Abstract: A method for successfully heat treating magnet coils of braided Bi2Sr2Ca1Cu2Ox (Bi-2212) strand. The Bi-2212 coil is fabricated using standard round wire powder-in-tube techniques, and braided with a ceramic-glass braid with integrated carbonaceous binder. The coil is heated in an atmosphere controlled furnace below the high current density phase reaction sequence to burn off the carbonaceous binder and evacuated to remove unwanted gases from the inner windings. The oxygen environment is then reintroduced and the coil is heat treated to the high Jc reaction temperature and then processed as normal. As the local atmosphere around the surface of the wire, particularly the concentration of oxygen, is critical to a successful reaction sequence, high current Bi-2212 coils can thereby be obtained.

Abstract: A superconducting magnetic sensor having a sensing coil is provided with one or more superconducting discs for adjusting the effective area of the coil. The effective area of the coil is adjusted by varying the position of the superconducting disc relative to the associated coil. In a superconducting gradiometer having a pair of sensing coils coupled in series opposition, three superconducting discs are arranged to provide effective area adjustment along three mutually orthogonal axes. Coarse and fine adjustment are optionally provided by employing two sets of superconducting discs, one set fixed, the other adjustable.