Thin high-order shims for small dipole NMR magnets

Area of Science:

• Magnetic Resonance Imaging
• Magnet Design
• Coil Engineering

Background:

• Miniaturized dipole magnets for Nuclear Magnetic Resonance (NMR) face severe spatial constraints.
• Achieving high-order shim fields is critical for high-resolution NMR spectroscopy.

Purpose of the Study:

• To introduce a novel NMR shim coil design method suitable for miniaturized dipole magnets.
• To demonstrate the feasibility of creating high-order shim fields within limited spatial volumes.

Main Methods:

• A shim coil design based on a collection of straight wires was developed.
• A shim set was constructed using 32 wires in four directions, occupying only 2mm of a 5mm gap.
• Three-dimensional magnetic field mapping of individual wires and formation of linear combinations were employed.

Main Results:

• The wire-based shim set successfully generated first through fourth order shim fields.
• The shim set occupied minimal space (2mm) in a 1.6T magnet.
• High-purity shim fields were achieved, enabling high-resolution NMR (<25ppb FWHM) with a 1.0mm sample size.

Conclusions:

• The proposed shim coil design method is effective for achieving high-resolution NMR in space-constrained miniaturized magnets.
• This approach allows for precise magnetic field control, essential for advanced NMR applications.
• The thin shim set design facilitates the use of very small sample sizes in NMR.