A lens assembly having a magnetic lens assembly for a charged particle beam system is provided. The lens assembly includes: a first pole piece having a connecting portion of the first pole piece and a gap portion of the first pole piece, a second pole piece having a connecting portion of the second pole piece and a gap portion of the second pole piece, wherein the first pole piece and the second pole piece provide a gap at the respective gap portions, a coil for exciting the magnetic lens assembly, a centering element comprising a material that has a smaller Young's modulus than the material of the first and the material of the second pole piece, wherein the pole pieces are connected with each other at the respective connecting portions and have a centering element receiving portion towards the respective gap portion ends of the pole pieces.