Multi-Reflection Mass Spectrometer Focal Plane Correction
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Solution Overview
Problem
High mass resolution time-of-flight mass spectrometers face challenges with temporal aberrations due to tilted mirror electrodes and slow response times of power supplies, which limit the ability to adjust focal plane positions quickly and maintain high resolution across varying ion densities.
Innovation Solution
The introduction of a focal plane correction electrode that extends along the drift direction between the mirror electrodes allows for rapid adjustment of the focal plane position by applying a perturbation field with lower potential requirements, enabling fine-tuning of the focal plane without affecting the ion reflection process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If tilted mirror electrodes are used to extend ion flight path, then time-of-flight separation is improved, but temporal aberrations are introduced
Solution Approach 1:
A focal plane correction electrode is introduced as an intermediary element between the tilted mirror electrodes and the detector. This electrode generates a compensating electric field that corrects the temporal aberrations caused by the tilted mirrors, allowing the benefits of extended flight path to be realized without the detrimental timing effects
2Reliability
If stripe electrodes are used to correct temporal aberrations, then average ion velocity is adjusted, but device complexity increases
Solution Approach 1:
The correction function is extracted from the complex striped electrode configuration and consolidated into a single focal plane correction electrode. This simplifies the device structure while maintaining the ability to correct temporal aberrations through a unified electric field generation mechanism
3Measurement precision
If power supply voltage is adjusted to correct focal plane position, then focal plane alignment is improved, but response time increases
Solution Approach 1:
The focal plane correction electrode serves as a mediator that enables rapid focal plane adjustment through low-voltage operation. By using this intermediate electrode rather than adjusting the main power supply voltage, the system achieves fast response times while maintaining precise focal plane alignment
4Duration of action of moving object
If mirror electrode separation decreases along drift direction, then ion oscillation period is reduced, but temporal aberration increases
Solution Approach 1:
The focal plane correction electrode applies a preliminary compensating effect that counteracts the temporal aberration caused by the decreasing mirror separation. By establishing this counteracting electric field in advance, the system prevents the accumulation of temporal errors throughout the ion flight path
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 solution allows for rapid and precise adjustment of the focal plane position, mitigating the effects of space charge and enabling fast switching between normal and zoom modes, thus enhancing the dynamic range and resolving power of the mass spectrometer.
Implementation Method 1
providing a perturbation field with lower potential requirements, enabling fine-tuning of the focal plane
Implementation Method 2
providing an electrical potential to the mirror electrodes that reflects the ions in the resulting ion beam
Implementation Method 3
high mass resolution time-of-flight mass spectrometry
Data Source
AI summary
A multi-reflection time of flight mass spectrometer comprises a mass analyser with opposing mirror electrodes and a focal plane correction electrode. Each mirror electrode is elongated generally along a drift direction. The focal plane correction electrode extends along at least a portion of the drift direction in or adjacent the space between the mirror electrodes. Ions are injected into the mirror electrodes and an electrical potential provided to the mirror electrodes reflects the ions in the resulting ion beam and causes the ions to follow a zig zag path as they drift along the mirror electrodes. An electrical potential is also provided to the focal plane correction electrode to set the focal plane position of the ion beam to coincide with a detector surface of an ion detector placed at the end of the ions' path.