Patent ID: 8648678

Claim:
A compact superconducting magnet device to generate a homogeneous magnetic field component Bz along an axis Oz in a zone of interest (ZI) for nuclear magnetic resonance or magnetic resonance imaging applications, successively comprising, starting from the axis Oz and perpendicular to this axis Oz, at least one first superconducting helical coil ( 1 ; 101 ) formed around a first circular cylinder section ( 10 ; 110 ) of axis Oz delimited by first end circles ( 10 A, 10 B; 110 A, 110 B), said first superconducting helical coil ( 1 ; 101 ) having a first outer radius (a 12 ), a first inner radius (a 11 ), and a first length ( 2 b 1 ), with a first azimuthal current density j 1 , at least one second superconducting helical coil ( 2 ; 102 ) formed around a second circular cylinder section ( 20 ; 120 ) of axis Oz delimited by second end circles ( 20 A, 20 B; 120 A, 120 B) and surrounding said first circular cylinder section ( 10 ; 110 ), said second coil ( 2 ; 102 ) having a second outer radius (a 22 ), a second inner radius (a 21 ) and a second length ( 2 b 2 ), with a second azimuthal current density j 2 , characterized in that the lateral ends of the first and second helical coils ( 1 , 2 ; 101 , 102 ) are arranged, to within the thickness of the coils, in the vicinity of one same sphere ( 5 ; 105 ) of radius c whose centre O is placed on the axis Oz in the centre of said zone of interest (ZI) and which encompasses the magnet device assembly, in that it further comprises at least one third superconducting helical coil ( 3 ; 103 ) formed around a third circular cylinder section ( 30 ; 130 ) of axis Oz delimited by third end circles ( 30 A, 30 B; 130 A, 130 B) and surrounding said second circular cylinder section ( 20 ; 120 ), said third coil ( 3 ; 103 ) having a third outer radius (a 32 ), a third inner radius (a 31 ) and a third length ( 2 b 3 ), with a third azimuthal current density j 3 , in that said first, second and third azimuthal current densities j 1 , j 2 , j 3 are of alternate opposite sign, in that the first, second and third lengths ( 2 b 1 , 2 b 2 , 2 b 3 ) of the first, second and third coils ( 1 , 2 , 3 ; 101 , 102 , 103 ) are of decreasing length, in that the outer radius (a 32 ) of the outermost superconducting helical coil ( 3 ; 104 ) is substantially equal to the half-length (b 1 ) of the innermost superconducting helical coil ( 1 ; 101 ) and in that the outer radius (a 12 ) of the innermost superconducting helical coil ( 1 ; 101 ) is substantially equal to the half-length (b 3 ; b 4 ) of the outermost superconducting helical coil ( 3 ; 104 ).