Electricity: measuring and testing – Particle precession resonance – Spectrometer components
Patent
1985-10-07
1987-07-14
Levy, Stewart J.
Electricity: measuring and testing
Particle precession resonance
Spectrometer components
324318, G01R 3320
Patent
active
046805516
ABSTRACT:
A method for minimizing the inhomogeneity of a static magnetic field, produced by a main magnet, over a selected arbitrary volume, by operation of a plurality N of shimming coils each independently producing an associated shimming magnetic field having an associated inhomogeneity which is a function of spatial location over that same volume, uses the steps of: measuring the magnitude of the main magnet field, in the absence of all shimming fields, at a plurality of locations X.sub.i upon the surface of an imaginary sphere enclosing the arbitrary volume; measuring the polarity and magnitude of each of the N shimming fields, with respect to the polarity and magnitude of a D.C. current flowing through the associated shimming coil, at the same plurality of locations X.sub.i upon the imaginary sphere surface; determining the weighted mean-square variation of the total field at each of another plurality of points Y.sub.i within the volume of said imaginary sphere; and (d) selecting the current magnitudes and polarities for each of the N shimming coils to provide each of the N associated shimming fields with magnitude and polarity to minimize the inhomogeneity of the main magnetic field in the arbitrary volume. The set of weighting coefficients may be selected to all be equal, or to emphasize at least one desired region of the arbitrary volume.
REFERENCES:
patent: 4523166 (1985-06-01), Gross
patent: 4581580 (1986-04-01), Keim
Current Shims for High-Resolution NMR on Correcting Field Inhomogeneities, I. Zupancic Nuclear Ins. J. Stefan Ljubljana Yugo, Apr./1962.
Electrical Current Shims for Correcting Mag. Fields, W. Anderson, Review of Scientific Instruments, vol. 32, No. 3, Mar./1961.
Barber William D.
Edelstein William A.
Karr Steven G.
O'Donnell Matthew
Wang Jish M.
Arana Louis M.
Davis Jr. James C.
General Electric Company
Krauss Geoffrey H.
Levy Stewart J.
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