Variable-Multipole Ion Guide for Ion Acceptance and Beam Focusing
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Solution Overview
Problem
Current ion guides, particularly in collision cells of mass spectrometry systems, face challenges in efficiently capturing and transferring ions with varying mass-to-charge ratios due to limitations in their RF electric field configurations, which affect ion beam focusing and fragmentation efficiency.
Innovation Solution
The ion guide is designed with a configuration of elongated electrodes forming a two-dimensional RF electric field, comprising a superposition of lower-order and higher-order multipole components, where the amplitude ratio of these components varies along the axis, and the RF voltage amplitude also changes, to create a pseudo-potential well that adapts to ion beam characteristics, enhancing ion confinement and transfer efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional linear multipole ion guide with constant RF voltage amplitude is used, then the ion guide structure is simple and easy to manufacture, but the ion acceptance at the entrance is limited and the ion beam focusing is insufficient
Solution Approach 1:
The patent applies dynamics by making the RF voltage amplitude variable along the ion guide axis rather than constant. The RF voltage amplitude increases from the ion source end toward the analyzer end, creating a dynamic field configuration that adapts to the changing ion beam characteristics and improves ion acceptance while maintaining manageable device complexity
Solution Approach 2:
The patent changes the RF voltage amplitude parameter along the ion guide axis. By varying this parameter spatially, the system achieves improved ion confinement and acceptance without requiring fundamental changes to the electrode structure, thus balancing performance improvement with device complexity
2Manufacturing precision
If the RF voltage amplitude is increased to improve ion beam focusing, then the ion confinement is enhanced, but the ion fragmentation increases due to higher energy collisions
Solution Approach 1:
The patent applies local quality by creating different RF voltage amplitude conditions at different locations along the ion guide. The voltage amplitude is lower near the ion source where fragmentation should be minimized, and higher near the analyzer where strong focusing is needed, thus achieving localized optimization of both focusing and fragmentation control
Solution Approach 2:
The dynamic variation of RF voltage amplitude along the axis allows the system to provide appropriate confinement strength at each location. This dynamic approach prevents excessive energy transfer that would cause fragmentation while still achieving the necessary beam focusing for mass analysis
3Manufacturing precision
If the ion guide uses a constant aspect ratio configuration, then the electrode structure is uniform and easy to manufacture, but the ion beam emittance cannot be minimized effectively at the exit
Solution Approach 1:
The patent makes the aspect ratio variable along the ion guide axis, transitioning from a constant cross-section to a tapered configuration. This dynamic geometric change allows effective emittance minimization at the exit while maintaining manufacturability through systematic tapering rather than complex variable geometry
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 improves ion beam focusing and fragmentation by allowing a larger ion acceptance at the entrance while minimizing emittance at the exit, optimizing the transfer of ions through narrow apertures and maintaining adiabatic conditions, thus enhancing the overall performance of mass spectrometry systems.
Implementation Method 1
the plurality of electrodes is configured to generate a two-dimensional RF electric field on the transverse plane orthogonal to the axis in the ion guide interior
Implementation Method 2
the RF electric field comprising a superposition of a lower-order multipole component and a higher-order multipole component wherein an amplitude ratio of the lower-order component to the higher-order component varies along the ion guide axis
Implementation Method 3
to create a pseudo-potential well that adapts to ion beam characteristics, enhancing ion confinement and transfer efficiency
Implementation Method 4
the ion guide is configured to generate a radio frequency (RF) field in its interior space effective to focus ions as an ion beam on the central, longitudinal axis of the ion guide
Data Source
AI summary
An ion guide includes electrodes elongated along an axis from an entrance end to an exit end and spaced around the axis to surround an interior. The electrodes have polygonal shapes with inside surfaces disposed at a radius from the axis and having an electrode width tangential to a circle inscribed by the electrodes. An aspect ratio of the electrode width to the radius varies along the axis. The electrodes are configured to generate a two-dimensional RF electrical field in the interior having a multipole composition comprising one or more lower-order multipole components and one or more higher-order multipole components and varying along the axis in accordance with the varying aspect ratio, and having an RF voltage amplitude that varies along the axis.