Segmented Ion-Optical Mirrors for Time-of-Flight Aberration Control
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Solution Overview
Problem
Existing multi-reflection mass spectrometers face challenges in achieving high resolution due to manufacturing difficulties of parabolically-shaped ion-optical mirrors, which require stringent tolerances that are hard to achieve, leading to time-of-flight aberrations and spatial focusing issues.
Innovation Solution
The ion-optical mirrors are designed with a combination of straight and curved electrodes, where high voltage differences are applied between straight edges for precise fabrication, and smaller voltage differences between curved edges to mitigate tolerance requirements, allowing for isochronous ion motion and reduced time-of-flight aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If parabolically-shaped ion-optical mirrors are used to achieve spatial focusing and isochronous ion motion, then time-of-flight separation and resolution are improved, but manufacturing precision requirements become excessively stringent and difficult to achieve
Solution Approach 1:
The ion-optical mirror is segmented into multiple straight electrode segments arranged in a specific geometric pattern. Instead of requiring a single continuous parabolic surface, the system uses discrete straight electrodes (e.g., five electrodes forming a segmented mirror) that collectively provide the necessary ion-optical focusing effect, thereby relaxing manufacturing tolerance requirements while maintaining functional performance
Solution Approach 2:
Different regions of the ion-optical system use different electrode configurations - straight electrodes in certain positions and curved electrodes in others - with each region optimized for its specific function. This allows the system to achieve overall parabolic focusing effect through combination of simpler local elements with less stringent manufacturing requirements
2Manufacturing precision
If curved electrodes are used to achieve proper ion focusing, then spatial focusing is improved, but ease of manufacture deteriorates due to difficulty in achieving tight tolerances on curved surfaces
Solution Approach 1:
Instead of using curved electrodes to achieve focusing (the conventional approach), the invention inverts the approach by using straight electrodes arranged in a specific geometric configuration to achieve the same focusing effect. This inversion replaces difficult curved surface fabrication with easier straight edge fabrication while maintaining the necessary ion-optical performance
3Productivity
If mirrors are tilted to extend ion flight path for increased time-of-flight separation, then mass resolution is improved, but time-of-flight aberrations are introduced due to varying ion paths
Solution Approach 1:
The system uses electrostatic feedback fields generated by the segmented electrode configuration to correct for path length variations among ions. The electric field distribution is adjusted to compensate for differences in ion trajectories, ensuring that ions with different initial angles still arrive at the detector with minimal time-of-flight differences, thereby eliminating aberrations introduced by tilted mirror geometry
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 design achieves high resolution mass spectrometry by compensating time-of-flight aberrations and spatial focusing, enabling precise ion detection without the need for extremely tight manufacturing tolerances on curved surfaces.
Implementation Method 1
The mirrors are tilted by an angle θ such that their separation in the drift direction away from the ion source decreases. Ions are injected into the mirrors at an initial inclination angle, and the mirror convergence tilt angle θ causes the trajectory inclination angle of the ions to decrease
Implementation Method 2
in time-of-flight (ToF) mass spectrometers, it increases the ability to distinguish small mass differences between ions
Data Source
AI summary
A multi-reflection mass analyser comprises a pair of opposed ion-optical mirrors elongated linearly along a longitudinal axis that extends centrally through the mass analyser, and either one or both ion-optical mirrors comprises a series of spaced apart electrodes. Each electrode is elongated along the longitudinal axis. The series of electrodes extend in a direction transverse to the longitudinal axis and the electrodes are spaced apart by a series of gaps. The series of electrodes comprises a first pair of adjacent electrodes and a second pair of adjacent electrodes. The first pair of adjacent electrodes are separated by a straight gap defined by respective straight edges of the adjacent electrodes. The second pair of adjacent electrodes are separated by a curved gap defined by respective curved edges of the adjacent electrodes.