A new low field magnet for Overhauser Dynamic Nuclear Polarization magnetic resonance studies
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Date
2024-11
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University of New Brunswick
Abstract
Low-cost portable magnetic resonance (MR) instruments have significantly evolved over the past several decades, offering diverse applications in medical diagnostics, material science, and beyond. Instruments for MR that employ permanent magnets are advantageous given that they are low-cost, portable, and simple to construct. This is not true for conventional superconducting magnets. Improvement of the instruments and measurement techniques employed in portable MR is essential for better material characterization. In this thesis, we present several portable magnet designs, based on permanent magnets, with diverse applications. An essential element of each design is that they are simple to construct, encouraging their use by others.
The first magnet design is an improvement upon the existing three-magnet array design. We employ computer simulation to optimize the magnet placements for a large homogenous region displaced far from the magnet surface. We explored the usage of this instrument for measurement of liquid samples and water-oil content determination.
The second magnet design is termed the CLAM (Ceramic Low-field Angled Magnet) magnet. It was employed for the dual purpose of flow velocity measurement and Overhauser Dynamic Nuclear Polarization (O-DNP). Ceramic magnets offer the advantage ii of being cost-effective and supporting efficient O-DNP enhancement due to their lower field strength. The design naturally led to two configurations: a homogeneous magnet for O-DNP, and a constant gradient magnet for flow measurements. The ability to spatially enhance 1H spins through local O-DNP enhancement was explored in the gradient configuration, which continued in the following study.
The culmination of this work is demonstrated through O-DNP selective enhancement of water or oil. The free-radical species 4-Hydroxy-TEMPO and 4-Hydroxy-TEMPO benzoate were employed to selectively enhance the signal from oil or water based on the solubility of the TEMPO agent. The preferential solubility of the free radical species in a chosen phase permitted the enhancement of a single species of interest. A new 1D profiling CLAM magnet design was created to image O-DNP selective enhancement. Studies of rock core flooding confirmed and validated this technique for exploring material characterization beyond what was previously possible with standard MR techniques.