New 209Bi photodisintegration and physical criteria of data reliabilityтезисы доклада

Дата последнего поиска статьи во внешних источниках: 11 ноября 2019 г.

Работа с тезисами доклада


[1] New 209bi photodisintegration and physical criteria of data reliability / S. Belyshev, A. Davydov, D. Filipescu et al. // International Conference on Nuclear Data for Science and Technology, May 19-24, 2019, Beijing, China. Conerence Program & Abstract Book. — China Nuclear Data Center Beijing, China, 2019. — P. 232–232. The well-known problem of noticeable disagreements between the photoneutron cross sections obtained in various experiments was discussed for 209Bi using objective physical data reliability criteria. Data for partial photoneutron reactions (g, 1n), (g, 2n), and (g, 3n) cross sections obtained before for many nuclei using quasimonoenergetic annihilation photon beams and the method of neutron multiplicity sorting at Livermore (USA) and Saclay (France) were analyzed using experimental-theoretical method based on SIGMAexp[(g, 1n)+2(g, 2n)+3(g, 3n)+… rather independent from the neutron multiplicity sorting problem was decomposed into the partial reaction cross sections, SIGMAeval(g, in) = FithSIGMAexp(g, Sn) = [SIGMAth(g, in)/SIGMAth(g, Sn)]SUGMAexp(g, Sn), (1) using the transitional neutron multiplicity functions, Fith = SIGMAth(g, in)/SIGMAth(g, Sn), (2) calculated within the framework of the Combined Model of Photonuclear Reactions for the partial reactions (g, in) with definite neutron multiplicity factors i = 1, 2, 3, ... .It was shown that because of significant systematic uncertainties of the method for determination of neutron multiplicity experimental data do not satisfy criteria of reliability and differ noticeably from the evaluated data. At the same time it was shown for 181Ta, 196Au and 209Bi evaluated data are near the data obtained using bremsstrahlung beams and activation method. To investigate the problem of data reliability in detail the evaluated data for (g, 1n), (g, 2n), (g, 3n), and (g, 4n) cross sections for 209Bi were compared with the new experimental data obtained using monochromatic laser Compton scattering γ-ray beam and novel technique of direct neutron-multiplicity sorting with a flat-efficiency detector. Photoneutron cross-section measurements were performed for 209Bi(γ, xn) reactions with x = 1–4 using LCS γ–ray beams at the NewSUBARU synchrotron radiation facility. A flat response neutron detector with the detection efficiency of 36.5 ± 1.6% over a neutron energy range 0.01–5.00 MeV was developed by optimizing triple-ring configurations of 3He proportional counters embedded in a polyethylene moderator block. It was shown that for all four partial reactions mentioned above the new experimental Fiexp data are in good agreement with Fith data and therefore the correspondent experimental cross sections are reliable. The work is supported by the Research Contracts of the IAEA Coordinated Research Project No F41032.

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