Multi-mode plasma-based optical emission gas detector
AssigneeMecanique Analytique Inc.
InventorYves Gamache
Life of this patent
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Abstract
A plasma-based detector using optical spectroscopic techniques for analyzing the constituents of gas samples are provided. The detector includes a plasma-generating mechanism and a plasma-localizing mechanism. Electron-injecting electrodes may be provided in the plasma chamber of the detector. A Pressure control mechanism as well as a doping module may optionally be included. In accordance with some implementations, the collection, detection and analysis of light extracted from the plasma may enable one or more of various operation modes, such as an emission mode, an absorption mode, and indirect detection mode or a constant emission mode.
Claims63
A plasma-based optical emission gas detector, comprising:
- a plasma chamber traversed by a gas flow path allowing a flow of a gas sample through the plasma chamber;
- a plasma-generating mechanism configured to apply a plasma-generating field across the plasma chamber intersecting the gas flow path so as to generate a plasma from said gas sample;
- at least one optical window allowing optical emissions from said plasma to exit the plasma chamber therethrough;
- and
- a plasma-localizing mechanism configured to apply a plasma-localizing field across the plasma chamber and positioned such that the plasma-localizing field localizes the plasma within the plasma chamber in alignment with the at least one optical window.
A plasma-based gas detector, comprising:
- a plasma chamber traversed by a gas flow path allowing a flow of a gas sample through said plasma chamber;
- a plasma-generating mechanism configured to apply a plasma-generating field across the plasma chamber, the plasma-generating field intersecting the gas flow path so as to generate a plasma from said gas sample, the plasma occupying a plasma region within the plasma chamber;
- and
- a pair of electron-injecting electrodes, each electrode of said pair having an extremity projecting within the plasma region.
A method for generating a plasma in a plasma chamber of a plasma-based gas detector, the method comprising:
- a) circulating a flow of a gas sample through the plasma chamber;
- b) controlling a pressure inside the plasma chamber to a sub-atmospheric level;
- c) applying a plasma-generating field across the plasma chamber intersecting the flow of gas sample so as to generate a plasma from the gas sample;
- d) putting respective extremities of a pair of electron-injecting electrodes in contact with the plasma;
- and
- e) applying a voltage on the electron-injecting electrode such that free electrons are injected within the plasma chamber.
A method of detecting a gas species in a gas sample, comprising:
- a) providing a plasma-based optical emission gas detector comprising a plasma chamber and a pressure control mechanism operable to control a pressure in the plasma chamber over a continuous pressure range;
- b) selecting a pressure setting based on at least one sample characteristic associated with the gas sample;
- c) circulating a flow of the gas sample through the plasma chamber;
- d) generating a plasma from the gas sample in the plasma chamber;
- e) controlling the pressure control mechanism to maintain the pressure in the plasma chamber at the selected pressure setting;
- and
- f) measuring optical emissions from the plasma indicative of presence of the gas species.
A method of measuring a gas species in a gas sample, comprising:
- a) providing a plasma-based optical emission gas detector comprising a plasma chamber and a plasma-generating mechanism comprising a pair of discharge electrodes and an alternating current generator providing an alternating discharge driving signal to the discharge electrodes at an adjustable frequency;
- b) circulating the gas sample through the plasma chamber;
- c) generating a plasma from the carrier gas in the plasma chamber using the plasma-generating mechanism;
- d) continuously measuring an optical emission from the plasma and adjusting the frequency of the discharge driving signal in real time to maintain the measured optical emission constant;
- e) introducing time-separated peaks of said impurities in the flow of carrier gas;
- and
- f) monitoring the frequency of the discharge driving signal and detecting the gas species through variations in said frequency.
A method of measuring a gas species in a gas sample, comprising:
- providing a plasma-based optical emission gas detector comprising a plasma chamber and a plasma-generating mechanism configured to apply a plasma-generating field across the plasma chamber;
- circulating the gas sample through the plasma chamber;
- generating a plasma from the gas sample in the plasma chamber using the plasma-generating mechanism;
- doping the gas sample in the plasma chamber with at least one dopant interacting with said gas species within the plasma;
- and
- measuring optical emissions affected by said interacting of the at least one dopant with the gas species.
A plasma doping module for a plasma-based optical emission gas detector comprising a plasma chamber traversed by a gas flow path allowing a flow of a gas sample through the plasma chamber, the plasma doping module comprising:
- an injection tubing connected to the plasma chamber and carrying said flow of the gas sample to the plasma chamber;
- an electrically conductive tube extending within the injection tubing, the electrically conductive tube having an inlet projecting out of the injection tubing and connectable to a dopant source to receive a flow of dopant gas therefrom, and an outlet projecting within the plasma chamber to output said flow of dopant gas into said plasma chamber;
- a pre-ionisation electrode in contact with the injection tubing coextensively with the flow of dopant gas;
- and
- a pre-ionisation voltage source connected to the electrically conductive tube and to the pre-ionisation electrode to apply a voltage therebetween, thereby pre-ionising the flow of dopant gas.
Dependencies are inferred from the claim text.