Nuclei in Cosmic Rays

Abstract

Cosmic rays were discovered almost 80 years ago by Victor Hess [Hes12] who was at that time working at the University of Vienna. He searched for the cause of the residual ionization of air which persisted even behind the most massive shielding. For this purpose he performed several balloon flights with an instrument which we should now call an ionization chamber. Most of these flights were launched from the site of the “K. u. K. Österreichischen Aero Club” in the Prater at the outskirts of Vienna although the most successful flight started from Aussig in northern Bohemia, went north and ended some 50 km east of Berlin [Hes12]. The results of the measurements during this flight showed unambiguously that the ionization of air passed through a flat minimum between 1000 and 2000 m above ground and then increased steeply to values much above ground level. This clearly indicated an extraterrestrial source of radiation.