Evaluation and Analysis of a 10 T-Class Small Coil Using REBCO Coated Conductors Laminated With Thick Copper Tapes

In 2013, we successfully developed a 5 T full REBCO cryogen-free superconducting magnet (CSM) with a 200 mm room temperature bore using thick copper laminated REBCO coated conductors (CCs) for quench protection. Based on the same protection concept, we have investigated the feasibility of a 10 T-class CSM using thick copper stabilized REBCO CCs. In this study, a 10 T-class small test coil with a 50 mm bore was fabricated, and the validity of the magnet design was verified through excitation tests and numerical calculations. Consequently, it was confirmed the test coil was successfully energized up to 500 A and 9.6 T without any abnormal voltages. The coil critical current I-c obtained experimentally at different temperatures agreed well with the values predicted numerically from the I-c(B,theta,T) measurement data for a typical REBCO CC. We also confirmed that the experimental results for the screening-current-induced magnetic field (SCIF) are in good agreement with the numerical calculations using the same I-c(B,theta,T) data. This indicates less variation in the in-field I-c characteristics of our REBCO CCs. Finally, quench tests were performed on the test coil with different post-quench decay time constants. There was no degradation of the coil even at a time constant equivalent to the magnet design, confirming that our thicker copper design is capable of providing quench protection.