Deflector Coil Configuration for Hexapole Field Cancellation
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Solution Overview
Problem
Existing electron beam deflectors in electron microscopes produce non-uniform magnetic fields, leading to distortion of the electron beam due to prominent hexapole fields, which hinder precise deflection.
Innovation Solution
A deflector system with six coils wound at 30-degree intervals around an annular core, where two sets of coils produce identical deflecting magnetic fields with opposite hexapole fields, canceling each other out to minimize distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a deflector is designed with coils wound around an annular core to produce deflecting magnetic fields, then the electron beam can be deflected, but hexapole fields are produced in addition which distort the electron beam
Solution Approach 1:
The deflector coils are segmented into multiple sets (first coil set and second coil set) with specific winding directions and electromotive force ratios. Each coil set produces both deflecting magnetic fields and hexapole fields, but the hexapole fields from the two sets are opposite in polarity and cancel each other out, while the deflecting magnetic fields are identical in direction and add up constructively.
Solution Approach 2:
The patent employs asymmetric winding configurations where the first coil set and second coil set have different numbers of coils (3 coils in first set, 2 coils in second set) and different electromotive force relationships (second coil has twice the electromotive force of the first coil). This asymmetric design enables selective cancellation of hexapole fields while maintaining strong deflecting magnetic fields.
2Manufacturing precision
If the hexapole fields are weakened to deflect the electron beam without distortion, then the beam quality is improved, but the deflector design becomes more complex with multiple coil sets and specific electromotive force relationships
Solution Approach 1:
The patent specifies precise parameter relationships among the coils including the electromotive force ratio (second coil is twice that of the first coil), winding directions (first, third, fourth, sixth coils in one direction; second, fifth coils in opposite direction), and angular intervals (30 degrees between adjacent coils). These controlled parameter changes enable hexapole field cancellation while maintaining manageable device complexity through systematic design rules.
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 enables precise deflection of charged particle beams like electron beams without distortion, maintaining a uniform magnetic field and reducing the size of the deflector compared to traditional designs.
Implementation Method 1
The coils are electrically energized to produce magnetic fields for deflecting the electron beam
Implementation Method 2
produce magnetic fields for deflecting the electron beam
Data Source
AI summary
There is provided a deflector that produces only a weak resulting combined hexapole field. The deflector (100) has first to sixth coils (11-16). The first to third coils (11-13) are equal in direction of energization. The fourth to sixth coils (14-16) are equal in direction of energization. The first coil (11) and fourth coil (14) are opposite in direction of energization. The first, third, fourth, and sixth coils (11, 13, 14, 16) are equal in electromotive force. The second coil (12) is equal in electromotive force to the fifth coil (15) and twice the electromotive force of the first coil (11).