Development of a 40 mm bore magnet cross section with high field uniformity for the 6.6T SSC dipole

The SSC requires a very uniform dipole field. A 40 mm bore diameter winding cross section has been developed which has computed multipole coefficients less than 1 × 10
^-6
of the dipole field at 10 mm radius for an operating field of 6.6T at 4.35 K. This cross section has 4 conductor blocks (3 wedges, 16 turns) per quadrant in the inner layer, and two blocks (1 wedge, 20 turns) in the outer layer. "Partially keystoned" cable is used; the inner cable has 23 strands of .0318 inch diameter wire; the outer cable has 30 strands of .0255 inch diameter wire. Model magnets have been constructed and the fields measured at room temperature and at liquid helium temperature up to fields exceeding 6.6T. Measured fields are compared to the predicted field. In addition, the as-built conductor positions in several magnets have been determined after cutting up the magnets. The predictions based on as-built configurations are computed and compared to measurements.