Neutron activation cross sections on lead isotopes

The cross sections for the reactions ${}^{204}\mathrm{Pb}(n,n^{\prime }\gamma ){}^{204}\mathrm{Pb}{}^m$, ${}^{204}\mathrm{Pb}(n,2n){}^{203}\mathrm{Pb}$, ${}^{204}\mathrm{Pb}(n,2n){}^{203}\mathrm{Pb}{}^{m1}$, ${}^{204}\mathrm{Pb}(n,3n){}^{202}\mathrm{Pb}{}^m$, ${}^{206}\mathrm{Pb}(n,3n){}^{204}\mathrm{Pb}{}^m$, ${}^{206}\mathrm{Pb}(n,\alpha ){}^{203}\mathrm{Hg}$, and ${}^{208}\mathrm{Pb}(n,p){}^{208}\mathrm{Tl}$ were determined at the IRMM van de Graaff laboratory in the neutron energy range from 14 to 21 MeV. Both natural and enriched samples were irradiated with neutrons produced via the ${}^3\mathrm{H}(d,n){}^4\mathrm{He}$ reaction. The induced activities were determined by gamma-ray spectrometry using a HPGe detector in a low-background shield. Neutron fluences were determined with the well-known cross section of the ${}^{27}\mathrm{Al}(n,\alpha ){}^{24}\mathrm{Na}$ reaction. Enriched samples were essential to determine the cross sections for the reactions with ${}^{204}\mathrm{Pb}{}^m$ and ${}^{206}\mathrm{Pb}{}^m$ isomers in the final state. Accurate results for reactions with ${}^{204,206}\mathrm{Pb}$ as target nuclei with natural lead samples were enabled through a precise measurement of the isotopic ratios. For a first investigation of the consequences of the present data for nuclear reaction models they were confronted with calculations based on global parameter systematics in a phenomenological and in a microscopic approach and with parameters selected to reproduce the available data. The TALYS code was used for the former two calculations involving parameter systematics while the STAPRE code was used for the latter calculation.

Figure 1

Experimental results for the charged particle emission reactions compared with results from earlier measurements and the TALYS and STAPRE model calculations.

Figure 2

Experimental results for the neutron emission reactions compared with results from earlier measurements and the TALYS and STAPRE model calculations.