Particle Optical Device Magnet Assembly Thermal Isolation
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Solution Overview
Problem
Conventional electron microscopes face issues with temperature gradients and drifts due to heat generated by coil energization, affecting the geometry and homogeneity of magnetic fields, leading to undesirable variations in deflecting fields.
Innovation Solution
The particle optical device incorporates trench-shaped coil arrangements with larger cross-sections and thermal isolation of coil wires from pole plates, along with the use of permanent magnets to reduce heat input and maintain magnetic field stability, and employs non-magnetic, electrically conducting layers to manage heat dissipation and maintain constant electron energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If coils are energized to generate magnetic fields for beam deflection, then the deflecting field strength is improved, but temperature gradients and heat transfer to pole plates cause geometry changes and field instability
Solution Approach 1:
A coil mount with gap structure is introduced as an intermediary between the coils and pole plates. The gap (50-500 μm) acts as a thermal barrier that reduces heat transfer from energized coils to pole plates, while the coil mount provides mechanical support and positioning. This mediator structure allows the system to maintain both strong deflecting fields and stable pole plate geometry.
Solution Approach 2:
The trench cross-section in the pole plate is optimized to provide adequate space for coil wires while maintaining precise surface contours. The trench dimensions are carefully controlled to balance two requirements: sufficient volume for coil windings (to reduce resistance and heat generation) and minimal impact on the magnetic pole surface geometry (to maintain field homogeneity).
2Loss of energy
If coil wire cross section is increased to reduce heat generation, then heat production is reduced, but space for coils in the pole plate is limited
Solution Approach 1:
The trench cross-sectional area and dimensions are optimized to provide maximum volume for coil wires within the constraints of the pole plate structure. This allows increased coil wire cross-section (reducing resistance and heat generation) while maintaining adequate space for the magnetic pole surfaces and overall compact design.
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
This configuration reduces heat generation and transfer, stabilizes the magnetic field, and minimizes temperature-induced variations, ensuring precise beam deflection and improved operational stability in electron microscopes.
Implementation Method 1
Coils are fitted into the surfaces of the pole plates, which coils may be energized by a flow of current. A magnetic field which is homogeneous to a high degree of approximation is then generated on the areas surrounded by the coil wires.
Implementation Method 2
For beam guiding, magnetic fields are usually employed
Implementation Method 3
Conventionally, the heat generated by energizing the coils is dissipated through the pole plates. The present inventors have now found that thereby, temperature gradients are caused, which affect the geometry of the pole plates.
Implementation Method 4
a particle optical device including a coil mount is provided, on which coil mount the coil wires are supported, wherein a gap is provided between the coil mount and the pole plate. According to this structure, in some embodiments the heat transfer from the coil wires to the pole plates via heat conduction is reduced
Data Source
AI summary
A particle optical apparatus has a particle source for generating at least one beam of charged particles, and a magnet arrangement having two pole plates, which are arranged spaced apart from one another, such that the at least one beam of charged particles in operation passes through the pole plates, wherein trenches are provided in the pole plates, in which trenches coil wires are arranged. The trenches, when viewed in a cross section transverse to an extension direction of the trenches, have a smaller width in a region of a surface of the pole plates, than in a region arranged at a distance from the surface.