Electricity: measuring and testing – Particle precession resonance – Spectrometer components
Patent
1989-12-04
1991-04-09
Tokar, Michael J.
Electricity: measuring and testing
Particle precession resonance
Spectrometer components
G01R 3320
Patent
active
050068040
ABSTRACT:
A method of shimming a magnet having correction coils is provided. The field strength in the bore of the magnet is measured at a predetermined number of points. The field inhomogeneity is determined from the measured field strengths. The field created by a fixed current in each shim coil operating alone, at each of the predetermined points is determined. The shim correction coil currents are determined using a linear programming solver to minimize the field inhomogeneity and the correction coil currents. The correction coil currents are determined based on the measured field in the bore of the magnet and the field created by each of the shim coils when carrying a fixed current, with the correction coil currents each constrained to a maximum value which is adjusted for the current in the correction coils when the field strength was measured. The correction coils are adjusted to the determined values and the fields strength of the magnet is gain measured at the predetermined points. The inhomogeneity is again determined and compared to a desired value of inhomogeneity. If the inhomogeneity is greater than desired, then shim correction coil currents are again determined, the determined shim coil currents set, and the field measured until the desired inhomogeneity is achieved.
REFERENCES:
patent: 4625826 (1987-03-01), Yamamoto et al.
patent: 4680551 (1987-07-01), O'Donnell et al.
patent: 4737754 (1988-04-01), Goldie
patent: 4812765 (1989-03-01), Aubert
Benesch Jay F.
Dorri Bizhan
Arana Louis M.
Davis Jr. James C.
General Electric Company
Scanlon Patrick R.
Tokar Michael J.
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