CONSISTENT EVALUATION OF PHOTONEUTRON REACTION CROSS-SECTIONS USING DATA OBTAINED IN EXPERIMENTS WITH QUASIMONOENERGETIC ANNIHILATION PHOTON BEAMS AT LIVERMORE (USA) AND SACLAY (FRANCE)

Authors & Affiliations

Varlamov V.V., Peskov N.N., Rudenko D.V., Stepanov M.E.
M.V. Lomonosov Moscow State University, D.V. Skobel’tsyn Scientific Research Institute for Nuclear Physics, Centre for Photonuclear Experiment Data, Russia

Abstract

A detailed,systematic analysis of the (γ,xn), (γ,n) and (γ,2n) reaction cross-section data obtained using quasimonoenergetic annihilation photon beams at Livermore (USA) and Saclay (France) was carried out for 19 nuclei (7 initially): 51V, 75As, 89Y, 90Zr, 115In, 116,117,118, 120,124Sn, 127I, 133Cs, 159Tb, 165Ho, 181Ta, 197Au, 208Pb, 232Th, 238U. It was observed that the (γ,xn) reaction cross-section data obtained at both laboratories without using a neutron multiplicity determination procedure disagreed by 10-15%. Additionally, it was found that the disagreement of the (γ,n) and (γ,2n) partial reaction cross-sections obtained at both laboratories using a neutron multiplicity determination procedure was significantly greater (up to 30-40%), and as a rule in different directions. These disagreements were interpreted as being the result of differences in the neutron multiplicity determination procedures used in both laboratories: the procedure at Saclay was incorrect, resulting in the incorrect attribution of part of the (γ,2n) reaction cross-section to the (γ,n) reaction. A special method was used to make the data consistent. This involved recalculating the part of the (γ,n) reaction cross-section determined to be "false" and moving it back to the (γ,2n) reaction cross-section. For all 19 nuclei listed above, the jointly corrected (γ,xn), (γ,n) and (γ,2n) reaction cross-sections were evaluated and prepared for inclusion in the EXFOR nuclear reaction database.

Keywords
(γ,xn), (γ,n),(γ,2n) reaction, cross-section, neutron multiplicity determination procedure, EXFOR nuclear reaction database, 51V, 75As, 89Y, 90Zr, 115In, 116,117,118, 120,124Sn, 127I, 133Cs, 159Tb, 165Ho, 181Ta, 197Au, 208Pb, 232Th, 238U

Article Text (in English, PDF, Translated by IAEA)

References

UDC 539.17

Problems of Atomic Science and Technology. Series: Nuclear Constants", issue 1-2, 2003