Bi-Sr-Ca-Cu-O conductors and magnets at high stress-strain levels

We focus on a react and wind Bi-2223 conductor with a pure silver matrix. The stress-strain-critical current relation is determined for coils with a uniform stress distribution, at 4.2 K and 19 T. Somewhat surprisingly, the coils fail at a Lorentz force induced strain value close to the value for uni-axially loaded straight samples. This implies that bending strain is only partially retained due to the plastic nature of the pure silver matrix. Also, a double-pancake coil with a 15 mm winding thickness, resulting in a non-uniform stress distribution, is tested at 4.2 K and 19 T. The coil current is cycled with increasing peak values and the onset and evolution of critical current degradation in the coil is shown.