Design of an active shield dipole magnet in the interaction region of the KEK B-Factory

Due to their detrimental effect on the experimental detector of the KEK B-Factory, the leakage fields of the bending magnets, which will be installed near to the collision point, need to be as small as possible. For achieving this smaller leakage field, the authors propose a special superconducting dipole with a shield coil. A novel approach for achieving a leakage field of less than 5 mT at a radius of 200 mm, based on an active shield method, has been investigated. The design concept of the coil, which consists of a main coil and a shield coil having an opposite current to the main coil, has been developed. The coil design and the structure of the magnet are described