Model Of High-temperature Superconductivity Research Articles

Fabrication and Test of a 1:4 Scaled HTS Coil for the Defocusing Magnet of 2 GeV FFAG Accelerator

The basic design of a 2 GeV fixed field alternating gradient (FFAG) accelerator was proposed by China Institute of Atomic Energy (CIAE) in 2019. A preliminary study of high temperature superconducting (HTS) magnet for the 2 GeV FFAG accelerator lattice scheme was carried out, considering the beam loss of high energy proton beams and energy efficiency of the main machine. In order to demonstrate the feasibility of manufacturing a spiral-shaped HTS magnet with concave edges based on ReBCO tapes, a 1:4 scaled HTS model magnet is being developed in CIAE. First, the design and fabrication of the 1:4 scaled prototype HTS magnet with concave edges will be described in detail. Then, each double pancake (DP) was tested by liquid nitrogen (LN) immersion. The terminal voltage and magnetic field variation were measured and simulated. Finally, the whole assembled HTS magnet was cooled down to 23 K using helium gas pipeline contact cooling and operated on 300 A for over 24 hours. The central magnetic field reached 719.5 mT, without iron. More detailed electromagnetic characteristics of the magnet during the excitation will be illustrated, which is much helpful for the fabrication of the final full-size HTS magnets.

Mathematical-Computational Optimization Methods on Primary Molecular Effect Model for Selected High Temperature Superconductors with Electronics Physics Applications

In previous series of contributions, Inverse Least Squares (ILS) Numerical Optimization, 3D/4D Interior Optimization, 3D/4D Graphical Optimization software and algorithms-programming were presented. The BCS theory Isotope Effect applications on superconductors TC dual/multiobjective optimization was the main subject. This contribution deals with the Molecular Effect Model for High Temperature Superconductors (HTSCs), in primary hypothesis stages. Selected group of HTSCs is Sn-Sb-Te-Ba-Mn-Cu-O . Namely, classical Inverse Least Squares, 2D Interior Optimization, and 2D Graphical Optimization techniques are applied. Results comprise Tikhonov Regularization algorithms and mathematical methods for this HTSCs group. Mathematical-programming findings to optimize this Type II HTSCs are presented with ILS outcoming data in Matlab and GNU-Octave. Rulings present an hypothesis of new ‘Molecular Effect’ model/algorithm, intended be proven for this HTSCs group. In this Molecular Effect optimization, Inverse Least Squares and Inverse Least Squares polynomial methods are applied with acceptable Numerical and 2D Graphical Optimization solutions. Results show accuracy with low programming residuals that confirm these findings. Solutions comprise two strands, the modelling for Molecular Effect, and the Inverse Least Squares improved programming methods with confidence intervals and statistical images. Hypothesis in Electronics Physics applications for Superconductors and High Temperature Superconductors emerge from findings. Modelling-hypothesis applications in Superconductor Theory turn up from the numerical and imaging data obtained.

2D Bifurcation diagram of capacitively coupled Josephson junctions in high-Tc superconductors

We study the nonlinear dynamics in an array capacitively coupled Josephson junctions with N=3 junctions. We consider the superconductor/ insulator/ superconductor, SIS, type junctions as a model for high temperature superconductors with layered structure. In this study, we introduce the 2D bifurcation diagrams for the Josephson junctions. First we show a current voltage characteristics (CVC) of Intrinsic Josephson Junctions (IJJs) with N=3 Junctions, then we show the breakpoint region,BPR (a region in which a net electric charge appear on superconducting layers, (S-layers), of junctions), in the CVC of the system, then we try to investigate the chaos in BPR region by the 2D bifurcation diagram of the system. We show the 2D bifurcation diagrams in two cases in which either the coupling factor, α or the β parameter which is related to dissipation, be variable. In the later case we showed there is a range of β parameter in which the chaotic region of BPR is disappeared, also we show that there is another range of β in which the BPR structure disappeared.

Preface

The 7th International Workshop on Numerical Modelling of High Temperature Superconductors (HTS 2020) was held online, hosted by Dr Kévin Berger (University of Lorraine, Nancy, France), on the 22nd and 23rd June 2021. In fact, the HTS 2020 workshop was expected to be held in Nancy in May 2020 but has been postponed due to COVID-19.The workshop received 95 abstracts submitted for presentation and was attended by 115 delegates from around the world. The conference programme covered the latest research and developments in modelling methods and tools to facilitate the accelerated development of superconducting science and technology – including modelling fundamentals, coupled and uncoupled multiphysics problems and applications – with an emphasis on high-temperature superconducting materials.Selected papers presented at HTS 2020 have been published separately in a Special Focus Issue of the journal Superconductor Science and Technology (SUST). This present volume in the Journal of Physics: Conference Series (JPCS) collects together the remainder of the (eight) contributed papers submitted to the HTS 2020 proceedings in JPCS.List of Editors, Scientific committees are available in the pdf

Design and Experimental Research on Self-Shielding DC HTS Cable Model With Large Current Capacity

DC high-temperature superconducting (HTS) cable has advantages over the ac HTS cable in the power transmission due to its zero Joule loss, higher current capacity, and controllability. To minimize the magnetic field influence and critical current degradation in dc HTS cable, we have ever proposed a new structure of dc HTS cable that is, self-shielding dc HTS cable which has interleaved winding configuration. In this paper, in order to solve the difficulty of current lead connection with HTS layer in the cable terminal with multilayers, we put forward a new kind of terminal configuration which can make the current in each layer being controlled individually and avoid soldering in terminal as well as be convenient for installing and disassembly. With this kind of terminal connection method, a dc HTS model cable with eight layers and 1900 mm in length is fabricated and tested in liquid nitrogen temperature. Uniform current distribution among layers is realized by adjustable resistance connecting with each layer. The experimental results show that the critical current degradation of self-shielding dc HTS cable is only 7% compared with the critical current in self-field while the traditional structure of dc HTS cable is about 20%, which indicates that the self-shielding cable can promote the current capacity effectively with lower critical current degradation and save more HTS tapes in the application of power transmission. So, this kind of cable with a thinner insulation layer is suitable for mid- and low-voltage situations, especially for industrial and ship situations where large current and low voltage are required.

Recent Progress and Design of Three-Phase Coaxial HTS Power Cable in Korea

High-temperature superconducting (HTS) power cables were developed recently and have several advantages over conventional cables. For high current capacity, two or more layers are required in one phase of the HTS cable. Differences in the radii between each phase and layer cause inherent imbalance and non-uniform current distribution of three-phase currents. These outcomes must be minimized by properly designing the pitches of multi-layer three-phase coaxial HTS cables. In this paper, the authors design the conduction layers of a multi-layer three-phase coaxial HTS cable and analyze the characteristics of the designed cable based on the proposed PSCAD/EMTDC component and simulation method. A 23 kV/60 MVA multi-layer three-phase coaxial HTS power cable is considered. The conceptual design of a multi-layer three-phase coaxial HTS cable includes the radii of each layer, the number of layers in each phase, and the pitch design of each layer of the cable. Using an impedance matching program, current imbalance can be minimized and current distribution can be made uniform in all layers of the phase by adjusting the pitch length and winding direction. The characteristics of HTS cables using the proposed PSCAD/EMTDC component are analyzed. In this component, the dynamic resistance of current- and temperature-dependent HTS cables is added to the HTS model. AC losses are calculated using the some equation. Induced current loss is calculated based on the material properties of the shield layer. A transient simulation is performed for a three-phase fault of the three-phase coaxial HTS cable using a PSCAD/EMTDC-based simulation method.

A nonlinear peek into stripes

Superconductivity In many theoretical models of high-temperature superconductors, remnants of superconductivity persist to temperatures higher than the transition temperature, T C. Rajasekaran et al. used nonlinear terahertz spectroscopy to probe this region of the phase diagram of a cuprate superconductor that is well known for a stripe phase that appears for certain doping levels (see the Perspective by Ergecen and Gedik). For a sample deep in the stripe phase, a large nonlinear signal persisted from the superconducting region up to temperatures much higher than T C. The findings suggest the formation of a peculiar spatially modulated superconducting state called the pair-density wave. Science , this issue p. [575][1]; see also p. [519][2] [1]: /lookup/volpage/359/575?iss=6375 [2]: /lookup/doi/10.1126/science.aar5254

Detailed investigation of the bifurcation diagram of capacitively coupled Josephson junctions in high-Tc superconductors and its self similarity

We study an array of coupled Josephson junction of superconductor/insulator/superconductor type (SIS junction) as a model for high temperature superconductors with layered structure. In the current-voltage characteristics of this system there is a breakpoint region in which a net electric charge appear on superconducting layers, S-layers, of junctions which motivate us to study the charge dynamics in this region. In this paper first of all we show a current voltage characteristics (CVC) of Intrinsic Josephson Junctions (IJJs) with N=3 Junctions, then we show the breakpoint region in that CVC, then we try to investigate the chaos in this region. We will see that at the end of the breakpoint region, behavior of the system is chaotic and Lyapunov exponent become positive. We also study the route by which the system become chaotic and will see this route is bifurcation. Next goal of this paper is to show the self similarity in the bifurcation diagram of the system and detailed analysis of bifurcation diagram.

Spatial distribution of superconducting and charge-density-wave order parameters in cuprates and its influence on the quasiparticle tunnel current (Review Article)

The state of the art concerning tunnel measurements of energy gaps in cuprate oxides has been analyzed. A detailed review of the relevant literature is made, and original results calculated for the quasiparticle tunnel current J(V) between a metallic tip and a disordered d-wave superconductor partially gapped by charge density waves (CDWs) are reported, because it is this model of high-temperature superconductors that becomes popular owing to recent experiments in which CDWs were observed directly. The current was calculated suggesting the scatter of both the superconducting and CDW order parameters due to the samples' intrinsic inhomogeneity. It was shown that peculiarities in the current-voltage characteristics inherent to the case of homogeneous superconducting material are severely smeared, and the CDW-related features transform into experimentally observed peak-dip-hump structures. Theoretical results were used to fit data measured for YBa2Cu3O7–δ and Bi2Sr2CaCu2O8+δ. The fitting demonstrated a good qualitative agreement between the experiment and model calculations. The analysis of the energy gaps in high-Tc superconductors is important both per se and as a tool to uncover the nature of superconductivity in cuprates not elucidated so far despite of much theoretical effort and experimental progress.

Possible states of charge carriers in thin multilayered superconductive ceramics

This paper analyzes behavior (spectra and states) of the elementary charge carriers in anisotropic perovskite structures, such as modern superconducting ceramics. Translational symmetry of the atom (ion) distribution of the electron (or hole) system is broken by atomic/ionic/molecular sputtering and doping, as well as due to existence of two boundary surfaces. This is a charge carrier's model of high-temperature superconductors in which the observed symmetry breaking orthogonal to CuO planes was treated as a perturbation. The single-particle fermion's wave functions and the possible energies of charge carriers were determined.

Design and PHILS-based Transient Analysis of a Tri-axial HTS Power Cable

Tri-axial high-temperature superconducting (HTS) power cables are very efficient compared with other HTS power cables due to their reduced use of HTS wires and cryogenic surface area, resulting from the mutually layered structure of the three phases. However, the operating characteristics of tri-axial HTS power cables differ from other cables in a transient-state condition. In order to install HTS power cables in a real grid, feasibility verification through simulation or experimentation is required in advance. Thus, the authors design a tri-axial HTS power cable and implement a power hardware-in-the-loop simulation that consists of a real time digital simulator-based simulation model and hardware devices including a power supply and a 1 m-long tri-axial HTS model cable. Simulation results show the stability verification under steady-state and transient-state conditions.

Electrical-Thermal-Structural Coupled Finite Element Model of High Temperature Superconductor for Resistive Type Fault Current Limiters

A multi-physics finite element model of high-temperature superconductors (HTS) will be presented in this article. The electrical-thermal model is mainly based on Maxwell’s equation and basic heat transfer equation to calculate the temperature propagation along the length of the superconducting tapes. According to the calculated temperature profile during quench, the surface thermal stress of the tape is obtained by a structural model. This model can be used to evaluate the degradation of tape performance due to the surface thermal stress, and the results can be used to minimize these effects in the SFCL system. The proposed model is used to investigate the uneven tape, the thickness of the copper layer and YBCO layer which is non-uniform. Methods of smoothing the degradation effect by adding auxiliary fixed points to the tape and changing the basic thickness of copper layer are discussed.

An investigation of the effect of grain size on some properties of intrinsic Josephson junction

Some superconducting parameters of the high temperature superconductors, such as the plasma frequency and the critical transition temperature, depend on the oxygen content of the material. Since the oxygen content is effective on the grain size of the system, the under, optimally and over oxygen doped Hg-based copper oxide layered superconductors, which have the hole type superconductivity, have been investigated in this study. As is known that the concentration of hole type carriers is increased via optimally oxygen annealing. In other words, relatively higher values for the various critical parameters are achieved by the optimally oxygen doping procedure. In this work, the grain sizes of the oxygen annealed samples have been investigated by Scanning Electron Microscopy (SEM). Moreover, the magnetization data obtained via Superconducting Interference Quantum Device (SQUID) has been utilized for calculation of critical current density, which is essential parameter for determining Josephson penetration depth. The Josephson penetration depths of the systems have been calculated by Lawrence–Doniach Model for high temperature superconductors. Since plasma frequency of the system is inversely proportional to Josephson penetration depth, the plasma frequencies of the various doping profiles have also been calculated for the high temperature superconductor investigated.

Electrical-Thermal Coupled Finite Element Model of High Temperature Superconductor for Resistive Type Fault Current Limiter

A multi-physics finite element model of high temperature superconductors (HTS) is presented in this article. An electrical model based on a set of Maxwell's equations and E-J power law is used to solve the critical state of the superconductor. A heat transfer model is added to the electrical model to calculate the temperature distribution and therefore investigate the J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> (T) dependence of the superconductor. The model is used to study the quench behavior of YBCO-coated conductors for the application of resistive type fault current limiters. Some numerical techniques are applied and assumptions are made to simplify the calculation and improve convergence. An equivalent heat transfer coefficient which is much larger than the normal heat transfer coefficient is applied to the region surrounding the superconductors. This equivalent coefficient represents the drastic heat exchange during the boiling of the liquid nitrogen. The cross-section of YBCO tapes is divided into several sub-domains. The temperature is assumed to be uniform in each sub-domain. This simplification significantly improves the convergence of model and still is able to keep a reasonable level of accuracy. The model is then able to simulate the whole process of YBCO tapes quenching and recovering to superconducting state. The numerical results are compared with the fault current experiments and excellent agreement is obtained.

Current Margin of 66 kV Class HTS Power Cable Against Fault Current

In practical applications, high temperature superconducting (HTS) power cables can be subjected to short-circuit fault currents. Further, these cables are assumed to operate over a period of 30 years. Therefore, it is important to investigate the current margin and aging degradation against the fault current. In order to ensure the over-current characteristics of 66 kV class HTS power cables against the fault current, preliminary experiments were carried out on some HTS model cables. Concurrently, numerical simulations were performed to clarify the electromagnetic and thermal behaviors of the HTS model cables under fault conditions. Moreover, the validity of our computer simulation was confirmed by comparing the experimental results with the simulation results. In this study, the maximum fault current in one GdBCO coated conductor assembled in the HTS power cable was numerically simulated. AC over-current experiments were carried out on an HTS model cable by using the maximum fault current of the simulation result to evaluate the current margin against the fault current under conduction cooling and liquid nitrogen bath cooling condition.

Overcurrent Tests and Numerical Simulations on a 66-kV-Class RE123 High-Temperature Superconducting Model Cable

In Japan, the development of a 66-kV-class superconducting power cable was started in 2008 as a national project. A high-temperature superconducting (HTS) power cable typically consists of a copper former, HTS conductor layers, electrical insulation layers, HTS shield layers, and copper shield layers. A 66-kV-class superconducting power cable may be subjected to a fault current of 31.5 kA <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> for 2 s. Therefore, in order to ensure the stability and feasibility of the cable, the thermal characteristics and current distributions of the cable need to be investigated under fault conditions. In this study, overcurrent experiments were performed on a 2-m-long HTS model cable. Numerical simulations were also performed on the model cable by using a computer program on the basis of a 3D finite element method and an electrical circuit model.

Numerical analyses of the electromagnetic force acting on high-temperature superconducting power cables due to fault current

In Japan, the development of the 66 kV class REB2C3O7−x (RE123; RE stands for rare earth) high-temperature superconducting (HTS) power cable was begun in 2008 as a national project. 66 kV class RE123 HTS power cables may be subjected to a fault current of 31.5 kArms for 2 s. Therefore, the electromagnetic and thermal characteristics of HTS power cables have to be determined under fault conditions to ensure stability and feasibility. In this study, numerical analyses were performed using a computer program on the basis of the finite element method and an equivalent circuit model to evaluate the electromagnetic and thermal behaviors of a 66 kV class HTS model cable resulting from the fault current. The electromagnetic forces acting on coated conductors that are assembled in the HTS model cable were also numerically simulated under the fault condition. The result found was that the maximum electromagnetic force acting on the coated conductor in the peeling and compression direction was less than 20 kPa. However, the irreversible Ic degradations caused by the peeling and compression stress were above several MPa in previous studies. Thus, the results of this study indicate a low probability of Ic degradation of the 66 kV class HTS power cable being caused by the electromagnetic force due to the fault current.

Over-Current Characteristics of 66-kV RE123 HTS Power Cable

In Japan, the development of the 66-kV-class superconducting power cable was begun in 2008 as a national project. A high-temperature superconducting (HTS) power cable typically consists of a copper former, HTS conductor layers, electrical insulation layers, HTS shield layers, and copper shield layers. 66-kV-class superconducting power cables may be subjected to a fault current of 31.5 kA <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> for 2 s. Therefore, in order to ensure the stability and feasibility of superconducting power cables, we need to investigate these cables with respect to their thermal characteristics and current distribution under fault conditions. In this study, we carried out over-current experiments on a 2-m-long HTS model cable. We also performed numerical simulations on the model cable by using a computer program developed by us on the basis of a 3D finite element method (FEM) and an electrical circuit model.

Current Margin Against the Fault Current in REBCO Coated Conductors

The application of yttrium barium copper oxide (YBCO) coated conductors in power cables is anticipated. In practical applications, high-temperature superconducting (HTS) cables can be subjected to short-circuit fault current and are expected to operate for over 30 years. In order to safeguard the current margin of YBCO coated conductors against fault current, we carried out preliminary experiments on overcurrent characteristics using an HTS model cable. Meanwhile, we performed numerical simulations to clarify the electromagnetic and thermal behaviors of the HTS model cable. In this study, we numerically simulated the fault current waveform in each YBCO coated conductor that constitutes an entire cable. We then carried out experiments focusing on the current-voltage (I-V) characteristics and the current margin without causing critical current (Ic) degradation against the fault current by varying the amplitude of the waveform obtained numerically. Furthermore, we repeatedly applied the fault current to a YBCO coated conductor to experimentally investigate the Ic degradation caused by iterative fault current.

Inhomogeneity, dynamical symmetry, and complexity in high-temperature superconductors: Reconciling a universal phase diagram with rich local disorder

A model for high-temperature superconductors incorporating antiferromagnetism, d-wave superconductivity, and no double latticesite occupancy can give energy surfaces delicately balanced between antiferromagnetic and superconducting order for specific ranges of doping and temperature. The resulting properties can reconcile a universal cuprate phase diagram with rich inhomogeneity, relate that inhomogeneity to pseudogaps, give a fundamental rationale for giant proximity effects and other emergent behavior, and provide an objective framework to separate essential from peripheral in the superconducting mechanism. high-temperature superconductivity, pseudogap, critical dynamical symmetry, inhomogeneity, complexity, emergent behavior