Rocket Determination of the Ionization Spectrum of Charged Cosmic Rays atλ=41°N

Abstract

In a V-2 rocket measurement at $\lambda =41\mathrm{}$°N an analysis has been made of the various components of the charged particle radiation on the basis of ionization and absorption in lead. The ionization was determined by two proportional counters, the particle paths through which were defined by Geiger counters. With increasing zenith angle toward the north, the intensity is found to be substantially constant until the earth ceases to cover the under side of the telescope. The intensity of all particles with range ≥7 g/${\mathrm{cm}}^2$ is 0.079±0.005 ${\left({\mathrm{cm}}^2\mathrm{s}\mathrm{e}\mathrm{c}\mathrm{s}\mathrm{t}\mathrm{e}\mathrm{r}\mathrm{a}\mathrm{d}\mathrm{i}\mathrm{a}\mathrm{n}\right)}^{-1\mathrm{}}$. Of this an intensity 0.012±0.002 is absorbed in the next 14 g/${\mathrm{cm}}^2$. The ionization measurement is consistent with $\frac{3}{4}$ of these soft particles being electrons of < ∼60 Mev, the remainder being slow protons and alpha-particles. For the particles with greater range an ionization histogram is plotted, the smaller of the two ionization measurements for a single event being used to improve the resolution. The particles divide into protons, alpha-particles, and one carbon nucleus, with $\frac{N_p}{N_{\alpha }}=5.3\mathrm{}\pm 1.0$. Their absorption is exponential with mean free path 440±70 g/${\mathrm{cm}}^2$ Pb. Extrapolating to zero thickness, the total primary intensity is 0.070±0.005 ${\left({\mathrm{cm}}^2\mathrm{s}\mathrm{e}\mathrm{c}\mathrm{s}\mathrm{t}\mathrm{e}\mathrm{r}\mathrm{a}\mathrm{d}\mathrm{i}\mathrm{a}\mathrm{n}\right)}^{-1\mathrm{}}$ with 0.058±0.005 as protons, 0.011±0.002 as alpha-particles, and 0.001±0.001 as $Z>\mathrm{}2\mathrm{}$.