Surrogate measurement of the 238Pu(n,f) cross section

Ressler, J. J.; Burke, J. T.; Escher, Jutta; Angell, C. T.; Basunia, M. S.; Beausang, C. W.; Bernstein, L. A.; Bleuel, D. L.; Casperson, R. J.; Goldblum, B. L.; Gostic, J. M.; Hatarik, R.; Henderson, R.; Hughes, R. O.; Munson, J.; Phair, L.; Ross, T. J.; Scielzo, N. D.; Swanberg, E.; Thompson, I. J.; Wiedeking, M.

doi:10.2172/1091370

Cited by 7 publications

(3 citation statements)

References 21 publications

(16 reference statements)

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“…Inelastic scattering with charged light ions is a third type of reaction that has been employed in surrogate reaction measurements [35][36][37][38][39]. From these experiments, as well as from traditional studies of giant resonances [40][41][42], it is known that inelastic scattering can produce a compound nucleus at a wide range of excitation energies.…”

Section: Spin-parity Distributions In Surrogate Reactionsmentioning

confidence: 99%

Cross Sections for Neutron-Induced Reactions from Surrogate Data: Assessing the Use of the Weisskopf-Ewing Approximation for (n,n') and (n,2n) Reactions

Gorton

Escher

2020

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Background: Modeling nuclear reaction networks for nuclear science applications and for simulations of astrophysical environments relies on cross section data for a vast number of reactions, many of which have never been measured. Cross sections for neutron-induced reactions on unstable nuclei are particularly scarce, since they are the most difficult to measure. Consequently, we must rely on theoretical predictions or indirect measurements to obtain the requisite reaction data. For compound nuclear reactions, the surrogate reaction method can be used to determine many cross sections of interest. Purpose: Earlier work has demonstrated that cross sections for neutron-induced fission and radiative neutron capture can be determined from a combination of surrogate reaction data and theory. For the fission case, it was shown that Weisskopf-Ewing approximation, which significantly simplifies the implementation of the surrogate method, can be employed. Capture cross sections cannot be obtained, and require a detailed description of the surrogate reaction process. In this paper we examine the validity of the Weisskopf-Ewing approximation for determining unknown (n, n) and (n, 2n) cross sections from surrogate data. Methods: Using statistical reaction calculations with realistic parametrizations, we investigate first whether the assumptions underlying the Weisskopf-Ewing approximation are valid for (n, n) and (n, 2n) reactions on representative target nuclei. We then produce simulated surrogate reaction data and assess the impact of applying the Weisskopf-Ewing approximation when extracting (n, n) and (n, 2n) cross sections in situations where the approximation is not strictly justified. Results: We find that peak cross sections can be estimated using the Weisskopf-Ewing approximation, but the shape of the (n, n) and (n, 2n) cross sections, especially for low neutron energies, cannot be reliably determined without accounting for the angular-momentum differences between the neutron-induced and surrogate reaction. Conclusions: To obtain reliable (n, n) and (n, 2n) cross sections from surrogate reaction data, a detailed description of the surrogate reaction mechanisms is required. To do so for the compound-nucleus energies and decay channels relevant to these reactions, it becomes necessary to extend current modeling capabilities. I. BACKGROUND AND NEED

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Section: Spin-parity Distributions In Surrogate Reactionsmentioning

confidence: 99%

Cross Sections for Neutron-Induced Reactions from Surrogate Data: Assessing the Use of the Weisskopf-Ewing Approximation for (n,n') and (n,2n) Reactions

Gorton

Escher

2020

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“…A detection system combining silicon telescopes with fission detectors has been used to measure the 238 Pu(n, f ) cross section [7].…”

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confidence: 99%

DEATH-STAR: Silicon and Photovoltaic Fission Fragment Detector Arrays for Light-Ion Induced Fission Correlation Studies

Koglin

Burke

Fisher

et al. 2017

Nuclear Instruments and Methods in Physics Research Section A:

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The Direct Excitation Angular Tracking pHotovoltaic-Silicon Telescope ARray (DEATH-STAR) combines a series of 12 silicon detectors in a ∆E − E configuration for charged particle identification with a large-area array of 56 photovoltaic (solar) cells for detection of fission fragments. The combination of many scattering angles and fission fragment detectors allows for an angular-resolved tool to study reaction cross sections using the surrogate method, anisotropic fission distributions, and angular momentum transfers through stripping, transfer, inelastic scattering, and other direct nuclear reactions. The unique photovoltaic detectors efficiently detect fission fragments while being insensitive to light ions and have a timing resolution of 15.63±0.37 ns. Alpha particles are detected with a resolution of 35.5 keV 1σ at 7.9 MeV. Measured fission fragment angular distributions are also presented.

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“…The surrogate method appears to be a promising technique in that neutron-induced fission cross sections have been obtained using the surrogate ratio method (SRM) for both stable and radioactive nuclei from energies of several hundred keV up to 20 MeV with total uncertainties on the order of 10% or less [1][2][3][4][5][6][7]. This effort was recently expanded to include the determination of neutron capture cross sections.…”

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confidence: 99%

Indirect determination of neutron capture cross sections on spherical and near-spherical nuclei using the surrogate method

et al. 2012

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The 92 Mo(n,γ) cross section was obtained using both the absolute surrogate approach and surrogate ratio method (SRM), relative to the 94 Mo(n,γ) cross section, in an equivalent neutron energy range of 80 to 890 keV. Excited 93 Mo and 95 Mo nuclei were populated using the 92 Mo(d, p) and 94 Mo(d, p) reactions, respectively. Both discrete and statistical tagging approaches were employed to identify the γ-decay channel and were examined in terms of their sensitivity to the initial angular momentum population distribution. The absolute surrogate 92 Mo(n,γ) cross sections disagree with evaluated neutron capture cross section data by as much as a factor of four, whereas the results obtained using the SRM trend more favorably with the evaluated result. Experimental results suggest that discrete and statistical tagging approaches may sample different contributions of the γ-cascade for near-spherical nuclei. This work represents the first use of the surrogate method in the determination of neutron capture cross sections on spherical and quasi-spherical nuclei in the mass-90 region and provides a possible pathway to extend the SRM to a broader mass range.

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Surrogate measurement of the 238Pu(n,f) cross section

Cited by 7 publications

References 21 publications

Cross Sections for Neutron-Induced Reactions from Surrogate Data: Assessing the Use of the Weisskopf-Ewing Approximation for (n,n') and (n,2n) Reactions

Cross Sections for Neutron-Induced Reactions from Surrogate Data: Assessing the Use of the Weisskopf-Ewing Approximation for (n,n') and (n,2n) Reactions

DEATH-STAR: Silicon and Photovoltaic Fission Fragment Detector Arrays for Light-Ion Induced Fission Correlation Studies

Indirect determination of neutron capture cross sections on spherical and near-spherical nuclei using the surrogate method

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