Some Cross Sections for the Production of Radio-Nuclides in the Bombardment of C, N, O, and Fe by Medium Energy Protons

Abstract

A number of nuclide formation cross sections have been measured, using the Berkeley 184-in. cyclotron, to assist in the interpretation of the data on cosmic-ray-produced nuclides in the atmosphere and in iron meteorites.Cross sections of ${\mathrm{H}}^{3}$ and ${\mathrm{Be}}^{7}$ have been measured in bombardments of organic targets containing nitrogen and oxygen by protons of energy 225-730 Mev. Semicarbazide (C${\mathrm{H}}_{5}$${\mathrm{N}}_{3}$O) targets were used to obtain cross sections in air nuclei. The targets were prepared by mixing with a few percent of aluminum dust to permit reliable monitoring of the beam. Polyethylene, aluminum lactate, and Plexigals targets provided elementary cross sections in carbon and oxygen.The cross sections for the production of the long lived isotopes ${\mathrm{Cl}}^{36}$ (3\ifmmode\times\else\texttimes\fi{}${10}^{5}$ yr) and ${\mathrm{Al}}^{26}$ (8\ifmmode\times\else\texttimes\fi{}${10}^{5}$ yr) at 730 Mev, and of a number of short lived radionuclides at 500 and 730 Mev, in iron bombardment by protons have been measured. These data and those of earlier workers suggest some modifications in empirical relations used for predicting spallation cross sections in the case of nuclides close to stability