Čerenkov Scintillation Counter Measurements Relating to the Isotopic Composition of Helium Nuclei in the Primary Cosmic Radiation

Abstract

A balloon-borne scintillation-scintillation \ifmmode \check{C}\else \v{C}\fi{}erenkov telescope has been used to measure the spectrum and geomagnetic cutoff-transmission effects on the low-energy proton and helium components in the primary cosmic radiation. Differences are found in the cutoff effects (assumed to be rigidity-dependent) of these two components in flights at closely adjacent latitudes. It is shown that these differences can be related to the presence of ${\mathrm{He}}^{3}$ in the primary radiation. The ratio (${\mathrm{He}}^{3}$/${\mathrm{He}}^{3}$+${\mathrm{He}}^{4}$) is deduced to be 0.30\ifmmode\pm\else\textpm\fi{}0.07, essentially independent of energy in the range 120-300 MeV/nucleon. This result is compared with other measurements and some implications regarding the production of the ${\mathrm{He}}^{3}$ nuclei are discussed.