Glow Plasma Signal Processing for Stable Atmospheric Gas Measurement
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Solution Overview
Problem
Conventional glow discharge optical emission spectroscopy systems face challenges in accurately processing signals from glow plasmas at atmospheric pressure, leading to instability and inefficiencies in gas analysis, particularly in maintaining stable plasma conditions and achieving high signal-to-noise ratios.
Innovation Solution
The method involves generating oscillating electromagnetic fields within a plasma cell to produce a stable glow discharge plasma, monitoring optical emissions at twice the excitation frequency, and using dynamic resonant feedback control to maintain desired operating conditions, thereby enhancing signal processing and stability for real-time gas analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional glow discharge optical emission spectroscopy systems are used for gas analysis at atmospheric pressure, then the system can operate at atmospheric pressure conditions, but the signal-to-noise ratio is poor and plasma stability is difficult to maintain
Solution Approach 1:
The patent applies periodic modulation of the plasma excitation at a specific frequency, and detects the emitted light at twice this frequency. This periodic action creates a stable reference signal that can be distinguished from background noise, thereby improving both plasma stability and signal-to-noise ratio simultaneously
Solution Approach 2:
The system implements feedback control by monitoring the optical emissions and using this information to adjust and maintain stable plasma conditions. The detected signal at twice the excitation frequency provides feedback about plasma state, enabling active stabilization of the discharge
2Reliability
If low-pressure glow discharge is used to improve signal stability, then plasma stability improves, but the system complexity and cost increase due to vacuum requirements
Solution Approach 1:
The patent changes the operating pressure parameter from low-pressure to atmospheric pressure conditions. By combining this parameter change with frequency-domain detection (measuring at twice the excitation frequency), the system achieves signal stability without requiring complex vacuum systems, thereby reducing device complexity while maintaining reliability
3Adaptability or versatility
If atmospheric pressure glow discharge is used for gas analysis, then the application scope is expanded, but the plasma becomes less stable and harder to control
Solution Approach 1:
By implementing periodic modulation of the excitation source and detecting at twice this frequency, the system creates a stable reference signal that enables reliable atmospheric pressure operation. This allows the system to maintain plasma stability while operating at atmospheric pressure, thereby expanding application scope without sacrificing 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 improves signal-to-noise ratios and maintains stable glow discharge optical emissions, enabling more accurate and efficient gas analysis across a wide range of conditions, including atmospheric pressure, by actively controlling plasma excitation and monitoring emissions in real-time.
Implementation Method 1
generating one or more oscillating electromagnetic fields within a plasma cell to excite particles within the cell, to produce a glow discharge plasma in the plasma cell
Implementation Method 2
The subsequent radiative decay to lower energy levels results in the emission of characteristic photons of radiation that gives the name of 'glow' discharge
Data Source
AI summary
Methods and apparatus for determination of the gas composition of a sample gas using glow discharge optical emission spectroscopy, in which the method comprises: generating one or more oscillating electromagnetic fields within a plasma cell to excite particles within the cell, to produce a glow discharge plasma in the plasma cell, and controlling the operating conditions for the plasma cell while flowing a gas mixture through the plasma cell to maintain glow discharge optical emissions from the plasma within a desired operating range; and monitoring one or more glow discharge optical emissions from the plasma in the plasma cell by measuring the optical emissions, or measuring a signal that correlates with the optical emissions, at twice the plasma excitation frequency; and processing the signal during each excitation cycle of the electromagnetic excitation, to determine the concentration of a gas within a gas mixture flowing through the plasma cell.