Investigation of cosmic-ray showers at 4000 m. above sea-level

Abstract

During the summer of 1936, we made some experiments on Mt. Kazbek in the Caucasus in order to study cosmic-ray showers. The main object of the work was to find if the Z 2 law for the relative frequency of the recorded showers produced in thin layers of different elements of atomic number which had been established at sea-level by Morgan and Nielsen (1936) (Hu Chien Shan 1937), was also true at a considerable height above sea-level. The usual coincidence counting method was used. Most of the work was done using five counters arranged as described by Follett and Crawshaw (1936) and one of the authors (Hu Chien Shan 1937). An ordinary amplifier was used with pentodes in the first stages. To operate the counting meter two triodes in cascade were used instead of a thyratron, since this arrangement has a much lower filament consumption. Economy in filament consumption was essential, as there was no electric supply on the mountain and the filament accumulators had to be taken 15 km. down the mountain to be charged. One of the triodes was so arranged that the pulses were lengthened enough to operate the counting meter. Glass counters filled with argon-air mixture at a total pressure of about 20 cm. Hg were used. They all had an internal diameter of 1·7 cm. and a length of 20 cm. Each counter was fitted inside a thin tube made of tinned iron sheet, and this tube was soldered on to a thin cylindrical box which contained the pentode. This arrangement not only gives good shielding against pick-up, but also makes possible the use of very short bare connecting wires between the coupling condenser and the wire electrode of the counter. These counterpentode units were designed so that they could easily be made airtight and thus could be used even in very wet weather.