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ISSN: 2772-8307
Copyright © 2026 Shanghai Jiaotong University. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
cited:15
Development of a novel joint-less double aperture REBCO magnet with an innovative excitation circuit for stable magnetic field generation
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Article Number:Article 100139
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Abstract
Corresponding email:huangdaxing@mail.iee.ac.cn; guhw@mail.iee.ac.cn; dingfazhu@mail.iee.ac.cn
Second-generation high-temperature superconducting (2G-HTS) magnets operating in persistent current mode (PCM) effectively address the challenge of magnetic field stability. This paper introduces a novel joint-less double aperture (JDA) REBa2Cu3O7−δ (REBCO, RE: rare earth) magnet, designed to overcome the limitations posed by joint resistance in traditional 2G-HTS magnets. A single slit REBCO tape is innovatively wound into double-pancake (DP) coils on both sides and placed in spaced apertures within the magnet. This closed-loop design generates two stable magnetic fields while effectively preventing tape twisting between the DP coils. Furthermore, a new portable excitation circuit is proposed for the JDA REBCO magnet, utilizing pulsed magnetic fields generated by the copper coil, which eliminates the need for current leads, electrodes, and persistent current switches (PCSs), significantly reducing system complexity. Initially, a traditional PCS was used to charge the JDA REBCO magnet to 40 A at 77 K, generating a magnetic field of 60.6 mT at the center of one of the DP coil apertures. The magnet was then successfully excited using a pulse circuit after about 200 cycles. A comparative analysis with the PCS results showed that the current induced by the pulse circuit was approximately 40 A. The stability of the magnetic field within one DP coil of the JDA REBCO magnet was monitored for 107 h, with a magnetic field drift rate of approximately 0.86 ppm/h. The closed-loop advantage of the JDA REBCO magnet, combined with the portable pulsed excitation circuit, demonstrates the promising potential for applications in double aperture magnetic resonance imaging (MRI) equipment, particle accelerators, and other advanced technologies.
cited:42
Quench behaviors of parallel-wound no-insulation high temperature superconductor coils
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Article Number:Article 100140
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Abstract
Corresponding email:yawei.wang@sjtu.edu.cn
No-insulation (NI) high-temperature superconducting (HTS) coil wound with parallel-stacked tapes emerges as a prospective choice for high-field fusion magnets owing to lower inductance and faster ramping rate. The parallel stacked-tape structure leads to new current redistribution among stacked tapes in each turn during local quenches, which also considerably changes the current redistribution behavior through inter-turn contacts. Therefore, quench behaviors of parallel-wound no-insulation (PWNI) coil should differ from its counterpart wound with single tape, which are still unknown. This study is to illustrate quench behaviors of PWNI HTS coils induced by local hot spot. A multi-physics model integrating an equivalent circuit network, a FEM heat transfer module, and a FEM T-A model is developed to analyze the electromagnetic and thermal characteristics of PWNI HTS coils during quench. Results show that the transport currents are mainly redistributed among parallel-stacked tapes through terminal resistances when a local hot spot happens on one tape, while being less dependent on turn-to-turn electrical contacts. It leads to a coupling current within PWNI coils that is not present in NI coils wound with single tape (single-wound no-insulation (SWNI) coil), resulting in a highly non-uniform transport current distribution among parallel-wound tapes. The reduced terminal joint resistances further enhance the coupling current, potentially leading to an extra overcurrent quench risk in PWNI coils. Moreover, the current redistribution between parallel-stacked tapes inhibits the turn-to-turn current redistribution in the PWNI coil, thus significantly reducing its magnetic field degradation under a high heat disturbance, which can be almost less than half of the SWNI counterpart in this study. These results offer important theoretical guidance to safety operation and robustness improvement of high-field HTS magnets wound by PWNI technique.
cited:12
Superconducting materials − tools to combat with climate change
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Article Number:Article 100113
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cited:17
Suppression of flux avalanches in YBCO superconducting thin films by coating metal investigated using magneto-optical imaging
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Article Number:Article 100101
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Abstract
Corresponding email:zhangxingyi@lzu.edu.cn
Flux avalanches, prevalently existing in superconducting thin films, can cause catastrophic breakdowns of electromagnetic properties and even irreversible damage to superconducting materials. Metal coating is an effective way to suppress the flux avalanches in superconducting thin films. Nevertheless, it is difficult to reveal the suppression mechanisms due to the challenge of effectively separating the simultaneous eddy currents and heat exchange in the metal coating. In this work, the eddy currents and heat exchange in the Ag metal coating are separated by setting a thermal insulation layer, and its inhibiting effect on the flux avalanches of the YBCO superconducting thin films is elucidated. The results indicate that eddy currents play an important part in suppressing magnetic flux avalanches, and their effect strengthens with increasing Ag thickness. Meanwhile, employing the double-exposure method, the flux avalanche velocity of YBCO superconducting thin films was measured, revealing a significant decrease in the magnetic flux avalanche velocity due to suppression by eddy currents. Moreover, a theoretical model was established to investigate the influence of eddy currents on the motion of a single vortex, and the calculated results showed good agreement with the experiments. These findings provide a better understanding of the flux avalanches and their suppression in YBCO superconducting thin films.
Abstract
Corresponding email:kumuds@barc.gov.in
The Proton Improvement Plan (PIP)-II project is part of Fermilab’s upgrade of its proton accelerator complex, to provide a powerful, high-intensity proton beam to the laboratory’s upcoming research program. The project includes an 800 MeV superconducting (SC) linear accelerator (linac), with five flavours of cavities and cryomodules. The medium energy section of the linac contains two types of superconducting Single Spoke Resonator (SSR) RF cavities (SSR1 and SSR2), which are interleaved with strong solenoid focusing lenses. A unified design of the solenoid has been developed, with one solenoid design satisfying both SSR1 and SSR2 requirements. The integral focusing strength requirement of 4.5 T2m with a full width half maximum (FWHM) of 180 mm indicates the peak field strength ∼ 6.8 T in the magnet aperture, necessitating a superconducting design within the limits of NbTi as magnet wire strand. These are complex combined units that include one focusing solenoid with bucking coils to minimize fringe fields and four corrector coils each, with independent current leads to produce dipole and quadrupole fields. To simplify the current lead design and reduce complexity, the project opted conduction cooling for these magnets, thus requiring a redesign compared to previous prototype bath cooled units. Existing designs for high energy accelerators adopt bath cooled design of the solenoid focusing lenses for medium energy cryomodules. The present design explores a unique and technically superior solution for the cryomodule operation by decoupling the magnet and cavity cooling to certain extent. Reliability in cryomodule operations shall be studied after integration of magnets in the Linac beamline. Here we discuss the design requirements, challenges, electromagnetic design, superconducting wire selection and the results from magnetic measurements of the first pre-series units.
cited:18
Numerical simulations on the AC loss of REBCO stacks under rotating magnetic fields
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Article Number:Article 100111
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Abstract
Corresponding email:jfang@bjtu.edu.cn; Zhenan.Jiang@vuw.ac.nz
AC loss presents a significant challenge for high-temperature superconducting (HTS) rotating machines. To date, the behaviour of total AC loss (Qtol) (with current) and magnetization loss (Qm) (without current) in a single HTS tape under rotating magnetic fields (RF) have been explored. However, a research gap remains in understanding how these findings translate to the more complex HTS windings of rotating machines. Further exploration is needed to understand the loss behaviour of more complex HTS structures, such as HTS stacks. In this work, Qtol and Qm, in the HTS stacks under RF and a perpendicular AC standing wave magnetic field are numerically investigated. Two different RF models are considered: one is the Uni-RF model, characterized by a uniform field with equal field amplitudes and phases at each position, and the other is a non-uniform field created by a rotating Halbach array, referred to as the Hal-RF model. The dependence of AC loss on parameters such as the number of tapes in the stacks, tape width (2a), and the inclination angle (α) of tapes, which refers to the angle between the normal direction of the stack and the vertical direction, have been explored. The number of tapes in the stacks ranges from 1 to 16, α ranges from 0° to 90°, and the tape width includes 4 mm and 40 mm. Additionally, different rotating field directions are also considered. Interestingly, the analytical values from Brandt and Indenbom equation for Qm of a superconducting strip (BI-strip) are close to Qm results of the stacks under the standing wave at high fields, while they are over twice as high as those in the Hal-RF model at 1 T. This suggests the BI-strip equation is not reliable for predicting Qm under RF at high fields. We also show in the Hal-RF model that different rotation directions of the field lead to varying Qm and Qtol when asymmetric Jc (B, θ) data are applied. Moreover, it has been observed that the inclination angle has no impact on Qm under uniform RF while significantly impacts both Qm and Qtol in the Hal-RF model.
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