Ultraprecise superferric storage ring magnet for the Muon G-2 experiment

A new measurement of the anomalous magnetic moment (G-2 factor) of the muon to a precision of 0.35 p.p.m. is being undertaken with the AGS at Brookhaven National Laboratory. It will involve a precision superferric storage ring with a magnetic field of 1.5 T and a radius of 7 m for 3.1 GeV/c muons. The magnetic field in the storage region must be homogeneous to one part in 10⁶ and the effective field averaged around the ring must be known to 1 part in 10⁷. The design status of the superferric storage ring and of the techniques planned for magnetic-field control and measurement are presented. Perturbation field calculations for the iron and coil configuration, considerations on the superconducting coil, shimming and measurement techniques, and plans for a test magnet program are discussed.