Ionization of air by gamma-rays as a function of pressure and collecting field II

The γ-ray ionization current measurements in air at high pressures made by Erikson and by Clay and Van Tijn are shown to be largely modified by volume recombination at collecting fields below about 400 volts per cm. The Jaffé theory of columnar ionization does not explain the observed variation of ion current when it is applied over a wide range of collecting fields to data free from volume recombination.