Cross sections for production of stable and long-lived nuclides by high energy spallation of iron; cosmic ray implications

The cross sections for production of the stable and long-lived isotopes of Be, Sc, V, Cr, and Mn by proton spallation of Fe have been measured at 600 MeV and 21 GeV. The experimental method involves the contamination free separation of the spallation products from ultrapure iron targets and the mass spectrometric determination of their isotopic ratios. To derive absolute cross sections, radioactive isotopes are used as references. For this purpose, the cross sections of a few radioactive isotopes have been measured at 21 GeV by $\gamma$-ray spectrometry. The results are compared with the values obtained by means of semiempirical formulas. The overall agreement is good but the cross sections for formation of manganese isotopes are found to be significantly higher than predicted. The implications of the results for path-length distribution and source abundances of cosmic ray nuclei with $21\le Z\le 26$ are discussed. Calculated cosmic ray isotopic distributions are presented for some elements, which illustrate the potential resources of electron capture isotopes.