Homogeneous magnetic field generator in a sphere centred on a central point, this generator comprising: - coils (122-125, 128-131, 134-137, B) wound around, respectively, a first, a second, and a third winding axes (X, Y, Z), the first, second and third winding axes being mutually orthogonal and secant at a common point corresponding to the central point, the coils wound around one and the same winding axis being arranged along this winding axis in such a way that a plateau of intensity of the magnetic field generated by these coils is produced at the central point when these coils are passed through by one and the same current, - the generator comprising at least four of these coils wound around each of the winding axes, the four coils wound around the same winding axis forming two pairs of coils, each coil of a pair being symmetrical with the other coil of the pair relative to a plane of symmetry at right angles to this winding axis and passing through the central point, characterized in that, for each winding axis, the four coils (122-125, 128-131, 134-137, B) wound around this axis are spaced apart from one another in such way as to cancel at least the first derivative up to the seventh derivative of the magnetic field generated by these coils, parallel to the winding axis, at the central point when they are powered by the same current, and - the circumference of each coil is a circle, the diameter of this circle being equal, to within plus or minus 2%, to the diameter of a circle defined by the intersection of a sphere centred on the central point and of a plane, at right angles to the winding axis of this coil, passing through this coil, the sphere being the same for all the coils wound around the same winding axis. - coils (122-125, 128-131, 134-137, B) wound around, respectively, a first, a second, and a third winding axes (X, Y, Z), the first, second and third winding axes being mutually orthogonal and secant at a common point corresponding to the central point, the coils wound around one and the same winding axis being arranged along this winding axis in such a way that a plateau of intensity of the magnetic field generated by these coils is produced at the central point when these coils are passed through by one and the same current, - the generator comprising at least four of these coils wound around each of the winding axes, the four coils wound around the same winding axis forming two pairs of coils, each coil of a pair being symmetrical with the other coil of the pair relative to a plane of symmetry at right angles to this winding axis and passing through the central point, characterized in that, for each winding axis, the four coils (122-125, 128-131, 134-137, B) wound around this axis are spaced apart from one another in such way as to cancel at least the first derivative up to the seventh derivative of the magnetic field generated by these coils, parallel to the winding axis, at the central point when they are powered by the same current, and - the circumference of each coil is a circle, the diameter of this circle being equal, to within plus or minus 2%, to the diameter of a circle defined by the intersection of a sphere centred on the central point and of a plane, at right angles to the winding axis of this coil, passing through this coil, the sphere being the same for all the coils wound around the same winding axis.