Ion Guide With DC Beam Deflection for Neutral Separation
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Solution Overview
Problem
Ion fragmentation and contamination issues in ion spectrometers due to the use of ion funnels with RF electrodes, where neutrals and droplets can strike electrodes, causing charging effects and ion beam misdirection, and existing solutions either increase fragmentation risk or require complex electrode structures.
Innovation Solution
An ion guide design featuring a first electrode assembly with guide electrodes receiving RF voltages to create a confinement volume and a second electrode assembly receiving DC voltages to deflect the ion beam radially, separating ions from neutrals and reducing fragmentation risk by maintaining a stable RF pseudopotential and axial DC gradient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ion funnels with RF electrodes are used to guide ions, then ion beam transmission is improved, but neutrals and droplets strike the electrodes causing contamination and charging effects
Solution Approach 1:
The patent extracts the harmful neutral particles and droplets from the ion beam by applying a DC electric field that deflects ions while allowing neutrals to pass through undeflected. This separates the ion guidance function from the neutral particle removal function, solving the contamination problem while maintaining transmission efficiency
Solution Approach 2:
The electrode system is segmented into RF electrodes for ion confinement and a separate DC electrode for neutral particle removal and ion deflection. This functional segmentation allows each electrode type to optimize its specific role without interfering with the other, reducing contamination while maintaining transmission
2Manufacturing precision
If the radius of RF electrode rings is reduced to focus the ion beam, then ion beam focusing is improved, but ion fragmentation occurs due to RF field penetration
Solution Approach 1:
A DC electrode is introduced as an intermediary element between the RF electrodes and the ion beam. This DC electrode creates an electric field that assists in ion focusing and deflection while the RF electrodes maintain a larger radius to avoid fragmentation. The DC field mediates the focusing function without requiring aggressive RF field penetration
Solution Approach 2:
The patent changes the operational parameters by applying DC voltages to specific electrodes in addition to the RF voltages. This parameter change allows the system to achieve ion focusing and deflection through combined DC and RF fields, eliminating the need to reduce RF electrode radius and thereby preventing ion fragmentation
3Manufacturing precision
If increasing separation between RF electrodes is used to create narrowing pseudopotential, then ion beam focusing is improved, but ion fragmentation increases due to RF barrier penetration
Solution Approach 1:
The focusing function is segmented between DC electrodes and RF electrodes. DC electrodes with increasing separation create the primary focusing gradient, while RF electrodes maintain constant separation to provide stable confinement without excessive field penetration, thus achieving focusing while preventing fragmentation
Solution Approach 2:
The patent uses a composite electrode system combining DC and RF voltage applications. The DC component provides the focusing gradient through variable separation electrodes, while the RF component provides stable confinement. This composite approach achieves focusing without the harmful effects of excessive RF field penetration
4Reliability
If density of electrode rings is increased to mitigate ion fragmentation, then ion beam stability is improved, but device complexity increases
Solution Approach 1:
The patent extracts the stability function from the RF electrode density and assigns it to a separate DC electrode system. This allows the RF electrodes to maintain lower density while the DC electrodes provide the additional stabilization needed, reducing overall device complexity while maintaining ion beam stability
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
Improves ion beam focusing and separation from neutrals, enhancing transmission through the ion exit aperture while minimizing ion fragmentation and contamination, allowing mainly ions to pass through, thus improving the efficiency and accuracy of ion spectrometers.
Implementation Method 1
An ion guide typically has a series of stacked radio frequency (RF) ring electrodes, which generate a repulsive RF pseudopotential inside the funnel
Implementation Method 2
the second electrode assembly is positioned with respect to the first electrode assembly and is configured to receive a DC voltage, such that a centre of the ion beam is deflected to be off the central axis
Implementation Method 3
If the ion beam enters the ion guide as part of a jet comprising neutrals or droplets, the neutrals will be undeflected and will continue along their original trajectory. Deflecting the ion beam allows the ions to be separated from the neutrals
Data Source
AI summary
An ion guide is provided for a spectrometer. The ion guide comprises a first electrode assembly, comprising a plurality of guide electrodes aligned along a central axis. Each guide electrode comprises an aperture. The apertures define an ion channel from a first end of the first electrode assembly to a second end of the first electrode assembly. The ion channel is configured to receive an ion beam at the first end. The guide electrodes are configured to receive RF voltages to define a confinement volume for the ion beam, wherein the confinement volume is centred about the central axis. The ion guide comprises a second electrode assembly adjacent to the first electrode assembly, wherein the second electrode assembly is configured to receive a DC voltage, such that a centre of the ion beam is deflected to be off the central axis.