Direct Determination of Primary Cosmic-Ray Alpha-Particle Energy Spectrum by New Method

The flux of cosmic-ray alpha particles has been measured at λ=41^∘N and 55^∘N and the energy spectrum in the region 883-285 Mev/nucleon has been determined by the use of a combination of a scintillation and {C} {C}{}erenkov counter. This spectrum is not dependent on geomagnetic theory. It has been found that the integral alpha spectrum can be fitted with the function ${J}_{0{α}}(E)={431}{{(1+E)}^{1.4±{}0.2}}particles/{m}²{-}sec{-}sterad,$ and ${J}_{0{α}}({E}₁)=87±{}9 particles/{m}²{-}sec{-}sterad, {λ}=41^∘{}N,$ ${J}_{0{α}}(0.285 Bev)=292±{}25 particles/{m}²{-}sec{-}sterad, {λ}=55^∘{}N.$ ${J}_{0{α}}(E)$ is the flux of ${α}$ particles at the top of the atmosphere with kinetic energy ${}E$ (in Bev/nucleon). ${E}₁$ is the cutoff energy/nucleon for ${α}particles at 41^∘N. An absorption mean free path{{λ}}_{{α}}=45±{}7$ g/${cm}²$ has been measured for alpha particles. The properties of this new detector are discussed and a study is made of the energy response of the {C} {C}{}erenkov counter to fast multiply-charged particles.