Cold iron cos θ magnet option for the SSC

In this paper we review first the evolution over the past several years of a cold iron, high field cos θ magnet design option for the SSC. WIe note the collaborative approach pursued by BNL and LBL on the 2-in-1 option, and the culmination of this effort in the tests of the BNL 4.5 m model magnets. Next, we discuss the subsequent l-in-l option being pursued jointly by BNL, Fermilab and LBL. During the initial period, 1983-84, the cold iron SSC program progressed in several stages, all based on the 2-in-I (two coils in a common iron yoke) concept: first, and basically a BNL effort, a 2-in-1 dipole of 3.2 cm aperture was developed, to accommodate either NbTi or Nb₃Sn to achieve an eventual field of 6.5 T to 7.5 T, respectively. We designate this SSC Design Ao. A modified version of this later became the workhorse of the BNL/LBL collaboration, namely a geometrically similar dipole of 4.0 cm aperture, based on the high homogeneity NbTi conductor then under development at the University of Wisconsin and with industry, with an expected field of about 6. 5 T. This magnet was featured in SSC Reference Design A. Finally, in the last quarter of 1984 Design A underwent an important modification, with the addition of stainless steel collars. This collared 2-in-1 dipole of 4.0 cm aperture we designate SSC Design A´. Meanwhile, a parallel development of an ironless cos θ magnet at Fermilab, described in an earlier paper by E. Fisk, became the basis for Reference Design B, a medium-field SSC option. In the winter of 1984-85, the three laboratories, in order to minimize technical options at this stage and to more efficiently use scarce R&D funds, adopted a common cos θ cold iron design incorporating the nost promising features of Designs A´ and B. This paper ends with a brief status report of this SSC Design D option, a l-in-l cold iron, collared dipole of 4.0 cm aperture which is expected to achieve 6.5 T.