Ion Trapping System Orthogonal Dispersion
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Solution Overview
Problem
Mass spectrometers with ion traps face challenges in high space-charge capacity at elevated pressures, leading to ion dissociation and distortion in ion mobility separation due to increased local charge density, particularly affecting thermally labile compounds.
Innovation Solution
The ion trapping system disperses ions orthogonally to the entrance and exit axes, extending the ion trapping region in one dimension to reduce space-charge effects, allowing for a higher charge capacity while minimizing spatial spread, and using a transient DC voltage that decreases in force towards the exit to alleviate space charge issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ions are accumulated in the ion trap from an upstream ion source to increase duty cycle, then the ion trapping capacity is improved, but the local charge density increases causing ion dissociation due to heating from proximity to radial confining RF fields
Solution Approach 1:
The patent introduces a new spatial dimension by operating the ion trap at elevated pressures (0.2-20 mbar) similar to the IMS device pressure, rather than maintaining ultra-high vacuum. This pressure change fundamentally alters the ion transport mechanism from vacuum-based to gas-filled diffusion and mobility-driven transport, enabling three-dimensional ion distribution that reduces peak charge density while maintaining trapping capacity
Solution Approach 2:
The patent changes the operating pressure parameter from ultra-high vacuum to elevated pressure (0.2-20 mbar), which fundamentally changes the ion transport physics. At these pressures, gas molecule interactions dominate ion motion, reducing the impact of RF field heating and preventing ion dissociation while allowing high ion accumulation
2Object-affected harmful factors
If the ion trapping region is extended in one dimension to reduce space-charge effects, then the ion distribution is improved, but the spatial spread parallel to the exit axis increases
Solution Approach 1:
The patent extends the ion trapping region in the radial dimension (orthogonal to the exit axis) by operating at elevated pressures where gas-filled ion transport allows broader spatial distribution. This radial extension reduces space-charge effects without increasing the axial length, maintaining compact ion packets at the exit
3Quantity of substance
If high charge density is maintained in the ion trap, then the ion trapping capacity is improved, but RF heating in the IMS device and distortions in IMS peak width and drift time occur during separation
Solution Approach 1:
The patent uses elevated pressure operation to enable radial ion distribution in three dimensions, reducing the linearity of ion packets as they enter the IMS device. This spatial redistribution maintains high total ion capacity while reducing peak charge density, thereby minimizing RF heating and preserving IMS separation 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 configuration enhances the ion trapping capacity while maintaining a small spatial spread parallel to the exit axis, reducing ion dissociation and distortion, and improves the resolution of downstream ion separation devices by evenly distributing ions and reducing peak charge density.
Implementation Method 1
an RF confined ion trap upstream of an ion mobility separator (IMS) device
Implementation Method 2
at such relatively high pressures that the ions lose their kinetic energy by interactions with the background gas molecules
Implementation Method 3
The ion trapping system disperses ions away from the entrance and/or exit axis, thereby reducing space-charge effects during filling of the ion trapping region with ions
Implementation Method 4
an ion mobility separator (IMS) device in order to increase the duty cycle of the instrument
Data Source
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AI summary
An wide ion trapping system is disclosed comprising an ion urging system for urging ions to spread out orthogonally within an ion trapping region. Alternatively, the ion trapping system may deflect ions such that ions enter the ion trapping region at different locations. Alternatively, an ion deflector may be arranged upstream of, or at the entrance to, the ion trapping region, for deflecting ions orthogonally such that ions enter the ion trapping region with different speeds so that the ions spread out within the ion trapping region. In a second aspect, an ion trapping system is disclosed comprising an ion urging system configured to translate at least one transient DC voltage along the ion trapping region from the ion entrance to the ion exit for urging ions along the ion trapping region, wherein the force applied by the transient DC voltage decreases as the transient DC voltage travels from the ion entrance to the ion exit; and a control system configured to control the one or more voltage supplies to apply one or more voltages to the electrodes to prevent ions being ejected from the ion trapping region by the at least one transient DC voltage when the transient DC voltage reaches the ion exit.