Cable-in-conduit conductor concept for the GEM detector magnet

A conceptual design for a conductor based on cable-in-conduit (CIC) technology is presented for application to the proposed GEM detector magnet for the Superconducting Super Collider. The conductor design is driven by the enormous scale of the magnet, which will be composed of two coil halves each approximately 19 m in diameter and 14 m long. Each coil half will be assembled from 12 winding modules, each comprising of a single layer winding. The nominal operating current of 50 kA generates a central field of 0.8 T and a peak field at the winding of 1.6 T. Although the field requirements are low and operation is DC, the CIC concept is preferred because of its large intrinsic stability. The GEM detector requires the highest level of stable, quench-free operation to minimize risk and maximize reliability. The conductor consists of a 450 strand multistage cable made from NbTi/copper composite wires enclosed in a stainless steel tube which is surrounded by a large rectangular block of low resistivity aluminum. The aluminum sheath offers quench protection for the 2.5-GJ coil system, while the fast transient stability is provided by copper in the strand and the supercritical helium inside the conduit. Details of the conductor design, operating performance, and manufacturing process are described.<>