Conductivity Performance Research Articles

Mechanical and Electrical Modeling of Strands in Two ITER CS Cable Designs

Following the test of the first Central Solenoid (CS) conductor short samples for the International Thermonuclear Experimental Reactor (ITER) in the SULTAN facility, Iter Organization (IO) decided to manufacture and test two alternate samples using four different cable designs. These samples, while using the same Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strand, were meant to assess the influence of various cable design parameters on the conductor performance and behavior under mechanical cycling. In particular, the second of these samples, CSIO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , aimed at comparing designs with modified cabling twist pitches sequences. This sample has been tested, and the two legs exhibited very different behaviors. To help understand what could lead to such a difference, these two cables were mechanically modeled using the MULTIFIL code, and the resulting strain map was used as an input into the CEA electrical code CARMEN. This article presents the main data extracted from the mechanical simulation and its use into the electrical modeling of individual strands inside the CICC.

16.1: Sub‐Micron Transparent Metal Mesh Conductor for Touch Screen Displays

AbstractWe report on a recently developed superior ITO‐alternative transparent conductor, based on metal mesh technology. Trademarked by Rolith, Inc as NanoWeb®, metal mesh has the narrowest lines on the market (&lt; 1 micron), which assures complete invisibility of the mesh under the most strict illumination conditions. It has also removed the necessity to optimize metal mesh design for each display structure, since it does not create a visible Moiré fringes, as do other metal mesh conductors on the market. We report also on “best‐in‐class” optical, electrical and mechanical performance of NanoWeb conductor fabricated on glass plates and PET films.

Thermal Hydraulic Analysis of the ITER PF and Correction Coils in 15 MA Scenario Operation Using the SuperMagnet Suite of Codes

The poloidal field (PF) coils and correction coils (CCs) constitute one of the four hydraulic loops of the ITER magnet system. They are cooled in parallel by the same heat exchanger. The PF coils consist of 6 different pulsed coils while the CCs include 18 coils divided into 3 different sets: bottom, side and top. The PF coils are made of dual-channel NbTi conductors whereas the CCs consist of single-channel NbTi conductors. The SuperMagnet suite of codes can combine 1-D cooling with supercritical helium flow in the ITER conductors and the 2-D heat diffusion across the coils into a full-scale quasi 3-D model. We analyzed the in-coil NbTi conductor performance and the heat load to the cryogenic plant. We also compared the results from Vincenta and SuperMagnet.

Test Results of RF ITER TF Conductors in the SULTAN Test Facility

The cable-in-conduit-conductors (CICC) for the ITER Toroidal Field (TF) Coils are tested in the Sultan test facility in order to estimate their AC and DC performances under operating conditions. The tests are carried out on different stages of conductor procurement implementation starting from Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn superconducting strand layout and process development to regular checks of production unit lengths. Four TF samples provided by Russia have been successfully tested in the Sultan facility by now in the framework of the ITER collaboration, including Strand Performances Qualification Sample, Qualification Conductor Sample, Pre-production and Production Conductors sample. The test results of all four samples shows pretty good reproducibility of the conductor performances from sample to sample and at the same time good stability of conductor performance under mechanical loading caused by Lorenz force during electromagnetic (EM) cycling can be observed. In the present work a comparison of the conductors and their performance was carried out to show the development of conductor performances from R&D stage to mass production.

Production Results of 11.75 Tesla Iseult/INUMAC MRI Conductor at Luvata

Large quantities of NbTi-based superconductors have been produced for the 11.75 Tesla whole body magnetic resonance imaging project called the Iseult/INUMAC managed by CEA Saclay. The magnet is designed to operate at 1.8 K. Production consisted of nearly 65 t (170 km) of a large 9.2 mm × 4.9 mm Rutherford cable-in-channel for the main coil and 22 t (58 km) of a 9.1 mm × 4.2 mm wire-in-channel for the shield. These have been successfully manufactured, inspected, and delivered. The key technical requirements were dimensional precision, superconducting properties, RRR, and tensile strength. An extensive quality assurance program was instituted to guarantee the final conductor performance. Measured degradation in superconducting characteristics due to cabling and solder integration were negligible (<;3%). Results show that we have achieved state-of-the-art critical current density and n values for this very high field NbTi application. We will report test data including statistical summaries.

Design of a $\hbox{Nb}_{3}\hbox{Sn}$ Cable-in-Conduit Conductor to Withstand the 60 000 Electromagnetic Cycles of the ITER Central Solenoid

The performance of the ITER Nb3Sn cable-in-conduit conductor tested in Sultan for the toroidal field (TF) coils have shown some limited degradation with cycling, which is consistent with the conductor performance requirement, as the TF coils are designed for an upper limit of 1000 electromagnetic cycles. The first samples of the central solenoid (CS) Nb3Sn conductor tested in Sultan have also shown some degradation with electromagnetic and thermal cycling. However, this is not considered appropriate as the CS conductor has to sustain 60 000 electromagnetic cycles during the lifetime of the tokamak. A sample of a CS conductor based on a locked cable configuration including segregated copper strands and designed to achieve saturation versus cycling has been fabricated and tested successfully in the Sultan test facility. Additional samples of CS conductor fabricated on the same principle have confirmed the observed very low sensitivity to cycling. The Sultan test results show that a locked cable configuration achieved by a short twist pitch cable pattern can cure the problem of degradation versus cycling for both types of strand, internal Sn and bronze route.

Overview of Conductor Production for ITER Toroidal Field Magnet in Korea

The ITER toroidal field (TF) conductor is made up of superconducting Nb3Sn and copper strands assembled into a multistage, rope-type cable inserted into a conduit of butt-welded stainless steel jacket sections. For the ITER Project, the Korean Domestic Agency (KODA) took the responsibility of the procurement of 27 superconducting conductors for the ITER TF magnets. After concluding the Procurement Arrangement (PA) with the ITER International Organization in May 2008, KODA has been implementing the PA through four major industrial contracts: (1) Nb3Sn strand, (2) cable, (3) stainless steel jacket sections, and (4) jacketing. Prior to the production of conductors required for the TF coils, one 760-m-long copper dummy conductor and one 100-m-long superconducting conductor were fabricated for manufacturing process qualification. As of June 2013, 16 TF conductors were successfully manufactured. The full-size conductor performance tests in the SULTAN facility yielded very high performance. This article describes the technical requirements of the TF conductor and how KODA has been manufacturing the conductors with a high-level quality assurance/quality control system. It also presents the results of acceptance tests, including those of the SULTAN test.

Study of the Temperature and Field Dependence of the Critical Currents in Nb-Ti Strands for the ITER Poloidal Field Magnet System

Commercial multifilamentary Nb-Ti strands produced by the Russian Federation DA for the ITER poloidal field coils PF1 and PF6 were characterized regarding the critical current versus magnetic field dependence from 2 to 10 T over a wide range of temperatures from 2.5 to 7 K. The data were collected on several Nb-Ti strands at the stage before production and after 30% of the production for the ITER program. J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> (B, T) fits were determined using parameterization models with single pinning and two-pinning components. The validity and limitation of these estimations will be discussed. The pinning force curves are presented in the temperature range from 2.5 to 4.2 K and indicate a shift of the pinning force peak to lower fields with increasing temperature. The current sharing temperature T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cs</sub> at the operating current (33 A) and field (6.4 T) was determined from both parameterization models. The results of T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cs</sub> show good reproducibility for each set of Nb-Ti strands. The good agreement between experimental and fit results over very wide temperature ranges can be used for the analysis of experimental data on the PF conductor performance and for the design of future superconducting magnets.

Optimizing the Performance of Metal Grid Conductors for Light-Emitting Electrochemical Cell Devices by Modifying Printing Conditions

Printed metal grid conductors can be used in thin, flexible and large-area lighting sources based on, e.g., light-emitting electrochemical cells (LECs). Similar to organic light-emitting diodes (OLEDs), LECs are thin-film electroluminescent devices, which can be processed from solution. However, LECs have a simpler architecture, and do not rely on air-sensitive charge-injection layers or metals for electron injection. This offers simplicity for manufacturing process, cost-efficiency and easier large-scale manufacture. Printing methods such as inkjet and flexography are suitable for manufacturing the metal grid conductors needed in LEC devices. The goal of this article is to evaluate the potential of flexographic and inkjet printing to manufacture metal grid conductors on an industrial scale. Printing equipment that can be up-scaled to industrial scale is used and the printing conditions are modified to meet the device requirements. The performance and properties of inkjet and flexographic printed conductors are compared. Finally, the performance of full LEC devices is evaluated. As a conclusion, both inkjet and flexographic printing were found to be suitable for fabricating metal grid conductors since the surface roughness, layer thickness and electrical performance met the target values when the printing conditions were carefully optimized. Some compromises had to be made between adhesion, surface roughness, layer thickness and process reliability requirements. Finally, the performance of inkjet printed LEC devices has been demonstrated.

Coated conductors for power applications: materials challenges

This manuscript reports on the recent progress and the remaining materials challenges in the development of coated conductors (CCs) for power applications and magnets, with a particular emphasis on the different initiatives being active at present in Europe. We first summarize the scientific and technological scope where CCs have been raised as a complex technology product and then we show that there exists still much room for performance improvement. The objectives and CC architectures being explored in the scope of the European project EUROTAPES are widely described and their potential in generating novel breakthroughs emphasized. The overall goal of this project is to create synergy among academic and industrial partners to go well beyond the state of the art in several scientific issues related to CCs’ enhanced performances and to develop nanoengineered CCs with reduced costs, using high throughput manufacturing processes which incorporate quality control tools and so lead to higher yields. Three general application targets are considered which will require different conductor architectures and performances and so the strategy is to combine vacuum and chemical solution deposition approaches to achieve the targeted goals. A few examples of such approaches are described related to defining new conductor architectures and shapes, as well as vortex pinning enhancement through novel paths towards nanostructure generation. Particular emphasis is made on solution chemistry approaches. We also describe the efforts being made in transforming the CCs into assembled conductors and cables which achieve appealing mechanical and electromagnetic performances for power systems. Finally, we briefly mention some outstanding superconducting power application projects being active at present, in Europe and worldwide, to exemplify the strong advances in reaching the demands to integrate them in a new electrical engineering paradigm.

Significant performance enhancement of yttrium-doped barium cerate proton conductor as electrolyte for solid oxide fuel cells through a Pd ingress–egress approach

Proton-conducting perovskite oxides are excellent electrolyte materials for SOFCs that may improve power density at reduced temperatures and increase fuel efficiency, thus encouraging the widespread implementation of this attractive technology. The main challenges in the application of these oxides in SOFCs are difficult sintering and insufficient conductivity in real cells. In this study, we propose a novel method to significantly enhance the performance of a yttrium-doped barium cerate proton conductor as an electrolyte for SOFCs through a Pd ingress–egress approach to the development of BaCe0.8Y0.1Pd0.1O3−δ (BCYP10). The capability of the Pd egress from the BCYP10 perovskite lattice is demonstrated by H2-TPR, XRD, EDX mapping of STEM and XPS. Significant improvement in the sinterability is observed after the introduction of Pd due to the increased ionic conductivity and the sintering aid effect of egressed Pd. The formation of a B-site cation defect structure after Pd egress and the consequent modification of perovskite grain boundaries with Pd nanoparticles leads to a proton conductivity of BCYP10 that is approximately 3 times higher than that of BCY under a reducing atmosphere. A single cell with a thin film BCYP10 electrolyte reaches a peak power density as high as 645 mA cm−2 at 700 °C.

The performance test and analysis of the third and fourth China PF conductor for ITER

The third Chinese PF conductor for ITER PF5 (PFCN3) and the fourth Chinese PF conductor for ITER PF2/3/4 (PFCN4) conductor in Phase II were manufactured in ASIPP and tested in the SULTAN facility. This paper introduces the PFCN3 and PFCN4 sample manufacture, including strand, sample preparation, current sharing temperature (Tcs), AC loss and Minimum Quench Energy (MQE) test performance of PFCN3 and PFCN4 conductors. The Tcs test result of PFCN4 conductor is consistent with the calculated result used the strand scaling and the Tcs test result of PFCN3 conductor is a little larger than calculated result, whose maximum difference is about 0.2K. According to the SULTAN test result, the Tcs performance of both PFCN3 and PFCN4 conductor sample could meet the ITER requirement.

Carbon‐Coated LiTi2(PO4)3: An Ideal Insertion Host for Lithium‐Ion and Sodium‐Ion Batteries

We report the extraordinary performance of carbon-coated sodium super ion conductor (NASICON)-type LiTi2 (PO4 )3 as an ideal host matrix for reversible insertion of both Li and Na ions. The NASICON-type compound was prepared by means of a Pechini-type polymerizable complex method and was subsequently carbon coated. Several characterization techniques such as XRD, thermogravimetric analysis (TGA), field-emission (FE) SEM, TEM, and Raman analysis were used to study the physicochemical properties. Both guest species underwent a two-phase insertion mechanism during the charge/discharge process that was clearly evidenced from galvanostatic and cyclic voltammetric studies. Unlike that of Li (≈1.5 moles of Li), Na insertion exhibits better reversibility (≈1.59 moles of Na) while experiencing a slightly higher capacity fade (≈8 % higher than Li) and polarization (780 mV) than Li. However, excellent rate capability profiles were noted for Na insertion relative to its counterpart Li. Overall, the Na insertion properties were found to be superior relative to Li insertion, which makes carbon-coated NASICON-type LiTi2 (PO4 )3 hosts attractive for the development of next-generation batteries.

The Effect of Conductor Expressivity on Choral Ensemble Evaluation

Abstract Visual information can contribute significantly to the opinion one makes, the meaning one ascribes, and the interpretation one derives from musical information. An ongoing series of studies has examined whether a conductor’s use of gesture in a manner considered either “expressive” or “inexpressive” affects listeners’ evaluations of an ensemble performance. Prior results have indicated that among university music students instrumental performances led by conductors deemed to be expressive were evaluated more positively than those led by inexpressive conductors even when the performances were actually identical. The purpose of the present study was to determine whether a similar response pattern would be observed (a) among younger and less experienced music students and (b) for choral performance examples, as well as (c) to compare responses against evaluations of performances presented in an audio-only condition. Students (N = 429) enrolled in secondary level music classes rated the expressivity of two pairs of two identical choral performance excerpts (four excerpts in all) using a 10-point Likerttype scale. One group (n = 274) watched a video performance of the four excerpts featuring conductors who demonstrated either high-expressivity (HE) or low-expressivity (LE) conducting techniques. There was a significant effect of conducting condition on both the conductor and choral performance evaluations. When compared with the evaluations of a second group of participants (n = 155) who heard the same excerpts presented in an audio-only format, LE performance ratings were significantly lower; there was no difference between HE and audio-only ratings.

Prototype Nb3Sn Superconducting Strand for ITER CS Coil Conductor Produced in Korea Using the Internal-Tin Route

The ITER tokamak being constructed in southern France will incorporate a central solenoid (CS) coil consisting of 6 modules stacked one on top of the other. Each module will be constructed from round-in-square Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn based superconducting cable-in-conduit conductor (CICC). Production of CS conductor for the ITER tokamak had been delayed due to discoveries of faster than expected performance degradation. Investigations into mitigating this shortfall have included using internal-tin (IT) route Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strand in place of the bronze (BR) route strand that was originally proposed. Prototype ITER CS conductor samples have been produced using IT route Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strand in conjunction with cabling optimization, and conductor performance tests show that they satisfy ITER performance requirements. One of the suppliers of IT route ITER Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strand, which will be supplying superconducting strand for ITER CS conductor, is Kiswire Advanced Technology Ltd. (KAT) of Daejeon, Korea. The characteristics of their prototype Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strand for ITER CS conductor are presented. Furthermore, performance degradation of the CS strand due to possible strand deformations during the cabling process was also investigated. The results show similarities as well as differences with recent results obtained with BR route Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strand. However, direct interpretation of the strand deformation versus performance results may not lead to correct predictions of cable performance because of the strand contact interaction mechanism investigated.

Homogeneous performance and strain tolerance of long Bi-2223 HTS conductors under hoop stress

Two types of high-strength industrial Bi-2223 conductor, one laminated by copper alloy and the other laminated by stainless steel, have been tested to examine the effect of hoop stress on the transport property. The specimens (∼2 m long) were prepared by winding one layer around a GFRP mandrel and the measurements were made in a liquid helium bath with the hoop stress calculated from the BJR product applied by external magnetic field. A careful measurement wire configuration was necessary to cancel the noise pick-up from the environment for more accurate determination of Ic and n-value. We show for the first time that both conductors showed homogeneous voltage–current characteristics over a long length and degradations with hoop stress occurred uniformly, which is crucial information for the development of HTS magnet technology. The onset of degradation occurred at 200 MPa and 220 MPa, with additional bending stress present from the winding diameter of 108 mm, for copper alloy laminated and stainless steel laminated conductors, respectively. After considering the effect of bending strain, our result agrees well with the previously measured data.

Reversible and irreversible mechanical effects in real cable-in-conduit conductors

The strong strain sensitivity of the critical properties of Nb3Sn is well established. However, the roles played by both the reversible strain sensitivity and the susceptibility to brittle fracture of Nb3Sn filaments is still leading to unexpected results and resulting design modifications of conductors. Practical conductors require acceptance of less than perfect superconducting behaviour because such conductors actually operate continuously in a slightly resistive mode. Performance testing of the ITER conductors has provided a unique database of both strand and corresponding conductor performance. The test database includes strand characterization under uniaxial and bending strain, superconducting measurements on full-size conductor samples and microscopic investigations into filament fracture. A simple mechanical and electrical model of the strands and a multistage cable (capable of operation at 12 T and 45 kA) that focuses on predicting the imperfect superconducting behaviour is used to provide insight into the processes governing the observed conductor behaviour. The conclusions show that a short twist pitch at the first cabling stage provides the best operating conditions for the strands, and further that some strand mechanical properties, essentially a high stiffness to bending and a low stiffness to pinching, increase the ability of the strands to tolerate less well optimized cables.

High temperature heat treatment on boron precursor and PIT process optimization to improve the Jc performance of MgB2-based conductors

The promising results reported in our previous works led us to think that the production process of boron plays a crucial role in MgB2 synthesis. A new method for boron preparation has been developed in our laboratory. This particular process is based on magnesiothermic reaction (Moissan’s process) with the addition of an initial step that gives boron powder with nano-metric grain size. In this paper we report our efforts regarding optimization of the powder-in-tube (PIT) method for these nano-metric powders, and the resolution of problems previously highlighted such as the difficulty in powder packaging and the high friction phenomena occurring during cold working. This increases cracking during the tape and wire manufacture, leading to failure. Packaging problems are related to the amorphous nature of boron synthesized in our laboratory, so a crystallization treatment was applied to improve the crystallinity of the boron. To prevent excessive friction phenomena we synthesized non-stoichiometric MgB2 and used magnesium as lubricant. Our goal is the Jc improvement, but a global physical–chemical characterization was also made to analyse the improvement given by our treatments: this characterization includes x-ray diffraction, ρ(T) measurement, and SEM imaging, besides magnetic and transport Jc measurements.

Correlation between degradation and broadness of the transition in CICC

Cable in conduit conductor (CICC) performance is characterized in terms of relationships involving the electric field (E), voltage (V), temperature (T), current (I), magnetic field (B) and strain. Development of the electrical field in the V–T or V–I transitions in CICCs is exponential. These transitions plotted in the coordinates log E versus T or log E versus I look like straight lines. ITER Nb3Sn CICCs show degradation of properties versus load cycles that could be attributed to plastic deformation of the Nb3Sn strands or fracture of the superconducting filaments. The degradation is expressed in terms of the reduction of the current sharing temperature Tcs or critical current Ic, respectively. It was noticed long ago that degradation is accompanied by a significant broadening of the V–T or V–I transition, that looks like a change in the slope in the semi-log coordinate plot. This paper presents some systematic observations of correlations between the critical parameters and broadness of the transition in many CICCs. In most cases, the broadness of the transition seems to be a more sensitive indicator of the conductor damage even in cases where Tcs degradation is not clearly seen. Tcs degradation typically becomes obvious later in the cycling, especially after warm-up and following cool-down and more cycling. In some cases, a CICC manifests temporary or even a permanent growth of Tcs with load cycles, especially in the latest measurements of the CS conductors with short twist pitches. A possible mechanism of degradation that allows qualitative explanation of this phenomenon is discussed and is supported by the voltage measurements on the cable in the TFUS1 sample with the voltage taps penetrating the jacket to the cable.

Mechanical Behaviour of Multi-Span Overhead Transmission Lines Under Dynamic Thermal Stress of Conductors Due to Power Flow and Weather Conditions

Dynamic Thermal Rating (DTR) of overhead transmission lines represents a significant improvement with respect to the traditional criteria used to assess the steady-state ampacity of conductors. In fact DTR uses actual operating conditions of the power line, rather than assumed conservative conditions. This is extremely promising for the secure operation of the power system: with DTR, TSOs can fully exploit the dynamic performances of conductors, i.e. currents significantly higher than the steady-state thermal limits, in the meantime that the system is redispatched. The present paper proposes a novel dynamic model for calculating sags and tensions in a multi-span power line, for purposes of DTR. The model considers not only the mechanical interaction between spans, due to rotation of strings, but also that the temperature of conductors can vary by span, for different weather conditions. The problem was solved with a fast Newton-Raphson technique, rather than with conventional relaxation methods, in order to comply with the requirements of real-time operation. The developed tool is able to forecast the time trend of conductor temperatures, tensions, sags and clearances at each span, or to indicate which current can be carried for a given time, before a clearance or temperature constraint is violated. A case study compares the results of this novel method with the outcomes of the traditional ruling span technique.