An electronic dosimeter for diagnostic X-ray beams based on a differential amplifier circuit with MOSFETs

¹ CRCN-NE/CNEN, Brazil
² UFPE, Brazil
³ SCIENTS, Brazil

^* lasantos.scients@gmail.com.br

Published online: 21 November 2023

Abstract

It is known that the device MOSFET works as a dosimeter in radiation beams for cancer radiotherapy. Basically, the radiation beam generates defects in a way that produces in the MOSFET the variation in its threshold voltage, V_T, which is proportional to the accumulated radiation dose. Recently, MOSFETs were also tested under X-ray beams commonly used in the energy range applied to medical diagnoses, which is lower energy than radiotherapy. Indeed, it was already shown that the MOSFET drain current varies with the radiation dose for energies in the range applied to diagnostic radiology. In this paper, an innovative method based on a differential amplifier circuit with two electronically matched MOSFETs is presented. Therefore, before irradiation the differential output voltage signal, V_dif = 0. Actually, it is a differential amplifier circuit with one of the MOSFETs shielded from the ionizing radiation beam. Therefore, if such a circuit is irradiated the difference between ID1 and ID2, from MOSFET1 and MOSFET2 respectively, will result Vdif ≠ 0. To evaluate the response of this electronic dosimeter it was tested under a diagnostic radiology beam typically used in clinics to take radiography of patients. The results showed that the proposed dosimeter works and varies linearly with the radiation dose. The technology developed in this paper will allow research to be carried out for optimizing such electronic dosimeter to make it a wearable device and can be able to use it by workers exposed to ionizing radiation in nuclear power plants or even in outer space.