Measurement of high-energy prompt gamma-rays from neutron induced fission of U-235

Makii, H.; Nishio, K.; Hirose, K.; Orlandi, R.; Léguillon, R.; Ogawa, Tatsuhiko; Söldner, T.; Hambsch, F.‐J.; Astier, A.; Pollitt, Andrew; Petrache, C. M.; Tsekhanovich, I.; Mathieu, L.; Aïche, M.; Frost, R.J.W.; Czájkowski, S.; Guo, Song; Köster, U.

doi:10.1051/epjconf/201714604036

“…60 Therefore, it is important to evaluate the potential contribution of γ-rays to the observed NC scintillation. The calculated γ-ray attenuation cross sections σ γ-ray of the NCs scintillator materials, averaged with respect to the prompt gamma ray spectrum of 235 U, 5,61 range from 0.14 cm 2 /g in CuInS 2 to 0.28 cm 2 /g for FAPbBr 3 and CsPbBr 3 (Table 1), consistent with the photon stopping power provided by the high Pb content of the latter compounds. The attenuation coefficients a γ-ray of these NC samples, which account for the concentration by dividing by the NC density in the colloidal solution, vary from 0.2 × 10 −3 cm −1 for the more dilute CsPbBrCl 2 :Mn NCs to 9.8 × 10 −3 cm −1 for the more concentrated CsPbBr 3 NCs (Table 1).…”

Section: Resultssupporting

confidence: 65%

Fast Neutron Imaging with Semiconductor Nanocrystal Scintillators

McCall

¹

,

Sakhatskyi

²

,

Lehmann

³

et al. 2020

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Fast neutrons offer high penetration capabilities for both light and dense materials due to their comparatively low interaction cross sections, making them ideal for the imaging of large-scale objects such as large fossils or as-built plane turbines, for which X-rays or thermal neutrons do not provide sufficient penetration. However, inefficient fast neutron detection limits widespread application of this technique. Traditional phosphors such as ZnS:Cu embedded in plastics are utilized as scintillators in recoil proton detectors for fast neutron imaging. However, these scintillation plates exhibit significant light scattering due to the plastic−phosphor interface along with long-lived afterglow (on the order of minutes), and therefore alternative solutions are needed to increase the availability of this technique. Here, we utilize colloidal nanocrystals (NCs) in hydrogen-dense solvents for fast neutron imaging through the detection of recoil protons generated by neutron scattering, demonstrating the efficacy of nanomaterials as scintillators in this detection scheme. The light yield, spatial resolution, and neutron-vs-gamma sensitivity of several chalcogenide (CdSe and CuInS 2 )-based and perovskite halide-based NCs are determined, with only a short-lived afterglow (below the order of seconds) observed for all of these NCs. FAPbBr 3 NCs exhibit the brightest total light output at 19.3% of the commercial ZnS:Cu(PP) standard, while CsPbBrCl 2 :Mn NCs offer the best spatial resolution at ∼2.6 mm. Colloidal NCs showed significantly lower gamma sensitivity than ZnS:Cu; for example, 79% of the FAPbBr 3 light yield results from neutron-induced radioluminescence and hence the neutron-specific light yield of FAPbBr 3 is 30.4% of that of ZnS:Cu(PP). Concentration and thickness-dependent measurements highlight the importance of increasing concentrations and reducing self-absorption, yielding design principles to optimize and foster an era of NC-based scintillators for fast neutron imaging.

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“…60 Therefore, it is important to evaluate the potential contribution of γ-rays to the observed NC scintillation. The calculated γ-ray attenuation cross sections σ γ-ray of the NCs scintillator materials, averaged with respect to the prompt gamma ray spectrum of 235 U, 5,61 range from 0.14 cm 2 /g in CuInS 2 to 0.28 cm 2 /g for FAPbBr 3 and CsPbBr 3 (Table 1), consistent with the photon stopping power provided by the high Pb content of the latter compounds. The attenuation coefficients a γ-ray of these NC samples, which account for the concentration by dividing by the NC density in the colloidal solution, vary from 0.2 × 10 −3 cm −1 for the more dilute CsPbBrCl 2 :Mn NCs to 9.8 × 10 −3 cm −1 for the more concentrated CsPbBr 3 NCs (Table 1).…”

Section: Acs Nano Wwwacsnanoorgsupporting

confidence: 64%

“…The blocking experiment implemented for the spatial resolution provides a modulated light yield due to neutron and gamma attenuation of the metal blocks, thus the ratio R b of the light intensity in the blocked and unblocked regions can be used to estimate the gamma sensitivity. This ratio can be expressed as Gamma attenuation coefficients of the metal blocks were averaged with respect to the 235 U γ-ray spectrum, 61 while the fast neutron attenuation coefficients were estimated using the calculated neutron fission spectrum. 11 Note that these values will overestimate the neutron stopping power due to the lower average energy of the calculated fission neutron spectrum (1.…”

Section: Acs Nano Wwwacsnanoorgmentioning

confidence: 99%

Fast Neutron Imaging with Semiconductor Nanocrystal Scintillators

Sakhatskyi

¹

,

Bodnarchuk

²

,

Lehmann

³

et al. 2021

Proceedings of the Internet NanoGe Conference on Nanocrystals

0

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Fast neutrons offer high penetration capabilities for both light and dense materials due to their comparatively low interaction cross sections, making them ideal for the imaging of large-scale objects such as large fossils or as-built plane turbines, for which X-rays or thermal neutrons do not provide sufficient penetration. However, inefficient fast neutron detection limits widespread application of this technique. Traditional phosphors such as ZnS:Cu embedded in plastics are utilized as scintillators in recoil proton detectors for fast neutron imaging. However, these scintillation plates exhibit significant light scattering due to the plastic−phosphor interface along with long-lived afterglow (on the order of minutes), and therefore alternative solutions are needed to increase the availability of this technique. Here, we utilize colloidal nanocrystals (NCs) in hydrogen-dense solvents for fast neutron imaging through the detection of recoil protons generated by neutron scattering, demonstrating the efficacy of nanomaterials as scintillators in this detection scheme. The light yield, spatial resolution, and neutron-vs-gamma sensitivity of several chalcogenide (CdSe and CuInS 2 )-based and perovskite halide-based NCs are determined, with only a short-lived afterglow (below the order of seconds) observed for all of these NCs. FAPbBr 3 NCs exhibit the brightest total light output at 19.3% of the commercial ZnS:Cu(PP) standard, while CsPbBrCl 2 :Mn NCs offer the best spatial resolution at ∼2.6 mm. Colloidal NCs showed significantly lower gamma sensitivity than ZnS:Cu; for example, 79% of the FAPbBr 3 light yield results from neutron-induced radioluminescence and hence the neutron-specific light yield of FAPbBr 3 is 30.4% of that of ZnS:Cu(PP). Concentration and thickness-dependent measurements highlight the importance of increasing concentrations and reducing self-absorption, yielding design principles to optimize and foster an era of NC-based scintillators for fast neutron imaging.

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“…Delayed γ lines starting from the prompt γ peak can also be seen, and are associated with isomeric decays of particular fission fragments, e.g., 1769 keV γ line with lifetime 54 ns can be a candidate for 146 Ce [23]. Other lines originate from neutron inelastic scattering (n, n ′ γ ) on materials inside the detectors, e.g., γ -ray decay of the first excited states of 139 La (165.86 keV), 79 Br (217.07 keV), and 81 Br (275.99 keV), or materials close to the γ detectors and the ionization chamber, e.g., γ -ray decay of the first excited states of 27 Al (843.76 keV) and 56 Fe (846.78 keV). A continuous γ background exists along the whole axis associated with uncorrelated decays in FIG.…”

Section: B Pfg Selectionmentioning

confidence: 99%

“…The latter cover a wide range of energies from a few tens keV up to 10 MeV. At even higher energies, the deexcitation of giant resonance (GR) of the fragments may be observed [26,27]. In the case of fast-neutron-induced fission, where the cross section is three orders of magnitude lower than thermal-neutron-induced fission, the limited statistics above 6 MeV constrain the study of high-energy γ rays (see Fig.…”

Section: Emission Spectrum Shapementioning

confidence: 99%

Statistical study of the prompt-fission γ -ray spectrum for U238(n, f ) in the fast-neutron region

Qi

¹

,

Lebois

²

,

Wilson

³

et al. 2018

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Prompt-fission γ -ray spectra (PFGS) have been measured for the 238 U(n, f ) reaction using fast neutrons produced by the LICORNE directional neutron source. Fission events were detected with an ionization chamber containing actinide samples placed in the neutron beam, and the coincident prompt-fission γ rays were measured using a number of LaBr 3 scintillation detectors and a cluster of nine phoswich detectors from the PARIS array. Prompt-fission γ rays (PFGs) were discriminated from prompt-fission neutrons using the time-of-flight technique over distances of around 35 cm. PFG emission spectra were measured at two incident neutron energies of 1.9 and 4.8 MeV for 238 U(n, f )andalsofor 252 Cf (sf ) as a reference. Spectral characteristics of PFG emission, such as mean γ multiplicity and average total γ -ray energy per fission, as well as the average γ -ray energy, were extracted. The sensitivity of these results to the width of the time window and the type of spectral unfolding procedure used to correct for the detector responses was studied. Iteration methods were found to be more stable in low-statistics data sets. The measured values at E n = 1.9 MeV were found to be the mean γ multiplicity M γ = 6.54 ± 0.19, total released energy per fission E γ,tot = 5.25 ± 0.20 MeV, and the average γ -ray energy ǫ γ = 0.80 ± 0.04 MeV. Under similar conditions, the values at E n = 4.8 MeV were measured to be M γ = 7.31 ± 0.46, E γ,tot = 6.18 ± 0.65 MeV, and ǫ γ = 0.84 ± 0.11 MeV.

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Measurement of high-energy prompt gamma-rays from neutron induced fission of U-235

Cited by 6 publications

References 17 publications

Fast Neutron Imaging with Semiconductor Nanocrystal Scintillators

Fast Neutron Imaging with Semiconductor Nanocrystal Scintillators

Fast Neutron Imaging with Semiconductor Nanocrystal Scintillators

Statistical study of the prompt-fission γ -ray spectrum for U238(n, f ) in the fast-neutron region

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