Isotope-production cross sections for $p$-, $d$-, and C-induced spallation reactions on ${}^{93}\mathrm{Nb}$ at 113 MeV/nucleon were measured using the inverse-kinematics method employing secondary targets of ${\mathrm{CH}}_2$, ${\mathrm{CD}}_2$, and C. The measured cross sections for ${}^{90}\mathrm{Mo}$, ${}^{90}\mathrm{Nb}$, ${}^{86,88}\mathrm{Y}$ produced by $p$-induced reactions were found to be consistent with those measured by the conventional activation method. We performed benchmark tests of the reaction models INCL-4.6, JQMD, and JQMD-2.0 implemented in the Particle and Heavy Ion Transport code System (PHITS) and of the nuclear data libraries JENDL-4.0/HE, TENDL-2017, and ENDF/B-VIII.0. The model calculations also showed generally good agreement with the measured isotope-production cross sections for $p$-, $d$-, and C-induced reactions. It also turns out that, among the three nuclear data libraries, JENDL-4.0/HE provides the best agreement with the measured data for the $p$-induced reactions. We compared the present ${}^{93}\mathrm{Nb}$ data with the ${}^{93}\mathrm{Zr}$ data, that were measured previously by the same inverse kinematics method (Kawase et al., Prog. Theor. Exp. Phys. 2017, 093D03 (2017)), with particular attention to the effect of neutron-shell closure on isotope production in $p$- and $d$-induced spallation reactions. The isotopic distributions of the measured production cross sections in the ${}^{93}\mathrm{Zr}$ data showed noticeable jumps at neutron number $N=50$ in the isotopic chains of $\mathrm{\Delta }Z=0$ and $-1$, whereas no such jump appeared in isotopic chain of $\mathrm{\Delta }Z=0$ in the ${}^{93}\mathrm{Nb}$ data. From INCL-4.6 $+$ GEM calculations, we found that the jump formed in the evaporation process is smeared out by the intranuclear cascade component in ${}^{91}\mathrm{Nb}$ produced by the ${}^{93}\mathrm{Nb}(p,p2n)$ and $(d,d2n)$ reactions on ${}^{93}\mathrm{Nb}$. Moreover, for ${}^{93}\mathrm{Nb}$, the distribution of the element-production cross sections as a function of the change in proton number $\mathrm{\Delta }Z$ is shifted to smaller $\mathrm{\Delta }Z$ than for ${}^{93}\mathrm{Zr}$, because the excited Nb prefragments generated by the cascade process are more likely to emit protons than the excited Zr prefragments, due to the smaller proton-separation energies of the Nb isotopes.

• Received 18 June 2019

DOI:https://doi.org/10.1103/PhysRevC.100.044605