36 Matching Results

Search Results

Advanced search parameters have been applied.
in creator/contributor: "Dietrich, F. S."  
Results: 1 - 24 next
open access

New parameterization of the E1 gamma-ray strength function

Description: The giant dipole (GD) parameters of peak energy, width, and cross section were satisfactorily correlated for elements from V to Bi, assuming two overlapping peaks with a separation dependent on deformation. The energy dependence of the GD resonance is assumed to have a Breit-Wigner form, but with an energy-dependent width. The resulting gamma-ray strength function model is used to predict neutron capture cross sections and gamma-ray spectra for isotopes of Ta, Os, and Au. 23 references.
Date: October 18, 1979
Creator: Gardner, D. G. & Dietrich, F. S.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Exploratory gas-target experiment at PEP using the TPC/2. gamma. facility

Description: A pilot nuclear-physics experiment at the PEP ring was performed by bleeding deuterium, argon, and xenon gases into the interaction region containing the TPC/2Y facility. The purpose of the experiment was to obtain information for the design of a dedicated nuclear-physics interaction region at PEP, as well as to obtain a first view of the physics that could be studied at such a facility. 1 ref., 4 figs.
Date: June 1, 1986
Creator: Dietrich, F. S.; Melnikoff, S. O. & Van Bibber, K. A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Can cross sections be accurately known for priori?

Description: Distinct maxima and minima in the neutron total cross section uncertainties were observed in our large scale covariance calculations using a spherical optical potential. In this contribution we investigate the physical origin of this oscillating structure. Specifically, we analyze the case of neutron reactions on {sup 56}Fe, for which total cross section uncertainties are characterized by the presence of five distinct minima at 0.1, 1.1, 5, 25, and 70 MeV. To investigate their origin, we calcul… more
Date: June 24, 2008
Creator: Pigni, M. T.; Dietrich, F. S.; Herman, M. & Oblozinsky, P.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Modeling of High Precision Neutron Nonelastic Cross Sections

Description: A new method has been applied to the determination of neutron nonelastic cross sections for iron {sup 56}Fe and lead {sup 208}Pb for energies between 5 and 26 MeV. These data have estimated errors of only a few percent and do not suffer from the ambiguities encountered in earlier nonelastic data. We attempt to fit these high precision data using both a semiclassical single phase shift model (nuclear Ramsauer model) as well as a recent global optical model that well reproduces a wide body of neu… more
Date: February 5, 2007
Creator: Dietrich, F. S.; Anderson, J. D.; Bauer, R. W.; Grimes, S. M. & McNabb, D. P.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Radiative capture mechanisms in the {sup 89}Y({rvec p},{gamma}) reaction

Description: We have measured the spectra of gamma rays from approximately 14 MeV to the endpoint in the {sup 89}Y({rvec p},{gamma}) reaction with 19.6 MeV polarized protons from the TUNL tandem accelerator. Gamma spectra were measured with a pair of 25.4 cm {times} 25.4 cm anticoincidence shielded NaI detectors at angles of 30, 55, 90, 125, and 150{degrees} with respect to the incident beam. The {gamma}-ray spectra show significant analyzing powers and forward peaking of the angular distributions. These fe… more
Date: July 28, 1993
Creator: Parker, W. E.; Dietrich, F. S.; Sale, K. E.; Kammeraad, J. E.; Luke, S. J.; Weller, H. R. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Comparison of Ramsauer and Optical Model Neutron Angular Distributions

Description: The nuclear Ramsauer model is a semi-classical, analytic approximation to nucleon-nucleus scattering that reproduces total cross section data at the 1% level for A > 40, E{sub n} = 5-60 MeV with 7-10 parameters. A quick overview of the model is given, demonstrating the model's utility in nuclear data evaluation. The Ramsauer model predictions for reaction cross section, elastic cross section, and elastic scattering angular distributions are considered. In a recent paper it has been shown tha… more
Date: September 30, 2004
Creator: McNabb, D. P.; Anderson, J. D.; Bauer, R. W.; Dietrich, F. S.; Grimes, S. M. & Hagmann, C. A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Measurement of 150-Sm(n,2ngammai) 149-Sm cross sections between threshold and 20 MeV

Description: Absolute partial {gamma}-ray cross sections for the production of discrete {gamma}-rays from the reaction {sup 150}Sm(n,2n{gamma}{sub i}){sup 149}Sm were measured using the GEANIE {gamma}-ray spectrometer coupled with the intense white neutron source at WNR/LANSCE. The measurements were made for incident neutron energies between threshold (8.04 MeV) and 20 MeV. The partial cross sections for 21 {gamma}-rays were extracted from the data. Of these, 17 were compared to calculations performed using… more
Date: August 2, 2004
Creator: Cooper, J.; Becker, J.; Dashdorj, D.; Dietrich, F. S.; Garrett, P.; Hoffman, R. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Alternate Approach to the 239Pu(n,2n) Cross Section

Description: Using existing experimental data for neutron-induced total, elastic, inelastic, reaction and fission cross sections, as well as results from nuclear model calculations and evaluations from nuclear reaction data libraries, we derived an estimate for the cross sections for the {sup 235}U(n,2n) and {sup 239}Pu(n,2n) reactions for the neutron energy range from threshold to approximately 12 MeV. In effect, our approach is based on subtracting the fission and inelastic cross sections from the total r… more
Date: September 1, 2000
Creator: Anderson, J. D.; Bauer, R. W.; Becker, J. A.; Dietrich, F. S. & McNabb, D. P.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

The prediction of Neutron Elastic Scattering from Tritium for E(n) = 6-14 MeV

Description: In a recent report Navratil et al. evaluated the angle-integrated cross section and the angular distribution for 14-MeV n+T elastic scattering by inferring these cross sections from accurately measured p+3He angular distributions. This evaluation used a combination of two theoretical treatments, based on the no-core shell model and resonating-group method (NCSM/RGM) and on the R-matrix formalism, to connect the two charge-symmetric reactions n+T and p+{sup 3}He. In this report we extend this tr… more
Date: June 14, 2010
Creator: Anderson, J. D.; Dietrich, F. S.; Luu, T.; McNabb, D. P.; Navratil, P. & Quaglioni, S.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Deducing the 237U(n,f) cross-section using the Surrogate Ratio Method

Description: The authors have deduced the cross section for {sup 237}U(n,f) over an equivalent neutron energy range from 0 to 20 MeV using the Surrogate Ratio method. A 55 MeV {sup 4}He beam from the 88 Inch Cyclotron at Lawrence Berkeley National Laboratory was used to induce fission in the following reactions: {sup 238}U({alpha},{alpha}{prime}f) and {sup 236}U({alpha},{alpha}{prime}f). The {sup 238}U reaction was a surrogate for {sup 237}U(n,f) and the {sup 236}U reaction was used as a surrogate for {sup … more
Date: December 29, 2005
Creator: Burke, J. T.; Bernstein, L. A.; Escher, J.; Ahle, L.; Church, J. A.; Dietrich, F. S. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Optical Model and Cross Section Uncertainties

Description: Distinct minima and maxima in the neutron total cross section uncertainties were observed in model calculations using spherical optical potential. We found this oscillating structure to be a general feature of quantum mechanical wave scattering. Specifically, we analyzed neutron interaction with 56Fe from 1 keV up to 65 MeV, and investigated physical origin of the minima.We discuss their potential importance for practical applications as well as the implications for the uncertainties in total a… more
Date: October 5, 2009
Creator: Herman, M. W.; Pigni, M. T.; Dietrich, F. S. & Oblozinsky, P.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

High Energy Gamma Rays from p+X, X=Cu, Ag, Au at 34 MeV

Description: In this paper we present results from the measurement of the gamma ray yield in the reaction of 34-MeV protons on Cu, Ag and Au. The protons were produced by the University of Washington superconducting linac. The gamma rays were measured using a large NaI and two large BaF{sub 2} detectors. Angular distributions were obtained for each of the three targets. Data for the Cu and Ag target were taken at six lab angles between 35 and 135 degrees, while data were taken at eight lab angles between 35… more
Date: March 7, 2000
Creator: Luke, S. J.; Dietrich, F. S.; Chadwick, M. B.; Gossett, C. A.; Kaplan, M. S.; McLain, B. T. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Proton Reaction Cross Sections Measured in the BNL/AGS E943 Experiment

Description: We have measured proton reaction cross sections over a wide mass and energy range at the Brookhaven AGS accelerator. The samples were elemental Be, C, Al, Cu, W, and Pb; the measurements were carried out at ten incident proton kinetic energies in the range 0.54 to 7.8 GeV. The experiment was similar to an earlier experiment in the 200-550 MeV range by Renberg et al. The new results are in good agreement with those of Renberg et al. at the overlap point near 550 MeV. The combined results of the … more
Date: November 1, 2001
Creator: Dietrich, F. S.; Hartouni, E. P.; Johnson, S. C.; Schmid, G. J.; Soltz, R.; Abfalterer, W. P. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Study of gamma-ray strength functions

Description: The use of gamma-ray strength function systematics to calculate neutron capture cross sections and capture gamma-ray spectra is discussed. The ratio of the average capture width, GAMMA/sub ..gamma../-bar, to the average level spacing, D/sub obs/, both at the neutron separation energy, can be derived from such systematics with much less uncertainty than from separate systematics for values of GAMMA/sub ..gamma../-bar and D/sub obs/. In particular, the E1 gamma-ray strength function is defined in… more
Date: August 7, 1980
Creator: Gardner, D. G.; Gardner, M. A. & Dietrich, F. S.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

The 75As(n,2n) Cross Sections into the 74As Isomer and Ground State

Description: The {sup 75}As(n, 2n) cross section for the population of the T{sub 1/2} = 26.8-ns isomer at E{sub x} = 259.3 keV in {sup 74}As has been measured as a function of incident neutron energy, from threshold to E{sub n} = 20 MeV. The cross section was measured using the GEANIE spectrometer at LANSCE/WNR. For convenience, the {sup 75}As(n, 2n) population cross section for the {sup 74}As ground state has been deduced as the difference between the previously-known (n, 2n) reaction cross section and the… more
Date: June 30, 2003
Creator: Younes, W.; Garrett, P. E.; Becker, J. A.; Bernstein, L. A.; Ormand, W. E.; Dietrich, F. S. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Neutron capture cross sections for unstable nuclei in the mass 90 region derived from proton capture measurements. [Strength functions]

Description: Experimental measurements were made of the production cross sections and energy distributions of gamma rays emitted when the stable targets /sup 88/Sr, /sup 89/Y and /sup 90/Zr are exposed to protons in the energy range 3 to 8 MeV. The data are being analyzed using a recent version of the Uhl statistical model code. One conclusion is that while the gamma-ray strength functions employed reproduce the proton capture cross sections, they do not achieve the same degree of hardness observed in the m… more
Date: September 1, 1978
Creator: Gardner, D. G.; Dietrich, F. S. & Heikkinen, D. W.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Neutron and Charged-Particle Induced Cross Sections for Radiochemistry in the Region of Samarium, Europium, and Gadolinium

Description: We have developed a set of modeled nuclear reaction cross sections for use in radiochemical diagnostics. Systematics for the input parameters required by the Hauser-Feshbach statistical model were developed and used to calculate neutron and proton induced nuclear reaction cross sections in the mass region of samarium, europium and gadolinium (62 {le} Z {le} 64, 82 {le} N {le} 96).
Date: November 30, 2004
Creator: Hoffman, R. D.; Kelley, K.; Dietrich, F. S.; Bauer, R. & Mustafa, M.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Neutron and Charged-Particle Induced Cross Sections for Radiochemistry for Isotopes of Scandium, Titanium, Vanadium, Chromium, Manganese, and Iron

Description: We have developed a set of modeled nuclear reaction cross sections for use in radiochemical diagnostics. Local systematics for the input parameters required by the Hauser-Feshbach statistical model were developed and used to calculate neutron and proton induced nuclear reaction cross sections in the mass region of scandium, titanium, vanadium, chromium, manganese, and iron (21 {le} Z {le} 26, 20 {le} N {le} 32).
Date: November 30, 2004
Creator: Kelley, K.; Hoffman, R. D.; Dietrich, F. S.; Bauer, R. & Mustafa, M.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

The (3He,tf) as a surrogate reaction to determine (n,f) cross sections in the 10 to 20 MeV energy range

Description: The surrogate reaction 238U(3He,tf) is used to determine the 237Np(n,f) cross section indirectly over an equivalent neutron energy range from 10 to 20 MeV. A self-supporting ~;;761 mu g/cm2 metallic 238U foil was bombarded with a 42 MeV 3He2+ beam from the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory (LBNL). Outgoing charged particles and fission fragments were identified using the Silicon Telescope Array for Reaction Studies (STARS), consists of two 140 mu m and one 1000 mu m Mic… more
Date: February 25, 2009
Creator: Basunia, M. S.; Clark, R. M.; Goldblum, B. L.; Bernstein, L. A.; Phair, L.; Burke, J. T. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Determining neutron capture cross sections with the Surrogate Reaction Technique: Measuring decay probabilities with STARS

Description: Neutron-induced reaction cross sections are sometimes difficult to measure due to target or beam limitations. For two-step reactions proceeding through an equilibrated intermediate state, an alternate ''surrogate reaction'' technique can be applicable, and is currently undergoing investigation at LLNL. Measured decay probabilities for the intermediate nucleus formed in a light-ion reaction can be combined with optical-model calculations for the formation of the same intermediate nucleus via the… more
Date: July 14, 2004
Creator: Church, J. A.; Ahle, L.; Bernstein, L. A.; Cooper, J.; Dietrich, F. S.; Escher, J. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

A New Method for Estimating Neutron Reaction Cross Sections Based on Wick's Limit

Description: Wick's limit is an inequality that relates the zero-degree differential elastic scattering cross section to the total cross section. The deviation of Wick's limit from an exact equality is small over a wide range of incident energies and target masses. Under these circumstances we show that Wick's limit can be used to correlate the uncertainties in the two terms of the reaction (nonelastic) cross section expressed as the difference between the total and angle-integrated elastic cross sections. … more
Date: October 13, 2004
Creator: Dietrich, F. S.; Anderson, J. D.; Bauer, R. W. & Grimes, S. M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Failure of Stadard Optical Models to Reproduce Neutron Total Cross Section Difference in the W Isotopes

Description: Recently cross section differences among the isotopes{sup 182,184,186}W have been measured as part of a study of total cross sections in the 5-560 MeV energy range. These measurements show oscillations up to 150 mb between 5 and 100 MeV. Spherical and deformed phenomenological optical potentials with typical radial and isospin dependences show very small oscillations, in disagreement with the data. In a simple Ramsauer model, this discrepancy can be traced to a cancellation between radial and i… more
Date: November 1, 2001
Creator: Anderson, J. D.; Bauer, R. W.; Dietrich, F. S.; Grimes, S. M.; Finlay, R. W.; Abfalterer, W. P. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
Back to Top of Screen