Background: If we try to perform the inspection for an electrometer, two types of electronic signals energized to the electrometer can be used. One is the signal that occurs in the ionization chamber irradiated by radiation. The other is the signal that is derived from a current source. The former signal is changed by radiation output, so we need to use two or more sets of the chambers and the electrometers in the inspection. In addition, the high-performance current source is relatively expensive. Therefore, it is difficult for users to inspect the electrometer simply. To deal with these, we have developed a new current source that allows users to perform highly accurate electrometer inspections at their own facilities.
Aim: The purpose of this study was to verify that users can perform electrometer inspections with high accuracy in their own facilities by using a new current source.
Materials and methods: A newly current source equips a dry cell battery as a charge generator. Current, polarity, and energized time can be changed by the source setting. We conducted an inspection by energizing the electrometer using the developed current source.
Results: The coefficient of variation of the charge amount in the measurement using the new current source was within 0.05%. The electrometer calibration coefficients measured by sensitivity comparison using this current source could be obtained based on electrometers calibrated at a certified facility of the Japan Calibration Service System.
Conclusion: We have shown that the new current source can be used as a relative current value by using a calibrated electrometer as a reference, indicating that the user can check the electrometer.
Keywords: calibration separately; current source; dosimeter; electrometer; radiotherapy.