An easy-built Halbach magnet for LF-NMR with high homogeneity using optimized target-field passive shimming method

Area of Science:

• Magnetic Resonance Imaging
• Magnet Design
• Spectroscopy

Background:

• Portable low-field NMR (LF-NMR) systems require magnets with high homogeneity and ease of construction.
• Existing Halbach magnet designs may not meet the criteria for portability, cost-effectiveness, and simplicity.

Purpose of the Study:

• To develop an easy-to-build, low-cost Halbach magnet with high homogeneity for portable LF-NMR.
• To optimize the magnet's performance using passive shimming techniques.

Main Methods:

• A 4-ring Halbach magnet was designed using simulation and mechanical modeling.
• The magnet was constructed in a laboratory setting and characterized for field strength and homogeneity.
• An optimized target-field passive shimming method was developed and applied.
• Proton (¹H) NMR experiments were conducted on water samples using a homemade spectrometer.

Main Results:

• The constructed Halbach magnet achieved a field strength of 0.169 T with an initial homogeneity of 8204 ppm (20 mm diameter sphere).
• Passive shimming significantly reduced linewidths; a 3 mm sample's linewidth decreased from 452.3 Hz to 12.9 Hz.
• The shimming method achieved high homogeneity, demonstrating effectiveness for LF-NMR.

Conclusions:

• The developed Halbach magnet is suitable for portable LF-NMR applications due to its ease of construction, low cost, and high homogeneity after shimming.
• The proposed passive shimming method effectively enhances magnet homogeneity for NMR experiments.
• This work provides a viable magnet solution for advancing portable NMR technology.