Ellipsoidal Electrostatic Lens for Wide-Angle Particle Collimation
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Solution Overview
Problem
Conventional electrostatic lenses have a limited acceptance angle due to spherical aberration, restricting the measurement of charged particles to about ±20°, which hinders high sensitivity and energy resolution in electron spectroscopy and photoelectron diffraction, and require a large apparatus size due to the need for spherical aberration correction.
Innovation Solution
An electrostatic lens with an axially symmetric, non-spherical mesh and a configuration of electrodes that creates a concave surface towards the point source, allowing an acceptance angle of ±60° and high parallelism of charged particle trajectories, combined with a planar collimator plate for band-pass filtering and amplification, to achieve high sensitivity and energy resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional concentric spherical grids are used in retarding-voltage-type energy analyzer, then the analyzer can be constructed with simple geometry, but the charged particles are projected onto a spherical surface preventing planar microchannel plate amplification and limiting acceptance angle
Solution Approach 1:
The patent replaces the conventional spherical grid structure with an ellipsoidal grid arrangement. The first and second grids are positioned at the foci of the ellipsoid, creating a specific electric field distribution that enables planar projection of charged particles while maintaining large acceptance angle capability. This curved geometric arrangement resolves the contradiction by providing both large acceptance angle and compatibility with planar detection surfaces.
Solution Approach 2:
The invention transitions from spherical coordinate projection to planar coordinate projection by strategically positioning grids at ellipsoidal foci. This dimensional transformation allows charged particles entering within a large acceptance angle (±60° or wider) to be projected onto a planar detector surface, enabling the use of planar microchannel plates for signal amplification while maintaining large solid angle coverage.
2Ease of operation
If retarding-voltage-type energy analyzer is used, then energy analysis can be performed, but fluorescent X-ray cannot be removed and increases as acceptance angle is enlarged, becoming background noise
Solution Approach 1:
The patent introduces a dedicated X-ray removal mechanism by positioning a third grid between the sample and the first grid. This third grid is biased to repel or absorb fluorescent X-rays while allowing charged particles to pass through to the analysis region. By extracting the harmful X-ray component separately from the charged particle beam path, the system achieves both large acceptance angle capability and reduced X-ray background noise.
3Ease of operation
If ordinary electrostatic lenses are used, then beam deceleration can be achieved, but acceptance angle is limited to about ±20° due to spherical aberration
Solution Approach 1:
The patent employs an ellipsoidal grid configuration where the first and second grids are positioned at the foci of an ellipsoid. This specific curved geometry creates an electric field distribution that corrects spherical aberration while enabling wide acceptance angle. The ellipsoidal shape focuses charged particles from a wide angular range onto a planar surface without the blur associated with conventional spherical lenses, achieving both large acceptance angle (±60° or wider) and sharp focusing precision.
4Ease of operation
If spherical mesh is used to increase acceptance angle to about ±30°, then sensitivity can be improved, but spherical aberration correction requires larger apparatus size
Solution Approach 1:
The patent uses an ellipsoidal grid arrangement with foci positioned at specific locations to achieve aberration correction in a compact configuration. The ellipsoidal geometry naturally focuses particles from wide angles without requiring the large correction lenses needed in conventional spherical systems. This enables acceptance angles of ±60° or wider while maintaining a compact apparatus size, effectively resolving the size-angle tradeoff.
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 enables high sensitivity and energy resolution measurements over a large solid angle range, reduces apparatus size, and improves angular resolution, allowing for compact and efficient electron spectroscopy and diffraction analysis.
Implementation Method 1
an electrostatic lens is often used at the incident part of an energy analyzer in an apparatus for electron spectroscopy and this electrostatic lens takes in as much electrons as possible and lets the electrons enter into the analyzer after decelerating the electrons
Implementation Method 2
This electrostatic lens comprises a non-spherical mesh 2 having an aspherical surface, and one or more electrodes 11 to 15, and creates an electric field so that the charged particles emitted from a point source 7 within a specific solid angle range can enter into the analyzer
Implementation Method 3
creates an electric field so that the charged particles emitted from a point source 7 within a specific solid angle range can enter into the analyzer
Data Source
AI summary
Provided is a compact device which captures, over a large solid angle range, electrically charged particles emitted from a point source and parallelizes the trajectories of said charged particles. The present invention is configured from: an electrostatic lens comprising a plurality of axisymmetric electrodes (10-14) and an axisymmetric aspherical mesh (2) which has a surface that is concave away from the point source; and a flat collimator plate (3) positioned coaxially with the electrostatic lens. The acceptance angle for the electrically charged particles generated from a point source (7) is ±30° or greater. The shape of the aspherical mesh (2), and the potentials and the positions of a ground electrode (10) and application electrodes (11-15) are adjusted so that the trajectories of the electrically charged particles are substantially parallelized by the electrostatic lens. The electrostatic lens and the flat collimator plate are positioned on a common axis.