Место издания:Saint-Petersburg University Saint-Petersburg
Первая страница:110
Последняя страница:110
Аннотация:Experimental data on photodisintegration of a large number of medium and heavy nuclei (91,94,96Zr, 115In, 112–124Sn, 159Tb, 181Ta, 197Au, 208Pb) obtained primarily at Livermore (USA) and Saclay (France) using quasimonoenergetic annihilation photons and the neutron multiplicity sorting based on its energy measurement were analyzed. It was shown that many data under do not satisfy to proposed objective data reliability criteria: in various energy ranges of initial photons the ratios F2 = SIG(g, 2n)/SIG(g, xn) = SIG(g, 2n)/SIG[(g, 1n) + 2(g, 2n) + 3(g, 3n) + …] have physically unreliable values larger 0.50 and at the same time ratios F1 = SIG(g, 1n)/SIG(g, xn) have physically forbidden negative values. That means that experimental neutron multiplicity sorting has been done erroneously because of large systematic uncertainties. A very noticeable disagreements between experimental and physical criteria based cross section energy dependences were found out for 159Tb, 116Sn, 94Zr, 65Cu, 80Se.
Therefore new data free of systematic uncertainties under discussion were evaluated for two isotopes 63,65Cu data obtained at Livermore and 80Se data obtained at Saclay. New experimentally–theoretical method [2] was used for evaluation: – SIG-eval(g, in) = F-theori • SIG-exp(g, xn). It means that competition between partial reactions is in accordance with combined model of photonuclear reactions and their sum SIG-eval(g, xn) is equal to SIG-exp(g, xn) free from neutron multiplicity sorting problems mentioned above.
New cross sections were evaluated for (g, 1n) and (g, 2n) reactions for isotopes 63,65Cu and 80Se. Using evaluated partial reactions cross sections new data for total photoneutron reaction SIG(g, Sn) = SIG[(g, 1n) + (g ,2n) + (g, 3n) + …] were obtained also. Large deviations of evaluated partial reactions cross sections from experimental ones are discussed in details. It is shown that those deviations are the results of unreliable and erroneous redistribution of many neutrons between the channels with multiplicities “1” and “2”.
The work is partially supported by the RFBR Grant 13–02–00124.
