A radial coil probe for quadrupole magnet measurements

This note describes a rotating coil probe of ''radial-winding geometry'' for the measurements of the magnetic center, quadrupole fields and multipole coefficients of quadrupole magnets. The active length of the coil is longer than the magnet length, so that all the measurements will be integrated values along the longitudinal direction of the magnets. Errors of the measurements due to the fabrication tolerances of the coil are discussed