Field mapping the dipole magnets for the University of Colorado energy-loss spectrograph

Using a comparatively inexpensive mechanical hoop and Hall effect probe it was possible to map the dipole magnets of the University of Colorado's energy-loss spectrograph with a precision of 1 part in 104 for the integrated value of magnetic field along bending radii through the magnets. The limiting factors in precision were an instability of field measurements caused by electronic noise and neglect in interpolation calculations of a measured asymmetry of the magnetic field about the median plane. Hall effect errors caused by regions with gradients and higher derivatives in the magnetic field, although potentially a serious problem, were found less important in the present case because of the small extent of such regions compared to the larger uniform field regions.