Energy Spectra of Cosmic-Ray Photons and Electrons from Plastic Scintillation Counter Measurements

A new method of measuring high energy photons and electrons is reported. Using an experimental arrangement consisting of G-M counters and scintillation counters with large plastic scintillators, the number vs size distribution of cosmic-ray showers produced by photons and electrons in a lead block of one inch thickness was measured. From the results of shower theory the energy spectra of cosmic-ray photons and electrons at Chicago (600 ft above sea level and 51° N geomag. lat) were deduced. The results of the present investigation show that in the energy range of 0.3-2.0 Bev, the differential energy distributions can be represented by a power law of the form $E^{-s}$, with $s=2.71\mathrm{}\pm 0.13$ and $s=2.81\mathrm{}\pm 0.13$ for the photon and electron components, respectively. The exponent $s$ decreases considerably at energies below 0.2 Bev. An essential part of this investigation is to provide a suitable means of measuring the energies of energetic $\gamma$-rays or electrons, or the energy distribution of energetic $\gamma$-rays or electrons. The results show that scintillation counter arrangements consisting of large plastic scintillators are suitable instruments for these purposes. This method could also be applied to energy measurements of photons and electrons from high energy accelerators.