skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Indirect Methods for Nuclear Reaction Data

Abstract

Several indirect approaches for obtaining reaction cross sections are briefly reviewed. The Surrogate Nuclear Reactions method, which aims at determining cross sections for compound-nuclear reactions, is discussed in some detail. The validity of the Weisskopf-Ewing approximation in the Surrogate approach is studied for the example of neutron-induced fission of an actinide nucleus.

Authors:
;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
894793
Report Number(s):
UCRL-PROC-217429
TRN: US0700319
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Conference
Resource Relation:
Conference: Presented at: Perspectives on Nuclear Data in the Next Decade, Bruyere-le-Chatel, France, Sep 26 - Sep 28, 2005
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; ACTINIDES; CROSS SECTIONS; FISSION; NUCLEAR REACTIONS

Citation Formats

Escher, J E, and Dietrich, F S. Indirect Methods for Nuclear Reaction Data. United States: N. p., 2005. Web.
Escher, J E, & Dietrich, F S. Indirect Methods for Nuclear Reaction Data. United States.
Escher, J E, and Dietrich, F S. Fri . "Indirect Methods for Nuclear Reaction Data". United States. doi:. https://www.osti.gov/servlets/purl/894793.
@article{osti_894793,
title = {Indirect Methods for Nuclear Reaction Data},
author = {Escher, J E and Dietrich, F S},
abstractNote = {Several indirect approaches for obtaining reaction cross sections are briefly reviewed. The Surrogate Nuclear Reactions method, which aims at determining cross sections for compound-nuclear reactions, is discussed in some detail. The validity of the Weisskopf-Ewing approximation in the Surrogate approach is studied for the example of neutron-induced fission of an actinide nucleus.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Nov 18 00:00:00 EST 2005},
month = {Fri Nov 18 00:00:00 EST 2005}
}

Conference:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.

Save / Share:
  • Optimum procedures for the statistical improvement, or updating, of an existing nuclear-data evaluation are reviewed and redeveloped from first principles, consistently employing a minimum-variance viewpoint. A set of equations is derived which provides improved values of the data and their covariances, taking into account information from supplementary measurements and allowing for general correlations among all measurements. The minimum-variance solutions thus obtained, which we call the method of ''partitioned least squares,'' are found to be equivalent to a method suggested by Yu. V. Linnik and applied by a number of authors to the analysis of fission-reactor integral experiments; however, up tomore » now, the partitioned-least-squares formulae have not found widespread use in the field of basic data evaluation. This approach is shown to give the same results as the more commonly applied Normal equations, but with reduced matrix inversion requirements. Examples are provided to indicate potential areas of application. 10 refs.« less
  • Standard nuclear reaction methods are limited to treating problems that generalize two-body scattering. These are problems with only one continuous (vector) degree of freedom (CDOF). The difficulty in extending these methods to cases with two or more CDOFs is not just the additional numerical complexity: the mathematical problem is usually not well-posed. It is hard to guarantee that the proper boundary conditions (BCs) are satisfied. Since this is not generally known, the discussion is begun by considering the physics of this problem in the context of coupled-channel calculations. In practice, the difficulties are usually swept under the rug by themore » use of a highly developed phenomenology (or worse, by the failure to test a calculation for convergence). This approach limits the kind of reactions that can be handled to ones occurring on the surface of where a second CDOF can be treated perturbatively. In the past twenty years, the work of Faddeev, the quantum three-body problem has been solved. Many techniques (and codes) are now available for solving problems with two CDOFs. A method for using these techniques in the nuclear N-body problem is presented. A set of well-posed (connected kernal) equations for physical scattering operators is taken. Then it is shown how approximation schemes can be developed for a wide range of reaction mechanisms. The resulting general framework for a reaction theory can be applied to a number of nuclear problems. One result is a rigorous treatment of multistep transfer reactions with the possibility of systematically generating corrections. The application of the method to resonance reactions and knock-out is discussed. 12 figures.« less
  • We discuss nuclear data resources of the National Nuclear Data Center (NNDC) of relevance to nuclear astrophysics applications. These resources include databases, tools and powerful web service at www.nndc.bnl.gov. Our objective is to provide an overview of nuclear databases, related products and demonstrate nuclear astrophysics potential of the ENDF/B-VII beta2 library. A detailed discussion on the Maxwellian neutron capture cross sections obtained from the ENDF/B-VII beta2 library is presented.