Estudo, caracterização e simulação em COMSOL de fibras PCF visando a construção de um detector de radiação

Abstract

Radiological protection is vital, becoming a current and widely studied subject. In addition, ionizing radiation detectors are essential and legally mandatory in any place that works with them, protecting the environment and all living beings involved. Thus, several devices are fulfilling this role, however, in general, they have a high cost of production and sale, in addition to, generally, the most affordable ones do not have instant measurement. With this in mind, there are ways to overcome these obstacles in the production of a radiation detector, among them, the use of optical fibers and the phenomenon of radioluminescence. Optical fiber is a technological innovation that has revolutionized the way all human beings communicate, mainly because it is considered low-cost, small, light, versatile, and not damaged by radiation. For these reasons, there are many uses for optical fiber, with use in sensor manufacturing being one of the main applications for this tool. Examples of these applications include motion sensors, substance sensors, and radiation sensors. Radioluminescence, on the other hand, occurs when ionizing radiation falls on a radioluminescent material, which will excite the electrons of the material and, when it becomes deexcited, emit photons. Thus, this phenomenon will help in the instantaneous verification of the irradiated dose. In this way, with the help of fibers and a radioluminescent material, it would be possible to build a low-cost radiation sensor, which, when ionizing radiation falls, instantaneously produces light that will be guided along the length of the fiber to a photosensitive device. To do so, some points must be examined and tested, such as the way in which fiber material will be used, or which fiber geometry will maximize the operation of the system, as well as which radioluminescent substances are good candidates for this purpose. For this purpose, this dissertation aims to study and characterize four different PCF-type fibers, Photonic-crystal fibers, with different geometries, as possible candidates for radiosensitive material storage devices and light guidance devices. With this objective, micro-tomography was performed of each of the fibers, which were reconstructed and segmented in the Avizo 3D program to measure their geometric properties. Complementing this study, simulations, in the COMSOL multiphysics program, of the PCFs in question were produced to compare which geometry would generate a fundamental and central mode with the highest electric field strength and lowest confinement loss.