Precise centering and field characterization of magnetic quadrupole lenses

A setup to investigate fields of magnetic quadrupole lenses was designed and constructed. It allows the spatial position of the axis and the multipole structure of the field of a lens (or lenses) with aperture sizes from 11 mm to be determined. The technique employed is based on the measurements of the radial component of the magnetic induction vector using a Hall probe at the points located on the three dimensional surface with subsequent data processing using the Laplace equation. The article presents design and performance characteristics of the setup as well as results from the accuracy evaluations in the measurements of the centers and parasitic multipole field components of the magnetic quadrupole lenses in the integrated doublet.