Nuclear reactions of 48Ti, 56Fe, 57Fe, 58Ni, 60Ni, 63Cu, and 65Cu by 12-GeV protons.

Abstract

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 \ensuremath{\gamma}-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${\ensuremath{\pi}}^{+}$), 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\ensuremath{\le}x\ensuremath{\le}9 revealed strong target dependence. The average N/Z ratio of reaction products for x\ensuremath{\simeq}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.