TOF MS Detection with Secondary Electron Attenuation for Wide Dynamic Range
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Solution Overview
Problem
Conventional time-of-flight mass spectrometers face limitations in dynamic range and detector longevity due to saturation and spectral distortion issues, particularly with high ion fluxes and intense signals, which current methods fail to adequately address.
Innovation Solution
The method involves pulsing ions into a time-of-flight region, attenuating secondary particles generated at different rates or amounts based on constant settings for each time period to prevent detector saturation and spectral distortion, allowing for the detection of both intense and less intense signals without distorting the mass spectral data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional detectors are used to detect high ion fluxes, then detector sensitivity is maintained, but detector saturation and spectral distortion occur
Solution Approach 1:
The detector is divided into two independent detection channels: a first detection channel for detecting intense ion signals and a second detection channel for detecting less intense ion signals. Each channel has its own detector and processing circuitry, allowing simultaneous optimization for different signal intensity ranges without mutual interference.
Solution Approach 2:
The patent transitions from single-channel detection to multi-channel parallel detection, adding a dimensional aspect of signal intensity-based channel selection. This allows the system to handle a wider dynamic range by operating in multiple detection dimensions simultaneously.
2Measurement precision
If detector amplification gain is increased to detect weak signals, then detection sensitivity for weak signals improves, but intense signals cause saturation
Solution Approach 1:
The detection system is segmented into two channels with different amplification gains optimized for different signal intensity ranges. The first channel uses high amplification gain for weak signals while the second channel uses low amplification gain for intense signals, eliminating the need to compromise between these conflicting requirements.
Solution Approach 2:
Each detection channel is locally optimized for its specific function: the first channel is optimized with high amplification gain for detecting weak signals, while the second channel is optimized with low amplification gain for handling intense signals. This local optimization allows each channel to perform its specific detection task effectively.
3Device complexity
If single detector setting is used, then device complexity is reduced, but dynamic range is limited
Solution Approach 1:
The detector system is segmented into two independent detection channels, each with its own detector and processing circuitry optimized for different signal intensity ranges. This segmentation enables the system to achieve a wide dynamic range while maintaining relatively simple individual channel designs.
Solution Approach 2:
The dual-channel detection system provides multi-functionality by simultaneously detecting both intense and weak ion signals within the same instrument. This universal detection capability allows a single mass spectrometer to handle a wide variety of sample types and ion flux conditions without requiring multiple specialized instruments.
4Duration of action of stationary object
If detector amplification is instantly limited to prevent saturation, then detector life-time is extended, but dynamic range is reduced
Solution Approach 1:
The detection system is segmented into two channels that simultaneously operate with different amplification settings. This eliminates the need for dynamic amplification limiting that would reduce the dynamic range, as both high and low gain channels operate continuously without needing to switch or limit their amplification.
Solution Approach 2:
Both detection channels operate continuously and simultaneously, providing uninterrupted detection across the full dynamic range. This continuous multi-channel operation maintains detector life-time by preventing saturation in either channel while preserving the full dynamic range capability.
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 significantly enhances the dynamic range of time-of-flight mass spectrometers, enabling the detection of ion fluxes up to 1E+9 ions/sec with improved detector longevity and minimal spectral distortion, achieving a dynamic range greater than 1E+7/sec.
Implementation Method 1
converting the ions into secondary particles at the ion converter
Implementation Method 2
pulsing packets of ions into a time-of-flight region such that they separate according to mass to charge ratio as they travel therethrough
Data Source
AI summary
Apparatus and method are proposed for the strong improvement of dynamic range (DR) of detectors and of data systems for time-of-flight mass spectrometers (TOF MS) with periodically repetitive signals. TOF separated ions are converted into secondary particles, primarily electrons, and the flow of secondary particles is controllably attenuated to sustain the data acquisition system in a counting mode above the electronic noise threshold. The acquisition time is split between at least two time segments, characterized by alternated transmission efficiency SE of secondary particles. Using strong electron suppression (SE«1) is employed for recording intense ion peak, while counting ions with either ADC, or TDC, or ADC with extracting peak centroids. A longer time segment employs an efficient electron transfer (SE=1) for detecting weak ion species. In another independent aspect, an ion-optical element is provided upstream of the ion detector and is configured to deflect, reflect or retard ions such that ions that have been scattered or fragmented in the time of flight region do not impact on the ion detector.