Cross sections for neutron capture from surrogate measurements: An examination of Weisskopf-Ewing and ratio approximations

Abstract

Motivated by the renewed interest in the surrogate nuclear reactions approach, an indirect method for determining compound-nuclear reaction cross sections, the prospects for determining (n,γ) cross sections for deformed rare-earth and actinide nuclei are investigated. A nuclear-reaction model is employed to simulate physical quantities that are typically measured in surrogate experiments and used to assess the validity of the Weisskopf-Ewing and ratio approximations, which are typically employed in the analysis of surrogate reactions. The expected accuracy of (n,γ) cross sections extracted from typical surrogate measurements is discussed and limitations of the approximate methods are illustrated. Suggestions for moving beyond presently-employed approximations are made.

Spin differences in the Zr90 compound nucleus induced by (p,p′) , Ota1, Burke2, Casperson3 et al. 2015Phys. Rev. C233280View full textAdd to dashboardCite

“…While this has a smaller effect on the extraction of fission cross sections [9], the γ-ray emission of the compound nucleus can be quite sensitive to the initial J π distribution [14,15,[17][18][19][20][21]. Therefore, in order to extract (n, γ) cross sections from surrogate data it becomes necessary to take into account the J π distribution of the decaying compound nucleus.…”

“…While the applicability of the surrogate reaction approach has been successfully demonstrated for (n, f ) cross sections (e.g. * ota2@llnl.gov [8][9][10][11][12][13]), it has been difficult to determine (n, γ) cross sections (e.g., [14][15][16]). …”

87Y(n,γ) and89,90Zr(n,γ) cross sections from a surrogate reaction approach

“…These are contaminant peaks from the 92,94,96 Zr targets. Also, some peaks from the 12 C and 16 O are seen in the lower energy. These contaminant peaks are entirely removed after the correction.…”

“…While the applicability of the surrogate reaction approach has been demonstrated for (n,f) cross sections [8][9][10][11][12], it has been difficult to determine (n,J) cross sections due primarily to the discrepancy in the spin-parity distributions of the compound nucleus created by the (n,J) and the surrogate reaction [13][14][15][16][17]. However, some recent research showed promise for inferring (n,J) cross sections by accounting for spin-parity distribution of the compound nucleus [18].…”

Current Status of Nuclear Physics Research

“…Transfer reaction methods as the ones described above are form a kind of surrogate reactions in which the neutron is carried along by a nucleus to react with a target [353,354]. An example of surrogate reactions are (d,p) reactions, which exploits the simplicity of the deuteron structure.…”