Characteristics of REBCO Coated Conductors for 25 T Cryogen-Free Superconducting Magnet

A 25 T cryogen-free superconducting magnet is under development at the High Field Laboratory for Superconducting Materials (HFLSM), Institute for Materials Research (IMR), Tohoku University. Fujikura has manufactured and supplied REBCO coated conductors for the 25 T cryogen-free superconducting magnet. In-field critical current (I_c) properties in high magnetic fields at lower temperatures below 20 K and mechanical properties are important for design of these superconducting magnets. However, there is insufficient data of I_c properties in high magnetic fields above 15 T. In this work, in-field I_c properties at 20 K, 15 T of several samples cut from commercial coated conductors are evaluated at HFLSM, IMR, Tohoku University. The correlations between I_c at 20 K, 15 T and I_c at 77.3 K are compared. As a result, it is confirmed that I_c at 20 K, 15 T have a stronger correlation with in-field I_c at 77.3 K rather than I_c at 77.3 K, self-field. In addition, tensile strengths at 77.3 K of more than 30 samples of coated conductors are also evaluated.