Monochromator with Offset Cylindrical Lenses for Energy Resolution
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Solution Overview
Problem
Conventional monochromators are complex, expensive, and require high precision, leading to issues like off-axis aberrations, energy spread increase, and unstable emission current, which hinder achieving high energy resolution for charged particle beam applications.
Innovation Solution
A monochromator design featuring a two-stage cylindrical lens offset from the optical axis with a slit between them, where the first lens deflects and disperses the charged particle beam, and the second lens corrects the beam's path to match the original axis, minimizing secondary aberrations and energy dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional monochromators use complex optical systems with multiple lenses and high precision components, then energy resolution can be improved, but device complexity and manufacturing cost increase significantly
Solution Approach 1:
The monochromator is divided into two functional stages: a first cylindrical lens for beam deflection and energy dispersion, and a second cylindrical lens for beam path correction. This segmentation allows each component to perform a specific function with simpler design, reducing overall system complexity while maintaining energy resolution performance.
Solution Approach 2:
The patent introduces an asymmetric configuration where the cylindrical lenses are deliberately offset from the optical axis by a specific distance. This asymmetric positioning creates controlled off-axis aberrations that are then corrected by the second lens, achieving energy resolution without requiring symmetric high-precision optical systems.
2Measurement precision
If conventional monochromators use off-axis chromatic aberration of cylindrical lenses, then energy analysis can be achieved, but off-axis aberrations and beam profile degradation occur
Solution Approach 1:
The patent converts the harmful off-axis aberration into a beneficial effect by deliberately positioning the cylindrical lenses off-axis. The first lens uses the off-axis chromatic aberration for energy dispersion, while the second lens corrects the resulting beam profile distortion, thus converting the harmful aberration into a useful energy separation mechanism.
Solution Approach 2:
The patent changes the positional parameter of the cylindrical lenses from on-axis to off-axis by a specific distance. This parameter change enables the system to utilize off-axis chromatic aberration for energy dispersion while the second lens compensates for the resulting beam degradation, achieving both energy analysis and beam quality.
3Reliability
If conventional monochromators require high precision fabrication and multiple power sources, then performance can be maintained, but manufacturing cost and system complexity increase
Solution Approach 1:
The patent employs cylindrical lenses with relaxed precision requirements compared to conventional monochromators. By using off-axis positioning and two-stage correction, the system achieves acceptable performance with less expensive, easier-to-manufacture components, reducing overall manufacturing cost while maintaining sufficient reliability for charged particle beam applications.
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 design achieves an excellent charged particle beam profile with reduced energy spread and stabilized current, improving energy resolution and simplifying the mechanical and electrical structure, while being cost-effective and suitable for various charged particle beam apparatuses.
Implementation Method 1
The cylindrical lens is a charged particle lens in which a rectangular opening is formed at the center of three electrodes 11, a high voltage is applied to the center electrode, and two electrodes on both sides are used as ground voltages. An insulating material 12 is provided between the three electrodes 11. Energy of electrons is decelerated almost close to 0 near the center electrode, a component that passes through the outside of the optical axis of the cylindrical lens is selected, and energy of charged particles is analyzed using an energy dispersion generated by the chromatic aberration of the lens axis.
Implementation Method 2
The monochromator of the FEI Co., Ltd. is a monochromator MC for selecting the off-axis component of an electron source by an aperture, passing the selected component through the outside of an electrostatic lens, and performing monochrome (i.e., enlarging or reducing energy) on the component by performing spectroscopy on the energy.
Implementation Method 3
A Wien Filter type monochromator MC is mounted on the electron gun of a transmission electron microscope (TEM) or scanning transmission electron microscope (STEM), energy is subject to spectroscopy, and monochrome may be performed on the energy (i.e., an energy distribution may be reduced)
Implementation Method 4
a 4-stage electrostatic deflector is mounted on the electron gun of a transmission electron microscope (TEM) or scanning transmission electron microscope (STEM), energy is subject to spectroscopy, monochrome may be performed on the energy (i.e., an energy distribution may be reduced)
Data Source
AI summary
Disclosed herein are a monochromator and a charged particle beam apparatus including the same. The monochromator may include a first electrostatic lens configured to have a charged particle beam discharged by an emitter incident on the first electrostatic lens, refract a ray of the charged particle beam, and include a plurality of electrodes and a second electrostatic lens spaced apart from the first electrostatic lens at a specific interval and configured to have a central axis disposed identically with a central axis of the first electrostatic lens, have the charged particle beam output by the first electrostatic lens incident on the second electrostatic lens, refract the ray of the charged particle beam, and comprise a plurality of electrodes. Accordingly, there is an advantage in that a charged particle beam can have an excellent profile even after passing through the monochromator.