The Absorption of Cosmic-Ray Electrons

Abstract

The interpretation that the coincident discharge of three or more G-M counters in line represents the passage of a single ionizing particle through the counters and any intervening material has been checked by two methods: (1) A vertical cloud chamber between the central and lower counters of a triple-counter telescope controlling the chamber has shown in 90 percent of the coincidences a single electron directed through the counters even when lead up to 45 cm in thickness is placed between the central and upper counters. Soft or hard rays associated with the single particle are rare. (2) Four counters so spaced that 90 cm of material could be introduced between them controlled additional counters which were placed adjacent to the telescope elements and connected as in a hodoscope circuit for the detection of rays associated with those producing the quadruple counts. In only 10 percent of the coincidences were any of the side counters discharged. Absorption data obtained with the latter arrangement for lead, iron and marble (CaC${\mathrm{O}}_{3}$) indicate that the absorption as a function of the thickness of absorber on a scale of extranuclear electrons per ${\mathrm{cm}}^{2}$ is approximately the same for all three materials. The lead values have been compared with Anderson's electron energy distribution (for the counter controlled data) to determine what specific energy loss values for electrons in lead must be assumed to satisfy both sets of data. The results are: