Multireflection TOF Mass Spectrometer Ion Mirror Design
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Solution Overview
Problem
Multireflection time-of-flight (TOF) mass spectrometers face limitations in mass range analysis due to ion mixing and defocusing issues, particularly when increasing the flight path length, which restricts the resolving power and requires complex and costly additional components to maintain focus.
Innovation Solution
The design incorporates a multireflection TOF mass spectrometer with ion mirrors having a cross-section with a minor axis (Y) and major axis (X) perpendicular to the longitudinal axis, allowing ions to intersect a plane of symmetry multiple times, creating a 'gamma' trajectory, enabling multiple reflections with reduced space charge effects and eliminating the need for additional focusing means.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the flight path length is increased to improve resolving power, then the resolving power is improved, but ion mixing occurs and mass range is limited
Solution Approach 1:
The patent transitions from linear ion flight paths to three-dimensional trajectories using electrostatic mirrors. Ions follow curved paths in multiple dimensions, reflecting off mirrors positioned at angles to create extended flight paths without requiring long linear distances. This dimensional transformation allows high resolving power while maintaining compact instrument size and avoiding ion mixing.
Solution Approach 2:
The patent implements a nested mirror configuration where multiple electrostatic mirrors are arranged in sequence along the ion flight path. Each mirror reflects ions through a specific angular deviation, and the mirrors are positioned such that ions pass through multiple reflection stages. This nesting of reflection events within a compact space enables extended effective flight path length without proportionally increasing instrument size.
2Manufacturing precision
If multiple planar lenses are added to refocus ions, then spatial focusing is improved, but device complexity and cost increase
Solution Approach 1:
The electrostatic mirrors in the patent serve dual functions: they provide the necessary angular deviation to extend the ion flight path length while simultaneously providing spatial focusing of the ion beam. The mirrors are positioned and angled to reflect ions through specific trajectories that naturally converge at the detector plane. This eliminates the need for separate focusing components, reducing device complexity while maintaining focusing precision.
Solution Approach 2:
The patent combines the path-length extension function and the spatial focusing function into a single integrated mirror system. The electrostatic mirrors are configured such that their reflection geometry inherently provides both the extended flight path and the beam convergence needed for spatial focusing. This merging of functions reduces the number of components and simplifies the overall device architecture.
3Length of stationary object
If coaxial mirrors are used for multireflection, then flight path length is extended, but ion mixing occurs and mass range is restricted
Solution Approach 1:
The patent employs asymmetric mirror arrangements where mirrors are positioned at different angles and locations rather than in symmetric coaxial configurations. The first and second electrostatic mirrors are angled relative to each other, creating non-coaxial reflection paths. This asymmetry prevents ions of different mass-to-charge ratios from following identical trajectories, thereby avoiding ion mixing while still achieving extended flight path lengths through multiple reflections.
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 allows for a large path length while minimizing ion mixing, enhancing spatial focusing, and reducing space charge effects, thereby improving the mass range and resolving power without the need for additional focusing components, thus optimizing the mass spectrometer's performance.
Implementation Method 1
accelerating ions in an electric field
Implementation Method 2
multireflection time-of-flight mass spectrometry (MR TOF-MS) has been developed
Implementation Method 3
time-of-flight mass spectrometry (TOF-MS) involves accelerating ions in an electric field and then drifting them to a detector at a known distance. Ions of different mass to charge ratios (m/z) but having the same kinetic energy move at different velocities towards the detector and so separate according to their m/z.
Data Source
AI summary
A method of reflecting ions in a multireflection time of flight mass spectrometer is disclosed. The method includes guiding ions toward an ion mirror having multiple electrodes, and applying a voltage to the ion mirror electrodes to create an electric field that causes the mean trajectory of the ions to intersect a plane of symmetry of the ion mirror and to exit the ion mirror, wherein the ion are spatially focussed by the mirror to a first location and temporally focused to a second location different from the first location. Apparatus for carrying out the method is also disclosed.