High Precision Superconducting Magnets

Window-frame type superconducting dipole magnets have demonstrated accuracy and predictability of fields which compare well with the best conventional accelerator-type magnets. Precision measurements were made on the two series powered 2 m long 4 T modules comprising the 80 bending magnet at BNL after two years of beam operation including several dozen beam induced quenches. The integral field of the two units is identical to measurement accuracy, ?? 1 ?? 10-4 parts at ~ full aperture, for all multipoles except quadrupole. Random quadrupole terms of G/B = 6 ?? 10-5 cm-1 or 2 ?? 10-4 parts are present. A 1 m long 6 T model of more advanced design shows pure dipole field, at all field levels, to 1 ?? 10-4 parts, using a single correction coil with predetermined excitation. The field shape at ~ 0.5 T/sec rise rate is identical to dc. The advantages of the extended current sheet coil construction are discussed. Results will be compared with computer simulations of construction errors. Suitable conceptual designs of compact 6 T dipoles and of quadrupoles applied to a 1 km accelerator lattice will be presented.