Patent ID: 6646261
Filing Date: 2003-11-11
Classification: H01J

Abstract:
A particle-optical apparatus which includesa particle source for producing a primary beam of electrically charged particles that travel along an optical axis of the apparatus, a specimen carrier for a specimen to be irradiated by means of the apparatus, a focusing device for forming a focus of the primary beam in the vicinity of the specimen carrier by means of electrostatic electrodes, and a detector that has a detector surface for detecting electrically charged particles that emanate from the specimen in response to the incidence of the primary beam, which detector is arranged ahead of the focusing device, viewed in the propagation direction of the primary beam, and which detector surface is provided with a central bore for the passage of the primary beam, characterized in that the detector is provided with a central electrode at the area of the central bore and that the particle-optical apparatus is provided with a power supply for adjusting such a voltage across the central electrode that at the area of the detector surface the central electrode exerts a repulsive force on the particles that emanate from the specimen.