Tritium Production by 2.2-Bev Protons on Iron and Its Relation to Cosmic Radiation

The cross section for tritium production by 2.2-Bev protons on iron is measured to be 62±7 mb. This tritium cross section indicates that (1.4±0.4)×${10}^{-3\mathrm{}}$ tritons/g sec would be produced in small iron meteorites (a few inches in radius) in space by cosmic rays of the intensity of those striking the earth's polar regions. In 4×${10}^9$ years, (6±2)×${10}^{-6\mathrm{}}$ cc of ${\mathrm{He}}^3$ per gram of iron results from this cosmic-ray tritium. Mount Ayliff meteorite contains 11.5×${10}^{-6\mathrm{}}$ cc of ${\mathrm{He}}^3$ per gram, indicating its bombardment by a cosmic-ray flux at least as intense as is presently striking the earth. The variation of tritium with target depth is also measured and indicates a decrease less rapid than an attenuation due to geometric cross section.