The connexion between cosmic ray showers and bursts

Cosmic ray showers have so far been mostly investigated by counting the number of triple coincidences of suitably arranged Geiger-Müller counters. The information obtained in this way is restricted to the number of these events and does not give the number of particles in the shower. To obtain more complete information on showers an ionization chamber was put above the counters in the experiments described below, and the ionization in the chamber was recorded whenever all three counters discharged simultaneously. 2- Experimental Arrangement The arrangement of ionization chamber and counters is seen from fig. 1. The ionization chamber proper consisted of a wire cage, rectangular in shape, of 2·1 liters volume, reinforced by a substantial steel frame. The inner electrode, connected to the first valve of a linear amplifier of the Wynn Williams type, was a plain wire net, also reinforced by a steel frame. The whole structure was put in a cylindrical brass vessel with a wall 3 mm thick, filled with commercial nitrogen at 5 atm. pressure. A potential of about- 1500 volts was maintained between the electrodes of the chamber, giving a field of 500 volts/cm. The collecting time of ions was calculated to be slightly under 1/50 sec. The mean path of a cosmic ray particle in the chamber is about 10 cm, in which distance on the average about 5000 I (ion pairs) are produced. The rate of single cosmic ray particles crossing the chamber is about 5 per second. These values are obtained under the assumption that in air at N. T. P., 2·48 I are produced by cosmic radiation per cm3 and that a single particle produces produces 100 I per cm path in air at N. T. P. Fig. 1 shows also the size and arrangement of the counters and of the lead plate which is placed above the chamber to increase the number of showers.