A thin-wall ionization chamber used as a laboratory reference for exposure measurement at radiation protection level

A spherical thin-wall ionization chamber has been developed as a laboratory reference for exposure measurement at radiation protection level. The volume of the chamber is about 100 cm3 and the background current is about 1 x 10-15 A in normal condition. The energy dependence normalized to 60Co is within 5% for energies ranging from 33 keV to 1.25 MeV. As exposure rate greater than 10mR/h, the uncertainty of the chamber's calibration factor was estimated to be ±0.9% for above energy range. And over the energy range, the intercomparison results of the chamber with IAEA dosimetry ladoratory were found to be consistent within 1.2% between them during the period of IAEA's Workshop and Seminar on SSDL's Calibration Procedure in Malaysia (1987)