Low-Cost Electrometer for Use in Ionizing Radiation Metrology

Dosimeters perform an essential role in ionizing radiation applications. Its operation is based on the proportionality between the radiation dose rate and the current induced by ionizing radiation in a sensor element. Thus, it is possible to calculate the absorbed radiation dose by integrating the measured current over time. This work’s main objective was to develop an electronic circuit based on a transimpedance amplifier to work with currents of pico amperes generated by an ionization chamber exposed to radioactive sources. The developed prototype can operate with currents from ± 10 pA to ± 1000 pA and generate polarization voltages for the ionization chamber in the range between ± 100 V and ± 400 V. Laboratory tests were carried out using an ionization camera coupled to this picoammeter using a triaxial cable. The camera was polarized at −150 V, and two Sr-90 radioactive sources were used during the tests. The currents generated by the radioactive sources were approximately 70 pA and 430 pA, respectively. The results were compared with those obtained from a commercial electrometer. The percentage error was less than 1.5%, indicating that the low-cost methodology proposed in this work is suitable for ionizing radiation dosimetry.