Gas Analysis System with Segmented Plasma Source
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Solution Overview
Problem
Current gas analysis systems using optical emission spectroscopy are limited to pressures above 10^-3 mbar and cannot perform real-time, reproducible analysis of gaseous species in secondary vacuum conditions due to insufficient light generation and rapid pollution of optical components.
Innovation Solution
A gas analysis system with a plasma source comprising a cylindrical volume and a perforated cathode disc, where the anode is centered within the central hole of the disc, and a magnetic field is used to enhance plasma excitation, combined with a converging lens system and a regulation device to adjust the anode supply voltage based on pressure, minimizing pollution and optimizing light collection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If optical emission spectroscopy is used to analyze gases in secondary vacuum conditions, then real-time analysis capability is improved, but optical components are rapidly polluted and light generation becomes insufficient
Solution Approach 1:
The device divides the vacuum chamber into distinct zones: a plasma generation zone with perforated cathode and anode, and a separate analysis zone with optical components. This spatial segmentation allows the plasma to be generated in one area while optical components remain in a cleaner area, reducing pollution while maintaining real-time analysis capability
Solution Approach 2:
The patent introduces a magnetic field as an intermediary to enhance plasma excitation and light generation efficiency. By using magnetic fields to confine and energize the plasma, sufficient light is produced for analysis without requiring the optical components to be directly exposed to the harsh plasma environment, thus reducing pollution
2Illumination intensity
If plasma intensity is increased to improve light generation for analysis, then measurement capability is improved, but contamination of the system increases
Solution Approach 1:
The device segments the plasma generation function from the optical detection function by using a perforated cathode structure that confines plasma to specific regions. This allows high plasma intensity to be maintained in the generation zone for sufficient light emission, while the optical components in the analysis zone remain protected from direct contamination
Solution Approach 2:
A magnetic field is introduced as an intermediary to enhance plasma excitation efficiency. This allows the plasma to generate sufficient light intensity for analysis without requiring excessive plasma density that would lead to increased contamination, as the magnetic field optimizes the energy utilization of the plasma
3Adaptability or versatility
If conventional plasma sources are used in rough or primary vacuum, then analysis can be performed, but the system cannot operate in secondary vacuum conditions below 10^-3 mbar
Solution Approach 1:
The patent modifies the plasma source parameters by using a perforated cathode structure with specific geometry and applying optimized voltage and magnetic field parameters. These parameter changes enable the plasma source to maintain stable operation and reliable analysis capability across a broad pressure range from rough vacuum down to secondary vacuum conditions below 10^-3 mbar
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
Enables real-time analysis of gaseous species in secondary vacuum conditions (10^-3 to 10^-8 mbar) with improved light intensity and focus, reducing contamination and extending system lifespan by maintaining optimal plasma intensity and reducing optical component pollution.
Implementation Method 1
An optical emission spectrometer, after light diffraction, analyzes in real time the evolution of the radiation emitted by the atoms, molecules and ions, excited by the free electrons of the plasma
Implementation Method 2
a magnetic field is used to enhance plasma excitation
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The invention relates to a system for analysing gases (2) under pressure of the order of secondary vacuum. The system includes a gas ionisation device (4) that comprises a cathode (14) having conducting walls (12) defining a cylindrical volume (11) and a disc (15) including at least one central through hole (31), an anode (13) placed substantially at the centre of the hole (31), a plasma source, the plasma being generated in the cylindrical volume by the combined action of an electric field E (17) and a magnetic field B (19) orthogonal to the electric field E (17), a system (5) for collecting the light radiation emitted by the plasma, a cylindrical cavity (23) coaxial to the anode (13) having a conductance lower than that of the cylindrical volume (11) and arranged between the ionisation device (5) and the collector system (5), and an analysis device (6) for the ionised gases including an optical spectrometer (41) for analysing the evolution of the radiating spectrum. Preferably, the end of the cavity (23) opposite the cylindrical volume (11) is closed by a hatch (21) that is transparent to the light radiation emitted by the plasma.