A large 5 Tesla superconducting solenoid unquestionably transcends present experience in magnet design. It has been suggested that mechanical considerations lead to an upper limit of about 60 T2m for the figure-of-merit B2R for superconducting solenoids. For the solenoid for the proposed SiD detector at the ILC this quantity is 62.5 T2m, suggesting that the feasibility of such a magnet is best determined by appeal to experience and careful engineering extrapolation where required. The CMS solenoid, nearing completion at the CERN Large Hadron Collider, will provide a 4 T field in a bore 5.9 m in diameter and 13 m long. This magnet provides a substantial proof-of-concept for the SiD solenoid. The CMS conductor consists of a 32-strand NbTi cable, stabilized by a co-extrusion of high-purity aluminum, which is welded to two bars of strong aluminum alloy. CMS achieves its design field with four winding layers; SiD will require six layers using the same conductor. The smaller aspect ratio (magnet length divided by diameter) of SiD vs. CMS -- approximately one for SiD but more than two for CMS -- means that more linear current density than simple proportionality of the higher field is required. CMS operates at 19.5 kilo-Ampères (kA) and its windings provide a linear current density of approximately 3500 A/mm; SiD requires 4800 A/mm, a factor of almost 1.4 more than CMS for a field only 25% more intense

Description of the work done to date in a contribution (pdf) to the Genoa conference.