Projeto e desenvolvimento de sistema de posicionamento automatizado para simulação de fonte de radiação infinita e calibração de detectores de radiação

Abstract

Computational simulation with the Monte Carlo method has been used by researchers in several studies related to the interaction of radiation with matter. In order to validate the results of these simulations, it is necessary to obtain real experimental data so that they can be compared with the simulation results. There is, however, a difficulty in obtaining experimental data in laboratories for cases where the radiation source has larger dimensions than laboratory sources, which are usually quite small. The objective of this work was to design, build, program and test a prototype of an equipment that makes very precise automated displacements to change the linear distance and angle between a set of source and detector, in order to be able to experimentally simulate a large source by using a very small laboratory source. With different dose rate measurements at different positions, it is possible to interpret the sum of these measurements as the value that would be read by the detector if the radiation source had larger dimensions. The prototype was designed using a CAD, having several components printed using a 3D printer. For the operation of the prototype, stepper motors controlled by Arduino boards were used. The Arduino microcontroller was programmed using a programming language based on C/C++. Due to the accuracy of the displacement, the prototype can also be used for calibration of radiation detectors. To do this, it is only necessary to use the linear displacement function to precisely position the set of source and detector. With a known laboratory source, it is possible to adjust the detector calibration factor so that the reading is as expected for that source at the given distance. The prototype has been tested to ensure high positioning accuracy. For the linear displacement, precision of 1 mm was obtained in the displacements, while in the angular displacement, precision of 0.4° was obtained. The prototype was used to obtain experimental data with a set of source and detector, which can already be used in other studies to validate results of computational simulations using the Monte Carlo method.