35.4 T field generated using a layer-wound superconducting coil made of (RE)Ba2Cu3O7−x (RE = rare earth) coated conductor

Abstract

To explore the limits of layer wound (RE)Ba 2 Cu 3 O 7-x (REBCO, RE = Rare Earth) coils in a high magnetic field environment > 30 T, a series of small insert coils have been built and characterized in background fields. One of the coils repeatedly reached 35.4 T using a single ~100 m length of REBCO tape wet wound with epoxy and nested in a 31 T background magnet. The coil was quenched safely several times without degradation. Contributing to the success of this coil was the introduction of a thin polyester film that surrounded the conductor. This approach introduces a weak circumferential plane in the coil pack that prevents conductor delamination that has caused degradation of several epoxy impregnated coils previously made by this and other groups.The cuprate based high temperature superconductor (RE)Ba 2 Cu 3 O 7-x (REBCO, RE = Rare Earth), has the capability to substantially transform the technology of high field magnet systems. So far, the low temperature superconductors Nb-Ti and Nb 3 Sn have been used for virtually all superconducting high field magnets. Their maximum field, however, is limited by their upper critical fields (H c2 ) of about 15 T for Nb-Ti and 30 T for Nb 3 Sn, which limits their highest practical field to about 23.5 T 1 . This limit is imposed by the rapid decrease in critical current density J c as H c2 is approached. By contrast, REBCO has an H c2 that exceeds 100 T at 4.2 K, removing the H c2 and J c limit that restricts usage of Nb 3 Sn in highfield magnet systems. One of the goals at the NHMFL is to develop the necessary technology for the next generation of high-field magnets including Nuclear Magnetic Resonance (NMR) quality magnets. To reduce the number of resistive joints and achieve the required field homogeneity for NMR, layer-winding

Strongly enhanced vortex pinning from 4 to 77 K in magnetic fields up to 31 T in 15 mol.% Zr-added (Gd, Y)-Ba-Cu-O superconducting tapes

“…%Ti wires, in which α-Ti precipitates yield significant pinning enhancement. 21 F p (H//c) for the 15% Zr-doped film at 77 K is comparable to that of optimized Nb-Ti at 4.2 K, which is ∼16.9 GN/m 3 at ∼5 T. Strikingly, H irr (77 K) ∼14.8 T for the 15% thin film is even higher than the H irr ∼ 11 T of Nb-Ti at 4.2 K. An earlier work using BaSnO 3 and BZO has achieved F p (H//c) > 25 GN/m 3 but peaking at somewhat lower field and without any H irr (T) measurement. 16 J c (H//c) at 4.2 K and H up to 31.2 T of both 7.5 and 15 mol.…”

“…We ascribe the excellent pinning performance at high temperatures to the high density (equivalent vortex matching field ∼7 T) of self-assembled BZO nanorods, while the low temperature pinning force is enhanced by large additional pinning which we ascribe to strain-induced point defects induced in the REBCO matrix by the BZO nanorods. Our results suggest even more room for further performance enhancement of commercial REBCO coated conductors and point the way to REBCO coil applications at liquid nitrogen temperatures since the critical current density J c (H//c) characteristic at 77 K are now almost identical to those of fully optimized Nb-Ti at 4 Thanks to its high critical temperature T c , high critical current density J c , high irreversibility field H irr , and moderate anisotropy parameter γ , REBa 2 Cu 3 O x (REBCO, where RE = rare earth) thin films grown on flexible and mechanically strong substrates can exceed the temperature and field application limits of the Nb-based low temperature superconductors, and enable superconducting applications in a broad temperature and magnetic field regime now exceeding 35 T at 4 K. [1][2][3] However, further J c and H irr enhancement and anisotropy reduction are strongly desirable for compelling, costeffective applications, and especially to enable multi-Tesla fields in a temperature regime of 30-77 K. [4][5][6] Enhanced vortex pinning is needed both to raise higher temperature irreversibility fields and to raise J c so that overall conductor current density J E can reach the required high values of the order of 500 A/mm 2 . Adding higher densities of nanoscale defects with strong vortex pinning properties is the most efficient strategy.…”

Fabrication of 1 T Bi-2223 superconducting magnet with 92 mm bore diameter at 77 K

“…On the other hand, REBa 2 Cu 3 O x (RE-123; RE:rare earth) coated conductor tape is used and insert magnet for high magnetic field generation is fabricated [9]. Degradation of the performance of RE-123 double-pancake coil due to epoxy impregnation is investigated and it is found that dry winding and paraffin impregnation suppress degradation [10].…”

Testing of machine wound second generation HTS tape Vacuum Pressure Impregnated coils

“…It has been reported by some workers that testing of second generation tape sometimes resulted in delamination of the tapes when using resin based insulation systems for wound coils [4][5][6][7]. One proposed root cause is the differential thermal contraction between the coil former (the mechanical structure upon which the coil is wound) and the resin encapsulated coil turns resulting in the tape caxis (direction normal to tape length and widest tape face) tensile stress being exceeded.…”