Coaxial Ion Guide Space Charge Capacity
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Solution Overview
Problem
The space charge capacity limitations in conventional ion mobility spectrometers lead to ion loss, mass discrimination, and fragmentation due to excessive charge in the trapping region, which reduces the device's performance and resolution.
Innovation Solution
An annular or co-axial ion trap with a toroidal trapping geometry and RF or AC voltage application to confine ions radially and axially, increasing the space charge capacity and conditioning the ion population for direct injection into a coaxial ion guide, while using transient DC voltages to eject and focus ions efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the axial length of the trapping region is extended to increase charge capacity, then the space charge capacity is improved, but the resolution of the downstream ion mobility spectrometer is reduced
Solution Approach 1:
The invention transitions from a conventional linear trapping region to a three-dimensional环形 (annular) trapping region. This dimensional change allows ions to be confined in both axial and radial directions, significantly increasing the charge capacity without extending the axial length that would degrade resolution. The annular geometry provides volumetric confinement while maintaining a compact axial footprint.
Solution Approach 2:
The invention employs curved annular electrodes instead of straight linear electrodes to define the trapping region. This curvature enables the formation of a toroidal or annular trapping volume that maximizes space charge capacity within a limited axial space, thereby maintaining high resolution while accommodating large ion populations.
2Productivity
If excessive charge is stored in the trapping region to increase duty cycle, then the productivity is improved, but ion loss and fragmentation occur due to space charge effects
Solution Approach 1:
The annular trapping region is designed to pre-condition ion packets by providing stable three-dimensional confinement before injection into the ion mobility spectrometer. This preliminary confinement allows ions to be stored at high densities without immediate space charge effects, and enables controlled ejection that minimizes fragmentation and loss during transfer.
Solution Approach 2:
The invention uses RF voltages applied to the annular electrodes to dynamically control the trapping and ejection of ions. By modulating the RF parameters, the system can accommodate varying charge densities while maintaining stable confinement, thereby preventing ion loss and fragmentation even when storing excessive charges to maximize duty cycle.
3Device complexity
If conventional circular trapping geometry is used, then the device complexity is low, but the space charge capacity is limited
Solution Approach 1:
The invention adds radial confinement to the conventional axial trapping geometry, transforming a one-dimensional linear trap into a two-dimensional annular trap. This additional dimensional constraint creates a three-dimensional confinement volume that dramatically increases space charge capacity while maintaining relatively simple electrode structures.
Solution Approach 2:
The annular electrodes are formed with curved geometries that define a toroidal or ring-shaped trapping region. This curved configuration maximizes the volume available for ion confinement within a compact structure, significantly increasing space charge capacity compared to linear geometries without requiring proportionally higher device complexity.
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 significantly enhances the space charge capacity, reduces ion loss, and maintains high resolution by effectively confining and ejecting ions, thereby improving the overall performance and efficiency of the ion mobility spectrometer.
Implementation Method 1
the nature of the confining force provided by the RF confinement field
Implementation Method 2
Ions are extracted from the device by a potential difference between an annular conductive strip and an exit plate
Implementation Method 3
ions are separated according to their ion mobilities
Data Source
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AI summary
A method of mass and/or ion mobility spectrometry is disclosed comprising: trapping ions in an annular or co-axial ion trap (4); and then axially ejecting at least some of said ions from said annular or co-axial ion trap (4) into an annular ion guide (3). Ions trapped in the ion trap (4) are distributed around the entire circumference of the annular or co-axial ion trap. As the ions travel along at least a portion of the length of the ion guide their motion around the circumference of the annular ion guide is unrestricted and the ions separate axially as they travel along the ion guide.