Soft Radiation at Balloon Altitudes

Abstract

Results are given on cloud-chamber observations of electron showers and "spray" events at high altitude (18 millibars). The fluxes derived for initiating radiation are consistent with a common origin for showers and "sprays," and thus support the conclusion by Rau and Wightman that "sprays" are showers produced in a single lead plate. However, less than one-fourth as many such events occur as would be expected from observations on mu-mesons if mesons are produced with a spectrum that does not vary with altitude. If all soft radiation at 18 millibars were of primary origin, it would constitute less than 0.6 percent of the total cosmic-ray flux.