Improved, minimum-inductance, elliptic-cylinder z-gradient coil using axial and azimuthal current flow

A new design for a minimum inductance, distributed current, longitudinal (z) gradient coil, fabricated on the surface of an elliptic cylinder is proposed. By incorporating a small axial current, in addition to the purely azimuthal current which has been considered hitherto, this design greatly reduces the nonuniformity of the longitudinal magnetic field in transverse planes, which is associated with a purely azimuthal current flowing on the surface of an elliptic cylinder. For a coil with an axial ratio of the ellipse of 0.75, the deviation from gradient linearity along the z axis is <0.1% out to 0.66a where a is the length of the semi-major axis. The nonuniformity of the field in the transverse directions is <0.1% out to 0.5a, over most of the target-field region \z\ < 0.4a. (C) 1996 Academic Press, Inc.