THE EFFECT OF THE APPLIED VOLTAGE ON IONIZATION IN A PARALLEL PLATE IONIZATION-CHAMBER

The following phenomena were observed on output currents from a parallel plate ionization chamber which was irradiated with X-rays or Co-60 gamma-rays. For irradiation from the front side (polarizing electrode) with gamma-rays, the output current of the chamber increases and decreases linearly with positive and negative applied voltage (beyond the recombination region), respectively. The increase or decrease of the current is reversed when the chamber is irradiated from the rear side (collector). The rate of increase/decrease is relatively lower in the case of X-ray irradiation. This increase/decrease is attributed to the change in stopping power of air due to acceleration/deceleration of secondary electrons in the applied electric field.