LIBS Quantitative Analysis via Iterated Plasma Fitting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current LIBS techniques require prior calibration for each element, assume optically thin and homogeneous plasmas, and fail to accurately account for self-absorption and inhomogeneities, leading to imprecise elemental concentration measurements.
Innovation Solution
The method introduces a new functional relationship (curve Cσ) between line intensity and concentration, using iterated fitting with radiative transfer models to account for inhomogeneous plasmas and eliminate invalid data, allowing for calibration-free elemental analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If prior calibration with reference samples is performed for each element, then measurement precision is improved, but device complexity and time consumption increase due to requiring multiple calibration samples and procedures
Solution Approach 1:
The method enables the LIBS system to perform self-calibration by using the plasma spectrum itself to determine calibration parameters. The system automatically calculates the calibration curve from the measured spectrum without requiring external reference samples, making the system self-sufficient and eliminating complex external calibration equipment
Solution Approach 2:
The patent introduces an artificial calibration line as an intermediary element with known concentration and spectral characteristics. This artificial line serves as a reference marker within the plasma spectrum, enabling calibration without requiring external reference samples for each element being analyzed
2Ease of manufacture
If the optically thin plasma hypothesis is assumed, then calculation simplicity is improved, but measurement precision deteriorates due to self-absorption effects in high-density plasmas
Solution Approach 1:
The method changes the approach from assuming optically thin plasma to calculating the optical depth parameter τ for each spectral line. By computing τ using the measured intensity, atomic data, and plasma parameters, the system adapts the calculation model based on the actual optical depth condition, maintaining precision whether the plasma is optically thin or thick
Solution Approach 2:
The patent implements a feedback mechanism where the measured spectral line intensity is used to calculate the optical depth, which then feeds back into the concentration calculation. The system iteratively adjusts the concentration values based on the optical depth feedback, ensuring accurate results even when self-absorption occurs in high-density plasmas
3Ease of operation
If homogeneous plasma with single temperature is assumed, then measurement simplicity is improved, but measurement precision deteriorates due to plasma inhomogeneity and temperature gradients
Solution Approach 1:
The patent segments the plasma into multiple zones along the line of sight, each with its own temperature and electron density parameters. By dividing the inhomogeneous plasma into discrete regions, the system can account for temperature gradients and density variations, improving measurement precision while maintaining computational feasibility
Solution Approach 2:
The method applies local quality by assigning different temperature and density parameters to different spatial zones within the plasma. Each zone is characterized by its own local conditions, allowing the system to accurately represent the inhomogeneous nature of the plasma and improve concentration measurements for elements emitting from different regions
4Measurement precision
If intense spectral lines are used for better precision, then measurement precision is improved, but reliability deteriorates due to high self-absorption in high-density plasma
Solution Approach 1:
The patent implements a dynamic selection approach where the system evaluates the optical depth of each spectral line and adapts the measurement strategy accordingly. For lines with high optical depth indicating strong self-absorption, the system automatically selects alternative lines or adjusts the calculation model, ensuring reliable measurements across varying plasma density conditions
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 provides precise elemental concentration measurements without prior calibration, accurately handling inhomogeneous plasmas and self-absorption, improving the accuracy and reliability of LIBS analysis.
Implementation Method 1
The LIBS technique is based on generating a plasma by focusing a pulsed laser beam on a material
Implementation Method 2
The radiation emitted by the plasma is detected by the LIBS system, a spectrum containing a continuum emission as well as the spectral lines
Data Source
AI summary
The quantitative analysis method for analyzing the composition of materials of the invention is based on a functional relationship (curve Cσ) between line intensity and the concentration of the element in the material. The method comprises: obtaining characteristic parameters, selecting the spectral lines of neutral atoms and ions of the elements of interest, obtaining their atomic data; calculating, for the selected lines, a line crosssection; measuring line intensities; determining the concentrations of the elements of interest by means of fitting two graphs Cσ, one for neutral atoms and another for ions with a unit charge, the fitting being performed by means of an iterative algorithm which compares the experimental graphs with the curves Cσ calculated with a plasma model; calculating, for the data of the graphs Cσ, the product of line optical depth by Lorentzian width; evaluating, for the data of the graphs Cσ, a condition on the validity limit of the model, the datum for which the mentioned product is greater being eliminated if the condition is not complied with; repeating the three preceding steps until all data comply with the mentioned condition. The invention has the advantage of not requiring prior calibrations.