Rotatable Small Permanent Magnet Array for Ultra-Low Field Nuclear Magnetic Resonance Instrumentation: A Concept...

Area of Science:

• Physics
• Engineering
• Materials Science

Background:

• Ultra-low field nuclear magnetic resonance (NMR) relaxometry traditionally relies on bulky electromagnets.
• The need for portable and energy-efficient NMR systems is growing.
• Permanent magnets offer a potential alternative to electromagnets for generating magnetic fields.

Purpose of the Study:

• To investigate the feasibility of using dynamically adjustable permanent magnets for generating variable magnetic fields in NMR relaxometry.
• To explore the potential of replacing electromagnets with permanent magnet arrays to improve system portability.

Main Methods:

• Numerical simulations using the finite element method (COMSOL®) were performed on a small permanent magnet array.
• Key parameters such as magnetic field strength, homogeneity, switching time, and magnetic forces were calculated.
• A manually operated prototype was simulated and constructed to validate the numerical findings.

Main Results:

• A concentric small permanent magnet array can generate strong pre-polarisation fields (>100 mT) and variable measurement fields (20-50 μT).
• High field homogeneity (200 ppm) was achieved within a 5 x 5 x 5 cm³ field-of-view.
• Simple magnet rotations enable dynamic adjustment of magnetic fields for NMR applications.

Conclusions:

• A dynamic small permanent magnet array can successfully generate the multiple, highly homogeneous magnetic fields required for ultra-low field NMR and MRI.
• This permanent magnet-based design significantly reduces the volume and energy consumption compared to traditional electromagnet systems.
• The proposed approach offers a substantial improvement in the portability of NMR and MRI instruments.