Charge and energy spectra of cosmic-ray nuclei with Z = 10–28

Abstract

An improved method of charge determination of heavy primary cosmic rays of nuclear charge Z = 10–28 has been obtained by measuring the Fowler–Perkins parameter in less-sensitive G-2 and G-0 emulsions for the determination of the primary ionization. It is found that reliable measurements of the primary ionization can be made for ionizations as high as ~1 000 times minimum. The average errors in the charge determinations by this method were found to be about 0.5, 0.7, and 1.0 unit of charge for H1 (Z = 10–15), H2 (Z = 16–19), and H3 (Z = 20–30) groups of nuclei, respectively. This method has been applied to the study of the H1, H2, and H3 groups of nuclei in an emulsion stack exposed over Fort Churchill, Canada, on June 18, 1963 at 4.3 g cm−2 of residual atmosphere for 11.1 h. The results are based on an analysis of 340 nuclei with [Formula: see text]. The charge composition and relative abundances of the H1, H2, and H3 nuclei were obtained. The differential energy spectra of the H1, H2, H3, and [Formula: see text] groups of nuclei were determined in the energy interval 250–1 000 MeV/nucleon and integral fluxes for energy > 1 000 MeV/nucleon.