Fabrication of a variable- field-direction superconducting magnet

Magnetic field direction often greatly influences material properties, such as critical current densities of tape-shaped superconductors. To determine the influence of this parameter, an object is usually rotated in a fixed magnetic field, which is not always effective. We are developing a variable-field-direction superconducting magnet that can change its field direction continuously in a 2D plane. Two sets of split-pair coils are placed perpendicular to each other, and the perpendicular magnetic fields generated by each split-pair coil are superimposed. By independently controlling the operating current of each split-pair coil, we can continuously change the direction of the superimposed magnetic field. Four solenoid coils were wound with Nb-Ti conductors. This magnet is designed to rotate a field of 1 T. The field homogeneity is estimated to be less than 1% in a 10 mm-diameter sphere volume. This is a conduction-cooled superconducting magnet employing 4K-GM refrigerators. We constructed a cryostat with two types of room-temperature bores and conducted a cooling test without solenoid coils and supporting structures was conducted.