Superconducting Wires Research Articles

Additively Manufactured Polymer Composites for Superconducting Motor Coil Structures

The Robinson Research Institute at Victoria University Wellington is building a series of superconducting motors over the next six years to demonstrate technology pathways for the transport industry, including aviation. Our target topology for these machines uses rotor-mounted superconducting field coils and a superconducting stator in an air-core configuration. To avoid eddy current heating in the stator cryostat, electrically conductive materials must be eliminated. At the same time, heat generated due to AC losses in the stator must be transferred efficiently and evenly from the superconductor to the cryo-coolant, in order to avoid localised film boiling. And finally, the coil structural support needs to closely match the thermal expansion characteristics of the superconductor wires and likely other G10 structural pieces to avoid debilitating stresses and lost support. In this study, we investigated the opportunity to use additively manufactured (AM) polymers with a range of filler materials as the structural support for a motor coil. A range of commercially available candidate materials have been identified and test coupons manufactured using either Selective Laser Sintering (SLS) or Fused Deposition Modelling (FDM). The material properties of the test coupons have been measured from room temperature down to cryogenic temperatures. This data was used to design, analyse and manufacture the support structure for a stator saddle-coil, and the coil wound with aluminium wire to simulate Conductor on Round Core (CORC) cable. Initial thermal cycle testing has been carried out to assess the performance of the composite.

Limitation of Current Transport in Coated Conductors: Statistical Fluctuations or Weak Spots?

Traditionally, the critical current, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_c</i> , of a superconducting wire, considered as the limit of DC operation, is experimentally verified on a sample few centimeters long. This approach could fail in case of high-temperature superconductor wires, where significant changes of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_c</i> along the conductor length, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> , are commonly observed. Then, the quantity that could replace the uniform critical current as the entry data in designing of a superconducting device is to be found. We have analysed the properties of 6 coated conductor tapes provided by 4 different manufacturers. First, the overall critical current of the full tape length, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_c_,ovrl</i> , has been evaluated from the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_c(x</i> ) data. However, the dissipation in a non-uniform conductor with fluctuating critical current concentrates in the “weak spots” with the lowest <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_c</i> values. Then, depending on the conditions of heat removal, thermal runaway in some location could happen before reaching <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_c_,ovrl</i> during conductor testing or operation. Taking into account the conductor architectures and assuming the cooling in liquid nitrogen bath, we computed the thermal runaway current, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_tr</i> , at which the weakest location in each of the analysed conductors would convert to a “hot spot” with rapid increase of temperature. Then, comparing <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_tr</i> to <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_c_,ovrl</i> one can identify which of these two values is lower, i.e., represents the upper limit of transportable current. We discuss how the result of such analysis would be influenced by a metallic stabilisation that exhibits significant impact on cooling.

High-Temperature Superconducting Undulator Prototype Coils for Compact Free-Electron Lasers

Short-period and high-field undulators are crucial for the production of coherent light up to X-rays in compact free-electron lasers (FELs). Besides, future colliders like CLIC or FCC-ee demand high-field damping wigglers to reach a low beam emittance. Both applications may benefit from the use of high-temperature superconductors (HTS), e.g. by providing high magnetic field amplitudes or higher operating temperatures. This paper presents and summarizes our HTS undulator prototype coils, designed and manufactured at CERN, made from coated REBCO tape superconductor. The coil design, described and already powered at 77K in previous works, is based on no-insulation (NI) vertical racetracks with a period length of 13 mm, assembled with iron poles. Powering tests of several HTS undulator prototype coils at 4.2 K, performed at KIT, revealed safe operations at high engineering current densities of 2.3 kA/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with produced magnetic fields of up to 1.5 T at 3.5mm distance from the magnetic iron poles. Reasonable effective time constants of around 100 s were obtained and further powering tests in regions beyond <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J</i> c with 3.6 kA/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> showed the stability of our NI design and created magnetic fields in the region of 2 T.

High transport Jc in 7-filament Cu/Ag sheathed Ba0.6K0.4Fe2As2 tapes manufactured by ambient pressure sintering

In regard to iron-based superconductors (IBS), the multi-filament Cu/Ag composite sheathed Ba-122 tape is particularly attractive for industrial high-field applications owing to its prominent properties. By a cost-effective and scalable way, ambient pressure sintering, a high transport critical current density (Jc) of 7-filament Cu/Ag sheathed Ba-122 tapes reached 4.5 × 104 A cm−2 at 4.2 K and 10 T, whose corresponding engineering critical current density (Je) has achieved to 104 A cm−2. An optimized powder-in-tube (PIT) method was adopted aiming at overcoming the difficulty of ambient pressure sintering to obtain high-density superconducting core and grain alignment. Improvements in the manufacturing process, such as drawing without intermediate annealing and rolling from larger initial diameter to thinner tapes, have resulted in high grain connectivity and good c-axis texture, which are the major factors contributing to high Jc. Our results demonstrate that the ambient pressure sintering process is a viable method to fabricate long-length multifilamentary Cu/Ag composite sheathed IBS tapes with high Jc for practical high-field applications.

A novel method incorporating large rock fragments for improved soil bulk density and carbon stock estimation

AbstractSoil bulk density (BD) is a principal component in estimating the density of soil nutrients and elements including carbon (C). Current literature states that in soils with rock fragment (RF) content ≥3% of the total sample volume, substantial differences in estimated soil organic carbon density (SOCD) are found, depending on the soil BD calculation method chosen, potentially affecting the accuracy of soil nutrient and C inventories. In many soil surveys, soil BD is not measured directly, or the core method is used as the sole determinant of soil BD, potentially neglecting the soil volume dilution effect of RFs larger than the diameter of the cores used. This study uses the core and quantitative pit methods at 10 forest sites in Ireland to determine the BD and RF mass and volume to a depth of 40 cm. The authors examine how large RFs impact BD and subsequently affect the estimated SOCD values by comparing against reference values from established soil sampling and BD calculation methods. The analysis reveals significant variations in the estimated SOCD values when the RF volume in the soil sample exceeds 8% of the total sample volume. A novel method, hereafter named “core‐scaling,” combines core and pit sampling methods to account for large RF mass and volume in BD calculations. This study suggests that using the core‐scaling method provides results that are strongly correlated with the pit method, thus offering an alternative that can also provide accurate SOCD estimates in soils with a high RF content.

Numerical simulation of mechanical behaviors and intergranular fracture of polycrystalline Nb3Sn and superconducting filaments

Given the importance of large-scale engineering applications of the superconducting compound Nb3Sn, both its use and performance under certain operating conditions have attracted the interest of applied superconductivity researchers and material scientists for several years now. Huge efforts are directed toward understanding the response to applied loads and predicting fracture damage within their internal microstructure; this is fundamental in the design of superconducting coils and magnets which must meet stringent requirements in terms of maximum thermal and electromagnetic loads. In this paper, the fracture behaviors in polycrystalline Nb3Sn and Nb3Sn filaments with composite structures are investigated using the micromechanical finite element (FE) models with Voronoi tessellation. First, the 2D and 3D Voronoi FE models of the polycrystalline Nb3Sn tensile tests are developed and validated to provide insight into the cracking behavior in the intergranular brittle fracture of polycrystalline Nb3Sn. A cohesive zone model is used to simulate crack propagation at the grain level model including grain boundary zones. It is found that the pre-existing cracks of polycrystals and martensitic phase transformation of grains significantly impact the fracture properties in polycrystalline Nb3Sn. Second, detailed FE models of powder-in-tube (PIT) and bronze route filaments with Voronoi structures for fracture analysis are then developed on the basis of experimental observations of sectional morphologies. The mechanism of crack initiation and propagation under tensile load have been investigated by analyzing the mechanical properties of each component and the characteristics of multi-scale composite structures of filaments. Furthermore, the damage situation is investigated in PIT filaments undergoing transverse compressive load. The proposed simulation method in this paper can be extended to the fracture and damage analysis of Nb3Sn superconducting wires with different layouts and fabrication processes.

Improved measuring plate solution method of density for rockfill dam based on the additional -mass model

Density control is the key index of quality control during the rockfill-construction period. Normally, traditional pits method used in rockfill-construction has several disadvantages, such as long test time, high manpower consumption, etc. Therefore, it will bring great interference to the construction progress. The new additional mass method has been widely used with advantages, such as fast test speed, no damage to dam body, etc. However, there are some shortcomings in the solution of added-mass method at present, such as limited test range, unclear theoretical basis and so on. In this paper, a new method of digital measurement plate construction is proposed. Firstly, the process of solving the density of prototype rockfill materials(PRFM) was described based on the equation-equivalence method. Then, two kinds of measurement plates were made by constructing parameter-equivalence diagrams. The validity of the method is verified by comparing test results and pit-test results in several different parts of the Shuangjiangkou dam. The new method is easy to calculate and the parameters could be equaled flexibly. Moreover, comparing with the previous digital measurement plate method, the new one has advantages, such as easier to be expanded and having a wider test range.

К методике обоснования границ между открытыми и подземными работами

Introduction. Currently, in the development of mineral deposits, the most widely used are open and underground methods. At the same time, open-pit mining is characterized by an extremely negative impact on the environmental situation, while at enterprises that develop deposits by underground methods, labor productivity is lower and, with some development systems, the extraction of minerals is much worse. The possibility of using open pit and underground works at one field makes it possible to use the advantages of each of the development methods, while reducing the negative factors of one of them at the expense of the other. The aim of the work is to assess the impact of technological solutions involving internal dumping on the establishment of a boundary between open pit and underground operations, taking into account the reduction of the technogenic impact on the environment. Methods for determining the boundaries of the open pit can be divided into 2 groups: the first includes methods for determining the boundaries of the open pit by the minimum total costs or the maximum total profit, the other includes methods using the boundary stripping ratio. In this work, when developing an economic-mathematical model, the methodology proposed by Professor A.I. Arsentiev, where profit is used as a criterion for the transition from open to underground work. As a result of the research, an economic-mathematical model was developed and tested to solve the problem of determining the boundary of the transition from open to underground work, based on obtaining additional profit by reducing environmental costs and taking into account the change in the order of dumping. Dependences have been obtained that reflect the change in the economically justified depth of the open pit on the degree of use of the mined-out space, as well as on the area of external dumps. The analysis of the obtained dependences shows that within the established limits and the given modeling parameters, the use of the worked-out space of the quarry allows to reduce the area of external dumps from 13 ha to 2 ha, while the boundary stripping ratio increases to 5.04, and the depth of the open pit increases from 105 m to 116 m. The results of the study can be used in the design of field development by open pit and combined methods.

Investigation of boring pile integrity of road systems in engineering-geological condition of Kazakhstan

The paper considers the testing of pile foundations for continuity at Atbasar pipeline facility. For testing monolithic concrete and reinforced concrete structures, a variety of the pit (pile integrity test) method is used – low-deformation dynamic tests. This is the most modern technique in the world practice of recent years. It allows you to check the continuity of all types of monolithic concrete and reinforced concrete structures, including concrete (reinforced concrete) piles, to identify defects in them. Based on the obtained pile data, as a result of testing for the continuity of foundations, the number of non-defective piles and defective piles are reflected, and solutions are proposed to ensure the reliability and safety of the pipeline operation. A total of 10 bored piles, which were located in 4 separately standing foundations, were investigated in the work. The results showed that 3 piles could have defects in the form of cracks or narrowing of the cross-section of the bored piles.

Experimental HTSC-MAGLEV System and Efficiency Evaluation of a Noncontact Acceleration of IFE Target Placed in a Levitating Carrier

Over the last two decades, superconducting materials have undergone an evolution that has broadened its application space. This work focuses on the issue of noncontact acceleration of fusion targets for fueling of a commercial Inertial Fusion Energy (IFE) power plant. This approach attracts a significant interest due to its potential for almost frictionless motion. The operational principle is the magnetic acceleration of the levitating target carrier (or HTSC-sabot) made from high-temperature superconducting tapes of the second generation (2G-HTSC). From physics, the possibility of their practical applications is directly related to the flux pinning of quantized magnetic flux lines in the superconductors (so called, high-pinning, Type-II HTSCs). The article describes the important achievements made in this area: 1) measurements of the magnetic moment of 2G-HTSC tapes (Tc = 92 K) in the wide temperature range of 10–95 K; 2) building a circular PMG system (outer radius is R = 50 mm, В = 0.13−0.25 T) to study magneto-thermo-mechanical interactions between HTSC-sabot and permanent magnets under external variable load with a rate of 2‒5 Hz; 3) studying a static and dynamic stability of the guidance force for a set of different top-down suspended HTSC-sabots; 4) calculation of the HTSC-sabot velocity at which it leaves a circular trajectory at temperatures of ~ 80 K to evaluate its behavior at T ~17 K. The obtained results are in a good agreement that will allow one to estimate the parameters of a circular accelerator of R = 1 m based on HTSC magnetic levitation (HTSC-MAGLEV) transport; the operating temperature is T ~17 K which is characteristic of the target delivery to IFE power plant. The results of this work provide theoretical and experimental support for the practical design and application of such ac-celerator for reaching the target injection velocities in the range of 200−400 m/s.

Evaluasi Kemiringan Jalan Tambang Terhadap Cycle Time Alat Angkut Pada Dump Truck Hino FG 235 JJ Tambang Batu Granit Di PT Aditya Buana Inter Kabupaten Bangka

PT ABI is a private company engaged in the granite mining business using the open pit method. The problem encountered is that there is a slope of the mine road that does not comply with the standards set by the company, namely ≤ 8%, the slope of the mine road, which is not suitable, makes the truck to produce large rimpull, which affects the overall distribution time. This study aims to evaluate and optimize the dump truck cycle time obtained. This research begins by calculating the actual travel time on 2 dump trucks in 40 trips, conveyance A gets 493.72 seconds and conveyance B is 495.75 seconds, the actual travel time on the haul road segment exceeds ≥ 8%, i.e. in the B-C segment which has a grade of 8.86% with an average travel time of 20.38 seconds and in the C-D segment which has a grade of 10.51% with an average travel time of 37.91 seconds. Obtained circulation time decreased by 5 seconds from 494.73 seconds to 489.69 seconds with a percentage increase of 1.04% after optimization, meaning that the conveyance can transport 89 tons more of material.

Deterioration of the 2G HTS tapes by the Ne+ ions irradiation (250 keV)

We discuss changes in properties of Gd-based high-temperature superconducting (HTS) tapes induced by 250 keV Ne+ ions irradiation. HTS tapes are used in devices operating in extreme radiation conditions with the prospect of using them in space industry. Ionizing radiation, including heavy ion bombardment, can introduce defects (e.g. Schottky, Frenkel ones) to the microstructure of tapes, leading to deterioration of the superconducting parameters. Therefore, the superconducting layer of the tape was implanted with fluences from 1012 to 1014 Ne+/cm2 to determine the cosmic ray irradiation effect. Comprehensive studies of the microstructural, structural, magnetic, and electrical properties of the irradiated tapes prove the microscopic origin of their deterioration. It is mainly due to oxygen deficiency and microstructural as well as structural defects. The critical current densities are reduced by 33% – 60% (depending on the external magnetic field) compared to the reference sample.

Review of commercial nuclear fusion projects

Nuclear fusion technologies have re-gained momentum in the last decade thanks to their disruptive potential in different fields, such as energy production and space propulsion, and to new technological developments, especially high temperature superconductor tapes, which allow overcoming previous performance or design limits. To date, reviews of recent nuclear fusion designs are lacking. Therefore, this paper aims at giving a comprehensive overview of nuclear fusion concepts for industrial applications with a focus on the private sector. The designs are classified according to the three leading concepts for plasma confinement, namely, magnetic confinement, inertial confinement and magneto-inertial confinement. The working principles of the main devices are described in detail to highlight strengths and weaknesses of the different designs. The importance of the public sector on private projects is discussed. The technological maturity is estimated, and the main criticalities for each project are identified. Finally, the geographical distribution of the companies (or public institutions) pursuing the design of fusion devices for commercial applications is reported.

Development of metal-organic deposition-derived second-generation high-temperature superconductor tapes and artificial flux pinning

Development of metal-organic deposition-derived second-generation high-temperature superconductor tapes and artificial flux pinning

Static magnetic field amplification in high-T c superconducting flux transformer equipped with multi-turn coil prepared using REBCO tape conductor

In this study, a high critical temperature (high-T c) superconducting flux transformer is prepared using a commercially available REBa2Cu3O y (REBCO) high-T c superconducting (HTS) tape conductor. The device configuration includes a 10 cm diameter pickup coil and a 3 cm diameter multi-turn input coil, which are formed by the “cut-and wind” method. The static magnetic field transfer efficiency between both coils has been estimated using inductance calculation of the multi-turn coils. The transfer efficiency measured is close to the calculation, and the field amplification of the transferred magnetic field compared to the applied field to the pickup coil is confirmed in the device which equipped with the multi-turn input coil. The magnitude of this magnetic field amplification has achieved to 125% of the applied field. This result suggests that the HTS flux transformer proposed in this study is effective in the sensitivity enhancement of the magnetometer for static magnetic fields.

Reproducible stable critical current density in powder-in-tube (PIT) Nb3Al superconductors by multi-time rapid heating and quenching process

This paper investigated the microstructure and superconductivity of the powder-in-tube (PIT) Nb3Al short samples with different rapid heating and quenching (RHQ) treatment. Single RHQ processed Nb3Al wires showed inhomogeneous microstructure and the superconductivity were sensitive to rapid heating temperature (Tmax), showing significant fluctuation with a slight change of Tmax. Multi-time RHQ treatment was performed to homogenize the Nb3Al superconductors. The highly uniform microstructure and composition distribution were found in 5-time RHQ processed Nb3Al wires, which exhibited significantly stable and excellent Jc performance. Reproducible stable Jc results of Nb3Al wires were realized in three samples of 5-time RHQ treatment with a difference of Tmax reaching about 200 °C. Jc of the three samples fluctuated less than 20% with results of 1.1 × 105 A/cm2, 9.87 × 104 A/cm2 and 9.51 × 104 A/cm2 at 4.2 K and 12 T. The insensitivity of Jc to Tmax in 5-time RHQ processed Nb3Al samples might attribute to the highly homogeneous Nb3Al A15 phase.

Characterization of Prismatic Slip in SiC Crystals by Chemical Etching Method

In 4H-silicon carbide crystals, basal plane slip is the predominant deformation mechanism. However, prismatic slip is often observed in single crystals grown by the physical vapor transport method as the diameter expands to 6 inches or larger. Thermal modeling has shown that occurrence of prismatic slip is attributed to increased radial thermal gradients. While X-ray topography can be used to characterize the presence and extent of prismatic slip, the feasibility of using the chemical etching method to assess the extent of prismatic slip in an industrial setting is investigated. The distribution of scallop shaped etch pits oriented along the directions that correspond to prismatic dislocations, correlate well with the results of the thermal model that predicts the occurrence of prismatic slip dislocations. This capability of the etch pit method to characterize prismatic slip can be used to manage radial thermal gradients during PVT growth.

Experimental measurements of contact resistivity between superconducting HTS tapes with or without metallic co-wound tape

REBCO No– or Metal-Insulation winding open the way to very high field magnets. However, in order to impose a reasonable loading time and to protect the magnet as well as possible, the value of the contact resistivity between turns must be controlled. In this paper, we first present our experimental station allowing measuring the contact resistivity between No-Insulation (NI) 6mm wide HTS superconducting tapes, as a function of the mechanical pressure and cooled down at liquid nitrogen temperature (77K). In a second part, we introduce the different types of winding pack measured in addition to NI: Metal-Insulation (MI), Soldered No-Insulation (SNI), Soldered Metal-Insulation (SMI) and double Metal-Insulation (2xMI). Changing the nature of the insulation between the turns changes the value of the contact resistivity and thus the behavior of a coil during a transient regime. These technologies are tested with superconducting tapes from different manufacturers: SuperPower (SP),Theva, ShanghaiSuperconductorTechnology (SST) and SuperOx. Then we will introduce and explain the different parameters of the superconducting and metallic tapes to have a contact resistivity between 1 and 107μΩ.cm2 in the case of our measurements.

Review of thermodynamics concerning phase transitions (How to increase high temperature superconductivity via quantum entanglement)

We review thermodynamic 4 variables and 4 potentials, and recommend precision optics interference. Measurement techniques for the phase transitions as follows. We consider the superconductivity as a Lambda (close to the 2nd order) phase transition phenomena. Then the quantum mechanics entanglement of two branches of superconductor wires that are made of YBCO 123 high temperature superconductor can be further increased one wire toward room temperature while still kept at zero resistance Ohm’s law measured by precision Optics Phase Conjugated Interferometer.

A Histogram Analysis of the Pixel Grayscale (Luminous Intensity) of B-Mode Ultrasound Images of the Subcutaneous Layer Predicts the Grade of Leg Edema in Pregnant Women.

The technique most widely used to quantitatively measure leg edema is only a pitting edema method. It has recently become possible to digitize B-mode ultrasound images and accurately quantify their brightness using an image-analysis software program. The purpose of this study was to find new indices of the grade of leg skin, to study whether or not analyses of the subcutaneous layer of leg skin on ultrasound images using image-editing software program can be used to evaluate it and to digitize it. Images of 282 subcutaneous layers of leg skin in 141 pregnant women were obtained using a B-scan portable ultrasound device. Rectangular photographs (vertical: skin thickness; horizontal: width of probe) were obtained using an image-editing program, and the luminous intensity (pixel grayscale: 0-255) and thickness of the skin were calculated using a histogram. We investigated the correlation between these parameters and the grade of pitting edema (0-3). There was a significant positive correlation between the grade of pitting edema and the average luminous intensity value, its standard deviation, and the skin thickness (ρ = 0.36, ρ = 0.22, ρ = 0.51, p < 0.0001, respectively). In particular, there was strong positive correlation between the grade of pitting edema and both the total number of pixels in a rectangle × (multiplied by) the average luminous intensity value and the total number of pixels in a rectangle × the standard deviation of the average luminous intensity value (ρ = 0.58 and ρ = 0.59, p < 0.0001, respectively). We could quantitatively evaluate the grade of leg edema by analyzing ultrasound photographs of the subcutaneous layer of the leg skin using an image-editing software program and found new indices to digitize it.