Cosmic-Ray Ionization as a Function of Pressure, Temperature, and Dimensions of the Ionization Chamber

Abstract

Experiments have been performed to test the adequacy of the writer's explanation of the dependence upon pressure of the cosmic-ray ionization in gases at high pressures in terms of subsidiary radiations emitted solely from the walls of the ionization chamber. The ionization in a 436 cc sphere of 33.32 g mass located at the center of the 660 lb. bomb of 13.8 liters capacity used in previous experiments, was found not to differ greatly from the average ionization in the large chamber at corresponding pressures up to 175 atmospheres. At the higher pressures gamma-ray ionization and cosmic-ray ionization were found to vary with the pressure in the same manner. These facts are considered to be incompatible with the explanation mentioned above. The temperature effect was found to amount to 0.19 percent increase in ionization per centigrade degree increase in temperature at a mean pressure of 23.3 atmospheres, and 0.27 percent per degree at 162.1 atmospheres, in qualitative but not entirely in quantitative agreement with the theory and observations of Compton, Bennett and Stearns. The cosmic-ray ionization at 205 atmospheres in the shielded bomb was found to agree within about one percent with the upper limit previously observed in the same chamber with similar shielding at pressures between 130 and 170 atmospheres. Certain transient effects associated with changes in pressure and temperature were observed.