No-Insulation Multi-Width Winding for High Temperature Superconducting Magnets

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Yukikazu Iwasa
Francis Bitter Magnet Lab, MIT
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Seungyong Hahn
Francis Bitter Magnet Lab, MIT
Juan Bascunan
Francis Bitter Magnet Lab, MIT
Dong Keun Park
Francis Bitter Magnet Lab, MIT
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Jim Freedman
MIT Technology Licensing Officer - Chemicals, Instruments, Consumer Products
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No-insulation multi-width winding for high temperature superconducting magnets

US Patent 9,117,578
HTS Pancake Coils Without Turn-to-Turn Insulation
IEEE Transactions on Applied Superconductivity, volume 21, issue 3, June 2011


This invention has applications in the development of high-performance and small-footprint superconducting electromagnets for micro-nuclear magnetic resonance (micro-NMR) spectroscopy.

Problem Addressed

At present, standard high-field NMR magnets are made from low-temperature superconducting (LTS) materials such as NbTi and Nb3Sn. Due to the low current-carrying capacity of these materials, conventional magnets suffer from large size and high cost due to the large quantities of superconducting material required. This cost disadvantage is further exacerbated by the reliance of conventional LTS magnets on expensive liquid helium to keep the magnet at superconducting temperatures and avoid undesired quenching. This invention describes a novel high-temperature superconducting (HTS) magnet design that significantly outperforms conventional LTS magnets in terms of footprint and operational stability while reducing reliance on liquid helium cooling.


This invention describes a compact HTS magnet with a room temperature bore of just 25 mm and the capability to generate fields up to 11.74 T.

This design differs from conventional magnets in two key ways. First, the HTS tape making up the windings is uninsulated, allowing electrical contact between adjacent turns of the coil. This adds to the operational stability of the magnet by allowing overload currents to flow directly from turn to turn, bypassing the original spiral path and protecting the magnet from overcurrent damage. This self-protecting feature allows the amount of stabilizer material (e.g. copper) required in the HTS tape to be minimized, thereby reducing magnet size by approximately two-thirds compared to conventional designs.

The second innovation in this design is to vary the width of HTS tape used to construct the magnet coils. Tape width is reduced as one moves closer to the midplane of the magnet coil, creating a central region of elevated current density. This allows the magnet to achieve center fields up to 1.5x greater than comparable magnets with constant-width windings.


  • Reduced footprint compared to conventional NMR magnets (66% size reduction demonstrated in 500 MHz magnet)
  • Self-protecting against overcurrent damage and quenching
  • Does not require liquid helium