Microfabricated Quadrupole Lens Segmentation for Mass Resolution
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Solution Overview
Problem
Miniature mass spectrometers face limitations in mass range, sensitivity, and noise levels due to RF heating and capacitative coupling issues in silicon-based electrostatic quadrupole mass filters, which restrict the voltage and frequency that can be applied, limiting both mass range and resolution.
Innovation Solution
The solution involves a microfabricated electrostatic quadrupole mass filter with electrodes mounted on insulating substrates, using conducting parts for alignment and support, and incorporating a Brubaker pre-filter to reduce fringing fields and capacitative coupling, while a conducting screen provides complete shielding to enhance sensitivity and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If silicon-based electrostatic quadrupole mass filters are used, then miniaturisation and cost reduction are achieved, but RF heating and capacitative coupling limit the voltage and frequency that can be applied, restricting mass range and resolution
Solution Approach 1:
The quadrupole electrodes are segmented into multiple sections along their length, with each section independently controllable. This segmentation reduces capacitative coupling between adjacent electrodes by introducing insulating barriers between segments, thereby reducing RF heating while maintaining the miniaturized structure and improving mass range and resolution
Solution Approach 2:
Insulating coatings or dielectric layers are introduced as intermediary materials between the silicon substrate and the quadrupole electrodes, or between adjacent electrode sections. These intermediaries reduce direct capacitative coupling and RF heating effects, enabling higher operating voltages and frequencies in the miniaturized device
2Volume of moving object
If the entrance pupil size is decreased, then device miniaturisation is achieved, but ion transmission is reduced
Solution Approach 1:
A Brubaker pre-filter is introduced upstream of the main quadrupole filter to pre-collimate and guide ions into the entrance pupil. This preliminary action improves ion transmission efficiency by reducing angular dispersion before ions enter the miniaturized quadrupole, compensating for the reduced pupil size while maintaining compact dimensions
3Productivity
If fringing fields at the input to the quadrupole are reduced, then ion transmission is improved, but additional components are required
Solution Approach 1:
The Brubaker pre-filter and main quadrupole filter are merged into a single integrated structure where the pre-filter electrodes are electrically connected to the main quadrupole electrodes. This merging reduces the number of separate components while maintaining improved ion transmission by reducing fringing fields at the input
4Reliability
If higher voltages and frequencies are applied, then mass range and resolution are improved, but RF heating increases
Solution Approach 1:
Segmenting the electrodes into multiple sections with insulating barriers between segments reduces capacitative coupling, thereby reducing RF heating and allowing higher operating voltages and frequencies to be applied, improving mass range and resolution
Solution Approach 2:
The operating parameters (voltage and frequency) are optimized by changing the segmentation configuration and insulating barrier properties, allowing the system to operate at higher voltages and frequencies with reduced RF heating through modified electrical parameters
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 approach allows for higher mass range, reduced noise, and improved sensitivity by minimizing RF heating and capacitative coupling, enabling the application of higher voltages and frequencies, thus enhancing the overall performance of the mass spectrometer.
Implementation Method 1
travel parallel to the electrodes under the influence of a time-varying hyperbolic electrostatic field. This field contains both a direct current (DC) and an alternating current (AC) component
Implementation Method 2
quadrupole electrostatic lens as a mass filter
Implementation Method 3
RF heating, caused by capacitative coupling between co-planar cylindrical electrodes through the oxide interlayer via the substrate
Data Source
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AI summary
This invention provides a method of aligning sets of cylindrical electrodes in the geometry of a miniature quadrupole electrostatic lens, which can act as a mass filter in a quadrupole mass spectrometer. The electrodes are mounted in pairs on microfabricated supports, which are formed from conducting parts on an insulating substrate. Complete segmentation of the conducting parts provides low capacitative coupling between co-planar cylindrical electrodes, and allows incorporation of a Brubaker prefilter to improve sensitivity at a given mass resolution. A complete quadrupole is constructed from two such supports, which are spaced apart by further conducting spacers. The spacers are continued around the electrodes to provide a conducting screen.