Measurements with a Pulsed Neutron Source

Beckurts, K. H.

doi:10.13182/nse57-a25417

Cited by 39 publications

(4 citation statements)

References 2 publications

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“…It is apparent from eqs. (39)(40)(41)(42)(43)(44) that the a depend on anisotropic scattering only up to order n. This result is also evident in Table I.…”

Section: $(En) =Y -^^ $^(E)p^(h) (16)supporting

confidence: 57%

“…Early investigations (50,51,43) defined the "thermalization time" by the rate of approach of the average neutron energy to equilibrium, putting E -|/cT -const, e"^^"^…”

Section: Investigations On the Time Dependency Of Neutron Thermalizationmentioning

confidence: 99%

“…Early measurements of the thermalization time were performed by a Russian group (51) and by the author (43). Transmission through silver was used to determine the average neutron energy; the data were analyzed with Eq.…”

Section: On the Thermalization Time Of Graphitementioning

confidence: 99%

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Proceedings of the Brookhaven Conference on Neutron Thermalization, April 30 to May 2, 1962. Volume I. The Scattering Law. Volume Ii. Neutron Spectra in Lattices and Infinite Media. Volume Iii. Experimental Aspects of Transient and Asymptotic Phenomena. Volume Iv. Theoretical Aspects of Transient and Asymptotic Phenomena

1963

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“…It is apparent from eqs. (39)(40)(41)(42)(43)(44) that the a depend on anisotropic scattering only up to order n. This result is also evident in Table I.…”

Section: $(En) =Y -^^ $^(E)p^(h) (16)supporting

confidence: 57%

“…Early investigations (50,51,43) defined the "thermalization time" by the rate of approach of the average neutron energy to equilibrium, putting E -|/cT -const, e"^^"^…”

Section: Investigations On the Time Dependency Of Neutron Thermalizationmentioning

confidence: 99%

See 1 more Smart Citation

Proceedings of the Brookhaven Conference on Neutron Thermalization, April 30 to May 2, 1962. Volume I. The Scattering Law. Volume Ii. Neutron Spectra in Lattices and Infinite Media. Volume Iii. Experimental Aspects of Transient and Asymptotic Phenomena. Volume Iv. Theoretical Aspects of Transient and Asymptotic Phenomena

1963

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“…When SNM is interrogated using a pulsed neutron source, the induced fission signature persists even after the source is turned off. Source neutrons become thermalized in the surrounding material, and their population decays with a characteristic time on the order of a few microseconds [5]. When SNM is present, these thermalized neutrons can induce additional fission events, providing a secondary source of neutrons, which causes the overall population of thermalized neutrons to decay more slowly.…”

Section: Introductionmentioning

confidence: 99%

Discriminating Uranium Isotopes Based on Fission Signatures Induced by Delayed Neutrons

Ogren,

Nattress,

Jovanovic

2019

Preprint

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The use of active interrogation (AI) to induce delayed neutron emission is a well-established technique for the characterization of special nuclear materials (SNM). Delayed neutrons have isotopecharacteristic spectral and temporal signatures, which provide the basis for isotope identification. However, in bulk materials that contain an appreciable fissile (e.g., 235 U or 233 U) fraction, such as highly-enriched uranium (HEU), delayed neutrons have a high probability of inducing additional fissions. As a result, the overall delayed neutron signature consists of two distinct components: the "primary" delayed neutrons (emitted directly by fission fragments), and the "secondary prompt" fission neutrons produced in fission induced by primary delayed neutrons. These prompt products differ from "primary" delayed neutrons both in their energy spectra and in the presence of coincident radiation released by the parent fission event. The presence and relative quantity of prompt products from delayed fission depend on the cross-section of the material in the energy range of delayed neutrons, which may differ significantly between isotopes, thus providing an exploitable means for isotope differentiation. In this work, we demonstrate two experimental approaches for discriminating between 235 U and 238 U isotopes based on the measurement of delayed neutron-induced fission products. First, HEU and depleted uranium objects are differentiated through the detection of highenergy prompt neutrons from delayed fission using both recoil-based organic liquid scintillators and thermalization spectra from a custom-built capture-gated composite detector. Secondly, coincident radiation measurements are used as the basis for discrimination by comparing the overall rates and time evolution of fission events when delayed neutrons are present.

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Thermalization of Neutrons

Beckurts

Wirtz

1964

Neutron Physics

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Measurements with a Pulsed Neutron Source

Cited by 39 publications

References 2 publications

Discriminating Uranium Isotopes Based on Fission Signatures Induced by Delayed Neutrons

Thermalization of Neutrons

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