LIBS Plasma Self-Calibration via Iterative Spectral Matching
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Solution Overview
Problem
Current LIBS techniques require prior calibration and assume a plasma is optically thin and uniform, leading to inaccuracies due to self-absorption and spatial non-uniformity, and cannot provide real-time measurements.
Innovation Solution
A method that calculates the absorption coefficient and spectral luminance using analytical solutions, iteratively adjusting plasma parameters to accurately determine elemental composition without prior calibration, considering the plasma's non-uniformity and temperature gradients by dividing it into multiple zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If prior calibration is used to determine elemental composition, then measurement accuracy is improved, but experimental constraints increase and the number of calibration curves required becomes excessive
Solution Approach 1:
The method uses the plasma itself to provide the calibration information needed. By measuring the intensity ratio of two spectral lines from the same element and using the known relationship between line intensity and atomic concentration, the system performs self-calibration without requiring external reference samples or complex calibration curves
Solution Approach 2:
The method changes the measurement approach from requiring multiple calibration curves for different elements to using a single ratio measurement approach. By measuring the intensity ratio of two spectral lines and applying the calibration-free method based on plasma parameters, the system eliminates the need for extensive calibration data
2Ease of manufacture
If the plasma is assumed to be optically thin and uniform, then calculation simplicity is improved, but measurement accuracy deteriorates due to self-absorption and spatial non-uniformity
Solution Approach 1:
The method changes the plasma model from optically thin to optically thick by incorporating the self-absorption coefficient into the calculations. This parameter change allows the system to account for self-absorption effects while maintaining a relatively simple calculation framework based on modified plasma radiation equations
Solution Approach 2:
The method accounts for spatial non-uniformity by considering that different regions of the plasma have different properties. The calculation incorporates the effects of plasma inhomogeneity through the use of appropriate radiation transfer equations that consider the spatial distribution of plasma parameters
3Measurement precision
If iterative calculation of absorption coefficient and spectral luminance is performed, then measurement accuracy is improved, but calculation time increases
Solution Approach 1:
The method performs iterative calculations only when necessary to achieve the desired accuracy. By using initial estimates of plasma parameters and performing iterations only to the extent needed to converge to acceptable accuracy, the system balances measurement precision with calculation time efficiency
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 precise and rapid concentration measurements by iteratively matching calculated and measured spectra, overcoming the limitations of prior calibration and plasma assumptions, allowing for real-time analysis.
Implementation Method 1
focusing a pulsed laser beam onto the surface of a sample of solid, liquid (or gaseous) materials to vaporize the matter and transform it into a plasma
Implementation Method 2
The plasma's emission spectrum is then analyzed to determine its chemical composition
Implementation Method 3
laser-induced plasma spectroscopy (LIBS, or 'Laser-Induced Breakdown Spectroscopy' in English)
Implementation Method 4
calculating the plasma absorption coefficient to account for the fact that the plasma is not optically thin
Data Source
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AI summary
A system and method for measuring elemental concentrations of a material from a sample containing several elements by LIES analysis is provided. The material is heated to generate plasma and its chemical composition is determined from spectral analysis of its radiation. The spectral lines of interest are identified among those emitted by constituents of each element composing sample, and their intensities are measured. The chemical composition of the plasma is calculated. The absorption coefficient according to wavelength is calculated for the spectral zones of the lines of interest. The spectral radiance of the plasma is calculated for the same spectral zones and then a comparison of the intensity and shape of the spectrum thus calculated with those of the spectrum measured is performed. These calculations and this comparison are repeated iteratively in order to adjust the temperature, electron density, relative values of the elemental concentrations and width of the plasma.