Multi-Stage Ion Guide with Constant Rod Ratio
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Solution Overview
Problem
Conventional ion guides face challenges in efficiently concentrating ion beams due to geometrical distortions and pressure-related issues, leading to reduced sensitivity and effectiveness in mass spectrometry, particularly when ions transition from high to low pressure regions.
Innovation Solution
The ion guide features multiple stages with elongate conductive rod segments arranged about a guide axis, where the ratio of rod radius to the distance from the axis is constant, allowing for a well-defined electric field that progressively reduces the ion beam radius, and varying voltage amplitudes and frequencies across stages to guide and confine ions effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ion guides are used to transport ions from high pressure to low pressure regions, then ion transmission is achieved, but geometrical distortions and pressure-related issues cause beam concentration problems and reduced sensitivity
Solution Approach 1:
The ion guide is divided into multiple stages, each with progressively smaller rod radii. This segmentation allows the beam to be gradually concentrated as it progresses through each stage, preventing geometrical distortions that would occur in a single-stage design while maintaining reliable ion transmission from high to low pressure regions.
Solution Approach 2:
Each stage of the ion guide has locally optimized rod dimensions where the radius decreases progressively from one stage to the next. This local quality variation ensures that the electric field geometry is optimized at each position along the beam path, achieving precise beam concentration without the distortions that plague conventional uniform designs.
2Measurement precision
If the ion beam radius is reduced to concentrate ions, then sensitivity is improved, but ion losses increase due to collisions with rod electrodes
Solution Approach 1:
The ion guide employs dynamic control of RF voltage amplitude and frequency across different stages. By adjusting these parameters progressively, the electric field dynamically adapts to guide ions through each stage with optimal confinement, achieving beam concentration while minimizing ion losses through careful parameter optimization at each position.
Solution Approach 2:
The system changes key operating parameters (RF voltage amplitude, frequency, and rod radius) progressively from one stage to the next. This parameter optimization ensures that ions are concentrated effectively at each stage while maintaining field conditions that prevent excessive ion losses, resolving the contradiction between concentration and loss.
3Stress or pressure
If multiple pumping stages are used to reduce pressure in the analyser region, then cost-effective pressure reduction is achieved, but the complexity of the system increases
Solution Approach 1:
The ion guide serves multiple functions: it transports ions through pressure regions, concentrates the ion beam, and provides RF ion guiding all in a single integrated structure. This multi-functionality reduces the need for separate pumping stages and components, achieving pressure reduction without proportionally increasing system complexity.
4Quantity of substance
If large entrance apertures are used to increase ion flux, then sensitivity is improved, but the ability to concentrate the beam at the exit is reduced
Solution Approach 1:
The multi-stage design with progressively smaller rod radii allows the system to accept a large ion flux through the entrance while gradually concentrating the beam through each subsequent stage. The segmentation enables the transition from large aperture acceptance to small exit beam diameter without losing either ion flux or concentration precision.
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 the sensitivity of mass spectrometers by maintaining a well-defined electric field and reducing ion losses, allowing for higher ion flux and improved sensitivity, especially during transitions between pressure regions.
Implementation Method 1
A voltage source provides a voltage having an AC component between two adjacent ones of the plurality of opposing elongate conductive rod segments of each of the stages to produce an alternating electric field to guide ions along the guide axis
Implementation Method 2
Within each stage, amplitude and frequency, and resolving potential of the electric field may be independently varied... allowing for a well-defined electric field that progressively reduces the ion beam radius
Data Source
AI summary
An ion guide includes multiple stages. An electric field within each stage guides ions along a guide axis. Within each stage, amplitude and frequency, and resolving potential of the electric field may be independently varied. The geometry of the rods maintains a similarly shaped field from stage to stage, allowing efficient guidance of the ions along the axis. In particular, each rod segment of the ith of stage has a cross sectional radius ri, and a central axis located a distance Ri+ri from the guide axis. The ratio ri/Ri and is substantially constant along the guide axis, thereby preserving the shape of the field.