Mass Spectrometer Ion Source Thermal Electron Confinement
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Solution Overview
Problem
The parallel filament arrangement structure in mass spectrometers offers high sensitivity but lacks measurement stability, leading to ionic intensity drift and poor reproducibility, whereas the orthogonal structure balances sensitivity and stability but falls short on detection sensitivity.
Innovation Solution
A mass spectrometer design with an ion source featuring an ionization chamber, repeller electrode, filament, trap electrode, and magnetic field control, where specific distances between port ends and chamber walls are set to minimize thermal electron and ion contact with internal surfaces, enhancing stability while maintaining high sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a parallel filament arrangement structure is used, then detection sensitivity is improved, but measurement stability deteriorates with ionic intensity drift
Solution Approach 1:
The patent changes the geometric parameters of the ionization chamber by setting specific distances (first distance and second distance) between the electron introduction port and chamber walls to be larger than the thermal electron radius of gyration. This parameter optimization allows the parallel filament arrangement to maintain both high detection sensitivity and improved measurement stability by preventing electron-wall collisions that cause instability.
2Device complexity
If the electron introduction port is positioned closer to chamber walls, then device complexity is reduced, but thermal electron contact with internal surfaces increases causing contamination
Solution Approach 1:
The patent addresses the contamination issue by considering the three-dimensional trajectory of thermal electrons through the ionization chamber. By setting the electron introduction port at a specific distance from the chamber walls (greater than the radius of gyration), the patent ensures that electrons traveling in curved paths due to magnetic field effects do not collide with the walls, thus preventing contamination while maintaining a relatively simple device structure.
3Manufacturing precision
If distances between port ends and chamber walls are reduced, then manufacturing precision requirements are lowered, but electric field stability deteriorates
Solution Approach 1:
The patent optimizes the geometric parameters of the ionization chamber by establishing specific distance requirements between the electron introduction port and chamber walls. These parameter settings (first distance and second distance both greater than the thermal electron radius of gyration) create a stable electric field environment that is less sensitive to manufacturing variations, thereby improving electric field stability without excessively stringent manufacturing precision requirements.
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 reduces contamination and stabilizes the electric field, improving measurement stability and detection sensitivity, allowing for the identification and quantification of small compound amounts in gas chromatograph mass spectrometry.
Implementation Method 1
the filament 11 is energized to generate heat and generate thermal electrons
Implementation Method 2
A direct current voltage having a predetermined potential difference is applied between the filament 11 and the opposing filament 12, and the generated thermal electrons are accelerated by the potential difference
Implementation Method 3
The focusing magnets 13 form a magnetic field in which the magnetic flux lines run in the Y-axis direction, and the broadening of the thermal electron flow 16 in the X-axis and Z-axis directions is suppressed by the magnetic field
Implementation Method 4
A direct current voltage V1 having the same polarity as that of the ions derived from the sample is applied to the repeller electrode 14. As a result, an extrusion electric field having a force to push the ions in a direction away from the repeller electrode 14 is formed
Implementation Method 5
an extraction electric field formed by the voltage applied to the extraction electrodes of the ion lens 2 intrudes into the ionization chamber 10 through the ion ejection hole 101. Ions are extracted from the ionization chamber 10 in the X-axis direction by the actions of both the extrusion electric field and the extraction electric field
Implementation Method 6
A sample component (compound) in the sample gas supplied into the ionization chamber 10 through the sample gas introduction pipe 15 comes into contact with the thermal electrons and is ionized
Data Source
AI summary
A mass spectrometer includes an ion source including: an ionization chamber including an ion ejection hole, and an electron introduction port and an electron discharge port; a repeller electrode; a filament; a trap electrode; and a magnetic field forming unit. A first distance in a direction along the ion optical axis between an end of the electron introduction port on an ion ejection hole side and an inner face of a wall of the ionization chamber in which the ion ejection hole is formed and/or a second distance in a direction along the ion optical axis between an end of the electron introduction port on a repeller electrode side and the repeller electrode, is set to be larger than a radius of gyration of the thermal electron estimated based on energy imparted to the thermal electron and intensity of the magnetic field formed by the magnetic field forming unit.