The Prompt Fission Neutron Spectrum (PFNS) Measurement Program at LANSCE

Haight, R. C.; Lee, Hye Young; Taddeucci, T.N.; O’Donnell, J. M.; Perdue, B. A.; Fotiades, N.; Devlin, M.; Ullmann, J. L.; Laptev, A.; Jändel, M.; Nelson, R. O.; Wender, S. A.; White, Morgan Curtis; Wu, C. Y.; Kwan, E.; Chyzh, A.; Henderson, R.; Gostic, J. M.

doi:10.1016/j.nds.2014.08.057

Cited by 16 publications

(13 citation statements)

References 5 publications

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“…These measurements were made as part of the "Chi-Nu" project, and the experiments have been partially described previously in, for example, Refs. [19][20][21]. Preliminary results, particularly for the lower-energy part of the PFNS for 235 U, have also been reported previously; the results reported here are of a less preliminary nature, and should supersede the prior reported values.…”

Section: Introductionsupporting

confidence: 79%

Prompt Fission Neutron Spectra for Neutron-Induced Fission of ²³⁹Pu and ²³⁵U

et al. 2020

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We report the current results of a large effort to accurately measure the Prompt Fission Neutron Spectra (PFNS) for neutron-induced fission of 235U and 239Pu for incident neutrons with energies from 1 to 20 MeV. The Chi-Nu experiment at the Los Alamos Neutron Science Center used an unmoderated, white spectrum of neutrons to induce fission in actinide samples that were placed inside a parallel plate avalanche counter to provide a fast fission signal. A double time-of-flight technique was used to determine the incoming and outgoing neutron energies. Two neutron detector arrays, one with 54 liquid scintillators and another with 22 lithium glass detectors, were used to detect the outgoing neutrons and measure the PFNS distributions over a wide range in outgoing neutron energy, from below 100 keV to 10 MeV. Extensive Monte Carlo modeling was used to understand the experiment response and extract the PFNS. Systematic errors and uncertainties in the method have been examined and quantified. A summary of these results for incoming energies from 1 to 5 MeV is presented here.

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Section: Introductionsupporting

confidence: 79%

Prompt Fission Neutron Spectra for Neutron-Induced Fission of ²³⁹Pu and ²³⁵U

et al. 2020

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“…The Los Alamos National Laboratory Chi-Nu array [41], consisting of 54 17.78 cm diameter by 5.08 cm thick cylindrical EJ-309 scintillators coupled to 12.7 cm diameter photomultiplier tubes (Hamamatsu R4144), was used to measure neutrons and photons from 252 Cf(sf). In this work, because of the number of data channels available in the electronics, only 45 of the detectors were used.…”

Section: A Experimentsmentioning

confidence: 99%

Measured and simulated Cf(sf)252 prompt neutron-photon competition

et al. 2018

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Neutrons and photons are characteristically emitted during the nuclear fission process when a deformed, neutron-rich nucleus divides into two fragments that then de-excite. During de-excitation, neutrons are emitted first, followed by photons; this process gives rise to correlated emissions. Few data exist on event-by-event neutron-photon correlation. In this work, 252 Cf(sf) neutron and photon correlations were measured with an array of 45 liquid organic scintillation detectors and a fission chamber. The measured correlations are compared with MCNPX − PoliMi simulations using the built-in model and two event-by-event fission models, CGMF and FREYA, which predict correlations in prompt emissions from fission. Experimental results suggest weak neutron-photon competition during fragment de-excitation.

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“…The present experiment has been described previously [9][10][11][12]. Briefly, the principal elements are (1) the WNR/LANSCE unmoderated, pulsed spallation neutron source [13] on the 4FP15Left beam line, (2) a new target area centered 21.5 meters from the source with walls at least 3 meters from the center, (3) a fast parallel plate avalanche detector (PPAC) containing 10 separate PPAC modules with approximately 10 mg of 239 Pu in each module [14], (4) an array of neutron detectors to detect fission neutrons, and (5) a data acquisition system based on waveform digitizers.…”

Section: Methodsmentioning

confidence: 99%

The LANL/LLNL Prompt Fission Neutron Spectrum Program at LANSCE and Approach to Uncertainties

Haight

Lee

et al. 2015

Nuclear Data Sheets

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New data on the prompt fission neutron spectra (PFNS) from neutron-induced fission with higher accuracies are needed to resolve discrepancies in the literature and to address gaps in the experimental data. The Chi-Nu project, conducted jointly by LANL and LLNL, aims to measure the shape of the PFNS for fission of 239 Pu induced by neutrons from 0.5 to 20 MeV with accuracies of 3-5% in the outgoing energy from 0.1 to 9 MeV and 15% from 9 to 12 MeV and to provide detailed experimental uncertainties. Neutrons from the WNR/LANSCE neutron source are being used to induce fission in a Parallel-Plate Avalanche Counter (PPAC). Two arrays of neutron detectors are used to cover the energy range of neutrons emitted promptly in the fission process. Challenges for the present experiment include background reduction, use of 239 Pu in a PPAC, and understanding neutron detector response. Achieving the target accuracies requires the understanding of many systematic uncertainties. The status and plans for the future will be presented.

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The Prompt Fission Neutron Spectrum (PFNS) Measurement Program at LANSCE

Cited by 16 publications

References 5 publications

Prompt Fission Neutron Spectra for Neutron-Induced Fission of ²³⁹Pu and ²³⁵U

Prompt Fission Neutron Spectra for Neutron-Induced Fission of ²³⁹Pu and ²³⁵U

Measured and simulated Cf(sf)252 prompt neutron-photon competition

The LANL/LLNL Prompt Fission Neutron Spectrum Program at LANSCE and Approach to Uncertainties

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The Prompt Fission Neutron Spectrum (PFNS) Measurement Program at LANSCE

Cited by 16 publications

References 5 publications

Prompt Fission Neutron Spectra for Neutron-Induced Fission of 239Pu and 235U

Prompt Fission Neutron Spectra for Neutron-Induced Fission of 239Pu and 235U

Measured and simulated Cf(sf)252 prompt neutron-photon competition

The LANL/LLNL Prompt Fission Neutron Spectrum Program at LANSCE and Approach to Uncertainties

Contact Info

Product

Resources

About

Prompt Fission Neutron Spectra for Neutron-Induced Fission of ²³⁹Pu and ²³⁵U

Prompt Fission Neutron Spectra for Neutron-Induced Fission of ²³⁹Pu and ²³⁵U