Modern status of photonuclear data
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CLEI Theory
Modern Status of Photonuclear Data V. V. Varlamov1)* and B. S. Ishkhanov1), 2) Received January 18, 2017
Abstract—The reliability of experimental cross sections obtained for (γ, 1n), (γ, 2n), and (γ, 3n) partial photoneutron reactions using beams of quasimonoenergetic annihilation photons and bremsstrahlung is analyzed by employing data for a large number of medium-heavy and heavy nuclei, including those of 63,65 Cu, 80 Se, 90,91,94 Zr, 115 In, 112−124 Sn, 133 Cs, 138 Ba, 159 Tb, 181 Ta, 186−192 Os, 197 Au, 208 Pb, and 209 Bi. The ratios of the cross sections of definite partial reactions to the cross section of the neutronyield reaction, Fi = σ(γ, in)/σ(γ, xn), are used as criteria of experimental-data reliability. By definition, positive values of these ratios should not exceed the upper limits of 1.00, 0.50, 0.33, . . . for i = 1, 2, 3, . . . , respectively. For many nuclei, unreliable values of the above ratios were found to correlate clearly in various photon-energy regions Fi with physically forbidden negative values of cross sections of partial reactions. On this basis, one can conclude that correspondent experimental data are unreliable. Significant systematic uncertainties of the methods used to determine photoneutron multiplicity are shown to be the main reason for this. New partial-reaction cross sections that satisfy the above data-reliability criteria were evaluated within an experimental–theoretical method [σ eval (γ, in) = Fitheor (γ, in) × σ expt (γ, xn)] by employing the ratios Fitheor (γ, in) calculated on the basis of a combined photonuclear-reaction model. It was obtained that cross sections evaluated in this way deviate substantially from the results of many experiments performed via neutron-multiplicity sorting, but, at the same time, agree with the results of alternative activation experiments. Prospects of employing methods that would provide, without recourse to photoneutron-multiplicity sorting, reliable data on cross sections of partial photoneutron reactions are discussed. DOI: 10.1134/S106377881705026X
1. INTRODUCTION Photonuclear reactions play an important role both in basic and applied nuclear-physics studies. The parameters of giant dipole resonances (GDR) observed in cross sections of various photon-induced reactions are of great interest from the point of view of studying nuclear structure and dynamics and nuclear-reaction mechanisms. One employs them in a wide variety of fields, including nuclear physics; nuclear power engineering; astrophysics; radiation sections of chemistry, geology, and medicine; materials science; ecology; and various applied problems, such as monitoring of colliding beams and noninvasive control methods. With the aim of meeting needs for data on various photonuclear reactions, the IAEA Nuclear Reaction Data Centers Network [1], including the SINP (Skobeltsyn Institute of Nuclear Physics) Center for photonuclear experiments data of Lomonosov Moscow State University, created
and maintains the EXFOR international database of nuclear reactions [2], wh
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