Special Quadrupole Magnets for KEKB Interaction Region

Because of the limited beam separation, normalconducting quadrupole magnets with special shape were required for KEK B-factory (KEKB) interaction region. We have developed, tested and installed the six special shape magnets, five of these are full quadrupole magnets with field free space for the other beam. And the rest one is a half quadrupole magnet. These magnets have to meet the severe specifications such as high current density and good field distributions over a large aperture. We describe here the design and the preliminary field measurement results.