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1
Hürlimann, Martin Dominik. "Cryogenic hydrogen maser." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/29116.
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A new type of atomic hydrogen maser that operates in a dilution refrigerator has been developed. In this device, the hydrogen atoms circulate back and forth between a microwave pumped state invertor in high field and the maser cavity in zero field.
A prototype maser with a small maser cavity has been built and the results obtained so far are encouraging. Stable maser oscillations were observed for temperatures of the maser bulb between 230 mK and 660 mK and for densities up to 3 x 1012cm⁻³. The short term frequency stability was measured with the help of two high quality quartz crystal oscillators by the three-cornered-hat method. The observed fractional frequency fluctuations for an averaging time of 1 s were 6.3 ± 3.7 x 10⁻¹⁴, which is lower than the results from the best room temperature masers. In conjunction with the stability measurements, the phase noise of the maser electronics was investigated. In particular, the temperature dependence of the phase noise of the cooled preamplifier was measured and it was shown that anomalous high noise levels between 2.2 K and 4.2 K are caused by the boiling of the liquid helium.
From the temperature dependence of the maser frequency, the binding energy E[sub B] of H on ⁴He could be determined to a high precision. The result is E[sub B] = 1.011 ± 0.010 K.
An extensive computer simulation program has been written that models the operation of the cryogenic hydrogen maser. It has been used to analyze and interpret some of the data. In addition, this simulation program is helpful for the design of an improved second generation cryogenic maser. Based on the present data and the model calculations, a new pumping scheme is proposed that is expected to increase the efficiency of the state invertor significantly.Science, Faculty of
Physics and Astronomy, Department of
Graduate
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Peddiraju, Naga Venkata Satya Pravin Kumar. "Modeling of cryogen leakage through composite laminates." Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/1329.
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Cryogenic composites find critical application in the manufacture of fuel tanks for reusable launch vehicles due to significant reduction in overall structural weight of the tank. These fuel tanks contain pressurized cryogen such as hydrogen at cryogenic temperatures. Exposure to varying temperatures and mechanical loads resulting from flight cycle, containment of pressurized cryogen causes thermo-mechanical loading of the composite. The thermo-mechanical loading cycles combined with anisotropy of the composite and mismatch in the thermal and mechanical properties of fibers and matrix lead to transverse matrix cracks (TMC) in each ply. TMC in adjacent plies intersect in localized regions at ply interfaces called crack junctions, which open up due to delamination on application of thermo-mechanical load. TMC and crack junctions usually form a network of leakage paths that assists leakage of cryogen through the composite. In this study, the volumetric flow rate of cryogen leaking through a damaged cross-ply composite with five plies is determined by estimating the effective conductance of the leakage paths. For a given damage state and applied load, crack junction and TMC openings are obtained by finite element analysis. A computational fluid dynamics model is first used to estimate the effective conductance of a leakage path to hydrogen leakage and then a simplified analytical model is used to compute the effective conductance from individual conductances of each crack junction and TMC through a series-parallel combination. A single phase flow model is considered for the numerical analysis of hydrogen flow through TMC and crack junctions. The simulations are carried out using a commercial computational fluid dynamics software, FLUENT. Parametric studies are carried out to investigate the dependence of leak rate of hydrogen on the irregularities of the TMC geometry and TMC, crack junction openings. The simplified model predictions of the effective conductance for the five ply composite show good comparison with numerical simulations.
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Bateman, Rodney William. "Cryogenic temperature sensor investigation." Thesis, Birkbeck (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313794.
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Connell, Anne Cumming. "Subsea cryogenic gas release." Thesis, University of Glasgow, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236051.
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Yang, Shaoyong. "Cryogenic characteristics of IGBTs." Thesis, University of Birmingham, 2005. http://etheses.bham.ac.uk//id/eprint/896/.
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Applications are now starting to emerge for superconducting devices in the areas of electrical power conversion and management, for example superconducting windings for marine propulsion motors, superconducting fault current limiters and superconducting magnet energy storage (SMES). Many of these applications also require power electronics, and it is therefore timely to consider the possibility of locating the power electronics in the cryosystem with the superconducting devices. Although significant work has been undertaken on the cryogenic operation of small devices, little has been published on larger devices, particularly the IGBT. This therefore forms the focus of this study. To examine the cryogenic performance of the sample devices, a cryo-system consisting of a cold chamber, a helium-filled compressor and vacuum pumps was built. Static, gate charge and switching tests were carried out on three types of IGBT modules, PT (punch-through), NPT (non-punch-through) and IGBT3 respectively, in the temperature range of 50 to 300 K. The switching tests were undertaken at 600V and up to 110 A. A physically based, compact level-1 model was selected to model the cryogenic performance of the IGBTs. A generic Saber power diode model with reverse recovery was selected to model the diode cryogenic performance. Close correspondence was demonstrated between the models and experimental results over the temperature range of 50- 300 K. Saber simulation was used to examine the cryogenic performance of a DC-DC step-down converter and a pulse-width modulated inverter leg, in which the temperature-dependent power device models developed in the modelling work were used. The simulation results showed that standard power electronic circuits using standard devices could work much more efficiently at low temperatures, for example, the efficiency of the DC-DC converter working at 50 kHz being increased from 90.0% at room temperature to 97.0% at 50 K.
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Nellis, Gregory F. (Gregory Francis). "Magnetically augmented cryogenic refrigeration." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11482.
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Magalhães, Rui. "Cryogenic gas-assisted injection moulding." Thesis, University of Warwick, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251053.
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Shokrani, Chaharsooghi Alborz. "Cryogenic machining of titanium alloy." Thesis, University of Bath, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636532.
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Materials which are both lighter and stronger have faced an increased demand over the past decades to fulfil the requirements across a range of industrial applications. More specifically, demands for titanium alloys have increased significantly due to its high strength to weight ratio which is particularly attractive for increasing fuel efficiency in aircrafts and cars and is also used in biomedical implants. Despite the increasing demand for titanium made products, machining titanium alloys remains a significant challenge. High material strength and hardness lead to excessive heat generation at the cutting zone which accumulates and results in high cutting temperatures due to the poor thermal conductivity. The high cutting temperatures together with inherent material properties of titanium are responsible for short tool life and poor surface finish. Despite the environmental and health drawbacks, a generous amount of cutting fluids is commonly used to control the cutting temperature in machining titanium alloys. However, conventional cutting fluids evaporate at high cutting temperatures which isolate the cutting zone by forming a vapour cushion resulting in further increases in cutting temperatures. This research investigates the effects of cryogenic cooling on machinability of Ti-6Al-4V alloy in CNC milling as compared to conventional dry and wet machining environments. Two literature reviews were conducted and a methodology has been developed and implemented consisting of three experimental stages of i) design and manufacture of a cryogenic cooling system, ii) comparative study of cryogenic cooling with dry and wet machining and iii) optimisation of cutting parameters for cryogenic machining. The major contribution of this research can be summarised as design, realisation and assessment of a novel cryogenic cooling system for CNC milling, termed cryogenic shower, which is retrofitable to an existing CNC machining centre. In addition, the research provides a thorough study on the effects of cryogenic cooling on machinability of Ti-6Al-4V alloy in comparison with dry and wet machining. The studies range from power consumption and tool wear through to surface topography and surface integrity. Furthermore, the optimum cutting parameters for cryogenic machining are identified. The research demonstrates that using the cryogenic shower has significantly improved machinability of Ti-6Al-4V through realisation of higher material removal rates, reduced tool wear and improved surface finish, surface topography and surface integrity.
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Brown, Keith Andrew. "Cryogenic characterization of Josephson junctions." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36132.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2006.Includes bibliographical references (p. 109-110).
Cryogenic characterization is a crucial part of understanding the behavior of low-temperature quantum electronics. Reliable device testing provides the feedback to fabrication process development, facilitating the rapid development of quantum devices. The research presented in this thesis explores the cryogenic testing, analysis, and characterization of a superconducting quantum device, the Josephson junction. This thesis begins with a theoretical description of superconductivity and Josephson junctions, two superconductors separated by a thin insulating battier. Two models of Josephson barriers are presented for use in analysis. The effect of self-induced magnetic field is considered. A numerical simulation is performed to justify neglecting effects of self-induced magnetic field in junctions of diameter less than the Josephson penetration depth Aj. Lincoln Laboratory's Josephson junction fabrication effort is described along with the apparatus used to test junctions at 4.2 K. Custom software used to test these junctions is then presented. The analysis of 4.2 K data is shown with a simple model of a disc as the insulating barrier. 391 valid Josephson junctions are analyzed across 16 wafers in 3 runs.
(cont.) The critical current density J is calculated to be 4.88 ± 2.81 ( ... ) for junctions with expected J of 5 ( ... ). The superconductive energy gap A is calculated to be 1.51 ± 0.31 meV. The process bias 60 is shown to be -0.35 i 0.12 ,tm. Analyzing the junctions with an alternate model taking into account pollution produces an upper bound for barrier pollution depth of approximately 60 nm. Discussion of a 300 mK apparatus is then presented. This apparatus is constructed and presently being incorporated in an existing 300 mK 3He refrigerator. Finally, the results are concluded with a discussion of advantages, and proposed initial experiments for the 300 mK apparatus.
by Keith Andrew Brown.
S.B.
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Conway, Lamb Ian. "Cryogenic Control Beyond 100 Qubits." Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/17046.
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Quantum computation has been a major focus of research in the past two decades, with recent experiments demonstrating basic algorithms on small numbers of qubits. A large-scale universal quantum computer would have a profound impact on science and technology, providing a solution to several problems intractable for classical computers. To realise such a machine, today's small experiments must be scaled up, and a system must be built which provides control and measurement of many hundreds of qubits. A device of this scale is challenging: qubits are highly sensitive to their environment, and sophisticated isolation techniques are required to preserve the qubits' fragile states. Solid-state qubits require deep-cryogenic cooling to suppress thermal excitations. Yet current state-of-the-art experiments use room-temperature electronics which are electrically connected to the qubits. This thesis investigates various scalable technologies and techniques which can be used to control quantum systems. With the requirements for semiconductor spin-qubits in mind, several custom electronic systems, to provide quantum control from deep cryogenic temperatures, are designed and measured. A system architecture is proposed for quantum control, providing a scalable approach to executing quantum algorithms on a large number of qubits. Control of a gallium arsenide qubit is demonstrated using a cryogenically operated FPGA driving custom gallium arsenide switches. The cryogenic performance of a commercial FPGA is measured, as the main logic processor in a cryogenic quantum control system, and digital-to-analog converters are analysed during cryogenic operation. Recent work towards a 100-qubit cryogenic control system is shown, including the design of interconnect solutions and multiplexing circuitry. With qubit fidelity over the fault-tolerant threshold for certain error correcting codes, accompanying control platforms will play a key role in the development of a scalable quantum machine.
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Gom, Bradley Gustav. "A cryogenic detector for submillimetre astronomy." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0026/MQ49144.pdf.
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Gom, Bradley Gustav, and University of Lethbridge Faculty of Arts and Science. "A cryogenic detector for submillimetre astronomy." Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 1999, 1999. http://hdl.handle.net/10133/102.
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Over the last several years, a submillimetre astronomical polarizing Fourier Transform Spectrometer (FTS) has been developed for use at the James Clerk Maxwell Telescope (JCMT) located atop Mauna Kea, Hawaii. A new liquid3 He cooled dual polarization detector system has been carefully designed for use with this FTS to eliminate noise problems encountered with UKT14, the JCMT facility bolometric detector. The objective of this thesis is to evaluate and optimize the performance of the new detector system. The design of the detector system is discussed, and the noise performance of the system is evaluated. The system performance is determined from photmetric, classical B-I, and spectroscopic measurements. Compared to UKT14, the intrinsic bolometer noise is reduced by a factor of - 2. More importantly, the spectral signal to noise ratio is improved by a factor of - 10 due to the elimination of electrical pickup and microphone noise in the detector signal.xiv, 156 leaves : ill. ; 28 cm.
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Velat, Christopher James. "Experiments in cryogenic two phase flow." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0006941.
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Surovtseva, Daria. "CO2 separation by cryogenic and hydrate." Thesis, Curtin University, 2010. http://hdl.handle.net/20.500.11937/2501.
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According to the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4), fossil fuels are utilised to produce more than 80% of the world's energy and this is likely to remain unchanged in the nearest future, especially as industrialisation is pursued by such economic giants as China. Without substantial change in energy policies with primary focus on the development of sustainable technologies for power generation, mitigation of associated Green House Gas (GHG) emissions cannot be fully implemented, and will require continual improvement in order to achieve objectives set by the Kyoto protocol. Research and development in the field of Carbon Capture and Sequestration is therefore being thoroughly explored. In this work a new sustainable technology for CO2 capture from IGCC power stations is developed and discussed in detail. This technology is based on cryogenic condensation integrated with gas hydrate formation.With the massive global reduction in recoverable oil and the potential size in a few decades time, the accent started to shift towards the other available fossil fuels such as gas and coal. The amount of Natural Gas trapped in the form of solid hydrate sunk in the deep ocean and permafrost areas cannot be estimated precisely, however, the scientific community agrees that values in order of 1015 to 1017 cubic metres are realistic. This has caused overwhelming research into gas hydrates as storage media for different gases. Gas hydrates are highly organized crystalline structures with molecules of light gases encaged in a framework created by water molecules. They can form at any place where free water in intimate contact with hydrate forming gas is exposed to elevated pressures and low temperatures. The ability to store large quantity of gas per unit volume makes gas hydrates an attractive option for any application requiring gas preservation. One of such modern applications for gas hydrates has arisen from the global warming problem and addresses the potential capability to efficiently capture and safely store the CO2.Coal remains the main energy source in the world; for example, in Australia it is providing 40% of total energy and up to 80% of electricity (Cuevas-Cubria et al., 2010). The main advantages of coal over the other fossil energy resources are its abundance, its easy recoverability and lower cost. Massive pollution produced during burning of this fuel forced the creation of new technologies that allow for GHG reduction. Integrated Gasification Combined Cycle (IGCC) is the most favoured advanced option for energy recovery from a variety of sources, particularly coal, the so-called 'clean coal technology'. IGCC generates a high pressure shifted syngas stream composed essentially of Hydrogen and Carbon Dioxide. Historically, the CO2 was separated from rich sources (such as natural gas) via the Ryan-Holmes cryogenic condensation process. However, applied at the gas or oil refinery this method can consume up to 50% of the generated energy to bring the CO2 levels down to pipeline requirements which does not seem attractive in terms of cost of CO2 avoided. High temperatures utilised for coal gasification are also not favourable for the implementation of cryogenic condensation to an IGCC stream.On the other hand, high pressure and high CO2 content in the IGCC flue gas provide the ideal conditions for CO2 capture in the form of solid hydrates. This option has been investigated under the guidance of the US Department of Energy by a team of researchers (Los Alamos National Laboratory, Nexant, Inc., and SIMTECHE) since 1999 and at the Chinese Academy of Science. A few proof-of-concept reports can be found stating that the utilisation of the hydrate formation phenomenon for purification of gas streams is less energy intensive than any of the other existing CO2 capture methods. The ability to encapsulate significant amounts of gas in little space and relatively mild conditions of storage make the hydrates an extremely attractive option for easy handling of high rates of GHG emissions. However, this research is still on a laboratory scale.In this thesis a new method is developed for cost and energy efficient CO2 sequestration from IGCC sources based on a simple configuration. High feed pressure facilitates bulk removal of CO2 by cryogenic methods, and high energy recovery is achieved through process integration with hydrate formation. Liquid CO2 produced as a result of condensation carries most of the cold energy required for initial refrigeration, and the hydrate unit does not consume any substantial additional energy. Separated CO2 is characterised by high purity sufficient for utilisation in enhanced oil and gas recovery processes. The hydrate can be easily handled and stored. Although the focus is made on IGCC flue gas application, the method can be extended to other sources with high CO2 levels and supplied at high pressure.Additional value is brought to this research by extensive investigation of the phase behaviour of gas mixtures containing CO2. Particular attention is paid to the distinctive features of gas hydrates produced in different systems including mixtures with hydrocarbons and non-hydrocarbons in various concentrations and in the presence of chemicals dissolved in water. This knowledge will contribute to the future development in the field of hydrates and will be useful for both academic research and industrial application.
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Perea, Solano Blanca. "Cryogenic Silicon Microstrip detector modules for LHC." Doctoral thesis, Universitat Politècnica de Catalunya, 2004. http://hdl.handle.net/10803/6604.
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CERN is presently constructing the LHC, which will produce collisions of 7 TeV protons in 4 interaction points at a design luminosity of 1034 cm-2 s-1. The radiation dose resulting from the operation at high luminosity will cause a serious deterioration of the silicon tracker performance. The state-of-art silicon microstrip detectors can tolerate a fluence of about 3·1014 cm-2 of hadrons or charged leptons. This is insufficient for long-term operation in the central parts of the LHC trackers, in particular after the possible luminosity upgrade. By operating the detectors at cryogenic temperatures the radiation hardness can be improved by a factor 10. This work proposes a cryogenic microstrip detector module concept which has the features required for the upgraded LHC experiments at CERN. The module can hold an edgeless sensor, being a good candidate for improved luminosity and total cross-section measurements. The design of such a module is constrained by the requirements on radiation hardness and minimal mass. The choice of the component materials is guided by the properties of the silicon sensors, and the main criteria include best possible matching of the thermal dilatation, high thermal conductivity and appropriate elastic properties, in addition to the radiation resistance.
A module design is proposed where, apart from the silicon sensor, both the support plate and the pitch adapter are processed on silicon. Future design options may also feature hybrids processed in silicon using thick-film techniques and cooling microchannels directly micromachined into the support plate. The best performance and highest degree of integration of the cooling is achieved with two-phase flow (high heat transfer coefficient) argon running through capillary pipes embedded in a CFC spacer close to the heat sources. A series of thermal tests have shown that silicon is an excellent heat spreader and its use as a structural material leads to a uniform temperature distribution in the sensor and support plate. The thermal resistance due to the glue layers dominates the thermal behaviour.
The thermoelastic properties of the epoxies are key factors in the design. A series of samples were prepared to measure these properties of Araldite® 2011, Stycast® 1266 and Type L epoxies filled with fused quartz powder, as a function of temperature. Filling these epoxies reduces their thermal dilatation, nearly matching that of metals. This reduces the stress in the joints when cooling down. However, filling increases the Young modulus (E) of the epoxy so much, that the thermal stress increases with the filling factor. Furthermore, filling increases the viscosity and leads to thicker glue layers, which also increases the thermal stress in silicon. The idea of using filled epoxy was therefore abandoned. The E of unfilled epoxies at 77 K is between 4 and 8 times higher than that measured at 300 K. Thin layers of epoxy should be used to minimize the stress on the silicon substrate.
Precision gluing jigs were designed and produced to assemble the prototype modules. The alignment with respect to the beam is done using a warm support plate, placed between the module and the vacuum chamber. The module is attached to this support structure through three thermally isolating precision support posts with dowels. The position of the module and its readout strips is thus accurately referred to the vacuum chamber, which itself can be aligned in the test beam line using optical targets.
A first electrical prototype module was assembled using a 50 ?m pitch silicon microstrip sensor (32.5 cm2). Pitch adapter and support plate were processed on silicon. The CMS hybrid with APV25 readout chips was characterized at low temperature. First results were obtained down to 210 K, showing a decrease of the noise and the rise time and an increase of the pulse peak height with respect to the room temperature behaviour.
A pair of edgeless silicon diode pad sensors was exposed to the X5 high-energy pion beam, in order to determine the edge sensitivity. A high-resistivity silicon p+-i-n+ planar diode detector (0.25 cm2) was diced through its front p+ implant to produce two halves of edgeless diode pad sensors. A large surface current on such an edge prevents the normal reverse biasing of this device but it can be sufficiently reduced by the use of a suitable cutting method, followed by edge treatment and by operating the sensor at low temperature. The gap width between the edgeless sensors, determined using the tracks measured by a reference telescope, was compared with metrology measurements. It was concluded that the depth of the dead layer is compatible with zero within the statistical accuracy of 8 µm and systematic accuracy of 6 µm.
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Cozzini, Cristina. "CRESST dark matter search with cryogenic calorimeters." Diss., [S.l.] : [s.n.], 2003. http://edoc.ub.uni-muenchen.de/archive/00001299.
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Yuan, Jiahui. "SiGe HBTs Operating at Deep Cryogenic temperatures." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14609.
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As Si-manufacturing compatible SiGe HBTs are making rapid in-roads into RF through mm-wave circuit applications, with performance levels steadily marching upward, the use of these devices under extreme environment conditions are being studied extensively. In this work, test structures of SiGe HBTs were designed and put into extremely low temperatures, and a new negative differential resistance effect and a novel collector current kink effect are investigated in the cryogenically-operated SiGe HBTs.
Theory based on an enhanced positive feedback mechanism associated with heterojunction barrier effect at deep cryogenic temperatures is proposed. The accumulated charge induced by the barrier effect acts at low temperatures to enhance the total collector current, indirectly producing both phenomena. This theory is confirmed using calibrated 2-D DESSIS simulations over temperature. These unique cryogenic effects also have significant impact on the ac performance of SiGe HBTs operating at high-injection. Technology evolution plays an important role in determining the magnitude of the observed phenomena, and the scaling implications are addressed. Circuit implication is discussed.
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Sivapurapu, Sai Vinay Kumar Plummer Mitty Charles. "Preliminary design of a cryogenic thermoelectric generator." [Denton, Tex.] : University of North Texas, 2007. http://digital.library.unt.edu/permalink/meta-dc-3612.
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Andrew, Jeremy James. "Energy transfer in gases and cryogenic liquids." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303566.
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Wilson, Graham John. "Energy transfer in gases and cryogenic liquids." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239254.
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Brunner, Andreas [Verfasser]. "Cryogenic NV Scanning Probe Magnetometry / Andreas Brunner." München : Verlag Dr. Hut, 2018. http://d-nb.info/1174426357/34.
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Dhokia, Vimal Gordhan. "The Cryogenic Sculptured Surface Machining of Elastomers." Thesis, University of Bath, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.507757.
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Emery, Nick. "Cryogenic refrigeration using an acoustic stirling expander." Thesis, University of Canterbury. Mechanical Engineering, 2011. http://hdl.handle.net/10092/5306.
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A single-stage pulse tube cryocooler was designed and fabricated to provide cooling at 50 K for a high temperature superconducting (HTS) magnet, with a nominal electrical input frequency of 50 Hz and a maximum mean helium working gas pressure of 2.5 MPa. Sage software was used for the thermodynamic design of the pulse tube, with an initially predicted 30 W of cooling power at 50 K, and an input indicated power of 1800 W. Sage was found to be a useful tool for the design, and although not perfect, some correlation was established. The fabricated pulse tube was closely coupled to a metallic diaphragm pressure wave generator (PWG) with a 60 ml swept volume. The pulse tube achieved a lowest no-load temperature of 55 K and provided 46 W of cooling power at 77 K with a p-V input power of 675 W, which corresponded to 19.5% of Carnot COP. Recommendations included achieving the specified displacement from the PWG under the higher gas pressures, design and development of a more practical co-axial pulse tube and a multi-stage configuration to achieve the power at lower temperatures required by HTS.
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Wu, M. F. "The solubility of solutes in cryogenic liquids." Thesis, University of Southampton, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373935.
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Dubrovsky, Vladimir. "Adaptive control of linear Stirling cryogenic coolers." Thesis, Loughborough University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432812.
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Thorne, Jacob Aaron. "Electric field optimisation for cryogenic nEDM experiments." Thesis, University of Sussex, 2018. http://sro.sussex.ac.uk/id/eprint/80282/.
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This thesis presents details of the design, construction and measurements of an apparatus (Blue Elbow cryostat) for high voltage testing of a full-size cryogenic nEDM cell in liquid helium at 4.2 K SVP. The test cell is cylindrical and of 24 cm internal diameter with stainless steel electrodes and an insulating borosilicate glass spacer. The cylinder axis of the cell is vertical and the insulator is located in grooves in the electrodes. The electrode separation can be varied from 0.2 cmto 2.6 cm and a voltage of up to 260 kV can be applied across the cell. It has long been expected that a nEDM cell immersed in superfluid LHe at 0.5 K should permit E-fields much greater than room temperature experiments. Long et al. (1) showed that over 400 kV/cm was obtainable in a large cell without an insulating spacer at 4.2 K, but that this was reduced dramatically as the temperature, and hence pressure, was reduced to below 2 K in a pumped LHe bath. Subsequent work by Davidson (2) in this laboratory on small spacerless cells showed that the dielectric strength in the superfluid at 1.9 K could be restored to its 400 kV/cm value by pressurising the LHe to 1 bar. Further work in this laboratory by Davidson (2) and Hill (3) shows that the introduction of a dielectric spacer reduces the value of the breakdown field, Ebd , for a given geometry. However, measurements presented here on smaller scales than the Blue Elbow cryostat, overcame the reduced fields through careful groove optimisation and insulator material choice. Ebd data as a function of separation with the Blue Elbow cryostat in LN2 show a clear reduction compared to data from smaller scale cells, due to surface area effects. Breakdown fields in LHe at 4.2 K SVP with this apparatus indicate fields at 120 kV/cm were achievable at 6mm separation but dropped off dramatically as separation was increased to 12 mm then 16 mm. The reason for the drop off is attributed to the geometry of the electrode. This result, together with Davidson's pressure dependence data, should inform the design of a future cryogenic nEDM experiment.
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Becher, Marina. "Cryogenic soil processes in a changing climate." Doctoral thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-112509.
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A considerable part of the global pool of terrestrial carbon is stored in high latitude soils. In these soils, repeated cycles of freezing and thawing creates soil motion (cryoturbation) that in combination with other cryogenic disturbance processes may play a profound role in controlling the carbon balance of the arctic soil. Conditions for cryogenic soil processes are predicted to dramatically change in response to the ongoing climate warming, but little is known how these changes may affect the ability of arctic soils to accumulate carbon. In this thesis, I utilize a patterned ground system, referred to as non-sorted circles, as experimental units and quantify how cryogenic soil processes affect plant communities and carbon fluxes in arctic soils. I show that the cryoturbation has been an important mechanism for transporting carbon downwards in the studied soil over the last millennia. Interestingly, burial of organic material by cryoturbation appears to have mainly occurred during bioclimatic events occurring around A.D. 900-1250 and A.D. 1650-1950 as indicated by inferred 14C ages. Using a novel photogrammetric approach, I estimate that about 0.2-0.8 % of the carbon pool is annually subjected to a net downward transport induced by the physical motion of soil. Even though this flux seems small, it suggests that cryoturbation is an important transporter of carbon over centennial and millennial timescales and contributes to translocate organic matter to deeper soil layers where respiration proceeds at slow rates. Cryogenic processes not only affect the trajectories of the soil carbon, but also generate plant community changes in both species composition and abundance, as indicated by a conducted plant survey on non-sorted circles subjected to variable differential frost heave during the winter. Here, disturbance-tolerant plant species, such as Carex capillaris and Tofieldia pusilla, seem to be favoured by disturbance generated by the differential heave. Comparison with findings from a previous plant survey on the site conducted in the 1980s suggest that the warmer temperatures during the last decades have resulted in decreased differential heave in the studied non-sorted circles. I argue that this change in cryogenic activity has increased abundance of plants present in the 1980s. The fact that the activity and function of the non-sorted circles in Abisko are undergoing changes is further supported by their contemporary carbon dioxide (CO2) fluxes. Here, my measurements of CO2 fluxes suggest that all studied non-sorted circles act as net CO2 sources and thus that the carbon balance of the soils are in a transition state. My results highlight the complex but important relationship between cryogenic soil processes and the carbon balance of arctic soils.
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Burns, Rebecca Kate. "Cryogenic carbon cycling at an Icelandic glacier." Thesis, Lancaster University, 2016. http://eprints.lancs.ac.uk/85961/.
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Glaciers and ice caps are recognised as an important component of the global carbon cycle. Carbon within glacial systems exists in organic and inorganic forms, across supraglacial, englacial and subglacial realms. It is often difficult to detach cryospheric carbon cycling from hydrology, with the transfer of carbon between glacial inventories relying upon meltwater flows. Classical glacial hydrology consists of distributed drainage delivering delayed flow meltwaters, throughout the accumulation season, superseded by quick flow, aerated channelized drainage during increased ablation. It is upon this template that most existing studies have addressed the dynamics of carbon within glaciated catchments. However, Icelandic glacial systems provide an opportunity to investigate the role of subglacial volcanism in driving carbon dynamics. Hydrochemical properties of Sόlheimajökull bulk meltwaters indicate untraditional redox conditions, with discharge of reduced, anoxic meltwaters in Summer, when expansion of subglacial drainage intersects the Katla geothermal zone. This unique hydrological regime generates profound effects upon the solute flux from the glacier, particularly with regard to the carbon budget. Dissolved inorganic carbon dynamics are dominated by weathering of basaltic bedrocks and accessory hydrothermal calcites, fuelled by subglacial geothermal proton supply. Widespread basal anoxia during summer facilitates methanogenesis resulting in large quantities of methane being discharged from beneath the glacier (flux range between 9,179 to 22,551 tonnes per year). Evidence suggests subglacial microbial acetoclastic methanogenesis is responsible with δ13C and δD CH4 values of ~60‰ and -320‰ respectively, supported by laboratory identification of methanogenesis in Sόlheimajökull subglacial sediments. The organic counterpart to the carbon cycle is invoked to serve as the energy source for microbial metabolism. Such direct measurements of subglacial methane have rarely been achieved at contemporary ice margins. This study therefore provides an exciting opportunity to identify methane sources and carbon cycling in areas subjected to subglacial volcanism and to consider these within the broader context of global carbon dynamics.
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De, Cea Falco Marc. "Millivolt silicon photonic modulators for cryogenic applications." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/130202.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, May, 2020Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 275-298).
Cryogenic technologies promise to overcome existing bottlenecks in a range of science and engineering fields including quantum computing, high performance computing and single-photon communication systems. As these technologies mature and systems scale, a readout solution for high speed, low power data transfer between the cryogenic environment and room temperature becomes essential. The use of optical links for such data transfer - in what is known as cryogenic optical readout - is appealing due to the low heat conduction of optical fiber and the possibility to exploit wavelength division multiplexing architectures. However, existing demonstrations suffer from large power dissipation associated with amplifying the millivolt signals generated by the cryogenic systems. This thesis deals with the development of silicon photonic modulators operating at cryogenic temperatures and capable of modulating an optical carrier with millivol-level driving signals. We show cryogenic operation of CMOS photonic resonant modulators in the forward bias regime with high modulation efficiency and reduced power dissipation, and demonstrate cryogenic optical readout of a superconducting single photon detector. We also present a new operation mode for optical modulators that leverages parasitic photocurrent to achieve electrical gain and reduce power dissipation. Modulation with signal levels down to 4 mVpp and electrical power dissipation in the zJ/bit range is demonstrated. This thesis sets the foundation for silicon photonics to realize scalable, low power, high throughput cryogenic readout, addressing one of the key remaining challenges for the wide adoption of cryogenic technologies.
by Marc de Cea Falco.
S.M.
S.M. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
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Barsi, Stephen. "Ventless Pressure Control of Cryogenic Storage Tanks." Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1283125342.
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Sivapurapu, Sai Vinay Kumar. "Preliminary design of a cryogenic thermoelectric generator." Thesis, University of North Texas, 2007. https://digital.library.unt.edu/ark:/67531/metadc3612/.
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A cryogenic thermoelectric generator is proposed to increase the efficiency of a vehicle propulsion system that uses liquid nitrogen as its fuel. The proposed design captures some of the heat required for vaporizing or initial heating of the liquid nitrogen to produce electricity. The thermoelectric generator uses pressurized liquid nitrogen as its cold reservoir and ambient air as the high-temperature reservoir to generate power. This study concentrated on the selection of thermoelectric materials whose properties would result in the highest efficiency over the operating temperature range and on estimating the initial size of the generator. The preliminary selection of materials is based upon their figure of merit at the operating temperatures. The results of this preliminary design investigation of the cryogenic thermoelectric generator indicate that sufficient additional energy can be used to increase overall efficiency of the thermodynamic cycle of a vehicle propulsion system.
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White, Thomas Leslie Carleton University Dissertation Geology. "Cryogenic alteration of a frost susceptible soil." Ottawa, 1992.
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Jensen, Mark. "Energy Process Enabled by Cryogenic Carbon Capture." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5711.
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Global climate change concerns help shape current environmental regulations, which increasingly seek to reduce or capture CO2 emissions. Methods for capturing CO2 emissions from energy processes have been the focus of numerous studies to provide support for those seeking to reduce the environmental impact of their processes. This research has (1) simulated a baseline case of energy-storing cryogenic carbon capture for implementation on a 550 MWe coal fired power plant, (2) presented a novel cryogenic carbon capture process for removing CO2 from natural gas down to arbitrary levels, (3) presented a natural gas liquefaction process that has the ability to be highly CO2 tolerant, and (4) developed theoretical models and their experimental validation of CO2 capture predictions for all aforementioned processes.
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Cha, Jeesung Jeff. "CFD Simulation of Multi-Dimensional Effects in Inertance Tube Pulse Tube Cryocoolers." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5229.
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Inertance Tube Pulse Tube Cryocoolers (ITPTC) are a class of rugged and high-endurance refrigeration systems that operate without a moving part at their low temperature end, and are capable of reaching 4 K or lower. ITPTCs are suitable for application in space vehicles, and attempts are underway worldwide to improve their performance and miniaturize their size. The thermo-fluidic processes in ITPTC are complicated, however, and the details of the mechanisms underlying their performance are not well understood. Elucidation of these underlying processes is the objective of this investigation.
In this study, the commercial computational fluid dynamic (CFD) package Fluent䵠was utilized for modeling the entire large ITPTC system that includes a compressor, an after cooler, a regenerator that is represented as a porous medium, a pulse tube, cold and warm heat exchangers, an inertance tube, and a reservoir. The simulations represent a fully-coupled system operating in steady periodic mode, without any arbitrary assumptions. The objective was to examine the extent of multi-dimensional flow effects in an inertance tube pulse tube cryocoolers, and their impact on the performance of these cryocoolers.
Computer simulations were performed for two complete ITPTC systems that were geometrically similar except for the length-to-diameter ratios of their regenerators and pulse tubes. For each ITPTC system three separate simulations were performed, one with an adiabatic cold-end heat exchanger (CHX), one with a known cooling heat load, and one with a pre-specified CHX temperature. Each simulation would start with an assumed uniform system temperature, and continue until steady periodic conditions were achieved.
The results indicate that CFD simulations are capable of elucidating the complex periodic processes in PTCs very well. The simulation results also show that a one-dimensional modeling of PTCs is appropriate only when all the components of the PTC have very large aspect ratios (i.e., L/D >>1). Significant multi-dimensional flow effects occur at the vicinity of component-to-component junctions, and secondary-flow recirculation patterns develop, when one or more components of the PTC system have small aspect ratios. The simulation results, although limited in scope, also suggest that ITPTCs will have a better overall performance if they are made of components with large aspect ratios.
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Mancuso, Michele. "Development and optimization of scintillating bolometers and innovative light detectors for a pilot underground experiment on neutrinoless double beta decay." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS083/document.
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Le travail de doctorat exposé dans ce manuscrit a été développé dans le cadre du projet LUMINEU, une expérience pilote pour la double désintégration bêta sans émission de neutrinos (0νββ) de l'isotope Mo avec des bolomètres scintillants de ZnMoO₄. Ce travail de physique expérimentale implique l'avancement du design et des tests des prototypes de détecteurs, et le développement des outils en vue de la préparation d'une expérience importante. La méthode de détection adoptée dans cette thèse est la technique bolométrique, qui s'intègre bien avec les caractéristiques requises des détecteurs pour étudier les événements rares. Le détecteur fournit une grande efficacité, une très bonne résolution en énergie et il permet la discrimination des particules pour la suppression du fond. Cette thèse se concentre sur la physique du neutrino et sur la désintégration 0νββ; les méthodes de détection expérimentales et la sensibilité de la demi-vie d'une expérience 0νββ sont traitées.La deuxième partie de ce travail est dédiée au setup, l'acquisition et l'analyse des données sont traitées en détails.La dernière partie de la thèse est consacrée aux résultats : les progrès réalisés dans le détecteurs bolométriques et les mesures sont résumés. Sur la base de ces résultats, nous avons calculé une sensibilité finale sur une expérience à venir basée sur ces détecteursThe current experiments on rare events searches for neutrino and dark matter are at present two of the most relevant and exiting field in particle and astro-particle physics.Thanks to the efforts made in the past years, much of progress has been made in answering some big open questions in this field. In particular, experiments in neutrino physics during the past decades gave very interesting results, stimulating new ideas of the mechanisms beyond the Standard Model. One of them is known as neutrinoless double beta decay which can give important informations on the puzzling picture of how nature behaves. It is a rare nuclear transition with a half life longer than 10^25 years where two neutrons decay simultaneously in to two protons with the emission of only two electrons, the two neutrino acting as a virtual particle between the two decay vertices. This process is possible only if the neutrino is equal to its antiparticle, which is in contrast with the SM predictions.The observation of this phenomenon can determining the nature -- Dirac or Majorana --, of massive neutrinos. This is of fundamental importance for making progress in our understanding of the origin of neutrino masses and mixing and of the symmetries governing the lepton sector of particle interactions. The measurement of the half life of the process would give unvaluable information on the absolute scale of neutrino masses, the Majorana phases and the type ofneutrino mass spectrum.This thesis is deeply related to the LUMINEU project aiming to prepare the construction of a next-generation Neutrinoless Double Beta Decay experiment, capable exploring the inverted hierarchy region of neutrino mass. This goal will be achieved through the development of sophisticated low-temperature detectors named bolometers, which may lead to important advancements in the field of dark matter detection as well.Bolometers are low temperature calorimetric detectors, which can exploit the so called homogeneous approach, which provides very high efficiency. They can be made by almost any dielectric material, giving a flexibility in the source/detector material choice. In addition, their excellent energy resolution makes them very competitive detectors.Scintillating bolometers are upgrade of the simple bolometers, where the absorber can also scintillate. The readout of the scintillating light is made by an auxiliary bolometer and it enables particle identification with the only drawback of doubling the readout channels.In this context, we developed, tested and optimized scintillating bolometers and innovative light detectors for a pilot underground experiment on neutrinoless double beta decay of 100Mo embedded in ZnMoO₄ and Li₂MoO₄ crystal scintillators.We demonstrated that the sensitivity of an experiment searching for neutrinoless double beta decay with scintillating bolometers can compete with reach the present forefront technologies in the field
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Li, Changyi. "Cryogenic atomic force microscope for characterization of nanostructures." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/2727.
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Thesis (M.S.) -- University of Maryland, College Park, 2005.Thesis research directed by: Electrical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Utturkar, Yogen. "Computational modeling of thermodynamic effects in cryogenic cavitation." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0011583.
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Petricca, Federica. "Dark Matter Search with Cryogenic Phonon-Light Detectors." Diss., lmu, 2005. http://nbn-resolving.de/urn:nbn:de:bvb:19-37308.
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Pacio, Julio César. "Multiscale thermo-hydraulic modeling of cryogenic heat exchangers." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16090.
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The cryogenic industry has experienced a continuous growth in the last decades, partially sustained by the worldwide development of Liquefaction of Natural Gas (LNG) projects. LNG technology provides an economically feasible way of transporting natural gas over long distances, and currently accounts for nearly 30% of the international trade of this resource. The economic feasibility of these projects, in terms of both capital and operating costs, is to a large extent controlled by the performance of the main cryogenic two-phase flow heat exchanger. This industrial scenario provides then the motivation for a detailed study of the heat exchanger from a design perspective. On the one hand, it is widely accepted that a highly detailed analysis is required at a micro scale to properly take account of the two phase heat transfer process. On the other hand, a process-level description corresponds to larger time and space scales. In general, determining the proper methodology for considering these scales and their interaction remains a challenging problem. For this reason, current techniques focus in only one particular scale. The main objective of this project is then to develop a multiscale model applicable for two-phase flow heat exchangers. In this context, a three-scale framework is postulated. This thesis was divided into macro, meso (medium) and micro scale analysis. First, a macroscopic analysis provides a broad description in terms of overall heat transfer and pressure drop, using simple models without taking into account the details of physical phenomena at lower scales. Second, at mesoscale level, flow in parallel channels is considered following a homogenization approach, thus including the effects of flow maldistribution and partial mixing. Third, the microscopic description conceives a phenomenological representation of boiling flows, following multifluid formulations, for two specific flow patterns: annular-mist and post-dryout regimes. Finally, a multiscale design algorithm is proposed.
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Skarpeteig, Jon. "Cryogenic micro-photoluminescence of silicon solar cell materials." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elektronikk og telekommunikasjon, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-11106.
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A literature review of relevant luminescence spectra for silicon solar cell materials has been performed. Three multi crystalline silicon samples in particular has been the focus of attention, one electronic grade sample R6, and two solar grade samples ES1, and MH2, where MH2 has added chromium. A list of relevant luminescence spectra has been compiled, and can be found in the appendix.The samples was measured using low temperature micro photoluminescence. They where cooled down by liquid helium in a cryostat, and excited using a laser. Photoluminescence was captured by a camera mounted on a spectrometer. Noise components was measured and removed, but are subject to changes in between measurements, causing some unwanted artifacts to appear in the end result.Luminescence due to P and B doping atoms are identified in ES1, and MH2 as expected, and a weak boron bound exciton line is also present in the clean sample R6. R6 also show signs of having a carbon-carbon complex impurity forming at grain boundaries. Lines attributed to chromium boron pairs where not observed in MH2, presumably due to the lack of such pairs. ES1 exhibits a luminescence attributed to a higher quality material, than both MH2, and R6. Expected behavior is for R6 to have such traits, but this is not the case. The reason for ES1 to show this enhanced luminescence is not known. Lines attributed to dislocations are observed in all the samples, but consist of less intense peaks than expected.Local heating is a severe problem using micro photoluminescence. Bound excitons, impurity lines, and dislocation related lines, all loose intensity at higher temperatures. The intrinsic TO line also have a substantial broadening with respect to energies, suggesting that local temperatures are as much as 70K higher than the sample holder temperature, when exciting with 128 mW using a 2 µm spot diameter.
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Luanje, Appolinaire Tifang. "INTEGRATED OPTICAL FIBER RAMAN SENSOR FOR CRYOGENIC APPLICATION." MSSTATE, 2008. http://sun.library.msstate.edu/ETD-db/theses/available/etd-04042008-155057/.
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An integrated fiber optical Raman sensor was designed for real-time, non intrusive detection of liquid and gaseous mixtures at high pressure and high flow rates. The integrated sensor employs a high-power solid-state pumped Nd:YAG frequency doubled (532nm) laser (3W), a modified In Photonics Raman probe which has built-in Raman signal filter optics, and two high-resolution spectrometers and photomultiplier tubes (PMT) with selected bandpass filters to collect both N2 and O2 Raman signals. The detection unit was also integrated with Lab View software interfaced PMT modules for fast data acquisition.
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Bruckmayer, Manfred. "Imaging cryogenic detectors for astro and particle physics." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312189.
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De, Motte Darren C. E. "Cryogenic ion trapping for next generation quantum technologies." Thesis, University of Sussex, 2016. http://sro.sussex.ac.uk/id/eprint/66011/.
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Quantum technology has made great strides in the last two decades with trapped ions demonstrating all the necessary building blocks for a quantum computer. While these proof of principle experiments have been demonstrated, it still remains a challenging task to scale these experiments down to smaller systems. In this thesis I describe the development of technology towards scalable cryogenic ion trapping and quantum hybrid systems. I first discuss the fundamentals of ion trapping along with the demonstration of ion trapping on a novel surface electrode ion trap with a ring shaped architecture. I then present the development of a cryogenic vacuum system for ion trapping at ~4 K, which utilizes a closed cycle Gifford McMahon cryocooler with a helium gas buffered ultra-low vibration interface to mechanically decouple a ultra-high vacuum system. Ancillary technologies are also presented, including a novel in-vacuum superconducting rf resonator, low power dissipation ceramic based atomic source oven and an adaptable in-vacuum permanent magnet system for long-wavelength based quantum logic. The design and fabrication of microfabricated surface ion traps toward quantum hybrid technologies are then presented. A superconducting ion trap with an integrated high quality factor microwave cavity and vertical ion shuttling capabilities is described. The experimental demonstration of the cavity is also presented with quality factors of Q6~6000 and Q~15000 for superconducting niobium nitride and gold based cavities respectively, which are the highest demonstrated for microwave cavities integrated within ion trapping electrode architectures. An ion trap with a multipole electrode geometry is then presented, which is capable of trapping a large number of ions simultaneously. The homogeneity of five individual linear trapping regions are optimized and the design for the principle axis rotation of each linear region is presented. An overview of microfabrication techniques used for fabricating surface electrode ion traps is then presented. This includes the detailed microfabrication procedure for ion traps designed within this thesis. A scheme for the integration of ion trapping and superconducting qubit systems as a step towards the realization of a quantum hybrid system is then presented. This scheme addresses two key diffculties in realizing such a system; a combined microfabricated ion trap and superconducting qubit architecture, and the experimental infrastructure to facilitate both technologies. Solutions that can be immediately implemented using current technology are presented. Finally, as a step towards scalability and hybrid quantum systems, the interaction between a single ion and a microwaves field produced from an on chip microwave cavity is explored. The interaction is described for the high-Q microwave cavity designed in this thesis and a 171Yb+ion. A description of the observable transmission from the cavity is described and it is shown that the presence of a single ion can indeed be observed in the emission spectrum of high-Q microwave cavity even in the weak coupling regime.
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Major, Kyle D. "Coupling single molecules to cryogenic optical fibre microcavities." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/32272.
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Placing single emitters inside optical cavities provides a way of drastically modifying their interaction with the electric field. Such systems can be used to test our fundamental understanding of quantum electrodynamics and to develop devices that exploit this new found knowledge. This thesis describes work towards coupling single dye molecules to optical fibre microcavities at cryogenic temperatures. I present the design of an oven growth chamber and develop a method to grow cosublimated crystals of anthracene doped with dibenzoterrylene. I then describe the characterisation of these samples using a confocal microscope setup both at ambient and cryogenic temperatures. The samples grown show bright, stable, single emitters in a defined orientation in the anthracene crystals. By varying the growth parameters of the homebuilt crystal growing chamber, we can control the density of dibenzoterrylene molecules and grow at an optimum density to use these crystals in conjunction with optical fibre microcavities. I show how optical fibre microcavities have been developed that can be cooled to the liquid helium temperatures required to take advantage of the lifetime-limited emission from single dibenzoterrylene molecules, that only occurs below 4K. I also present cavity quantum electrodynamic simulations of the cavities, showing what we expect to see when we take reflection spectra of single molecules coupled to these cavities. In addition, I describe the optical setup that has been developed to take these measurements. I conclude with proposed improvements to the cavity setup that will enable these reflection spectra to be more easily taken. This will allow these molecule-cavity systems to be used as infrared single photon sources for quantum optics experiments.
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Obaida, Hayder Mahdi Baqer. "Cryogenic cycle power turbines optimised by hub contouring." Thesis, University of Leicester, 2017. http://hdl.handle.net/2381/40492.
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Improvements in stage isentropic efficiency and reductions in stage total pressure loss are sought in a 1.5 stage axial turbine. This is representative of power generation equipment used in thermal power cycles, in a cryogenic plants, and in aeroderivative engines. The performance of cryogenic installations and of power plants can be enhanced by using turbines with a higher isentropic efficiency, by reducing the secondary flow losses. Secondary flow loss reduction is achieved by designing a non-axisymmetric end-wall for the turbine inlet stator hub. The approach is to use a novel guide groove to direct the pressure side branch of the horseshoe vortex away from the blade suction side, using a novel parametric end-wall hub surface definition. This delays the onset of the passage vortex and reduces its associated loss. The performance of the novel hub profile is compared with that from contouring the hub using representative industry best practice. For this, a three-dimensional steady RANS model with an axisymmetric hub is first validated against reference experimental measurements from RWTH Aachen. A Kriging surrogate model from the Alstom Process and Optimisation Workbench (APOW) is used to optimise the hub surface. Comparative CFD predictions with an optimised non-axisymmetric hub show a decrease in the stage total pressure loss coefficient and an increase in the stage isentropic efficiency at design and off-design. The potential benefits to a representative Liquefied Natural Gas (LNG) cryogenic cycle is assessed by thermodynamic cycle analysis. A 1.60 % increase in the axial turbine stage isentropic efficiency is predicted by using a hub contoured by the optimised guide groove compared to a 0.19 % increase by using the industry best practice. The higher turbine stage isentropic efficiency is predicted to enhance the performance of the LNG cryogenic plant by a 3.15 % rise in the Coefficient Of Performance.
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Coulter, Philip. "Cryogenic phonon-scintillation detectors with NTD germanium readout." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:8ee65ffd-1f0f-4318-894f-c82746acaefb.
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Cryogenic detectors are an advanced technology for both dark matter and neutrinoless double beta decay searches, having the key advantage of a range of possible absorber materials that can be used for the detectors. Neutron transmutation doped germanium sensors are highly sensitive thermometers ideal for use at milli kelvin temperatures, with a simple repeatable resistance temperature relation. To discriminate between candidate events and background events simultaneous measurements can be made of the energy deposited in the detector as phonons and the energy emitted by the absorber crystal as scintillation light. Phonon detectors with a calcium tungstate or calcium molybdate crystal as the target and an NTD sensor as a thermometer were made in Oxford, along with a light detector with a light-absorbing silicon layer on a sapphire crystal, also with an NTD thermometer. A system of electronics was designed and tested in Oxford to bias and readout the NTD thermometers, while the setup inside the cryostat was developed to provide a thermally and mechanically stable shielded environment for the detectors. As part of this, prototype semi-rigid kapton cabling for use in the EDELWEISS experiment was installed and tested in the cryostat. Three different NTD germanium sensor types were characterized and calibrated in the cryostat and two of these selected for use on the phonon and light detectors. The detectors were operated at temperatures as low as 9 mK and tested with radioactive sources to produce energy spectra. Baseline resolutions of 1.7 keV and 2.5 keV, respectively, were achieved for the calcium molybdate and calcium tungstate phonon detectors. A working scintillation light detector was demonstrated as part of a phonon-scintillation detector module with a suggested application in double-beta decay searches.
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Schalk, Martin. "Ultra-fast electronic pulse control at cryogenic temperatures." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAY061.
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Synchronisation ultra-rapide, mise en forme d’impulsions et commutation efficace sont au cœur des mesures précises. L’objectif de ce projet de thèse est d’apporter le contrôle électronique ultra-rapide aux circuits nanométriques refroidis à des températures de l’ordre du mK. L’opération quantique rapide rapprochera le domaine de l’optique électronique quantique de son homologue photonique avec des applications pour un contrôle électronique rapide et efficace des dispositifs quantiques. Les dispositifs expérimentaux développés au cours de ce projet de thèse sont décrits et testés de manière à esquisser également les possibilités d’intégration dans les technologies quantiques. Dans un premier temps, une impulsion de tension de forme lorentzienne Γ = (76 ± 2) ps est mesurée de manière résolue dans le domaine temporel à des températures cryogéniques. Ensuite, les dérives de phase et d’amplitude sont analysées et optimisé avec le spectre de bruit. Un nouveau dispositif de génération d’impulsions utilisant un générateur de peigne est ensuite décrit et testé. Enfin, un futur réalisation d’une expérience d’interférence quantique par manipulation et détection dans un conducteur quantique est décrite, de même que les défis posés pour les dispositives quantiques à basse température et ses interconnexionsUltra-fast synchronization, pulse shaping, and efficient switching are at the heart of precise measurements. The aim of this thesis project is to bring ultra-fast electronic control to small nano-metric circuits cooled down to mK temperatures. The fast quantum operation will bring the field of quantum-electronic optics closer to its photoniccounterpart with applications for fast and efficient electronic control in quantum devices. To this end, the experimental setups developed during the thesis project are described and tested in a way to outline also possible device integration for scalable solid-state quantum technology. As a first step, a Lorentzian-shaped voltage pulse with a full width half maximum Γ = (76 ± 2) ps is measured in a time-resolved manner at cryogenic temperatures. Secondly, the phase and amplitude drifts are analyzed and optimized together with the noise spectrum. A new pulse generation setup using a microwave frequency comb generator is then described and tested. Finally, a future realization of a quantum interference experiment by manipulating and detecting electronic pulses in a quantum conductor is described along with challenges for low-temperature quantum hardware and interconnects
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Bamforth, P. B. "The structural permeability of concrete at cryogenic temperatures." Thesis, Aston University, 1987. http://publications.aston.ac.uk/14275/.
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The thesis describes a programme of research designed to identify concretes for application at cryogenic temperature, in particular for storage of Liquefield Natural Gas which is maintained at a temperature of -165oC. The programme was undertaken in two stages. Stage 1 involved screening tests on seventeen concrete mixes to investigate the effects of strength grade (and water/cement ratio), air entrainment, aggregate type and cement type. Four mixes were selected on the basis of low temperature strength, residual strength after thermal cycling and permeability at ambient temperature. In Stage 2 the selected mixes were subjected to a comprehensive range of tests to measure those properties which determine the leak tightness of a concrete tank at temperatures down to -165oC. These included gas permeability; tensile strength, strain capacity, thermal expansion coefficient and elastic modulus, which in combination provide a measure of resistance to cracking; and bond to reinforcement, which is one of the determining factors regarding crack size and spacing. The results demonstrated that the properties of concrete were generally enhanced at cryogenic temperature, with reduced permeability, reduced crack proneness and, by virtue of increased bond to reinforcement, better control of cracking should it occur. Of the concretes tested, a lightweight mix containing sintered PFA aggregate exhibited the best performance at ambient and cryogenic temperature, having appreciably lower permeability and higher crack resistance than normal weight concretes of the same strength grade. The lightweight mix was most sensitive to thermal cycling, but there was limited evidence that this behaviour would not be significant if the concrete was prestressed. Relationships between various properties have been identified, the most significant being the reduction in gas permeability with increasing strain capacity. The structural implications of the changing properties of the concrete have also been considered.
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Nielson, Bradley J. "Cryogenic Carbon Capture using a Desublimating Spray Tower." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3721.
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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.
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MARTINEZ, ROJAS ALEJANDRO DAVID. "Integrated cryogenic electronics to readout large areas SiPMs." Doctoral thesis, Politecnico di Torino, 2021. http://hdl.handle.net/11583/2907032.
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