Journal
IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT
Volume 70, Issue -, Pages -Publisher
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI: 10.1109/TIM.2021.3074951
Keywords
Adaptive simplex; automatic shimming; field homogeneity; low-field nuclear magnetic resonance (NMR); magnetic susceptibility effect
Funding
- National Natural Science Foundation of China [U1805261, 11761141010]
Ask authors/readers for more resources
Two remedies are proposed to improve the shimming speed for the search shimming method: relocating starting points closely to optima by analyzing and compensating for magnetic susceptibility effects, and improving the convergence of the simplex shimming algorithm in a multidimensional search space by modifying the simplex movement. The proposed shimming method outperforms regular shimming methods in handling complex magnetic fields and reducing shimming times, showing potential for further improvement in NMR shimming methods.
During the past several decades, inexpensive compact nuclear magnetic resonance (NMR) instruments have been widely used for on-site detections of chemical identity and sample analyses in industrial applications. In general, via shim coils and control strategies, automatic search shimming methods are capable of improving the magnetic field uniformity so that optimized signals can be acquired and particularly suited for rapid detections in compact NMR instruments. However, because these methods inherently endure the inefficiency in multidimensional shims and the sensitivity of starting points, it is time-consuming to obtain acceptable results in a field infected with distortions and strays. Here, two remedies that improve the shimming speed for the search shimming method are proposed. First, analyzing and compensating for magnetic susceptibility effects, we relocate starting points closely to optima and reduce the complexity of global exploration. Second, modifying the simplex movement with adaptive scale factors and gradient-like centroid, we have improved the convergence of the simplex shimming algorithm in a multidimensional search space. Via theoretical analyses and lab experiments, we find that the proposed shimming method outperforms regular shimming methods in terms of handling complex magnetic fields and reducing shimming times and hope that our study can help further improve NMR shimming methods in the future.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available