Improving and optimizing the structure of a cylindrical ionization chamber for radiation protection dosimetry: Guard electrode and chamber wall

摘要

Due to relative ease, high accuracy, high sensitivity, appropriate response, and other properties of ionization chambers, they are usually employed as reference instruments in dosimetry and quality assurance programs. Therefore, any improvement and optimization in the structure of these dosimeters can lead to accurate measurements of the absorbed dose. In the present study, the structure of a specific cylindrical ionization chamber (PTW, model 23361, Freiburg, Germany) was improved and optimized. After the design and construction of the new cylindrical ionization chamber, the performance of this dosimeter was investigated by saturation, ion collection efficiency, polarization, leakage current, stability, and linearity of response tests. The findings of performance tests showed that the response of the introduced dosimeter agrees with the recommended standards. The new design and construction of the guard electrode, both in length and arrangement of the dosimeter structure, can improve the electric field and decrease the leakage current. Moreover, the use of pure graphite in the chamber's wall can result to improve in the electric field of the chamber's sensitive volume, thereby improving the performance of the dosimeter.