scholarly journals Pulsed magnetic field generation suited for low-field unilateral nuclear magnetic resonance systems

AIP Advances ◽  
2018 ◽  
Vol 8 (5) ◽  
pp. 056814 ◽  
Author(s):  
Neelam Prabhu Gaunkar ◽  
Jayaprakash Selvaraj ◽  
Wei-Shen Theh ◽  
Robert Weber ◽  
Mani Mina
Keyword(s):  
Magnetic Field ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Pulsed Magnetic Field ◽  
Magnetic Field Generation ◽  
Field Generation ◽  
Low Field ◽  
Nuclear Magnetic

scholarly journals Effective Suppression of Residual Magnetic Interference in a Conductive Shielded Room for Ultra-Low Field Nuclear Magnetic Resonance

2020 ◽  
Vol 10 (11) ◽  
pp. 3745
Author(s):  
Yiqiu Tan ◽  
Danfeng Zhou ◽  
Mengxiao Song ◽  
Jie Li
Keyword(s):  
Magnetic Field ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Eddy Currents ◽  
Small Scale ◽  
Signal Loss ◽  
Low Field ◽  
Residual Magnetic Field ◽  
Control Electronics ◽  
Nuclear Magnetic

Residual magnetic interference induced by applied magnetic field pulses inside a conductive shielded room (SR) has been a common issue in ultra-low-field (ULF) nuclear magnetic resonance (NMR). The rapid cutoff of the applied pre-polarizing field (Bp) induces eddy currents in the walls of the SR, which produces a decaying residual magnetic interference that may cause severe image distortions and signal loss. In this study, a pair of cancellation coils (CC) and control electronics were designed for the suppression of the residual magnetic interference in a SR. Simulations show that this method was effective in suppressing the residual magnetic field (Br) after removal of the pre-polarizing magnetic field. Then, a small-scale SR was designed and the effectiveness of this cancellation scheme was experimentally verified. The test results showed a good agreement with the simulation, which indicated that the cancellation scheme was capable of reducing Br field to a much lower level. The scheme proposed in this study provides a solution for suppressing the residual magnetic field in the ULF NMR system. After decoupling the eddy–current field, the effect of the suppression may be further improved by optimization of the cancellation coil in further work.

Nuclear magnetic resonance microscopy

1989 ◽  
Vol 47 ◽  
pp. 828-829
Author(s):  
Paul C. Lauterbur
Keyword(s):  
Magnetic Field ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Fields ◽  
Signal To Noise ◽  
Field Gradients ◽  
Useful Signal ◽  
Magnetic Field Gradients ◽  
Observation Times ◽  
Nuclear Magnetic

Nuclear magnetic resonance imaging can reach microscopic resolution, as was noted many years ago, but the first serious attempt to explore the limits of the possibilities was made by Hedges. Resolution is ultimately limited under most circumstances by the signal-to-noise ratio, which is greater for small radio receiver coils, high magnetic fields and long observation times. The strongest signals in biological applications are obtained from water protons; for the usual magnetic fields used in NMR experiments (2-14 tesla), receiver coils of one to several millimeters in diameter, and observation times of a number of minutes, the volume resolution will be limited to a few hundred or thousand cubic micrometers. The proportions of voxels may be freely chosen within wide limits by varying the details of the imaging procedure. For isotropic resolution, therefore, objects of the order of (10μm) may be distinguished.Because the spatial coordinates are encoded by magnetic field gradients, the NMR resonance frequency differences, which determine the potential spatial resolution, may be made very large. As noted above, however, the corresponding volumes may become too small to give useful signal-to-noise ratios. In the presence of magnetic field gradients there will also be a loss of signal strength and resolution because molecular diffusion causes the coherence of the NMR signal to decay more rapidly than it otherwise would. This phenomenon is especially important in microscopic imaging.

Application of Low-Field Nuclear Magnetic Resonance (LFNMR) in Characterizing the Dissociation of Gas Hydrate in a Porous Media

2021 ◽  
Vol 35 (3) ◽  
pp. 2174-2182
Author(s):  
Yongchao Zhang ◽  
Lele Liu ◽  
Daigang Wang ◽  
Pengfei Chen ◽  
Zhun Zhang ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Porous Media ◽  
Magnetic Resonance ◽  
Gas Hydrate ◽  
Low Field ◽  
Nuclear Magnetic
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