High Field Accelerator Magnets Research Articles

Optimizing Secondary CLIQ for Protecting High-Field Accelerator Magnets

Optimizing Secondary CLIQ for Protecting High-Field Accelerator Magnets

Training-free demonstration of a 5.4 T Nb3Sn Canted–Cosine–Theta accelerator dipole impregnated with paraffin wax

Lawrence Berkeley National Laboratory is pursuing stress-managed Nb3Sn Canted–Cosine–Theta (CCT) magnet technology for high field accelerator magnets. Although promising results have been reported, improvements in the training performance are desired. This work describes the fabrication and testing campaigns of two subscale Nb3Sn CCT magnets; a baseline impregnated with National High Magnetic Field Laboratory Mix-61 and a magnet impregnated with paraffin wax. The paraffin magnet reached the short sample limit of the conductor, to within the measurement uncertainty, with no training quenches inside the magnet. In contrast, the baseline magnet reached 80% of the short sample limit after approximately 20 quenches and exhibits some loss of memory after thermal cycles. Inter-layer flexible quench antennas combined with voltage tap data show that all quenches appear identical and originate from a region corresponding to the location of peak field in the cable. Although this success should be replicated at higher fields, these first test results demonstrate the potential for training free Nb3Sn accelerator magnets operating near the short-sample limit.

A 6-around-1 cable using high-temperature superconducting STAR ® wires for magnet applications

To generate a dipole field above 20 T, we need high-temperature superconductors, including REBa2Cu3O 7−x (RE = rare earth, rebco) coated conductors. However, the optimal architecture of a high-current flexible rebco cable is not yet settled for high-field magnet applications. Here we report a 6-around-1 cable concept based on the high-temperature superconducting star ® wires. We made two cable samples. One had a single star ® wire and the other had six star ® wires. The cable with six star ® wires was 1.5 m long. It had a diameter of 5.7 mm and a pitch length of 52 mm. The critical current of the cable before bending was 1448 A at 77 K, retaining at least 77% of the total critical current from individual star ® wires. The cable had a low n value around 4.5. At a bend radius of 30 mm, the critical current and n value remained the same as before bending. The total resistance of electrical terminations was 61 nΩ at 77 K. The flexible and transposed 6-around-1 star ® cable can provide another route toward practical rebco conductors for high-field accelerator and fusion magnet applications.

FFT-Based Approach for the Mechanical Analysis of Superconducting Rutherford-Type Cables

Low-temperature superconductors are widely used in high field accelerator magnets, mostly within Rutherford type cables. We have proposed the “CoCaSCOPE” approach in order to build a numerical model of impregnated low-temperature Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn superconducting Rutherford-type cables dedicated to mechanical computation. Here the strand structure is described as a bi-metallic material: a copper core, a superconducting bundle region and an outer copper ring. In this paper, we explore the use of the distributed solver AMITEX_FFTP based on Fast Fourier Transform (FFT). The main interest of this method is to reduce the simulation time. This approach is investigated for structures with linear material behavior in this paper. This work compares the results from the FFT approach (using AMITEX) and from the 3D Finite Elements approach (using Cast3M). In this way, we can demonstrate the higher performances of FFT-based solving method compared to the finite elements method for multi-scale structure such as Rutherford-type cables in terms of computation time. With this approach, we can reduce the computation time or, alternatively, increase the size of our models in order to analyze the behavior of a macroscale model under mechanical solicitation.

Design and Assembly of a Large-Aperture Nb3Sn Cos-Theta Dipole Coil With Stress Management in Dipole Mirror Configuration

The stress-management cos-theta (SMCT) coil is a new concept which has been proposed and is being developed at Fermilab in the framework of US Magnet Development Program (US-MDP) for high-field and/or large-aperture accelerator magnets based on low-temperature and high-temperature superconductors. The SMCT structure is used to reduce large coil deformations under the Lorentz forces and, thus, the excessively large strains and stresses in the coil. A large-aperture Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn SMCT dipole coil has been developed and fabricated at Fermilab to demonstrate and test the SMCT concept including coil design, fabrication technology and performance. The first SMCT coil has been assembled with 60-mm aperture Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn coil inside a dipole mirror configuration and will be tested separately and in series with the insert coil. This paper summarizes the large-aperture SMCT coil design and parameters and reports the coil fabrication steps and its assembly in dipole mirror configuration.

Design Optimization, Cabling and Stability of Large-Diameter High Jc Nb3Sn Wires

In the framework of the High Field Magnets (HFM) program, CERN is developing and qualifying Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn Rutherford cables to support magnet development towards the requirements of a future energy-frontier collider, using both state-of-the-art commercial wires and experimental wires under development with industrial partners. The trend towards higher current density and larger diameter wires imposes challenges for magneto-thermal stability. In this study, rolling trials and Rutherford cabling have been performed at CERN for two designs of a 1 mm diameter distributed tin Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wire produced by KAT, and for 1 mm and 1.1 mm diameter RRP Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wires procured from Bruker OST, and the self-field stability and cabling degradation have been analyzed. The 1 mm RRP wire shows significant degradation in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_c</i> and stability on cabling. Although the latter is not expected to impact the performance of research magnets, the potential of heat treatment optimization to improve stability has also been quantified. The distributed tin wire shows substantially poorer stability, but promising indications of low cabling degradation. The influence of wire design characteristics on cabling behavior and stability have been assessed, and the implications for future wire optimization towards high field accelerator magnet applications have been discussed.

Model-Based System Engineering Framework for Superconducting Accelerator Magnet Design

The design specification of future high-field accelerator magnets require innovation in and integration of multiple disciplines. Numerical models underpin each step of the design. In this paper, we present a methodology for collaborative modeling based on relevant concepts of model-based systems engineering. The methodology is composed of three pillars: encapsulated computing environments with service query interface, model notebooks with auto-generated model views, and model query interface with results caching. The methodology aims at a de-centralized approach to multi-model and multi-scale collaboration that maintains the cornerstones of traceability and reproducibility. It is demonstrated with a multi-model coil design optimization of a high-field superconducting magnet.

Degradation of I c due to residual stress in high-performance Nb3Sn wires submitted to compressive transverse force

Future particle colliders in search for new physics at the energy frontier require the development of accelerator magnets capable of producing fields well beyond those attainable with Nb-Ti. As the next generation of high-field accelerator magnets is presently planned to be based on Nb3Sn, it becomes crucial to establish precisely the mechanical limits at which this brittle and strain sensitive superconductor can operate safely. This paper reports on the stress dependence and the permanent reduction of the critical current under transverse compressive loads up to 240 MPa in state-of-the-art restacked-rod-process (RRP®) and powder-in-tube Nb3Sn wires. Single-wire experiments were performed at 4.2 K in magnetic fields ranging between 16 T and 19 T on resin-impregnated samples to imitate the operating conditions of a wire in the Rutherford cable of an accelerator magnet. Depending on the wire technology, we measured irreversible stress limit values—defined as the transverse stress value, leading to a permanent reduction in the critical current of 5%, assessed by convention at 19 T—ranging between 110 MPa and 175 MPa. This permanent reduction of the critical current after mechanical unload can occur for two reasons, which can be concomitant: the plastic deformation of the Cu matrix that produces residual stresses on the Nb3Sn lattice and the formation of cracks. We developed a method to identify the dominant degradation mechanism in our experiments that allowed us to predict the fraction of critical current lost due to residual stresses. Interestingly, we found that in the RRP® wires the measured reduction of Ic after unload from stresses as high as 240 MPa can be fully ascribed to residual stresses. An independent confirmation of this conclusion coming from a study combining x-ray tomography and deep learning Convolutional Neural Networks is also reported.

Development of superconducting model dipole magnets beyond 12 T with a combined common-coil configuration

The superconducting magnet group at IHEP (the Institute of High Energy Physics, Chinese Academy of Sciences, China) has been engaging in the R&D of high field accelerator magnets since 2014 for the pre-study of the next-generation high energy particle accelerators like CEPC-SPPC (Circular Electron Positron Collider-Super Proton Proton Collider), FCC (Future Circular Collider), etc. A superconducting model dipole magnet named LPF1 was first fabricated with NbTi and Nb3Sn in a combined common-coil configuration in 2017 and tested in 2018, a main field of 10.23 T was reached within two 10 mm apertures. The magnet was reassembled with higher pre-stress in 2019 to investigate the influence of the pre-stress loading level on the performance of common-coil dipole magnets. The main field of this upgraded magnet named LPF1-S was increased to 10.71 T within two 12 mm apertures. By improving the key processing technologies in Rutherford cable fabrication, coil winding, Nb3Sn & NbTi splices soldering and coil impregnation, the recently fabricated model dipole magnet named LPF1-U attained a 12.47 T main field in two 14 mm apertures in 2021. To fully take advantage of Nb3Sn and NbTi superconductors in different field regions, LPF1-U was still designed and developed with a combined coil configuration with Nb3Sn for the inner two coils and NbTi for the outer four coils. Additionally, graded coil topology and different coil LSS (length of straight section) settings were adopted in the optimization of LPF1-U layouts. Bladder and key technology was used for the support structure, and fiber optic sensors based on FBG (fiber Bragg grating) were utilized to monitor the stress distribution and variation in the structures and coils through the whole process from magnet assembly to cool-down and excitation. During the performance test, a relatively large number of trainings were carried out and LPF1-U became more stable after the thermal cycle. A peak field of 12.7 T in the coils (12.47 T main field in apertures) corresponds to an operating current of 6865 A and a load line ratio of 90% was finally attained. It is worth mentioning that LPF1-U is the first hybrid—Nb3Sn, NbTi—common coil dipole magnet that has achieved a main field of more than 12 T in two apertures. The design, fabrication and performance analysis of the LPF series dipole magnets are presented in this paper.

Optimizing the use of pressurized bladders for the assembly of HL-LHC MQXFB magnets

The use of pressurized bladders for stress control of superconducting magnets was firstly proposed at Lawrence Berkeley National Laboratory in the early 2000s. Since then, the so-called ‘bladders and keys’ procedure has become one of the reference techniques for the assembly of high-field accelerator magnets and demonstrators. Exploiting the advantages of this method is today of critical importance for Nb3Sn-based accelerator magnets, whose production requires the preservation of tight stress targets in the superconducting coils to limit the effects of the strain sensitivity and brittleness of the conductor. The present manuscript reports on the results of an experimental campaign focused on the optimization of the ‘bladders and keys’ assembly process in the MQXFB quadrupoles. These 7.2 m long magnets shall be among the first Nb3Sn cryomagnets to be installed in a particle accelerator as a part of the High Luminosity upgrade of the LHC. One of the main practical implications of the bladders technique, especially important when applied to long magnets like MQXFB, is that to insert the loading keys, the opening of a certain clearance in the support structure is required. The procedure used so far for MQXF magnets involved an overstress in the coils during bladder inflation. The work presented here shows that such an overshoot can be eliminated thanks to additional bladders properly positioned in the structure. This optimized method was validated in a short model magnet and in a full-length mechanical model, becoming the new baseline for the series production at CERN Furthermore, the results are supported by numerical predictions using finite element models.

Uni-layer magnets: a new concept for LTS and HTS based superconducting magnets

A novel geometrical configuration to form a magnetic field perpendicular to an aperture, created by an asymmetric current distribution, within a single layer, and using a continuous ideal current line, named the uni-layer (UL) magnet, is here presented. The idea is compared to existing concepts in superconducting magnets, namely, the sector magnet, stress managed and canted . The UL magnet allows for a design with a continuous unit length (no layer jump), and an increased minimum bending radius of the conductor in relation to traditional and canted designs. The specific characteristics of the UL design are especially advantageous for strain-sensitive and prone to winding degradation high-temperature superconductors, in very high field accelerator magnet applications, in which, high efficiency in the use of conductor, and a small aperture are required. The advantages with regard to the design and fabrication of UL magnets in relation to other concepts are also discussed.

Design, fabrication, and characterization of a high-field high-temperature superconducting Bi-2212 accelerator dipole magnet

The use of high-field superconducting magnets has furthered the development of medical diagnosis, fusion research, accelerators, and particle physics. High-temperature superconductors enable magnets more powerful than those possible with Nb-Ti (superconducting transition temperature ${T}_{c}$ of 9.2 K) and ${\mathrm{Nb}}_{3}\mathrm{Sn}$ (${T}_{c}$ of 18.4 K) conductors due to their very high critical field ${B}_{c2}$ of greater than 100 T near 4.2 K. However, the development of high-field accelerator magnets using high-temperature superconductors is still at its early stage. We report the construction of the world's first high-temperature superconducting ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{x}$ (Bi-2212 with ${T}_{c}$ of $\ensuremath{\sim}82\text{ }\text{ }\mathrm{K}$) accelerator dipole magnet. The magnet is based on a canted-cosine-theta design with Bi-2212 Rutherford cables. A high critical current was achieved by an overpressure processing heat treatment. The magnet was constructed from a nine-strand Rutherford cable made from industrial 0.8 mm wires. At 4.2 K, it reached a quench current of 3600 A and a dipole field of 1.64 T in a bore of 31 mm. The magnet did not exhibit the undesirable quench training common in Nb-Ti and ${\mathrm{Nb}}_{3}\mathrm{Sn}$ accelerator magnets. It quenched a dozen times without degradation. The magnet exhibited low magnetic field hysteresis ($&lt;0.1%$) as measured by a cryogenic Hall sensor. It was fast cycled to 1.47 T at $0.54\text{ }\text{ }\mathrm{T}/\mathrm{s}$ without quenches. This work validates the canted-cosine-theta Bi-2212 dipole magnet design, illustrates the fabrication scheme, and establishes an initial performance benchmark.

A Preliminary Study on a New Epoxy Resin IR-3 for High-Field Superconducting Magnet Applications

Epoxy resins are commonly used in high field superconducting magnets for electrical insulation and mechanical reinforcement. However, many of the epoxy systems for vacuum pressure impregnation (VPI) techniques show drawbacks like easy cracking at low temperatures, short pot life, and/or low glass transition temperatures <formula><tex>$(T_g)$</tex></formula>. High-field dipole magnets are under development at the Institute of High Energy Physics (IHEP) for the pre-study of future high-energy accelerators. Finding the most appropriate epoxy is critically important. Herein, a new epoxy resin (named IR-3) is developed. Its potting properties including thermal shock, viscosity, <formula><tex>$T_g$</tex></formula>, and mechanical strength before and after radiation are presented and were compared with CTD-101K which is mostly used in accelerator magnets. Additionally, the thermal and electrical characteristics of high-temperature superconductor (HTS) coils encapsulated with these epoxies were also investigated. The results show that IR-3 is a promising encapsulating material for impregnating HTS coils and has the potential application in high field accelerator magnets

Development of a Small-Aperture Cos-Theta Dipole Insert Coil Based on Bi2212 Rutherford Cable and Stress Management Structure

The U.S. Magnet Development Program (US-MDP) is developing high-field accelerator magnets with magnetic fields beyond the limits of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn technology based on high temperature superconductor Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Sr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> CaCu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8-x</sub> (Bi2212). However, Bi2212 wires and cables are sensitive to transverse stresses and strains, which are substantial in high-field accelerator magnets. To prevent large degradation of the Bi2212 coils and achieve the required field quality, an innovative design which provides turn positioning during coil fabrication and operation and manage azimuthal and radial strains/stresses in the coil has been proposed at FNAL. This paper describes the development of a small-aperture two-layer Bi2212 dipole coil with stress management. The main parameters of the Bi2212 wire and Rutherford cable, the design of coil stress management structure and its plastic model, the coil mechanical analysis in the dipole mirror configuration are presented and discussed.

Using additive manufacturing technologies in high-field accelerator magnet coils

Recent advances with additive manufacturing (AM) technologies using various materials allow them to be considered for the manufacture of precise and complicated metal parts of the magnet coils of high field accelerator magnets from aluminum bronze, titanium alloy, stainless steel, etc. The 3D printing technology is also being used to fabricate prototype models of real parts to test and optimize their geometry. This paper discusses the designs of the complex stress-management coil parts developed at Fermilab, their fabrication using AM technologies, and quality control methods and results.

Study on Internal Strain Distribution of the High-Field Nb₃Sn Superconducting Accelerator Magnets With Homogenization Theory

To fabricate 10–16 Tesla high-field accelerator magnets, the high-Jc Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn superconductor is one of the most practical choices. However, it is a brittle material and is strain-sensitive. To reduce the potential Jc degradation of the conductor, it is crucial to accurately evaluate the stress of the coils owing to the large Lorentz force during magnet excitation. In the traditional stress analysis of magnets, the coils are usually regarded as homogenized structures using isotropic material coefficients; however, most superconducting (SC) coils have hierarchical and complicated structures. To obtain a more accurate estimation, it is necessary to consider the detailed internal structure of the coils during stress analysis. In this study, the homogenization method was applied to multi-scale stress analysis of a high-field accelerator SC magnet. The effective material coefficients of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn coils were calculated using this method. Stress analysis of the magnet was performed using the effective material coefficients and isotropic material coefficients for comparison. Compared with the result obtained using isotropic material coefficients, the Von-Mises stress of the coil using effective material coefficients is larger at different load steps. The stress level of most Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn filaments in the strand was higher than that of the coil. The maximum stress of the Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn filaments appeared in the strand contact regions. In addition, there was a significant difference in the average stress of all materials in the strand. These findings will help develop more accurate analysis and simulation models for high-field SC magnets.

Progress on Tests on Splices Between Nb3Sn Rutherford Cables for Graded High-Field Accelerator Magnets

Future high-field accelerator magnets foresee the extensive use of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn, more expensive than the Nb-Ti of LHC. For projects involving the series production of magnets, conductor grading is mandatory in order to reduce the cost. To allow grading, a splice between higher and lower grade cables must be implemented. The internal splice option, i.e., embedded in the winding pack, is the one considered in this manuscript. The magnet technology is Wind&React (W&R). The target resistance is 1 nΩ at a background field of B≈10 T and ratio between operational and critical current I/I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ≈1/3, the one at which such Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn dipoles are expected to work. This manuscript reports progress on ultrasonically welded, soldered and diffusion-bonded splices. The feasibility studies on ultrasonic welding between Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn Rutherford cables and strands is presented. The potential corrosive effect of fluxing agents of impregnated soldered samples is examined. In the end, the design and test in SULTAN of bent diffusion-bonded splices is reported.

Test of Superconducting Wires and Rutherford Cables With High Specific Heat

High-field accelerator magnets made of state-of-the-art Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn Rutherford cables demonstrate relatively long trainings due to sudden heat depositions originated by thermo-mechanical perturbations in the magnet coils. Coil sensitivity to these perturbations can be reduced by increasing the specific heat, C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> , of major coil components - strands, or whole cable, or epoxy. The R&D on all these three approaches is in progress. This paper studies feasibility of increasing the C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> of Rutherford-type cables by using a thin composite Cu/Gd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3 </sub> tape. The tape can be either wrapped around the cable, placed on the cable wide faces under the insulation, and/or inserted as a core. Cu/Gd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3 </sub> ribbons with ~30% of Gd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3 </sub> powder and two different thicknesses were produced by Hyper Tech Research, Inc. Wire and cable samples outfitted with these high-C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p </sub> ribbons, or tapes, were prepared and tested at FNAL for the Minimum Quench Energy (MQE). At 80%I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> , the MQE gain average over the tested magnetic field range of the NbTi cable with high-C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p </sub> tape on both sides was ~1.3. The MQEgain average of the NbTi wire wrapped with the high-C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p </sub> ribbon was 3.1.

Study on Reducing Magnetization Loss in CORC Cables By Laser Cutting Technology

Conductor on round core (CORC) cables with the features of flexibility and a high engineering current density have been a potential candidate for high magnetic field magnets and accelerator magnets. In these applications, reducing the magnetization loss generated in superconductors is essential in the process of design. CORC cables fabricated by multifilament-coated conductor (CC) tapes have been proved to have a low magnetization loss. However, the degradation of the critical current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) and additional coupling losses significantly affects the performance of CORC cables. In this article, ultraviolet laser cutting technology is used to scribe both the superconducting layer and copper stabilization layers into narrow filaments. First, the magnetization loss of a single tape with different numbers of filaments was measured by a calibration-free method. Then, based on the testing results of a single tape, two typical CORC cables are wound by 10-mm-wide and 4-mm-wide CC tapes. The magnetization loss of cables made of striated tapes was discussed by both experimental and numerical methods. It is found that the magnetization loss significantly decreases with an increasing number of filaments under a high background magnetic field. The magnetization losses decrease in CORC cables made of striated CC tape. Due to the reduced coupling loss and attenuated shielding effect, there is not much difference between the two values of the magnetization loss reduction rates in CORC cables and single tapes. The conclusions obtained in this article will be instructive for the future design of CORC cables.

Research and Development of Nb3Sn Wires and Cables for High-Field Accelerator Magnets

Research and Development of Nb3Sn Wires and Cables for High-Field Accelerator Magnets