USA Banner

Official US Government Icon

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure Site Icon

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Novel Cryogen-free Actively Shielded Superconducting Magnets for Maglev Vehicles

Document Series:
Technical Reports
Author:
  • M. E. Vermilyea
Report Number
DOT/FRA/NMI-92/07
Office
RRD
Subject:
Maglev
Keywords:
Shielding, Cryogenics, Magnet System

This report presents the results of a research effort into the design of a shielded superconducting magnet system for a maglev vehicle. The magnet design is based on a novel cryogen-free technology which allows operation without the use of any cryogenic fluids. This is accomplished by the use of a two- stage Gifford-McMahon (G-M) cryogenic refrigerator to provide cooling of the coil and a single cryostat thermal radiation shield by conduction. The design operating temperature of the magnet is 7.5 K, and that of the shield is 43 K. The magnet is wound with a tape form of niobium tin superconductor which allows operation at a module current density of 8100 A/cm2 at a flux density of 3.4 T at the 7.5 K temperature with a margin of 4.5 K to critical temperature. The resulting magnet design is more reliable, rugged, and less expensive and heavy than a comparable pool cooled system, and is recommended for application to any maglev vehicles developed in the United States requiring superconducting magnets. Shielding of the passenger compartment of the vehicle from the DC magnetic field of the superconducting magnets is also investigated here for an assumed geometry. The geometry used is that of a sidewall, null-flux levitation and propulsion system, with the planes of the vehicle coils in a vertical orientation. Both active and passive shielding techniques are reviewed and applied to the assumed coil and vehicle geometry, with variations on the geometry considered to determine their effect on reducing the field in the passenger compartment Options for reducing the field to certain levels are presented. The basic conclusion of the shielding study is that shielding using active coils is rather ineffective for the assumed geometry, and that the only realistic shielding methods are passive shielding (using iron in the vehicle structure) and shielding by distance (raising the vehicle farther above the magnets).


DOT is committed to ensuring that information is available in appropriate alternative formats to meet the requirements of persons who have a disability. If you require an alternative version of files provided on this page, please contact FRADevOps@dot.gov.
Last updated: Monday, June 1, 1992