Secondary-Electron Multiplier Amplification Adjustment
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Solution Overview
Problem
The amplification of secondary-electron multipliers in mass spectrometers changes over time due to aging, making it difficult to determine the optimal setting, leading to noisy spectra and reduced instrument life, as the ion generation and multiplier amplification compensate each other, and existing mass spectrometers lack measurement devices to independently determine multiplier amplification.
Innovation Solution
A method to adjust the amplification of secondary-electron multipliers by acquiring mass spectra with single ion signals, calculating the average peak heights, and adjusting the supply voltage to achieve a desired average peak height, utilizing the known characteristic of the multiplier's amplification-voltage relationship, which can be automated using computer control programs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the amplification of the secondary-electron multiplier is increased to improve signal detection, then the signal quality improves, but the life of the multiplier is reduced and the mass spectrum becomes noisy
Solution Approach 1:
The patent implements a feedback mechanism where the system automatically monitors the ion current signal and adjusts the multiplier amplification accordingly. The control unit continuously adapts the amplification level to maintain optimal signal quality without excessive amplification, thereby extending multiplier life while preserving measurement precision.
Solution Approach 2:
The system dynamically changes the amplification parameter based on real-time signal conditions. By adjusting the amplification factor according to the detected ion current strength, the system achieves high measurement precision when needed while avoiding the detrimental effects of constantly high amplification on multiplier life.
2Measurement precision
If the amplification of the secondary-electron multiplier is set high to detect weak signals, then weak ion signals become detectable, but the mass spectrum becomes unnecessarily noisy and too few ions are measured
Solution Approach 1:
The patent transforms the static amplification setting into a dynamic parameter that automatically adapts to signal conditions. The system continuously monitors ion current strength and adjusts amplification in real-time, enabling detection of weak signals without the harmful effects of fixed high amplification that causes noise and ion loss.
Solution Approach 2:
A feedback control loop monitors the ion current signal and automatically adjusts the multiplier amplification. When weak signals are detected, amplification is increased to improve detectability; when signals are strong, amplification is reduced to prevent noise and maintain accurate ion counting.
3Measurement precision
If the ion current is increased to improve signal quality, then the signal strength improves, but the ion trap becomes overfilled and mass resolving power is reduced
Solution Approach 1:
The system implements feedback control where the control unit continuously monitors the ion image and ion current level. When the ion trap approaches overfill conditions, the system automatically reduces the ion current to maintain optimal trap filling, thereby preserving mass resolving power while still achieving sufficient signal quality through optimized amplification settings.
Solution Approach 2:
The patent dynamically adjusts multiple parameters including ion current level and multiplier amplification. By coordinating changes in these parameters, the system maintains optimal ion trap filling for high mass resolving power while ensuring sufficient signal quality through appropriate amplification levels determined by real-time monitoring.
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 reproducible adjustment of the multiplier amplification, ensuring accurate determination of ion numbers and distribution, improving the quality of mass spectra and extending the life of the instrument by maintaining optimal operating conditions.
Implementation Method 1
the amplification of a secondary-electron multiplier does not remain constant over its lifetime but is always changing when in use as a result of aging processes
Data Source
AI summary
The amplification of secondary-electron multipliers in mass spectrometers is automatically adjusted by generating mass spectra with single ion signals, determining the average value of the peak heights of these single ion signals, and setting the amplification so that the average peak height assumes a desired nominal value. The amplification may be set via the supply voltage of the secondary-electron multiplier and can be increased or decreased by a desired factor using the known characteristic of the secondary-electron multiplier.