Dissertations / Theses on the topic 'PMPTS'

Conselho Nacional de Desenvolvimento Científico e Tecnológico
Since the first report from the Toyota research group, polymer/clay nanocomposites have attracted great interest and lots of attempts to prepare these nanocomposites. The addition of small contents of clay into polymer matrix exhibits potential increase in the physical and chemical properties such as flame retardance, barrier, flame and solvent resistances, thermal properties and advanced corrosion coatings. The study of polymer/clay nanocomposites are of fundamental importance due to a better understanding of the structural properties which optimizes its applications. The morphology of these nanocomposites depends on strongly of the synthesis conditions such as clay content and the synthetic method. Therefore, the use of the multivariable systems (factorial design of experiments) to evaluate the effect of experimental variables on the properties of the nanocomposites is of great relevance. In the present study, nanocomposites obtained from copolymerization of poly(methyl methacrylate), PMMA and poly(methacryloxy propryltrimethoxysilane), PMPTS forming PMMA-co-PMPTS and adding protonate montmorillonite (MMT H+) clay were prepared via in situ polymerization using benzoyl peroxide (BPO) as thermal initiator. Factorial design systems (four factors at two levels) were used to study the influence on effects of experimental variables (MMA, MPTS, MMT H+ and BPO) on the thermal properties of (PMMA-co-PMPTS)/MMT H+ nanocomposites using thermogravimetry. The structure and morphology were studied by X-ray diffraction, fourier transform infrared and transmission electronic microscopy. The study of thermal properties through the factorial design showed that the sample prepared by combining 150 mmol of MMA, 23 mmol MPTS, 0.186 mmol BPO and 0.150 g MMT H + (experiment 7, AM7) showed the highest depolymerization temperature (Td) (381 ° C). The value of the determination coefficient (R2) obtained by the statistical model indicated that the mathematical model of the first order explained 96.11% of the variability of Td and the correlation of predicted versus observed values was considered very strong, which presented a value of 0.9818. Along with the structural and morphological study it was possible to identify the partial compatibility between PMMA and MMT H +.
Desde os primeiros estudos relatados pelo grupo de pesquisa da Toyota na década de 90, nanocompósitos polímero/argila tem atraído grande interesse devido às suas propriedades e aplicações. A adição de pequenas quantidades de argila na matriz polimérica promove um potencial aumento nas propriedades físicas, químicas e térmicas, tais como retardância de chama, aumento da estabilidade térmica e revestimentos anticorrosivos. A morfologia desses nanocompósitos depende fortemente das condições de síntese, tais como o teor de argila, o método de síntese, o tipo de polímero, entre diversos outros. Desta forma, a utilização de um planejamento experimental multivariável para avaliar o efeito das variáveis experimentais sobre as propriedades dos nanocompósitos é de grande relevância. No presente estudo, nanocompósitos obtidos a partir da co-polimerização do poli(metacrilato de metila), PMMA e do poli metacrilóxi propril trimetoxisilano, PMTPS formando o PMMA-co-PMPTS com adição de argila montmorilonita protonada (MMT H+) foram preparados via polimerização in situ utilizando-se peróxido de benzoíla (BPO) como iniciador térmico. Sistemas de planejamento fatorial (quatro fatores em dois níveis) foram utilizados para estudar a influência das variáveis experimentais (MMA, MPTS, MMT H+ e BPO) sobre as propriedades térmicas de nanocompósitos (PMMA-co-PMPTS) / MMT H+ obtidos por termogravimetria. A estrutura e morfologia foram estudadas por difração de raios X, espectroscopia de absorção na região do infravermelho e microscopia eletrônica de transmissão. O estudo das propriedades térmicas por meio do planejamento fatorial mostrou que a amostra preparada pela combinação de 150 mmol de MMA, 23 mmol MPTS, 0,186 mmol BPO e 0,150 g MMT H + (experimento 7, AM7) apresentou o maior valor de Temperatura de despolimerização (Td) (381 °C). O valor do coeficiente de determinação R2 obtido pelo modelo estatístico indicou que o modelo matemático de primeira ordem explicou 96,11 % da variabilidade da Td, e a correlação dos valores preditos versus observados foi considerada fortíssima, o qual apresentou um valor de 0,9818. Com o estudo estrutural e morfológico dos nanocompósitos foi possível identificar a parcial compatilização entre o PMMA e a MMT H+.

For many applications a common source of performance degradation is excessive processor stalling from high memory latencies or poor data placement. Performance degradations from program and memory hierarchy interactions are often difficult for programmers and compilers to correct due to a lack of run-time information or limited knowledge about the underlying problem. By leveraging the Pentium 4 processor's performance monitoring hardware, specific run-time information can be provided, allowing code modifications to reduce or even eliminate problematic code, resulting in reduced execution times.
Furthermore, many tools currently available to aid programmers are program counter centric. These tools point out which area of the code produce slowdowns, but they do not directly show where the problem data structures are. This is a common problem in programs that dynamically allocate memory. By creating a ?malloc-centric? tool, we can develop an interesting perspective of the memory behavior of the system, providing better insight into the sources of performance problems.

This thesis consists of two parts: In the first part we describe the Photomultiplier Tube (PMT) selection and testing processes for the Hadronic Forward (HF) calorimeter of the CMS, a Large Hadron Collier (LHC) experiment at CERN. We report the evaluation process of the candidate PMTs from three different manufacturers, the complete tests performed on the 2300 Hamamatsu PMTs which will be used in the HF calorimeter, and the details of the PMT Test Station that is in University of Iowa CMS Laboratories. In the second part we report the Cascade_c_+ lifetime measurement from SELEX, the charm hadro-production experiment at Fermilab. Based upon 301+-31 events from three different decay channels, by using the binned maximum likelihood technique, we observe the lifetime of Cascade_c_+ as 427+-31+-13 fs.

The flavor oscillations of neutrinos due to the mixing of mass eigenstates have been thoroughly studied in several experiments. One missing piece of the puzzle is the mixing angle θ13, which is being searched for by the Daya Bay experiment. Currently, the experiment is still in construction mode. Part of the experiment involves building effective detectors for atmospheric muons, resulting in accurate detection of antineutrinos from the source. To ensure accurate detection, we must effectively calibrate the PMTs with the use of carefully chosen and calibrated LEDs. This thesis details the study of several LEDs measured in an attempt to determine the properties of the most likely source for our calibration efforts. I measured the spectra of the LEDs meant for use in calibration, along with several others for the purpose of comparison of spectrum width and to find the evidence of fluorescence in the LEDs.
Master of Science

Numerous and convincing are the experimental evidences that led to the believe that most of the Universe is constituted by the so-called Dark Matter (DM). Its research has attracted many experimental efforts to the point of being considered the greatest mystery of physics. The most promising candidates to DM are generically named as WIMPs, an acronym for Weakly Interacting Massive Particles.The detectors that have reached the most competitive sensitivity levels have in common the characteristics of being built with ultrapure materials and located underground, shielded from cosmic rays. The XENON project,located at the Laboratori Nazionali del Gran Sasso (LNGS). The XENON1T experiment employed a dual-phase Time Projection Chamber (TPC) with 2t of xenon active mass. The next step of the detector is XENONnT, and is currently in the final assembling stage. With a bigger TPC containing 6t of xenon active mass, the main goal is to improve the detection potential for WIMPs by increasing the sensitivity of one order of magnitude in five years of data taking. That result can be achieved only with a substantial background lowering attained with a reduction of the contaminants of the xenon as well as of the detector materials and finally, with the Neutron Veto system (nVeto); the latter is a detector which tags the radiogenic neutrons coming from the materials of the experiment. The nVeto will employ the gadolinium-loaded water technology to significantly enhance the neutron capture cross-section. It will be instrumented with 120 8'' Hamamatsu R5912 photomultipliers (PMT) featuring high quantum efficiency and low radioactivity. Most of the work done to design and realize the nVeto is the argument of this thesis. In addition, an extensive study of the nVeto PMT performance has been done in a dedicated experimental setup at the LNGS. The complete description of the setup,as well as the results of the nVeto PMT tests, is the other big topic of this thesis.

Glassy dynamics of polymethylphenylsiloxane (PMPS) is studied by broadband dielectric spectroscopy in one-dimensional (1D) and two-dimensional (2D) nanometric confinement; the former is realized in thin polymer layers having thicknesses down to 5 nm, and the latter in unidirectional (thickness 50 µm) nanopores with diameters varying between 4 and 8 nm. Based on the dielectric measurements carried out in a broad spectral range at widely varying temperatures, glassy dynamics is analyzed in detail in 1D and in 2D confinements with the following results: (i) the segmental dynamics (dynamic glass transition) of PMPS in 1D confinement down to thicknesses of 5 nm is identical to the bulk in the mean relaxation rate and the width of the relaxation time distribution function; (ii) additionally a well separated surface induced relaxation is observed, being assigned to adsorption and desorption processes of polymer segments with the solid interface; (iii) in 2D confinement with native inner pore walls, the segmental dynamics shows a confinement effect, i.e., the smaller the pores are, the faster the segmental dynamics; on silanization, this dependence on the pore diameter vanishes, but the mean relaxation rate is still faster than in 1D confinement; (iv) in a 2D confinement, a pronounced surface induced relaxation process is found, the strength of which increases with the decreasing pore diameter; it can be fully removed by silanization of the inner pore walls; (v) the surface induced relaxation depends on its spectral position only negligibly on the pore diameter; (vi) comparing 1D and 2D confinements, the segmental dynamics in the latter is by about two orders of magnitude faster. All these findings can be comprehended by considering the density of the polymer; in 1D it is assumed to be the same as in the bulk, hence the dynamic glass transition is not altered; in 2D it is reduced due to a frustration of packaging resulting in a higher free volume, as proven by ortho-positronium annihilation lifetime spectroscopy.

Portfolio diversification has been a subject frequently addressed since the publications of Markowitz in 1952 and 1959. However, the Modern Portfolio Theory and its mean variance framework have been criticized. The critiques refer to the assumptions that return distributions are normally distributed and the symmetric definition of risk. This paper elaborates on these short comings and applies a heuristic downside risk approach to avoid the pitfalls inherent in the mean variance framework. The result of the downside risk approach is compared and contrasted with the result of the mean variance framework. The return data refers to the real estate sector in Sweden and diversification is reached through property type and geographical location. The result reveals that diversification is reached differently between the two approaches. The downside risk measure applied here frequently diversifies successfully with use of fewer proxies. The efficient portfolios derived also reveals that the downside risk approach would have contributed to a historically higher average total return. This paper outlines a framework for portfolio diversification, the result is empirical and further research is needed in order to grasp the potential of the downside risk measures.

Cette thèse aborde un problème de transport appelé le Problème de m-Tournées Sélectives (PmTS) ou ”Team Orienteering Problem” en anglais. Le PmTS consiste à construire m tournées pour une flotte de véhicules afin de desservir un sous-ensemble sélectionné de clients. Dans le PmTS un service est fourni à chaque client visité en contrepartie de quoi, un gain est récolté. La tournée de chaque véhicule part d'un dépôt, passe par un sous-ensemble de clients et revient en un autre sans dépasser la longueur maximale autorisée. Chaque client peut être desservi au plus une fois par un unique véhicule. L'objectif est de maximiser le gain total récolté. Le PmTS étant un problème NP-difficile, notre objectif de recherche a consisté à proposer des heuristiques basées sur le principe général de ”Cluster first - Route second”. Ces algorithmes sont prévus pour être intégrés dans un logiciel de planification des tournées de techniciens de maintenance.

The first 900 four-anode Photomultiplier Tubes (PMTs) have been evaluated for use in the 2013 Hadronic Forward (HF) calorimeter upgrade. HF is a part of the Compact Muon Solenoid (CMS), which is one of the two large general-purpose particle detectors of the Large Hadron Collider (LHC) at CERN in Geneva, Switzerland. HF requires 1728 PMTs. These small tubes are the sensitive light detectors that provide the output signals of HF. Before installing PMTs in HF, their quality control demands need to be satisfied. These tests, done at the University of Iowa, are designed in three categories to test seventeen different parameters for each PMT. The three most basic and most important groups of parameters are: dark current, gain (anode and cathode), and timing. There are secondary tests which are performed on a smaller percentage of the PMTs such as surface uniformity, double pulse and single photo-electron resolution. The PMTs that meet the specifications of HF will be sent to CERN where they are expected to be in use for at least a decade.

碩士
國立臺灣大學
化學學系
85
Polymethylphenylsiloxane (PMPS) / polydiphenylsiloxane (PDPS) diblock copolymers with various degree of polymerization (DP) are synthesized through a living anionic ring-opening polymerization from hexaphenylcyclotrisiloxane (P3) and l,3,5-trimethyl-l,3,5-triphenylcyclo -siloxane (D3Ph), using n-butylithium as initiator, THF as solvent, diphenylraethylchlorosilane as terminator. These copolymer were characterized by GPC and NMR. The thermal properties of PMPS/PDPS copolymers are discussed via the chemical composition of the copolymers. The glass transition temperature (Tg) and mesophase transition temperature (Tm) of these copolymers were determined by Differential Scanning Calorimetry (DSC). It was found that the Tm was strongly dependent on the DP of PDPS in the copolymers with DP of PDPS less than 15. The fractionation and recrystallization phenomena are also found in these copolymers during DSC scanning. The thermal stabilities (Tm) of these copolymers were measured by Thermogravimeter analysis (TGA) and it was found that the) thermal stabilities T10 were improved with the increasing DP of PMPS. It was also revealed that T10 is strongly dependent on DP of PDPS. In addition, the isotropic temperatures (Ti) of the PMPS/PDPS copolymers were measured by the Polarized Optical Microscopy (POM) and the relationship between Ti and DP of PDPS was discussed. Based upon the POM and DSC result, the crystalline phase, mesophase and isotropic phase could be identified, and phase diagrams of these copolymers were established. Upon the results of temperature-variation wide angle X-ray diffraction (WAXD), the diffraction peak at low angle for mesophase was found to be intensely sharp and showed a distinct difference from the broad one for isotropic phase.

碩士
國立臺灣大學
化學學系
86
Series of Polymethylphenylsiloxane (PMPS)/Polydiphenylsiloxane (PDPS) statistical random copolymers with different PDPS content were synthesized through a living anionic copolymerization from hexaphenylcyclotrisiloxane (P3) and 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxaiie (D3Ph) in various solvent system, using n-butyllithium as initiator, and diphenylmediylchlorosilane as terminator. These copolymers were characterized by GPC and 1H-NMR. The monomer reactivity ratios of the D3Ph/P3 copolyinerization in various solvent system were estimated from Fineman-Ross equation. The monomer sequence of the copolymers was confirmed by the 1H-NMR and the glass transition temperature (Tg) of the synthesized copolymers. The Tg and mesophase transition temperature (Tm) of these copolymers were determined by Differential Scanning Calorimeter (DSC). The isotropic temperature (Ti) of the copolyiners were measured by the Polarized Optical Microscopy (POM). Basing upon DSC and POM results, the phase diagrams of these copolymers were established. The thermal stability (T10) of these copolymers were measured by Thermogravimetry Analysis (TGA).

In this thesis, I describe studies identifying and characterizing two putative stem cell populations of the neural and pancreatic lineages. The mechanisms governing the emergence of the earliest mammalian neural cells during development and the ontogeny of neural stem cells remain incompletely characterized. A default mechanism has been suggested to underlie neural fate acquisition, however an instructive process has also been proposed. I utilized mouse ES cells to explore the fundamental issue of how an uncommitted, pluripotent mammalian cell will self-organize in the absence of extrinsic signals, and what cellular fate will result. Individual ES cells were found to rapidly transition directly into neural cells by a default mechanism, a process shown to be independent of suggested instructive factors. Further, I provide evidence that the default neural identity is that of a primitive neural stem cell, the earliest identified stem cell of the neural lineage. The exiguous conditions used to reveal the default state were found to present primitive neural stem cells with a survival challenge, which could be mitigated by survival factors or genetic interference with apoptosis. I also report the clonal identification of multipotent precursor cells, PMPs, from the adult mouse and human pancreas. These cells proliferate in vitro to form clonal colonies and display both pancreatic and neural cell multipotentiality. Importantly, the newly generated beta cells demonstrate glucose-dependent calcium responsiveness and regulated insulin release. PMP colonies do not express markers of embryonic stem cells, nor genes suggestive of mesodermal or neural crest origins. Moreover, genetic lineage-labeling experiments excluded the neural crest, and established the embryonic pancreatic lineage, as the developmental source of PMPs. The PMP cell was further found to express insulin in vivo, and insulin+ stem cells were shown to contribute to multiple pancreatic and neural cell populations in vivo. These findings demonstrate that the adult mammalian pancreas contains a population of insulin+ multipotent stem cells, capable of contributing to the pancreatic and neural lineages. In the final section of this thesis, I consider the relationships between neural and pancreatic tissues, as well as discussing the relevance of these two novel stem cell populations.

Um parâmetro importante para a medida do desempenho de um detector é a sua linearidade de resposta. No TileCal, um calorímetro hadrónico de telhas cintilantes, a luz de cintilação é transmitida por fibras ópticas, com mudança do comprimento de onda, para leitura por tubos fotomultiplicadores (PMT). Estes têm de ter uma resposta que aumenta linearmente com a intensidade de luz recebida, a qual será proporcional à energia depositada pelas partículas no calorímetro. Para medir a linearidade dos PMT recorrese a um sistema laser que envia, simultaneamente, uma quantidade bem definida de luz, monitorizada por PMT e fotodíodos instalados dentro da caixa do laser, para todos os cerca de 10000 PMT do TileCal. Neste trabalho desenvolveu-se software de análise de dados, recorrendo ao programa ROOT, para o estudo da linearidade de resposta dos PMT.

Dissertação de Mestrado apresentada no ISPA – Instituto Universitário para obtenção de grau de Mestre em Biologia Marinha e Conservação
Os cetáceos, como predadores de topo, são elementos chave do meio marinho e devem ser priorizados em estratégias de conservação marinha. Os projetos de ciência cidadã contam com a participação de qualquer cidadão na recolha de dados científicos, favorecendo assim o avanço da ciência. O presente estudo disponibiliza informação, com base em fontes de informação não-convencionais (ciência cidadã e inquéritos dirigidos), relativa à abundância e distribuição horizontal de cetáceos e avalia o contributo da ciência cidadã para o estudo da ocorrência e distribuição espacial de cetáceos no Parque Marinho Professor Luiz Saldanha (PMPLS) e na Reserva Natural das Berlengas (RNB), em Portugal. O golfinho-comum e o golfinho-roaz foram as espécies mais reportadas via ciência cidadã na plataforma BioDiversity4All (Projeto CETASEE) e mencionadas num maior número de inquéritos, nas AMPs em estudo e zonas adjacentes. Algumas espécies, como o grampo e a orca também foram reportados na plataforma nas áreas de estudo. A ciência cidadã poderá tornar-se uma fonte de recolha de dados sistemáticos sobre a ocorrência e distribuição espaciotemporal de cetáceos e, nesse sentido, deve integrar estudos científicos e ser tida em consideração em medidas de conservação e gestão aplicadas às AMPs. Outras metodologias, como a utilização de DNA ambiental e de censos visuais e a criação de programas de monitorização acústica passiva e de monitorização de populações são também apontadas para preencher a lacuna de conhecimento científico relativa à ocorrência e distribuição de cetáceos em Portugal.
Cetaceans, as top predators, are key elements of the marine environment and should be prioritized in marine conservation strategies. Citizen science projects count on the participation of any citizen in the collection of scientific data, thus favoring the advancement of science. The present study provides information, based on non-conventional sources of information (citizen science and targeted surveys), regarding the abundance and horizontal distribution of cetaceans and assesses the contribution of citizen science to the study of the occurrence and spatial distribution of cetaceans in the Professor Luiz Saldanha Marine Park (PMPLS) and in the Berlengas Nature Reserve (RNB), in Portugal. The common dolphin and bottlenose dolphin were the most reported species via citizen science on the BioDiversity4All platform (CETASEE Project) and mentioned in a greater number of surveys, in the AMPs under study and adjacent areas. Some species, such as the clamp and the orca, were also reported on the platform in the studied areas. Citizen science can become a source of systematic data collection on the occurrence and spatiotemporal distribution of cetaceans and, in this sense, it must integrate scientific studies and be taken into account in conservation and management measures applied to AMPs. Other methodologies, such as the use of environmental DNA and visual censuses and the creation of passive acoustic monitoring and population monitoring programs are also aimed at filling the scientific knowledge gap regarding the occurrence and distribution of cetaceans in Portugal.

Ultrasonic sensors are well known for various applications such as NDT, ultrasound imaging, and proximity sensing. Conventional ultrasound transducers are bulky, work at notoriously high voltages, and consume significant power. Microfabrication techniques are leading to a paradigm shift in the field of ultrasonics by enabling development of low power - small footprint ultrasound transducers. This work focuses on the development of piezoelectric type flexural mode micromachined ultrasound transducer also known as PMUTs. We start by establishing a system level analytical model of a PMUT and use it to offer insights into scaling of the performance of the transducer with respect to various design parameters. In this analysis we give special attention to residual stresses thus establishing a contrast between membrane type and plate type PMUTs. After going through various steps of material development and microfabrication, we obtain arrays of PMUTs with different designs. PZT thin films deposited by sol-gel method are used as the piezoelectric layer in the multilayer stack. Further, we present a thorough characterization of fabricated PMUTs which includes measurement of the piezoelectric properties of the embedded PZT thin film, electrical impedance of the electromechanical transducer, its vibrational charac-teristics and acoustic radiation from a single PMUT cell. We also develop a pre-amplifier circuit for a PMUT receiver and present its working as a simple proximity sensor. After establishing the repeatability and predictability of our PMUT sensors we delve into application development beyond ultrasound imaging. Experiments and analysis of PMUTs submerged in water show strong structural-acoustic coupling between the PMUT membrane and the surrounding fluid. We hypothesize the applicability of this feature to sense changes in the acoustic environment of a PMUT. To this end, we integrate an array of PMUTs with a micro-fluidic chip and study the changes in the vibrational behaviour of the PMUT in response to change in the air-water ratio in a closed cell around a PMUT membrane. We also present our preliminary results on presence of micro-bubbles in the closed cell around the PMUT.

Tese de mestrado integrado, Engenharia Física, Universidade de Lisboa, Faculdade de Ciências, 2019
O sistema atual de distribuição de alta tensão do calorímetro hadrónico central da experiência ATLAS do CERN, TileCal, foi fabricado no final dos anos 90. Este foi projectado para estar em funcionamento durante 10 anos, no entanto jáa se encontra em funcionamento há cerca de 20 anos. Atualmente, muitos dos componentes utilizados encontram-se obsoletos o que impossibilita a sua reparação e reutilização. Por outro lado, o sistema atual encontra-se no interior da caverna ATLAS, logo encontra-se exposto a altos níveis de radiação. Esta exposição contínua a altos níveis de radiação resultantes das colisões entre os feixes de partículas, que ocorrem no LHC (Large Hadron Collider), afeta todo o sistema. O facto de o sistema se encontrar na caverna suscita ainda outros problemas, tais como, a dificuldade de reparar ou mesmo substituir qualquer componente ou placa constituinte do sistema eletrónico, danificado pela radiação ou devido ao envelhecimento eletrónico. Para se efetuar a reparação ou a substituição de componentes ou placas é necessário que o LHC pare o seu funcionamento durante alguns meses, de modo a que os níveis de radiação diminuam o suficiente para permitir que um técnico possa entrar na caverna, porém esta pausa de meses só oferece um tempo muito limitado para executar esta tarefa. Para além destes problemas tem-se ainda como um dos objetivos o aumento da luminosidade do LHC, o que vai implicar um aumento do nível de radiação na caverna ATLAS. Outro dos objetivos, é a diminuição do intervalo de tempo entre as colisões de partículas, levando à necessidade de electrónica mais rápida. Todos estes problemas e novos objetivos fazem com que seja necessário atualizar e/ou modificar toda a electrónica do TileCal. De forma a superar estes problemas, foi proposta uma actualização: um novo sistema de distribuição de alta tensão (HVDS) será colocado fora da caverna onde se encontra o detetor, passando este a ser um sistema remoto que não é afetado pela radiação, maximizando assim a fiabilidade e a robustez do sistema. A eletrónica deste novo sistema será colocada numa sala sem radiação, localizada 100 metros acima da caverna ATLAS, o que permitirá o acesso permanente ao sistema de distribuição de altas tensões. Assim, deixa de ser necessária a existência de uma paragem do funcionamento do LHC para executar reparações no sistema. Outra vantagem inerente ao sistema remoto é deixar de haver uma limitação de tempo disponível para realizar as reparações e/ou substituições, diminuindo também o risco a que o técnico está sujeito quando as executa. Para este novo sistema é necessário produzir uma placa dedicada que forneça as alimentações primárias necessárias, alta e baixa tensão, dado que no sistema atual as fontes de alimentação primárias de baixa tensão encontram-se na caverna ATLAS e as de alta tensão embora se encontrem na sala sem radiação já referida são fontes lineares de elevado custo. O trabalho apresentado nesta dissertação insere-se na colaboração portuguesa no projeto ATLAS/CERN. Este consiste no desenvolvimento de uma placa de alimentação, designada por Power Supplies, capaz de fornecer tanto a alta tensão (HV), - 830 V a -950 V, como as baixas tensões ,±12 V e 3; 3 V, sendo imperativo que todas as tensões produzidas tenham baixo ruído. Para produzir estas tensões recorreu-se à utilização de quatro conversores DC/DC, sendo que dois dos conversores DC/DC são utilizados para produzir a alta tensão, -830 V a -950 V @ 10 mA, e os restantes dois para as baixas tensões, um para os 3:3 V @ 0:8 A, e o outro que é um conversor DC/DC duplo para os ±12 @ 2:5 A. Cada HVDS fornece a alimentação para 48 fotomultiplicadores (PMTs) do detetor. Devido à corrente necessária para alimentar todos os PMTs, é necessário recorrer ao uso de dois conversores DC/DC para produzir a alta tensão. Os valores da tensão de saída dos conversores DC/DC de alta tensão são controlados digitalmente, podendo fornecer dois valores diferentes, -830 V ou -950 V. Estes valores de tensão distintos permitem que cada PMT do detetor possa receber a tensão adequada para funcionar corretamente. Dado que não existe um único componente que seja igual a outro, cada PMT terá as suas características próprias e, portanto, a sua tensão de alimentação deve ser ajustada para se obter o melhor desempenho do detetor. Estes dois valores de tensão permitem a correta calibração de todos os PMTs efetuada pelo sistema de distribuição das altas tensões. A placa que fornecerá as alimentações ao HVDS, deverá ainda oferecer algumas funcionalidades extra, tais como: a possibilidade de uma monitorização em tempo real do consumo em tensão e corrente de cada conversor, a leitura da temperatura em dois pontos diferentes da placa, a capacidade de ligar/desligar digitalmente cada um conversores DC/DC individualmente e ligar/desligar manualmente todos os conversores DC/DC ao mesmo tempo, através de um interruptor. Este último serviáa como medida de segurança caso o método digital não funcione ou em caso de substituição ou manutenção do sistema sem necessidade de recorrer ao sistema de controlo digital do ATLAS. O controlo digital da placa Power Supplies será baseado num protocolo de comunicação SPI e num expansor série/paralelo. Os sinais de saída do referido expansor serão os sinais para ligar/desligar os conversores, os sinais de seleção de tensão de saída dos conversores de alta tensão e os sinais que permitem a leitura adequada e em tempo real dos consumos de tensão e de corrente e dos sensores de temperatura utilizados. Estas leituras são efetuadas recorrendo ao controlo digital de um multiplexador analógico e a um conversor analógico digital (ADC). Ainda no âmbito desta tese, à apresentada a interface gráfica de utilizador (GUI) desenvolvida na linguagem de programação Python. Esta foi utilizada para facilitar a comunicação entre a placa Power Supplies e o utilizador. A interface gráfica está dividida em três secções diferentes, de forma a ser mais intuitiva para o utilizador. A primeira secção é a secção responsável por ligar/desligar os conversores DC/DC, sendo que esta apresenta quatro caixas de seleção, uma para cada conversor, que quando selecionadas pelo utilizador, executam o código responsável por enviar a instrução ao expansor para enviar o sinal de ligar/desligar para os conversores DC/DC selecionados. Na segunda secção encontram-se representadas duas barras deslizantes, às quais se encontra associado um cursor que se pode deslocar entre duas posições distintas, associadas à selecção da tensão de saída de cada um dos conversores DC/DC de alta tensão. Associada à posição do cursor encontra-se também um texto informativo que permite que o utilizador verifique se a tensão seleccionada é a pretendida. A terceira e última secção é a da leitura dos consumos de tensão e de corrente assim como das duas temperaturas lidas por dois sensores de temperatura colocados em pontos distintos da carta. Esta leitura pode ser feita de duas formas diferentes, pode ser feita uma única medida através da seleção de botões dedicados que apenas permitem selecionar uma opção de cada vez, sendo o resultado da leitura apresentado em duas caixas. A primeira caixa com a leitura em contagens do ADC, que é o valor que o ADC fornece diretamente, e a segunda caixa com a leitura do valor correspondente ao que se está efetivamente a medir com a respetiva unidade física. A outra forma envolve um conjunto várias medições contínuas de uma das grandezas anteriormente referidas, sendo que o utilizador pode escolher o número de medições pretendidas e o intervalo de tempo entre cada medida. Os valores lidos/medidos através deste método são apresentados em gráficos diferentes em função do tempo atualizados em tempo real, sendo possível guardar estes dados num ficheiro do tipo csv. O trabalho desta dissertação consistiu no desenvolvimento de uma placa que irá fornecer as alimentações primárias necessárias para o novo sistema de distribuição de alta tensão, e no desenvolvimento da interface gráfica de utilizador dedicada para esta placa que permitirá o seu teste funcional e que será mais tarde migrada para o teste de controlo digital do ATLAS.
The current system that distributes high voltage to the hadronic calorimeter TileCal of the ATLAS experiment at CERN was manufactured in the late 1990s and now many of its components are obsolete. In addition to this, the continuous exposition to high levels of radiation that results from the LHC collision affects the whole system. The calorimeter itself will be upgraded and a faster and low noise electronic will be needed. Given this, an update was proposed to mitigate these problems: a new high voltage distribution system (HVDS) placed outside of the detector, a remote system which will not be affected by the radiation, that maximize the reliability and robustness of the system. For this new system it is necessary to produce a dedicated board that provides the necessary primary supplies. Therefore, the presented work consists in the development of a power supply board capable of providing both high voltage (HV), 􀀀830 V and 􀀀950 V, and low voltage, _12 V and 3:3 V, with low noise, resorting to DC/DC converters. Each HVDS provides the supply to 48 photomultipliers tubes (PMTs) of the detector. Due to the current needed, two high voltage sources are available, each one to supply just half of the PMTs. The values of the provided HV supplies are digitally controlled to one of the referred values, so each PMT of the detector can receive the right voltage to work correctly. Besides that, this board is controlled by a serial peripheral interface (SPI) communication protocol and has an analog to digital converter (ADC) and an analog multiplexer that are used to provide the user monitoring of all supply voltages and currents in real-time as well as the temperature, in two different positions of the board, in real time. A graphical user interface (GUI) has also been developed which allows easy communication between the power supply board and the user.