X-Ray fluorescence imaging system based on Thick-GEM detectors

Abstract

AgradecimentosEste trabalho recebeu apoio financeiro da Fundação de Amparo à Pesquisa do Estado de São Paulo, com a bolsa FAPESP 2017/00426-9.My sincere thanks to the whole GDD lab at CERN, in special Leszek Ropelewski, Eraldo Oliveri, Patrik Thuiner and Florian Brunbauer.Gostaria de agradecer primeiramente ao professor Alexandre Suaide, por me introduzir ao grupo e pela ajuda nos mais diversos assuntos. À professora Marcia Rizzuto e à minha amiga Hellen Santos, pelo interesse nesse trabalho e troca de informações.Aos professores Marco Bregant, Marcelo Munhoz, Nelson Carlin, Tiago Fiorini, Mauro Cosentino e Zwinglio Guimarães pelas ideias e sugestões, tornando esse trabalho muito mais completo.Ao meu orientador e amigo, Hugo Natal da Luz, pelos ensinamentos, conselhos e paciência. Aos amigos que fiz durante a graduação e o mestrado, pela diversão, aprendizado e companhia durante todos esse anos. Um agradecimento especial aos amigos do grupo, Henrique, Milton, Camila, Chiara, Thais e Lucas. À minha familia, meus pais, Marco Aurélio e Maria Cabrine, e meu irmão Ramon, por toda confiança e suporte. Vocês são os melhores exemplos para mim. À Mayumi, pelo carinho e por estar ao meu lado nos melhores e piores momentos."All we have to decide is what to do with the time that is given us." -J.R.R. Tolkien, The Lord of The Rings Abstract GEMs (Gas Electron Multiplier) and Thick-GEMs (Thick-Gas Electron Multiplier) are MPGDs (Micropattern Gas Detector) that make part of the new generation of gaseous detectors, allowing high counting rates, low cost when compared to solid state detectors, high radiation hardness and gain when using multiple structures. Besides that, the handling and maintenance of these detectors is relatively simple, being versatile to detect different types of radiation. Therefore, these detectors are an effective alternative to build imaging systems with large sensitive area. This work consists in the study and characterization of a set of gaseous detectors, more specifically the Thick-GEMs produced in the High Energy Physics and Instrumentation Center at IFUSP, which were tested showing promising results in terms of gain, energy resolution and operational stability. However, due to the low signal-to-noise ratio of the Thick-GEMs, the X-ray fluorescence imaging system was mounted using GEMs. During this work the necessary software tools for image processing and reconstruction were developed as a parallel study in computational simulations to better understand the operation of gaseous detectors.X-ray fluorescence techniques are essential in areas such as medicine and the study of historical and cultural heritage since they are non-invasive and non-destructive. Techniques to check the authenticity of masterpieces are required and museums are gradually becoming more interested in the Physics and instrumentation needed to characterize their patrimony.

Comparing different methods of position reconstruction considering 1D readout of GEM detectors

“…The algorithms were made using Python [5] programming language, considering a 1D readout of strips. From previous work [3] is known that the cloud widths of the order of 0.2 mm are expected in a typical detector used in our laboratory: gas mixture of Ar/CO2 (70/30) and an electrical field of 400 V/cm in a drift region of around 1 cm. Therefore for this study we have modeled a 1 cm readout, from -0.5 cm to 0.5 cm, where the coordinate 0 is in the middle of the strips pattern.…”

Double-GEM based thermal neutron detector prototype

“…4, since it is position-independent, coming directly from the multiplication. Considering the expected extraction efficiency 𝜖 ext for the last GEM [29], the charge signal collected at its bottom is given by 1 − 𝜖 ext , which is ∼ 64 % of the multiplied charge for our configuration. In order to reconstruct the event's position, we use Eq.…”

Double-GEM based thermal neutron detector prototype

“…The charge signal is used as the trigger for the data acquisition, as shown in figure 4, since it is position-independent, coming directly from the multiplication. Considering the expected extraction efficiency 𝜖 ext for the last GEM [29], the charge signal collected at its bottom is given by 1 − 𝜖 ext , which is approximately 64% of the multiplied charge for our configuration.…”