Estimation of Joint Resistance in REBCO Single-Turn Loop Under Magnetic Fields

The technological development for a 3-T high-temperature superconducting (HTS) magnetic resonance imaging (MRI) magnet is underway. The 3-T HTS MRI magnet is imaged such that RE(= Rare Earth)Ba2Cu3O7-delta (REBCO) coils are installed and cooled using a cryocooler between 30 and 50 K without liquid helium refrigerant. REBCO MRI magnets are expected to maintain the magnetic field with stability better than 0.1 ppm/h with superconducting joints for a persistent-current mode. The resistance in a joint must be suppressed less than 1 x 10(-12) Omega to achieve the expected stability. The resistance of REBCO joint was estimated measuring the decay rate of trapped magnetic field in a REBCO single-turn loop including a joint. An external magnetic field of up to 1 T was applied to the joint in the STL at temperatures of 35 K and 50 K. The order of resistance in the REBCO joint was less than 1 x 10(-13) Omega.