Optimization of a parallel‐plate RF probe for high resolution thin film imaging

Abstract

Choosing an MR probe with the correct dimensions and high sensitivity is critical for magnetic resonance imaging, especially high resolution thin film imaging. In this work, a parallel‐plate resonator has been optimized for strength and uniformity of the B1 magnetic field. The parallel‐plate resonator is designed for high resolution imaging in the direction perpendicular to the plates. The optimization process was undertaken through simulation with CST Micro Wave Studio, followed by experiment. A 400 μm capillary tube, filled with doped water, was used for testing the optimized probe in a 2.4 T magnet. It is shown that increasing the width of the copper leads connected to the plates increases the homogeneity of the B1 magnetic field by almost 90%. The best approach to increase the sensitivity and the homogeneity of the probe was to maintain the dimensions of the plates and copper leads but to add additional capacitors at the corners to distribute the current. This approach produces a 40% stronger B1 magnetic field and increases the homogeneity by almost 85%. The experimental B1 magnetic field of the parallel‐plate prototype agrees within 20% of the value found through simulation, for specified power. The experimental MRI results show that it is possible to achieve a nominal resolution of 10 μm between the plates for suitable samples using the optimized probe. The optimized parallel‐plate resonator, combined with a phase encode SE SPI method, may be used for high resolution studies of lithium‐ion transport in the electrolyte solution of lithium‐ion batteries.

Application of Magnetic Resonance Techniques to the In Situ Characterization of Li-Ion Batteries: A Review

“…Assembling such a probe directly on the outside of a single-layer prismatic cell would allow researchers to obtain the desired field alignment. More recently the potential of a similar approach for magnetic resonance experiments on lithium ion cells have been demonstrated utilizing a model system [78].…”

Quantitative Operando 7Li NMR Investigations of Silicon Anode Evolution during Fast Charging and Extended Cycling

“…Ex situ NMR measurements were also performed to highlight the new insights into the operation of the Si electrodes gained through operando measurements. The operando data were obtained with our parallel-plate resonator ,− and a novel reusable cartridge-type electrochemical cell that mimics the layout of a single-layer pouch cell ,,− Both in situ and operando measurements can provide insights into the chemical and structural changes in the active material that may not be detected by ex situ measurements …”