Homogenizing coils for nmr apparatus

Claim 2

In an NMR apparatus having means for establishing a magnetic field of predetermined magnitude in a gap between first and second magnet pole faces, a means for reducing inhomogeneities occurring in the magnetic field comprising: first and second plates formed of an electrically insulating material positioned in the gap near said first and second pole pieces respectively, said plates each supporting a plurality of spaced-apart electroconductors having segments thereof formed on opposite surfaces of plates, each of said electroconductors adapted to establish a magnetic field representable by a distinct spherical harmonic function when a current flows therein and circuit means for causing a current to flow in each of said electroconductors for homogenizing said field.

Claim 3

The apparatus of claim 1 wherein said electroconductors comprise generally arcuate and radial segments.

Claim 4

The apparatus of claim 1 wherein said electroconductors are formed of relatively flat generally arcuate and radial segments and are positioned in a manner for providing orthogonality between primary spherical harmonic functions (np, mp) which are representative of the magnetic potentials generated by said electroconductors.

Claim 5

The apparatus of claim 3 wherein said homogenizing electroconductors comprise circular segments for providing a primary spherical harmonic potential function of degree n and order m 0.

Claim 6

The apparatus of claim 3 wherein said homogenizing electroconductors comprise arcuate segments arranged as a plurality of generally semicircular segments connected to radial segments for generating a primary spherical harmonic potential function of degree n and order m 1.

Claim 7

The apparatus of claim 3 wherein said homogenizing electroconductors comprise arcuate segments arranged in a configuration of a plurality of generally quarter-circular segments connected to radial segments for generating a primary spherical harmonic potential function of degree n and order m 2.

Claim 8

In an atomic analysis apparatus having means for establishing a magnetic field of predetermined magnitude in a gap between first and second pole faces, a means for reducing inhomogenities in the magnetic field comprising: first and second plates positioned in the gap near said first and second pole faces respectively; said plates each comprising an insulative material having a relatively thin conductive material mounted on opposite sides of the insulative material; said thin conductive materials on each of said plates forming a plurality of electrically insulated electroconductors adapted to establish an equal plurality of corrective magnetic fields which are defined by primary spherical harmonic potential functions of order m 0, 1, and 2; said electroconductors including arcuate segments and spaced relatively in a manner for providing substantial orthogonality between fields the potentials of which are primary spherical potential functions (np, mp); said arcuate segments for establishing a primary spheRical harmonic potential function of order m 0 arranged in a generally circular configuration; said arcuate segments for establishing a primary spherical harmonic potential function of order m 1 arranged in a plurality of generally semicircular segments connected to radial segments; said arcuate segments for establishing a primary spherical harmonic potential function of order m 2 arranged in a plurality of generally quarter-circular segments connected to radial segments; and means for causing current to flow in each of said electroconductors for homogenizing said field.

Claim 9

In an atomic analysis apparatus having means for establishing a magnetic field of predetermined magnitude in a gap between first and second pole faces, a means for reducing inhomogenities in the magnetic field comprising: first and second plates positioned in the gap near said first and second pole faces respectively; said plates each comprising an insulative material having a relatively thin conductive material mounted on opposite sides of the insulative material; said thin conductive materials on each of said plates forming a plurality of electrically insulated electroconductors adapted to establish an equal plurality of corrective magnetic fields which are defined by primary spherical harmonic potential functions of order m 0, 1, and 2; said electroconductors including arcuate segments and spaced relatively in a manner for providing substantial orthogonality between fields the potentials of which are primary spherical potential functions (np, mp); said arcuate segments for establishing a primary spheRical harmonic potential function of order m 0 arranged in a generally circular configuration; said arcuate segments for establishing a primary spherical harmonic potential function of order m 1 arranged in a plurality of generally semicircular segments connected to radial segments; said arcuate segments for establishing a primary spherical harmonic potential function of order m 2 arranged in a plurality of generally quarter-circular segments connected to radial segments; and means for causing current to flow in each of said electroconductors for homogenizing said field.

Claim 10

The apparatus of claim 7 wherein the arcuate segments are interconnected by radial extending segments formed from the conductive material on the opposite surface of the insulative material.

Claim 11

The apparatus of claim 7 including additional pairs of plates arranged for providing additional primary spherical harmonic potential functions.

Claim 12

In an atomic analysis apparatus having magnet means for establishing a magnetic field H1 of predetermined magnitude in a gap between first and second pole faces of the magnet, a means for reducing inhomogenities in the magnetic field comprising: first and second plates positioned in the gap near said first and second pole faces respectively, said plates each supporting a plurality of electrically insulated electroconductors formed in a same plane, each of said electroconductors having a substantially uniform cross section and adapted for establishing a distinct corrective magnetic field the potential of which is representable by a spherical harmonic function; a one of said electroconductors adapted to establish a magnetic field potential representable by a primary spherical harmonic function of degree n 1 and order m 0; and, circuit means for causing currents of separately adjustable magnitude to flow in each of said electroconductors for homogenizing said field H1.

Claim 13

In an atomic analysis apparatus having magnet means for establishing a magnetic field H1 of predetermined magnitude in a gap between first and second pole faces of the magnet, a means for reducing inhomogenities in the magnetic field comprising: first and second plates positioned in the gap near said first and second pole faces respectively, said plates each supporting a plurality of electrically insulated electroconductors formed in a same plane, each of said electroconductors having a substantially uniform cross section and adapted for establishing a distinct corrective magnetic field the potential of which is representable by a spherical harmonic function; a one of said electroconductors adapted to establish a magnetic field potential representable by a primary spherical harmonic function of degree n 1 and order m 0; and, circuit means for causing currents of separately adjustable magnitude to flow in each of said electroconductors for homogenizing said field H1.

Claim 14

In a nuclear magnetic resonance apparatus having means for establishing a magnetic field of predetermined magnitude in a gap between first and second magnet pole faces, a means for reducing inhomogenities occurring in the magnetic field comprising: a plurality of windings positioned between said pole faces, each of said windings arranged for establishing a primary magnetic field representable by a distinct spherical harmonic function of particular degree and order and simultaneously creating ancillary magnetic fields in said gap when a current of predetermined amplitude flows therein; first circuit means for providing a separate electrical current flow path between each of said windings and a current source for homogenizing said field; a current flowing in a first homogenizing coil of a first electrical current flow path creating an ancillary magnetic field which interferes with a primary magnetic field created by a current flowing in a homogenizing winding of a second electrical current flow path; and an electrical impedance coupled between said first and second current flow paths for applying a portion of a current flowing in said first path to said second path, said impedance having a magnitude for applying a current to said second circuit having an amplitude for cancelling the interference of said ancillary field on the primary field of said second circuit winding.

Claim 15

In a nuclear magnetic resonance apparatus having means for establishing a magnetic field of predetermined magnitude in a gap between first and second magnet pole faces, a means for reducing inhomogenities occurring in the magnetic field comprising: a plurality of windings positioned between said pole faces, each of said windings arranged for establishing a primary magnetic field representable by a distinct spherical harmonic function of particular degree and order and simultaneously creating ancillary magnetic fields in said gap when a current of predetermined amplitude flows therein; first circuit means for providing a separate electrical current flow path between each of said windings and a current source for homogenizing said field; a current flowing in a first homogenizing coil of a first electrical current flow path creating an ancillary magnetic field which interferes with a primary magnetic field created by a current flowing in a homogenizing winding of a second electrical current flow path; and an electrical impedance coupled between said first and second current flow paths for applying a portion of a current flowing in said first path to said second path, said impedance having a magnitude for applying a current to said second circuit having an amplitude for cancelling the interference of said ancillary field on the primary field of said second circuit winding.

Claim 16

The apparatus of claim 11 wherein said plurality of homogenizing windings includes windings adapted for generating homogenizing fields the potentials or which are combinations of the spherical harmonic functions of the degree and order (2,1), (4,1) and (4,3), and said electrical impedance means is arranged for linearly adding currents proportional to currents flowing in the (2,1) and (4,1) windings to the current flowing in the (4,3) winding to reduce interference of fields generated by the former on the field of the latter winding.

Claim 17

The appaRatus of claim 11 wherein said plurality of windings includes windings adapted for generating homogenizing fields the potentials of which are combinations of the spherical harmonic functions of the degree and order (2,1)'', (4,1)'' and (4,3)'', and said electrical impedance means is arranged for linearly adding currents proportional to those flowing in the (2,1)'' and (4,1)'' winding to the current flowing in the (4,3)'' winding to reduce interference of fields generated by the former on the field of the latter winding.