An ion beam column including an ExB mass filter, comprising: an ion source for providing ions of different charge-to-mass ratios; a first lens for first forming the ions from the ion source into a beam along a first axis; a first ExB mass filter stage that provides a first beam deflection away from the first axis, the first beam deflection depending on the charge-to-mass ratio of each ion in the beam, the first axis being a symmetry axis of the first ExB mass filter stage; a rotational symmetry axis, the rotational symmetry axis being oriented perpendicular to the plane including the first axis and the direction of first beam deflection, the rotational symmetry axis being offset parallel to the first beam deflection; characterized by: a second ExB mass filter stage positioned such that it results from the first ExB mass filter stage by a rotation of 180 degrees around the rotational symmetry axis, a symmetry axis of the second ExB mass filter stage being a second axis, the second ExB mass filter stage providing a second beam deflection opposite to that of the first beam deflection, the combination of the deflections of the first and second ExB mass filter stages being equal to the displacement between the first and second axes for one of the ions of different charge-to-mass ratios exiting the second ExB mass filter stage; a mass separation aperture for passing less than all the ions from the second ExB mass filter stage, the mass separation aperture being centered on the second axis; and a second lens receiving ions from the second ExB mass filter and focusing those ions onto a substrate surface, the second ExB mass filter stage substantially canceling the chromatic aberration from the first ExB mass filter stage at the substrate surface. an ion source for providing ions of different charge-to-mass ratios; a first lens for first forming the ions from the ion source into a beam along a first axis; a first ExB mass filter stage that provides a first beam deflection away from the first axis, the first beam deflection depending on the charge-to-mass ratio of each ion in the beam, the first axis being a symmetry axis of the first ExB mass filter stage; a rotational symmetry axis, the rotational symmetry axis being oriented perpendicular to the plane including the first axis and the direction of first beam deflection, the rotational symmetry axis being offset parallel to the first beam deflection; characterized by: a second ExB mass filter stage positioned such that it results from the first ExB mass filter stage by a rotation of 180 degrees around the rotational symmetry axis, a symmetry axis of the second ExB mass filter stage being a second axis, the second ExB mass filter stage providing a second beam deflection opposite to that of the first beam deflection, the combination of the deflections of the first and second ExB mass filter stages being equal to the displacement between the first and second axes for one of the ions of different charge-to-mass ratios exiting the second ExB mass filter stage; a mass separation aperture for passing less than all the ions from the second ExB mass filter stage, the mass separation aperture being centered on the second axis; and a second lens receiving ions from the second ExB mass filter and focusing those ions onto a substrate surface, the second ExB mass filter stage substantially canceling the chromatic aberration from the first ExB mass filter stage at the substrate surface. a second ExB mass filter stage positioned such that it results from the first ExB mass filter stage by a rotation of 180 degrees around the rotational symmetry axis, a symmetry axis of the second ExB mass filter stage being a second axis, the second ExB mass filter stage providing a second beam deflection opposite to that of the first beam deflection, the combination of the deflections of the first and second ExB mass filter stages being equal to the displacement between the first and second axes for one of the ions of different charge-to-mass ratios exiting the second ExB mass filter stage; a mass separation aperture for passing less than all the ions from the second ExB mass filter stage, the mass separation aperture being centered on the second axis; and a second lens receiving ions from the second ExB mass filter and focusing those ions onto a substrate surface, the second ExB mass filter stage substantially canceling the chromatic aberration from the first ExB mass filter stage at the substrate surface.