AN IMPROVED LEAKAGE CURRENT COMPENSATION TECHNIQUE FOR A 4-PI-GAMMA IONIZATION-CHAMBER SYSTEM

A current integration method using a small capacitor is most commonly employed for precise measurements of small currents from 4 pi gamma io nization chambers for the secondary standardization of radionuclides. An improved technique has been developed for eliminating the possible effect due to the electrical leakage and/or current loss across the fe edback capacitor used in the integration of the ionization current. Th is method is based upon charge integration from a fixed negative level of potential to nearly the same level of positive potential via the z ero point. The validity of this method is demonstrated for some typica l applications of 4 pi gamma ionization chamber systems. This techniqu e can contribute to the improvement of accuracy and to the extension o f the intensity range of radioactive source in 4 pi gamma ionization m easurement.