Compensation Electrodes for Linear Ion Trap Field Optimization
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Solution Overview
Problem
Ion processing devices with linear or two-dimensional electrode arrangements face challenges due to field imperfections caused by electrode truncation and slots, leading to shifts in ion ejection time and mass shifts in mass spectra, which are not adequately addressed by conventional methods.
Innovation Solution
The introduction of a compensation electrode structure that adjusts the RF field by applying different voltages to main and compensation electrodes, optimizing field conditions for ion ejection and collision-induced dissociation (CID) processes, and allowing for the superposition of adjustable multipole components on the quadrupole trapping field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional electrode arrangements are used, then device structure is simple, but field imperfections cause mass shifts and reduced measurement precision
Solution Approach 1:
The electrode structure is segmented into main electrodes and compensation electrodes. The compensation electrodes are positioned to specifically address field imperfections in certain regions while the main electrodes provide the primary trapping field, allowing independent optimization of different functional zones
Solution Approach 2:
Different regions of the electrode structure are assigned different functional qualities. The compensation electrodes are strategically positioned to correct local field imperfections near the aperture, while the main electrodes provide the overall quadrupole field, creating non-uniform but optimized field distribution
2Adaptability or versatility
If fixed field conditions are maintained, then operational stability is high, but adaptability to different modes of operation is reduced
Solution Approach 1:
The system transitions from static field conditions to dynamic, adjustable field conditions. The compensation electrode voltages can be independently adjusted to optimize field conditions for different operational modes such as ion ejection, CID, and mass analysis, allowing the same device to adapt to multiple functions
Solution Approach 2:
The electrical parameters (voltages) of the compensation electrodes are made variable to change the field conditions. By adjusting the voltage on compensation electrodes relative to main electrodes, the system can optimize for different modes of operation while maintaining overall field stability through coordinated control
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 effectively compensates for field imperfections, improving ion ejection efficiency, mass resolution, and increasing the average collision energy for CID processes, thereby enhancing the overall performance of ion processing devices.
Implementation Method 1
A first RF voltage is applied to at least two of the main electrodes at a first amplitude. A second RF voltage is applied to a compensation electrode at a second amplitude.
Implementation Method 2
The radial excursions of ions along the x-y plane may be controlled by applying a two-dimensional RF trapping field between opposing pairs of electrodes. The axial excursions of ions, or the motion of ions along the central axis, may be controlled by applying an axial DC trapping field between the axial ends of the electrodes.
Implementation Method 3
Ions present in the interior space of the electrode set are responsive to, and their motions influenced by, all electric fields active within the interior space.
Data Source
AI summary
Methods for applying an RF field in a two-dimensional electrode structure include applying RF voltages to one or more main electrodes and compensation electrodes. The voltages on the one or more compensation electrodes may be adjusted to be proportional to the voltages on the main electrodes. The adjustment(s) may be done to optimize the RF field for different modes of operation such as ion ejection and ion dissociation. For dissociation and other procedures involving ion excitation, the voltages applied to the one or more compensation electrodes may be different from the voltages applied to the one or more main electrodes. Electrode structures may include main trapping electrodes, one or more compensation electrodes, one or more ion exit apertures, and a device or circuitry for applying the various desired voltages.