Technical Reports

Application of Cable-in-Conduit Conductor (CICC) to Maglev Magnetic Systems

  • 31
  • Jul
  • 1992
AUTHOR: R. J. Thomas, D. B. Montgomery, J. V. Minervini
KEYWORDS: Conductor Design, Levitation Magnet Design, Railroad Technology
ABSTRACT: This report summarizes the evaluation of CICC as an option for MAGLEV levitation coils. Superconducting magnets are cooled by: 1) immersion in a liquid helium bath it near saturation conditions; 2) conduction cooling of an epoxy-impregnated coil; or 3) use of CICC in which single-phase supercritical helium cooling becomes an intrinsic part of the conductor design with helium contained in the conductor sheath. Major problems with options 1) and 2) are mitigated by use of option 3. Many levitation coil geometries were reviewed and the racetrack coil shape selected for :he levitation coil system design task. The study showed that lift force per unit weight (coil plus cryostat) is proportional to the product of the conductor current density, j, and maximum magnetic field, BM, experienced by the winding divided by the weight density. The lift force is also proportional to coil shape, track and speed characteristics, and dewar functions; however, no variables in this dimensionless group is conductor related. The design was to a maximum product of BM for the conductor. Analyses using both Nb3Sn and NbTi at preselected temperatures and energy margins showed that systems optimized at a low field level from 2.0 to 3.7T, that Nb3Sn systems have higher jBms than NbTi at the same temperatures and that Nb3Sn was therefore preferred. Those studies, although not optimized, indicate clearly that distinct advantages lie in using Nb3Sn CICC at 8 K as opposed to the 4.5 K of conventional systems. Elevated operating temperature may lead to significant reductions in refrigerator weight.