The present invention relates to e.g. a charged particle beam energy width reduction system for a charged particle beam with a z-axis along the optical axis and a first and a second plane, comprising, a first element (110) acting in a focusing and dispersive manner, a second element (112) acting in a focusing and dispersive manner, a first quadrupole element (410) being positioned such that, in operation, a field of the first quadrupole element overlaps with a field of the first element acting in a focusing and dispersive manner, a second quadrupole element (412) being positioned such that, in operation, a field of the second quadrupole element overlaps with a field of the second element acting in a focusing and dispersive manner, a first charged particle selection element (618) being positioned, in beam direction, before the first element acting in a focusing and dispersive manner, and a second charged particle selection element (616;716) being positioned, in beam direction, after the first element acting in a focusing and dispersive manner. Thereby, a virtually dispersive source-like location without an inherent dispersion limitation can be realized.