bluuebunny/crossref_metadata_2025_split huggingface dataset:
HTS CroCo - a Strand for High Direct Current Applications
Authors: Wolf M J , Fietz W H , Heiduk M , Heller R , Lange C , Preuß A , Weiss K-P 
Published: August 2020

Abstract
High temperature superconductors (HTS) are discussed as energy-efficient solutions for applications needing high direct currents beyond 10 kA e.g. for large high-field magnets or bus bar systems in industrial electrolysis plants. A number of high-current cable concepts based on REBCO tapes were developed such as the Roebel cable, co-axially wound tapes and several stacked-tape arrangements, among them the HTS CrossConductor (HTS CroCo), a stacked-tape conductor with high current density developed at KIT. In this manuscript, the experimental test of a high DC demonstrator, termed Supra-DC-Cable, made from twelve HTS CroCo strands is presented. The demonstrator was tested successfully at T = 77 K, reaching the expected critical current of 33 kA at 77 K and even for a constant-current operation at 36 kA for more than 30 minutes limited by the copper connections, not the superconducting cable. Currents and voltages were measured in all twelve strands individually during the parallel operation in the cable. These measured data allow the experimental validation of the modelled current distribution, based on the individual characterization of the twelve strands.
Evaluation of superconductor assisted machining (SUAM) with superconducting coated conductors using the finite element method
Authors: Kinoshita Y , Zhang R , Otabe E S , Suzuki K , Tanaka Y , Nakashima H , Nakasaki T 
Published: August 2020

Abstract
In the present study, we numerically calculated the magnetic levitation force for superconductor assisted machining (SUAM) using the finite element method. Although we usually use bulk superconductors for magnetic levitation in SUAM, we herein considered magnetic levitation using superconductor-coated conductors. We were able to explain the experimental results on the forces of the coated conductors as well as bulk theoretically. For both bulk and coated conductor, the repulsive force was found to increase as the distance from the permanent magnet became shorter. For the coated materials, both the repulsive and attractive forces were lower than in the case of bulk superconductors. This is because the volume of superconducting material was smaller than in the case of bulk superconductors, since the overall size of both materials was the same. However, we believe that greater forces can be obtained by increasing the number of coated conductors.
Magnetic Flux Trapping and Flux Jumps in Pulsed Field Magnetizing Processes in REBCO and Mg-B Bulk Magnets
Authors: Oka T , Takeda A , Oki H , Yamanaka K , Dadiel L , Yokoyama K , Häßler W , Scheiter J , Sakai N , Murakami M 
Published: August 2020

Abstract
Pulsed-field magnetization technique (PFM) is expected as a cheap and an easy way for HTS bulk materials for utilizing as intense magnets. As the generation of heat due to magnetic flux motion in bulk magnets causes serious degradation of captured fields, it is important to investigate the flux motions during PFM in various field applications. The authors precisely measured the magnetic flux motion in the cryocooled MgB2 bulk magnets containing various amount of Ti. We classified the motions to “no flux flow (NFF)”, “fast flux flow (FFF)”, and “flux jump (FJ)” regions. The results showed that addition of Ti shifts the field invasion area to high field areas, and expands the NFF regions. The highest field-trapping appears at the upper end of the NFF region. Since the heat generation and its propagation should attribute to the dissipation of magnetic flux, FFF leads to FJ. Compared with MgB2, we referred to GdBCO as for the flux motion. A flux jump was observed at 30 K when the pulse field of 7 T was applied to the preactivated sample, showing its stability against FJ.
Fabrication and Characterizations of KCa2Fe4As4F2 Superconducting HIP Wires
Authors: Pyon S , Miyawaki D , Tamegai T , Kajitani H , Koizumi N , Awaji S , Kito H , Ishida S , Yoshida Y 
Published: August 2020

Abstract
We report the fabrication and characterizations of KCa2Fe4As4F2 round wires for the first time. Polycrystalline KCa2Fe4As4F2 powder was prepared by solid-state reaction. Superconducting wires were fabricated by powder-in-tube (PIT) method followed by hot-isostatic-press (HIP) technique. The self-field J
c of the KCa2Fe4As4F2 HIP wires fabricated at 700 and 740°C at a high pressure of 9 MPa for 0.5 h, reached 10 kAcm−2. Although high-pressure sintering at high temperatures enhanced the J
c and density of the core of the wires, X-ray diffraction and scanning electron microscopy–energy-dispersive X-ray spectroscopy analyses indicated that impurity phases were present both in the polycrystalline powder and in the core of the wire.
Effect of the metallic oxides mix-doping on the microstructure and superconducting properties of Bi-2223 Ag/tapes
Authors: Lu X Y , Yi D , Nagata A 
Published: August 2020

Abstract
The Bi-2223 Ag/tapes with the composition Bi1.8Pb0.4Sr1.9Ca2.1Cu3.5Oy + Xn (X1: un-doped; X2: 1wt% MgO + 1wt% Ag2O; X3: 1wt% MgO + 1wt% Ag2O + 0.05wt% SnO2; X4: 1wt% MgO + 1wt% Ag2O + 0.05wt% B2O3; X5: 1wt% MgO + 1wt% Ag2O + 0.05wt% Li2O; X6: 1wt% MgO + 1wt% Ag2O + 0.05wt% La2O3) were prepared by sintering at 837°C for 120 h after partial-melting at 850°C for 1 h. The B2O3 mix-doped tape (X4) and the Li2O mix-doped tape (X5) shows lower conversion of Bi-2212 phase to Bi-2223 phase and lower J
c value than the un-doped tape (X1). The MgO and Ag2O mix-doped tape (X2) shows the same conversion of Bi-2212 phase to Bi-2223 phase as the un-doped tape (X1), but higher J
c value than the un-doped tape (X1). The SnO2 mix-doped tape (X3) and the La2O3 mix-doped tape (X6) show higher conversion of Bi-2212 phase to Bi-2223 phase and higher J
c value than the un-doped tape (X1). However, the La2O3 mix-doped tape (X6) shows the highest proportion of Bi-2223 phase and the highest critical current density. It is suggested that the critical current density depends on the flux pinning and the conversion of Bi-2212 phase to Bi-2223 phase. The MgO doping can increase J
c due to improving the flux pinning, and the SnO2 mix-doping and La2O3 mix-doping can increase J
c due to increase the conversion of Bi-2212 phase to Bi-2223 phase.
Fabrication of YBa2Cu3O
y
coated conductor by Vapor-Liquid-Solid growth technique using a Reel-to-Reel system
Authors: Yasuda Kento , Ito Tomohiro , Tsuchiya Yuji , Ichino Yusuke , Ichinose Ataru , Yoshida Yutaka 
Published: August 2020

Abstract
To optimize the production cost of REBCO-coated conductors, the deposition rate needs to be increased. The vapour-liquid-solid (VLS) growth technique is a suitable method for fabricating a film with a high deposition rate and good crystal orientation. This technique enables growth through a liquid phase. There have been studies conducted on the fabrication of REBCO films using the VLS growth technique. However, very few studies have been performed on a system for depositing REBCO-coated conductors with VLS growth techniques while moving the substrate. In this study, we evaluate the reel-to-reel pulsed laser deposition system, pure YBCO-coated conductors, and the BHO 3 vol% doped YBCO-coated conductors, which were fabricated using the VLS growth technique under high-speed deposition conditions with an average deposition rate of 17 nm/s, achieved J
c > 2.0 MA/cm2, J
c > 1.0 MA/cm2 at 77 K and self-field, respectively. In addition, the J
c in the magnetic fields of the BaHfO3-doped YBCO coated conductors could be improved by introducing discontinuous BHO nanorods.
Influence of Mechanical Cutting Methods on Critical Current of 1 mm HTS Tapes
Authors: She M X , Wang H , Wang L B , Li Z Y , Hong Z Y , Yao L P 
Published: August 2020

Abstract
Over the past decade, the critical current of the tape with 4 mm width exceeds 200 A. Due to the high critical current, the narrowing process to 1 mm width for the HTS tape becomes a feasible technology, and the value of critical current for the 1 mm tape is able to above 50 A. In this paper, critical current loss of 1 mm HTS tape was observed after the mechanical narrowing process. This significantly affects the properties of the 1 mm HTS tape. To understand the influence of narrowing process on critical current, we proposed mechanical cutting methods to manufacture the 1 mm tapes. Meanwhile, the solder plating process was also considered in the manufacturing process of 1 mm tape. The critical current measurements were carried out in order to study the loss of critical current. The detailed results about the critical current measurement experiment, the microscope observation experiment, and the solder plating process were presented and discussed in this study.
Deposition of thick superconducting YBCO films using the surface laser heating
Authors: Matsuzaka J , Tsuchiya Y , Ichino Y , Yoshida Y 
Published: August 2020

Abstract
Cost reduction of REBa2Cu3O
y
(REBCO) coated conductors (CCs) is of interest in the recent applications. To improve the production speed of REBCO CCs is one solution to reduce costs. The larger I
c with the thick REBCO layer is one solution to improve the production speed because the amount of REBCO CCs required for applications reduces. It is important that the deposition of the REBCO layer at a sufficiently high temperature for thick film. Therefore, various heating methods have been studied. In this study, we combined the conventional resistance heating with the laser heating to the surface of the CCs by using an infrared CW laser. As results, the a-axis oriented grains were suppressed with the laser heating. Furthermore, we have achieved I
c values of up to 1500 A/cm-width at 77K and under a self-field in the YBCO films with a thickness of 8 µm.
Towards Understanding the Temperature and Current Sensitivities of Transition-Edge Sensors
Authors: Zhou Yu 
Published: August 2020

Abstract
The transition-edge sensor (TES) technology is widely applied to X-ray spectroscopy or imaging applications at wavelengths ranging from infrared to sub-mm, with the aim of potentially achieving unprecedented spectral resolution and detection sensitivity. As a critical component of the X-ray microcalorimeter, the TES affects the energy resolution via two main parameters: temperature sensitivity and current sensitivity. Tremendous efforts have been made to fabricate TESs with high temperature sensitivity and low current sensitivity, in order to enhance the energy resolution of the microcalorimeters. However, since the resistance of TESs is a complex function of temperature, current, and magnetic field, it is difficult to optimize the operational point of the detector from the first principle. We conducted an experiment to map the parameter space of a sample of MoAu TESs in the transition phase. The results show that the current sensitivity depends only on the resistance of the TESs, which is in line with the two-fluid model. The figure of merit of energy resolution dependence on the quasiparticle diffusion length has been compared with the prediction of the two-fluid model, which indicates that the time-averaging critical current of phase-slip centers is not a constant throughout the superconducting transition. The magnetic field could potentially enhance the energy resolution by reducing the charge imbalance relaxation time.
Development of embedded STJ for large format array X-ray detector
Authors: Ito Y , Aoyagi M , Otani C , Naruse M , Myoren H , Taino T 
Published: August 2020

Abstract
We have been developing an embedded superconducting tunnel junction (e-STJ) for a large-format array X-ray detector. Compared with the conventional STJ array, the e-STJ array is suitable for enlarging the detection area effectively because the e-STJ detector utilizes a three-dimensional packaging technology. To investigate the relationship between the fabrication method and the electric characteristics of the e-STJ, we designed and fabricated three types of simplified e-STJ and measured their subgap leakage current in the temperature range from 4.2 K to 0.3 K. We found that the roughness of the embedding hole on the Si substrate and the contact part between the embedded STJ and the side of the embedding hole affected the subgap leakage current.
Performance of Digital SQUID with Sub-Flux Quantum Feedback Resolution Fabricated using 10 kA/cm2 Nb Process
Authors: Itagaki Kohki , Oshima Itta , Hasegawa Yuichi , Matsunawa Ryo , Naruse Masato , Taino Tohru , Myoren Hiroaki 
Published: August 2020

Abstract
Digital superconducting quantum interference device (SQUID with Single Flux Quantum (SFQ) feedback operates as a Δ-type oversampling A/D converter. Magnetic flux resolution at Nyquist frequency can be improved by taking sub SFQ feedback resolution and large oversampling ratio. Using high critical current density Nb process for fabricating SFQ circuits, we expected more higher operation speed for the digital SQUID and resulting to higher magnetic flux resolutions. We expected a performance of the digital SQUID magnetometer fabricated using 10 kA/cm2 Nb process based on CAD layout, with an up/down counter using T2FF cells and parallel SFQ feedback. For the clock frequency of 13 GHz and the Nyquist frequency of 1.587 MHz, the magnetic field noise was lower than

1.5

fT

/

Hz

and the slew rate was exceeded 500 mT/s.
Implementation of Interface Circuit for Digital SQUID with Sub-Flux Quantum Feedback Resolution
Authors: Matsunawa Ryo , Itagaki Kohki , Oshima Itta , Hasegawa Yuichi , Naruse Masato , Taino Tohru , Myoren Hiroaki 
Published: August 2020

Abstract
Digital SQUIDs with single flux quantum (SFQ) feedback have attracted much attention because of the feasibility of realizing a wide dynamic range and high slew rate for digital magnetometers. To achieve a higher resolution, we studied a digital SQUID with sub-flux quantum feedback. We studied implementation methods for an interface circuit by considering the circuit size, power consumption and signal processing to achieve high-resolution and highspeed operation of the digital SQUID magnetometer. Assuming the decimation filter and the up/down counter implemented on a FPGA board, a 1-bit to 16-bit deserializer with an output frequency of 500 MHz could be used for the interface circuit. The circuit scale was 1940 µm × 1720 µm, and the bias current was 302 mA. From the simulation results, a sufficient wide bias margin could be obtained up to 30 GHz.
Logic simulation tool for RSFQ circuits accepting arrivals of multiple pulses in a clock period
Authors: Kito Nobutaka , Udatsu Shohei , Takagi Kazuyoshi 
Published: August 2020

Abstract
A logic simulation tool for RSFQ circuits is proposed. It can treat RSFQ logic circuits containing signal lines accepting multiple pulses in a clock period. Logic circuits can be implemented in compact area by utilizing RSFQ specific gates and feeding multiple pulses into a gate input in a clock period. For treating circuits containing signal lines accepting multiple pulses in a clock period, a new description method is proposed. A logic simulation tool treating netlists described based on the proposed method was implemented. Examples of designs having signal lines accepting multiple pulses to be implemented in compact area are shown, and simulation results obtained with the tool are shown.
Design and error-rate evaluation of RSFQ logic gates comprising a toggle storage loop
Authors: Yamazaki Koki , Shimada Hiroshi , Mizugaki Yoshinao 
Published: August 2020

Abstract
We propose an RSFQ digital cell with a toggle storage loop structure for logical NOT operation. Logical NOT operation is a fundamental function of digital circuitry, and hence, it had better be realized with less devices. We demonstrate a simpler and area-halved NOT gate designed as a 40 x 80 μm2 cell, which follows to cell-based design methodology. Test circuits were fabricated using a 2.5kA/cm2 Nb integration process. Measurements were executed in a liquid helium bath. We confirmed that the NOT gate comprising a toggle storage loop worked correctly. The error-rate of the NOT gate was less than 8.33 x 10−6 in the bias voltage range from 2.111 to 3.165 mV, which corresponded to the bias margin from 84.4% to 126.6% of the nominal bias voltage (2.5 mV). We also present that NOR and NAND logic gates can be configured using a toggle storage loop.
A Study of the HTS Josephson Junction Formed by a Ga Focused Ion Beam
Authors: Hayashi K , Ueda T , Ohtani R , Ariyoshi S , Tanaka S 
Published: August 2020

Abstract
High Temperature Superconductor Josephson Junctions (HTS-JJs) are based on artificial grain boundaries. However, the layout of HTS Superconducting QUantum Interference Devices (SQUIDs) on a bi-crystal substrate was restricted. Therefore, we considered to form low noise nano-bridge JJs by Ga Focused Ion Beam (Ga-FIB) irradiation. An 100 nm thick and 4 μm wide YBa2Cu3O7-δ
(YBCO) micro-channels protected by a 20 nm thick Au protection layer were irradiated by line scans of Ga-FIB (Acceleration voltage: 40 kV, Beam diameter: ∼30 nm) and they were became normal conductivity except for the restricted region. In those nano-bridges, W
N = 500 nm and fluence Φ = 2.0×1015 ions/cm2 of the nano-bridge was I
C = 170 μA and we confirmed Shapiro steps by microwave irradiation of f
RF = 2 GHz.
Estimation of Electricity Storage Density of Compact SMESs Composed of Si-wafer Stacks Loaded with Superconducting Thin Film Coils in Spiral Trenches under the Constraints of the Critical Magnetic Flux Density
Authors: Motohiro T , Sasaki M , Noh J-H , Takai O , Honma H 
Published: August 2020

Abstract
Numerical estimations of electricity storage volume density: W for a proposed compact superconducting magnetic energy storage system composed of 4 stacks of 20 to 1800 Si-wafers loaded with superconducting YBa2Cu3O7-δ thin film coils in spiral trenches formed by MEMS process were performed in conjunction with estimations of magnetic flux density and electromagnetic hoop stress applied to the coil. Changing the design parameters such as trench depth, trench width, trench wall thickness, number of stacked Si wafers, the inner-radius of the spiral coil under the fixed outer-radius of 47.45 mm, the maximum W was obtained to be 13.6 Wh/l under the constraint of the maximum magnetic flux density applied to the coil: Bmax
< 20 T. The maximum hoop stress applied to the coil was estimated to be much lower than the mechanical strength limit of the Si wafer :4 GPa, indicating that other substrate materials such as typical engineering ceramics can be used in place of Si wafer if microfabrication of spiral trenches is feasible.
Effectiveness of Filter Inductor of Rectifier Transformer Flux Pump in Energizing Multi-Stacked No-Insulation REBCO Pancake Coils
Authors: Mato Takanobu , Kurauchi Thomas , Noguchi So 
Published: August 2020

Abstract
In recent years, strong magnetic field rare-earth barium copper oxide (REBCO) magnets are desired for various applications. For such magnets, since heat penetrating from current leads is undesirable, a flux pump is an attractive method to energize. However, it is difficult to apply a flux pump to a REBCO coil using no-insulation (NI) winding technique. Because, a large current flows into the radial direction due to a low contact resistance. Recently, a filter inductor installed into a rectifier transformer type flux pump (RTTFP) was proposed to effectively charge an NI REBCO single pancake coil. However, it is not sure whether it also works for multi-stacked NI REBCO pancake coils. Hence, we investigate the role of a filter inductor by a numerical simulation, and then we clarify the validity of filter inductor. As the result, the filter inductor accelerates the charging of multi-stacked NI REBCO pancake coils with low contact resistance.
Numerical simulation of a hybrid trapped field magnet lens (HTFML) magnetized by pulsed fields
Authors: Shinden Motoki , Namba Sora , Hirano Tatsuya , Fujishiro Hiroyuki , Naito Tomoyuki , Ainslie Mark D 
Published: August 2020

Abstract
The hybrid trapped field magnet lens (HTFML) is a promising device that is able to concentrate a magnetic field higher than an applied background field continuously, even after removing a background field, which was conceptually proposed by the authors in 2018. We have numerically investigated the HTFML performance, consisting of a REBaCuO cylindrical magnetic lens and REBaCuO trapped field magnet (TFM) cylinder, magnetized by pulsed fields. Single magnetic pulses were applied ranging from B
app = 1.5 T to 5.0 T at the operating temperature of T
s = 30, 40 and 50 K, and the performance was compared with that of the single REBaCuO TFM cylinder. The HTFML effect was clearly confirmed for the lower B
app values. However, for the higher B
app values, the trapped field in the magnetic lens bore was nearly equal to or slightly lower than that for the single TFM cylinder because of a weakened lens effect due to magnetic flux penetration into the lens. A temperature rise in the REBaCuO magnetic lens and TFM cylinder was also observed. These results strongly suggest that lowering the temperature of the REBaCuO magnetic lens could enhance the HTFML effect even for higher B
app.
Superconducting motors for aircraft propulsion: the Advanced Superconducting Motor Experimental Demonstrator project
Authors: Grilli Francesco , Benkel Tara , Hänisch Jens , Lao Mayraluna , Reis Thomas , Berberich Eva , Wolfstädter Simon , Schneider Christian , Miller Paul , Palmer Chloe , Glowacki Bartek , Climente-Alarcon Vicente , Smara Anis , Tomkow Lukasz , Teigelkötter Johannes , Stock Alexander , Büdel Johannes , Jeunesse Loïc , Staempflin Martin , Delautre Guillaume , Zimmermann Baptiste , Woude Ruud van der , Perez Ana , Samoilenkov Sergey , Molodyk Alexander , Pardo Enric , Kapolka Milan , Li Shuo , Dadhich Anang 
Published: August 2020

Abstract
The European Union-funded Advanced Superconducting Motor Experimental Demonstrator (ASuMED) project started in May 2017 with the purpose of demonstrating the benefits of a new, fully superconducting motor for reaching the targets established by the Flightpath 2050 plan. The project aims at a motor power density of 20kW kg−1 using a high-temperature superconducting (HTS) stator. The rotor will use HTS stacks operating like permanent magnets. A highly efficient cryostat for the motor combined with an integrated cryogenic cooling system and associated power converter will be used. This article provides a general overview of the prototype that is currently being assembled and that will be tested soon.
Test of a Flux Modulation Superconducting Machine for Aircraft
Authors: Colle A , Lubin T. , Ayat S. , Gosselin O. , Leveque J. 
Published: August 2020

Abstract
The increasing of drives towards More Electric Aircraft (MEA) or the development of electric propulsion aircraft calls for MW-class electrical machines with more compact and power dense designs. One way is to explore the use of superconducting (SC) materials to create a high magnetic field in order to reduce the mass of ferromagnetic components. This paper presents the design and the test of a brushless axial flux superconducting machine. The brushless topology satisfies the aeronautics industry requirements in terms of maintenance, while the axial configuration ensures an optimal use of the anisotropic HTS tapes. The machine is classed as partially superconducting, only the inductor is made with superconducting materials. A 50kW prototype is manufactured with a minimal mass objective. The prototype constitutes a first step to a scale-up MW-class machine design.