bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of non-magnetic rare earth substitution for A site in mixed anion APX superconductors
Authors: Kitô H , Kawashima K , Ishida S , Oka K , Fujihisa H , Gotoh Y , Iyo A , Ogino H , Eisaki H , Yoshida Y
Published: August 2020

We report the improvement of superconducting transition temperature (T
c) by nonmagnetic rare earth atom substitution for A site in APX-based Zr(P, S)2, Hf(P, Se)2 and Hf(P, S)2 superconductors. The partial non-magnetic rare earth Lu atom substitution at Zr site of ZrPS, as opposed to the case of Zr(P, Se)2, shows that lattice constants a and c decrease monotonically with increasing nominal substitution y. It is shown that the maximum T
c for ZrPS was increased from 3.70 K to 6.36 K. In HfP1.55Se0.45, when Hf site is partially substituted with Lu atoms (or Y atoms), lattice constant a shrinks and c expands monotonically with increasing nominal rare earth substitution y. T
c was also increased from 4.88 K to 5.89 K. In HfP1.45S0.55, when Hf site is partially substituted with Lu atoms (or Y atoms), lattice constant a shrinks slightly and c expands monotonically with increasing y. T
c was also increased from 3.16 K to 5.86 K. In this paper, the doping behaviour by partial substitution and the increase of T
c is discussed.
Electronic Structure of Novel Superconductor doped-ZrPSe
Authors: Hase I , Yanagisawa T , Kito H. , Iwakiri K. , Nishio T. , Fujihisa H , Gotoh Y , Eisaki H , Kawashima K
Published: August 2020

In this paper we report the results of the first-principles calculations for cation and anion co-doped system (Zr1-yYy)P(As0.25Se0.75) using virtual crystal approximation. The density of states at the Fermi level (=D(EF)) shows a dome-shape with respect to the doping concentration y. This result qualitatively explains the observed y dependence of T
c, especially for (Zr1-yYy)P1.25Se0.75. We also found the similarity of the band structure between ZrSiS and doped-ZrPSe. Characteristic band crossing near E-g, which is found to be the Dirac line node in ZrSiS, is also found in doped-ZrPSe. This result strongly suggests that the superconductivity and the Dirac line node are co-existed in doped-ZrPSe.
Fermion zero-energy modes and fractional fermion numbers in a fractional vortex-fermion model
Authors: Yanagisawa Takashi
Published: August 2020

Topological materials have attracted much attention from both physicists and mathematicians recently. Topological properties are closely related to the fermion number (index) of Dirac fermions. The fermion number is given by the η invariant introduced by Atiyah, Padoti and Singer. We discuss a system of Dirac fermions interacting with a vortex and a kink. This system will be realized as a layered material of superconductors and topological insulators, where the Dirac fermion exists on the surface of the topological insulator. The fermion number is fractionalized and the fermion zero-energy excitation mode emerges when Dirac fermions interact with vortices and kinks. Our discussion includes the case where there is a half-flux quantum vortex associated with a kink in a magnetic field in a bilayer superconductor. A normalizable single-valued fermion zero-energy mode does not exist in the core of the half-flux quantum vortex.
The search for the new superconductors in the Ni-N system
Authors: Gavryushkin P N , Sagatov N , Sagatova D , Banaev M V , Donskikh K G , Litasov K D
Published: August 2020

Transition metal nitrides show a unique combination of superconducting and mechanical properties. In this study we perform a theoretical search of the intermediate compounds in Ni-N system, determine their superconducting transition temperatures (Tc
) and bulk moduli (K
0) in the wide range of pressures, from 0 to 300 GPa. We have revealed several nickel-rich interstitial compounds, Ni5N2, Ni3N, and Ni6N, and one nitrogen-rich compound, NiN2, as stable structures. At pressures above 100 GPa, previously unknown NiN with anti-nickeline structure is also stabilized. All found compounds are non-magnetic. The most promising for superconductivity NiN2 structure is stable against decomposition on the mixture of (Ni+N) from 3 to at least 300 GPa. The transition from marcasite-type NiN2-Pnnm to pyrite-type NiN2-

P
a

3
¯

occurs at 70 GPa. NiN2-Pnnm is an insulator with the band gap of about 1 eV, while NiN2-

P
a

3
¯

is a metallic phase. The calculated Tc
of NiN2-Pnnm equals to 10−2 K, and the bulk modulus (K
0) equals to 225 GPa at 10 GPa, which is in excellent agreement with available experimental data. The comparison of Tc
of compounds in the Ni-H and Ni-N systems with that of the Fe-H and Fe-N compounds, shows that hydrides and nitrides of nickel have lower Tc
than hydrides and nitrides of iron, which is explained by the significant differences in crystal structures.
Effects of Splayed Columnar Defects on Critical Current Density in CaKFe4As4
Authors: Takahashi A , Pyon S , Kobayashi Y , Kambara T , Yoshida A , Okayasu S , Ichinose A , Tamegai T
Published: August 2020

Introduction of columnar defects to superconductors through particle irradiation enhances their critical current density (J
c) . Further enhancement of J
c by dispersing the direction of columnar defects has been confirmed. Moreover, in such systems with splayed columnar defects, an anomalous peak effect in J
c at a certain magnetic field determined by the irradiation dose accompanied by the in-plane anisotropy of J
c between those parallel and perpendicular to the splay direction were observed. We introduce splayed columnar defects to CaKFe4As4 single crystals, which was recently found as a new type of iron-based superconductors (1144-type IBS), by irradiating 2.6 GeV U and 320 MeV Au ions and measure their J
c properties.
Insulator-to-superconductor transition by exciting half-filled d-wave pairing state beyond Mott gap
Authors: Yokoyama Hisatoshi , Kobayashi Kenji , Watanabe Tsutomu , Ogata Masao
Published: August 2020

In connection with recent tera-Hertz photoexcitation experiments in which strongly correlated materials are changed from Mott-insulating to metallic, we statically study the properties of excited states beyond the Mott gap in the

d

x
2

−

y
2

-wave superconducting (d-SC) branch at half filling, by applying a variational Monte Carlo method to a two-dimensional Hubbard model. It is found that the first-order Mott transition previously found at U = U
c for the lowest-energy state vanishes for the excited states. As a result, an insulator-to-d-SC transition occurs as the strength of excitation (corresponding to light intensity) is increased for U/t (> U
c
/t) fixed. As a mechanism, this conduction is led by newly created free carriers (unbound doublons and holons) in the excited states.
Possibility of Pomeranchuk instability in staggered flux state
Authors: Kobayashi Kenji , Yokoyama Hisatoshi
Published: August 2020

In connection with the symmetry-breaking phenomena found in cuprate superconductors, the instability toward x−y and (x + y)−(x − y) anisotropy (Pomeranchuk instability) is studied for a strongly correlated Hubbard model (U/t = 12) on a square lattice with the next-nearest-neighbor transfer t′ using a variational Monte Carlo method. As a variational function, a staggered flux state ΨSF is considered, which is a candidate for the pseudogap state in cuprates. ΨSF is stabilized in a underdoped regime and reduced to the normal state (projected Fermi sea) for larger doping area. By analyzing ΨSF for t′/t = 0, ±0.3, we argue that the appearance of Pomeranchuk instability is limited to the normal state with t′/t = 0 and

0.08
≤
δ
≤
0.20

(σ: doping rate) in the x−y anisotropy. Band-renormalization effects (Fermi-surface modification) owing to strong correlations play a crucial role for the argument.
Simulation of THz oscillations in an intrinsic Josephson junction array
Authors: Fujiki Yusuke , Kato Masaru
Published: August 2020

When a voltage is applied to coupled Josephson junctions, an ac current flows because of the Josephson effect. Due to this ac current, an electromagnetic (EM) wave is emitted from junctions. For the cuprate High-Tc superconductor, frequency of the EM wave reaches to the THz regime since the energy gap is large. In order to simulate the EM wave in the superconductors, we solve the Josephson junction relations and the Maxwell equations simultaneously. Especially, we consider coupling of junctions including capacitive and inductive couplings, and spatial variations of phase differences of order parameters inside of junctions. We shows time developments of distributions of the phase differences, magnetic and electric fields in junctions in the transient state.
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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Electromagnetic analysis of fully superconducting motor for electric aircraft
Authors: Voccio John , Voccio Quinn
Published: August 2020

In order to reduce carbon emissions, there is considerable interest in all-electric aircraft for transportation. Fully superconductor motors will be required to meet the high specific weight requirements, which are >10 kW/kg for the NASA N3-X plane. This paper summarizes the results of electromagnetic analysis generated using the FEMM magnetics code, along with the Lua scripting language, to determine the optimum motor configuration for a 4 MW, 3000 rpm fan motor. In considering ac loss, the analysis assumes Bi-2212 stator windings and both iron-tooth and air-core designs are considered. The best selected case consists of an 8-pole configuration utilizing an armature current density of 100 A/mm2.
Simplex optimization of shield coil geometry for increasing magnetic shielding performance of air-core superconducting generator
Authors: Oh J M , Bang T K , Jang G H , Lee J I , Haran K S , Cho H W
Published: August 2020

This study deals with the simplex optimization of a shield coil geometry for improving the magnetic shielding performance of fully air-cored superconducting generators. The superconducting generator in this study has a 10 MW-3000 rpm class, fully air-cored, rotating armature structure designed for electric propulsion aircraft applications. The magnetic flux radiated to the outside of the machine is shielded by the shield coil, and the shielding performance is determined by the shape of the shield coil. In this study, the design of the shield coil is developed using simplex optimization to improve the shield performance. The shape optimization is conducted using the simplex optimal design method, and the validity of the designed shield coil is verified by comparing the shielding performance of the initial and the optimized models.
Estimation of Machine Parameters in Superconducting Transformer using Differential Evolution
Authors: Yonenaka T , Muraoka T , Ichiki Y , Otabe E S , Tokunaga Y
Published: August 2020

To analyze the inrush current in a superconducting transformer, the machine parameters for the transformer were estimated from the measured current using a search algorithm. To address the large rising edge error in estimations performed using a genetic algorithm (GA), a differential evolution (DE) was used in this study. As a result, the estimated time was reduced to about 1/10 that obtained with GA, and the evaluation value indicating the difference between the measured value and the estimated value was reduced to about 1/2. Thus, it was possible to estimate with higher accuracy by using DE.
An approach to development of the HTS magnet for SMES at JINR
Authors: Khodzhibagiyan H , Drobin V , Dorofeev G , Karpinskiy V , Shurygin A , Novikov M , Kashaev D , Zaslavskiy M , Kachlishvili G
Published: August 2020

Particle accelerator complex NICA (Nuclotron-based Ion Collider fAcility) comprises superconducting Booster and Nuclotron synchrotrons which magnets operating at pulse mode in opposite phase with period of about 4 seconds. Summary stored energy of Booster and Nuclotron magnets will vary from 1 to 2.6 MJ during the period. NICA power supply system can be significantly improved by Superconducting Magnetic Energy Storage (SMES) application that will help to move the energy back and force between Booster and Nuclotron. The useful energy at this SMES must be about 1.6 MJ so the maximum total SMES energy should be 3-5 MJ. SMES with this energy should have several Tesla magnetic fields to keep a reasonable size. SMES operating current can be not less than Booster and Nuclotron magnets current so it might be 10-12 kA. It is better to make such a SMES magnet from an HTS (high temperature superconductor) cable for the stability at 6-7 T and 4 s pulse mode. The SMES magnet is planned to be wound as a short solenoid (Brooks coil) of cables optimized for several coaxial sections. HTS cables with helical structure similar to well-known CORC (conductors on round core) cables are under the development at JINR. The HTS cabling technology is based on the same principle as Nuclotron type cable manufacturing technology. HTS tapes, cables and magnets experimental study and testing methods are being developed on the base of an existing test facility at LHEP. First HTS cable short sample with 6 HTS tapes was prepared and tested at 77 K in self-field. Its critical current is about 800 A that will allow achieve required operating currents of SMES magnet with a reasonable amount of HTS tapes in cables. Developments of high field high current fast cycling HTS magnets for accelerators are also being planned at JINR.
Theoretical and experimental investigation of R&W and W&R SMES coils wound with large-scale MgB2 Rutherford cables operated around liquid hydrogen temperature
Authors: Hira M , Yagai T , Takao T , Shintomi T , Makida Y , Hirano N , Komagome T , Tsukada K , Onji T , Arai Y , Ishihara A , Tomita M , Miyagi D , Tsuda M , Hamajima T
Published: August 2020

We have developed the system called Advanced Superconducting Power Conditioning System (ASPCS) composed of a Superconducting Magnetic Energy Storage (SMES), a fuel cell and a water electrolyzer for effective use of renewable energy such as wind and solar power generation. We have been investigating about the SMES coil using the large-scale Rutherford-type conductors made of commercially-available MgB2 wires. Due to strain sensitivity even before heat treatment for MgB2 production, the design for large-scale Rutherford cables both in the wind and react (W&R) method, and the react and wind (R&W) method applied to coil fabrication has to be done cautiously to prevent the degradation of the IC by the optimizing design parameters such as the twist pitch and the cable compaction. Especially for the R&W method using heat-treated wires, other factors like handling during the coil production process which affect the conductor and coil IC should be also considered. To evaluate the applied strains during the manufacturing process, we conducted theoretical investigation on the strains applied to individual filaments caused by wire-bending. We developed a test coil designed for the R&W method based on analyzing those factors. Furthermore, we measured the coil IC-B-T characteristics and compared to those of other test coils made by the W&R method.
Half-meter Scale Superconducting Magnetic Bearing for Cosmic Microwave Background Polarization Experiments
Authors: Sakurai Yuki , Ashton Peter , Kusaka Akito , Hill Charles A. , Kiuchi Kenji , Katayama Nobuhiko , Tajima Osamu
Published: August 2020

We report the development of a large-diameter superconducting magnetic bearing (SMB) used in a continuously rotating cryogenic half-wave plate (HWP) polarization modulator for cosmic microwave background (CMB) polarization experiments. A precise measurement of the CMB polarization will place tighter constrains on cosmic inflation, describing the rapid expansion of the early universe. The polarization modulator is a critical instrument for suppressing 1/f contamination, which is mainly caused by atmospheric noise, and for mitigating systematic uncertainties that arise when differencing orthogonal polarization detectors. To ensure a sufficient field of view and to reduce thermal emission, the polarization modulator must have a clear-aperture diameter of > 500 mm and must operate at cryogenic temperatures. We constructed a superconducting magnetic bearing (SMB) with an inner diameter of 550 mm, which is the largest used in any CMB polarization experiment to date. We tested the friction and stiffness of the bearing at liquid nitrogen temperatures. The measured total loss is 0.4 W and the spring constant is >105 N/m, which satisfies typical experimental requirements. Furthermore, we performed a performance test by changing the number of disk-shaped YBCO tiles, and then confirmed that the SMB performance was proportional to the YBCO volume.
Simulation of thrust magnetic bearings for levitation systems
Authors: Anischenko I.V. , Pokrovskii S.V. , Rudnev I.A.
Published: August 2020

This work presents the complex results of the FEM H-formulation modeling of the thrust magnetic bearing based on 2G HTS tapes. The simulated bearing consists of the HTS stator and PMs rotor. In the model we have used the magnetic and transport characteristics of industrial GdBa2Cu3O7-x superconductors and also took into account the thermal properties of each layer of high-temperature superconducting tape and the features of the layered structure of the whole stack. The numerical simulation was performed using the finite element method. The developed model feature is a direct magnetic assembly rotation simulation. Load characteristics and losses in the system at several operating temperatures were obtained. Comparison with the experimental results was done.
The Role of Design Characteristics of the Internal & External Spaces of Campus to Achieve Psychological Stability “Mosul University Campus as Case Study”
Authors: Mohammed Nasma Maan , Mohammed Anfal Azzam
Published: August 2020

The architect plays a great role in influencing the professors and students behavior of the constituent spaces of the architectural form he produces, since the occupation of this space needs to provide his biological, physical and psychological needs, thus positively affecting the performance of the users. The productivity of the individual increases, whether for work for adults or for students. The study dealt with the effect of shaping the architectural form of the buildings in general and the university buildings in particular in achieving psychological stability for professors and students to increase their positive influence and their chances of success as individuals in the society, and discussed the negative effects of these buildings on the professors and students as they design their lives and negative perception of architectural elements, principles and strategies. The researchers conducted some practical experiments regarding the role of each building on the inside of their users in terms of (space capacity or narrowness, high or low ceiling, shape and color of walls and ceiling, straight or curved architectural design lines, The value, as well as the shape and color of the furniture used). This role has been identified by distributing a questionnaire for each of the professors and students about the university building internal and external spaces at the University of Mosul, and collecting the data in special tables and then discussing the results. The architect who design and shape the architectural form of the university buildings must be well thought out as it directly affects (positively or negatively) on both of them of these configurations that he designed.
Hot Mix Asphalt Characteristics with Sugar Industry Waste Materials as Mineral Filler
Authors: Shareef Ranin Abd , Al-Hdabi Abbas
Published: August 2020

Recently, applying of the waste materials as mineral filler in hot asphalt mixture has many advantage for economic and environmental impacts and also used to improve the hot asphalt mixtures characteristics. In this research, sugar industry waste materials has been used as mineral filler to investigate the achievable prospects to improve hot asphalt mixture properties. The aim of this study is to evaluate the effect of adding Sugar Waste (SW) materials on the properties of hot mix asphalt in comparison with the State Commission of Roads and Bridges (SCRB, R9) requirements. Two groups of hot asphalt mixtures have been prepared, the first was with the Ordinary Portland Cement (OPC) as mineral filler i.e. (control mixture) and the second was prepared with SW materials (modified mixtures). These mixtures have been assessed based on different experimental tests which were Marshall Stability and Flow, Indirect Tensile Strength (ITS), Index of Retained Strength (IRS) and Long Term Aging (LTA). The results indicate that there is an improvement in the mixture properties; slight increase in Marshall Stability, an improvement in Indirect Tensile Strength, enhanced their Marshall stability after aging when tested in accordance to LTA. Furthermore, the modified mixtures comply with (SCRB, R9).
Finite element analysis of embankments on gypsiferous subgrade soil - stone column strengthened with geogrid
Authors: Mohammed Hadeel Ammar , Afaj Hanan A , Masood Ghadah Ghassan
Published: August 2020

Gypsum and anhydrite rocks are frequently found in numerous countries of the world in extensive deposits, the huge region in middle and west of Iraq is classified as a gypseous soil. Stone columns are non-time dependent foundation technique used to increase the structural stability and to reduce the structural deformations of soil. In the present study, the finite element method is used as a tool to utilized the effect of using stone columns with geogrid as reinforcing material for treatment gypsiferous subgrade soil under embankment during both construction and consolidation conditions. The results show that decreasing the stone column spacing leads to a considerable decrease in the settlement beneath the embankment, especially below the center line, reduction in the settlement of about 60% and when using geosynthetic material the reduction about 75%. Also, increases the excess pore water pressure immediately after the construction of each lift of the embankment and then falls with and without using geosynthetic material. The vertical stress in the gypsiferous subgrade soil increases at a very small rate especially in the early stages and decreases as stone columns spacing decreases.
Effect of longitudinal steel reinforcement ratio on deflection and ductility in reinforced concrete beams
Authors: Mansor Ahmed Abdullah , Mohammed Ahlam Sader , Salman Wissam D
Published: August 2020

This search report is an experimental result on load –deflection relationship of various ratios of longitudinal reinforcement for six simply supported reinforced concrete beams. All specimens’ dimensions are (200×300×1750mm) and they were tested under two-point loading. Concrete compressive strength was (37.0-40.7 MPa). The variables studied in this work were tensile steel ratio (0.46-3.0%), bar diameter (12, 16 and 25mm) and number of bars (2 or 3 bars). It is concluded that for low reinforcement values (ρ < 0.013), an increase in ρ is sharply reduced the ductility index μ

d
. However, this effect decreases with increase in ρ values. All beams exhibit insufficient displacement ductility (less than 3) when reinforced with ρ/ρ

b
> 0.4. The increase in longitudinal steel ratio using 2 bars is more significant than when using 3 bars in yield and ultimate strengths of specimens as well as the deflection values at yield load, but the deflection values have gradual decrease at the ultimate load as a result of ductility decrease. It was concluded that the increase in longitudinal reinforcement ratio causes an increase in yield and ultimate strength of beams, these increments are compatible with the steel ratio i.e. by increasing the ρ by 50% the strength is increased about this ratio. As well as, the decreasing in ductility compatible with increasing the ρ by 50% the ductility decreased in about 50% on average.
The Behavior of Polymer RC Columns Exposed to aggressive Soils
Authors: Rasheed L Sh , Salih Sh A , Hanash Z F
Published: August 2020

One of the most important properties about the durability of concrete is its resistance to sulfate attack. In this search, the effect of sulfate salts on reinforced polymer concrete columns was studied, the columns buried in two types of soil, sand and clay, in depth of 3 m, in one of the agricultural areas in the holy city of Karbala. The sandy soil comprised 10.609% of SO3, the clay soil 2.61%SO3. A compressive test for reinforced concrete columns, compressive test for concrete cubes and a tensile splitting test for concrete cylinders were applied, absorption, voids ratio and density also measured. A ratio of polymer / cement = 7.5% was found to reduce the compressive strength of polymer reinforced concrete columns buried in clay soil at ages 60, 150 and 240 days by 23.97, 20.28 and 24.96%. When buried in sandy soil, the decrease in strength was 31.12, 20.03 and 37.52 % respectively, in comparison to the reference column. From this it can be concluded that the use of a polymer (SBR) has negatively affected the strength of reinforced concrete columns after 150 days so is not recommended for use in concrete facilities which are subject to attack by sulfate salts.