Nuclear reactions ofTi48,Fe56,Fe57,Ni58,Ni60,Cu63, andCu65by 12-GeV protons

Formation cross sections of product nuclides in the nuclear reactions of enriched isotope targets, ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ti}$, ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$, ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{63}{}_{}{}^{}\mathrm{Cu}$, and ${}_{}{}^{65}{}_{}{}^{}\mathrm{Cu}$, by 12-GeV protons were measured with the γ-ray spectroscopy. The measured spallation cross sections were used to obtain the charge-dispersion relation by the least-squares analysis. The present data cover a broader range of the N/Z ratio of the target, (N/Z${)}_T$, from 1.071 to 1.241. The N/Z ratio at the charge-dispersion peak, (N/Z${)}_P$, was found to be consistent with that obtained previously using natural targets in the same mass region. The (N/Z${)}_P$ value for ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ was determined to be 1.110 that is appreciably larger than the (N/Z${)}_T$ value of 1.071. This result seems to contradict a simple statistical interpretation of spallation reactions in terms of the nuclear cascade-evaporation process without including nuclear effects of the target nucleus. Cross sections for (p,capture), (p,p${\pi }^{+}$), and (p,xpyn) reactions were determined unambiguously from the present data. Most of (p,pyn) and (p,2pyn) reactions did not show any noticeable target effect, whereas (p,xpyn) reactions for 3≤x≤9 revealed strong target dependence. The average N/Z ratio of reaction products for x≃7 was found to be consistent with the (N/Z${)}_P$ results of the charge-dispersion analysis. Emission of neutrons depends strongly upon the target nucleus. The A dependence of (N/Z${)}_P$ was estimated.