Wien Filter Monochromator for Reduced Boersch Effect
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Solution Overview
Problem
Existing charged particle microscopy and microanalysis systems suffer from the Boersch effect, which increases energy spread due to Coulomb interactions in charged particle beams, impairing energy resolution and limiting the ability to analyze materials at atomic scales.
Innovation Solution
Implementing a Wien filter with a specific excitation parameter (ϕ > 3π/4) and a monochromator configuration that includes a dispersing element and a selector to disperse and focus charged particles, reducing the Boersch effect and narrowing the energy distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a charged particle beam is used for microscopy and microanalysis, then imaging and material analysis can be performed at atomic scales, but the Boersch effect increases energy spread and deteriorates energy resolution
Solution Approach 1:
The patent applies preliminary anti-action by introducing a monochromator system before the beam reaches the sample to pre-compensate for energy spread. The Wien filter and selector are configured to counteract the Boersch effect by selecting a narrow energy range of electrons, thereby reducing the harmful energy spread before it affects the measurement precision
Solution Approach 2:
The patent changes physical parameters by adjusting the excitation parameter φ of the Wien filter to values greater than 3π/4 (specifically around 4.3), and by optimizing the selector aperture width and position. These parameter changes optimize the monochromator's ability to reduce energy spread while maintaining sufficient beam current
2Measurement precision
If the beam current is increased to improve signal strength, then measurement sensitivity improves, but the Boersch effect intensifies and energy resolution deteriorates
Solution Approach 1:
The patent replaces direct mechanical/electrical beam intensity control with an optical filtering approach using the monochromator. Instead of simply increasing beam current to improve signal, the system uses the Wien filter and selector to optically filter the electron beam, achieving high signal-to-noise ratio through improved energy resolution rather than brute-force current increase
Solution Approach 2:
The patent optimizes the balance between beam current and energy resolution by adjusting the selector aperture characteristics and Wien filter excitation. This allows operation at higher beam currents (5 nA to 50 nA at monochromator entrance) while maintaining energy resolution by compensating for the increased Boersch effect through the monochromator's energy selection
3Measurement precision
If a monochromator is introduced to reduce energy spread, then energy resolution improves, but device complexity increases
Solution Approach 1:
The patent achieves multi-functionality by designing the monochromator to simultaneously perform energy selection, beam focusing, and Boersch effect compensation. The Wien filter and selector configuration not only narrows energy distribution but also optimizes beam current transmission, thereby reducing the need for separate compensation devices and minimizing overall system complexity
Solution Approach 2:
The patent reduces operational complexity by optimizing the Wien filter excitation parameter to a specific range (φ > 3π/4, particularly around 4.3) and selector aperture dimensions (0.3 μm to 1.3 μm). These optimized parameters simplify the operational procedure and reduce the need for complex real-time adjustments during measurement
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
Improves energy resolution and spatial resolution, enabling precise measurement of material properties and detailed analysis of molecular structures, particularly in electron energy loss spectroscopy, by attenuating the Boersch effect and enhancing signal-to-noise characteristics.
Implementation Method 1
The Wien filter can be configured to disperse particles of a beam of charged particles by energy in a dispersion plane. The dispersion plane can be parallel with the beam axis.
Implementation Method 2
The optical element can be configured to focus the beam of charged particles toward the beam axis.
Implementation Method 3
the Boersch effect describes an increase in energy spread (e.g., a wider beam energy distribution) due at least in part to Coulomb interactions between the particles in a charged particle beam
Data Source
AI summary
The present disclosure describes systems, methods, algorithms, and non-transitory media storing computer-readable instructions for reducing the Boersch effect using dispersive optics, in various embodiments. A charged particle optical device can include a Wien filter disposed on a beam axis. The Wien filter can be configured to disperse particles of a beam of charged particles by energy in a dispersion plane. The dispersion plane can be parallel with the beam axis. The device an include an optical element disposed on the beam axis downstream of the Wien filter. The optical element can be configured to focus the beam of charged particles toward the beam axis. The device can also include a selector. The selector can be disposed on the beam axis at a position substantially corresponding to a third crossover plane downstream of the optical element.