An einzel lens with a diagonal-slit central electrode to combine steering and focusing of a low energy ion beam

In many applications of the simple three-element einzel lens, such as injecting a low energy ion beam into a high-field Penning trap, there is a need for small-angle steering as well as focusing of the beam. We have analyzed a diagonalslit cylinder serving as the middle electrode of such a lens and have shown that such an electrode configuration significantly diminishes the aberration associated with such a deflection.