Ion Guide Modulation Using Dual Traveling Wave Sections
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Solution Overview
Problem
Existing ion guide technologies are not precise enough in modulating a stream of ions according to a modulation function, leading to inaccuracies in determining ion mobility, especially when larger ions are involved, as they take longer to traverse a given distance due to higher collision cross-sections, resulting in artificial features in ion mobility spectra.
Innovation Solution
An ion guide assembly with a dual section design, featuring first and second arrangements of conveying electrodes generating traveling waves with specific amplitudes and velocities, where the ion gate is used to modulate the stream of ions, ensuring that each ion species experiences different wave conditions to achieve precise modulation, with the first section having a more trapping effect than the second.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single section ion guide is used with uniform traveling waves, then the device complexity is low, but the modulation precision of ion stream is insufficient leading to artificial features in spectra
Solution Approach 1:
The ion guide is divided into two distinct sections: a first section with first traveling waves and a second section with second traveling waves. Each section has different wave parameters (amplitude, velocity) to optimize for different ion mobility ranges. This segmentation allows precise modulation of ions with varying mobilities without requiring a completely complex redesign, as each section can be independently optimized.
Solution Approach 2:
Different sections of the ion guide are assigned different local properties: the first section uses traveling waves with specific amplitude and velocity optimized for certain ion species, while the second section uses different parameters optimized for other ion species. The ion gate position and wave parameters are locally optimized to achieve precise modulation for each section's specific ion mobility range.
2Measurement precision
If DC voltages are applied to convey ions, then the ion guide assembly is simple, but larger ions are pushed out of potential wells by gas resistance leading to inaccurate mobility determination
Solution Approach 1:
Instead of using static DC voltages, the patent applies periodic AC voltages that generate traveling waves. These traveling waves create moving potential wells that continuously propel ions forward while maintaining confinement. The periodic nature of the waves prevents larger ions from being pushed out by gas resistance, as the moving potential minimum continuously pulls them forward along with smaller ions.
Solution Approach 2:
The patent changes the voltage parameters from static DC levels to dynamic AC waveforms with specific frequencies and amplitudes. By adjusting the voltage parameters (frequency, amplitude, phase) of the traveling waves, the system can optimize the potential well depth and velocity to accommodate ions of different sizes and mobilities, preventing larger ions from being pushed out while maintaining simple overall device architecture.
3Measurement precision
If a single traveling wave velocity is used throughout the ion guide, then the control system is simple, but ions of different mobilities cannot be conveyed uniformly resulting in spectral artifacts
Solution Approach 1:
The ion guide path is segmented into two sections, each with its own traveling wave velocity optimized for specific ion mobility ranges. The first section uses first traveling waves with velocity v1 optimized for ions with mobility in a certain range, while the second section uses second traveling waves with velocity v2 optimized for ions with different mobility characteristics. This segmentation enables uniform conveyance of ions with widely varying mobilities.
Solution Approach 2:
The system transitions from a static, uniform velocity field to a dynamic, spatially varying velocity field. By making the traveling wave velocity a function of position (different velocities in different sections), the system can adapt to ions of different mobilities as they progress through the guide, ensuring uniform conveyance across the full range of ion types without requiring overly complex real-time control.
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 approach allows for more precise modulation of ions, ensuring that ions of varying mobilities are conveyed uniformly, reducing artificial features in ion mobility spectra and enhancing the accuracy of ion mobility determination.
Implementation Method 1
the first arrangement of conveying electrodes is adapted for generating first travelling waves having a first travelling wave amplitude and travelling along the first section of the ion guide path at a first travelling wave velocity for conveying the ions along the first section of the ion guide path
Implementation Method 2
AC voltages are applied to the first arrangement of conveying electrodes for generating the first travelling waves and to the second arrangement of conveying electrodes for generating the second travelling waves
Implementation Method 3
the ion gate is adapted to provide an open state for allowing the ions passing the ion gate position when being conveyed along the ion guide path and a closed state for preventing the ions from passing the ion gate position
Implementation Method 4
the first arrangement of conveying electrodes is adapted for generating first travelling waves having a first travelling wave amplitude and travelling along the first section of the ion guide path at a first travelling wave velocity for conveying the ions
Implementation Method 5
for conveying the ions along the ion guide path in a conveying direction
Data Source
AI summary
The invention relates to a method for, in an ion guide (10), modulating a stream of ions according to a modulation function, wherein the stream of ions includes at least N different ion species, wherein N is at least 1. This ion guide (10) forms an ion guide path, wherein the ions of the stream of ions are conveyed along the ion guide path in a conveying direction to form the stream of ions. The ion guide (10) includes an ion gate (12) arranged at an ion gate position on the ion guide path, wherein the ion gate (12) is adapted to provide an open state for allowing the ions passing the ion gate position when being conveyed along the ion guide path and a closed state for preventing the ions from passing the ion gate position. The ion guide (10) further includes a first arrangement (13) of conveying electrodes (230) arranged along the ion guide path, the first arrangement (13) of conveying electrodes (230) extending over a first section of the ion guide path, wherein the first section of the ion guide path reaches from at least the ion gate position downstream to at least a transition position on the ion guide path, wherein the first arrangement (13) of conveying electrodes (230) is adapted for generating first travelling waves having a first travelling wave amplitude and travelling along the first section of the ion guide path at a first travelling wave velocity for conveying the ions along the first section of the ion guide path. Furthermore, the ion guide (10) includes a second arrangement (14) of conveying electrodes (240) arranged along the ion guide path, the second arrangement (14) of conveying electrodes (240) extending over a second section of the ion guide path, wherein the second section of the ion guide path reaches from the transition position downstream, wherein the second arrangement (14) of conveying electrodes (240) is adapted for generating second travelling waves having a second travelling wave amplitude and travelling along the second section of the ion guide path at a second travelling wave velocity for conveying the ions along the second section of the ion guide path. According to the method, the stream of ions is modulated with the ion gate (12) according to the modulation function and AC voltages are applied to the first arrangement (13) of conveying electrodes (230) for generating the first travelling waves and to the second arrangement (14) of conveying electrodes (240) for generating the second travelling waves for conveying the ions downstream of the ion gate (12) along the first section and the second section of the ion guide path in the conveying direction away from the ion gate (12), wherein for each ion species of the at least N different ion species, a ratio A is the average velocity of the ions of the respective ion species in the first section of the ion guide path divided by the first travelling wave velocity, wherein for each ion species of the at least N different ion species, a ratio B is the average velocity of the ions of the respective ion species in the second section of the ion guide path divided by the second travelling wave velocity, wherein the first travelling wave amplitude, the first travelling wave velocity, the second travelling wave amplitude and the second travelling wave velocity are chosen such that for each ion species of the at least N different ion species, the ratio A is larger than the ratio B.