The production of showers by cosmic radiation

The production of secondary particles by the passage of cosmic radiation through matter is a well-known feature of the cosmic ray phenomenon. Cloud chamber photographs of Blackett and Occhialini, Anderson, and Kuntze how that the secondaries often occur in groups, which have been named "showers.” The production of those showers was investigated by observing the simultaneous discharges of three Geiger-Müller counters so arranged that hey only recorded showers of at least three particles. The main experiments were carried out at the Forschunga-station Jungfraujoch, in Switzerland, at height of 8800 metres. Other experiments wero made at Eigergletscher (2300 m.) and Zürich (500 m.) to investigate the variation of frequency of the showers with altitude. Experimented Method. The experimental arrangement was similar to that used by Rossi and by Fünfer. Three Geiger-Müller counters were used, arranged as shown in fig. 1. The lead under investigation was placed above in such a position that no particle coming from the lead could go through more than one counter. The triple coincidences due to the presence of the lead must thus be due to showers of at least three particles. The coincidences were recorded by a method described by Rossi. The impulse from a fourth valve was fed to the grid of a thyratron by resistance capacity coupling, fig. 2. This impulse was a negative kick, but the accompanying positive back-kick was sufficient to trip the thyratron. This arrangement rendered the circuit very stable and free from external pickup.