Ion Mobility Spectrometer Virtual Aperture Grid
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Solution Overview
Problem
Conventional ion mobility spectrometers require a physical aperture grid to prevent premature ion detector response, which increases system complexity and introduces noise due to vibration sensitivity and additional current generation.
Innovation Solution
An ion mobility spectrometer with a virtual aperture grid, where stacked electrodes adjacent to the ion collector are connected to a source of free charge, creating a low-pass electrical circuit that shields the ion collector from mirror current, eliminating the need for a physical aperture grid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a physical aperture grid is used to prevent premature ion detector response, then the ion collector is shielded from mirror current, but the system complexity increases and noise is introduced due to vibration sensitivity and additional current generation
Solution Approach 1:
The patent removes the physical aperture grid from the system entirely. Instead of using a physical structure to shield the ion collector, the invention extracts this function and replaces it with a computational algorithm that processes detector signals to eliminate mirror current effects, thereby reducing system complexity while maintaining shielding effectiveness
Solution Approach 2:
The patent replaces the mechanical/physical aperture grid with an electronic/computational solution. The physical shielding structure is substituted by signal processing algorithms that mathematically remove mirror current contributions from the detector signal, eliminating vibration sensitivity and mechanical complexity
2Reliability
If a physical aperture grid is used to prevent premature ion detector response, then the ion collector is shielded from mirror current, but noise is introduced due to vibration sensitivity and additional current generation
Solution Approach 1:
The patent replaces the physical aperture grid with an electronic signal processing approach. By using algorithms to computationally remove mirror current effects from the detector signal, the system eliminates the mechanical structure that causes vibration sensitivity and associated noise, while maintaining effective shielding
Solution Approach 2:
The patent introduces signal processing algorithms as an intermediary between the ion collector and the final signal output. This computational mediator processes the raw detector signals to eliminate mirror current contributions before presenting the cleaned signal, thereby achieving shielding without the noise-generating physical grid
3Device complexity
If stacked electrodes with small pitch are used to create a virtual aperture grid, then the physical aperture grid is eliminated, but the electrode structure becomes more complex
Solution Approach 1:
The patent makes the stacked electrodes serve multiple functions: they provide the electric field for ion mobility separation and simultaneously create the virtual aperture grid effect for shielding. This multi-functionality eliminates the need for separate physical aperture grid structures, reducing overall system complexity while maintaining manufacturing simplicity
Solution Approach 2:
The patent merges the function of the stacked electrodes with the aperture grid function. By combining these two previously separate components into a single integrated structure, the invention reduces the number of parts and simplifies manufacturing while achieving both ion mobility separation and mirror current shielding
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 reduces system complexity and noise while maintaining resolution by effectively screening the mirror current, resulting in a more stable and accurate ion mobility spectrum without the added complexity of a physical aperture grid.
Implementation Method 1
at least two of the stacked electrodes adjacent to the ion collector have an electrode pitch that is less than the width of an ion swarm and each of the adjacent electrodes is connected to a source of free charge, thereby providing a virtual aperture grid at the end of the drift region that shields the ion collector from the mirror current of the ion swarm
Implementation Method 2
a drift tube comprising a drift region in which the ions drift under the influence of an electric field, established by a plurality of stacked electrodes, against a counter-flowing drift gas and are separated into at least one single ion swarm therein
Data Source
AI summary
An ion mobility spectrometer does not require a physical aperture grid to prevent premature ion detector response. The last electrodes adjacent to the ion collector (typically the last four or five) have an electrode pitch that is less than the width of the ion swarm and each of the adjacent electrodes is connected to a source of free charge, thereby providing a virtual aperture grid at the end of the drift region that shields the ion collector from the mirror current of the approaching ion swarm. The virtual aperture grid is less complex in assembly and function and is less sensitive to vibrations than the physical aperture grid.