Objective lens arrangement usable in particle-optical systems

A particle optical inspection system comprising:

• a charged particle source;
• an objective lens arrangement;
• and
• a charged particle detector;
• wherein the objective lens arrangement comprises:
• an object mount for mounting an object to be processed in an object plane;
• a first pole piece and a second pole piece, wherein the first and second pole pieces are substantially rotationally symmetric with respect to an axis of symmetry, wherein a radial inner end of the first pole piece is disposed at a distance from a radial inner end of the second pole piece to form a first gap, wherein the second pole piece is closer to the object mount than the first pole piece;
• a first excitation coil for generating a focusing magnetic field in the first gap;
• a beam tube extending through a bore formed by the radial inner end of the first pole piece;
• and
• a first voltage source for supplying a voltage to the beam tube such that the beam tube is at a potential different from a potential of the second pole piece,
• wherein the bore extends from a first plane where a diameter of the bore is a minimum diameter to a second plane in which a front surface portion of the first pole piece is disposed, wherein the front surface portion is the portion of the first pole piece disposed closest to the object plane, wherein a diameter of the bore at the front surface portion is a front diameter, wherein a difference between the front diameter and the minimum diameter is more than 10 mm, and wherein a distance between the first and second plane is more than 5 mm,
• wherein the bore has a tapered portion and the bore diameter increases with decreasing distance from the object plane.