1988 Applied Superconductivity Conference

The following topics are dealt with: superconducting electronics; superconducting quantum interference devices (SQUIDs); magnetometers; Josephson device memories; thin-film superconducting materials; tunnel junctions; Josephson device logic circuits; high-T_c (critical temperature) superconductors; YBaCuO superconductors: ceramic superconductor memories; millimeter-wave detectors; Josephson device mixers; superconducting transmission-line structure; superconducting microwave cavities; tunnel spectroscopy; laser-induced switching of superconductors; gradiometers; harmonic mixing; SIS (superconductor-insulator-superconductor) mixers; superconducting bolometers; superconductor device fabrication; SSC; (Superconductor Super Collider); magnets; superconducting magnets; chaos in Josephson junction systems; superconducting coils; superconducting material preparation; MHD; (magnetohydrodynamics) magnets; magnetic resonance imaging (MRI) magnets; and niobium materials devices     

Research and development at the Japanese National Research Institute For Metals

Research activities at the National Research Institute for Metals on high-field superconducting materials and the structure materials for cryogenic use are described. The superconducting materials research building equipped with a 17.5 T superconducting magnet, was recently constructed in Tsukuba New Science City of Japan to further progress in the superconducting and cryogenic engineerings.     

Entangling a single NV centre with a superconducting qubit via parametric couplings between photons and phonons in a hybrid system

We propose an efficient scheme for generating entangled states between a single nitrogen-vacancy (NV) centre in diamond and a superconducting qubit in a hybrid set-up. In this device, the NV centre and the superconducting qubit couple to a nanomechanical resonator and a superconducting coplanar waveguide cavity, respectively, while the microwave cavity and the mechanical resonator are parametrically coupled with a tunable coupling strength. We show that, highly entangled states between the NV centre and the superconducting qubit can be achieved, by means of the Jaynes–Cummings interactions in the NV-resonator and qubit-cavity subsystems which transfer the entanglement between the vibration phonons and the cavity photons to the NV centre and the superconducting qubit. This work may provide interesting applications in quantum computation and communication with single NV spins and superconducting qubits.     

A superconducting stepping motor with pulsed-field magnetization for a pump

Pulsed-field magnetization is applied to a superconducting stepping motor to improve its rotor dynamics. The superconducting motor is composed of a superconducting rotor, a stator with eight electromagnets, a computer and a pulsed-power supply. Pulsed-field is applied to the superconducting rotor before the rotation. Moreover, the superconducting stepping motor is then applied to a pump that can function at extremely low temperatures. Pulsed-field magnetization is also applied to the pump motor in order to improve the performance of the pump. The static and dynamic characteristics of the motor and the pump are discussed.     

Power Absorption Efficiency in Superconducting Fiber Optical Waveguides

By using an analytical model and a finite element method, we investigate a new, very sensitive, superconducting traveling wave photodetector made by a fiber waveguide, which includes two high index layers and an active superconducting layer. A comparison with the corresponding superconducting box shaped waveguide shows that a larger width of the superconducting layer can be used to obtain single degenerate hybrid mode HE ₁₁. The real part of the propagation constants in the fiber is smaller in comparison with that of the box-shaped waveguide with similar dimensions but the imaginary part of the propagation constant and the power absorption efficiency in superconducting layer are comparable with those of the corresponding box-shaped waveguide. The confinement regimes of the light and the power absorption efficiency in superconducting layer can be optimized by only acting on the fiber geometry.     

管内电缆导体稳定性研究方法新探

管内电缆导体（ＣＩＣＣ）,是目前大型低温超导磁体的首选导体。随着超导技术的发展,ＣＩＣＣ在大型超导核聚变实验装置及超导储能磁体中的应用具有不可比拟的优越性。为降低导体成本而提出了在ＣＩＣＣ中采用的超导股线配以纯铜股线的设计方案,开展含纯铜股线ＣＩＣＣ稳定性机理及实验的研究,并开发ＣＩＣＣ优化设计软件,对ＣＩＣＣ在高科技术中的应用意义重大。     

Impregnation of superconducting solenoid with cryocon grease

Impregnating superconducting coils with various materials is used as a technique to prevent wire movements which lead to premature quenching of superconducting coils. This report describes the effect of using cryocon grease to impregnate the coils of laboratory scale superconducting solenoids.     

The superconducting transition temperature of multilayer superconductors: The frustratedXY-Josephson model

The superconducting transition temperature of multilayered superconducting structures of the S-N(D)-S type in the RVB theory is defined taking into account the resonance pair “tunneling” between superconducting layers. The Josephson array defectivity is considered with the frustration parameters.     

The Mott-Hubbard insulating state and orbital degeneracy in the superconducting C60(3-) fulleride family

Electron correlation controls the properties of important materials such as superconducting and magnetoresistive transition metal oxides and heavy fermion systems. The role of correlation in driving metal-to-insulator transitions assumes further importance because many superconducting materials are located close to such transitions. The nature of the insulating ground state often reveals the dominant interactions in the superconductor, as shown by the importance of the properties of La2CuO4 in understanding the high-temperature-superconducting cuprates. The A3C60 alkali metal fullerides are superconducting systems in which the role of correlation in both the normal state and the superconducting pairing mechanism is controversial, because no magnetic insulator comparable to the superconducting materials has been identified. We describe the first example of a cubic C60(3-) system with degenerate orbitals that adopts the Mott-Hubbard insulating localized electron ground state. Electron repulsion is identified as the interaction that is suppressed on the transition to metallic and superconducting behaviour in the fullerides. This observation is combined with ab initio calculations to demonstrate that it is the orbital degeneracy that allows the superconducting cubic A3C60 fullerides to remain metallic while provoking electron localization in systems with lower symmetry.     

The superconducting transition temperature of multilayered superconductors. The frustratedXY-Josephson model

The superconducting transition temperature of multilayered superconducting structures of the RVB theory for the S-N(D)-S type is defined taking into account the resonance pair “tunneling” between superconducting layers. The Josephson array defectivity is considered with the frustration parameters.     

Cryogen-free HTS coil placed in a heat-exchange gas

Poorly cooled regions in cryogen-free superconducting windings represent weak points especially in high-current-density superconducting windings of superconducting magnets with complicated geometry. It is quite natural taking into account the low average heat conductivity of the superconducting winding. In this paper, we propose to cool the winding mainly not by thermal conductivity but by heat exchange with the low-pressure gaseous helium placed in a hermetic envelope around the winding. The envelope is cooled through its thermal contact with a cooler head. The method was experimentally checked and its advantages are discussed.     

Current and current density distribution in parallel superconducting wires in a planar array in the meissner state

The current distribution in parallel superconducting wires is influenced by the Meissner effect. In order to treat this quantitatively, the behaviour of superconducting cylinders in an inhomogeneous magnetic field was examined and the results were applied to a planar arrangement of parallel superconducting wires. How the current distribution between the conductors and the current density distribution along the circumference of each wire behave, if the distance between the conductors is varied, is also discussed, together with the effect of varying the number of wires on the current distribution. Finally the current distribution in a planar array of superconducting wires is compared with the current density distribution in a thin superconducting layer. Experimental results supporting the above mentioned theoretical considerations will be presented.     

Superconducting resonance systems in precise measuring units

This paper presents the results of studies on high stability oscillators with superconducting resonance systems incorporated, which operate at superhigh and radio frequencies. A superconducting resonance system was also used to build a model superconducting gravimeter of 10^?10 g sensitivity.     

RRR300超导铌板结晶转变温度研究

RRR300超导铌板是制作超导腔的主要材料,为了减小制备超导腔时的阻力,有必要进行退火,提高材料塑性.通过采用不同退火温度对RRR300超导铌板进行退火,观察RRR300超导铌板显微组织、力学性能以及RRR值变化,确定了 600℃为RRR300超导铌板的结晶转变温度,750℃为最理想的热处理温度,此温度下,力学性能、显...     

Superconducting magnets in the world of energy,especially in fusion power

Industrial applications of superconducting magnets are only feasible in the near future for superconducting homopolar machines and possibly MHD generators. In both cases there are no longer any major problems with the superconducting windings or cryogenic systems, but technological problems connected with other components are governing the chances of large scale applications.For superconducting synchronous machines, after the successful operation of machines in the MVA range, a new phase of basic investigations has started. Fundamental problems which could not be studied in the MVA machines, but which influence the design of large turbo-alternators, must now be investigated.Fusion power by magnetic confinement will probably be the largest field of application for superconducting magnets in the long run. The present research programmes require large superconducting magnets by the mid-1980s for the experimental reactors envisaged at that time.In addition to dc windings, pulse-operated superconducting windings are required in some systems, such as Tokamak. The high sensitivity of the overall plant efficiency and the active power demand of the pulsed windings require great efficiency from energy storage and transfer systems. Superconducting energy storage systems would be suitable for this, if transfer between inductances could be provided with sufficient efficiency. Basic experiments gave encouraging results.In power plant systems and electric machines an extremely high level of reliability and availability has been achieved. Less reliability will not be accepted for systems with superconducting magnets. This requires great efforts during the development work.     

环氧树脂固化工艺条件对YBCO超导带材临界电流的影响

为了研究固化条件对超导带材临界电流的影响,采用电测法实验测量了多种固化工艺条件下YBCO高温超导带材的临界电流。分析得到热处理温度140℃时,超导带临界电流出现明显退化,温度越高退化越明显;超导带临界电流随着固化时间的延长而降低,处理温度越高,随时间下降的幅度越大,并从超导体钉扎效应的角度对实验结果进行了初步的分析。     

Low-temperature structural studies of Tl2Ba2CaCu2O x

Low-temperature x-ray diffraction studies of superconducting Tl-2212 ceramics revealed anomalies in thec cell parameter andc-axis thermal expansion coefficient near the superconducting transition. Air and vacuum anneals in the range 400–550‡C demonstrate that these anomalies correlate with the superconducting properties of the material. The anomalous temperature variation of thermal expansion suggests that the superconducting transition is accompanied by significant changes in the phonon spectrum.     

Vortex Structure in an Antiferromagnetic Superconductor

The structure of a superconducting vortex in a dirty antiferromagnetic superconductor (AFSC) has been studied theoretically. We show that a superconducting vortex in AFSC has an antiferromagnetic core. The existence of superconducting vortex with antiferromagnetic cores may have nontrivial influence upon transport properties of type-II AFSC in magnetic field.     

New method of selecting the optimum geometrical parameters in the design of superconducting solenoids

A new method of selecting the optimum geometrical parameters in the design of superconducting solenoids has been proposed. The volume of superconducting winding can be much reduced and the homogeneity of the magnetic field is improved. A design example has shown that the volume of superconducting winding was reduced by 29% in comparison with the volume minimized coil with a rectangular winding cross-section.     

高温超导带材低/变温疲劳性能测试系统的研制

实用化高温超导带材(如Bi系与ReBCO高温超导复合带材)在高磁场下拥有较高的临界电流密度、宽泛的温度裕度、较强的抗粒子辐照能力及良好的机械特性,因此这类材料在加速器超导磁体系统、高场超导磁体、超导电力等方面表现出巨大的应用潜力。而作为典型的多层功能复合性材料,虽然高强度的基底层增强了高温超导带材拉伸强度,使其在强磁场、高载流条件下可以承受很高的应力,在其加工与运行过程中,不可避免地受到多种疲劳载荷的作用,从而其临界载流能力会显著地降低,进一步,会造成相应高温超导装置功能性难以达到设计标准等。该文介绍一种自主研制的高温超导带材低/变温疲劳性能测试系统,基于该测试系统:一方面,可以实现对高温超导材料在低/变温、疲劳载荷等环境下力学、热学等宏观参数的实验表征研究;另一方面,可以对高温超导材料开展低温疲劳载荷环境下力-电弱化等临界特性的实验研究。利用所研制的低/变温疲劳性能测试系统,对受拉-压疲劳荷载下的YBCO超导带材的力学行为、载流特性开展了初步的实验研究,并分析了应力比、温度等外部环境因素对实验结果的影响规律等。结果表明:在相同的疲劳次数的情况下,YBCO超导带材的力学性能及载流特性与其应力比成明显的非线性关系。该测试系统的成功研制将为中国粒子加速器用高温超导磁体的设计与研发提供基础测试平台。