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Neutron-capture cross sections of the tungsten isotopes /sup 182/W, /sup 183/W, /sup 184/W, and /sup 186/W from 2. 6 to 2000 keV

Description: Neutron-capture cross sections of four stable tungsten isotopes were measured as a function of energy by time of flight at the Oak Ridge Electron Linear Accelerator. The resolution achieved, ..delta..E/E about 1/750 FWHM, has allowed the analysis of several hundred resonance peaks at energies a few kiloelectron volts above the neutron-binding energy. Strength functions were fitted to the average cross sections up to about 100 keV, and average cross sections were extended with less precision from 100 to 2000 keV. The capture cross section of natural tungsten was calculated from measurements for individual isotopes. Compound nucleus calculations have been made with deformed optical model parameters for comparison with experimental cross sections.
Date: April 1, 1982
Creator: Macklin, R.L.; Drake, D.M. & Arthur, E.D.
Partner: UNT Libraries Government Documents Department

Differential cross sections of /sup 3/H(p,n)/sup 3/He and of /sup 6/Li(n,t)/sup 4/He by using triton beams between 5. 95 and 19. 15 MeV and a reevaluation of the p-T neutron production cross sections up to 12 MeV

Description: Six angular distributions and the zero degree excitation function of the reaction /sup 1/H(t,n)/sup 3/He between 5.95 and 19.15 MeV were measured to provide back angle data for the /sup 3/H(p,n)/sup 3/He reaction between 2.0 and 6.4 MeV proton energy. Together with relative angular distributions at 2.22 and 3.00 MeV these data are the backbone of the new evaluation which gives appreciably higher angle yields than previous ones. Consistency of the data base is not very good resulting in maximum scale errors of +-4% and maximum shape error of the angular distributions of +-3%. Data of the reaction /sup 4/He(t,n/sub x/)/sup 6/Li can contribute to the knowledge of the cross section standard /sup 6/Li(n,t)/sup 4/He, the time-reversed reaction. New data for triton energies between 11.9 and 16.4 MeV (corresponding to neutron energies for N-/sup 6/Li between 2.3 and 5.3 MeV) are presented both for the population of the ground state in /sup 6/Li and the first excited state. In addition, data of the same reaction obtained in a previous experiment were revised above 12.8 MeV taking a 0.1% impurity of hydrogen into account.
Date: May 1, 1985
Creator: Drosg, M.; Haouat, G.; Stoeffel, W. & Drake, D.M.
Partner: UNT Libraries Government Documents Department

Fast neutron capture cross sections of /sup 169/Tm, /sup 191/Ir, /sup 193/Ir, and /sup 175/Lu for 3 less than or equal to E/sub n/ less than or equal to 2000 keV

Description: Fast neutron capture cross sections of /sup 169/Tm, /sup 191/Ir, /sup 193/Ir, and /sup 175/Lu, and the /sup 6/Li(n,..cap alpha..)/sup 3/H cross sections to which they are normalized are presented in tabular form for neutron energies between 3 and 2000 keV.
Date: November 1, 1977
Creator: Macklin, R.L.; Drake, D.M. & Malanify, J.J.
Partner: UNT Libraries Government Documents Department

New electronically black neutron detectors

Description: Two neutron detectors are described that can function in a continuous radiation background. Both detectors identify neutrons by recording a proton recoil pulse followed by a characteristic capture pulse. This peculiar signature indicates that the neutron has lost all its energy in the scintillator. Resolutions and efficiencies have been measured for both detectors.
Date: March 1, 1986
Creator: Drake, D.M.; Feldman, W.C. & Hurlbut, C.
Partner: UNT Libraries Government Documents Department

Fast neutron capture cross sections of /sup 169/Tm, /sup 191/Ir, /sup 193/Ir, and /sup 175/Lu for 3 less than or equal to E/sub n/ less than or equal to 2000 keV

Description: Fast-neutron capture cross sections of /sup 169/Tm, /sup 191/Ir, /sup 193/Ir, and /sup 175/Lu are presented in tabular form for neutron energies between 3 and 2000 keV. 1 table.
Date: August 1, 1978
Creator: Macklin, R.L.; Drake, D.M. & Malanify, J.J.
Partner: UNT Libraries Government Documents Department

Neutron cross section programs in the energy region from 1 to 24 MeV at the LASL Van de Graaff Facilities

Description: Neutron measurements relevant to the Los Alamos Scientific Laboratory's (LASL) programmatic efforts and to the U.S. fission and fusion energy programs can be divided into four categories: secondary neutron emission cross sections on light elements, gamma-ray production cross sections, total cross sections on light isotopes, and (n,2n) and (n,3n) cross sections. Many of these measurements were performed using the unusual capabilities of the LASL's Van de Graaffs. This is especially true for the high energy (greater than or equal to 20 MeV) measurements on (n,2n) and (n,3n) cross sections. One describes briefly the four types of measurements, to illustrate each measurement with some examples, and to present any new data that are not as yet available in the literature. One also indicates in which programs new measurements are planned for the next year.
Date: January 1, 1977
Creator: Auchampaugh, G. F.; Drake, D. M. & Veeser, L. R.
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

E2 isovector giant resonance as seen through the capture of fast neutrons

Description: The forward-to-backward asymmetry of high-energy photons, emitted in the radiative capture of neutrons with energies up to 20 MeV, was measured for /sup 208/Pb. The asymmetry increases abruptly from small values to large ones near E..gamma.. approx. 23 MeV, supporting the location in that neighborhood of the E2 giant isovector resonance.
Date: November 1, 1981
Creator: Drake, D.M.; Aniol, K.; Halpern, I.; Joly, S.; Nilsson, L.; Storm, D. et al.
Partner: UNT Libraries Government Documents Department

Double differential neutron emission cross sections of /sup 10/B and /sup 11/B at 6, 10 and 14 MeV and of /sup 6/Li, /sup 7/Li and /sup 12/C at 14 MeV

Description: Neutron emission spectra of /sup 10/B and /sup 11/B were measured at 6, 10, and 14.1 MeV and those of /sup 6/Li, /sup 7/Li and carbon at 14.1 MeV using time-of-flight technique. Absolute double differential cross sections were obtained by using scattering from hydrogen as a cross section reference. Integration over energy ranges and solid angle yielded integrated elastic and total neutron emission cross sections. At 6 and 10 MeV excellent agreement with total cross section data is found, at 14.1 MeV the new data tend to be higher than expected. The biggest error source in the continuous spectra stems from uncertainties in the input library (ENDF/B-IV) of the Monte Carlo correction for multiple scattering. In particular, the library for /sup 11/B appears to be very unrealistic, with a total elastic cross section at 14.1 MeV which should be higher by 50%.
Date: January 1, 1985
Creator: Drosg, M.; Lisowski, P.W.; Hardekopf, R.A.; Drake, D.M. & Treitl, K.
Partner: UNT Libraries Government Documents Department

Differential cross sections of the reaction /sup 4/He(t,n)/sup 6/Li between 8. 5 and 16. 5 MeV and the n-/sup 6/Li cross-section standard

Description: Differential cross sections of the reaction /sup 4/He(t,n)/sup 6/Li, including some data of the first and second excited states of /sup 6/Li, were measured and compared with an R-matrix analysis of previous data in the /sup 7/Li system. Excellent agreement is observed for the angular distribution at the 0.24-MeV resonance of n-/sup 6/Li, and the shape of the angular distribution for /sup 4/He(t,n/sub 1/)/sup 6/Li at 12.9 MeV is predicted qualitatively by the R-matrix analysis. However, for neutron energies greater than 0.5 MeV for /sup 6/Li(n,t)/sup 4/He the zero-degree excitation function is consistently lower (about 30%) in the R-matrix analysis.
Date: January 1, 1982
Creator: Drosg, M.; Drake, D.M.; Hardekopf, R.A. & Hale, G.M.
Partner: UNT Libraries Government Documents Department

Cross sections for neutron-producing reactions induced by 14. 1 MeV neutrons incident on /sup 6/Li, /sup 7/Li, /sup 10/B, /sup 11/B, and carbon

Description: Using the time-of-flight technique, we have measured neutron emission spectra for /sup 6/Li, /sup 7/Li, /sup 10/B, /sup 11/B and carbon at an incident neutron energy of 14.1 MeV and at 10 angles between 30/degree/ and 143/degree/. Double differential cross sections and their integrated values have been extracted and are presented in tables and graphs. The nonelastic portion of the neutron emission spectra is noticeably higher than expected which may be due to uncertainties in the input library (ENDF/B-IV) used in the Monte Carlo correction for multiple scattering. In particular, the library for /sup 11/B appears to be very unrealistic with an integrated elastic cross section which should be higher by 50%. 20 refs., 1 fig., 12 tabs.
Date: October 1, 1988
Creator: Drosg, M.; Lisowski, P.W.; Drake, D.M.; Hardekopf, R.A. & Muellner, M.
Partner: UNT Libraries Government Documents Department

H(t,n)/sup 3/He reaction for depth profiling of hydrogen by neutron time-of-flight

Description: The cross section for the H(t,n) reaction is large (200 to 700 mb/sr at 0/sup 0/) and smoothly varying. The usefulness of this reaction for depth profiling hydrogen in solids was investigated using the pulsed T/sup +/ beam from the Los Alamos vertical Van de Graaff. Neutron spectra from targets of Ti and TiH/sub 2/ with a nominal thickness of ten microns were compared with targets of SiO/sub 2/, C and Au to assess the importance of neutron backgrounds from triton reactions with the constituents of those targets. A 2.54-cm-diameter by 2.54-cm-thick stilbene neutron detector was placed at 0/sup 0/ 5.35 meters from the target. Pulse shape discrimination virtually eliminated gamma-ray background. When the neutron spectra were transformed into profiles, the background corrected TiH/sub 2/ spectrum showed a uniform hydrogen concentration over ten microns. In the experimental geometry used, a measurement of the neutron spectrum produced when bombarding an Au target (on which (t,n) reactions are strongly inhibited by the Coulomb barrier) yields a background equivalent to a concentration of 3 at.% of hydrogen in Ti. This background is due to reactions on hydrogen, hydrocarbons, or other light nuclei on or in beam line components. Equivalent hydrogen atomic concentrations (in Ti) calculated from neutron spectra measured on the other targets were: SiO/sub 2/-11 at.%, Si-7 at.%, C-22 at.%, Ti-5 at.%. Development of high sensitivity for depth profiling hydrogen with this technique appears possible only for high Z host materials and will require careful attention to beam line and vacuum system design.
Date: June 1, 1977
Creator: Davis, J. C.; Lefevre, H. W.; Poppe, C. H.; Drake, D. M. & Veeser, L. R.
Partner: UNT Libraries Government Documents Department

H(t,n)/sup 3/He reaction for depth profiling of hydrogen by neutron time-of-flight

Description: The usefulness of the H(t,n) reaction for depth profiling of hydrogen in solids was investigated using the pulsed T/sup +/ beam from the Los Alamos vertical Van de Graaff. A 2.54 cm diameter by 2.54 cm thick stilbene neutron detector was placed at 0/sup 0/, 5.35 meters from the target. Pulse shape discrimination virtually eliminated gamma-ray background. Neutron spectra from targets of Ti and TiH/sub 2/ with a nominal thickness of ten microns were compared with targets of SiO/sub 2/, Si, C and Au to assess the importance of neutron backgrounds from triton reactions with the constituents of those targets. When the neutron spectra were transformed into profiles, the background corrected TiH/sub 2/ spectrum showed a uniform hydrogen concentration over ten microns. A measurement of the neutron spectrum produced when bombarding an Au target on which (t,n) reactions are strongly inhibited by the Coulomb barrier gives a yield equivalent to a background concentration of 3 at.% of hydrogen in Ti. This background is due to reactions on hydrogen, hydrocarbons, or other light nuclei on or in beam line components. Similar measurements on other targets gave background values equivalent to hydrogen atomic concentrations in Ti of: SiO/sub 2/-11 at.%, Si-7 at.%, C-22 at.%, Ti-5 at.%. Development of high sensitivity for depth profiling hydrogen with this technique appears possible only for high Z host materials and will require careful attention to beam line and vacuum system design.
Date: June 1, 1977
Creator: Davis, J. C.; Lefevre, H. W.; Poppe, C. H.; Drake, D. M. & Veeser, L. R.
Partner: UNT Libraries Government Documents Department

Double-differential beryllium neutron cross sections at incident neutron energies of 5. 9, 10. 1, and 14. 2 MeV. [5. 9 to 14. 2 MeV, differential cross sections, ENDF/B-IV]

Description: Beryllium neutron-production cross sections were measured using the time-of-flight technique at incident neutron energies of 5.9, 10.1, and 14.2 MeV, and at laboratory angles of 25, 27.5, 30, 35, 45, 60, 80, 100, 110, 125, and 145/sup 0/. The differential elastic and inelastic cross sections are presented. Inelastic is defined here as those reactions that proceed through the states at 1.69-, 2.43-, 2.8-, and 3.06-MeV excitation energy in /sup 9/Be. Comparison of emission energy spectra with calculations using the ENDF/B-IV beryllium cross sections shows that the ENDF/B cross sections strongly overemphasize the low lying states in /sup 9/Be.
Date: August 1, 1976
Creator: Drake, D. M.; Auchampaugh, G. F.; Arthur, E. D.; Ragan, C. E. & Young, P. G.
Partner: UNT Libraries Government Documents Department

Cross sections for neutron-induced neutron-producing reactions in /sup 6/Li and /sup 7/Li at 5. 96 and 9. 83 MeV

Description: Time-of-flight techniques were used to measure the /sup 6/Li and /sup 7/Li neutron emission spectra at incident neutron energies of 5.96 and 9.83 MeV and at 10 angles from 25/sup 0/ to 144/sup 0/. Differential elastic and inelastic cross sections as well as continuum cross sections that result from three-body breakup and inelastic scatering from unresolved states are presented. 10 figures, 5 tables.
Date: October 1, 1980
Creator: Lisowski, P.W.; Auchampaugh, G.F.; Drake, D.M.; Drosg, M.; Haouat, G.; Hill, N.W. et al.
Partner: UNT Libraries Government Documents Department