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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

AC losses of Roebel and CORC ® cables at higher AC magnetic fields and ramp rates

We have measured ReBCO coated conductor-based conductor on round core (CORC ® ) and Roebel cables at 77 K in a spinning magnet calorimeter, which subjected the tapes in the samples to a radial magnetic field of 566 mT (peak) at frequencies up to 120 Hz (272 T s -1 , cyclic average) with an approximately sinusoidal waveform. The samples were oriented such that the field applied to the tapes within the cables was entirely radial, simplifying subsequent analysis. An expression for loss which included hysteretic, flux creep and eddy current losses was fit to both the CORC ® and the Roebel cables. This expression allowed easy comparison of the relative influence of eddy currents and flux creep (or power-law behavior) effects. The loss of both the CORC ® and Roebel cables measured here were seen to be essentially the sum of the hysteretic loss, flux creep effects, and the normal metal eddy current losses of the individual tapes. The losses of these cables were measured at high B × d B /d t with no coupling current loss observed under the present preparation conditions. The influence of flux creep effects on loss were not negligible. The losses of the CORC ® cable per meter of tape were seen to be reduced from the case of a flat tape because of the helical geometry of the tapes.

Physics↗
DOE OSTI2018

A Hybrid HTS/LTS Superconductor Design for High-Field Accelerator Magnets (Final Report)

This paper presents the design, construction, and test results of a hybrid dipole magnet. The inner coils were of second generation (2G) high-temperature superconductor (HTS) ReBCO tape and the outer coils were of low-temperature superconductor (LTS) Nb 3 Sn Rutherford cable. The HTS and LTS coils were independently powered and protected using different power supplies. The HTS coils were quenched many times with no degradation in performance observed. The hybrid field reached ~8.6 T, which is believed to be a record for a hybrid dipole. The maximum field was limited by the stable operation of the leads in the LTS coil at 8000 A. The HTS coils were independently ramped to 800 A, and the LTS coils to 10,000 A. With improved leads and instrumentation, this hybrid dipole is expected to produce over 13 T when the ReBCO tape in the HTS coil is aligned nearly parallel to the field. One major purpose of this program was to perform magnetization studies in the coils made with the HTS tape. Magnetization-induced field errors are expected to be small when the field is nearly parallel to the wide face of the tape. The magnetization measurements were performed at 77 K with the two racetrack coils in two orientations, with field predominantly either parallel or perpendicular to the wide face of the HTS tape. In addition, measurements were also performed at 4 K in different background fields provided by the outer Nb3Sn coils. This paper will summarize the magnetization measurements and present the quenching experience of the HTS coils in this hybrid magnet system.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2019

Measurements of the Strain Dependence of Critical Current of Commercial REBCO Tapes at 15 T Between 4.2 and 40 K for High Field Magnets

Interest for high magnetic fields (>16 T) for applications in high energy physics (HEP) and fusion machines, requires the development of high current cables capable to withstand the large forces, mechanical and electromagnetic, experienced during manufacturing and operations. The critical current (I c ) of REBCO tapes depends on strain, magnetic fields, and operational temperatures. Understanding how these parameters affect the I c of the conductor will be critical to develop robust high-current REBCO cables. However, there are limited reports on the strain dependence of I c , in particular at high fields and elevated temperatures relevant for future high-field compact fusion reactor magnets. We present here I c of commercial REBCO tapes measured as a function of compressive and tensile strain (between -0.6% and +0.65%) at high magnetic fields (12 and 15 T) and different temperatures (within 4.2-40 K). Results at 4.2 and 20 K showed less than 5% reduction in the normalized I c at high strain, while a stronger strain dependence was observed at 40 K. Samples tested at 12 T and 4.2 K showed similar strain dependence as 15 T and 4.2 K. In all tested conditions, the tape experienced reversible I c reduction in both tension and compression. Finite element analysis was used to predict the residual thermal strain accumulated in the REBCO layer prior of testing to account for the effect of the cooldown. A method was also developed to account for the current sharing observed between the sample and the sample holder during the ramp of the current. Our results provide useful input for the development of high-field fusion and HEP magnets using REBCO conductors.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Finite-Element Analysis of the Strain Distribution Due to Bending in a REBCO Coated Conductor for Canted Cosine Theta Dipole Magnet Applications

High-current cables using REBCO tapes can be used to develop high-field dipole magnets. However, the strain accumulated during cable fabrication and coil winding may reduce the critical current of the conductor. Therefore, it is important to properly consider the strain when designing high-field magnets. We used structural finite-element analysis (FEA) to predict the strain experienced by a REBCO tape during bending in configurations relevant to the fabrication of high-field accelerator magnets, in particular, the mechanical strain generated during cable fabrication and winding in a canted-cosθ dipole configuration. We considered two different cable options: (A) Flat tape that lay in the mandrel channel and (B) a REBCO tape helically wound around a circular copper core, the typical configuration of the conductor in round core cable (CORC). Strain accumulated during tape winding is studied for different core diameters and winding tilt angles. FEA longitudinal strain results were compared with the simulations for configuration A, where higher strain was observed experimentally. Configuration B was verified indirectly by comparing experimentally measured I c with the one predicted (based on the longitudinal strain) as a function of the bending diameter. Good agreement was found up to a bending diameter of 30 mm. The presented results will help to understand the impact of bending on REBCO tapes and CORC wires to develop high-field magnets.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

An electric-circuit model on the inter-tape contact resistance and current sharing for REBCO cable and magnet applications

REBCO coated conductor has demonstrated high current capacity that can enable high-field magnets for high energy physics and fusion applications. However, quench protection is still one of the main challenges to be addressed for these applications. In addition, Ic and n value variations along the length of REBCO tapes exist in commercial production. The inter-tape contact resistance plays a key role to develop the self protection capability in cables and magnets by enabling current sharing and suppressing excessive eddy currents. Here we propose an electric-circuit model to describe the inter-tape contact resistance and its impact on the current sharing between REBCO tapes. We report the experiments on a 2-stacked tape REBCO cable with local Ic drop to validate the model. With the developed model, we study the upper limit of the contact resistance which allows current sharing between tapes. We also study the impact of variation in Ic and n values in tapes on the cable performance. Finally, our model is expected to provide useful insight into the current sharing and target values for inter-tape contact resistance in REBCO cables and magnets for various applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

A Finite Element Study of Stress Reduction Techniques in REBCO HTS Conductor on a Round Cable (CORC) Cable

ReBCO high-temperature superconducting (HTS) tape is critical for achieving the high magnetic fields needed in next-generation particle accelerators. Enhancing the mechanical performance of ReBCO tape increases its critical current by reducing internal stress, especially in the superconducting layer. A finite element study examined how copper layer properties affect stress in ReBCO conductor on a round core (CORC) cables. The cable was modeled as a doubly supported beam under uniform compressive stresses."cable was modeled as a doubly supported beam under uniform load to simulate bending. A staged modeling approach from a single tape to a six-layer stack enabled validation and efficient parameter studies. Increasing the yield strength and Young s modulus of the copper layers reduced peak stress in the ReBCO layer. These results support development of improved tape stacks for high-field accelerator magnets

Mueller, Scott [Northern Illinois U.]↗
DOE OSTI2020

Superconductor with improved flux pinning at low temperatures

A REBCO superconductor tape that can achieve a lift factor greater than or equal to approximately 3.0 or 4.0 in an approximately 3 T magnetic field applied perpendicular to a REBCO tape at approximately 30 K. In an embodiment, the REBCO superconductor tape can include a critical current density less than or equal to approximately 4.2 MA/cm2 at 77 K in the absence of an external magnetic field. In another embodiment, the REBCO superconductor tape can include a critical current density greater than or equal to approximately 12 MA/cm2 at approximately 30 K in a magnetic field of approximately 3 T having an orientation parallel to a c-axis.

Selvamanickam, Venkat↗
DOE OSTI2022

Superconductor with improved flux pinning at low temperatures

A REBCO superconductor tape that can achieve a lift factor greater than or equal to approximately 3.0 or 4.0 in an approximately 3 T magnetic field applied perpendicular to a REBCO tape at approximately 30 K. In an embodiment, the REBCO superconductor tape can include a critical current density less than or equal to approximately 4.2 MA/cm2 at 77 K in the absence of an external magnetic field. In another embodiment, the REBCO superconductor tape can include a critical current density greater than or equal to approximately 12 MA/cm2 at approximately 30 K in a magnetic field of approximately 3 T having an orientation parallel to a c-axis.

Selvamanickam, Venkat↗
DOE OSTI2021

Characterization of edge damage induced on REBCO superconducting tape by mechanical slitting

Abstract Rare-earth barium-copper-oxide (REBCO) superconductors are high-field superconductors fabricated in a tape geometry that can be utilized in magnet applications well in excess of 20 T. Due to the multilayer architecture of the tape, delamination is one cause of mechanical failure in REBCO tapes. During a mechanical slitting step in the manufacturing process, edge cracks can be introduced into the tape. These cracks are thought to be potential initiation sites for crack propagation in the tapes when subjected to stresses in the fabrication and operation of magnet systems. We sought to understand which layers were the mechanically weakest by locating the crack initiation layer and identifying the geometrical conditions of the slitter that promoted or suppressed crack formation. The described cracking was investigated by selectively etching and characterizing each layer with scanning electron microscopy, laser confocal microscopy, and digital image analysis. Our analysis showed that the average crack lengths in the REBCO, LaMnO 3 (LMO) and Al 2 O 3 layers were 34 μ m, 28 μ m, and 15 μ m, respectively. The total number of cracks measured in 30 mm of wire length was between 3000 and 5700 depending on the layer and their crack densities were 102 cracks mm −1 for REBCO, 108 cracks mm −1 for LMO, and 183 cracks mm −1 for Al 2 O 3 . These results indicated that there are separate crack initiation mechanisms for the REBCO and the LMO layers, as detailed in the paper. With a better understanding of the crack growth behavior exhibited by REBCO tapes, the fabrication process can be improved to provide a more mechanically stable and cost-effective superconductor.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

A bi-layer barrier design for 122-type iron-based superconducting wires and tapes

Iron-based superconducting wires and tapes hold great promise for high-field magnet applications. A promising design for 122-type wires and tapes based on the powder-in-tube method is using silver and copper double-layer sheaths. For this design a heat treatment temperature below ~ 779 °C is required to prevent Ag-Cu liquid formation. However, this may be below the optimal heat treatment temperature for the critical current density, and still cannot prevent Ag-Cu interdiffusion occurring in the solid state. In this work we propose adding a niobium or tantalum or vanadium (or their alloys) barrier layer between the Ag and Cu to solve the Ag-Cu interdiffusion issue, given that the group-VB metals (vanadium, niobium, tantalum) are relatively inert to both Ag and Cu. To investigate the effectiveness of this design, BaFe 1.84 Co 0.16 As 2 wires and tapes with Ag/Cu and Ag/Ta/Cu sheaths, as well as Ba 0.6 K 0.4 Fe 2 As 2 wires and tapes with Ag/Cu and Ag/Nb/Cu sheaths, were fabricated. It was found that both the Ta and Nb layers kept integral after wire drawing, but after a large flat-rolling reduction the Ta layer broke while the Nb layer kept integral. In the tapes with Ag/Cu sheaths (without the Ta or Nb layer) Cu diffused through the Ag layer and into the powder cores during 740 °C heat treatment, while in the tapes with Ag/Nb/Cu sheaths the Nb layer effectively blocked Ag-Cu interdiffusion even at 900 °C. Further, this work demonstrates that Ta is a suitable barrier material for 122-type wires, while Nb is suitable for both wires and tapes. In this design using Ag/Nb (or Ta)/Cu sheaths, we can regard the outer Cu as the conductor matrix while the Ag and Nb (or Ta) serve as two layers of barriers that suppress reactions between the components. Thus, we call this design a “bi-layer barrier” design for 122-type wires and tapes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Fusion Development and Technology (Final Technical Report for FC02-93ER54186)

The project is divided into three major tasks: 1) Magnet R&D i) Magnets Task 1 - Development of HTS Twisted Stacked-Tape Cable (TSTC) conductors for high field, high current magnets ii) Magnets Task 2– Development of Cryogenic Magnet Cooling Technology iii) Magnets Task 3 - National and International Collaboration 2) Electron Cyclotron Heating (ECH) of plasmas 3) FNSF Liquid Metals Study.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Rapid assessment of REBCO CC angular critical current density J c (B, T = 4.2 K, θ) using torque magnetometry up to at least 30 tesla

Abstract Detailed design of REBa 2 Cu 3 O 7 − x (REBCO)-based magnets ideally relies on knowledge of the full angular and wide temperature range characterization of the critical current I c of the REBCO coated conductors (CC) at high magnetic fields. In practice, however, obtaining I c ( B , T , θ ) data by the commonly used electrical transport technique is expensive, tedious, and difficult, due to high critical current values that exceed 2000 A for B | | a b -plane ( θ = 90 deg). The conductors are often damaged during angular transport measurements at angles approaching the ab -plane. Therefore, so far, REBCO magnets have been designed without full I c ( B , T , θ ) data sets. Here, we present J c ( B , T , θ ) results for more than twenty samples of CC all made to the same advanced pinning specification produced by SuperPower Inc. For this, we employed torque magnetometry, benchmarking the results to transport I c measurements mostly made away from ab -plane, finding good agreement with scaling factors ≈1–1.3. What is striking is the huge variety of properties exhibited by the samples, even for CC made recently. Given the huge attention now being paid to the effects of screening currents and to the torques generated by offsets between the tape plane and the local magnetic field vector, our data set suggests some caution in detailed design of such magnets without having data of the type presented here.

Physics↗
DOE OSTI2019

AMS-100: The next generation magnetic spectrometer in space – An international science platform for physics and astrophysics at Lagrange point 2

The next generation magnetic spectrometer in space, AMS-100, is designed to have a geometrical acceptance of 100 m 2 sr and to be operated for at least ten years at the Sun–Earth Lagrange Point 2. Compared to existing experiments, it will improve the sensitivity for the observation of new phenomena in cosmic rays, and in particular in cosmic antimatter, by at least a factor of 1000. The magnet design is based on high temperature superconductor tapes, which allow the construction of a thin solenoid with a homogeneous magnetic field of 1 Tesla inside. The inner volume is instrumented with a silicon tracker reaching a maximum detectable rigidity of 100 TV and a calorimeter system that is 70 radiation lengths deep, equivalent to four nuclear interaction lengths, which extends the energy reach for cosmic-ray nuclei up to the PeV scale, i.e. beyond the cosmic-ray knee. In conclusion, covering most of the sky continuously, AMS-100 will detect high-energy gamma-rays in the calorimeter system and by pair conversion in the thin solenoid, reconstructed with excellent angular resolution in the silicon tracker.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

AC loss and contact resistance in REBCO CORC ® , Roebel, and stacked tape cables

Abstract Many high-temperature superconductor (HTS) applications require superconducting cables with high currents while operating in an alternating magnetic field. HTS cables should be composed of numerous superconducting tapes to achieve the required current capacity. Alternating current and magnetic fields cause AC losses in such cables and can provoke conductor instability. AC losses and contact resistances were measured of several cable designs based on commercially available REBCO tapes at the University of Twente. The AC loss was measured under identical conditions for eight REBCO conductors manufactured according to three types of cabling methods—CORC ® (Conductor on Round Core), Roebel, and stacked tape, including a full-size REBCO CICC (cable in conduit conductor). The measurements were done at T = 4.2 K without transport current in a sinusoidal AC magnetic field of 0.4 T amplitude and frequencies from 5 to 55 mHz. The AC loss was measured simultaneously by calibrated gas flow calorimeter utilizing the helium boil-off method and by the magnetization method using pick-up coils. Also, the AC loss of two CORC® conductors and a Roebel cable was measured at 77 K. Each conductor was measured with and without background field of 1 T. The measured AC coupling loss in the CORC ® and Roebel conductors is negligible at 4.2 K for the applied conditions while at 77 K coupling loss was observed for all conductors. The absence of coupling loss at 4.2 K can be explained by shielding of the conductor interior; this is confirmed with measurement and calculation of the penetration field of CORC ® and Roebel cables. The inter-tape contact resistance was measured for CORC ® and stacked tape samples at 4.2 and 77 K. It was demonstrated that a short heat treatment of CORC ® conductor with solder-coated tapes activates tape-to-tape soldering and decreases the contact resistance. The reduction of contact resistance by two orders in magnitude to tens of nΩm is comparable with the interstrand contact resistance in ITER Nb 3 Sn type conductors.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Forced flow cooling of high field, REBCO-based, fusion magnets using supercritical hydrogen, helium, and neon

Rare Earth Barium Copper Oxide (REBCO) High Temperature Superconductor (HTS) tapes are being considered for the Toroidal Field (TF) magnets of a highly compact, high field fusion reactor operating at magnetic fields as high as 21 T and operating temperatures in the range of 10–30 K. Due to the increase in range of operating conditions made available through HTS tapes, a new set of cryogenic fluids are being considered for forced flow cooling. The present study investigates helium, hydrogen, and neon as a forced flow coolant for REBCO HTS tapes used in a highly compact, high-field reactor design. Four design criteria are considered, including current sharing temperature, fluid inlet temperature, cable pressure drop (dP), and operating pressure. From these simulations, neon is removed from consideration due to its high required pressure drop and low temperature margins with respect to the current sharing limit. Helium and hydrogen are then compared, with hydrogen producing the highest overall heat transfer rate at its optimum operating condition (1.5 MPa/15 K). A compromise across inlet temperature, dP, and operating pressure is found when helium has a minimum initial temperature of 10 K and an inlet pressure of 2.0 MPa. For the current design, helium is selected as a coolant due its acceptable cable pressure drop, required cooling load, and system complexity inherent to a forced-flow cryogenic system.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Berkeley Lab Finite Element Framework (BELFEM) v0.1

The software program, referred to as BELFEM, is a specialized finite element code designed for the magnetodynamic modeling of high-temperature superconducting (HTS) tapes. It incorporates novel mixed finite element formulations, particularly the h-ϕ-formulation with thin-shell simplification, to efficiently simulate larger geometries. This methodology is extremely promising for predicting the electrodynamic performance of HTS tapes used in superconducting cables and magnets, offering the benefit of reduced computational cost. Compared to similar technologies like COMSOL Multiphysics and GetDP, BELFEM's performance benchmarking indicates superior efficiency in its thin-shell implementation. In the future, it will also support features like thermal coupling and inter-tape current sharing, enhancing its utility in research and development, particularly in nuclear fusion applications. The intent is to develop BELFEM as a robust and efficient tool for the HTS community, contributing to the analysis and design of superconducting cables and magnets.

Messe, Christian↗