Measurement of the 
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 prompt fission neutron spectrum from 10 keV to 10 MeV induced by neutrons of energy from 1 MeV to 20 MeV

Kelly, K. J.; Gomez, J. A.; Devlin, M.; O’Donnell, J. M.; Neudecker, Denise; Lovell, A. E.; Haight, R. C.; Wu, C. Y.; Henderson, R.; Kawano, Toshihiko; Bennett, E. A.; Mosby, S.; Ullmann, J. L.; Fotiadis, Nikolaos; Henderson, J.; Taddeucci, T.N.; Lee, H. Y.; Talou, P.; White, Morgan Curtis

doi:10.1103/physrevc.105.044615

Cited by 13 publications

(3 citation statements)

References 30 publications

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“…The second source of nuclear data uncertainties relates to the fact that nuclear data are frequently used for many corrections to χ s . One example is that nuclear data are used in neutron-transport codes to calculate m. This nuclear-data-related uncertainty source was estimated in only rare cases [40,41,72]. This uncertainty amounted to values of 0.1-5% for Chi-Nu data.…”

Section: Nuclear-data Uncertaintiesmentioning

confidence: 99%

“…Chapter III.M of reference [1], (b) the detailed uncertainty analysis [7][8][9] of several 235,238 U and 239 Pu PFNS experimental data using their respective literature and EXFOR entries [35][36][37], as well as (c) uncertainty studies undertaken by the Chi-Nu team as part of their measurement campaign [13,[38][39][40][41][42][43]. After the initial establishment of the templates, a sub-set of the authors reviewed 252 Cf PFNS measurements; some of the knowledge, gained from references [6,[44][45][46], was added to this manuscript.…”

Section: Introductionmentioning

confidence: 99%

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Templates of expected measurement uncertainties for prompt fission neutron spectra

Neudecker,

Devlin,

Haight

et al. 2023

EPJ Nuclear Sci. Technol.

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In this paper, we provide templates of uncertainty sources expected to appear for three measurement types of prompt fission neutron spectra (PFNS): (1) shape measurements, (2) clean-ratio shape, that is the monitor PFNS are measured in nearly exactly the same surrounding as the PFNS of interest, and (3) indirect ratios, where the detector efficiency is backed out from PFNS monitor measurements. Information is also listed that is needed to faithfully include PFNS in nuclear data evaluations to guide experimenters on how to best report data and metadata for their measurements. These templates also suggest a typical range of pertinent uncertainty values and their correlations in case realistic uncertainties cannot be estimated from information on the measurement itself. The templates were based on a literature review, information found in EXFOR for 252Cf, 235, 238U, and 239Pu PFNS, and enhanced by expertise from experimenters contributing to these PFNS templates.

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Section: Nuclear-data Uncertaintiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Templates of expected measurement uncertainties for prompt fission neutron spectra

Neudecker,

Devlin,

Haight

et al. 2023

EPJ Nuclear Sci. Technol.

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show abstract

“…Today, experiment has advanced dramatically compared to those early days, and measured data are used to calibrate and guide theoretical treatments. For example, recent measurement campaigns have been undertaken by experimentalists at Los Alamos, Livermore, and Bruyeres-le-Chatel [21][22][23][24][25]; see the review in this issue [6].…”

Section: Bethe's Calculationsmentioning

confidence: 99%

Manhattan Project 1940s research on the prompt fission neutron spectrum

Chadwick

Capote²

2023

Front. Phys.

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We describe how the prompt fission neutron spectrum (PFNS) was determined for the Manhattan Project at Los Alamos. Early work before World War II at American and British universities is described, together with theoretical work by Feather at Cambridge and Bethe at Los Alamos. As the Manhattan Project was being planned in 1942, two experiments on natural uranium were commissioned that proved to be influential: 1) An integral experiment at Chicago by Christy and Manley that accurately determined the average PFNS spectrum energy, 2.2 ± 0.2 MeV; 2) Bloch and Staub’s Stanford cyclotron measurement of the PFNS spectrum, which obtained an average energy of 1.70 ± 0.34 MeV. These two papers, previously unavailable outside of Los Alamos, are reproduced in the Supplementary Appendix. From these data, at the beginning of the project in 1943 Serber estimated an average 235U PFNS energy of 2 MeV, and indeed this agrees with today’s best estimate. The challenges facing the scientists involved both the availability of only very small samples of enriched uranium and plutonium targets, and fast neutron detection technologies. During the project, 235U and 239Pu PFNS were measured by Nicodemus and Staub. These also proved to be quite accurate and gave an average spectrum energy of 2 MeV for 235U. [This is not reproduced in the Appendix because it was published after the war in Physical Review 89, 1288 (1953)]. New methods were developed to enable more accurate measurements, and this paper describes how the PFNS was determined surprisingly well by 1945. We end by describing the post-war measurements in the 50s, including the PFNS data used by Ford and Wheeler in their simulations in 1951, the Bonner 1952 data, the seminal 1952 Watt paper with a new empirical parametrization of the PFNS, and the accurate PFNS measurement undertaken at Los Alamos by Cranberg et al. in 1956. We compare the measurements with our best understanding today as embodied in the Evaluated Nuclear Data File ENDF/B-VIII.0. Some images from historical documents in our Los Alamos National Security Research Center (NSRC) archives are shown.

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The impact of detection rate changes and correlations on random-coincidence background measurements

Kelly

O’Donnell

Gomez

et al. 2023

Nuclear Instruments and Methods in Physics Research Section A:

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Measurement of the U235(n,f) prompt fission neutron spectrum from 10 keV to 10 MeV induced by neutrons of energy from 1 MeV to 20 MeV

Cited by 13 publications

References 30 publications

Templates of expected measurement uncertainties for prompt fission neutron spectra

Templates of expected measurement uncertainties for prompt fission neutron spectra

Manhattan Project 1940s research on the prompt fission neutron spectrum

The impact of detection rate changes and correlations on random-coincidence background measurements

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