We have developed several magnetic-coil based beamline elements for focusing and steering electron beams.
The steering coil set consists of four coils, arranged in a square geometry around the beam pipe. In the beam steering setting, equal currents are sent through opposite coils, creating an on-axis magnetic field perpendicular to the electron beam. The two sets of opposite coils allow controlled deflection of the electron beam in both directions perpendicular to the beamline axis.
By sending equal currents through all coils, with the current direction through each of the coils such that magnetic field is cancelled on axis, the square coil set becomes a quadrupole lens. A quadrupole lens focuses the beam in one perpendicular direction while simultaneously defocusing in the other. It can be used to create a line focus or to correct for astigmatism of the beam.