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ISBN 13 :
Total Pages : 8 pages
Book Rating : 4.:/5 (16 download)
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 Determining Neutron Capture Cross Sections with the Surrogate Reaction Technique: Measuring Decay Probabilities with STARS. written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract not provided.
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ISBN 13 :
Total Pages : 14 pages
Book Rating : 4.:/5 (16 download)
Download or read book Neutron-capture Cross Sections from Indirect Measurements written by and published by . This book was released on 2011 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cross sections for compound-nuclear reactions play an important role in models of astrophysical environments and simulations of the nuclear fuel cycle. Providing reliable cross section data remains a formidable task, and direct measurements have to be complemented by theoretical predictions and indirect methods. The surrogate nuclear reactions method provides an indirect approach for determining cross sections for reactions on unstable isotopes, which are difficult or impossible to measure otherwise. Current implementations of the method provide useful cross sections for (n, f) reactions, but need to be improved upon for applications to capture reactions.
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ISBN 13 :
Total Pages : 7 pages
Book Rating : 4.:/5 (16 download)
Download or read book Total Cross Sections as a Surrogate for Neutron Capture written by and published by . This book was released on 2014 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: There are many (n,?) cross sections of great interest to radiochemical diagnostics and to nuclear astrophysics which are beyond the reach of current measurement techniques, and likely to remain so for the foreseeable future. In contrast, total neutron cross sections currently are feasible for many of these nuclides and provide almost all the information needed to accurately calculate the (n,?) cross sections via the nuclear statistical model (NSM). I demonstrate this for the case of 151Sm; NSM calculations constrained using average resonance parameters obtained from total cross section measurements made in 1975, are in excellent agreement with recent 151Sm (n,?) measurements across a wide range of energy. Furthermore, I demonstrate through simulations that total cross section measurements can be made at the Manuel Lujan Jr. Neutron Scattering Center at the Los Alamos Neutron Science Center for samples as small as 10?g. Samples of this size should be attainable for many nuclides of interest. Finally, I estimate that over half of the radionuclides identified 2̃0 years ago as having (n,?) cross sections of importance to s-process nucleosynthesis studies (24/43) and radiochemical diagnostics (11/19), almost none of which have been measured, can be constrained using this technique.
Download or read book Total Cross Sections as a Surrogate for Neutron Capture written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: There are many (n, [gamma]) cross sections of great interest to radiochemical diagnostics and to nuclear astrophysics which are beyond the reach of current measurement techniques, and likely to remain so for the foreseeable future. In contrast, total neutron cross sections currently are feasible for many of these nuclides and provide almost all the information needed to accurately calculate the (n, [gamma]) cross sections via the nuclear statistical model (NSM). I demonstrate this for the case of 151Sm; NSM calculations constrained using average resonance parameters obtained from total cross section measurements made in 1975, are in excellent agreement with recent 151Sm (n, [gamma]) measurements across a wide range of energy. Furthermore, I demonstrate through simulations that total cross section measurements can be made at the Manuel Lujan Jr. Neutron Scattering Center at the Los Alamos Neutron Science Center for samples as small as 10[mu]g. Samples of this size should be attainable for many nuclides of interest. Finally, I estimate that over half of the radionuclides identified ~20 years ago as having (n, [gamma]) cross sections of importance to s-process nucleosynthesis studies (24/43) and radiochemical diagnostics (11/19), almost none of which have been measured, can be constrained using this technique.
Author : R. D. Hoffman
Publisher :
ISBN 13 :
Total Pages : 6 pages
Book Rating : 4.:/5 (316 download)
Download or read book Theoretical Challenges of Determining Low-Energy Neutron Capture Cross Sections Via the Surrogate Technique written by R. D. Hoffman and published by . This book was released on 2004 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cross sections for radiative neutron capture on unstable nuclei at low energies are difficult to calculate with high precision, and can be impossible to measure directly. It is therefore important to explore alternative methods. The prospects of one such method, the Surrogate Nuclear Reaction Technique, is currently being investigated at Lawrence Livermore National Laboratory. The purpose of this paper is to outline the strategy for combining the results from a surrogate experiment with theoretical calculations in order to extract the desired cross section.
Author : David T. Goldman
Publisher :
ISBN 13 :
Total Pages : 730 pages
Book Rating : 4.3/5 (91 download)
Download or read book Neutron Cross Sections and Technology written by David T. Goldman and published by . This book was released on 1968 with total page 730 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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ISBN 13 :
Total Pages : 15 pages
Book Rating : 4.:/5 (893 download)
Download or read book Using 171,173Yb(d, P) to Benchmark a Surrogate Reaction for Neutron Capture written by and published by . This book was released on 2008 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: Neutron capture cross sections on unstable nuclei are important for many applications in nuclear structure and astrophysics. Measuring these cross sections directly is a major challenge and often impossible. An indirect approach for measuring these cross sections is the surrogate reaction method, which makes it possible to relate the desired cross section to a cross section of an alternate reaction that proceeds through the same compound nucleus. To benchmark the validity of using the (d, p[gamma]) reaction as a surrogate for (n, [gamma]), the {sup 171,173}Yb(d, p[gamma]) reactions were measured with the goal to reproduce the known [1] neutron capture cross section ratios of these nuclei.
Author : Donald J. Hughes
Publisher : Elsevier
ISBN 13 : 1483282759
Total Pages : 193 pages
Book Rating : 4.4/5 (832 download)
Download or read book Neutron Cross Sections written by Donald J. Hughes and published by Elsevier. This book was released on 2016-01-22 with total page 193 pages. Available in PDF, EPUB and Kindle. Book excerpt: Neutron Cross Sections presents the principles of cross-section measurement and use, as well as sufficient theory so that the general behavior of cross sections is made understandable. This compilation is a direct result of experiences connected with the collection and evaluation of cross-section data during the past eight years at ""Sigma Centre"", Brookhaven National Laboratory. Here, experimental results received from laboratories throughout the world are carefully evaluated and compiled in the curves and tables of the large volume Neutron Cross Sections, The most recent version of the compilation, known as BNL 325, appeared 1 July 1955, and Supplement 1 to BNL 325 was published on 1 January 1957. The compilation itself consists almost completely of cross sections at specific energies, shown in the form of curves or tables, with only brief explanatory texts. The text opens with discussions of the general properties of cross sections and principles of nuclear structure that are important to the understanding of cross-section behavior. Separate chapters follow that describe specific techniques for measuring cross sections along with experimental results involving fast neutrons, resonance neutrons, resonances in fissionable materials, and thermal neutrons.
Author : D. J. Hughes
Publisher :
ISBN 13 :
Total Pages : 20 pages
Book Rating : 4.3/5 (91 download)
Download or read book Capture Cross Sections for Fast Neutrons written by D. J. Hughes and published by . This book was released on 1949 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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ISBN 13 :
Total Pages : 27 pages
Book Rating : 4.3/5 (91 download)
Download or read book Neutron Cross Sections and Related Measurements written by and published by . This book was released on 1966 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : P. B. Hemmig
Publisher :
ISBN 13 :
Total Pages : 572 pages
Book Rating : 4.E/5 ( download)
Download or read book Conference on Neutron Cross Section Technology written by P. B. Hemmig and published by . This book was released on 1966 with total page 572 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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ISBN 13 :
Total Pages : 4 pages
Book Rating : 4.:/5 (893 download)
Download or read book High-resolution Neutron Capture and Transmission Measurements and the Stellar Neutron Capture Cross Sections of {sup 116,120}Sn written by and published by . This book was released on 1997 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: Improved astrophysical reaction rates for {sup 116,120}Sn(n, [gamma]) are of interest because nucleosynthesis models have not been able to reproduce the observed abundances in this mass region. For example, previous s-process calculations have consistently underproduced the s-only isotope 116Sn. Also, these studies have resulted in residual reprocess abundances for the tin isotopes which are systematically larger than predicted by reprocess calculations. It has been suggested that these problems could be solved by reducing the solar tin abundance by 10-20%, but there is no experimental evidence to justify this renormalization. Instead, it is possible that the problem lies in the (n, T) cross sections used in the reaction network calculations or in the s-process models. One reason to suspect the (n, [gamma]) data is that previous measurements did not extend to low enough energies to determine accurately the Maxwellian-averaged capture cross sections at the low temperatures (kT=6-8 keV) favored by the most recent stellar models of the s process. Also, the two most recent high-precision measurements of the 12°Sn(n, [gamma]) cross section are in serious disagreement. Because of its small size, this cross section could affect (via the s-process branching at 121Sn) the relative abundances of the three s-only isotopes of Te.
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Download or read book High-resolution Neutron Capture and Transmission Measurements and the Stellar Neutron Capture Cross Sections Of[sup 116,120]n written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Improved astrophysical reaction rates for[sup 116,120]Sn(n, [gamma]) are of interest because nucleosynthesis models have not been able to reproduce the observed abundances in this mass region. For example, previous s-process calculations have consistently underproduced the s-only isotope[sup 116]Sn. Also, these studies have resulted in residual reprocess abundances for the tin isotopes which are systematically larger than predicted by reprocess calculations. It has been suggested that these problems could be solved by reducing the solar tin abundance by 10-20%, but there is no experimental evidence to justify this renormalization. Instead, it is possible that the problem lies in the (n, T) cross sections used in the reaction network calculations or in the s-process models. One reason to suspect the (n, [gamma]) data is that previous measurements did not extend to low enough energies to determine accurately the Maxwellian-averaged capture cross sections at the low temperatures (kT=6-8 keV) favored by the most recent stellar models of the s process. Also, the two most recent high-precision measurements of the[sup 120]Sn(n, [gamma]) cross section are in serious disagreement. Because of its small size, this cross section could affect (via the s-process branching at[sup 121]Sn) the relative abundances of the three s-only isotopes of Te.
Author : S Mughabghab
Publisher : Elsevier
ISBN 13 : 0323142354
Total Pages : 847 pages
Book Rating : 4.3/5 (231 download)
Download or read book Neutron Cross Sections written by S Mughabghab and published by Elsevier. This book was released on 2012-12-02 with total page 847 pages. Available in PDF, EPUB and Kindle. Book excerpt: Neutron Cross Sections, Volume 1: Neutron Resonance Parameters and Thermal Cross Sections, Part A represents the fourth edition of what was previously known as BNL-325, Neutron Cross Sections, Volume 1. This three-chapter book provides the extensive list of detailed individual resonance parameters for each isotope. The first chapter deals with the thermal cross sections and average resonance parameters, as well as the physics of thermal and resonance neutrons, with particular emphasis on evaluation methods. This chapter also includes tables of standards of capture cross sections and scattering lengths, and commonly used nuclear physics formulas. The second chapter covers the direct or valence capture and the Brink-Axel treatment of electric dipole radiation. These topics are followed by a discussion on spin-dependent scattering lengths that are of interest to solid state. The third chapter describes the Maxwellian 30-keV capture cross sections that are of importance to studies of nucleosynthesis and age of the universe. This chapter also examines the s- and p-wave average radiative widths and gamma-ray strength functions that are required in capture cross section measurements. This book will appeal to nuclear and astrophysicists.
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ISBN 13 :
Total Pages : 21 pages
Book Rating : 4.:/5 (965 download)
Download or read book Surrogate Measurements of Actinide (n, 2n) Cross Sections with NeutronSTARS. written by and published by . This book was released on 2016 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: Directly measuring (n,2n) cross sections on short-lived actinides presents a number of experimental challenges: scattered beam can produce neutron backgrounds in the detectors, fission can produce a substantial neutron background, and created a target with a short-lived isotope can be extremely difficult. To perform these surrogate (n,2n) cross section measurements, a silicon telescope array has been placed along a beam line at the Texas A & M University Cyclotron Institute, which is surrounded by a large tank of Gadolinium-doped liquid scintillator, which acts as a neutron detector. The combination of the charge-particle and neutron-detector arrays is referred to as NeutronSTARS. In the analysis procedure for calculating the (n,2n) cross section, the neutron detection efficiency and time structure plays an important role. Due to the lack of availability of isotropic, mono-energetic neutron sources, modeling is an important component in establishing this efficiency and time structure. This report describes the NeutronSTARS array, which was designed and commissioned during this project. It also describes the surrogate reaction technique, specifically referencing a 235U(n,2n) commissioning measurement that was fielded during the past year.
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ISBN 13 :
Total Pages : 10 pages
Book Rating : 4.:/5 (727 download)
Download or read book Nuclear Reaction Data from Surrogate Measurements written by and published by . This book was released on 2007 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: A brief summary of the Surrogate reaction method, an indirect approach for determining compound-nuclear reaction cross sections, is presented. The possibilities for obtaining accurate (n, f) cross sections from Surrogate measurements that are analyzed in the Weisskopf-Ewing and Ratio approximations are considered. Theoretical studies and benchmark experiments that provide new insights into the validity and limitations of the Surrogate approach, are discussed.
