Speaker
Description
NHMFL is designing a 40 T superconducting user magnet [1]. In this magnet, significant quantity of REBCO coated conductor will be used for the insert coils. Fully characterizing critical current (Ic) of REBCO tapes at temperatures of its operation (4.2 K) and during a potential magnet quench (> 4.2 K) is critical to the success of the project. Due to the strong anisotropy of REBCO coated conductor, critical current is much higher when sample’s ab plane is nearly parallel to the magnetic field, which is the case in most parts of our magnet. However, the conventional transport Ic measurement suffers from sample burn-out due to the high current. The newly developed Ic measurement method by torque magnetometry [2],[3] overcomes this difficulty and provides a more efficient measurement solution.
In this work, we measured Ic vs field angle for samples obtained from over 70 spools. Ic was measured in magnetic field up to 15 T with angles from -60 degrees to + 60 degrees from ab plane at 4.2 K. In addition, several samples were measured at 10 – 50 K in magnetic field up to 30 T. We compared the results with transport Ic measured at 4.2 K in magnetic field at 18 and 8 degrees off the ab plane of REBCO. We studied the reproducibility of the measurement. The factors influence the measurement accuracy are discussed.
Reference
[1] H. Bai, M.D. Bird, L. Cooley, I.R. Dixon, K.L. Kim, D.C. Larbalestier, W.S. Marshall, U.P. Trociewitz, H.W. Weijers, D.V. Abraimov, G.S. Boebinger, “The 40 T Superconducting Magnet Project at the National High Magnetic Field Laboratory,” IEEE Transactions on Applied Superconductivity, vol. 30, no. 4, pp. 1-5, 2020.
[2] J. Jaroszynski, A-M. Constantinescu, G. Miller, A. Xu, A. Francis, T. Murphy and D. C. Larbalestier,, ‘Rapid assessment of REBCO CC angular critical current density Jc(B, T = 4.2 K, θ) using torque magnetometry up to at least 30 tesla’, 2022 Supercond. Sci. Technol. 35 095009.
[3] J. J. Jaroszynski, G. Miller, D.C. Larbalestier, A-M. Constantinescu, ‘Magnetometer for large magnetic moments with strong magnetic anisotropy’, US Patent No. 12,181,540.
Acknowledgement
This work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement No. DMR- 2128556, DMR- 2131790, and the State of Florida, and by DMR-1644779 through User Collaborations Grants Program Project #5206.
