Multi-pole Wien Filter for Electron Microscope Aberration Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing Wien filters face challenges in achieving a perfect match of electric and magnetic dipole fields, leading to aberrations and astigmatism in imaging systems, particularly in compact designs required for applications like electron microscopes, where a strict adherence to the Wien Condition is necessary to minimize derivative aberrations and maintain imaging quality.
Innovation Solution
A multi-pole type Wien filter design incorporating a 12-electrode electric device with 8-fold symmetry and a cylindrical 4-coil magnetic device, each generating dipole fields with minimal 3rd order harmonics, and a compact structure that allows for a good match of on-axis electric and magnetic fields, along with the introduction of an electric quadrupole field for astigmatism compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a compact Wien filter design is used, then the device size is reduced, but the match between electric and magnetic dipole fields deteriorates, leading to increased aberrations and astigmatism
Solution Approach 1:
The Wien filter is divided into multiple functional sections with distinct electrode and coil arrangements. The electric device includes multiple electrode pairs arranged to generate dipole fields, while the magnetic device includes multiple coil pairs arranged to generate corresponding magnetic dipole fields. This segmentation allows independent optimization of each section's field distribution to maintain precision in compact configurations.
Solution Approach 2:
The electrode and coil arrangements employ asymmetric geometries with specific angular orientations (e.g., 45-degree angles between adjacent electrode pairs) to compensate for field mismatches. The asymmetric positioning of electrodes and coils allows for precise control of field distribution patterns, enabling better field matching in reduced-size configurations compared to symmetric traditional designs.
2Device complexity
If traditional dipole field configuration is used, then the structure is simple, but 3rd order harmonics and astigmatism increase
Solution Approach 1:
Different regions of the Wien filter employ different field configurations. The central region uses a dipole field configuration for primary particle separation, while peripheral regions incorporate quadrupole field elements through specifically positioned electrodes and coils. This local variation in field quality allows suppression of 3rd order harmonics and astigmatism in critical areas while maintaining overall structural simplicity.
Solution Approach 2:
The invention changes the geometric parameters of electrodes and coils, including their angular positions, spacing, and dimensions, to minimize harmonic content. By optimizing parameters such as the angle between adjacent electrode pairs and the relative positioning of magnetic coils, the design achieves reduced 3rd order harmonics and astigmatism without requiring fundamentally complex structures.
3Manufacturing precision
If field matching is prioritized, then aberrations are minimized, but the device complexity and size increase
Solution Approach 1:
The electric and magnetic field-generating components are merged into a unified multi-pole configuration where electrodes and coils are interlaced and share common structural support. The electric device and magnetic device are integrated such that their field patterns are spatially correlated, achieving field matching through their combined geometric arrangement rather than through separate complex adjustment mechanisms.
Solution Approach 2:
The multi-pole electrode and coil structures serve multiple functions simultaneously: they generate the primary dipole fields for particle separation, provide quadrupole field components for astigmatism compensation, and create higher-order field patterns for harmonic suppression. This multi-functionality achieves superior field matching without proportionally increasing structural complexity.
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 design effectively minimizes aberrations and astigmatism, achieving a better match of electric and magnetic fields, thereby enhancing the imaging quality and compactness of Wien filters, making them suitable for applications in electron microscopes and other imaging systems.
Implementation Method 1
The electric device generates an electric dipole field in a direction perpendicular to an optical axis of the Wien filter
Implementation Method 2
The magnetic device generates a magnetic dipole field in a direction perpendicular to the optical axis of the Wien filter
Implementation Method 3
Wien filter is based on the principle that the magnetic force of a magnetic field acting on a charged particle depends on the velocity vector thereof, but the electric force of an electric field acting on a charged particle does not
Data Source
AI summary
This invention provides a multi-pole type Wien filter, which acts more purely approaching its fundamentally expected performance. A 12-electrode electric device acts as an electric deflector,or acts as an electric deflector and an electric stigmator together. A cylindrical 4-coil magnetic device with a magnetic core acts as a magnetic deflector. Both can produce a dipole field while only incurring a negligibly-small 3rd order field harmonic. The magnetic core enhances the strength and more preciously regulates the distribution of the magnetic field originally generated by the coils. Then two ways to construct a Wien filter are proposed. One way is based on both of the foregoing electric and magnetic devices, and the other way is based on the foregoing electric device and a conventional magnetic deflector. The astigmatism in each of such Wien filters can be compensated by the electric stigmator of the electric device.