Ion Funnel Aperture Geometry for Stable Ion Transmission
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Solution Overview
Problem
Ion funnels face inefficiencies in transmitting low-mass ions due to poor stability and limitations in transmitting a wide m/z range, primarily due to space charge effects, gas flow drag, and axial RF voltage instability, which leads to ion fragmentation and narrow optimal transmission ranges.
Innovation Solution
The design incorporates an ion transfer tube with a slotted or multiple round bores and an ion funnel with enlarged apertures, eliminating the need for a DC electrical potential gradient, reducing on-axis RF voltage penetration, and achieving subsonic gas flow for improved ion transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a DC electrical potential gradient is applied to promote ion transport through the critical region near the output, then ion transmission efficiency is improved, but device complexity and potential instability increase
Solution Approach 1:
The patent removes the DC electrical potential gradient component from the ion funnel system, relying solely on RF voltages applied to the ring electrodes to achieve ion transmission. This extraction of the DC gradient simplifies the electrical configuration while maintaining ion transport through optimized RF parameters and aperture geometry.
2Object-affected harmful factors
If the exit aperture size is increased to reduce on-axis RF voltage, then RF voltage penetration is reduced, but gas load on downstream vacuum chambers increases
Solution Approach 1:
The patent changes the aperture diameter parameter to be at least three times the inter-electrode pitch, which fundamentally alters the RF voltage distribution within the funnel. This parameter change reduces on-axis RF voltage penetration without requiring a DC gradient, while the specific aperture-to-pitch ratio maintains gas flow characteristics that limit downstream gas load.
3Productivity
If a high throughput ion inlet capillary with large internal bore is used, then ion transmission capacity is improved, but foreline pressure increases promoting transient trapping
Solution Approach 1:
The patent modifies the aperture dimensions and inter-electrode pitch parameters to create an optimized ratio relationship. This parameter optimization allows the system to handle high ion throughput through the enlarged apertures while maintaining stable ion transport by reducing transient trapping effects, eliminating the need for DC gradient assistance.
4Productivity
If aperture diameters are enlarged to at least three times the inter-electrode pitch, then ion transmission efficiency is improved, but device dimensions increase
Solution Approach 1:
The patent establishes a specific parameter relationship where aperture diameter is at least three times the inter-electrode pitch. This parameter change optimizes the balance between transmission efficiency and physical dimensions, allowing enlarged apertures that improve ion transmission while the proportional relationship to pitch maintains a compact overall device footprint.
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 enhances ion transmission efficiency, broadens the operational voltage range, reduces fragmentation, and improves sensitivity for both low and high m/z ions, particularly in complex mixtures, by maintaining ion stability and reducing gas load on downstream vacuum chambers.
Implementation Method 1
radio-frequency (RF) voltages are applied to the electrodes in a prescribed phase relationship to radially confine the ions to the interior of the device
Implementation Method 2
each aperture diameter is greater than or equal to three times the inter-electrode pitch... reducing on-axis RF voltage penetration
Data Source
AI summary
An ion transport system comprises: (I) an ion transfer tube extending between an atmospheric-pressure ionization chamber and a partially evacuated chamber; and (II) an ion funnel within the chamber comprising: (1) an exit electrode that has an exit aperture configured to deliver the gas and charged particles to a high-vacuum chamber; and (2) a funnel portion comprising a plurality of plate electrodes configured as a stack, each electrode comprising a respective aperture, wherein an aperture diameter of each of the plurality of electrodes is greater than or equal to three times an inter-electrode pitch and wherein no DC electrical potential gradient is applied between the exit electrode and an adjacent one of the plurality of plate electrodes.