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

The flux of cosmic-ray alpha particles has been measured at $\lambda =41\mathrm{}°\mathrm{N} \mathrm{and} 55°\mathrm{N}$ and the energy spectrum in the region 883-285 Mev/nucleon has been determined by the use of a combination of a scintillation and Čerenkov counter. This spectrum is not dependent on geomagnetic theory. It has been found that the integral alpha spectrum can be fitted with the function $J_{0\alpha }\mathrm{}\left(E\right)=\frac{431}{{\mathrm{}(1+E)\mathrm{}}^{1.4\pm 0.2}}\mathrm{particles}/{\mathrm{m}}^2-\mathrm{s}\mathrm{e}\mathrm{c}-\mathrm{s}\mathrm{t}\mathrm{e}\mathrm{r}\mathrm{a}\mathrm{d},$ and $J_{0\alpha }\left(E_1\right)=87\mathrm{}\pm 9 \mathrm{particles}/{\mathrm{m}}^2-\mathrm{s}\mathrm{e}\mathrm{c}-\mathrm{s}\mathrm{t}\mathrm{e}\mathrm{r}\mathrm{a}\mathrm{d}, \lambda =41\mathrm{}°\mathrm{N},$ $J_{0\alpha }\left(0.285\mathrm{} \mathrm{Bev}\right)=292\mathrm{}\pm 25 \mathrm{particles}/{\mathrm{m}}^2-\mathrm{s}\mathrm{e}\mathrm{c}-\mathrm{s}\mathrm{t}\mathrm{e}\mathrm{r}\mathrm{a}\mathrm{d}, \lambda =55\mathrm{}°\mathrm{N}.$ $J_{0\alpha }\mathrm{}\left(E\right)\mathrm{}$ is the flux of $\alpha$ particles at the top of the atmosphere with kinetic energy $\geqq E$ (in Bev/nucleon). $E_1$ is the cutoff energy/nucleon for $\alpha$ particles at 41°N. An absorption mean free path ${\lambda }_{\alpha }=45\mathrm{}\pm 7$ g/${\mathrm{cm}}^2$ 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 Čerenkov counter to fast multiply-charged particles.