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Photoneutron reaction cross sections and physical criteria of data reliabilityтезисы доклада
- Авторы: Ishkhanov B.S., Peskov N.N., Orlin V.N., Stepanov M.E., Varlamov V.V.
- Сборник: The International Conference “Nuclear Structure and Related Topics”, July 14 – 18, 2015, Dubna, Russia. Book of Abstracts
- Тезисы
- Год издания: 2015
- Место издания: JINR Dubna
- Первая страница: 43
- Последняя страница: 44
- Аннотация: The traditional studies of the photonuclear reaction cross sections explore roles of different types of nuclear excitations in photoabsorption and their coupling to collective nuclear degrees of freedom, competition of different final states and different mechanisms in the exit channels of the reactions. Moreover, data on cross sections for partial photoneutron reactions are widely used in various realms of science and technologies (nuclear physics and nuclear power engineering; radiation chemistry, geology, and medicine; materials science; ecology; monitoring luminosities of colliding beams of relativistic nuclei in accelerators and many other fields). Majority of data under discussion were obtained using quasimonoenergetic annihilation photons and methods of neutron multiplicity sorting at Livermore (USA) and Saclay (France). Reliability data is doubtful because of presence of noticeable (till 100 %) systematic uncertainties: for many nuclei SIG(g, 1n) are noticeably larger at Saclay but SIG(g, 2n) vice versa at Livermore. Additionally one can see that for many nuclei investigated at Livermore there are many energy ranges in which SIG(g, 1n) have physically forbidden negative values. Using specially introduced objective physical criteria – ratios of partial/yield reaction cross sections Fi = SIG(g, in)/SIG(g, Sn) = SIG(g, in)/[SIG(g,n) + 2SIG(g,2n) + 3SIG(g,3n) + …] – it was shown that in many cases for various nuclei data reliability is doubtful because experimental Fexpi values are larger than the corresponding physical upper limits - 1.00 for F1; F2 – 0.50 for F2; F3 – 0.33 for F3, etc. That means unreliable experimental neutron multiplicity assignment. The approach based on the combined model for photonuclear reactions was proposed for partial photoneutron reaction cross section evaluation free from the neutron multiplicity sorting measurement problems. Evaluations SIGeval(g, in) = Fitheor x SIGexp(g, Sn)of reliable cross sections for partial reactions (g, 1n), (g, 2n) and (g, 3n) were carried out for nuclei 63,65Cu, 80Se, 91,94Zr, 138Ba, 186–192Os, 207Pb, 209Bi in addition to 90Zr, 115In, 112–124Sn, 133Cs, 159Tb, 181Ta, 197Au, 208Pb studied before . New data were compared with some the results of modern induced activity experiments free from neutron multiplicity sorting problems. Deviations of evaluated data from experimental ones were analyzed and many important things for various applications were discussed, many physical effects were overestimated. The work was partially supported by RBFR Grant N 13-02-00124.
- Добавил в систему: Варламов Владимир Васильевич