Patent ID: 6888145

Claim:
A particle optical corrector having multipole elements in the form of electrical quadrupole or magnetic quadrupole elements and octupole elements for eliminating chromatic aberration and spherical aberration of particle optical lenses, said particle optical corrector comprising: at least twelve quadrupole elements (Q 1 -Q 3 â€²â€³) and ten octupole elements (O 1 -O 4 ) with three quadrupole elements of said twelve quadrupole elements and two octupole elements of said ten octupole elements forming a group of elements (G) with a plurality of groups of elements (G 1 -G 4 ) being arranged one group behind another group along a straight optical axis; said multipole elements from said group of elements to said group of elements corresponding to one another in pairs (Q 1 and Q 1 â€²; Q 2 and Q 2 â€²; Q 3 and Q 3 â€²) and said multipole elements (Q 3 â€², Q 2 â€², Q 1 â€²) of a respective following said group of elements being positioned in reverse sequence along said straight optical axis to corresponding said multipole elements (Q 1 , Q 2 , Q 3 ) or a respective preceding said group of elements; the respective mutually corresponding multipole elements (Q 1 , Q 1 â€², Q 1 â€³, Q 1 â€²â€³; O 1 , O 1 â€², O 1 â€³, O 1 â€²â€³) are mirror symmetrical to respective center planes between each said group of elements, with said center plane between a first group of elements and a second group of elements defining a first plane of symmetry, said center plane between said second group of elements and a third group of elements defining a second plane of symmetry, said center plane between said third group of elements and a fourth group of elements defining a third plane of symmetry; at least two quadrupole elements of said at least twelve quadrupole elements generating an electrical quadrupole field and a magnetic quadrupole field and said at least two quadrupole elements being arranged mirror symmetrically to at least said second plane of symmetry; and, an additional octupole element being provided in said first plane of symmetry and said third plane of symmetry.