne, J.C.
Partner: UNT Libraries Government Documents Department

Analysis of n + /sup 197/Au cross sections for E/sub n/ = 0. 01-20 MeV

Description: An analysis of n + /sup 197/Au reactions has been completed for incident neutron energies between 0.01 and 20 MeV. The analysis involves use of a deformed optical model to calculate neutron transmission coefficients, a giant-dipole-resonance model and experimental data to determine gamma-ray transmission coefficients, and Hauser-Feshbach statistical theory to calculate partial reaction cross sections. Particular emphasis was given to obtaining gamma-ray strength functions that are consistent with spectral measurements of gamma-ray emission between E/sub n/ = 0.2 and 20 MeV by Morgan and Newman, while at the same time requiring agreement with (n,..gamma..) and (n,xn) cross-section data. 16 references.
Date: September 9, 1984
Creator: Young, P.G. & Arthur, E.D.
Partner: UNT Libraries Government Documents Department

Covariances for measured activation and fission ratios data

Description: Methods which are routinely used in the determination of covariance matrices for both integral and differential activation and fission-ratios data acquired at the Argonne National Laboratory Fast-Neutron Generator Facility (FNG) are discussed. Special consideration is given to problems associated with the estimation of correlations between various identified sources of experimental error. Approximation methods which are commonly used to reduce the labor involved in this analysis to manageable levels are described. Results from some experiments which have been recently carried out in this laboratory are presented to illustrate these procedures. 13 refs., 1 fig., 5 tabs.
Date: January 1, 1986
Creator: Smith, D.L.; Meadows, J.W. & Watanabe, Y.
Partner: UNT Libraries Government Documents Department