Orthogonal Acceleration TOF Mass Spectrometer Ground Potential
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Solution Overview
Problem
Conventional orthogonal acceleration time-of-flight mass spectrometers are limited by the voltage withstanding performance of the ion detector, leading to reduced quantitativeness and sensitivity due to capacitive coupling issues.
Innovation Solution
A potential lifting mechanism is introduced immediately ahead of the orthogonal acceleration region, allowing the ion source and detection system to be placed near ground potential, enabling higher accelerating voltages and improving sensitivity by avoiding capacitive coupling restrictions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the ion detector is coupled capacitively to the data collection system at ground potential, then the ion source can be installed at close to ground potential, but the baseline of the spectrum sags immediately after high-intensity ion detection, severely deteriorating quantitativeness
Solution Approach 1:
A grounded conductive box is introduced as an intermediary component between the ion source and the detector. The box is held at ground potential through a grounding connection, while ions are accelerated into it by a pulsed voltage. This mediator allows the ion source to remain at ground potential (improving ease of operation) while preventing direct capacitive coupling between the detector and ground potential system (preserving quantitativeness), as the box electrically isolates these two components.
2Adaptability or versatility
If the detector is floated at -5 to -10 kV to enable orthogonal acceleration, then mass separation can be performed, but the voltage withstanding characteristics of the detector limit the accelerating voltage and reduce sensitivity
Solution Approach 1:
The system is segmented into distinct voltage domains: the ion source and conductive box are maintained at ground potential, while the detector operates at a floated potential of -5 to -10 kV. The pulsed voltage acceleration region bridges these domains. This segmentation allows orthogonal acceleration to function (adaptability) while the ground-potential components do not suffer from voltage withstanding limitations (reliability), as only the detector needs to withstand the high voltage, and it does so in a controlled floated state.
3Measurement precision
If higher accelerating voltages are applied to improve sensitivity, then the detection capability is enhanced, but the voltage withstanding characteristics of the detector prevent using sufficiently high voltages
Solution Approach 1:
The problem is solved by adding a temporal dimension to the voltage application. Instead of continuously applying high voltage (which would exceed detector withstanding capability), a pulsed voltage is applied only during the brief ion acceleration window. This allows high accelerating voltages to be used (improving sensitivity) while the detector is protected during non-pulse periods when the full voltage is not present (maintaining reliability within voltage withstanding limits).
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 enhances the sensitivity and quantitativeness of the mass spectrometer by allowing higher accelerating voltages and reducing capacitive coupling issues, improving the overall performance and handling of the apparatus.
Implementation Method 1
In the orthogonal acceleration region, a pulsed voltage of about 10 kV is generated using a pulse voltage power supply 35 and applied such that the ions are accelerated in a direction orthogonal to the direction in which the ions are conveyed from the ion source
Implementation Method 2
The times taken for the ions to reach the detector 36 after the application of the pulsed voltage are different according to the masses of the ions. Thus, mass separation is performed
Implementation Method 3
In figure 3 the orthogonally accelerated ions are reflected in a reflector 38 so as to continue to the detector
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
An orthogonal acceleration TOF (time-of-flight) mass spectrometer is offered which is not affected by the voltage withstanding performance of ion detection means. The mass spectrometer has: an ion source for ionizing a sample; a conductive box into which the created ions are introduced; ion acceleration means placed inside or behind the conductive box and causing the ions to be accelerated in a pulsed manner in synchronism with a signal giving a starting point of measurement; and ion detection means for detecting the ions in synchronism with the acceleration of the ions. The conductive box is provided with an ion injection port and an ion exit port. A voltage is applied to the conductive box. This voltage is switched in synchronism with the signal giving the starting point of the measurement.