Gradient coils for therapy tomographs

Abstract

A gradient coil system for the production of a magnetic transverse gradient field G.sub.x =dB.sub.z /dx in an NMR tomograph has axial and transverse access to the measuring volume. The gradient coil system consists of four partial coils (S.sub.1x, S.sub.2x, S.sub.3x, S.sub.4x) each with two current connections (A.sub.1, A.sub.2), which are arranged mirror symmetrically with respect to the xy-plane (z=0) and mirror symmetrically with respect to the zy-plane (x=0). Each partial coil comprises winding sections on an inner and on an outer cylinder Z.sub.1x, Z.sub.ax) about the z-axis as well as on a radial connecting surface V.sub.+x, V.sub.-x and the radial connecting surfaces V.sub.+x, V.sub.-x of those partial coils (S.sub.1x, S.sub.4x ; S.sub.2x, S.sub.3x,) which face each other opposite the xy-plane are essentially identical. An axial gap for free transverse access to the measuring volume remains between the partial coils. Since the winding sections on both cylinders are restricted to z-values which are larger than the distance from the connecting surfaces to z=0, good shielding and linearity is nevertheless achieved.