The effects of humidity on volume recombination in ionization chambers.

Saturation curves were measured with a parallel-plate ionization chamber for air with humidities of 0%-81%. From the curves, values of m--which is equal to (alpha/eK+ K-)1/2 where alpha is the recombination coefficient, e the charge of an ion, and K+ and K- are mobilities of positive and negative ions, respectively-were obtained. It was confirmed that humidity was the decisive cause of the increase in the value of m with the lifetime of ions in the ionization chamber. It was found that the value of m increases sharply in a range of small values of the product of the ion lifetime and the partial pressure of water vapour and increases more slowly at high values of this parameter.