Active Shims for EPR Magnets

Electromagnets, commonly used for X/Q-band EPR spectroscopy typically do not have the homogeneity required for high-resolution NMR experiments. This becomes an issue for Overhauser Dynamic Nuclear Polarization (ODNP) experiments. Bridge12 offers active shims to improve the homogeneity of electromagnets typically used in EPR spectroscopy. Different models are available that fit a wide range of magnets from floor-model electromagnets to compact Halbach arrays.
Improved homogeneity leads to higher sensitivity

Improved homogeneity leads to higher sensitivity

Active shims are commonly used in high-field, superconducting magnets to improve the magnetic field homogeneity. However, shimming EPR magnets is less common nowadays. With the increased interest in low-frequency ODNP spectroscopy, shims can greatly increase the sensitivity. Especially when recording the unenhanced (off) signal.

Shimming an EPR magnet

Shimming an EPR magnet

The Bridge12 shims for EPR magnets can easily be installed between the magnet poles by the user and fit any commercially available EPR magnet. Commonly they are fitted with Z1, Z2, X, and Y coils. Higher order terms are available upon request.

... or compact Halbach arrays

… or compact Halbach arrays

Halbach magnet arrays have notoriously low magnetic field homogeneity resulting in broad NMR lines. With active shims the resolution and sensitivity can be dramatically increased and linewidths of < 10 Hz (< 0.7 ppm at 0.35 T) can be achieved. In addition, a B0 sweep coil can be added to the shim system to adjust the magnetic field strength. This is crucial in low-field ODNP experiments.

Technical Specifications

  • Form factor: Shims are available for standard EPR magnets such as Bruker ER073 or any other commercial brand
  • Correction terms: Z0, Z1, Z2, X, Y (higher order terms available upon request)
  • Gradient strength: PCB-based shims and wire-wound shims are available. The gradient strength depends on the type of shims required
  • Shims can come with integrated sweep coil (+/- 200 G)
  • Connection interface to connect a commercial shim power supply or any home-built supply

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