Patent ID: 7999225

Claim:
Charged particle source for producing a beam of charged particles, comprising a charged particle emitting surface emitting charged particles, a lens for forming an image of the charged particle emitting surface, said lens having an optical axis a beam limiting diaphragm for limiting of the beam, embodied in such a way that at least two beams are formed, a central beam going through the middle of the lens and an eccentric beam going eccentrically through the lens, a first deflector embodied to deflect one of the beams towards the axis, and an energy selecting diaphragm showing an energy selecting aperture for passing a part of the eccentric beam and a central aperture for passing the central beam, said energy selecting diaphragm positioned between the particle emitting surface and the deflector, and a second deflector to align the eccentric beam on the energy selecting aperture, the source configured such that when the eccentric beam is focused and aligned on the energy selecting aperture using the second deflector, the second deflector simultaneously deflects the central beam to such an extent that the central beam is blocked by the energy selecting diaphragm.