wherein a secondary connection is made by virtue of the third support 152 39 for the coil or alternatively by employing other connections not shown between the coils rf loss is maintained at its lowest possible value when it is as uniformly distributed across the conductor cross section of the coil windings as the skin effect will permit because the rf current travels only along the conductor surface of the coil windings rf loss is minimized by maximizing the coil surface area in contact with the rf magnetic field it has also be determined by modeling studies that the best cross section of the segmented toroidal shaped excitation coil of the invention is one where the inside coil windings 64 and 66 have a smaller cross sectional area than the outside coil windings 62 and 68 thus the optimal cross sectional structure of the coil configuration is one where the four separate coil windings form an ovate shape 60 39 as shown in fig5 c such an ovate shape would appear in cross section as an egg with a more pointed profile formed by windings 64 39 66 39 on the inside of the toroidal shaped total coil 60 39 and a less rounded profile formed by windings 62 39 68 39 at the outside of the toroidal shape 60 39 thus in comparison with the cross sectional area shown in fig5 a the cross sectional areas of the coil windings 64 39 and 66 39 would be somewhat smaller than those of windings.