Design and Construction of a Cylindrical Ionization Chamber for Reference Dosimetry in Radiation Protection

According to the recommendations of the International Atomic Energy Agency (IAEA), the calibration of ionization chambers used for radiotherapy dosimetry is an alternative method that requires the use of a reference ionization chamber. This project aims to design and construct a cylindrical ionization chamber detector as a reference dosimeter for standard dosimetry laboratories. The quality control tests were carried out in the Secondary Standard Dosimetry Laboratory of the Atomic Energy Organization in Iran according to the IAEA standards and restrictions. Leakage current and low polarity effect, ion collection efficiency and high stability, linear response of the detector to the dose and air Kerma rate were the salient features of the present detector compared to similar models, which was generally due to the optimal design of the designed collecting and protective electrodes and a selection of suitable materials in construction. Charge collection efficiency was 99.92% at the operating polarization voltage of 400 V and 69.018 mGy/min dose rate. Also, the relationship between ionization current and Kerma rate at different distances was linear with a correlation coefficient of R2 = 0.999. This constructed detector may be utilized as a reference dosimeter for calibration process in a straightforward and cost-effective manner due to its good performance.