Double stage charged particle beam energy width reduction system for charged particle beam system

A charged particle beam velocity distribution width reduction system positioned prior to an objective lens 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 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 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.

A method of operating a charged particle beam velocity distribution width reduction system comprising a z-axis along an optical axis, a 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 being a second Wien filter element, a first quadrupole element and a second quadrupole element, comprising:

• shaping the charged particle beam with a first charged particle selection element;
• exciting the first and the second quadrupole element so that the field of the first quadrupole element and the field of the second quadrupole element image in a y-z-plane a source-like location in a virtual manner;
• exciting the first element acting in a focusing and dispersive manner and the second element acting in a focusing and dispersive manner so that, in an x-z plane, the charged particles seem to originate from a source-like location by the combination of a field of the first element acting in a focusing and dispersive manner, a first quadrupole element field, a field of the second element acting in a focusing and dispersive manner, and a second quadrupole element field;
• and
• selecting velocity dependently the charged particles with the second charged particle selection element.