High-Tc superconducting monolithic phaseshifter

A high temperature superconducting (HTS) X-band phase shifter using a distributed Josephson inductance (DJI) approach was designed and fabricated. Phase swings of over 60° were measured at 65 K and below, with measurable phase shifts at temperatures above 77 K. High quality HTS films and superconducting quantum interference devices (SQUIDs) were deposited by laser ablation. A total of 40 HTS step edge SQUIDs were successfully integrated into a monolithic HTS circuit to produce a phase shifter in a resonant configuration. The magnitude of the Josephson inductance is calculated and a lumped element model is compared to measurements     

The new generation of superconductor equipment for the electric power grid

High-temperature superconductor (HTS) power equipment, such as power cables, synchronous condensers, fault current limiters (FCLs), and transformers, are poised to address key technical issues in the U.S. Power grid. This equipment is enabled by the successful development of robust long-length HTS wire, available commercially from a variety of manufacturers worldwide. Compared to conventional cables, HTS power cables offer higher capacity with minimal disturbance to neighboring underground infrastructure, and their low series impedance opens the opportunity for cost-effective power flow control with phase angle regulators. HTS cables are being actively prototyped worldwide. Based on technology developed for industrial and ship propulsion motors, an HTS synchronous condenser has been developed and successfully tested in the Tennessee Valley Authority (TVA) grid; this is the first HTS power equipment to be offered commercially. It addresses the growing need for dynamic reactive power compensation for grid stability and power quality. HTS FCLs and transformers are also in active development.     

一种简单的高温超导连续通带双工器设计

在双抛LaAlO3衬底上外延生长的钇系高温超导薄膜YBCO的基片上,设计并制作一个四级高温超导连续通带双工器（工作频率3.0～3.5GHz和3.5～4.0GHz）,与常规金属材料的双工器相比,体积减少3/4,插损减少2dB。在液氮温区77K时,测试结果为：通带内插损小于0.8dB,通带间带外抑制大于30dB通带中心频率。为近一步研制高温超导多工器提供了很好的借鉴,对将来高温超导信道化接收机系统的研究和设计具有重要的意义。     

Electronics for a high temperature superconducting receiver systemfor magnetic resonance microimaging

Describes an MRI (magnetic resonance imaging) receiver system that incorporates a high temperature superconducting (HTS) resonator as a surface coil. Techniques for measuring the Q of the HTS resonator in a 7 Tesla field are discussed. A method for coupling a room temperature copper resonant circuit to the HTS element is covered, and it is shown that such a coupling scheme preserves the signal-to-noise gain afforded by the HTS coil. A preamplifier with a noise figure of <0.15 dB at 300 MHz is described     

Scattering parameter and bit error rate characterization of hightemperature superconducting coplanar transmission lines

We report the gigahertz experimental results of time and frequency performance on YBCO high temperature superconductor (HTS) and gold coplanar transmission lines. An on-wafer direct probing measurement system was used to collect data at cryogenic temperatures on both YBCO and gold coplanar lines. The insertion loss of the 6-cm lines at a frequency of 3.0 GHz was measured to be -0.12 dB for the superconducting line compared to -10.7 dB for the gold line at 80 K. Error rate and eye-diagram measurements were performed on the packaged lines and show the correlation between the insertion loss of the line and the attenuation of a Pseudo Random Bit Sequence (PBRS). The superconducting line measured at 77 K had a BER rate of less than 10^-11 at a data rate of 3 Gb/s. The measured eye height was 350 mV for the YBCO compared to 100 mV for a gold line at 3 Gb/s and a temperature of 77 K for the packaged 6-cm lines     

Method for estimating future markets for high-temperature superconducting power devices

This paper describes a spreadsheet model for estimating the impact of high-temperature superconducting (HTS) power devices on the national electric grid. The distribution of losses in the national grid is carefully traced and those losses that HTS can eliminate are identified. The energy savings achievable by the many sizes of HTS generators, transformers, cables, and motors are then computed and totaled using a spreadsheet analysis. The economic savings are very sensitive to the price (and J/sub e/) of HTS wire, and to the cost of cooling the devices to operating temperature. A market penetration model is used to estimate how fast HTS devices become commercially,successful. The emphasis of the paper is the analytic tool, not the numerical results of one specific case. This entire model is explicitly designed to allow others to enter their own estimated parameters and arrive at their own conclusions.     

Alternative Designs of High-Temperature Superconducting Synchronous Generators

This paper discusses the different possible designs of both cored and coreless superconducting synchronous generators using high-temperature superconducting (HTS) tapes, with particular reference to demonstrators built at the University of Southampton using BiSCCO conductors. An overview of the electromagnetic, thermal, and mechanical issues is provided, the advantages and drawbacks of particular designs are highlighted, the need for compromises is explained, and practical solutions are offered. The scalability of results obtained from small demonstrators is considered.      

Analytical model of superconducting to normal transition of bulk high Tc superconductor BSCCO-2212

A comprehensive theoretical expression for the superconducting-to-normal transition of high-temperature superconducting (HTS) materials is derived. The electric field and resistivity of bulk melt-cast processed BSCCO-2212 are derived from the superconducting, flux creep, flux flow, and resistive properties of high critical temperature superconductors (HTS). An asymptotic function is used to model the Bean and Ohmic limits of the E(B,T,J) characteristics. Comparison is made with the experimental results of Elschner et al. The new model may be used in simulating the operation of HTS power equipment, and may be applicable to other HTS materials.     

High-Temperature Superconducting Loss-Free Delay Network for High-Power Pulse

In this paper, a high-temperature superconducting (HTS) loss-free delay network for high-power pulses is performed. Based on the voltage and current pulse experiments carried out at 300 and 77 K, experimental results demonstrate that, under the matched resistive load condition, compared with a normal conducting lossy delay network, the HTS loss-free delay network can effectively reduce the amplitude attenuation of voltage pulses and the front-edge distortion of current pulses.     

High-temperature superconducting magnet motor demonstration

A superconducting field winding, assembled with coils constructed with Bismuth 2223 HTS wire, has been successfully operated in an electric homopolar motor. At a field winding temperature of 4.2 K, the motor produced 125 kW of output power. At a temperature of 28 K, the motor power developed was 91 kW. These measured power levels are the highest that have been produced by an electric motor containing a HTS field winding     

Conceptual design of an electrical machine with both low and high Tc superconductors

The emergence of high T_c superconducting (HTS) wires with large critical current densities allows the design and construction of many applications, for example, rotating electrical machines. Nevertheless, the current “state of the art” of Bi “powder in tube” wires, the most advanced HTS conductor, is not adequate for an ac operation. We thus propose a fully superconducting synchronous machine with an NbTi stationary 4 K armature and a rotating Bi-2223 field winding at 20 or 40 K. Thanks to the armature cryogenic environment, the cooling of the Bi coils is very simple. The conceptual design of a typical machine is suggested and several electromagnetic designs are presented. The first one deals with a Bi field winding adapted to an existing NbTi armature of a tenth of kYA. Afterwards, large torque motors are theoretically designed comparing the high (at 20 and 40 K) and low T_c field winding solutions. The results are comparable for NbTi and Bi at 20 K. But with a Bi field winding operating at 40 K, the performances are degraded. Otherwise, at 4 or 20 K fully superconducting motors show high performances in terms of weight, volume, and efficiency. Nevertheless, the Bi field windings require a large amount of material indicating that improvements in critical current density are needed     

Design of a linear bulk superconductor magnet synchronous motor for electromagnetic aircraft launch systems

High-temperature superconducting (HTS) material in bulk form is used to design a linear synchronous motor for an electromagnetic aircraft launch system. The motor is designed without an iron core. Stator coils are placed in the air while the permanent magnets used in conventional design of linear permanent magnet synchronous motors are replaced by the HTS bulk magnets. The physical, operational, and equivalent circuit parameters of the linear motor with HTS bulk magnets are compared with those of a linear permanent magnet synchronous motor and linear induction motor designed for the same application. Results show that utilizing superconducting magnets is only superior at temperatures below 40 K.     

激光光热法测试YBCO 高温超导带材热扩散率

根据激光光热法原理建立了高温超导带材低温真空环境下热扩散率测试系统。通过研究热扩散率与加热激光调制频率及热波通过样品时产生的相位差之间的关系，提出了激光光热法测试热扩散率实验数据处理新思路，消除了系统误差的影响。为了探讨测试方法的可靠性，以热扩散率已知的紫铜为标准样品进行了测试。在此基础上，对YBCO高温超导带材进行了测试，获得了其在40~120K温区的热扩散率数据。YBCO 高温超导带材热扩散率随温度升高而降低，尤其在40~60K温区下降较快。     

Characteristics of smooth and periodic HTS coplanar resonators on ferroelectric/dielectric substrates

Characteristics of smooth and periodic (consisting of sections with different dimensions) high temperature superconducting (HTS) thin film coplanar waveguide (CPW) resonators with a ferroelectric component were calculated. Frequency tunability and microwave (MW) losses of the structure were analyzed using the obtained formulas. It was shown that for the ferroelectric layer thickness less than 100 nm, the MW losses are determined by the losses of HTS electrodes, while for thicker layers, the MW losses are completely determined by the loss tangent of the ferroelectric. Experimental aspects of the problem were investigated in the example of a YBCO/Ba/sub x/Sr/sub 1-x/TiO/sub 3/ smooth CPW resonator at 77 K and information about the permittivity and the loss tangent of the ferroelectric was obtained.     

Superconducting quasi-lumped element filter on R-plane sapphire

Recent advancement in superconducting microwave technology has led to commercial deployment of high-temperature superconducting (HTS) subsystems for wireless communication applications. Commercialization of the HTS thin-film devices lies within, among other factors, the quality and consistency of the HTS film, as well as the overall cost and performance of the subsystem. In this paper, we present the design and performance of a quasi-lumped element filter on sapphire substrate. Centered at 1857 MHz with 0.8% fractional bandwidth, the six-pole Chebyshev filter has an insertion loss of less than 0.2 dB at 60 K, which translated into a realized unload Q of 35000. This is an important step toward the commercialization of superconducting devices using industrial standard wafers. With the continuous improvement of the HTS film quality, YBCO film on sapphire could be an answer to the future     

Superconducting Electronics Research at CSIRO Australia ——20 Years after Discovery of HTS

CSIRO has had a long-term research effort in superconductivity, in particular, since the discovery of HTS which promised big prospects. Significant progress has been made in research and development of HTS electronic devices and systems for practical applications such as mineral and exploration as well as some niche applications in emerging science and technology areas. This article presents an overview of the CSIRO research activities in HTS supercon- ducting electronics since 1987, outlining the HTS junction and device technology as well as various application systems developed by the group.     

Si-YBaCuO intermixing and reactive patterning technique

A novel Si-YBaCuO intermixing technique has been developed for patterning YBaCuO superconducting thin films on both insulating oxide substrates (MgO) and semiconductor substrates (Si). The electrical, structural, and interfacial properties of the Si-YBaCuO intermixed system have been studied using resistivity, x-ray diffraction, scanning electron microscopy, x-ray photoelectron spectroscopy and Auger depth profiling measurements. The study showed that the reaction of Si with YBaCuO and formation of silicon oxides during a high temperature process destroyed superconductivity of the film and created an insulating film. On a MgO substrate, the patterning process was carried out by first patterning a silicon layer using photolithography or laser-direct-writing, followed by the deposition of YBaCuO film and annealing. For a silicon substrate, thin metal layers of Ag and Au were patterned as a buffer mask which defines the YBaCuO structures fabricated thereafter. Micron-sized (2-10 Μm) superconducting structures with zero resistance temperature above 77 K have been demonstrated. This technique has been used to fabricate current controlled HTS switches and interconnects.     

Design of high-temperature superconducting low-pass filter forbroad-band harmonic rejection

A new type of low-pass filter based on a coupled line and transmission line theory is proposed for suppressing harmonics and spurious frequency. The seventh-order coupled-line low-pass filter with strip line configuration was fabricated using a high-temperature superconducting (HTS) thin film on MgO(100) substrate. The seventh-order low-pass filter has five attenuation poles in the stop band. Its cutoff frequency is 1 GHz with a 0.01-dB ripple level. The fabricated filter exhibits a characteristic stop band in the range from 1 to 7 GHz. A measured insertion loss at the pass-band of the HTS low-pass filter is 0.2 dB at 77 K, while the maximum return loss is 17.1 dB. These results match well with those obtained by the EM simulation. The new low-pass filter structure is shown to have attractive properties such as compact size, wide stop band range, and low insertion loss     

Superconducting Electronics Research at CSIRO Australia-20 Years after Discovery of HTS

CSIRO has had a long-term research effort in superconductivity, in particular, since the discovery of HTS which promised big prospects. Significant progress has been made in research and development of HTS electronic devices and systems for practical applications such as mineral and exploration as well as some niche applications in emerging science and technology areas. This article presents an overview of the CSIRO research activities in HTS superconducting electronics since 1987, outlining the HTS junction and device technology as well as various application systems develop by the group.     

Superconducting magnet system of the CMD-2 detector

This paper describes the superconducting magnet system of the CMD-2 detector. The magnetic field is provided by the main and two compensating superconducting solenoids. The unique features of this system are the solenoids protection method utilizing a distributed resistance along the coil and the power supply being a fluxpump type. The main solenoid produces a field up to 1.2 T in a volume of φ 0.71 m×0.9 m. Its radiation thickness and E/M ratio are 0.38 X₀ and 5 kJ/kg, respectively. NbTi/Cu superconducting cables without any insulation and an aluminum stabilizer were used for the design of solenoid coils. The superconducting cable was wound in a stainless-steel bobbin and soldered by a PbSn alloy. The cooling bath provides a temperature of 4.2 K in the system. The superconducting magnet system of the CMD-2 detector was manufactured and tested in 1989