Li7(p,n)Be7 cross section from threshold to 1960 keV and precise measurement of the Au197(n,γ) spectrum-averaged cross section at 30 keV

Guido Martín-Hernández, Pierfrancesco Mastinu, Elizabeth Musacchio González, Roberto Capote, Hector Lubián, and Miguel Macías
Phys. Rev. C 99, 034616 – Published 22 March 2019

Abstract

Background: The Li7(p,n)Be7 reaction is one of the most used nuclear reaction for accelerator-based neutron sources. There are few experimental cross section data in the double-value energy region and they are discrepant, as are the reaction yields.

Purpose: We derive the Li7(p,n)Be7 reaction cross section, and measure with small uncertainty the Au197(n,γ)Au198 spectrum-averaged cross section at neutron energy around 30 keV.

Method: By irradiating Li metal targets over the proton energy range of 1879 to 1960 keV, thick target yields were measured using the generated Be7 activity. Based on the theoretical description of the reaction yield, accelerator parameters and reaction cross sections are derived. Gold foils were activated with the neutron field generated by the (p,n) reaction on a Li target at a proton energy of about a half keV above the reaction threshold.

Results: The thick target yield is well reproduced when the Breit-Wigner single-resonance formula for s-wave particles is used to describe the reaction cross section. The ratio between neutron and proton widths was found to be equal to Γn/Γp=5.41Tth/Tp. The detailed balance principle is used to obtain the cosmologically important time-reversed Be7(n,p)Li7 reaction cross section. The measured Au197(n,γ)Au198 spectrum-averaged cross section agrees with the value calculated from the ENDF/B-VIII.0 library.

Conclusions: We demonstrated the feasibility of deriving the Li7(p,n)Be7 reaction cross section from the thick target yield. Using the ratio between neutron and proton widths obtained in this work reduces the uncertainty in calculating the reaction cross section to a factor of 2.3.

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  • Received 15 November 2018

DOI:https://doi.org/10.1103/PhysRevC.99.034616

©2019 American Physical Society

Physics Subject Headings (PhySH)

Accelerators & BeamsNuclear Physics

Authors & Affiliations

Guido Martín-Hernández1, Pierfrancesco Mastinu2, Elizabeth Musacchio González1,2, Roberto Capote3, Hector Lubián1, and Miguel Macías4

  • 1Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear, 30 No. 502 Miramar, La Habana, Cuba
  • 2INFN - Laboratori Nazionali di Legnaro, Viale dell'Universita 2, 35020 Legnaro, Italy
  • 3NAPC-Nuclear Data Section, International Atomic Energy Agency, A-1400 Vienna, Austria
  • 4Universidad de Sevilla, Sevilla, Spain

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Issue

Vol. 99, Iss. 3 — March 2019

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