Ion Detector Lead-in Electrode Stray Light Reduction
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Solution Overview
Problem
Mass spectrometers face challenges in achieving a high signal-to-noise ratio due to stray light interference, which affects the detection of mass-selected ions and limits the sensitivity of the instrument.
Innovation Solution
An ion detector design incorporating a lead-in electrode with a specific area and potential difference configuration is used to minimize the impact of internal stray light, ensuring that the amount of internal stray light entering the first-stage electrode is equivalent to or less than the external stray light, thereby improving the ion pull-in effect and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the amplification factor of the secondary electron multiplier is increased to improve signal detection, then the signal amplification is enhanced, but the noise from stray light is also amplified equally, resulting in no improvement in signal-to-noise ratio
Solution Approach 1:
The ion detection path is segmented into multiple regions with different electric field strengths. The lead-in electrode creates a strong electric field region near the first-stage electrode D1, while other regions have weaker fields. This segmentation allows preferential acceleration of ions over photoelectrons, improving signal-to-noise ratio without increasing overall amplification.
Solution Approach 2:
Different regions of the detection space are given different electric field characteristics. The region near the first-stage electrode D1 has a strong electric field (high local quality) to attract ions, while other regions have weaker fields that don't accelerate photoelectrons generated by stray light. This local differentiation allows selective enhancement of signal while suppressing noise.
2Measurement precision
If a lead-in electrode is added to improve ion pull-in effect, then ion detection efficiency is enhanced, but the device complexity increases
Solution Approach 1:
The lead-in electrode serves multiple functions simultaneously: it creates the strong electric field for ion pull-in near D1, defines the detection region boundaries, and works in conjunction with existing deflection boards to guide ions. This multi-functionality reduces the need for separate components, minimizing the increase in device complexity.
3Measurement precision
If the area of the lead-in electrode is increased to enhance ion attraction, then the ion pull-in effect is improved, but the amount of internal stray light entering the first-stage electrode increases
Solution Approach 1:
The electric field strength parameter is varied spatially across the detection region. By adjusting the voltage on the lead-in electrode and its positioning, a strong electric field is created only in the critical region near D1 where ion attraction is needed, while other regions maintain weaker fields that minimize stray light effects. This parameter optimization balances ion pull-in effect with stray light reduction.
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 enhances the signal-to-noise ratio by effectively reducing the influence of internal stray light, allowing for more accurate detection of ions and improving the overall performance of the mass spectrometer.
Implementation Method 1
A lead-in electrode for pulling in ions to a first-stage electrode side of a secondary electron multiplier by an electric field
Implementation Method 2
When 2 kV is applied to the electrode D1, a collisional energy is approximately 2 keV, and, when the energy is at such level, electrons (secondary electrons) are generated on the surface of the electrode D1. That is, on the electrode D1, ion/electron conversion is performed.
Implementation Method 3
The electron generated from the electrode D1 is pulled in the second stage electrode (D2) having a potential higher (in the plus direction) by around 100 V than that of the electrode D1, and collides with an energy of around 100 eV corresponding to the potential difference. The yield of the generation of secondary electrons by an electron collision is very high, and, in the energy at such level, is around 1.5 to 2.0 in an appropriate surface state. Accordingly, the amplification of the electron is realized here.
Data Source
AI summary
The present disclosure provides an ion detector for improving the effect of electric field for pulling in an ion to be detected to a first-stage electrode of a secondary electron multiplier (SEM), and improving the effect of a stray light reduction. In one example embodiment, an ion detector includes a SEM, and a lead-in electrode for pulling in an ion to a first-stage electrode side of the SEM. At least one of the area of the lead-in electrode and a potential difference between the lead-in electrode and neighboring electrodes of the lead-in electrode, the neighboring electrode being an electrode not of the SEM, is set so that the light amount of internal-stray light generated inside the detector entering the first-stage electrode is not more than that of external-stray light generated outside the detector entering the first-stage electrode, when an ion is introduced into the detector.