  A new superferric magnetic storage ring with highly homogeneous field at 1.45
T and weak electrostatic focussing is described which has been set up at the
Brookhaven National Laboratory (BNL), USA, for a precision measurement of the
magnetic anomaly of the muon. The toroidal storage volume has a radius of 7 m
and a diameter of 9 cm. Precision magnetic field determination based on pulsed
NMR on protons in H$_2$O yields the field to better than 0.1 ppm everywhere
within the storage region. Follow on experiments using the setup have been
already suggested to search for a finite mass of the muon neutrino and to
search for an electric dipole moment of the muon with significantly increased
accuracy. The high homogeneity of the field suggests the usage of such devices
as a mass spectrometer for heavier particles as well.
