Linear Ion Trap Electrodes with Isosceles Triangle Cross-Sections
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Solution Overview
Problem
Existing linear ion traps face challenges in maintaining high resolving power due to field reduction near ejection slits, particularly in miniaturized designs with flat or hyperbolic electrodes, leading to reduced mass analysis efficiency.
Innovation Solution
The use of electrodes with a cross-sectional shape of isosceles triangles, where flat parts are angled relative to each other, compensates for field reduction at the ejection slit, allowing for high resolving power while simplifying manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If hyperbolic electrodes are used to create quadrupole fields, then resolving power is improved, but manufacturing complexity and cost increase significantly
Solution Approach 1:
The patent replaces expensive, difficult-to-manufacture hyperbolic electrodes with simple flat plate electrodes that are easier to manufacture. While flat plates inherently create non-ideal fields, the invention uses multiple strips per electrode to approximate the quadrupole field shape, achieving good resolving power with much simpler, cheaper components that can be manufactured using standard printed circuit board technology
Solution Approach 2:
The patent divides each flat electrode into multiple longitudinal strips (e.g., 3-5 strips per electrode). By applying RF potentials to these strips in specific proportions, the combined field approximates a quadrupole field more closely than a single flat electrode could achieve. This segmentation allows simple flat plates to achieve the field characteristics of complex hyperbolic electrodes
2Ease of manufacture
If flat plate electrodes are used to simplify manufacturing, then ease of manufacture is improved, but field shape degradation occurs leading to reduced resolving power
Solution Approach 1:
Each flat electrode is divided into multiple longitudinal strips that can be independently potential-controlled. By applying RF potentials to these strips in specific proportions (e.g., alternating phases), the combined electric field from all electrodes approximates a quadrupole field, significantly improving field shape and resolving power compared to using simple flat plates without segmentation
Solution Approach 2:
Different regions of the electrode surface (different strips) are assigned different potentials to create the desired field distribution. The strips closer to the center may have different potential proportions than outer strips, allowing local optimization of the field shape to approximate quadrupole characteristics across the entire trap volume
3Productivity
If ejection slits are made wider to improve ion ejection efficiency, then productivity is improved, but field reduction near slits increases leading to lower resolving power
Solution Approach 1:
The strips adjacent to ejection slits are assigned different RF potential proportions compared to central strips. This local optimization compensates for the field reduction effect near slits, allowing wider slits to be used without significantly degrading resolving power. The modified potential distribution maintains adequate field strength in the slit regions while preserving overall quadrupole field characteristics
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 design achieves resolving power comparable to hyperbolic geometry ion traps with significantly simpler electrode manufacturing, maintaining high performance across varying trap sizes.
Implementation Method 1
Only quadrupole fields have such property. In order to create quadrupole fields electrodes of the trap should have hyperbolic shape
Implementation Method 2
Trapping field in such traps is created by application of radiofrequency potentials RF+ and RF-
Implementation Method 3
Methods of ion manipulations in ion traps are based on resonance excitation of ion vibrations. Falling into resonance with excitation field ions increases amplitude of their vibration
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
Invention relates to the field of mass spectrometry, in particular it relates to design of a linear ion trap and its electrode system which forms a trapping field. Claimed electrode system of a linear ion trap has four electrodes, each pair oppositely located. Plains of symmetry of electrode pairs are perpendicular to each other. Difference from prototype is that each electrode of at least one pair has in a cross section substantially a shape of isosceles triangle. Top of the triangle is directed towards longitudinal axis of the trap. The best result is achieved when angle between shoulders of the triangle is from 130° to 152°. In other words, angle between working surfaces of electrodes is 130- 152°. The width of slit for ejecting ions in such electrode is less than 24% of the inscribed radius of the trap. Suggested electrode system for a linear ion trap allows achieving high resolving power which is comparable with resolution of ion traps of hyperbolic geometry, i.e. significantly higher than can be achieved by prototype ion traps. At the same time the working surface of electrodes in proposed system is composed of flat surfaces, which are placed at certain angle to each other, with top of angle directed towards ion trap axis. Manufacturing of such electrodes is much simpler. Angle in the region of ejection slit compensates for local reduction of the field strength.