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Absolute majority of data on photonuclear, first of all photoneutron, reaction cross sections was obtained in different type experiments carried out using the beams of quasimonoenergetic annihilation photons and the beams of bremsstrahlung [1]. The methods of receiving the information on reaction cross sections are quite different. On the beams of annihilation photons the cross sections of partial reactions (g,1n), (g,2n), (g,3n),… are directly determined and used for obtaining the total photoneutron reaction cross section σ(g,sn) = σ(g,1n) + σ(g,2n) + σ(g,3n) +… and the neutron yield cross section σ(g,xn) = σ(g,1n) + 2σ(g,2n) + 3σ(g,3n) +… . On the beams of bremsstrahlung the neutron yield cross section σ(g,xn) is determined at first and used for obtaining partial reaction cross sections with the aid of statistical theory corrections and correspondent difference procedures. The differences of the methods used are the reasons for significant disagreements between resulted reaction cross sections in both shape and absolute value. It was found out using the objective physical criteria of data reliability Fi = σ(g,in)/σ(g,xn) for more than 50 nuclei investigated on the beams of annihilation photons and about 10 nuclei investigated on the beams of bremsstrahlung that data obtained using both indirect methods for partial reaction separation contain significant systematic uncertainties which resulted in unreliability of data obtained. Newly evaluated reaction cross sections σ-eval(g,in) = Fi-theor x σ-exp(g,xn) for large number of nuclei from 51V up to 209Bi obtained by the experimental-theoretical method basing on the joint using of the experimental neutron yield cross sections σ-exp(g,xn) and the results of Fi-theor calculations in the combined model of photonucleon reactions (CMPNR) [2] are in serious disagreements with the results of both mentioned experimental methods for indirect unreliable separation of partial reactions. At the same time new evaluated data are in agreement with the results of experiments in which the partial reactions (g,1n), (g,2n), (g,3n),… are separated directly and reliably – the activation method on the beam of bremsstrahlung and the method of direct determination on the neutron multiplicity on the beam of photons from laser Compton backscattering of laser radiation on relativistic electrons [3,4].
The research was carried out in the Department of Electromagnetic Processes and Atomic Nuclei Interactions (Centre for Photonuclear Experiments Data) of the MSU SINP.
- IAEA Nuclear Data Section database “EXFOR. Experimental nuclear reaction data”, http://www-nds.iaea.org/exfor.
- B.S.Ishkhanov et al. // Phys. Atom. Nucl. 2008. V.71. P.493.
- V.V.Varlamov et al. // Phys. Atom. Nucl. 2017. V. 80. P.957.
- V.V.Varlamov et al. // Moscow University Physics Bulletin. 2023. V. 78. N. 3. P. 303.
| Section | Experimental and theoretical studies of nuclear reactions |
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