Low Loss Sintered Dielectric Resonators with HTS Thick Films

The combination of high-Qdielectric resonators and high-temperature superconducting (HTS) films offer many advantages in the area of cellular and satellite communications. The high cost of single crystal dielectrics and HTS thin films may be unattractive in certain applications. Superconducting thick films and polycrystalline ceramic dielectrics offer a high performance, low-cost alternative to high-Qthin film/single crystal dielectric resonators. The loss of polycrystalline ceramics of A1₂O₃, Ba(Mg_1/3Ta_2/3)O₃ (BMT), and Zr_0.875 Sn_0.25Ti0.875O₄ (ZTS) has been studied. Alumina, A1_2Oin3, has been studied as a model material for dielectric loss. Theory predicts that the loss in single crystal sapphire should follow aT ₅ dependence. However, at low temperatures the loss is dominated by extrinsic losses due to crystal imperfection, residual dopant atoms, dislocations, and other lattice defects and theT ₅ dependence does not hold. In polycrystalline alumina the intrinsic loss is immediately masked by these extrinsic losses, even at room temperature, and a simpleT dependence is observed. Results on polycrystalline alumina show that Q’s well in excess of 105 at 10 GHz and 77 K can be achieved in a design made compact by the use of a HTS thick film shield.     

Development of an Impedance Matching Program for Balancing the Current Distribution in a Tri-axial HTS Power Cable

The tri-axial high temperature superconducting (HTS) power cable design has several advantages when compared with other HTS power cables. However, this design has an imbalance in the three phase currents, as the phase conductors of the tri-axial HTS power cable have different radii. The radii of the phase conductors impact the value of inductance and capacitance for the cable, and the values are determined by the winding pitch length and the winding direction. Thus, the current imbalance can be minimized through the adjustment of the winding pitch length, the radius of each layer, and the winding direction. It takes a lot of time to manually calculate an impedance and to find a matched impedance. So the impedance of the tri-axial HTS power cable, according to its shape, was analyzed and the impedance matching program (IMP) was developed using LabVIEW (Laboratory Virtual Instrument Engineering Workbench) to solve this problem. IMP finds the matching impedance automatically by calculating the impedance according to the tri-axial HTS cable dimension. Consequently, this could save a lot of time, and so this program will be applied to the design of the tri-axial HTS power cable effectively.     

Substrate Contribution to the Surface Impedance of HTS Films on Si

We study the effects of semiconductor substrates on the surface impedance of high-T _c Superconductor (HTS) YBa₂Cu₃O_7−δ (YBCO) films. The characteristic impedance of silicon (Si) (for different doping levels and for different charge carrier scattering times) is evaluated. In particular, the most relevant features of Si electrodynamics are highlighted by the introduction of suitable normalized quantities. The effective surface impedance of the YBCO films on Si substrates is then calculated and discussed for different temperatures and frequencies in the microwave range, comparing the obtained results to their limiting expressions for bulk and thin-film HTS. Our analysis shows how the widely used thin-film approximation for the surface impedance can fail, critically highlighting the conditions it requires to be correctly used. We show that substrate contributions can heavily influence the overall response.     

面向CIMS 的纸箱展开尺寸计算子系统的研究与实现

介绍了面向CIMS的纸箱展开尺寸计算子系统的总体结构、主要功能模块和系统实现的关键技术。     

2000安高温超导输电电缆的研制

介绍了6m长2000A高温超导直流电缆－－Bi-2223/Ag带材的主要性能和该高温超导输电电缆的设计、绕制和试验结果。电缆的导体由8层共238根Bi-2223/Ag带材在不锈钢波纹管骨架上螺旋绕制而成,导体的内径为41．5mm,导体层间绝缘,导体层外侧有低温电绝缘。电缆芯的外径为48mm,它安装在低温容器内,并与两个终端相连。电缆的直流耐压大于2．5kV。在液氮下的实验表明,电缆的临界电流为2480A,n值为7．7,接头总电阻为0．1μΩ,均优于设计指标。在1h传输2kA电流的运行中,电缆的传输特性稳定。经4次热循环,电缆的临界电流没有降低。     

Dielectric Resonators for the Measurement of Superconductor Thin Films Surface Impedance in Magnetic Fields at High Microwave Frequencies

We present the design and realization of cylindrical dielectric resonators operating in the 40–60 GHz frequency range, designed for the measurement of the surface resistance and of the surface reactance shift in High-T _c Superconductors (HTS) thin films in a dc magnetic field. The resonators are single tone, based on the TE ₀₁₁ mode, and multiple tone, the latter allowing in principle to exploit the simultaneous determination of the surface impedance at different frequencies. As an application example, we report the temperature and field dependencies of the effective surface impedance of some cuprate superconductors thin films. The results are compared with those obtained through the use of a standard metal cavity with a similar Q-factor and operating in the same frequency range. The comparison highlights a superior stability and a higher sensitivity, resulting in an increase of about two orders of magnitude in the resolution of the surface impedance measurement. By contrast, the dissipative part of the superconducting transition (above T/T _c = 0.97) is better studied with the metal cavity. We also present measurements in the vortex state in YBaCa₂Cu₃O_7−δ and Tl₂Ba₂CaCu₂O_8+x that show significantly different physics. PACS: 74.25 Nf.     

Development of 3kA conduction cooled HTS current lead system

The research and development of superconducting magnet energy storage (SMES) system, a national project, began in 1999. One of the purposes of this project is investigation concerning the application of high-temperature superconducting (HTS) SMES. As a part of this project, the 3 kA class HTS small model coil was manufactured in order to verify the possibility of realizing conduction cooled HTS SMES. Therefore, it is important to develop the conduction cooled current lead system for applying this coil. We developed a kA class conduction cooled HTS current lead system. This current lead system consists of the copper current lead and the YBaCuO (YBCO) HTS current lead. The YBCO bulk manufactured by Nippon Steel Corporation was applied to the HTS current lead. The YBCO bulk keeps high critical current density (J_c > 10,000 A/cm²) in the magnetic field (1 T) at 77 K compared with Bi2223 superconductor. The experiment of this HTS current lead system was carried out, and rated current of 3000 A was achieved successfully.     

Generation of Bulk HTS with Doped Tungstates

Doped tungstates exhibit superconductivity as indicated to occur mainly at the surface of the WO₃ grains present. To generate bulk 3D superconducting material of doped tungstates, it is proposed to employ the recently discovered UV-generated synthesis of complex oxides from mixed simple oxides by illuminating the mixture with ultraviolet light at modest temperatures, as found in Shengelaya’s group in Tbilisi, and to generate a percolating 3D network of 2D superconducting sheets using the smallest basis oxides as the starting material. The latter procedure was demonstrated recently to be very effective in a collaboration with the present author (Daraselia et al., J. Appl. Phys. 121, 145104, 2017). If this proposition is successful, it would establish the doped tungstates as a second group of HTS besides the copper oxides that could be chosen for certain applications.     

Development of Decibel Stepped Attenuator for Automated Sound Level Meter Calibration

MAPAN - Parameter testing in the sound level meter calibration, such as frequency weighting and linearity, needs precise adjustment of sound level in the decibel (dB) unit. In the...     

Accurate Measurements of Surface Resistance of HTS Films Using a Novel Transmission Mode Q-Factor Technique

Microwave characterization of HTS films, using typically a sapphire dielectric resonator can only be as accurate as the Q₀-factor and f_res measurements. A novel Transmission Mode Q-Factor (TMQF) technique has been used for accurate measurements of surface resistance of YBa₂Cu₃O₇ films, with errors lower than 1%. The method allows for accurate determination of Q_L, ₁, and ₂ based on novel equations and a multi-frequency circle-fitting technique applied to S₂₁, S₁₁, and S₂₂ measured around the resonance. Parasitic effects introduced by real measurement systems, namely, noise, crosstalk, coupling loss, coupling reactance, and electrical delay due to uncalibrated transmission lines are compensated for in the new method. Range of unloaded Q₀-factors that can be measured with the TMQF technique is assessed to be from 100 to 10 million at the GHz range of frequencies.     

Development of a HTS magnet and application to a beam scanner

A solenoid magnet using high-temperature superconductor tape was designed, fabricated, and tested for its suitability as beam scanner. After successful cooling tests, the magnet performance was studied using DC and AC currents. With DC current the magnet was successfully operated as mirror coils for a 2.45 GHz ECR ion source. The coils could be operated at 100 A and frequencies above 1 Hz. The installation of iron pole pieces and return yokes, enabled us to generate fields in excess of 2 T at 197 A DC. In AC mode this magnet can be operated in the ranges of 0.14–1.73 and 1.22–1.67 T at frequencies of 0.05 and 0.25 Hz, respectively.     

纳米阻抗显微镜的研制及商品化

纳米阻抗显微镜(Nanoscale impedance microscopy,NIM)能够测量材料表面的纳米微区阻抗性质,已经成为纳米材料表征的重要工具,得到越来越多的应用;但其应用目前仅局限于实验室范围,而国内尚未有纳米阻抗显微镜研究的文献报道.本文主要介绍纳米阻抗显微镜的基本原理及其仪器的研制.以国内外现有的扫描探针显微镜仪器为基础,研制出了两套不同的纳米阻抗显微镜样机,并率先实现了这种技术的商品化,还利用该技术开展了氧化锌多晶陶瓷材料的应用研究.     

Analysis of a Stepped Air Line Using an Air Line Simulator

A stepped air line is investigated by using the mode matching method with mode expansion in the transverse direction of the line. To account for the effect of the air line loss, particularly on the propagation constant, a loss compensation is applied. Next, we develop a stepped air line simulator with a GUI-based program language. The competitiveness of the simulator is numerically verified with simulated results of a commercial FEM tool and experimentally with measured results of commercially available air lines with a vector network analyzer up to 50?GHz. Simulated S-parameters of a stepped air line with specific step diameters are presented.     

Development of a single-phase 30 m HTS power cable

HTS power transmission cables appear to be the replacement and retrofitting of underground cables in urban areas and HTS power transmission cable offers a number of technical and economic merits compared to the normal conductor cable system. A 30 m long, single-phase 22.9 kV class HTS power transmission cable system has been developed by Korea Electrotechnology Research Institute (KERI), LS Cable Ltd., and Korea Institute of Machinery and Materials (KIMM), which is one of the 21st century frontier project in Korea since 2001. The HTS power cable has been developed, cooled down and tested to obtain realistic thermal and electrical data on HTS power cable system. The evaluation results clarified such good performance of HTS cable that DC critical current of the HTS cable was 3.6 kA and AC loss was 0.98 W/m at 1260 Arms and shield current was 1000 Arms. These results proved the basic properties for 22.9 kV HTS power cable. As a next step, we have been developing a 30 m, three-phase 22.9 kV, 50 MV A HTS power cable system and long term evaluation is in progress now.     

Finite element analysis of the localised thermal quench of an HTS tape

In this work, we perform a finite element method (FEM) analysis of the localised thermal quench of a high temperature superconducting (HTS) tape. One 3D thermo-electric coupling FEM model, which is constructed to address the actual development of the localised thermal quench occurred in the HTS tape, has been proposed. One quench experiment is performed to validate this model. It is shown that the mode can quantitatively reflect the dynamic and static quench characteristics when comparing the results of the experiment with the model. The FEM model generates an estimate of the location of the highest temperature and visualisation of the quench dynamics.     

Fabrication of a highly sensitive magnetic sensor using an HTS thick film

A highly sensitive magnetic sensor based on Y₁Ba₂Cu₃O_7−x (YBCO) has been fabricated by the spray technique. The value of resistance R_ms in the transitional region ΔT of the thick film, was highly sensitive to the applied magnetic field B_ex. Here, ΔT is the transitional temperature region between the resistance drop temperature T_c^onset and residual resistance temperature T_c^res. The value of residual resistance R_res for an applied magnetic field of 80×10⁻⁴ T (80 G) exhibited an increase of about 580% over the resistance found in a zero magnetic field, and did not display any evidence of hysteresis. The fabrication and magnetic characteristics are discussed.     

微机械谐振器可变锚点结构能量耗散特性分析

微机械谐振器在振动过程中总会产生能量耗散,并且具有诸如空气阻尼耗散、热弹性阻尼耗散、锚点结构耗散、表面耗散等诸多耗散机制,其中锚点结构耗散是一种主要的能量耗散机制。应用完美匹配层方法,将无限大区域入射波的吸收问题转化到有限区域内进行。针对中心支撑圆盘体模态谐振器,设计两种不同的锚点支撑结构,并分别讨论其几何结构的变化对谐振器固有频率和锚点损耗品质因子的影响。结果证明通过调整锚点结构,可以大幅度提高谐振器的锚点耗散品质因子,提高能量的利用效率。     

Development of 500 m HTS power cable in super-ACE project

A high temperature superconducting power cable (HTS power cable) is highly promises as a low cost and large capacity power line. An HTS cable is also effective in increasing power capacity of underground cable in a city part. A demonstration of a 500 m HTS cable that contributes to research for commercial applications was planned in a part of “Super-ACE project” of METI (Ministry of Economy, Trade and Industry). Furukawa Electric has been taking charge of designing, manufacturing and installation of the 500 m cable. The cable is a 77 kV 1 kA single-core cable with liquid nitrogen (LN₂) impregnated paper insulation. The manufacturing and the installation of the cable have been completed in November 2003, and now preparations of peripheral equipments are proceeding for a test starting in March 2004. This paper describes the design, manufacturing and installation of the 500 m HTS cable.