Feasibility studies and manufacturing experience on the GEM Magnet conductor are presented, including all components-NbTi strand, cable, conduit manufacture, cable pulling, and aluminum sheath application.<>

The GEM Detector magnet at the Superconducting Super Collider is built in two halves each of which is comprised of 12 single layer superconducting coil modules wound on a 19 m mean diameter and joined with a low resistance lap joint employing the superconducting strands and a copper stabilizer. Each joint half is attached to the sheathed, cable-in-conduit conductor end, and assembly of the mating halves is completed in the field. The target resistance per joint is 5 x 10(-10) OMEGA at an operating current of 50 kA. Details of the joint design, its cooling and results of tests on prototypical sub- and full-scale models using superconducting strands are presented.

The GEM test coil, will be wound from 70 m of conductor identical to that used in the full scale magnet. The coil configuration will duplicate the field distribution of the full scale magnet and current control will duplicate full scale current decay characteristics. Therefore, quench/protection analysis of this coil will reveal very important information about the behavior of the full scale model. Due to the uncertainty associated with the contest between the cable, the conduit and the sheath, a parametric analysis has been performed in order to determine and bracket the behavior. With no electrical contact the quench evolves normally until, due to heat transfer from the sheath into the cable, the superconductor temperature becomes critical and the entire length becomes normal. >

Spectrometer magnets for use in satellite and balloon-borne cosmic ray experiments are subject to strict limits on mass and volume. Typically, the particle detectors are mounted adjacent to the outer boundary of the magnet package, rather than within its bore. Optimizing the distribution of ampere-turns radically, in a high alpha, low beta winding cross section places more ampere-turns in closer proximity to the detector volume. In additions, this winding configuration results in lower peak fields and lower stresses in the windings. Utilizing the bore volume for support structure can save a factor of two in structural mass. The resulting magnet package presents a full-diameter flat surface toward the detector space

In the past few years, several computer codes have been written for the purpose of analyzing transient recovery and quench in internally-cooled cable-in-conduit superconductors (ICCS). These codes all include a transient, compressible helium flow model. They differ in the dimensionality'' of the models, ranging from one- to three-dimensional finite element modeling of thermal conduction. The code used in this study, Wong's CICC, is a 1-{1/2} D code that models thermal conduction through the insulation of an individual conduit. Until recently, the calibration of CICC was restricted to measurements of helium expulsion in normal conductor. No actual quenches in ICCS coils had been simulated. In the past year, several experiments on ICCS conductors of differing topology have been performed and compared with CICC simulations, with varying success. This paper reports on the capability of CICC to predict and analyze ICCS recovery and quench, and on the code's limitations and need for further improvements.

A coupled electromagnetic and nonlinear structural analysis of a 4.5 tesla superconducting MHD dipole magnet is presented. The magnet design combines the latest in cable-in-conduit conductor (CICC) technology, a novel quasi-momentless support configuration, and finite element modeling to demonstrate the viability of this retrofit magnet concept. With the conductor participating as a major structural element, the support system is greatly simplified, and the overall cost and risk of the magnet system is reduced. Two and three-dimensional models are used to evaluate the concept and demonstrate how the full simulation is accomplished in one ANSYS computer run. >

The Gammas, Electrons, Muons (GEM) Detector, one of the two large detectors planned to be built at the SSC, features high muon momentum resolution. This is achieved by magnetization (by a huge magnet, about 20 m in diameter and 31 m long) of roughly 10,000 m3 of space within the muon chambers. The GEM Detector Magnet1 should be designed to operate with highest possible reliability level to ensure maximum availability of the Detector Systems. That means that the magnet and the conductor should be as stable as practically possible. The conductor should be reliably protected against overheating and electrical breakdown in the case of a quench or fast discharge. For reliability reasons, the magnet dump voltage is relatively low, 500 V to ground, which implies low current density in the conductor. Table 1 lists general requirements for the conductor.

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.< >

A conceptual design is presented for the Superconducting Super Collider GEM detector solenoid magnet. The magnet has symmetric, independent vacuum vessel enclosed halves, each with a warm bore of 18 m and containing a superconducting solenoid coil. The coils use cable-in-conduit conductor with an aluminum sheath wound at a nominal 19 m diameter in a single layer against an aluminum bobbin. The overall length of the solenoid is 30 m. The operating current in the conductor is 50 kA, which generates a central field of 0.8 T and a stored energy of 2.5 GJ. Each half solenoid is comprised of 12 modules which are electrically joined with a low resistance joint and mechanically bolted together. The unique features of this magnet are the conductor design itself and the large coil diameter, which demands an on-site winding and assembly operation. The use of a natural convection thermosiphon loop for thermal radiation cooling eliminates plumbing complications associated with double-jacketed cable-in-conduit conductors. Locating the aluminum sheath outside the conduit for quench protection enables optimizing the copper-to-superconductor ratio inside the conduit for stability alone. The conceptual design for the magnet, including the design for the detector dependent magnetics, the superconducting coils and coil. structure (cold mass), the coil winding process, the vacuum vessel and liquid nitrogen shields, the cold mass supports and the magnet assembly procedure are described.