Estudo de circuitos com capacitores comerciais para aplicação de medidas dosimétricas de radiações ionizantes

Abstract

With the health problems generated by X-ray exposures after its discovery, studies have emerged in order to create safe methodologies for the application of ionizing radiation. Therefore, to ensure quality control, detector systems are used for each energy used. We can mention as a dosimetric detector system an ionization chamber and an electrometer, which are widely used due to linearity and response stability. Thus, in this work, we obtained dosimetric measurements using commercial capacitors as a replacement for the ionization chamber, two of them, one for testing and the other for comparison and as an electrometer, a TL074CN integrated circuit, containing four high impedance Operational Amplifiers (AO) (10¹² Ω). The use of the capacitor is justified due to the low cost and simple and didactic engineering. We place ionizing radiation on the test capacitor and monitor the charge / discharge voltage by comparing it with the reference capacitor in the circuit. The data was read and recorded using a bench oscilloscope. We initially varied the radiation voltage by 5–25 kV, keeping the voltage fixed at 1 mA, in sequence we kept the voltage fixed at 35 kV and varied the current from 0.05–1.00 mA. Through the initial slope we obtained the response of a current due to the photoelectric effect, predominant for this energy. Corrections of the equations were necessary to eliminate the capacitive effect generated and to obtain reliable linear data. We need to prove its efficiency and accuracy for a future application in X-ray equipment calibration in order to be able to replace dosimetric systems. However, much study is still needed to admit capacitors as sensors.