Conductor Technology Research Articles

A structural health monitoring system of the overhead transmission line conductor

Transmission lines are affected by aeolian vibration, sandstorms and acid rain, which cause structural damage and eventually lead to line breaking accidents. In this paper, the structural health monitoring technology of conductors is researched, and a structural monitoring system for conductors is designed. First, based on the structure of the ACSR (Aluminum Conductor Steel Reinforced) conductor and the dynamic equation, the relation between the natural frequencies and the structure of the conductor is obtained. Then, an online health monitoring system of the conductor structure is proposed, and key issues, such as the power supply solution of sensors, data preprocessing technology, multiple-sensor synchronization method, are analyzed in detail. Finally, the structural health monitoring of overhead transmission lines designed in this paper is tested on 110-kV experimental transmission lines. The experimental results show that from the system proposed the operation parameters of the conductors can be well obtained.

Microscale Liquid Metal Conductors for Stretchable and Transparent Electronics

AbstractIntegrated wearable electronics capable of transducing and transmitting biophysical information on complex and dynamic systems are attracting high interest across the consumer electronics, clinical, and research domains. Gallium and gallium‐based liquid metals (LMs) emerge as promising conductor technology for wearables due to their excellent combination of electrical conductivity and mechanical compliance. However, LMs feature complex physical and chemical properties that pose significant manufacturability challenges. Herein, a microtechnology approach is presented to fabricate deformable, microscale LM conductors with high surface density and over large surface areas. Based on a combination of soft lithography, directional patterning, and thermal evaporation of gallium, this new technology enables a range of designs and geometries that can be used to form LM‐based stretchable electronic conductors. The versatility of the technology enables a palette of circuit designs that can offer unrivaled transparency (T > 89%) or large metallization density (2/5 µm line/gap).

Dimensional scaling of thin-film stimulation electrode systems in translational research

Objective. Electrical stimulation of biological tissue is an established technique in research and clinical practice that uses implanted electrodes to deliver electrical pulses for a variety of therapies. Significant research currently explores new electrode system technologies and stimulation protocols in preclinical models, aiming at both improving the electrode performance and confirming therapeutic efficacy. Assessing the scalability of newly proposed electrode technology and their use for tissue stimulation remains, however, an open question. Approach. We propose a simplified electrical model that formalizes the dimensional scaling of stimulation electrode systems. We use established equations describing the electrode impedance, and apply them to the case of stimulation electrodes driven by a voltage-capped pulse generator. Main results. We find a hard, intrinsic upward scalability limit to the electrode radius that largely depends on the conductor technology. We finally provide a simple analytical formula predicting the maximum size of a stimulation electrode as a function of the stimulation parameters and conductor resistance. Significance. Our results highlight the importance of careful geometrical and electrical designs of electrode systems based on novel thin-film technologies and that become particularly relevant for their translational implementation with electrode geometries approaching clinical human size electrodes and interfacing with voltage-capped neurostimulation systems.

Control of the nanosized defect network in superconducting thin films by target grain size

A nanograined YBCO target, where a great number of grain boundaries, pores etc. exist, is shown to hold an alternative approach to future pulsed laser deposition based high-temperature superconductor thin film and coated conductor technologies. Although the nanograined material is introduced earlier, in this work, we comprehensively demonstrate the modified ablation process, together with unconventional nucleation and growth mechanisms that produces dramatically enhanced flux pinning properties. The results can be generalized to other complex magnetic oxides, where an increased number of defects are needed for modifying their magnetic and electrical properties, thus improving their usability in the future technological challenges.

Discussion on Static Conductor Technology of MCCB from Patent

Discussion on Static Conductor Technology of MCCB from Patent

Interface-mediated plasticity and fracture in nanoscale Cu/Nb multilayers as revealed by in situ clamped microbeam bending

Properties of metal-metal nanolaminates have been studied for the past decade to meet the ever-increasing demand for strong and tough structural materials. Interface engineering is typically employed to prolong the material lifecycle by hindering crack propagation across the layers of nanolaminates. Various studies have been performed to understand the role of interfaces during plastic deformation in such nanolaminates. Nevertheless, detailed studies with direct observation capability on the mechanisms of deformation leading to failure are still scarce, especially in bending mode (which is the more realistic loading condition of structural materials in service). Therefore, in this study, in situ beam bending tests (inside a Scanning Electron Microscope) were performed on accumulative roll bonded (ARB) pre-notched Cu/Nb clamped beams. A large extent of notch widening (which was used as a measure for the extent of the capacity of the materials for interfacial sliding/shearing) during cross-layer fracture was observed for Cu/Nb (16 nm) ARB beams (i.e., with 16 nm individual layer thickness in both Cu and Nb layers) which were fabricated along the transverse direction (TD) of the ARB process. This may be attributed to an increase in layer strength (due to the small sizes) and interface-based localized plastic mechanisms (sliding/shearing, rotation, etc.). Upon comparison with our previous work (Cu/Nb ARB samples with large individual layer thickness, or fabricated along different directions in the ARB process), the extent of the interfacial sliding was found to be significantly large, indicating possible size effects and/or different/additional mechanisms of localized shearing/plasticity on the interfaces. These mechanisms can be further exploited for the design and development of a novel class of metallic flexible materials or conductor technologies.

Development and performance of a 2.9 Tesla dipole magnet using high-temperature superconducting CORC® wires

Although the high-temperature superconducting (HTS) REBa2Cu3O x (REBCO, RE–rare earth elements) material has a strong potential to enable dipole magnetic fields above 20 T in future circular particle colliders, the magnet and conductor technology needs to be developed. As part of an ongoing development to address this need, here we report on our CORC® canted cosθ magnet called C2 with a target dipole field of 3 T in a 65 mm aperture. The magnet was wound with 70 m of 3.8 mm diameter CORC® wire on machined metal mandrels. The wire had 30 commercial REBCO tapes from SuperPower Inc. each 2 mm wide with a 30 µm thick substrate. The magnet generated a peak dipole field of 2.91 T at 6.290 kA, 4.2 K. The magnet could be consistently driven into the flux-flow regime with reproducible voltage rise at an engineering current density between 400–550 A mm−2, allowing reliable quench detection and magnet protection. The C2 magnet represents another successful step towards the development of high-field accelerator magnet and CORC® conductor technologies. The test results highlighted two development needs: continue improving the performance and flexibility of CORC® wires and develop the capability to identify locations of first onset of flux-flow voltage.

False metals, real insulators, and degenerate gapped metals

This paper deals with a significant family of compounds predicted by simplistic electronic structure theory to be metals but are, in fact, insulators. This false metallic state has been traditionally attributed in the literature to reflect the absence of proper treatment of electron-electron correlation (“Mott insulators”) whereas, in fact, even mean-field like density functional theory describes the insulating phase correctly if the restrictions posed on the simplistic theory are avoided. Such unwarranted restrictions included different forms of disallowing symmetry breaking described in this article. As the science and technology of conductors have transitioned from studying simple elemental metals such as Al or Cu to compound conductors such as binary or ternary oxides and pnictides, a special class of degenerate but gapped metals has been noticed. Their presumed electronic configurations show the Fermi level inside the conduction band or valence band, yet there is an “internal band gap” between the principal band edges. The significance of this electronic configuration is that it might be unstable toward the formation of states inside the internal band gap when the formation of such states costs less energy than the energy gained by transferring carriers from the conduction band to these lower energy acceptor states, changing the original (false) metal to an insulator. The analogous process also exists for degenerate but gapped metals with the Fermi level inside the valence band, where the energy gain is defined by transfer of electrons from the donor level to the unoccupied part of the valence band. We focus here on the fact that numerous electronic structure methodologies have overlooked some physical factors that could stabilize the insulating alternative, predicting instead false metals that do not really exist (note that this is in general not a physical phase transition, but a correction of a previous error in theory that led to a false prediction of a metal). Such errors include: (i) ignoring spin symmetry breaking, such as disallowing magnetic spin ordering in CuBi2O4 or disallowing the formation of polymorphous spin networks in paramagnetic LaTiO3 and YTiO3; (ii) ignoring structural symmetry breaking, e.g., not enabling energy-lowering bond disproportionation (Li-doped TiO2, SrBiO3, and rare-earth nickelates), or not exploring pseudo-Jahn–Teller-like distortions in LaMnO3, or disallowing spontaneous formation of ordered vacancy compounds in Ba4As3 and Ag3Al22O34; and (iii) ignoring spin–orbit coupling forcing false metallic states in CaIrO3 and Sr2IrO4. The distinction between false metals vs real insulators is important because (a) predicting theoretically that a given compound is metal even though it is found to be an insulator often creates the temptation to invoke high order novel physical effects (such as correlation in d-electron Mott insulators) to explain what was in effect caused by a more mundane artifact in a lower-level mean-field band theory, (b) recent prediction of exotic physical effects such as topological semimetals were unfortunately based on the above compounds that were misconstrued by theory to be metal, but are now recognized to be stable insulators not hosting exotic effects, and (c) practical technological applications based on stable degenerate but gapped metals such as transparent conductors or electrides for catalysis must rely on the systematically correct and reliable theoretical classification of metals vs insulators.

How thin can you go? Performance of thin copper and aluminum RF coil conductors

To evaluate the impact of emerging conductor technology on RF coils. Performance and resulting image quality of thin or alternate conductors (eg, aluminum instead of copper) and thicknesses (9-600 μm) are compared in terms of SNR. Eight prototype RF coils (15 cm × 15 cm square loops) were constructed and bench-tested to measure quality factor. The coils used 6-mm-wide conducting strips of either copper or aluminum of a few different thicknesses (copper: 17, 32, 35, 127, 600 μm; aluminum: 9, 13, 20, 127μm) on acetate projector sheets for backing. Corresponding image SNR was measured at 0.48 tesla (20.56MHz). The coils spanned a range of unloaded quality factors from 89 to 390 and a fivefold range of losses. The image SNRs were consistent with the coils' bench-measured efficiencies (0.33-0.73). Thin aluminum conductors (9μm) led to the highest reduction in SNR (65% that of 127 μm copper). Thin copper (<32 μm) conductors lead to a much smaller decrease in SNR (approximately 10%) compared to 127 μm copper. No performance difference was observed between 127 μm thick copper and aluminum. The much thicker 600 μm copper bars only yield a 5% improvement in SNR. Even at 0.48 tesla, copper RF coil conductors much thinner than those in conventional construction can be used while maintaining SNR greater than 50% that of thick copper. These emerging coil conductor technologies enable RF coil functionality that cannot be achieved otherwise.

Multiband Dual-Meander Line Antenna for Body-Centric Networks’ Biomedical Applications by Using UMC 180 nm

A new, compact, on-chip antenna architecture for 5G body-centric networks’ (BCNs) applications is presented in this paper. The integrated antenna combines two turns of dual-meander lines (DML) on two stacked layers and a metal ground layer. The proposed DML antenna structure operated at resonant bands 22 GHz, 34 GHz, 44 GHz, and 58 GHz with an operating bandwidth up to 2 GHz at impedance bandwidth ≤−7.5 dB (VSWR—Voltage Standing Wave Ratio ≤ 2.5) and antenna gain about −20 dBi, −15 dBi, −10 dBi, and −1 dBi, respectively. Then it was compared with conventional single-meander line antenna. The proposed structure decreased the resonant frequency by 22%, increased number of tuning bands, and broadened the operating bandwidth by 25%, 15%, 10%, and 20% for the tuning bands to be a suitable choice for high-data -ate biomedical applications. Furthermore, the proposed antenna was simulated and studied for its performance on and inside the human body to test the integration effect in wearable equipment. The results showed that the antenna had acceptable performance in both locations. All simulations of the proposed antenna were done were done by using Ansys HFSS (high-frequency structure simulator) v.15 (Ansys, Canonsburg, PA, USA). The DML (Digital Microwave Links) antenna was fabricated by using UMC (United Microelectronics Corporation) 180 nm CMOS (Complementary Metal–Oxidesemi–Conductor) technology with a total area of 1150 µm × 200 µm and the results showed a good agreement between measured and simulated results.

Epitaxial Zr-doped CeO2 films by chemical solution deposition as buffer layers for Fe(Se,Te) film growth

The epitaxial growth of Zr-doped CeO2 (CZO) films by chemical solution deposition (CSD) on single crystal substrates such as Al2O3, SrTiO3 and Y2O3-stabilized ZrO2 (YSZ) and their use as buffer layers for Fe(Se,Te) film growth are reported. The growth of 30 nm thin CZO films is mostly dominated by dewetting issues, leading to highly incomplete substrate coverage due to the strong tendency of CZO grains to agglomerate. This effect is less severe on YSZ substrate and, in addition, can be fully controlled by setting the deposition temperature at 950 °C and operating under Ar–H2 reducing atmosphere. These conditions promote the growth of epitaxial and compact CZO films on YSZ, showing a flat surface morphology with root-mean-square roughness around 2.5 nm. Preliminary results on Fe(Se,Te) film deposited by pulsed laser deposition on CZO-buffered YSZ are reported. Although good epitaxial growth is achieved on CZO buffer layer, Fe(Se,Te) films exhibit poor superconducting properties. On the other hand, Fe(Se,Te) films show excellent properties when a seed layer is used, exhibiting a sharp superconducting transition at about 17 K and a critical current density exceeding 1 MA cm−2 at 4.2 K in self field. The main role of the seed layer, consisting of a non-superconducting Fe(Se,Te) film, is to favour the crystal and chemical matching between buffer layer and film, allowing for the growth of high-quality superconducting Fe(Se,Te) at deposition temperature as low as 200 °C.In perspective of applications, this result is a significant step towards process simplification and cost reduction of Fe(Se,Te)-based coated conductor technology development, being the first demonstration of superconducting Fe(Se,Te) films grown on CSD buffer layer.

Recent Progress in the Development of CORC Cable-In-Conduit Conductors

In recent years, three unique Re BCO-CORC CICC samples with six-around-one cable layout were developed as technology demonstrators at CERN in collaboration with Advanced Conductor Technologies. The tests of these conductors at low temperature in external magnetic field yielded very promising results, but also showed several issues requiring improvement. A new 2.8 m long CORC CICC has been prepared to replace a degraded sample. The voids between CORC strands in the new sample are filled with solder alloy to provide increased mechanical support to the strands, however, this yielded an additional set of new challenges. The conductor has a design critical current of 100 kA at 10 T and 4.5 K and is designed specifically for high-current bus-bars and large detector-type magnets. It therefore features a copper jacket and practical conduction cooling via a cooling line embedded in the jacket.

Research at Varian on applied superconductivity for proton therapy

Proton therapy is a rapidly increasing modality to treat cancerous tumors, but large-scale implementation, and therefore widespread availability for patients, is hindered by the size and upfront investment for treatment facilities. Superconducting technology can enable more compact, and therefore more affordable treatment systems, by increasing the magnetic field in the magnets for the proton accelerator (typically a cyclotron) and in the beam guidance up, over, and into the patient (the gantry). In this article, we discuss research at Varian Medical Systems Particle Therapy GmbH on various superconducting technologies for potential application in future, more compact cyclotrons and gantries. We discuss which technologies are feasible, and to what extent. We demonstrate why certain conductor choices are made, and show the development of novel new conductor and magnet technologies that will be required to enable the next generation of cryogen-free, conduction-cooled compact treatment systems. We conclude that superconductivity is certainly required for the next generation of proton treatment systems, but also that the amount of compactness that can eventually be achieved is not solely determined by the magnetic field strength that is generated in the magnets.

Introduction of the next generation of CORC® wires with engineering current density exceeding 650 A mm−2 at 12 T based on SuperPower’s ReBCO tapes containing substrates of 25 μm thickness

Next generation particle accelerators and fusion machines will greatly benefit from the development of low-inductance magnets capable of generating magnetic fields in excess of 16 T. Such magnets require high-temperature superconductors capable of carrying very high currents exceeding 5 kA at current densities of 400–600 A mm−2, such as Conductor on Round Core (CORC®) cables and wires wound from RE-Ba2Ca3O7-δ (ReBCO, Re = rare earth) coated conductor tapes. CORC® wires containing ReBCO tapes with 30 μm thick Hastelloy® substrates have previously been demonstrated as a viable high-field magnet conductor that can be produced at long lengths. Further improvement of the performance and flexibility of CORC® wires would benefit from the development of ReBCO tapes with even thinner substrates. SuperPower Inc. recently demonstrated ReBCO tapes based on 25 μm thick Hastelloy® substrates that allow the development of thinner and more flexible CORC® wires that meet the stringent performance requirements of high-field magnets. Several tapes containing 25 μm thick substrates were produced and analyzed, exhibiting critical current and cabling performance in-line with the current production level tapes with 30–50 μm thick substrates. Tape critical current was measured at 4.2 K and applied magnetic fields up to 31.2 T. Several CORC® wires incorporating these tapes were manufactured by Advanced Conductor Technologies using similar winding procedures that previously resulted in high-quality magnet-grade CORC® wires based on tapes with 30 μm thick substrates. The CORC® wires were tested in an applied magnetic field up to 12 T after bending to a 63 mm diameter. A critical current as high as 6231 A (12 T, 4.2 K) was measured with an engineering current density (Je) of 678 A mm−2, which extrapolates to over 450 A mm−2 at 20 T and is the highest current density reported in a CORC® conductor to date. The combination of ReBCO tapes produced using 25 μm thick substrates and the ability to wind them into long-length, high-quality CORC® magnet wires brings the development of low-inductance accelerator and fusion magnets that operate at magnetic fields exceeding 20 T closer to fruition.

Non-contact Dynamic Capacity-Increasing of Overhead Conductor Based on Cooling Tester (CT)

The traditional dynamic capacity-increasing technology of overhead conductors needs to monitor the operation state of conductors (temperature, sag, etc.), and the relevant sensors are usually installed directly on the surface of conductors. The installation cost is high, and the operating maintenance is complicated. In this paper, a non-contact dynamic capacity-increasing method for overhead conductors based on CT is proposed. Firstly, the theory of the non-contact dynamic capacity-increasing method for conductors is introduced, and a cooling testing device is designed according to the theory. Then, the cooling index is defined to represent the cooling capacity of the object, and the corresponding cooling indexes for the conductors and the CT are calculated based on the steady-state thermal balance equation. By establishing a cooling correlation model for the conductors and the CT, the calculation for the dynamic ampacity of the conductors can be obtained. Finally, the cooling conditions of cooling testing device at different ambient temperatures and wind speeds are calculated through the finite element simulation method. Combined with the dynamic capacityincreasing method proposed in this paper, the corresponding ampacity value are obtained, and the effect of capacity increase is analyzed. The results show that the non-contact dynamic capacity-increasing method based on the CT has obvious effect in capacity-increasing compared with the static ampacity.

Application of Adhesive Compositions Based on a Silicon Sealant and an Acrylic Adhesive as Binders in the Technology of Flexible Conductors

An adhesive composition based on acrylic acid and a silicon sealant is developed for impregnating carbon-fiber materials to obtain composites that can be used as flexible conductors. The physicomechanical and dynamic characteristics of the developed adhesive are investigated, and optimal impregnation conditions are determined. It is demonstrated that using this composite makes it possible to increase the operation life of a flexible conductor due by preserving high strength under alternating bending strains over a long period of time.

Metasurface-Based Method for Broadband RCS Reduction of Dihedral Corner Reflectors With Multiple Bounces

A broadband technique to reduce the radar cross section (RCS) of complex targets is presented. In such targets, multiple-bounce mechanism dominates their RCS. The proposed technique demonstrates that by treating the multiple-bounce mechanism as a cascaded phenomenon, the problem then simplifies to identifying and implementing a set of orthogonal functions. Robust guidelines for avoiding grating lobes are provided using array theory. The 90° dihedral corner is used to verify the proposed technique. Measurements are reported for a fabricated prototype with artificial magnetic conductor (AMC) technology where a 70% RCS-reduction bandwidth is observed. To generalize the method, a 45° dihedral corner, with quadruple-bounce mechanism, is considered. Generalized guidelines are summarized and applied to reduce the RCS of complex targets using the proposed method.

Dipole Magnets above 20 Tesla: Research Needs for a Path via High-Temperature Superconducting REBCO Conductors

To enable the physics research that continues to deepen our understanding of the Universe, future circular colliders will require a critical and unique instrument—magnets that can generate a dipole field of 20 T and above. However, today’s maturing magnet technology for low-temperature superconductors (Nb-Ti and Nb3Sn) can lead to a maximum dipole field of around 16 T. High-temperature superconductors such as REBCO can, in principle, generate higher dipole fields but significant challenges exist for both conductor and magnet technology. To address these challenges, several critical research needs, including direct needs on instrumentation and measurements, are identified to push for the maximum dipole fields a REBCO accelerator magnet can generate. We discuss the research needs by reviewing the current results and outlining the perspectives for future technology development, followed by a brief update on the status of the technology development at Lawrence Berkeley National Laboratory. We present a roadmap for the next decade to develop 20 T-class REBCO accelerator magnets as an enabling instrument for future energy-frontier accelerator complex.

Overview of verification tests on AC loss, contact resistance and mechanical properties of ITER conductors with transverse loading up to 30 000 cycles

The ITER magnet system uses cable-in-conduit conductor (CICC) technology with individual strands twisted in several stages resulting in a rope-type cable, which is inserted into a stainless steel conduit. The combination of high current (up to 68 kA) and background magnetic field (up to 13 T) results in large transverse Lorentz forces exerted on the conductors during magnet system operation. The high transverse forces, accompanied with the cyclic nature of the load, have a strong influence on the conductor properties. The Twente Cryogenic Cable Press is used to simulate the effect of the Lorentz forces on a conductor comparable to the ITER magnet operating conditions. An overview is presented of the AC coupling and hysteresis loss, mechanical deformation characteristics and inter-strand contact resistance measurement results obtained on full-size ITER CICCs measured in the Twente Cryogenic Cable Press. The aim of this work is to characterize conductors’ electromagnetic and mechanical properties during cycling of the load up to 30 000 cycles. The evolution of the magnetization (AC coupling loss time constant nτ), mechanical properties and inter-strand resistance Rc between selected strands is presented along with loading history. The Rc between first triplet strands is also measured as a function of applied load. It is shown that transverse load cycling has a strong influence on the CICC properties. An overview of the results for eight toroidal field conductors, two central solenoid conductors, three poloidal field conductors of different types (PF1&6, PF4, PF5), one main bus-bar and one correction coil conductor is presented.

Weak or Strong Anisotropy in Fe(Se,Te) Superconducting Thin Films Made of Layered Iron-Based Material?

We study the temperature dependence of the upper critical magnetic field Hc2 in a layered iron-based superconducting (IBS) material of the 11-family, namely the Fe(Se,Te) thin film grown on CaF2 substrate. On the basis of intrinsic anisotropy as well as system dimensionality, it turns useful to make a comparison with an ultrathin film conventional low temperature superconductors (LTS) such as NbN, mostly used for device applications. We compare the anisotropy factors as a function of temperature and magnetic field. Both materials present a peculiar behavior: The LTS behaves as a strong anisotropic system, whereas the IBS shows very weak anisotropic features. The strong NbN character can be directly ascribed to the dimensionality of the ultrathin film employed, thus revealing a geometry effect. The weak Fe(Se,Te) trend should be related to its layered crystallographic structure, thus probing an intrinsic origin of its anisotropy. These characteristics become relevant for the potential application of this material in coated conductor technology.