Cosmic-ray ionization and electroscope-constants as a function of pressure

Abstract

1. The residual ionization in an electroscope at infinite depth in water, that is, its zero reading, is found to be an inverse function of the pressure. Thus, in a particular electroscope the zero at 1 atmosphere was 5.13 ions cc/sec., while at 30.1 it had fallen to 1.2 ions cc/sec. 2. Also, when in this electroscope the pressure was changed from 1 atmosphere to 30.1 atmospheres the observed ionization current rose but 13.80 fold, which multiplying factor was found the same for gamma rays and for cosmic rays. 3. Both of these pressure effects are shown to be due to lack-of-saturation in high pressure electroscopes, as first explained in Nature of October 3, 1931, by Bowen and the author. 4. From the multiplying factor found in (2) in the measured ionization at Pasadena in this 30 atmosphere high-pressure electroscope, the number of cosmic-ray ions at 1 atmosphere (24°C 74 cm pressure) in this electroscope at Pasadena is found to be fairly accurately 2.63 ions cc/sec. 5. The sea level value of the ionization in this electroscope is 2.48 ions cc/sec.