RF Ion Guide Axial Field Generation via Auxiliary Electrodes
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Solution Overview
Problem
Existing RF ion guides face challenges in generating axial fields, particularly in rectilinear configurations, due to the difficulty in creating significant field penetration through the small gaps between flat plate electrodes, which limits their effectiveness in ion transport and trapping applications.
Innovation Solution
The use of elongated rod electrodes with RF voltages and auxiliary electrodes, where the auxiliary electrodes have different DC voltages and are arranged to create a DC auxiliary field that penetrates through openings in the RF electrodes, allowing for the generation of an axial potential gradient along the ion guide axis, even in configurations with small gaps between RF electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If small gaps between flat plate electrodes are used in rectilinear RF ion guides, then the device structure is compact, but the axial field penetration is insufficient
Solution Approach 1:
The patent transitions from flat plate electrodes to curved rod electrodes. The rod-shaped electrodes with cylindrical surfaces create more favorable field distribution and enable better axial field penetration through the gaps, resolving the contradiction between compact structure and sufficient field strength.
Solution Approach 2:
The patent changes the geometric parameters of the electrodes from flat plates to rods with specific dimensions (radius, length). This parameter change allows the electrodes to generate sufficient axial field penetration while maintaining a compact device structure, as the rod geometry naturally facilitates field concentration and penetration.
2Productivity
If auxiliary electrodes with DC voltages are added to generate axial fields, then ion transport efficiency is improved, but the device complexity increases
Solution Approach 1:
The RF electrodes serve dual functions: they provide the radiofrequency fields for ion confinement and, when configured as rods with appropriate geometry, they also generate the necessary axial fields for ion transport. This multi-functionality eliminates the need for separate auxiliary electrodes, improving ion transport efficiency while avoiding increased device complexity.
Solution Approach 2:
The patent merges the functions of RF confinement and axial field generation into a single electrode structure. The rod-shaped RF electrodes simultaneously provide both the radial confinement field and the axial transport field, simplifying the overall device architecture while maintaining high ion transport efficiency.
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 enables the effective generation of axial fields within RF ion guides, improving ion transport and trapping efficiency, particularly in high-pressure environments, and allows for more stable and flexible electrical arrangements, enhancing the performance of RF ion guides in mass spectrometry applications.
Implementation Method 1
auxiliary electrodes have different DC voltages and are arranged to create a DC auxiliary field that penetrates through openings in the RF electrodes, allowing for the generation of an axial potential gradient along the ion guide axis
Implementation Method 2
collisions primarily cause a reduction of ion kinetic energies, which is sometimes referred to 'collision cooling'
Implementation Method 3
collisions are energetic enough to cause collision induced dissociation (CID) of ions
Data Source
AI summary
RF ion guides are configured as an array of elongate electrodes arranged symmetrically about a central axis, to which RF voltages are applied. The RF electrodes include at least a portion of their length that is semi-transparent to electric fields. Auxiliary electrodes are then provided proximal to the RF electrodes distal to the ion guide axis, such that application of DC voltages to the auxiliary electrodes causes an auxiliary electric field to form between the auxiliary electrodes and the ion guide RF electrodes. A portion of this auxiliary electric field penetrates through the semi-transparent portions of the RF electrodes, such that the potentials within the ion guide are modified. The auxiliary electrode structures and voltages can be configured so that a potential gradient develops along the ion guide axis due to this field penetration, which provides an axial motive force for collision damped ions.