Production of manganese 54 and Zinc 65 from copper in thick targets by 0.45-Gev, 1.0-Gev, and 3.0-Gev protons

Abstract

The production of Mn54 and Zn65 from copper has been measured radiochemically at various depths and radial distances inside thick targets (up to 1 meter in size) that had been irradiated with 0.45-Gev, 1.0-Gev and 3.0-Gev protons. The targets consisted mainly either of copper or of iron. Based on the yields in these targets, the total number of Mn54 atoms produced per incident proton in a semi-infinite body of copper is 2.9×10−2 at 0.45 Gev, 7.5×10−2 at 1.0 Gev, and 2.0×10−1 at 3.0 Gev; the corresponding values for Zn65 are 3.7×10−3, 7.0×10−3, and 1.9×10−2. The experimental results have been compared with those of a Monte Carlo calculation that simulates the propagation of internuclear cascades in dense materials. The yields of Mn54 and Zn65 were computed as a function of location in the target from the particle fluxes given by the Monte Carlo calculation and from experimental excitation functions. The agreement is excellent for the production rates integrated over the target. It is generally good for the radially integrated dependence on depth but less satisfactory for detailed fits of the spatial distributions, Effects of finite beam size vis-a-vis the pencil beam of the calculation are discussed, and their inclusion is shown to improve the detailed comparisons. The Monte Carlo calculation has demonstrated the importance of internuclear cascade effects in thick targets: e.g., at 3.0 Gev about 90% of the Mn54 and virtually all the Zn65 is made by other particles than the primary ones, An analysis is presented of the different mechanisms by which a specific product can be made when high-energy particles enter large bodies, and the relative contribution of each of these mechanisms to the production of Zn65 and Mn54 in copper is evaluated.