Место издания:China Nuclear Data Center Beijing, China
Первая страница:58
Последняя страница:58
Аннотация:Data for partial photoneutron reactions (g, 1n), (g, 2n), and (g, 3n) cross sections obtained for 159Tb using quasimonoenergetic annihilation photon beams and the method of neutron multiplicity sorting at Livermore (USA) and Saclay (France) were analyzed using the objective physical criteria of data reliability, Fi = SIGMA(g, in)/SIGMA(g, Sn). It was shown that both Livermore and Saclay experimental data do not satisfy such criteria.
New data satisfied data those criteria were evaluated using experimental-theoretical method, SIGMAeval(g, in) = FithSIGMAexp(g, Sn) = [SIGMAth(g, in)/SIGMAth(g, Sn)]SIGMAexp(g, Sn)(2). This method means that the experimental neutron yield cross-section, SIGMAexp(g, Sn) = SIGMAexp[(g, 1n)+2(g, 2n)+3(g, 3n)+…(3) rather independent from the experimental neutron multiplicity sorting problems because all outgoing neutrons are included was decomposed into the partial reaction cross sections, using the ratios, Fith calculated within the framework of the Combined Model of Photonuclear Reactions. It was shown [3, 4] that because of significant systematic uncertainties involved in the method for determining the neutron multiplicity, experimental data are noticeably different from the evaluated data. To investigate the problem of data reliability in detail new (g, 1n), (g, 2n), (g, 3n), and (4, 4n) cross sections for 159Tb were obtained using the quasi-monochromatic laser Compton-scattering (LCS) γ-ray beams and the novel technique of direct neutron-multiplicity sorting with a flat-efficiency detector. Photoneutron cross-section measurements were performed using LCS γ–ray beams at the NewSUBARU synchrotron radiation facility. It is shown that for all four partial reactions mentioned above, new experimental cross sections are significantly different from both Livermore and Saclay cross sections. At the same time new cross sections are in good agreement with data evaluated using experimental-theoretical method and data reliability criteria. The work is supported by the Research Contracts (ROM-20476, RUS-20501, JPN-20564) of the IAEA Coordinated Research Project No F41032.