At the request of the Governor of Michigan, researchers from the Institute for Social Research (ISR) at The University of Michigan conducted studies of the social effects of and community support for the proposed Superconducting Super Collider (SSC) project in Michigan. Their initial work in 1986 focused on Dundee, in southeastern Michigan, the first site considered by Michigan as a location for the SSC. The State eventually presented proposals for two Michigan sites: the Dundee location and a location near Stockbridge, which is situated in south central Michigan. Research was conducted at both sites.

This thesis presents the results of the experimental studies on two kindof Superconducting circuits: one-dimensional Josephson junction chains andsuperconducting coplanar waveguide (CPW) resonators. One-dimensionalJosephson junction chains are constructed by connecting many Superconducting quantum interference devices (SQUIDs) in series. We have studied DC transport properties of the SQUID chains and model their nonlineardynamics with Thermally Activated Phase-Slips (TAPS). Experimental andsimulated results showed qualitative agreement revealing the existence of auniform phase-slipping and phase-sticking process which results in a voltage-independent current on the dissipative branch of the current-voltage char-acteristics (IVC). By modulating the effective Josephson coupling energy ofthe SQUIDs (EJ ) with an external magnetic field, we found that the ratio EJ /EC is a decisive factor in determining the qualitative shape of theIVC. A quantum phase transition between incoherent Quantum Phase Slip, QPS (supercurrent branch with a finite slope) to coherent QPS (IVC withwell-developed Coulomb blockade) via an intermediate state (supercurrentbranch with a remnant of Coulomb blockade) is observed as the EJ /EC ratio is tuned. This transition from incoherent QPS to the intermediate-statehappens around R0 ∼ RQ (RQ = h/4e^2 = 6.45kΩ). We also fabricated structured chains where a SQUID at the middle of the chain (central SQUID) has different junction size and loop area compared to other SQUIDs in the chain. Results showed that with these structured chains it is possible to localize andtune the amplitude of both TAPS and QPS at the central SQUID. The second part of the thesis describes the fabrication process and themeasurement results of superconducting CPW resonators. Resonators withdifferent design parameters were fabricated and measured. The transmissionspectra showed quality factors up to, Q ∼ 5 × 10^5 . We have observed bendingof the resonance curves to the lower frequencies due to existence of a nonlinear kinetic inductance. The origin of the nonlinear kinetic inductance isthe nonlinear relation between supercurrent density, Js, and superfluid veloc-ity, vs , of the charge carriers on the center line of the resonators. A simplemodel based on the Ginzburg-Landau theory is used in order to explain ob-served nonlinear kinetic inductance and estimates using this model showedgood agreement with the experimental results. / <p>QC 20131030</p> / SCOPE

Current physical supports used in cryogenic storage vessels, in which liquid hydrogen is stored, conduct heat from the environment to the liquid hydrogen which causes the hydrogen temperature to rise and ultimately leads to hydrogen losses due to boil-off. The focus of this study is to investigate magnetic levitation as a possible suspension mechanism, eliminating the use of current physical supports and so doing reducing hydrogen losses due to boil-off. A conceptual design of a container which makes use of magnetic suspension is presented in this study. The concept is validated on the basis of the forces obtainable between a paramagnetic aluminium plate and an electromagnet, as well as the forces obtainable between a neodymium magnet and a bulk Yttrium-Barium-Copper-Oxide superconductor. The forces between the paramagnetic aluminium plate and electromagnet were determined mathematically and tested experimentally. The forces between the magnet and superconductor were determined mathematically and by finite element modelling and simulations using ANSYS Multiphysics. The results obtained in the mathematical- and finite element studies were then validated experimentally. It was found that the forces obtained experimentally between the aluminium plate and electromagnets are inadequate for magnetic suspension of the inner vessel given in the conceptual design. It was also found that the forces obtained experimentally and in the simulation studies for the magnet and superconductor of this study were inadequate due to shortcomings in the magnet and superconductor obtained for experimental tests. The conclusion of this study is that electromagnetic levitation should not be used as a magnetic suspension mechanism for storage of liquid hydrogen. It is also concluded that superconducting levitation can not be used as a suspension mechanism for the concept presented in this study, unless the methods suggested to increase the levitation forces between the neodymium magnet and superconductor are executed. / Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013

Current physical supports used in cryogenic storage vessels, in which liquid hydrogen is stored, conduct heat from the environment to the liquid hydrogen which causes the hydrogen temperature to rise and ultimately leads to hydrogen losses due to boil-off. The focus of this study is to investigate magnetic levitation as a possible suspension mechanism, eliminating the use of current physical supports and so doing reducing hydrogen losses due to boil-off. A conceptual design of a container which makes use of magnetic suspension is presented in this study. The concept is validated on the basis of the forces obtainable between a paramagnetic aluminium plate and an electromagnet, as well as the forces obtainable between a neodymium magnet and a bulk Yttrium-Barium-Copper-Oxide superconductor. The forces between the paramagnetic aluminium plate and electromagnet were determined mathematically and tested experimentally. The forces between the magnet and superconductor were determined mathematically and by finite element modelling and simulations using ANSYS Multiphysics. The results obtained in the mathematical- and finite element studies were then validated experimentally. It was found that the forces obtained experimentally between the aluminium plate and electromagnets are inadequate for magnetic suspension of the inner vessel given in the conceptual design. It was also found that the forces obtained experimentally and in the simulation studies for the magnet and superconductor of this study were inadequate due to shortcomings in the magnet and superconductor obtained for experimental tests. The conclusion of this study is that electromagnetic levitation should not be used as a magnetic suspension mechanism for storage of liquid hydrogen. It is also concluded that superconducting levitation can not be used as a suspension mechanism for the concept presented in this study, unless the methods suggested to increase the levitation forces between the neodymium magnet and superconductor are executed. / Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013

A theoretical model with experimental verification is presented to enhance the quantum efficiency of a superconducting single-photon detector without increasing the length or thickness of the active element. The basic enhancement framework is based on: (1) Utilizing the plasmonic nature of a superconducting layer to increase the surface absorption of the input optical signal. (2) Enhancing the critical current of the nanowires by reducing the current crowding at the bend areas through optimally rounded-bend implementation. The experimental system quantum efficiency and fluctuation rates per second are assessed and compared to the proposed theoretical model. The model originated from an accurate description of the different liberation mechanisms of the nano-patterned superconducting films (vortex hopping and vortex-antivortex pairing). It is built complimentary to the existing, well-established models by considering the effects of quantum confinement on the singularities' energy states. The proposed model explains the dynamics of singularities for a wide range of temperatures and widths and describe an accurate count rate behavior for the structure. Furthermore, it explains the abnormal behaviors of the measured fluctuation rates occurring in wide nano-patterned superconducting structures below the critical temperature. In accordance to this model, it has been shown that for a typical strip width, not only is the vortex-antivortex liberation higher than the predicted rate, but also quantum tunneling is significant in certain conditions, and cannot be neglected as it has been in previous models. Also it is concluded that to satisfy both optical guiding and photon detection considerations of the design, the width and the thickness of the superconducting wires should be carefully determined in order to maintain the device sensitivity while crossing over from the current crowding to vortex-based detection mechanisms.

Conventional computing based on classical technologies is approaching its limits. Therefore scientists are starting to consider the applications of quantum mechanics as a means for constructing more powerful computers. After proposing theoretical methods, many experimental setups have been designed to achieve quantum computing in reality. This thesis gives some background information on the subject of quantum computing. We first review the concept of quantum entanglement, which plays a key role in quantum computing, and then we discuss the physics of the SQUIDs-cavity method proposed by Yang et al., and give the definitions of quantum gates which are the elements that are needed to construct quantum circuits. Finally we give an overview of recent developments of SQUIDs-cavity systems and quantum circuits after Yang et al.'s proposal in 2003. These new developments help to take a step towards the constructions of higher levels of quantum technologies, e.g. quantum algorithms and quantum circuits.

This master thesis investigates if there is an induction motor configuration that can be used with a flywheel energy storage system, that uses passve superconducting magnetic bearings (SMBs). The configurations should be able to be designed with induction motor building blocks that are commercially available. The method used to investigate this was simulations of different induction motor configurations in the finite element analysis software COMSOL. The simulations show that when larger air-gaps than that of a commercial IM unit are used it is possible to use SMBs in the IM. SMBs have the advantage of having zero resistance which makes it possible to store energy without resistance losses. However it was found that by using and IM with SMBs the generated power would be lower than that of a commercial unit.

Josephson junctions are dissipationless elements used notably in superconducting nanocircuits. While being indispensable for the making of superconducting quantum bits, they are plagued by intrinsic noise mechanisms that reduce the coherence time of the quantum devices. An important source of such fluctuations may come from the non-cristallinity and disorder of the oxide layer sandwiched between the two superconducting leads. In this work, roughness in a Josephson junction is modeled as a set of pinholes with a universal bimodal distribution of transmission eigenvalues that sum incoherently in the noise power. Each of these channels is treated as a ballistic quantum point contact with a thin barrier that determines the transmission eigenvalue. The noise spectrum is calculated using the quasiclassical Green's function method to analyze high and low transmission limits at non-zero temperature for all interesting frequencies. As suggested by experiments, low transmission channels generate shot noise while fast switching between subgap states creates strong non-poissonian low-frequency noise. However, when analyzed for three different universal models of disorder, the principal contribution to noise is found to come from the partially opened channels. Finally, fluctuations of the noise from sample to sample is seen to be dominated by the contribution of opened channels which may reduce the reproducibility of results between different experiments.

Thesis (M.S.)--Michigan State University. Dept. of Physics and Astronomy, 2006. / Title from PDF t.p. (viewed on Nov. 20, 2008) Includes bibliographical references (p. 67-68). Also issued in print.

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 115-116).