L-Shaped RF Ion Guide Geometry for Stronger Quadrupolar Confinement
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Solution Overview
Problem
RF multipole ion guides, particularly those using printed circuit board technology, suffer from weaker RF pseudo potentials leading to poorer transmission efficiencies and greater mass discrimination, especially in high-pressure regions and curved designs.
Innovation Solution
The design features four elongated electrodes with L-shaped cross-sections and RF voltages of equal amplitude but opposite phases applied to opposed pairs, along with a DC field gradient established by segmented DC electrodes, to enhance ion confinement and focusing, approximating a quadrupolar field for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If flatapole ion guide design is used, then fabrication cost is reduced and assembly is simplified, but RF pseudo potential strength is significantly weakened
Solution Approach 1:
The patent applies asymmetry by transitioning from the symmetric flat-inlaid electrode design to an L-shaped electrode configuration. The L-shaped geometry creates asymmetric field distribution that more closely approximates the ideal quadrupolar field, thereby strengthening the RF pseudo potential while maintaining compatibility with circuit board technology for cost-effective fabrication.
Solution Approach 2:
The patent changes the geometric parameters of the electrodes from flat rectangular shapes to L-shaped configurations. This parameter change fundamentally alters the electric field distribution within the ion guide, generating a stronger and more quadrupolar-like RF field that improves ion confinement and transmission efficiency while preserving the manufacturing advantages of printed circuit board technology.
2Ease of manufacture
If flatapole ion guide design is used, then assembly is simplified, but transmission efficiency is poorer
Solution Approach 1:
The L-shaped electrode design introduces asymmetry that better matches the theoretical quadrupolar field configuration. This asymmetric geometry creates more effective radial confinement of ions, leading to improved transmission efficiency through the ion guide while still utilizing simple circuit board fabrication and assembly methods.
Solution Approach 2:
By changing the electrode geometry parameter from flat rectangular to L-shaped, the patent optimizes the electric field distribution to enhance ion guidance. This parameter modification improves the matching between the actual field and the ideal quadrupolar field, thereby increasing transmission efficiency without complicating the manufacturing process.
3Ease of manufacture
If flatapole ion guide design is used, then fabrication is cheaper, but mass discrimination is greater
Solution Approach 1:
The L-shaped electrode configuration creates a more symmetric and quadrupolar-like electric field distribution compared to the flatapole design. This improved field symmetry reduces differential effects on ions of different masses, thereby minimizing mass discrimination while preserving the cost-effective circuit board fabrication approach.
Solution Approach 2:
The geometric parameter change to L-shaped electrodes optimizes the electric field uniformity and quadrupolar character, which reduces mass-dependent variations in ion transmission. This parameter optimization decreases mass discrimination effects while maintaining the economical fabrication process inherent to printed circuit board technology.
4Strength
If traditional round-rod design is used, then RF pseudo potential is stronger, but fabrication cost increases and assembly becomes more difficult
Solution Approach 1:
The patent creates a simplified copy or approximation of the ideal round-rod quadrupole design by using L-shaped electrodes on circuit boards. This copying approach captures the essential quadrupolar field characteristics needed for strong RF pseudo potential generation while using simpler, more manufacturable flat electrode geometries that can be produced using standard printed circuit board processes.
Solution Approach 2:
The patent changes the physical form parameter of the electrodes from three-dimensional round rods to two-dimensional L-shaped planar structures. This parameter change maintains the functional equivalence of generating strong quadrupolar RF fields while dramatically simplifying fabrication and assembly through circuit board technology, reducing both cost and manufacturing 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 enhances transmission efficiencies, reduces mass discrimination, and maintains compatibility with circuit board technology, particularly in high-pressure regions, by strengthening the RF field and maintaining effective ion transport across a wide mass range.
Implementation Method 1
RF voltages of equal amplitude but opposite phases are applied to opposed pairs of electrodes, in the manner known in the art, to generate an RF field to radially confine ions and focus them to the centerline
Implementation Method 2
A set of longitudinally segmented DC electrodes may be arranged in parallel to the elongated electrodes and coupled to a DC voltage source for establishing a DC field gradient within the ion guide interior that urges ions along the direction of travel
Implementation Method 3
Because the resultant RF field more closely approximates a quadrupolar field, relative to the field generated within a flatapole, better performance may be achieved in terms of improved transmission efficiencies and/or less mass discrimination
Data Source
AI summary
An embodiment of the present invention provides an RF ion guide having four elongated electrodes arranged in parallel around the axial centerline. Each electrode is generally L-shaped in cross section, having first and second inner surfaces directed toward the interior of the ion guide. The first and second surfaces extend along axis that are transverse and preferably approximately perpendicular to one another. RF voltages of equal amplitude but opposite phases are applied to opposed pairs of electrodes, in the manner known in the art, to generate an RF field to radially confine ions and focus them to the centerline. Because the resultant RF field more closely approximates a quadrupolar field, relative to the field generated within a flatapole, better performance may be achieved in terms of improved transmission efficiencies and/or less mass discrimination.