Patent ID: 11942316

Abstract:
An aperture device (31) is described, which is attachable to a lens system (13). The lens system (13) is arranged to form a particle beam of charged particles, emitted from a sample surface (Ss). The aperture device (31) comprises an end surface (S) which is to be arranged facing the sample surface (Ss), at least one aperture (38) arranged in the end surface (S), a length axis (32) which extends through the centre of said at least one aperture (38), and at least one gas outlet (10), which is arranged at a transverse distance (T) perpendicular from the length axis (32), and is arranged to direct gas into a volume between at least one aperture (38) and the sample surface (Ss). The end surface (S) within a distance, equal to ⅓ of the transverse distance (T), perpendicular from the length axis (32) has a variation along the length axis (32) being smaller than ⅙ of the transverse distance (T).