Arcuate Ion Guide Rods for Compact Collision Cell Design
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Solution Overview
Problem
Existing mass spectrometer systems face challenges in reducing the size of components, particularly ion guides, while maintaining efficient ion transmission and minimizing ion loss during the transition from atmospheric pressure to high vacuum conditions, and in reducing noise and ion stalling within the collision cells.
Innovation Solution
The use of arcuate-shaped rods in the multipole ion guide collision cell, which creates a hexapole or other multipole electric field, allows for a more compact design by changing the ion guide path, reducing the overall footprint and noise, and incorporating a resistive outer layer for DC voltage application to manage ion flow and heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional straight rods are used in the collision cell, then the ion guide path is simple and direct, but the instrument size and footprint are large
Solution Approach 1:
The patent applies curvature to the ion guide rods by arranging them in an arcuate configuration rather than straight lines. This curved arrangement allows the ion guide to fit within a smaller spatial envelope while maintaining the necessary ion transmission path, directly reducing the instrument footprint without compromising ion guide functionality.
2Productivity
If DC voltage is applied to the rods to overcome ion stalling, then ion transmission is improved, but noise increases
Solution Approach 1:
The DC voltage application is segmented into discrete electrode regions rather than being continuously applied along the entire rod length. This segmentation allows DC voltage to be applied only in specific zones where ion stalling occurs, improving ion transmission efficiency while limiting the spatial extent of noise-generating electric fields.
Solution Approach 2:
Different regions of the ion guide structure are assigned different electrical properties - some regions have DC voltage applied to overcome stalling, while other regions maintain RF-only operation to minimize noise. This local differentiation optimizes ion transmission in critical zones while controlling noise in other areas.
3Temperature
If RF multipole ion guides are used for ion cooling, then ion energy is reduced, but ion transmission efficiency decreases due to ion stalling
Solution Approach 1:
The patent merges two previously separate functions into a single integrated structure: the ion cooling function (typically provided by RF multipole fields) and the ion acceleration function (typically provided by DC electric fields). By combining RF and DC voltage applications on the same rod structure, the system achieves both ion energy reduction and transmission efficiency improvement simultaneously.
Solution Approach 2:
The ion guide rods are designed to perform multiple functions: they generate RF multipole fields for radial ion confinement and cooling, while simultaneously serving as electrodes for DC voltage application to provide axial ion acceleration. This multi-functionality eliminates the need for separate cooling and acceleration components, improving overall system efficiency.
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 ion transmission efficiency, reduces noise, and allows for a smaller instrument size, while maintaining effective ion cooling and fragmentation capabilities, thereby improving the signal-to-noise ratio and molecular structure analysis.
Implementation Method 1
Ion guides typically utilize electromagnetic fields to confine the ions radially while allowing or promoting ion transport axially
Implementation Method 2
When operated in presence of a buffer gas, RF guides are capable of reducing the ion energy (velocity) of ions in both axial and radial directions. This reduction in ion energy in the axial and radial directions is known as 'thermalizing' or 'cooling' the ion populations due to multiple collisions of ions with low energy neutral molecules of the buffer gas
Implementation Method 3
This DC gradient, usually in the order of approximately 2 V to approximately 10 V, generates an accelerating voltage field compelling the ions to move along the axis of the collision cell ass
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
In an embodiment, an ion guide (102), comprises rods (201,202,203,301,302,303) each having a first end (204,205,206) and a second end (207,208,209) remote from the first end (204,205,206); an inductor (402) connected between adjacent pairs of rods (201,202,203,301,302,303); means for applying a radio frequency (RF) voltage (502) between adjacent pairs of rods (201,202,203,301,302,303), wherein the RF voltage creates a multipole field in a region between the rods (201,202,203,301,302,303); and means for applying a direct current (DC) voltage (505) drop along a length of each of the rods (201,202,203,301,302,303).