Ion Trap Mass Analyzer Non-Linear Axial Field
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Solution Overview
Problem
Current ion traps face limitations in efficiently ejecting ions with varying mass-to-charge ratios due to the linear axial electrostatic potential, which affects mass resolution and scanning efficiency during forward and reverse scans.
Innovation Solution
The ion trap design deviates from a quadratic axial electrostatic potential at its ends, creating a non-linear electric field that alters the resonance frequency of ions as their amplitude increases, allowing for improved mass selective ejection and resolution by optimizing the axial DC and AC potential profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a linear axial electrostatic potential is used in the ion trap, then the structure is simple and easy to manufacture, but the mass resolution and scanning efficiency deteriorate due to uniform ion ejection behavior
Solution Approach 1:
The patent applies local quality by making the axial electrostatic potential non-uniform along the ion trap axis. Specifically, the potential is designed to be quadratic (parabolic) in the central region for stable ion confinement, but deviates from quadratic at the ends to create non-linear electric fields. This spatial variation in potential quality allows different regions to serve different functions: the central region provides stable trapping while the end regions enable improved mass-selective ejection with sharper peaks, thus resolving the contradiction between manufacturing simplicity and mass resolution.
Solution Approach 2:
The patent changes the parameter of axial electrostatic potential from a uniform linear distribution to a non-linear distribution with quadratic central region and non-quadratic end regions. This parameter change creates position-dependent ion oscillation frequencies, where ions at different axial positions experience different restoring forces. As a result, ions are ejected at different rates during mass scanning, producing sharper peaks and improved mass resolution without significantly complicating the overall trap structure.
2Stability of the object's composition
If a quadratic axial electrostatic potential is maintained throughout the ion trap, then ion confinement is stable, but ion ejection efficiency and mass scanning performance worsen due to uniform oscillation frequencies
Solution Approach 1:
The patent implements local quality by dividing the axial electrostatic potential into distinct regions: a central quadratic region that provides stable ion confinement with uniform oscillation frequencies, and end regions where the potential deviates from quadratic to create non-linear electric fields. This spatial differentiation allows the central region to maintain stable ion trapping while the end regions enhance ion ejection efficiency by creating position-dependent oscillation frequencies, thus resolving the contradiction between confinement stability and ejection efficiency.
Solution Approach 2:
The patent applies segmentation by dividing the axial electrostatic potential profile into functionally distinct segments along the ion trap axis. The potential is segmented such that the central portion maintains a quadratic form for stable confinement, while the end portions are modified to deviate from quadratic. This segmentation allows each region to optimize its local function: stable trapping in the center and efficient ejection at the ends, thereby improving overall ion ejection efficiency without compromising confinement stability.
3Device complexity
If the axial electrostatic field is linear across the entire ion trap, then the device complexity is low, but the growth in ion oscillation amplitude is too rapid causing poor mass resolution
Solution Approach 1:
The patent applies local quality by creating a non-uniform axial electrostatic field where the central region has a linear field (quadratic potential) for stable ion confinement, while the end regions have non-linear fields (non-quadratic potential). This local differentiation controls the growth rate of ion oscillation amplitudes: the linear central field provides stable trapping, while the non-linear end fields slow down amplitude growth for ions near the trap ends, producing sharper ejection peaks and improved mass resolution without significantly increasing overall device 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 design enhances mass resolution and scanning efficiency by delaying or accelerating the growth in ion oscillation amplitude, depending on the scan direction, leading to sharper peaks and improved performance in both forward and reverse scans.
Implementation Method 1
AC or RF voltage means arranged and adapted to apply an AC or RF voltage to at least some of the plurality of electrodes in order to confine at least some ions radially within the ion guide or ion trap
Implementation Method 2
first means arranged and adapted to maintain a DC or electrostatic electric field across at least a portion of the axial length of the ion guide or ion trap in order to confine at least some ions axially within an axial ion trapping region
Implementation Method 3
second means arranged and adapted to apply a supplemental AC voltage or potential to the electrodes in a first mode of operation in order to resonantly or parametrically eject at least some ions from the ion guide or ion trap
Implementation Method 4
second means arranged and adapted to apply a supplemental AC voltage or potential to the electrodes in a first mode of operation in order to resonantly or parametrically eject at least some ions from the ion guide or ion trap
Data Source
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AI summary
An ion trap mass analyser 1 is disclosed comprising a segmented rod set. Ions are trapped radially within the mass analyser by a radial pseudo-potential well. The ions are also confined axially within the ion trap by an axial electric field. The axial electric field is substantially linear across the central section of the ion trap, but the electric field is distorted across both ends of the ion trap. A supplemental AC voltage or potential is applied to the electrodes comprising the ion trap mass analyser 1 in order to excite ions within the ion trap 1. The distortions in the electric field at the ends of the ion trap cause the resonant frequency of ions within the ion trap to shift to either a higher or lower frequency. If the frequency of the supplemental AC voltage or potential is scanned appropriately then ions are ejected from the ion trap in a shorter period of time leading to an improvement in mass resolution.