SYSTEMATICS OF ANGULAR DISTRIBUTIONS AND THICK-TARGET RECOIL PROPERTIES OF DEEP SPALLATION AND FRAGMENTATION PRODUCTS OF HIGH-ENERGY PROTON REACTIONS
Abstract
Angular distributions and thick-target recoil properties of deep spallation and fragmentation products of the interaction of silver, lanthanum, terbium and lutetium with multi-GeV protons have been measured. The angular distributions can be characterized by two parameters, A$\sb 1$ and A$\sb 2$, which determine the asymmetry and the anisotropy, respectively. The thick-target results yield the values of the mean product kinetic energies and, combined with the data of angular distributions, those of the velocity of the remnant, $\beta\sb{/\!/}$. The systematics of these quantities are examined both for these and other targets, ranging from silver to uranium. With the exception of light fragments (A $<$ 30), both A$\sb 1$ and A$\sb 2$ decrease with increasing mass loss, $\Delta$A, and become negative for sufficiently large $\Delta$A. The corresponding laboratory angular distribution peaks shift from forward to sideward angles with increasing $\Delta$A. The deviation of the very light fragments supports the idea that the formation of light fragments (A $<$ A$\sb{\rm T}$/3) may involve a multi-fragment breakup process. The kinetic energies increase linearly with the fractional mass loss, $\Delta$A/A$\sb{\rm T}$ up to a value of $\sim$2/3. The deviation for larger $\Delta$A/A$\sb{\rm T}$ suggests a change in mechanism from deep spallation to fragmentation for products with a mass less than $\sim$A$\sb{\rm T}$/3. Contrary to the expectation from the two-step model, the $\beta\sb{/\!/}$ do not scale with $\Delta$A/A$\sb{\rm T}$.
Degree
Ph.D.
Subject Area
Nuclear chemistry
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