Common Coil Dipoles for Future High Energy Colliders

This paper presents several magnetic designs for a 16-T 50-mm aperture Nb3Sn dipole based on the common coil design for a future circular collider. It has an aperture-to-aperture spacing of 250 mm, a yoke outer diameter of 700 mm, and uses a similar or less conductor amounts than cosine theta or block designs. All field harmonics are about an order of magnitude better than specified at the design field and well below the specification in the entire range of operation. Initial results of mechanical design and analysis are also encouraging. They indicate that the proposed structure is able to support the pole coil blocks against the vertical Lorentz forces and that the maximum stresses in all coils remain generally below 150 MPa. Given several inherent advantages of the common coil design, the development presented here should make this approach a leading candidate for very high field magnets in future colliders.