Vacuum DMS Ion Guide Tapered Electrode Design
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Solution Overview
Problem
Existing systems lack an efficient means to integrate differential mobility spectrometry (DMS) devices into vacuum systems of mass spectrometers without degrading ion transmission through the entrance optics.
Innovation Solution
A system comprising a vacuum chamber with first and second ion guides and a DMS device, where the ion guides are tapered to focus ions and the DMS device is housed to operate at higher pressures than the ion guides, minimizing ion loss and optimizing ion transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the DMS device is placed in the vacuum system of a mass spectrometer, then the device can be permanently mounted with on/off control, but ion transmission through the entrance optics may be degraded
Solution Approach 1:
The system is divided into distinct pressure zones: a vacuum chamber for the mass spectrometer and a housing for the DMS device that can be differentially pumped. This segmentation allows the DMS device to operate at higher pressure while the mass spectrometer maintains vacuum, enabling permanent mounting without compromising ion transmission to the entrance optics.
Solution Approach 2:
A differential pumping system acts as an intermediary between the vacuum chamber and the DMS device housing. This intermediary maintains the pressure gradient, allowing the DMS device to be permanently mounted in the vacuum system while preventing pressure equalization that would degrade ion transmission through the entrance optics.
2Loss of substance
If the inscribed diameter at the DMS inlet end is made larger than the inscribed diameter at the first exit end of the first ion guide, then ion loss from the first ion guide to the DMS device is minimized, but the device complexity increases
Solution Approach 1:
The ion guides feature tapered electrodes that gradually change the inscribed diameter along the ion path. This dynamic geometric transition smoothly adapts the ion beam from the smaller ion guide exit to the larger DMS inlet, minimizing ion loss through gentle focusing rather than abrupt transitions that would increase complexity.
3Loss of substance
If the inscribed diameter at the second inlet end is made larger than the inscribed diameter at the DMS exit end, then ion loss from the DMS device to the second ion guide is minimized, but the device complexity increases
Solution Approach 1:
The second ion guide employs tapered electrodes that dynamically adjust the inscribed diameter to match the transition from the DMS exit to the ion guide inlet. This gradual geometric adaptation minimizes ion loss while maintaining a manageable device complexity through systematic tapering rather than complex mechanical adjustments.
4Productivity
If the housing allows the DMS device to operate at pressure greater than the vacuum chamber, then ion capture efficiency is improved, but the pressure gradient requires additional pumping infrastructure
Solution Approach 1:
The system segments the vacuum environment into distinct pressure zones separated by differential pumping stages. The housing containing the DMS device is differentially pumped to maintain higher pressure than the main vacuum chamber, improving ion capture efficiency while isolating the pumping infrastructure requirements to specific zones rather than requiring system-wide complexity.
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 allows for efficient ion capture and separation within the DMS device, maintaining high ion transmission efficiency and enabling permanent mounting of the DMS device in the mass spectrometer.
Implementation Method 1
The first ion guide has a plurality of first electrodes arranged around a central axis defining a first ion channel. Each of the plurality of first electrodes is tapered to provide a larger inscribed diameter at the first inlet end than at the first exit end in order to focus ions in the first ion channel.
Implementation Method 2
The DMS device has a plurality of DMS electrodes arranged around a central axis defining a DMS ion channel with a constant gap in order to separate ions within the DMS ion channel
Implementation Method 3
The second ion guide has a plurality of second electrodes arranged around a central axis defining a second ion channel. Each of the plurality of second electrodes is tapered to provide a larger inscribed diameter at the second inlet end than at the second exit end in order to focus ions in the second ion channel.
Data Source
AI summary
Differential mobility spectrometry is performed under vacuum. Ions generated in a high pressure region are received from the inlet orifice of a vacuum chamber using a first ion guide located in the vacuum chamber. The first ion guide focuses the generated ions on a DMS device inlet end using a plurality of tapered electrodes. The DMS device is coaxial and adjacent to the first ion guide. The DMS device separates the focused ions using a plurality of electrodes. The inscribed diameter at the DMS device inlet end is larger than the inscribed diameter at the first ion guide exit end to maximize ion transfer. The separated ions are received from the DMS device using a second ion guide coaxial and adjacent to the DMS device. The second ion guide focuses the separated ions on an exit orifice of the vacuum chamber using a plurality of tapered electrodes.