Measuring the235U ? values at a thermal point

Adamchuk, Yu.V.; Voskanyan, M. A.; Georgiev, Georgi; Kovtun, Anatoly L.; Muradyan, G.V.; Stancheva, N.; Chikov, N.; Yaneva, N.; Shchepkin, Yu.G.

doi:10.1007/bf01122477

Cited by 2 publications

(4 citation statements)

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“…It is remarkable that Beer et al 235 U alpha value of 0.1697 ± 0.0029 is in good agreement with Adamchuk et al data of Ref. [17]. Such agreement is surprising considering that g-factors for fission and capture cross sections evaluated by Westcott [20] are not currently considered to be very accurate despite the very low quoted uncertainties at the time (0.1% for 235 U fission and 0.3% for 239 Pu fission).…”

Section: Additional Data Used In the Combined Fit Of Tnc With Other Ssupporting

confidence: 61%

“…Adamchuk et al [17] measured an alpha value of 0.1690 ± 0.0035 at 0.0253 eV using a neutron beam with a mechanical selector (chopper), but this set was published in 1988 well after the Axton report [10]. However, Axton used data from postirradiation experiments (PIE) by Lounsbury [18] (one year irradiation of samples) and later re-analyzed using Monte Carlo simulations by Beer et al [19].…”

Section: Additional Data Used In the Combined Fit Of Tnc With Other Smentioning

confidence: 99%

“…New measurements of TNC, which can be used in the standards evaluation, have been available since Axton's evaluation. The most important one is the microscopic measurement of the ratio of capture to fission cross section (alpha) for 235 U at 0.0253 eV by Adamchuk et al [17] with 2.1% uncertainty; additionally, there are three measurements of ratio 233 U, 239 Pu and 241 Pu to 235 U at 0.0253 eV done at LANL and CERN n TOF with estimated uncertainties between 2 and 3%.…”

Section: Additional Data Used In the Combined Fit Of Tnc With Other Smentioning

confidence: 99%

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New fit of thermal neutron constants (TNC) for^233,235U,^239,241Pu and²⁵²Cf(sf): Microscopic vs. maxwellian data

et al. 2017

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Abstract. An IAEA project to update the Neutron Standards is near completion. Traditionally, the Thermal Neutron Constants (TNC) evaluated data by Axton for thermal-neutron scattering, capture and fission on four fissile nuclei and the total nu-bar of 252 Cf(sf) are used as input in the combined least-square fit with neutron cross section standards. The evaluation by Axton (1986) was based on a least-square fit of both thermal-spectrum averaged cross sections (Maxwellian data) and microscopic cross sections at 2200 m/s. There is a second Axton evaluation based exclusively on measured microscopic cross sections at 2200 m/s (excluding Maxwellian data). Both evaluations disagree within quoted uncertainties for fission and capture cross sections and total multiplicities of uranium isotopes. There are two factors, which may lead to such difference: Westcott g-factors with estimated 0.2% uncertainties used in the Axton's fit, and deviation of the thermal spectra from Maxwellian shape. To exclude or mitigate the impact of these factors, a new combined GMA fit of standards was undertaken with Axton's TNC evaluation based on 2200 m/s data used as a prior. New microscopic data at the thermal point, available since 1986, were added to the combined fit. Additionally, an independent evaluation of TNC was undertaken using CONRAD code. Both GMA and CONRAD results are consistent within quoted uncertainties. New evaluation shows a small increase of fission and capture thermal cross sections, and a corresponding decrease in evaluated thermal nubar for uranium isotopes and 239 Pu.

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Section: Additional Data Used In the Combined Fit Of Tnc With Other Ssupporting

confidence: 61%

Section: Additional Data Used In the Combined Fit Of Tnc With Other Smentioning

confidence: 99%

Section: Additional Data Used In the Combined Fit Of Tnc With Other Smentioning

confidence: 99%

See 1 more Smart Citation

New fit of thermal neutron constants (TNC) for^233,235U,^239,241Pu and²⁵²Cf(sf): Microscopic vs. maxwellian data

et al. 2017

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“…There are different experimental techniques to tackle this problem. One of them is the γ -ray multiplicity methodology developed in the 1980s [16,17], recently applied by Danon et al [8]. Another is the fission tagging technique [18], used by Jandel et al [7] and in this work.…”

Section: Introductionmentioning

confidence: 99%

Measurement of the α ratio and (n,γ) cross section of U235
Balibrea¹,
Cembranos²,
Cano‐Ott³
et al. 2020
Phys. Rev. C
3
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0
0
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We measured the neutron capture-to-fission cross-section ratio (α ratio) and the capture cross section of 235 U between 0.2 and 200 eV at the n_TOF facility at CERN. The simultaneous measurement of neutron-induced capture and fission rates was performed by means of the n_TOF BaF 2 Total Absorption Calorimeter (TAC), used for detection of γ rays, in combination with a set of micromegas detectors used as fission tagging detectors. The energy dependence of the capture cross section was obtained with help of the 6 Li(n, t) standard reaction determining the n_TOF neutron fluence; the well-known integral of the 235 U(n, f) cross section between 7.8 and 11 eV was then used for its absolute normalization. The α ratio, obtained with slightly higher statistical fluctuations, was determined directly, without need for any reference cross section. To perform the analysis of this measurement we developed a new methodology to correct the experimentally observed effect that the probabilities of detecting a fission reaction in the TAC and the micromegas detectors are not independent. The results of this work have been used in a new evaluation of 235 U performed within the scope of the Collaborative International Evaluated Library Organisation (CIELO) Project, and are consistent with the ENDF/B-VIII.0 and JEFF-3.3 capture cross sections below 4 eV and above 100 eV. However, the measured capture cross section is on average 10% larger between 4 and 100 eV.

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Measuring the235U ? values at a thermal point

Cited by 2 publications

References 1 publication

New fit of thermal neutron constants (TNC) for^233,235U,^239,241Pu and²⁵²Cf(sf): Microscopic vs. maxwellian data

New fit of thermal neutron constants (TNC) for^233,235U,^239,241Pu and²⁵²Cf(sf): Microscopic vs. maxwellian data

Measurement of the α ratio and (n,γ) cross section of U235
Balibrea¹,
Cembranos²,
Cano‐Ott³
et al. 2020
Phys. Rev. C
3
0
0
0
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Measuring the235U ? values at a thermal point

Cited by 2 publications

References 1 publication

New fit of thermal neutron constants (TNC) for233,235U,239,241Pu and252Cf(sf): Microscopic vs. maxwellian data

New fit of thermal neutron constants (TNC) for233,235U,239,241Pu and252Cf(sf): Microscopic vs. maxwellian data

Measurement of the α ratio and (n,γ) cross section of U235Balibrea1, Cembranos2, Cano‐Ott3 et al. 2020Phys. Rev. C3000View full textAdd to dashboardCite

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New fit of thermal neutron constants (TNC) for^233,235U,^239,241Pu and²⁵²Cf(sf): Microscopic vs. maxwellian data

New fit of thermal neutron constants (TNC) for^233,235U,^239,241Pu and²⁵²Cf(sf): Microscopic vs. maxwellian data

Measurement of the α ratio and (n,γ) cross section of U235
Balibrea¹,
Cembranos²,
Cano‐Ott³
et al. 2020
Phys. Rev. C
3
0
0
0
View full text Add to dashboard Cite