4.5 Tesla superconducting miniature magnet in liquid nitrogen.

Area of Science:

• Materials Science
• Superconductivity
• Magnet Technology

Background:

• Liquid nitrogen (LN₂) cooling offers a simpler and potentially lower-cost alternative to cryocooler-based or liquid helium (LHe) systems for high-temperature superconductor (HTS) magnets.
• Liquid helium is scarce, expensive, and difficult to handle, driving the need for alternative cooling methods.
• HTS technology enables high magnetic fields even at LN₂ temperatures.

Purpose of the Study:

• To demonstrate a proof-of-concept for compact high-field generation using HTS magnets cooled by liquid nitrogen.
• To assess the performance of a double-pancake coil magnet designed for LN₂ operation.
• To explore the feasibility of LN₂-cooled HTS magnets for nuclear magnetic resonance (NMR) applications.

Main Methods:

• A double-pancake coil magnet was constructed using 2 × 200 m, 10 mm wide HTS tape.
• Individual pancake coils were powered to generate 3 Tesla.
• Pancake coils were stacked and operated in parallel to achieve a maximum field of 4.5 Tesla.
• Coils were previously quenched in liquid helium to confirm manufacturing robustness.

Main Results:

• A maximum magnetic field of 4.5 Tesla was achieved with the double-pancake HTS magnet operating in liquid nitrogen at 77 K.
• Individual pancake coils generated 3 Tesla.
• The results indicate the robustness of the manufacturing and operation approach, as coils were pre-quenched in LHe.

Conclusions:

• LN₂-cooled HTS magnets are feasible for NMR-relevant high-field applications.
• This work provides a foundation for optimizing geometry, field homogeneity, and operating temperature for future LN₂-only NMR systems.
• The demonstrated technology paves the way for achieving high magnetic fields and homogeneity necessary for NMR spectroscopy solely in LN₂.