Feasibility Study of a No-Insulation REBCO Magnet for Persistent Mode Operation

A no-insulation solenoid magnet for persistent mode operation has been designed and constructed. The closed loop assembly used a 172-m-long REBCO superconducting tape, including 130 m for the magnet, 6 m for the switch, and 36 m for the soldered joints. The solenoid coil is of 30 mm ID, 68 mm OD, 40 mm length, 840 turns in 105 layers, and inductance of 20 mH. The assembly of magnet, switch, and joint has been operating in a persistent mode with a field decay rate of 18.8 ppm/h at the temperature of 30 K. Its operating current is 88.35 A, to achieve the designed central magnetic field of 1.5 T. The circuit resistance is 1.04 × 10
^-10
Ω, calculated from the inductance and field decay rate.