The common coil design is a 2-in-1 design for collider dipole magnets where not only the yoke but the coils are also common to the two apertures. It is based on simple (mostly flat racetrack) coil geometry with large bend radii. The bend radius is determined by the spacing between the two apertures rather than the size of aperture itself. It is a conductor friendly design suitable for brittle conductors. The common coil design is particularly attractive for high field magnets as coils move as a whole, causing much smaller stress/strain on the conductor in the end region under large Lorentz forces. Therefore, there is a potential to significantly reduce the amount of expensive support structure as much larger deflections can be tolerated. Good field quality magnetic designs have been developed. The design facilitates modular geometry which is good for mixing different conductors both in R&D magnets and in large scale production of hybrid magnets. One major goal of the current high field magnet R&D program is to develop designs that can produce lower cost magnets in industry. The common coil design is expected to produce lower cost magnets since the number of coils required is half (as they are shared between two apertures), since it requires less structure (since large deflections may be allowed) and since it allows lower cost production techniques (because of simpler geometry). The common coil design is also expected to produce magnets with better performance due to less strain on the conductor. The presentation will review the common coil design, the performance of a number of common coil magnets and future prospects.
