ION LOSS DUE TO INITIAL RECOMBINATION IN A PARALLEL-PLATE CAVITY IONIZATION-CHAMBER

Collection efficiencies for ion loss due to initial recombination and back-diffusion were measured for several humidities using a parallel-p late cavity ionization chamber irradiated with Co-60 gamma-rays. It wa s shown, from measurements in a range of inverse electric field streng ths from 0.05 to 14 mm V-1, that initial recombination took place both in clusters and columns of ions produced along the path of the second ary electrons ejected by the gamma-rays. The ion loss due to recombina tion in clusters was found to increase with humidity, but that in colu mns did not. Effects of ion clustering reactions on recombination may be reduced after longer periods of ion drift, when recombination in co lumns takes place. Ion loss due to back-diffusion was also found to ha ve no dependence on humidity.