Emulsion Studies of Cosmic-Ray Stars Produced in Metal Foils

Abstract

A method is described in which cosmic-ray induced disintegration of nuclei of several elements are studied with metal foils sandwiched between nuclear emulsions placed face-to-face and exposed at balloon altitudes. The range distributions of low-energy particles are obtained from tracks ending in the emulsion. Calculation of the probabilities of detecting star particles permits conversion of the observed star size distributions to the real size distributions, whose variation with atomic number is presented. The variation, with atomic weight, of the cross-sections for the production of stars of various sizes is analyzed. The number of tracks per star corresponding to protons in the energy range 25-100 Mev is obtained and found to vary approximately as the nuclear radius.