Mass Spectrometer Faraday Electrode Blocking Portion
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Solution Overview
Problem
Mass spectrometers with Faraday electrodes and secondary electron multipliers face increased background noise due to vacuum ultraviolet light at higher pressures, which existing configurations fail to adequately mitigate.
Innovation Solution
A mass spectrometer design featuring a Faraday electrode with a blocking portion connected to its bottom electrode to absorb photoelectrons and reflected light, positioned to intercept these before they reach the secondary electron multiplier, along with a quadrupole filter to select ions by mass-to-charge ratio, allowing precise detection even at high pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the Faraday electrode is disposed on the axis of the mass spectrometry unit to enable direct detection of ions, then the detection sensitivity is improved, but the background noise increases due to vacuum ultraviolet light reaching the detector
Solution Approach 1:
The harmful function of vacuum ultraviolet light reaching the detector is extracted and blocked by introducing a blocking portion (light shield) between the ionization chamber and the Faraday electrode. This blocking portion specifically removes the harmful vacuum ultraviolet light while allowing ions to pass through to the detector, thereby separating the harmful radiation path from the useful ion detection path.
Solution Approach 2:
A blocking portion (light shield) is introduced as an intermediary element between the ionization chamber and the Faraday electrode. This intermediary blocks vacuum ultraviolet light from reaching the detector while allowing ions to pass through, thus mediating between the ionization source and detector to prevent harmful radiation from causing background noise.
2Object-affected harmful factors
If additional electrodes are provided on the axis to prevent direct irradiation of the Faraday electrode with vacuum ultraviolet light, then the background noise is reduced, but the vacuum ultraviolet light reflected by the additional electrode is incident on the Faraday electrode or secondary electron multiplier, making the increase of background unavoidable
Solution Approach 1:
The blocking portion is designed to not only block vacuum ultraviolet light but also to suppress reflection of vacuum ultraviolet light toward the detector. By converting the potential harmful reflection into suppressed or absorbed radiation, the blocking portion transforms a potential problem (reflected light) into a beneficial outcome (reduced background noise).
Solution Approach 2:
The blocking portion employs materials with specific optical properties that both absorb and suppress reflection of vacuum ultraviolet light. This composite approach combines multiple functional properties (blocking and anti-reflection) in a single component, effectively preventing both direct and reflected vacuum ultraviolet light from reaching the detector.
3Productivity
If the measurement is performed in a space with higher pressure to increase the amount of analyte gas available for ionization, then the ionization efficiency is improved, but more vacuum ultraviolet light is generated, causing the background to increase
Solution Approach 1:
The harmful vacuum ultraviolet light generated during high-pressure ionization is extracted and blocked by the blocking portion, allowing the system to operate at higher pressures for improved ionization efficiency without suffering from increased background noise. This enables the beneficial effect of high-pressure operation to be realized while removing the harmful byproduct.
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 configuration significantly reduces background noise and enhances precision in mass spectrometry measurements at pressures up to 1×10−2 Pa, maintaining high detection limits and precision without increasing costs or complexity.
Implementation Method 1
a large amount of vacuum ultraviolet light is generated upon ionization of an analyte gas in an ionization chamber
Implementation Method 2
a filter unit configured to allow passage of only a target ion which is a component of the analyte gas ionized in the ionization unit and which has a specific mass-to-charge ratio
Implementation Method 3
When the vacuum ultraviolet light reaches the ion detector and generates photoelectrons, the background increases in a mass spectrum
Data Source
AI summary
A mass spectrometer includes: an ionization unit configured to ionize an analyte gas; a filter unit configured to allow passage of only a target ion which is a component of the analyte gas ionized in the ionization unit and which has a specific mass-to-charge ratio; and an ion detection unit configured to detect an ion detection value based on the target ion having passed through the filter unit, wherein the ion detection unit includes a Faraday electrode which includes an electrode portion disposed along a centerline of the filter unit and a bottom electrode provided at a position downstream of the electrode portion in a flow of the target ion, the electrode portion and the bottom electrode being connected to each other, a secondary electron multiplier provided to face the electrode portion with the centerline located therebetween, and a blocking portion connected to the bottom electrode.