Method and apparatus for in-process liquid analysis by laser induced plasma spectroscopy
First Claim
1. A laser-induced plasma spectroscopy apparatus for the analysis of the composition of liquid and molten materials comprising:
- a laser emitting pulses at given repetition rate and along a given beam path;
an optical means to direct the laser pulses to a location at a surface of the liquid to generate a plasma that emits elemental radiation that corresponds to at least one compositional element of the liquid;
a probe structure, which detects the emitted elemental radiation along a detection path, said probe structure including an optical window, a spectrometer for analyzing the spectra of the emitted radiation, a detector to detect the light diffracted by the spectrometer, a data processor which determines a concentration of the predetermined element; and
a flow cell assembly which establishes a substantially steady flow of the liquid past the said location at the surface of the liquid, the flowing liquid at this location being truly representative of the liquid bulk flown into the cell, said flow sufficient to prevent said pulses from perturbing said surface at said location, said cell assembly including a controller to control the liquid surface level and the flow speed.
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Abstract
A method and apparatus for spectrochemical analysis of liquids, including molten materials, using laser-induced plasma spectroscopy. The apparatus preferably comprises a high power pulsed laser focused on the surface of a liquid stream flowing in a measurement cell, and an optical spectrometer-detector assembly, which receives, detects and analyzes the radiation emitted by the high temperature plasma thereby excited. The measurement cell, and optional pump, establish a steady flow of liquid, thereby permitting the laser to repeatedly sample a fresh unperturbed surface, representative of the liquid volume, while also ensuring that bubbles and waves formed in the liquid are removed from the focal volume. Gas (usually air) blown above the liquid prevents aerosols and matter ejected from the sample responsive to the incident energy from interacting with subsequent laser pulses, and from accumulating on the optics.
26 Citations
38 Claims
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1. A laser-induced plasma spectroscopy apparatus for the analysis of the composition of liquid and molten materials comprising:
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a laser emitting pulses at given repetition rate and along a given beam path;
an optical means to direct the laser pulses to a location at a surface of the liquid to generate a plasma that emits elemental radiation that corresponds to at least one compositional element of the liquid;
a probe structure, which detects the emitted elemental radiation along a detection path, said probe structure including an optical window, a spectrometer for analyzing the spectra of the emitted radiation, a detector to detect the light diffracted by the spectrometer, a data processor which determines a concentration of the predetermined element; and
a flow cell assembly which establishes a substantially steady flow of the liquid past the said location at the surface of the liquid, the flowing liquid at this location being truly representative of the liquid bulk flown into the cell, said flow sufficient to prevent said pulses from perturbing said surface at said location, said cell assembly including a controller to control the liquid surface level and the flow speed. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 33, 34, 37)
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18. A method of laser-induced plasma spectroscopy analysis for liquid and molten materials, comprising the steps of:
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directing laser pulses at a given repetition rate and along a given beam path onto a location at the liquid surface to generate a plasma that emits elemental radiation that corresponds to at least one compositional element of the liquid;
detecting the emitted elemental radiation along a detection path and analyzing its spectra with a spectrometer;
processing the spectra to determine a concentration of the predetermined element; and
establishing a substantially steady flow of liquid past the said location at the liquid surface, said flow sufficient to prevent said pulses from perturbing said surface at said location, the flowing liquid at this location being truly representative of the bulk of the liquid to analyze; and
controlling the liquid surface level and the flow speed. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 35, 36, 38)
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Specification