Patent ID: 8373136

Claim:
An achromatic beam deflector device for deflecting a primary charged particle beam and providing the primary charged particle beam on an optical axis, comprising: a primary charged particle beam inlet; a primary charged particle beam outlet encompassing the optical axis; a magnetic deflection element adapted to generate a magnetic field; and an electrostatic deflection element adapted to generate an electric field overlapping the magnetic field, wherein at least one element chosen from the electrostatic deflection element and the magnetic deflection element is positioned to provide the electric field and the magnetic field in at least one arrangement chosen from: an arrangement in which the electric field is laterally offset with respect to the optical axis towards the direction of the incident primary beam, and an arrangement wherein the electric field is offset with respect to the magnetic field in a direction towards the beam outlet, wherein the at least one element is adjusted such that a trajectory of a primary charged particle beam bundle experiences an equal amount of positive and negative octopole effect about the optical axis.