Local Argon Purge for LIBS Elemental Analysis
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Solution Overview
Problem
Portable and benchtop XRF analyzers are unable to accurately determine lower atomic number elements like beryllium, sodium, carbon, boron, oxygen, nitrogen, and lithium, and face challenges with elements that react with oxygen, resulting in low signal detection, while LIBS devices require high argon gas usage and pose safety concerns with X-ray-based instruments.
Innovation Solution
A portable, battery-powered LIBS device using an eye-safe laser with a focusing mechanism to precisely target samples, a local argon purge system for gas conservation, and automated focusing and cleaning cycles to ensure accurate analysis of heterogeneous samples with reduced gas consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high powered laser is used to produce plasma for LIBS analysis, then the ability to detect lower atomic number elements is improved, but operator safety deteriorates due to eye safety concerns
Solution Approach 1:
The patent changes the wavelength parameter of the laser to 1.5 micrometers, which is absorbed by water in the cornea and cannot reach the retina, making it eye-safe while maintaining sufficient power density for plasma generation and LIBS analysis of lower atomic number elements
2Power
If the laser beam spot size is reduced to 100 micrometers or less to achieve sufficient power density, then the ability to generate plasma with lower power lasers is improved, but measurement precision deteriorates due to sample heterogeneity and surface contamination
Solution Approach 1:
The patent implements preliminary laser cleaning cycles before analytical measurements to remove surface contamination and oxidation from the sample, ensuring that the small 100 micrometer or smaller beam spot analyzes clean, representative sample material and improving analytical consistency
Solution Approach 2:
The patent uses periodic laser pulses in sequences that alternate between cleaning cycles and analytical measurement cycles, allowing the sample surface to be repeatedly cleaned and analyzed to ensure representative measurements despite the small beam spot size
3Measurement precision
If a large flow rate of argon gas is used to purge the sample, then the detection of elements that react with oxygen is improved, but gas consumption deteriorates requiring large portable tanks
Solution Approach 1:
The patent implements a local purge system where argon gas is delivered only to the immediate analysis region through a nozzle positioned near the laser focal point, creating a localized inert atmosphere that protects the plasma from oxygen contamination while using minimal gas quantities suitable for portable operation
Solution Approach 2:
The patent extracts only the essential function of oxygen exclusion from the sample region, using a targeted local purge rather than a large-scale atmospheric replacement, thereby achieving adequate protection for oxygen-reactive element detection with minimal argon consumption
4Ease of operation
If X-ray tubes are used for elemental analysis, then the ease of operation is improved with established technology, but harmful factors worsen due to radiation safety concerns
Solution Approach 1:
The patent replaces the X-ray tube mechanical and electrical system with a laser-based optical system that generates plasma for LIBS analysis, eliminating ionizing radiation hazards while maintaining elemental analysis capability through optical emission spectroscopy
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
The device achieves accurate elemental analysis of lower atomic number elements with reduced argon gas usage and enhanced operator safety, providing consistent and repeatable results while conserving battery power and minimizing sample inhomogeneity issues.
Implementation Method 1
These devices typically include a high powered laser that sufficiently heats a portion of the sample to produce a plasma
Implementation Method 2
As the plasma cools, eventually the electrons return to their ground states. In the process, photons are emitted at wavelengths unique to the specific elements comprising the sample
Implementation Method 3
It is known to use an inert gas such as argon to purge the sample
Implementation Method 4
it is often necessary to focus the laser into a smaller spot size, typically 100 μm or less in order to get a high enough power density to ignite a plasma
Data Source
AI summary
An analysis system includes a laser source generating a laser beam for creating a plasma at a location on a sample. A spectrometer is responsive to photons emitted by the sample at said location and has an output. At least one nozzle is configured to deliver inert gas from a source locally to the location on the sample. A controller is responsive to a trigger signal and is configured to activate the laser source generating a series of laser pulses, open a valve to purge the location locally on the sample, and close the valve after one or more laser pulses.