1 Abstract— Common coil magnets are a promising option for post LHC hadron colliders. Fermilab, in collaboration with LBNL, is involved in an R&D program to develop 11 T, 30-40 mm aperture, common coil dipoles. The use of Nb 3 Sn wound after reaction is chosen in order to address cost reduction that is a key issue for future hadron colliders. The common coil design concept allows a large bending radius at the coil ends and is well suited to the react-and-wind technique with brittle superconductors. Conversely the horizontal component of the magnetic forces in a common coil is larger than the radial component in a shell type layout, imposing demanding requirements on the mechanical structure. Both a 2-layer and a single layer design have been studied. The development of the program is presented focusing on the mechanical designs and assembly techniques. R&D activities and plans are also presented. Index Terms—Accelerator, superconducting magnet. I. INTRODUCTION ERMILAB is involved in an R&D program [1] aimed at developing 11 tesla 2-in-1 dipole magnets for future hadron colliders. As part of this effort a block type common coil with Nb 3 Sn coils using the React & Wind technique is under development. Several different designs were analyzed [2] in order to understand the main characteristics of block type common coil magnets from various points of view: magnetic design, mechanical design, and protection. The common denominator of this study was to look for simple designs (for instance avoiding auxiliary coils) with accelerator field quality. The study started with the development of a small bore (30 mm), 2-layer hybrid magnet (Fig.1), using NbTi in the outer layer, and evolved into a larger bore (40 mm) 1-layer design using a wide cable (Fig.2). Mechanical designs of the hybrid dipole were studied, exploring both a vertically and horizontally split yoke. The 1- layer magnet employs a novel type of collar and vertically split yoke, using a new assembly technique. Magnetic designs and quench protection study are presented elsewhere [3]-[6]. Table I reports main features of both designs (Jc = 1800 A/mm2 @ 12 T 4.2 K and Cu/nonCu = 0.85). Manuscript received Sept 17, 2000. This work was supported by the U.S. Department of Energy. G. Ambrosio , N. Andreev, E. Barzi, P. Bauer, D. Chichili, K. Ewald, L. Imbasciati, V. Kashikhin, S.W. Kim, P. Limon, I. Novitski, A. Zlobin are with Fermilab, Batavia, IL, 60510 USA (telephone: 630-840-2297, e-mail: giorgioa@fnal.gov). G. Sabbi, R. Scanlan are with LBNL, Berkeley, CA 94720 USA. J. Ozelis is with Jefferson Lab. Newport News, VA 23606 USA. Fig. 1. 2-layer hybrid common coil The 1-layer design has been chosen because of the larger aperture, the lower inductance and the more simple assembly. The engineering design is near finalization. This paper describes the main features and conclusions of the development of the 2-layer hybrid magnet, the conceptual design of the 1-layer dipole, its assembly technique and mechanical design. The broader R&D effort including a conductor development program, the production of practice coils and the fabrication and test of a racetrack magnet is reported. First results are mentioned as well. TABLE 1. MAGNET PARAMETERS. 2 layers 1 layer Max Field T 11 10.5 Max Current kA 15.3 24.5 Aperture mm 30 40 (50) Coil area cm 2 22.4(i) 31.2(o) 53.4 Inductance @11T mH/m 5.4 2.8 Max Temperature K 330 300 Max Voltage V 300 75 Fig. 2. Single layer common coil Development of React & Wind Common Coil Dipoles for VLHC G. Ambrosio, N. Andreev, E. Barzi, P. Bauer, D. Chichili, K. Ewald, L. Imbasciati, V. Kashikhin, S.W. Kim, P. Limon, I. Novitski, J.P. Ozelis, R. Scanlan, G. Sabbi, A.V. Zlobin F