Cosmic-Ray Shower Production and Absorption in Various Materials

Measurements have been made of shower production in thin pieces of carbon, aluminum, copper, tin and lead. The results as shown by a study of three and twofold showers for thicknesses of 0.58 and 0.29 cm lead mass equivalent thickness and for several different experimental arrangements, indicate that the increase in counting rate associated with each atom in the producing material varies as the 2.0±0.2 power of the atomic number of the element concerned. Our measurements indicate that the increase in counting rate for heavy elements such as lead increases faster than the first power of the thickness of producing material. The departure from linearity seems to be a function of atomic number, being greater for elements of large $Z$. Absorption measurements of showers from lead, in lead, tin, copper, aluminum and carbon show that the absorption per atom varies between the first and second powers of the atomic number. Rossi transition curves for lead, iron and aluminum are presented. In the case of iron and aluminum these measurements are extended to larger thicknesses than in previous investigations.