Time of Flight Mass Spectrometer ADC Signal Processing
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Solution Overview
Problem
Conventional mass spectrometers using Time to Digital Converters face challenges in distinguishing between single and multiple ion arrival events, leading to distorted intensity and mass-to-charge ratio measurements, especially at high ion fluxes, and suffer from dead time effects and limited dynamic range, while Analogue to Digital Converters can record intensity but introduce noise and reduce mass resolution.
Innovation Solution
A method involving digitizing ion detector signals to determine arrival times and intensities, calculating average arrival times and combined intensities for overlapping events, and processing these using differential signals to improve data accuracy and reduce noise, employing Analogue to Digital Converters with differential processing to enhance mass spectral data quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a Time to Digital Converter is used to record ion arrival times, then data processing is simplified and memory requirements are reduced, but the system cannot distinguish between single and multiple ion arrival events, leading to distorted intensity measurements
Solution Approach 1:
The patent segments the ion detection process into multiple measurement components: arrival time recording (handled by TDC) and intensity/charge measurement (handled by additional electronics that integrate signal area). This segmentation allows each component to optimize for its specific function while avoiding the limitations of using a single conversion method for both purposes.
Solution Approach 2:
The patent merges the capabilities of Time to Digital Conversion and Analogue to Digital Conversion into a hybrid system. The TDC records arrival times while additional circuitry simultaneously measures signal area for intensity determination. This combination resolves the contradiction by integrating the advantages of both conversion methods.
2Loss of information
If an Analogue to Digital Converter is used to record ion signals, then intensity information is captured, but noise is introduced and mass resolution is reduced
Solution Approach 1:
The patent applies different quality characteristics to different parts of the signal processing: high-speed timing information is captured with minimal processing (preserving resolution), while intensity information is extracted through integrated area measurement (preserving accuracy). Each measurement aspect receives tailored processing appropriate to its requirements.
Solution Approach 2:
Rather than fully converting the analogue signal to digital (which would capture all noise), the system performs partial measurement by integrating only the relevant signal area above threshold levels. This selective measurement approach captures intensity information while filtering out high-frequency noise that would degrade resolution.
3Loss of information
If multiple individual spectra are histogrammed to produce a final mass spectrum, then comprehensive data is collected, but processing time increases and real-time applications are hindered
Solution Approach 1:
The patent performs preliminary processing of each individual spectrum by extracting key parameters (arrival time and intensity) immediately upon detection. This preliminary action reduces the complexity of subsequent processing steps, allowing for faster aggregation of results without losing data completeness.
Solution Approach 2:
The patent extracts only the essential information from each full spectrum: the arrival time and intensity of ion signals. By taking out only these critical parameters for storage and further analysis, the system maintains data completeness for the most important measurements while dramatically reducing the volume of data requiring processing.
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 allows for accurate recording of multiple ion events, reduces noise, and improves mass spectral resolution and dynamic range, enabling more precise and reliable mass spectrometry data acquisition.
Implementation Method 1
Known Time of Flight mass analysers comprise an ion detector comprising a secondary electron multiplier such as a microchannel plate (MCP) or discrete dynode electron multiplier. The secondary electron multiplier or discrete dynode electron multiplier generates a pulse of electrons in response to an ion arriving at the ion detector.
Implementation Method 2
The arrival time is recorded as corresponding to the time when the leading edge of the ion signal passes through the voltage threshold.
Implementation Method 3
digitising a first signal output from an ion detector to produce a first digitised signal
Implementation Method 4
determining or obtaining a second differential or second difference of the first digitised signal; determining the arrival time T1 of one or more first ions from the second differential or second difference of the first digitised signal
Data Source
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AI summary
A Time of Flight mass analyser is disclosed comprising an ion detector comprising an Analogue to Digital Converter. Output signals from the ion detector are digitised and the arrival times and intensity values relating to ion arrival events are determined. If the determined arrival times from two signals fall within the same time window then the arrival times are added together in a weighted manner and the intensity values are combined.