Electricity: magnetically operated switches – magnets – and electr – Magnets and electromagnets – Superconductive type
Patent
1991-08-27
1993-11-30
Donovan, Lincoln
Electricity: magnetically operated switches, magnets, and electr
Magnets and electromagnets
Superconductive type
324307, H01F 100
Patent
active
052669130
ABSTRACT:
A primary gradient coil and a screen coil for use with the primary coil are constructed to create a substantially null field adjacent to the screen coil and a substantially distortion free linear gradient field adjacent to the gradient coil. A method is disclosed for generating the coils by considering the screen coil to be of infinite length, deriving a Fourier transform of the axial and other components of the field in which the transform is the sum of the permissible harmonic modes on the coil surface in which a coefficient C.sub.n is derived representing the nth harmonic. A perfect screen coil is created and the number of terms C.sub.n selected using least squares optimization until there is no longer a significant change in the resulting field. Examples are given for creating unscreened, screened, linear, axial and transverse gradient field coils.
REFERENCES:
patent: 4794338 (1988-12-01), Roerer et al.
patent: 4853663 (1989-08-01), Vermilyea
patent: 4978920 (1990-12-01), Mansfield et al.
P. Manfield & B. Chapman, "Multishield Active Magnetic Screening of Coil Structures in NMR", Journal of Magnetic Resonance, 72, pp. 211-223, (1987).
P. Mansfield & B. Chapman, "Active Magnetic Screening of Gradient Coils in NMR Imaging", Journal of Magnetic Resonance, 66, pp. 573-576, (1986).
R. Turner & R. M. Bowley, "Passive Screening of Switched Magnetic Field Gradients", Phys. E: Sci. Instrum., 19, (1986), pp. 876-879, printed in Great Britain.
P. Mansfield & B. Chapman, "Active Magnetic Screening of Coils for Static and Time-Dependent Magnetic Field Generation in NMR Imaging", J. Phys. E: Sci. Instrum., 19, (1986), pp. 540-545, printed in Great Britain.
B. Chapman & P. Mansfield, "Double Active Magnetic Screening of Coils In NMR", J. Phys. D: Appl. Phys., 19, (1986), pp. L129-L131, printed in Great Britain.
R. Turner, "A Target Field Approach To Optimal Coil Design", J. Phys. D: Appl. Phys., 19, (1986), pp. L147-L151, printed in Great Britain.
R. Turner, "Minimum Inductance Coils", J. Phys. E: Sci. Instrum., 21, (1988), pp. 948-952, printed in the United Kingdom.
British Technology Group USA Inc.
Donovan Lincoln
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