Wien Filter Field Leakage Reduction via Shielding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Wien filters in imaging systems, particularly in high-resolution scanning electron microscopes, face challenges in maintaining imaging quality due to fields-mismatch and magnetic field leakage in the fringe areas, leading to aberrations and off-axis deviations.
Innovation Solution
A field-isolating device comprising field-terminating plates and a field-terminating tube, made of electric and magnetic conductors, is designed to suppress magnetic flux leakage and improve the match between electric and magnetic dipole fields, reducing fields-mismatch in the far fringe areas and enhancing the Wien Condition compliance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Wien filter is used in imaging system, then particle separation capability is improved, but magnetic field leakage causes aberrations and off-axis deviations
Solution Approach 1:
A magnetic shielding structure made of high-permeability material is introduced as an intermediary between the Wien filter and the imaging system. This shielding structure provides a preferential path for magnetic flux, confining the magnetic field within the filter region and preventing leakage into the imaging path, thereby eliminating aberrations while preserving particle separation capability
Solution Approach 2:
The Wien filter system is segmented into distinct functional regions: the particle separation region with electric and magnetic fields, and the imaging region with shielded fields. The magnetic shielding structure creates clear spatial separation between these regions, allowing independent optimization of each function without mutual interference
2Object-affected harmful factors
If field-terminating plates are added to suppress magnetic flux leakage, then magnetic field confinement is improved, but device complexity increases
Solution Approach 1:
The magnetic shielding structure serves multiple functions simultaneously: it confines magnetic flux within the Wien filter, shields the imaging system from magnetic interference, and provides structural support for the filter assembly. This multi-functionality reduces the need for additional separate components, thereby limiting complexity increase
Solution Approach 2:
The magnetic shielding structure is designed as a nested configuration where inner shielding elements are positioned within outer shielding elements, creating concentric zones of magnetic field confinement. This nested arrangement efficiently contains magnetic flux with minimal material usage and compact geometry
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 solution effectively reduces aberrations and off-axis deviations, improving imaging quality by minimizing fields-mismatch and magnetic field leakage, thus enhancing the performance of Wien filters in high-resolution imaging systems.
Implementation Method 1
The two field-terminating plates and the field-terminating tube are configured to make an electric dipole field and a magnetic dipole field leaking out of the Wien filter vanish away rapidly outside the field-isolating device
Implementation Method 2
the electric force and magnetic force acting on the particle will be opposite to each other and perpendicular to the moving direction of the particle, hence generating a total force as shown in Equation (1.1). F=q·(E1−ν·B1)
Implementation Method 3
The twelve electrodes are excited to generate an electric dipole field in a direction perpendicular to the optical axis
Implementation Method 4
The four coils are excited to generate a magnetic dipole filed in a direction perpendicular to the optical axis
Data Source
AI summary
This invention provides a design of Wien filter for satisfying Wien Condition so as to ensure the Wien filter's performance. At first, to minimize the magnetic flux leaking out of the Wien filter, the invention proposes three measures to form a magnetic circuit to cover the magnetic device of a Wien filter respectively. The measures especially benefit a Wien filter acting as beam separator or Monochromator in a high resolution SEM. Secondly, based on the Wien filter proposed in cross-reference, several ways are provided for reducing the dissatisfaction of Wien Condition within the Wien filter, which especially modify either or both of the distribution shapes of the on-axis electric and magnetic dipole fields at two ends of the Wien filter. These ways provide more flexibility to reduce the dissatisfaction of Wien Condition in a Wien filter to a given degree at a reasonable manufacturing cost.