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Photoneutron reaction cross sections for 75As and 181Ta: Systematical uncertainties and data reliabilityтезисы доклада
- Авторы: Varlamov V., Davydov A., Ishkhanov B., Kaidarova V., Orlin V.
- Сборник: International Conference on Nuclear Data for Science and Technology, May 19-24, 2019, Beijing, China. Conerence Program & Abstract Book
- Тезисы
- Год издания: 2019
- Место издания: China Nuclear Data Center Beijing, China
- Первая страница: 144
- Последняя страница: 144
- Аннотация: There is the old problem of noticeable disagreements between photonuclear cross sections data obtained in various experiments. The most well-known once is that of significant systematic disagreements between cross sections for partial reactions (g, 1n) and (g, 2n), obtained at Livermore (UDSA) and Saclay (France) using beams of quasimonoenergetic annihilation photons and the method of photoneutron multiplicity sorting. The ratios S/L of integrated cross sections for 19 nuclei from 51V to 239U, investigated in both laboratories, are changed from 0.69 to 1.34 wherein averaged values are equal to 0.84 for (g, 2n) and 1.07 for (g, 1n) reactions. It means that as a rule the (g, 1n) reaction cross sections are larger at Saclay, but (g, 2n) reaction cross sections, vice versa, at Livermore. There are two very interesting cases – 75As, for which S/L ratios for both partial reactions are very close (1.22 and 1.21) and 181Ta for which those ratios are significantly different (0.89 and 1.25). Partial reaction cross-section data for both nuclei were analyzed using the objective physical data reliability criteria, SIGMAeval(g, in) = FithSIGMAexp(g, Sn) = [SIGMAth(g, in)/SIGMAth(g, Sn)]SIGMAexp(g, Sn), (1). It was found that there are serious doubts in reliability of Saclay data for both nuclei and both partial reactions. At the same time it was shown that correspondent Livermore data are in general definitely unreliable. Using the experimental-theoretical method for reliable partial reaction cross section SIGMAexp(g, Sn),(2) where SIGMAexp(g, Sn) = SIGMAexp[(g, 1n)+2(g, 2n)+3(g, 3n)+…] is rather independent from the experimental neutron multiplicity sorting problems because all outgoing neutrons are included, the new partial reaction cross sections satisfying data reliability criteria were evaluated. Using the comparison in detail of evaluated cross sections with experimental once it was shown that the main reason of definite unreliability of Livermore data is erroneous normalization of results of measurements in the cases of both nuclei and in addition the loss of many neutrons from the (g, 1n) reaction in the case of 181Ta. In general the reason of unreliability Saclay and Livermore data is erroneous sorting of photoneutrons between “1n” and “2n” channels. The newly reliable evaluated cross-section data 75As and 181Ta disagree with experimental data obtained at both Livermore and Saclay. The evaluated data for 181Ta agree with data obtained bremsstrahlung and activation method. The work is supported by the Research Contract 20501 of the IAEA Coordinated Research Project No F41032.
- Добавил в систему: Варламов Владимир Васильевич