Experimental results on cross sections for 7 Be photoproduction on 12 C, 14 N, and 16 O nuclei in the energy range of 40
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CLEI Experiment
Experimental Results on Cross Sections for 7 Ве Photoproduction on 12 С, 14N, and 16 O Nuclei in the Energy Range of 40–90 MeV A. N. Dovbnua1) , A. S. Deiev1) , V. A. Kushnir1) , V. S. Malyshevsky2)* , T. V. Malykhina3), V. V. Mitrochenko1), S. A. Perezhogin1) , A. V. Torgovkin1), G. V. Fomin2) , and B. I. Shramenko1) Received December 12, 2012; in final form, January 31, 2014
Abstract—The yields of A(γ, X)7 Ве reactions induced by bremsstrahlung photons were measured at the endpoint electron energies of 40, 50, 60, 70, 80, and 90 MeV. The spectra of bremsstrahlung incident to the targets used were calculated via a simulation based on the GEANT 4 code passage. The cross sections for the A(γ, X)7 Ве reactions on 12 С, 14 N, and 16 O nuclei were evaluated on the basis of the measured reaction yields and the calculated bremsstrahlung spectra. The experimental cross sections for the photonuclear reactions of 7 Ве production were compared with their counterparts calculated on the basis of the TALYS 1.4 package. Agreement of the experimental and evaluated results was demonstrated for 12 С nuclei and partly for 14 N nuclei. DOI: 10.1134/S1063778814070059
1. INTRODUCTION Reactions induced by electromagnetic interaction stand out among a wide variety of nuclear reactions. The interaction of low- and intermediate-energy photons are widely used in various realms of science and technologies—from nuclear physics to medicine and materials sciences. In recent years, cross sections for photonuclear reactions have found application in the field of monitoring the content of radionuclides in the near-Earth layer of the atmosphere [1, 2]. To date, it has been found that the radioactivity of air receives a significant contribution from the short-lived isotope 7 Ве of cosmogenic origin. It is commonly believed that dominant reactions leading to the production of beryllium isotopes in the Earth’s atmosphere are induced by the interaction of cosmic rays (protons and neutrons) with nitrogen and oxygen nuclei [3, 4], which are the main component of atmospheric air. The results obtained in [1, 2] reveal that photonuclear reactions may be yet another possible mechanism of the production of the beryllium isotope 7 Be in the upper atmosphere, making a contribution
that is commensurate with the contribution of the proton and neutron mechanisms. In the literature, there are only few data on reactions involving the multiparticle photodissociation of nuclei. For example, the interested reader can find a detailed investigation of the cross section for the reaction 12 C6 (γ, nα)7 Be4 in [5], but there are virtually no data on the reactions 14 N7 (γ, X)7 Be4 and 16 О8 (γ, X)7 Be4 in the literature. Since nitrogen and oxygen nuclei form a dominant component of atmospheric air, these are reactions that are of particular interest for an analysis of the photonuclear mechanism of 7 Ве production in the atmosphere. In contrast to what was done in the previous studies of our group [1, 2], the energy dependence of the yields of A(γ, X)7 Ве react
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