A Two-Level Undercut-Profile Substrate for Chemical-Solution-Based Filamentary Coated Conductors

Wulff, Anders Christian; Lundeman, Jesper Holm; Hansen, Jørn Bindslev; Mishin, Oleg; Zhao, Yüe; Mohajeri, Roya; Grivel, Jean‐Claude

doi:10.1109/tasc.2016.2536938

Cited by 7 publications

(5 citation statements)

References 16 publications

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“…The two-level undercut-profile substrate (2LUPS) approach was developed by Wulff et al [149][150][151][152]. It constitutes a bottom-up process that employs chemical etching/polishing directly on the metal substrate to produce shading 3D profiles prior to the CC stack deposition.…”

Section: Bottom-up Processesmentioning

confidence: 99%

Topical Review: Multifilamentary coated conductors for ultra-high magnetic field applications

Wulff

Abrahamsen

Insinga

2021

Supercond. Sci. Technol.

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High-temperature superconducting coated conductors (CCs) are considered an enabling ultra-high field (UHF) tape-conductor technology due to their extremely high engineering current densities at very high magnetic fields and low temperatures, and high mechanical strength. A major challenge is however related to induction of problematically large superconducting screening currents (as an effect of the large width-to-thickness ratio) when the wide tape conductors are exposed to strong transverse magnetic fields above 20 T, which is the case in many UHF magnet systems. Subdividing the superconducting layer into narrow parallel decoupled filaments has been shown to effectively reduce superconducting screening currents by a factor comparable to the number of filaments. The filamentization is however not effective until the induced coupling currents flowing across the filaments have decayed. The effectiveness of the multifilamentary structure in suppressing coupling currents and reducing the decay time constants is directly linked to potential current paths between filaments. Very recent experimental and numerical studies have examined both the challenge of magnet precision, caused by screening-current-induced fields, and the fatal consequences of local uneven tape stresses exceeding the irreversible limits for commercial CCs. These studies have conclusively revealed that screening currents must not be ignored in the mechanical design and other studies have introduced multifilamentary CCs as a viable solution. This paper aims to review the efforts made in developing and investigating multifilamentary CCs for ultra-high field applications focusing on the screening-current-related mechanisms, critical system-level effects, effectiveness of filamentization in UHFs, fabrication and large-scale analysis of multifilamentary CCs, in addition to providing cost estimates of previously studied filamentized CC fabrication techniques.

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Section: Bottom-up Processesmentioning

confidence: 99%

Topical Review: Multifilamentary coated conductors for ultra-high magnetic field applications

Wulff

Abrahamsen

Insinga

2021

Supercond. Sci. Technol.

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“…This magnetic system consists of a hollow cylinder having internal radius RI , external radius RO, and axial length Lz. The direction of magnetization is given bŷ e = cos(φ)êr + sin(φ)ê φ (1) This distribution has the purpose of generating a magnetic field oriented along the x direction inside the bore of the cylinder. As can be seen in Fig.…”

Section: Halbach Cylindermentioning

confidence: 99%

“…For these applications, though the tape geometry does pose several challenges with respect to field homogeneity and stability due to screening current decay and complex persistent mode operation. The former can be mitigated by subdividing the HTS tape into a number of fine filaments [1,2,4,3]. Persistent mode operation requires manufacturing of superconducting joints between multiple HTS tapes (REBCO-based) and it has been demonstrated [5,6] that such technology is greatly advancing.…”

Section: Optimal Design Parameters and Comparisonmentioning

confidence: 99%

Comparison of Superconductors and Permanent Magnets for Small-scale Magnetic Resonance Imaging Devices

et al. 2020

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In this feasibility study we use finite element method simulations to compare superconductors (SC) coils and permanent magnets (PM) assemblies as main field source for a small-scale magnetic resonance imaging scanner. The motivation behind this investigation is that for certain tissues, e.g. knee ligament, diagnosis can be performed with equipment operating with relatively weak magnetic fields. It is then interesting to assess whether the relaxed field requirement enables alternative technologies, which present some advantages over the well-established helium-cooled low-temperature superconductors.As prototypical magnetic systems we consider the Helmholtz coil and the Halbach cylinder for the SC and PM cases, respectively. Each possibility is simulated over a wide range of combinations of the fundamental design parameters. We estimate field strength, field homogeneity, and total cost over the service life of the device. From these figures of merit we evaluate the optimal combinations of design parameters. Finally we compare the SC and PM systems and we establish the range of field requirement values for which one alternative is more suitable than the other one.The result of the present investigation provides the starting point for more detailed studies where more specific design considerations are taken into account.

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“…However, the hysteresis losses associated with AC applications need to be reduced by subdividing the SC tape into smaller filaments, and possibly transposition of the filaments as in Roebel cables or CORC cables [2]. The two level undercut-profile substrate (2LUPS) geometry is a way to subdivide the tape into filaments without reducing considerably the engineering-critical current [3], [4]. In this work we present a magnetic characterization approach based on vibrating sample magnetometry, and we apply the method to 2LUPS samples and non-filamented reference samples.…”

Section: Introductionmentioning

confidence: 99%

Lift-Factor Analysis of Multifilamentary Coated Conductor Produced Using Two Level Undercut-Profile Substrates

Insinga

Solovyov

Usoskin

et al. 2019

IEEE Trans. Appl. Supercond.

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Here we present a detailed characterization of the critical current density of YBa2Cu3O7−x (YBCO) two level undercut-profile substrate (2LUPS)-based samples made at the Technical University of Denmark (DTU) using Hastelloy substrate. The CC architecture was produced at Bruker HTS by means of alternating beam assisted deposition (ABAD) and pulsed laser deposition (PLD). The magnetization of different samples having all the same size, but with various numbers of filaments, including a non-filamentary reference sample have been measured in applied magnetic fields up to 16 T and at temperatures ranging from T = 2 K to 77 K. A simple multiple rooftop model is proposed to estimate the critical current density of the filaments and it has been observed that filaments of 0.25 mm and 0.5 mm width are providing similar critical current densities in the order of Jc ≈ 2.3 MA/cm 2 at T = 4.2 K and B = 10 T as well as the reference samples without filaments. This result indicates that the filaments have been fabricated with no degradation of the superconductor and that the filaments are decoupled with non-superconducting material. Finally, the lift factor of the critical current Ic with respect to T = 77 K and self field of the 2LUPS samples is estimated. This is reaching 10 at T = 4.2 K and B = 10 Tesla.

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A Two-Level Undercut-Profile Substrate for Chemical-Solution-Based Filamentary Coated Conductors

Cited by 7 publications

References 16 publications

Topical Review: Multifilamentary coated conductors for ultra-high magnetic field applications

Topical Review: Multifilamentary coated conductors for ultra-high magnetic field applications

Comparison of Superconductors and Permanent Magnets for Small-scale Magnetic Resonance Imaging Devices

Lift-Factor Analysis of Multifilamentary Coated Conductor Produced Using Two Level Undercut-Profile Substrates

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