Secondary-Electron Multiplier Voltage Control for Mass Spectrometer Life
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Solution Overview
Problem
Secondary-electron multipliers in mass spectrometers age quickly due to high operating voltages, leading to reduced amplification and frequent replacements, which are costly and disruptive, especially in time-of-flight mass spectrometers used for high-throughput analysis.
Innovation Solution
Operating the secondary-electron multiplier at a significantly lower voltage, typically around 10^5 or 2×10^4, and using a low-noise preamplifier close to the multiplier to amplify the output signal, thereby reducing the energy input and slowing down the aging process, while maintaining sufficient signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the operating voltage of the secondary-electron multiplier is increased to maintain amplification, then the amplification is preserved, but the aging process intensifies and service life is reduced
Solution Approach 1:
A feedback control system continuously monitors the amplification output of the secondary-electron multiplier and automatically adjusts the operating voltage to maintain optimal amplification levels. This prevents manual over-volting and extends service life by keeping the voltage at the minimum necessary level rather than allowing it to drift upward over time
Solution Approach 2:
The patent changes the operating parameter (voltage) from a fixed high value to a dynamically controlled value that adapts to the aging state of the multiplier. By monitoring amplification output and adjusting voltage accordingly, the system maintains performance while reducing the intensity of the aging-causing high voltage exposure
2Duration of action of stationary object
If the operating voltage is reduced to slow aging, then service life is extended, but the amplification decreases and signal detection becomes difficult
Solution Approach 1:
The feedback control system monitors the amplification output and automatically increases the voltage only when necessary to maintain the required amplification level. This ensures the voltage is kept as low as possible (extending service life) while still achieving the necessary amplification for reliable detection
Solution Approach 2:
The operating voltage is made dynamic rather than static, allowing it to vary over time based on the actual performance needs and the aging state of the multiplier. This dynamic adjustment optimizes the balance between service life extension and maintaining sufficient amplification
3Reliability
If high operating voltage is used to achieve sufficient amplification, then signal detection is reliable, but the energy input intensifies aging and reduces service life
Solution Approach 1:
The feedback system ensures that the voltage is increased only to the extent necessary for reliable signal detection, not to excessive levels. By continuously monitoring the output and adjusting accordingly, the system avoids the intensified aging that would result from consistently high voltage operation while maintaining detection reliability
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 extends the service life of the secondary-electron multiplier by a factor of three to five, reducing the need for frequent replacements and minimizing operational interruptions, while maintaining high mass resolution and accuracy.
Implementation Method 1
The ions impinge on the first dynode, where they generate secondary electrons, which are accelerated and then impinge onto the second dynode. Each of these electrons then generates several secondary electrons on average, so that an avalanche of electrons forms along the dynodes.
Implementation Method 2
Each of these electrons then generates several secondary electrons on average, so that an avalanche of electrons forms along the dynodes.
Implementation Method 3
The output current of the secondary-electron multiplier is amplified by means of a low-noise preamplifier mounted close to the secondary-electron multiplier with such a low noise level that the current pulses of individual ions impinging on the ion detector are detected above the noise at the input of a digitizing unit.
Data Source
AI summary
The disclosure relates to a method of operating a secondary-electron multiplier in the ion detector of a mass spectrometer so as to prolong the service life, wherein the secondary-electron multiplier is supplied with an operating voltage in such a way that an amplification of less than 106 secondary electrons per impinging ion results, while the output current of the secondary-electron multiplier is amplified using an electronic preamplifier mounted close to the secondary-electron multiplier with such a low noise level that the current pulses of individual ions impinging on the ion detector are detected above the noise at the input of a digitizing unit. Further disclosed are the use of the methods for imaging mass spectrometric analysis of a thin tissue section or mass spectrometric high-throughput analysis/massive-parallel analysis, and a time-of-flight mass spectrometer whose control unit is programmed to execute such methods.