Laser-Induced Plasma Absorption Spectroscopy for Real-Time Ore Classification
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Solution Overview
Problem
Current methods for real-time classification of materials, such as ores on a conveyor, are inefficient and costly, as they fail to accurately determine the quantitative composition of moving materials without complex calibration and precise timing of laser pulses.
Innovation Solution
A system utilizing a laser pulse generator to produce first and second pulses separated by up to 10 microseconds, with an absorption detector sensing the absorption spectrum within 20 nanoseconds, and a real-time rangefinder for adjusting focus, enabling precise classification of materials in motion without calibration, using the difference in plasma plume diameters to calculate concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional laser-induced breakdown spectroscopy (LIBS) is used for quantitative analysis, then emission spectra can be obtained, but calibration is required and measurement precision deteriorates due to plasma conditions variability
Solution Approach 1:
The patent uses the first laser pulse as an intermediary to create a plasma plume that serves as a controlled absorption medium for the second laser pulse. This intermediary plasma plume enables direct quantitative measurement of atomic species concentration without requiring external calibration, as the absorption depth directly correlates to concentration through the known plasma conditions created by the first pulse.
Solution Approach 2:
The patent changes the temporal parameter by separating two laser pulses in time (first pulse creates plasma, second pulse measures absorption after a controlled delay). This time-based parameter change allows the plasma to reach a stable, controllable state before measurement, eliminating the need for calibration while maintaining high measurement precision.
2Productivity
If laser pulses are used for real-time classification of moving materials, then productivity is improved, but measurement precision deteriorates due to difficulty in timing and material motion
Solution Approach 1:
The patent employs periodic pulsed laser action where the first laser pulse continuously ablates material to create a plasma plume, and the second laser pulse periodically measures absorption at controlled intervals. This periodic action enables real-time analysis of moving materials while maintaining measurement precision through consistent, repeatable measurement cycles.
Solution Approach 2:
The first laser pulse performs preliminary action by creating and stabilizing the plasma plume before the second measurement pulse arrives. This preliminary plasma creation ensures that when the second pulse measures absorption, the plasma is in a known, stable state, enabling precise quantitative analysis even for moving materials.
3Measurement precision
If absorption spectroscopy is performed on expanding plasma plume, then quantitative analysis is possible, but reliability deteriorates due to rapid plasma expansion and cooling
Solution Approach 1:
The plasma plume created by the first laser pulse serves itself as the absorption medium for the second laser pulse. The plasma's own atomic species absorb at characteristic wavelengths, providing self-referential quantitative measurement. This self-service mechanism ensures reliability because the measurement uses the plasma's inherent properties rather than requiring external reference standards.
Solution Approach 2:
The system uses feedback by measuring the absorption of the second laser pulse through the plasma plume created by the first pulse. The absorption depth provides immediate feedback on the concentration of atomic species in the plasma, allowing for reliable, real-time quantitative analysis that accounts for plasma 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
Enables highly efficient and cost-effective real-time classification of materials by directly determining the quantitative composition of moving materials, allowing for immediate decision-making on processing or discarding based on predetermined thresholds, with a linear relationship between absorption spectrum and concentration.
Implementation Method 1
a first laser pulse is used to create a plasma plume
Implementation Method 2
a second laser pulse is used to induce absorption by atoms in the plasma plume
Implementation Method 3
an absorption detector is used to sense an absorption spectrum of the second laser pulse
Data Source
AI summary
A system for classifying moving materials in real time, the system including a laser pulse generator operative to generate at least first and second laser pulses which impinge on the same impingement location on the moving materials, the first and second laser pulses being separated in time by up to 10 microseconds; and an absorption detector operative to sense an absorption spectrum at the impingement location over a detection time duration of up to 20 nanoseconds following the second laser pulse.