Les Photomultiplicateurs Silicium (SiPM) sont devenus aujourd’hui des détecteurs de lumière visible, applicables dans de nombreux domaines comme la Physique des Hautes Énergies, les expériences Neutrinos, la détection de fluorescence, pour des applications de biophotonique ou d’imagerie médicale. La première partie de ma thèse concerne l’étude des divers paramètres physiques des SiPM en fonction de température T. En particulier, des composants récents (2015) de KETEK ayant diverses caractéristiques technologiques comme des jonctions p/n ou n/p, avec ou sans « trench » entre cellules, différentes épaisseurs de couches épitaxiales, etc… ont été étudiés dans la gamme de T de 308.15 K (+35°C) à 238.15 K (-35°C). En plus, des composants Hamamatsu de production 2011, ainsi que de production 2015 avec des caractéristiques technologiques améliorées (faible bruit), ont été testés dans la gamme 318.15 K (+45°C) à 98.15 K (-175°C). Pour ces études, j’ai participé à la conception, l’installation, la mise en service et la calibration d’un banc cryogénique destiné aux caractérisations électriques, optiques, et en température, des SiPM. J’ai développé une procédure d’analyse automatisée, capable de traiter en un temps très court une énorme quantité de données expérimentales (i.e. dizaines de Gb/détecteur), et de fournir une information rapide et précise sur les principaux paramètres et leur dépendance en T. J’ai développé un modèle physique décrivant les courbes IV en DC pour différentes T. Ce modèle proposé reproduit bien la forme de la courbe IV dans une large gamme de courants allant de 10⁻¹² à 10⁻⁵ A sur toute la zone de fonctionnement des divers détecteurs. Ainsi, le modèle IV peut être utilisé comme un outil simple et rapide pour déterminer les paramètres du SiPM comme le VBD, la forme de la courbe PGeiger en fonction de Vbias, ainsi que la plage des tensions de fonctionnement. La comparaison de ces paramètres avec ceux obtenus en mesure AC, et analysés par la procédure automatisée, sont en bonne concordance. La seconde partie de ma thèse a porté sur l’étude de composants SiPM spécialement adaptés à une application biomédicale. Il s’agit d’une sonde intracérébrale, sensible à l’émission β (Nβ) de molécules marquées par un traceur radioactif, injectées dans le cerveau d’un animal vivant. Le but étant de construire un nouveau "modèle animal" de maladies humaines telles que les maladies neuro-dégénératives ou neuropsychiatriques et la croissance de tumeurs. Cette sonde se compose d’un SiPM de très petite taille, bas bruit, couplé à une fibre scintillante, suivie d’une électronique de lecture spécifique, miniaturisée, à faible consommation. Ces SiPM ont été choisis comme les plus adaptés à notre application : deux SiPM de KETEK de 0.5x0.5 mm² (spécialement développés par cette compagnie pour nos besoins), et un SiPM standard de 1.3x1.3 mm² de Hamamatsu, tous ayant des μ-cellules de 50 × 50 μm². Pour chaque composant, les paramètres G, DCR et la sensibilité β ont été mesurés en fonction de Vbias et T. Les résultats obtenus montrent que le faible champ de vue des nouvelles structures KETEK permet une bonne amélioration du DCR. Cependant ce faible champ de vue entraîne une perte de collection de lumière due à l’épaisseur de la couche de résine époxy de protection, et à l’angle d’acceptante de la fibre. Comme la sensibilité β est un compromis entre le PDE et le DCR, les SiPM de KETEK montrent au final des performances voisines de celles de Hamamatsu. Les résultats préliminaires démontrent que la sensibilité β de KETEK peut être améliorée significativement en utilisant une lentille de focalisation entre la fibre scintillante et le SiPM, ou en diminuant l’épaisseur de la couche de résine époxy de protection. / Silicon PhotoMultiplier (SiPM) detector has become a suitable visible light/photon detector for many applications like high energy physics and neutrino experiments, fluorescence detection, bio-photonics and medical imaging. The first part of my thesis was oriented to the studies of SiPM physics parameters as a function of temperature. Particularly, recent KETEK devices (year 2015) with different technological characteristics like p/n and n/p junctions, with and without trench technology, and different widths of epitaxial layer were studied in the temperature range from 308.15 K (+35°C) down to 238.15 K (-35°C). In addition, the Hamamatsu devices from 2011 production run as well as new devices from 2015 year, with improved technological characteristics inducing a reduced noise, were investigated in a wider temperature range from 318.15 K (+45°C) down to 98.15 K (-175°C). For these purposes, I participated to the design, installation, commissioning and calibration of a cryogenic experimental setup dedicated to electrical, optical and temperature studies of SiPM devices. Also, I have developed an automatic analysis procedure able to handle in a short time an impressive quantity of experimental data (i.e. tens of Gb/device) and to give a precise and fast information on main SiPM parameters and their temperature dependence. I have also developed a physical modeldescribing the DC I-V curves of SiPM detectors at different temperatures. The proposed model fits well the shape of IV curve in a very large currents range from 10⁻¹² A up to 10⁻⁵ A over the full working range of various devices. Consequently, the IV model can be used as a simple and fast method for determination of SiPM parameters like breakdown voltage VBD, the shape of Geiger triggering probability PGeiger as a function of Vbias as well as the Vbias working range. The comparison of these parameters with those calculated from AC measurements and analyzed by the automatic procedure showed a good agreement. The second part of my thesis was oriented to the study of SiPM devices and their physical parameters required to build a prototype of betasensitive intracerebral probe. Such probe is dedicated to measure the local concentration of radiolabeled molecules on awake and freely moving animal and to study new animal models of human disorders (neurodegenerative diseases, tumor growth, and neuropsychiatric disorders). It is composed of small size, low-noise SiPM device coupled to a scintillating fiber and readout by a dedicated miniaturized low-power consumption electronics. Three SiPM devices have been chosen as the most adapted for our application: two small KETEK devices of 0.5×0.5 mm² size (with and without optical trenches, specially developed by KETEK to fulfill our requirements) and a standard Hamamatsu device of 1.3×1.3 mm² size, all devices having 50 × 50 μm² μcell size. For each SiPM the gain G, dark count rate DCR and beta sensitivity were measured as a function of Vbias and temperature. The obtained results showed that the small field of view and newly developed structure of the KETEK devices allow a large decrease of the dark count rate DCR. However, this small field of view also leads to a reduced light collection due to the thickness of the epoxy protection resin on top of the SiPM and the acceptance angle of the fiber. Since the beta sensitivity represents a tradeoff between photon detection efficiency PDE and dark count rate DCR, KETEK SiPMs exhibit similar performances in comparison with the Hamamatsu device. Preliminary results demonstrate that the beta sensitivity of KETEK devices can be significantly improved by using focusing lens between the scintillating fiber and the SiPM or by reducing the thickness of its epoxy protection resin.

No description available.

The Qweak experiment has taken data to make a 2.5 percent measurement of parity violating elastic ep asymmetry in the four momentum transfer region of 0.0250 (GeV/c)2. This asymmetry is proportional to the weak charge of the proton, which is related to the weak mixing angle, sin2(thetaW). The final Qweak measurement will provide the most precise measurement of the weak mixing angle below the Z° pole to test the Standard Model prediction. A description of the experimental apparatus is provided in this dissertation. The experiment was carried out using a longitudinally polarized electron beam of up to 180 microampere on a 34.5 cm long unpolarized liquid hydrogen target. The Qweak target is not only the world’s highest cryogenic target ever built for a parity experiment but also is the least noisy target. This dissertation provides a detailed description of this target and presents a thorough analysis of the target performance. Statistical analysis of Run 1 data, collected between Feb - May 2011, is done to extract a blinded parity violating asymmetry of size--299.7 +/- 13.4 (stat.) +/- 17.2 (syst.) +/- 68 (blinding) parts-per-billion. This resulted in a preliminary proton’s weak charge of value 0.0865 +/- 0.0085, a 9% measurement. Based on this blinded asymmetry, the weak mixing angle was determined to be sin2(thetaW) = 0.23429 +/- 0.00211.

Hereditary Equine Regional Derma Asthenia (HERDA) is a painful disfiguring autosomal recessive skin disorder of Quarter Horse lineages. Affected horses cannot be ridden and most are humanely destroyed. Five years following homozygosity mapping of a putative causal mutation responsible for HERDA, it remains unclear how this mutation causes the HERDA syndrome. HERDA horses have a missense mutation in peptidyl-prolyl cis-trans isomerase B (PPIB) which encodes cyclophilin B (CYPB) and alters folding and post-translational modifications of fibrillar collagen. Loss of function mutations in CYPB recognized in other species classically present as the debilitating bone disease, severe to lethal osteogenesis imperfect (OI). Objectives of this study were to develop a novel method for cryogenic clamping of tendons and ligaments of high tensile strength and validate its performance by ultimate tensile strength testing of normal equine deep digital flexor tendon. This validated method was then used to compare tendon and ligament of HERDA vs. control horses along with great vessels and skin. We hypothesized that all tissues of high fibrillar collagen content would have altered tensile properties due to the CYPB mutation affecting fibrous connective tissue globally within HERDA horses. Based on previous studies in our laboratory identifying reduced hydroxylysine content and altered collagen crosslink ratios in the skin of HERDA affected animals that implicate lysyl hydroxylase-1 (LH1) dysfunction, we hypothesized that the HERDA PPIB mutation modified an interaction between CYPB and LH1, interfering with hydroxylysine synthesis and its availability for collagen crosslink formation. In addition, we hypothesized that mutant CYPB may also lead to modifications of other known CYPB protein complexes, such as the CYPB, prolyl-3 hydroxylase-1 (P3H1) and cartilage associated protein (CRTAP) triplex. Goals of this study were to investigate the tensile properties of tissues with high fibrillar collagen content from HERDA homozygotes, to elucidate the mechanistic relationship of the HERDA CYPB mutation to the clinical disease, and to provide evidence to substantiate a heterozygote phenotype in HERDA which could be useful to explaining the correlation between lineages that carry the HERDA allele and performance outcomes in the discipline of western cutting competition.

This research aims to investigate the influence of 3D through-thickness stitching on the gas permeability and transverse microcracking of cryogenically cycled carbon/epoxy composites. 3D through-thickness stitching can be used to improve the interlaminar properties of polymer matrix composites (PMCs) and produce lightweight, unitized structures for cryogenic storage tanks. To fully utilize stitched composite structures for these applications, their inherent gas permeability challenges must be understood. Therefore, in this study, the stitched composites' damage evolution and gas permeability was experimentally characterized under a) pure thermal stress, b) thermal and uniaxial mechanical stress, and c) thermal and biaxial mechanical stress. Helium gas permeability was measured for each specimen at room or cryogenic temperatures under a mechanically strained state following the thermo-mechanical cycles. Optical microscopy was used to measure microcrack densities and monitor their evolution through the thickness of the composite specimens. Thin plies, graphene nanoplatelets (GNP) modified resin, and a hybrid barrier layer comprising of both were incorporated in the stitched specimens as barrier layers to reduce their gas permeability. The dependence of gas permeability of stitched composites on the mechanical strain, test temperature, and load history was evaluated and correlated to microcrack density. A significant reduction in permeability and damage evolution (transverse microcracks and delaminations) was obtained for all thermo-mechanical cases using the hybrid barrier layer laminate. Additionally, the permeability was several orders of magnitude lower than the allowable. Overall, the hybrid barrier layer shows tremendous promise as a viable barrier layer for stitched/unstitched composites undergoing thermo-mechanical fatigue involving a cryogenic environment.

No description available.

Cryogenic carbon capture removes CO2 and other pollutants from flue and waste stream gases produced from the combustion of fossil fuels such as coal, natural gas, and oil and the production of cement. A transient, 1-dimensional numerical model was developed to study the temperature profile within a counter-current surface CO2 desublimation-falling liquid or solid heat exchanger. Effects of desublimation heat and mass transfer as well as convective and conductive heat transfer relationships were taken into account. Experiments show that CO2 can be captured on a falling spherical particle when appropriate column operating conditions are met.

Global warming is becoming ever increasing concern in our society. As such the likelihood of a carbon tax in the US is becoming increasingly likely. A carbon tax will be expensive enough that coal-based power plants will either have to install carbon capture technology or close. The two front runner technologies for carbon capture are amine scrubbing, and oxyfuel combustion. The downside is that both of these technologies increase power generation cost in a new plant by about 80% and have up to a 30% parasitic load, which reduces the cycle efficiency, that is, the power production per unit fuel consumed, by the same 30%. Retrofitting existing plants by either of these technologies is even more expensive and inefficient since it requires major modifications or replacement of the existing plant in addition to the new capture technology. Sustainable Energy Solutions (SES) has developed a carbon capture technology named cryogenic carbon capture (CCC). CCC is a process by which the flue gas cools to the point that CO2 desublimates. This process is more efficient, cheaper, and has about half of the parasitic load of other technologies, approaching the theoretical minimum in CO2 separation within heat exchanger and compressor efficiencies. This thesis conceptually describes, experimentally characterizes, and theoretically models one desublimating heat exchanger as an integral part of the CCC process. A spray tower conceptually developed by SES and theoretically and experimentally explored in previous work at lab scale is developed at bench scale in this work with accompanying major modifications to the theoretical model. It sprays a cold contact liquid to cool warm gas (relative to the contact liquid) that travels up the tower. Nominal operating temperatures are around -120 to -130 °C for 90% and 99% capture, respectively. Once the flue gas cools enough, CO2 desublimates on the liquid droplet surfaces and forms a slurry with the contact liquid. This spray tower can achieve arbitrarily high CO2 capture efficiency, depending on the temperature of the exiting gas and other operational variables. The experimental data outlined here varied these operational parameters over broad ranges to achieve capture efficiencies of 55% to greater than 95%, providing a robust data set for model comparison. The operational parameters explored include liquid temperature, liquid flow rate, gas flow rate, and droplet size. These data validated a transport and design model that predicts capture for future scale-up and design of the project. The data and model indicate expected behaviors with most of these variables and a dependence on internal droplet temperature profiles that may be higher than expected. This project significantly advanced the experimental database and the model capabilities that describe the spray tower.

Shape memory alloys (SMAs) possess the unique ability to change their shape by undergoing a solid-state phase transformation at a particular temperature. The shape change is associated with a large strain recovery as the material returns to its "remembered" shape. Their ability to act as both sensor and actuator has made them an attractive subject of study for numerous applications. SMAs have many characteristics which are advantageous in space-related applications, including generation of large forces associated with the strain recovery, smooth and controlled movements, large movement to weight ratio, high reliability, and spark-free operation. The objective of this work is the further development and testing of a cryogenic thermal conduction switch as part of NASA funded projects. The switch was developed to provide a variable conductive pathway between liquid methane and liquid oxygen dewars in order to passively regulate the methane temperature. Development of the switch concept has been continued in this work by utilizing Ni-Ti-Fe as the active SMA element. Ni-Ti-Fe exhibits the shape memory effect at cryogenic temperatures, which makes it well suited for low temperature applications. This alloy is also distinguished by an intermediate phase change known as the rhombohedral or R-phase, which is characterized by a small hysteresis (typically 1-2 deg C) and offers the advantage of precise control over a set temperature range. For the Ni-Ti-Fe alloy used, its thermomechanical processing, subsequent characterization using dilatometry and differential scanning calorimetry and implementation in the conduction switch configuration are addressed. This work was funded by grants from NASA KSC (NAG10-323) and NASA GRC (NAG3-2751).

This dissertation is concerned with the design of permanent magnet synchronous motors (PMSM) to operate at super-high speed with high efficiency. The designed and fabricated PMSM was successfully tested to run upto 210,000 rpm The designed PMSM has 2000 W shaft output power at 200,000 rpm and at the cryogenic temperature of 77 K. The test results showed the motor to have an efficiency reaching above 92%. This achieved efficiency indicated a significant improvement compared to commercial motors with similar ratings. This dissertation first discusses the basic concept of electrical machines. After that, the modeling of PMSM for dynamic simulation is provided. Particular design strategies have to be adopted for super-high speed applications since motor losses assume a key role in the motor drive performance limit. The considerations of the PMSM structure for cryogenic applications are also discussed. It is shown that slotless structure with multi-strand Litz-wire is favorable for super-high speeds and cryogenic applications. The design, simulation, and test of a single-sided axial flux pancake PMSM is presented. The advantages and disadvantages of this kind of structure are discussed, and further improvements are suggested and some have been verified by experiments. The methodologies of designing super high-speed motors are provided in details. Based on these methodologies, a super high-speed radial-flux PMSM was designed and fabricated. The designed PMSM meets our expectation and the tested results agree with the design specifications. 2-D and 3-D modeling of the complicated PMSM structure for the electromagnetic numerical simulations of motor performance and parameters such as phase inductors, core losses, rotor eddy current loss, torque, and induced electromotive force (back-EMF) are also presented in detail in this dissertation. Some mechanical issues such as thermal analysis, bearing pre-load, rotor stress analysis, and rotor dynamics analysis are also discussed. Different control schemes are presented and suitable control schemes for super high- speed PMSM are also discussed in detail.