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

Abstract

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.

Defining optimal thickness for maximal self-field Jc in YBCO/CeO2 multilayers grown on buffered metal

“…High-temperature superconductor YBa 2 Cu 3 O 6+x (YBCO) thin films and coated conductors hold great potential for a variety of power applications, energy storage, high-speed computing etc [1][2][3][4][5], but to realize their full capability, the overall critical current density (J c ) needs to be maximized [6,7]. Since the thermal excitation of Cooper pairs and the field strength dependent Meissner effect greatly affect the J c , it is essential to design specific structures for various applications operating at different temperatures and magnetic fields.…”

Development of the first Tesla class iron-based superconducting coil for high field application

“…At present, the high field insert coil technology represents a crucial approach to achieving a stable state of strong magnetic field condition. Numerous fully superconducting magnets worldwide adopt the configuration of high-temperature superconducting coils inserted into lowtemperature superconducting magnets [16,17].…”

Numerical analysis of the electromechanical behavior of high-field REBCO coils in all-superconducting magnets

“…Despite the improvements in high-field magnets arising from the use of CCs, the screening current associated with the variation of the transverse magnetic field constitutes a major problem in practical magnets. Experiments and modeling [13][14][15][16][17][18] have shown that the screening current plays a role in reducing the total magnetic field and creating field spatial distortion. Furthermore, the decay of the screening current with time can lead to a temporal drift issue in the magnetic field due to thermally induced flux creep [17,19,20].…”

“…Experiments and modeling [13][14][15][16][17][18] have shown that the screening current plays a role in reducing the total magnetic field and creating field spatial distortion. Furthermore, the decay of the screening current with time can lead to a temporal drift issue in the magnetic field due to thermally induced flux creep [17,19,20]. All these effects are detrimental to the performance of NMR magnets [17,21].…”