Patent ID: 8362778
Filing Date: 2013-01-29
Classification: G01R

Abstract:
1. A cylindrical superconducting magnet arrangement comprising: a hollow cylindrical superconducting magnetic field generator having a bore; further comprising a shim arrangement for modifying the homogeneity of a magnetic field within a homogeneous field region, the shim arrangement itself comprising: shim channels extending axially within the bore, in a volume between the magnetic field generator and the homogeneous field region, at least one shim piece comprising magnetic material located within each shim channel; retaining means for retaining each shim piece in an axial position; an arrangement for moving each shim piece axially within the corresponding shim channel while the magnetic field generator is generating a magnetic field, thereby to relocate the shim pieces within the corresponding shim channels, whereby to modify the homogeneity of the magnetic field over the homogeneous field region; wherein the retaining means serve to retain each shim piece in its adjusted axial position, and wherein the arrangement for moving each shim piece axially within the corresponding shim channel is operable to adjust the axial position of each shim piece within the corresponding shim channel without adding or removing any shim pieces to or from the shim channels, further comprising a hollow cylindrical gradient coil assembly located within the bore and comprising coils for generating magnetic field gradients in a homogeneous field region located within the bore, wherein the shim channels are formed within the gradient coil assembly and extend axially therethrough, wherein the gradient coil assembly comprises gradient coils and gradient shield coils, positioned radially outside the gradient coils; the gradient coils and gradient shield coils are embedded within a potting material and the shim channels are formed within the potting material, radially between the gradient coils and the gradient shield coils.