Investigation into the relation of shower frequency to general cosmic-ray intensity.

Abstract

Follett and Crawshaw (1936) have compared the transition curve of showers from lead at sea-level and under 30 m. of clay (60 m. water equivalent) and find that the the number of showers decreases about in the same ratio as the vertical intensity. Other measurements of the showers below sea-level have been made by Clay and Clay (1935), Auger and Rosenberg (1935), Ehmert (1937 a, b ), Wilson (1938) and by Pickering (1935, 1937). The purpose of the work described in this paper was to investigate how the form of the shower transition curves at the two levels (i. e. sea-level and under 30 m. of clay) depends on the presence of large masses of light material (e. g. stone) over the lead absorber producing the showers. Drigo (1935) and Auger, Leprince-Ringuet and Ehrenfest (1936) had previously shown that at sea-level the presence of such light materials greatly reduces the number of showers and also alters the shape of the transition curve. Thus to get comparable results at the two levels it is necessary to use similar distributions of dense matter over the counting set. In the work of Follett and Crawshaw this was not the case.