REBCO coated conductors maintain high engineering current density above 16 T at 4.2 K. That fact will significantly impact markets of various magnet applications including high-field magnets for high-energy physics and fusion reactors. One of the main challenges for the high-field accelerator magnet is the use of multitape REBCO cables with high engineering current density in magnet development. Several approaches developing high-field accelerator magnets using REBCO cables are demonstrated. In this paper, we introduce an alternative concept based on the canted cos θ (CCT) magnet design using Conductor on Round Core (CORC R) wires that are wound from multiple REBCO tapes with a Cu core. We report the development and test of double-layer three-turn CCT dipole magnets using CORC R wires at 77 K and 4.2 K. The scalability of the CCT design allowed us to effectively develop and demonstrate important magnet technology features such as coil design, winding, joints and testing with minimum conductor lengths. The test results showed that the CCT dipole magnet using CORC R wires was a viable option in developing REBCO accelerator magnet. One of the critical development needs is to increase the engineering current density of the 3.7 mm diameter CORC R wire to 540 A mm −2 at 21 T, 4.2 K and to reduce the bending radius to 15 mm. This would enable a compact REBCO dipole insert magnet to generate a 5 T field in a background field of 16 T at 4.2 K.

Engineering current density over 5 kA mm −2 at 4.2 K, 14 T in thick film REBCO tapes To cite this article: Goran Majkic et al 2018 Supercond. Sci. Technol. 31 10LT01 View the article online for updates and enhancements. Related content Critical current density above 15 MA cm2 at 30 K, 3 T in 2.2 m thick heavily-doped (Gd,Y)Ba2Cu3Ox superconductor tapes V Selvamanickam, M Heydari Gharahcheshmeh, A Xu et al.-Sample and length-dependent variability of 77 and 4.2 K properties in nominally identical RE123 coated conductors L Rossi, X Hu, F Kametani et al.-Requirements to achieve high in-field critical current density at 30 K in heavilydoped (Gd,Y)Ba2Cu3Ox superconductor tapes V Selvamanickam, M Heydari Gharahcheshmeh, A Xu et al.-Recent citations Goran Majkic-Correlation of In-Field Performance of Thick REBCO Films Between 0-14 T and 4.2-77 K Goran Majkic et al-Effect of Deposition Temperature on Microstructure and Critical Current Properties of Zr-Doped GdYBCO Superconducting Tapes Made by MOCVD Ziming Fan et al

High-temperature superconductors (HTS) could enable high-field magnets stronger than is possible with Nb-Ti and Nb 3 Sn, but two challenges have so far been the low engineering critical current density J E , especially in high-current cables, and the danger of quenches. Most HTS magnets made so far have been made out of REBCO coated conductor. Here we demonstrate stable, reliable and training-quench-free performance of Bi-2212 racetrack coils wound with a Rutherford cable fabricated from wires made with a new precursor powder. These round multifilamentary wires exhibited a record J E up to 950 A/mm 2 at 30 T at 4.2 K. These coils carried up to 8.6 kA while generating 3.5 T at 4.2 K at a J E of 1020 A/mm 2 . Different from the unpredictable training performance of Nb-Ti and Nb 3 Sn magnets, these Bi-2212 magnets showed no training quenches and entered the flux flow state in a stable manner before thermal runaway and quench occurred. Also different from Nb-Ti, Nb 3 Sn, and REBCO magnets for which localized thermal runaways occur at unpredictable locations, the quenches of Bi-2212 magnets consistently occurred in the high field regions over a long conductor length. These characteristics make quench detection simple, enabling safe protection, and suggest a new paradigm of constructing quench-predictable superconducting magnets from Bi-2212.

No abstract

Abstract-Magnet programs at BNL, LBNL and FNAL have observed instabilities in high J c Nb 3 Sn strands and magnets made from these strands. This paper correlates the strand stability determined from a short sample-strand test to the observed magnet performance. It has been observed that strands that carry high currents at high fields (greater than 10T) cannot sustain these same currents at low fields (1-3T) when the sample current is fixed and the magnetic field is ramped. This suggests that the present generation of strand is susceptible to flux jumps (FJ). To prevent flux jumps from limiting stand performance, one must accommodate the energy released during a flux jump. To better understand FJ this work has focused on wire with a given sub-element diameter and shows that one can significantly improve stability by increasing the copper conductivity (higher residual resistivity ratio, RRR, of the Cu). This increased stability significantly improves the conductor performance and permits it to carry more current.