Download or read book FY07 LDRD Final Report Neutron Capture Cross Section Measurements at DANCE written by and published by . This book was released on 2008 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have measured neutron capture cross sections intended to address defense science problems including mix and the Quantification of Margins and Uncertainties (QMU), and provide details about statistical decay of excited nuclei. A major part of this project included developing the ability to produce radioactive targets. The cross-section measurements were made using the white neutron source at the Los Alamos Neutron Science Center, the detector array called DANCE (The Detector for Advanced Neutron Capture Experiments) and targets important for astrophysics and stockpile stewardship. DANCE is at the leading edge of neutron capture physics and represents a major leap forward in capability. The detector array was recently built with LDRD money. Our measurements are a significant part of the early results from the new experimental DANCE facility. Neutron capture reactions are important for basic nuclear science, including astrophysics and the statistics of the [gamma]-ray cascades, and for applied science, including stockpile science and technology. We were most interested in neutron capture with neutron energies in the range between 1 eV and a few hundred keV, with targets important to basic science, and the s-process in particular. Of particular interest were neutron capture cross-section measurements of rare isotopes, especially radioactive isotopes. A strong collaboration between universities and Los Alamos due to the Academic Alliance was in place at the start of our project. Our project gave Livermore leverage in focusing on Livermore interests. The Lawrence Livermore Laboratory did not have a resident expert in cross-section measurements; this project allowed us to develop this expertise. For many radionuclides, the cross sections for destruction, especially (n, [gamma]), are not well known, and there is no adequate model that describes neutron capture. The modeling problem is significant because, at low energies where capture reactions are important, the neutron reaction cross sections show resonance behavior or follow 1/v of the incident neutrons. In the case of odd-odd nuclei, the modeling problem is particularly difficult because degenerate states (rotational bands) present in even-even nuclei have separated in energy. Our work included interpretation of the [gamma]-ray spectra to compare with the Statistical Model and provides information on level density and statistical decay. Neutron capture cross sections are of programmatic interest to defense sciences because many elements were added to nuclear devices in order to determine various details of the nuclear detonation, including fission yields, fusion yields, and mix. Both product nuclei created by (n,2n) reactions and reactant nuclei are transmuted by neutron capture during the explosion. Very few of the (n, [gamma]) cross sections for reactions that create products measured by radiochemists have ever been experimentally determined; most are calculated by radiochemical equivalences. Our new experimentally measured capture cross sections directly impact our knowledge about the uncertainties in device performances, which enhances our capability of carrying out our stockpile stewardship program. Europium and gadolinium cross sections are important for both astrophysics and defense programs. Measurements made prior to this project on stable europium targets differ by 30-40%, which was considered to be significantly disparate. Of the gadolinium isotopes, 151Gd is important for stockpile stewardship, and 153Gd is of high interest to astrophysics, and nether of these (radioactive) gadolinium (n, [gamma]) cross sections have been measured. Additional stable gadolinium isotopes, including {sup 157,160}Gd are of interest to astrophysics. Historical measurements of gadolinium isotopes, including {sup 152,154}Gd, had disagreements similar to the 30-40% disagreements found in the historical europium data. Actinide capture cross section measurements are important for both Stockpile Stewardship and for nuclear forensics. We focused on the {sup 242m}Am(n, [gamma]) measurement, as there was no existing capture measurement for this isotope. The cross-section measurements (cross section vs. E{sub n}) were made at the Detector for Advanced Neutron Capture Experiments. DANCE is comprised of a highly segmented array of barium fluoride (BaF2) crystals specifically designed for neutron capture-gamma measurements, using small radioactive targets (less than one milligram). A picture of half the array, along with a photo of one crystal, is shown in Fig. 1. DANCE provides the world's leading capability for measurements of neutron capture cross sections with radioactive targets. The DANCE is a 4[pi] calorimeter and uses the intense spallation neutron source the Lujan Center at the Los Alamos National Laboratory. The detector array consists of 159 barium fluoride crystals arranged in a sphere around the target.
Download or read book Neutron Capture Cross Sections of Molybdenum Tantalum and U 238 Final Report written by and published by . This book was released on 1970 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Absolute Measurement of Neutron Cross Sections Progress Report written by and published by . This book was released on 1981 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The procedures and status of the absolute measurement of the neutron capture cross sections for 115In and 232Th are described. Work on the 239Pu fission fragment anisotropy and absolute measurement of the fast neutron fission cross section for 233U are briefly described. Progress in establishing the 14 MeV neutron measurements at the facility are discussed. (WHK).
Download or read book Neutron Capture Cross Section Measurement on Pu at DANCE written by and published by . This book was released on 2011 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: The proposed neutron capture measurement for 238Pu was carried out in Nov-Dec, 2010, using the DANCE array at LANSCE, LANL. The total beam-on-target time is about 14 days plus additional 5 days for the background measurement. The target was prepared at LLNL with the new electrplating cell capable of plating the 238Pu isotope simultaneously on both sides of the 3-?m thick Ti backing foil. A total mass of 395?g with an activity of 6.8 mCi was deposited onto the area of 7 mm in diameter. The 238Pu sample was enriched to 99.35%. The target was covered by 1.4?m double-side aluminized mylar and then inserted into a specially designed vacuum-tight container, shown in Fig. 1, for the 238Pu containment. The container was tested for leaks in the vacuum chamber at LLNL. An identical container without 238Pu was made as well and used as a blank for the background measurement.
Download or read book Measurement of Neutron Penetration Standards written by A. D. Carlson and published by . This book was released on 1969 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Neutron Capture Cross Section Measurement Techniques written by and published by . This book was released on 1975 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book NEUTRON CROSS SECTION MEASUREMENTS Summary Report March 1 1968 February 28 1969 written by and published by . This book was released on 1969 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Neutron Capture Measurements on 157Gd and 89Y at DANCE written by Andrii Chyzh and published by . This book was released on 2009 with total page 115 pages. Available in PDF, EPUB and Kindle. Book excerpt: Keywords: photo strength functions, neutron resonance, gadolinium, radiative neutron capture, Los Alamos, DANCE, cross section, yttrium.
Download or read book Neutron Capture Cross section Measurements from 01 to 3 MeV written by M. Lindner and published by . This book was released on 1974 with total page 117 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fast Neutron Cross Section Measurements Progress Report written by and published by . This book was released on 1992 with total page 41 pages. Available in PDF, EPUB and Kindle. Book excerpt: From its inception, the Nuclear Data Project at the University of Michigan has concentrated on two major objectives: (1) to carry out carefully controlled nuclear measurements of the highest possible reliability in support of the national nuclear data program, and (2) to provide an educational opportunity for students with interests in experimental nuclear science. The project has undergone a successful transition from a primary dependence on our photoneutron laboratory to one in which our current research is entirely based on a unique pulsed 14 MeV fast neutron facility. The new experimental facility is unique in its ability to provide nanosecond bursts of 14 MeV neutrons under conditions that are ''clean'' and as scatter-free as possible, and is the only one of its type currently in operation in the United States. It has been designed and put into operation primarily by graduate students, and has met or exceeded all of its important initial performance goals. We have reached the point of its routine operation, and most of the data are now in hand that will serve as the basis for the first two doctoral dissertations to be written by participating graduate students. Our initial results on double differential neutron cross sections will be presented at the May 1993 Fusion Reactor Technology Workshop. We are pleased to report that, after investing several years in equipment assembly and optimization, the project has now entered its ''data production'' phase.
Download or read book Neutron Capture Cross Section Measurements by the Missing Flux Technique written by Kevin W. Bruening and published by . This book was released on 1983 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Neutron Capture Cross Sections from Surrogate Measurements written by and published by . This book was released on 2009 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Neutron Capture Cross Section Measurements and Resonance Parameters written by E. Haddad and published by . This book was released on 1966 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fast Neutron Cross Section Measurements Final Technical Report March 1 1987 September 30 1995 written by and published by . This book was released on 1997 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt: The time-of-flight technique was used with the ring scattering geometry in a laboratory with low neutron scattering background to measure the angular distributions of the cross sections for elastic and inelastic scattering of 14 MeV neutrons in natural chromium, iron, nickel, and niobium. Specifically for inelastic scattering included were: the 1.43 MeV and 4.56 MeV levels of 52Cr, the 0.85 MeV level, and (2.94-3.12) MeV and (4.46-4.51) MeV level groups of 56Fe, the 1.33 MeV level of 6°Ni combined with the 1.45 MeV level of 58Ni, and the 4.48 MeV level of 58Ni. Pulses of neutrons with time width of 0.9-1.1 ns were produced via the 3H(d, n)4He reaction in a 150 keV Cockcroft-Walton linear accelerator, with average intensities of 9x108 n/s. The energy of the incident neutrons was between 14.75 MeV (at 16°) and 13.48 MeV (at 160°). High purity scattering ring samples were used. The scattering angles ranged from (almost equal to)16° to (almost equal to)150°, for iron, chromium, and nickel, and from (almost equal to)16° to (almost equal to)160° for niobium, with a typical step of (almost equal to)10°. High purity ring samples were used.
Download or read book Neutron Capture Cross Section on Lu Isotopes at DANCE written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The DANCE (Detector for Advanced Neutron Capture Experiments) array at the LANSCE spallation neutron source in Los Alamos has been used to measure neutron capture cross sections for 175Lu and 176Lu with neutron energies from thermal up to 100 keV. Both isotopes are of current interest for the s-process nucleosynthesis. 175Lu is an important waiting-point in the s-process and 176Lu is a sensitive s-process thermometer. Three targets were used to perform these measurements. One was a natural Lu foil of 31 mg/cm2 and the other two were isotopically enriched targets of 175Lu (99.8%, ≈1 mg/cm2 electro-deposited on Ti) and 176Lu (99.9%, ≈1 mg/cm2 mass separator deposited on aluminized mylar). The data analysis is in progress. Preliminary cross sections have been obtained by normalizing the data to the known thermal cross section. A comparison of these data with recent experimental data of K. Wisshak et al. and the evaluated data of ENDF B-VII will be presented.
Download or read book Measuring Neutron Capture with DANCE written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Precision Neutron Cross Section Measurements in Support of the LMFBR Program Progress Report for January 1 1975 December 31 1975 written by and published by . This book was released on 1975 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Research progress is reported for the following projects: (1) the neutron total cross section of sodium near minimum, (2) $sup 238$U(n, $gamma$) measurements with Fe-filtered neutron TOF beams, (3) neutron capture and transmission measurements on $sup 101$Ru, $sup 102$Ru, $sup 104$Ru, $sup 145$Nd, and $sup 149$Sm, (4) capture cross section normalization and analysis of $sup 101$Ru, $sup 10$$sub 2$, $sup 104$Ru, $sup 145$Nd, $sup 149$Sm, (5) neutron capture and transmission experiments on $sup 95$Mo, $sup 97$Mo, $sup 133$Cs, and $sup 143$Nd, (6) capture cross section measurements of radioactive fission products, and (7) neutron capture and transmission data analysis system. (SDF).
