A magnetic lens configured to apply a magnetic field to a charged particle beam is provided. The magnetic lens may include an outer pole piece and an inner pole piece. The outer pole piece may have at least two sectors and at least two slots. The magnetic lens may also have a primary coil winding interposed between the outer pole piece and the inner pole piece. In addition, the magnetic lens may have a number of sector coil windings, and each sector of the outer pole piece may be coupled to one sector coil winding. A magnetic potential of the outer pole piece relative to the inner pole piece may be generated by applying a current to the primary coil winding. A separate magnetic potential of each sector may also be generated by applying a current to the respective sector coil windings of each sector of the outer pole piece.