Orthogonal Acceleration Grid Aperture Design for Mass Spectrometer
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Solution Overview
Problem
In orthogonal acceleration time-of-flight mass spectrometers, electric field penetration between acceleration stages causes ion deflections and baseline noise, leading to degraded performance due to grid scattering and stray ions impinging on intermediate electrodes.
Innovation Solution
A grid configuration with reduced spacing between wires in the primary beam axis direction and increased spacing in the orthogonal direction is implemented, creating rectangular apertures that obstruct stray ions at grazing incidence, reducing artifact peaks and maintaining transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a grid electrode is used to separate acceleration stages, then field penetration is reduced, but grid scattering causes ion deflections and artifact peaks
Solution Approach 1:
The patent applies different wire spacing configurations to different regions of the grid. The grid has reduced spacing between wires in the primary beam axis direction (perpendicular to grid plane) and increased spacing in the orthogonal direction (parallel to grid plane). This creates rectangular apertures that are optimized to block stray ions at grazing incidence while maintaining transmission for normally incident ions, thus addressing both field penetration and grid scattering issues locally in different spatial directions.
2Object-affected harmful factors
If constant voltage differential is applied to counteract field penetration, then field isolation is improved, but electric fields along solid portion interfere with beam collimation
Solution Approach 1:
The patent creates a field-free region in the pulsing area by applying specific voltage differentials between the pusher electrode and intermediate electrode, while the grid electrode itself is configured with asymmetric wire spacing. The rectangular aperture configuration (reduced spacing perpendicular to grid, increased spacing parallel to grid) allows the grid to block field penetration without requiring constant voltage differential that would create interfering electric fields along the solid portion, thus resolving the contradiction between field isolation and beam collimation.
3Object-affected harmful factors
If second gridded electrode is added to reduce field penetration, then device complexity increases, but transmission efficiency may be reduced
Solution Approach 1:
Instead of adding a second complete gridded electrode, the patent segments the grid structure by creating rectangular apertures through asymmetric wire spacing in a single grid electrode. This segmentation approach divides the aperture into rectangular shapes with different dimensions in different directions, achieving field penetration reduction without the need for multiple complete grids, thus maintaining ion transmission efficiency while reducing device complexity compared to adding a full second gridded electrode.
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 configuration significantly reduces or eliminates artifact peaks and improves mass spectrometer performance by preventing stray ions from contributing to the mass spectra, while maintaining high transmission efficiency through the grid.
Implementation Method 1
obstruct stray ions at grazing incidence
Implementation Method 2
rectangular apertures that obstruct stray ions
Implementation Method 3
a pulsed acceleration field in the pulsing region, directed perpendicular to the primary beam axis, which, together with any subsequent electric fields, results in the acceleration of a segment of the primary ion beam
Implementation Method 4
These electrodes form one or more constant acceleration fields in order to optimize mass resolution and transmission of ions
Implementation Method 5
time-of-flight mass spectrometer
Data Source
AI summary
An orthogonal pulse accelerator for a Time-of-Flight mass analyzer includes an electrically-conductive first plate extending in a first plane, and a second plate spaced from the first plate. The second plate includes a grid that defines a plurality of apertures each having a first dimension extending in a first direction and a second dimension orthogonal to the first dimension, the first and second dimensions lying in the second plane and the second dimension begin larger than the first dimension. The first and second plates are positioned in the Time-of-Flight mass analyzer to receive, during operation of the mass analyzer, an ion beam propagating in the first direction in a region between the first and second plates, and the orthogonal pulse accelerator directs ions in the ion beam through the apertures.