A portable Halbach magnet that can be opened and closed without force: the NMR-CUFF

Area of Science:

• Physics
• Engineering
• Biophysics

Background:

• Portable nuclear magnetic resonance (NMR) requires lightweight, strong, and homogeneous magnetic fields.
• Existing NMR magnets are often heavy or limited to small sample sizes.
• Developing portable NMR equipment faces challenges in magnet design.

Purpose of the Study:

• To present a novel Halbach-type permanent magnet ring concept for portable NMR.
• To demonstrate a lightweight, openable magnet with strong and homogeneous fields.
• To enable in-situ NMR measurements on larger or immobile samples.

Main Methods:

• Designed a Halbach-type permanent magnet ring with a specific opening angle (35.3°) for force cancellation.
• Constructed a prototype magnet (NMR-CUFF).
• Measured flux density, homogeneity, and closing force; performed plant imaging and water flow measurements.

Main Results:

• The prototype magnet weighed 3.1 kg and achieved 0.57 T flux density.
• Demonstrated homogeneity better than 200 ppm over a 5mm spherical volume without shimming.
• Required only 20 N force to close, enabling easy operation.

Conclusions:

• The NMR-CUFF magnet concept is ideal for portable NMR and in-situ measurements.
• This design is suitable for investigating small or slender objects in their natural environment.
• The magnet technology has potential applications beyond NMR, including accelerators and motors.