Iron shimming of superconductive rotating dipoles

The design rules and constraints of a superconductive rotating dipole, aimed at providing a 9-10 T field in the central bore for material and vacuum polarization researches, are briefly reviewed. A careful control of |B| maxima is imperative: since an ideal cos /spl theta/ configuration can not be exactly implemented by coil without spacers, a |B| peak develops at a coil border. An economical correction of it at the price of an non-essential increase of field inhomogeneity, consists in the insertion of completely saturated iron shims in the polar region. The effect of these shims an coil ends is treated as well. Simple analytic rules and TOSCA simulations are presented: stray fields are found to be negligible. >