Patent ID: 7679054

Claim:
A charged particle beam velocity distribution width reduction system for a charged particle beam with the z-axis extending along the optical axis, comprising: a first element acting in a focusing and dispersive manner, the first element acting in a focusing and dispersive manner being a first Wien filter element; a second element acting in a focusing and dispersive manner, the second element acting in a focusing and dispersive manner being a second Wien filter element; a first quadrupole element 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, wherein the first quadrupole element is adapted for at least partly compensating the focusing effect of the first Wien filter element; a second quadrupole element 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, wherein the second quadrupole element is adapted for at least partly compensating the focusing effect of the second Wien filter element; a first charged particle selection element being positioned, in beam direction, before the first element acting in a focusing and dispersive manner, wherein the first charged particle selection element is adapted to be an angle dependent charged particle selection element; and a second charged particle selection element being positioned, in beam direction, after the first element acting in a focusing and dispersive manner, wherein the second charged particle selection element is adapted to be a velocity dependent selection element, wherein the first element acting in a focusing and dispersive manner and the second element acting in a focusing and dispersive manner are built, connected, or both, to a control unit so that different absolute values of dispersion are realized.