Development and test results of the prototype active shield dipole magnets for the KEK B-Factory

A novel dipole magnet with an active shield coil has been developed as a candidate of the separation dipole in the interaction region of the KEK B-Factory. This is an iron-free magnet with an inner aperture of 113.8 mm diameter and a nominal field of 0.7 T. The main coil produces a field of 1.6 T, while the shield coil, which sits outside the main coil and has a current in the opposite direction produces a field of -0.9 T and suppresses the outside field to the level of 5 mT at a radius of 200 mm. Two prototype dipoles have been fabricated and tested. This paper summarizes the design, construction and test results of the dipoles.