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Title: Determination of the effective sample thickness via radiative capture

Our procedure for determining the effective thickness of non-uniform irregular-shaped samples via radiative capture is described. In this technique, partial γ-ray production cross sections of a compound nucleus produced in a neutron-capture reaction are measured using Prompt Gamma Activation Analysis and compared to their corresponding standardized absolute values. For the low-energy transitions, the measured cross sections are lower than their standard values due to significant photoelectric absorption of the γ rays within the bulk-sample volume itself. Using standard theoretical techniques, the amount of γ-ray self absorption and neutron self shielding can then be calculated by iteratively varying the sample thickness until the observed cross sections converge with the known standards. The overall attenuation provides a measure of the effective sample thickness illuminated by the neutron beam. This procedure is illustrated through radiative neutron capture using powdered oxide samples comprising enriched 186W and 182W from which their tungsten-equivalent effective thicknesses are deduced to be 0.077(3) mm and 0.042(8) mm, respectively.
 [1] ;  [2] ;  [3] ;  [1] ;  [1] ;  [2] ;  [2]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. Hungarian Academy of Sciences, Budapest (Hungary)
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0168-583X
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Nuclear Instruments and Methods in Physics Research. Section B, Beam Interactions with Materials and Atoms
Additional Journal Information:
Journal Volume: 362; Journal ID: ISSN 0168-583X
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
Country of Publication:
United States
71 CLASSICAL AND QUANTUMM MECHANICS, GENERAL PHYSICS Prompt Gamma Activation Analysis (PGAA); gamma-ray absorption; neutron attenuation; (n, γ) radiative capture; partial gamma-ray production cross sections