Multipole Aberration Correction System for Electron Microscopes
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Solution Overview
Problem
Current aberration correction systems in transmission electron microscopes can only correct aberrations up to the fourth order, limiting spatial resolution due to residual higher-order aberrations like fifth-order spherical aberration and sixth-order astigmatism, which restricts the range of electron beam incidence angles that can be corrected, thereby limiting diffraction aberration reduction.
Innovation Solution
An aberration correction system using three stages of multipole elements, each producing a field of 3-fold symmetry, with specific rotational positional relationships between the elements to cancel out 3-fold and 6-fold astigmatisms, producing a negative spherical aberration that improves spatial resolution and widens the range of correctable electron beam incidence angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the range of electron beam incidence angles is increased to reduce diffraction aberration, then spatial resolution is improved, but aberration correction becomes difficult due to limited correctable angle range
Solution Approach 1:
The patent changes the parameters of the multipole elements, specifically using different numbers of poles (e.g., six-pole, eight-pole, ten-pole elements) with different symmetry orders (3-fold, 4-fold, 5-fold symmetry). This parameter variation allows each element to correct different orders of aberrations effectively, enabling the system to maintain correction capability across a wider range of electron beam incidence angles, thereby improving spatial resolution without being constrained by a limited angle range.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively cancels out higher-order aberrations, enhancing spatial resolution and reducing diffraction aberration by correcting 3-fold and 6-fold astigmatisms while maintaining a negative spherical aberration, thus improving the microscope's imaging capabilities.
Implementation Method 1
each multipole element producing a magnetic or electric field of 3-fold symmetry with respect to an optical axis
Implementation Method 2
each multipole element producing a magnetic or electric field of 3-fold symmetry with respect to an optical axis
Implementation Method 3
an electron beam passing through two stages of multipole elements is corrected for aberrations
Data Source
Figure 1
Figure 2a~2g
Figure 3~4
AI summary
An aberration correction system is offered which is for use in an electronmicroscope and which produces a negative spherical aberration and corrects a higher-order aberration. The aberration correction system has threestagesof multipole elements (21, 22, 23) which respectively produce fields of 3-fold symmetry with respect to the optical axis (11). The middle stage of multipole element (22) produces the field of the 3-fold symmetry within a plane perpendicular to the optical axis (11). The rear stage of multipole element (23) also produces the field of the 3-fold symmetry within the plane perpendicular to the optical axis (11). Any two stages of multipole elements are disposed in directions not to cancel out the 3-fold fields. However, the three stages of multipole elements are so disposed as to cancel out 3-fold astigmatisms.