Cosmic-Ray Studies of Penetrating Showers and Bremsstrahlung at 11 200 Feet by Using Plastic Scintillation Counters

An apparatus was designed to study penetrating showers produced by high-energy cosmic rays. For this purpose, four anthracene-in-polystyrene plastic scintillators of 1 and 2 cm thickness were used with lead plates of thicknesses 2.00 cm, 2.25 cm, and 2.25 cm, respectively, interposed between them. In addition to these scintillation counters, four trays of G-M counters and an arrangement of anticoincidence counters were used. Data on penetrating showers produced in a graphite block and a polystyrene scintillator were obtained. It was found that in the energy range from 2 to 20 Bev, the resulting integral energy spectra of the ${\pi }^0$ mesons can be represented by a power law with an exponent equal to -1.7±0.2 in polystyrene, with no filter for the primaries. Similar results were obtained in graphite and in polystyrene with primaries filtered through 10 cm of lead. The multiplicity of the charged mesons in the penetrating showers produced in graphite can be described by a power law with an exponent -4.2±0.5, in general agreement with cloud chamber results. It was found that the energy distribution of bremsstrahlung $\gamma$ rays and the flux of the $\mu$ mesons producing this bremsstrahlung in a lead block of 10 cm thickness is in agreement with theory.