Method for detecting a gas species using a super tube waveguide
First Claim
1. A method for detecting the concentration of a gas species X, comprising:
- emitting infrared radiation from a source into a sample cell comprised of a hollow waveguide with a plurality of bends that are collectively greater than 180 degrees in three dimensions, said infrared radiation being quasi-focused into a beam with an angle of incidence between greater than approximately 0° and
approximately 10°
relative to a longitudinal axis of a first linear segment of the sample cell proximate the source;
detecting a first signal at a first detector located in a detector chamber of the waveguide;
detecting a second signal at a second detector located in the detector chamber; and
using the second signal to adjust the first signal for detecting the concentration of the gas species X;
wherein one of the first and second signals is based upon a first absorption band for gas species X while the other of said signals is based upon a second absorption band chosen to detect water which does not coincide with any known absorption bands of gases in the sample cell.
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Abstract
A method for detecting the concentration of one or more gas species by using infrared radiation emitted from one or more sources into a sample cell which is a hollow waveguide with multiple bends collectively greater than 180 degrees in three dimensions, the infrared radiation being quasi-focused into a beam with an angle of incidence between greater than approximately 0° and approximately 10° relative to a longitudinal axis of a first linear segment of the sample cell proximate the source, then detecting two or more signals in which one of the signals is used to compensate for water vapor. The methods can detect gas concentrations down to 1 ppm or less.
20 Citations
20 Claims
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1. A method for detecting the concentration of a gas species X, comprising:
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emitting infrared radiation from a source into a sample cell comprised of a hollow waveguide with a plurality of bends that are collectively greater than 180 degrees in three dimensions, said infrared radiation being quasi-focused into a beam with an angle of incidence between greater than approximately 0° and
approximately 10°
relative to a longitudinal axis of a first linear segment of the sample cell proximate the source;
detecting a first signal at a first detector located in a detector chamber of the waveguide;
detecting a second signal at a second detector located in the detector chamber; and
using the second signal to adjust the first signal for detecting the concentration of the gas species X;
wherein one of the first and second signals is based upon a first absorption band for gas species X while the other of said signals is based upon a second absorption band chosen to detect water which does not coincide with any known absorption bands of gases in the sample cell. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method for detecting a concentration of a gas species X which is less than 100 ppm, comprising:
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emitting infrared radiation from a source into a sample cell comprised of a hollow waveguide with a plurality of bends that are collectively greater than 360 degrees in three dimensions, said infrared radiation being quasi-focused into a beam with an angle of incidence between greater than approximately 0° and
approximately 10°
relative to a longitudinal axis of a first linear segment of the sample cell proximate the source;
focusing said infrared radiation after it has traveled through substantially all of the waveguide and as it approaches the first detector;
detecting a first signal at a first detector located in a detector chamber of the waveguide;
detecting a second signal at a second detector located in the detector chamber; and
using the second signal to adjust the first signal for detecting the concentration of the gas species X;
wherein one of the first and second detectors are offset relative to the other of said detectors in the detector chamber; and
wherein one of the first and second signals is based upon a first absorption band for gas species X while the other of said signals is based upon a second absorption band chosen to detect water which does not coincide with any known absorption bands of gases in the sample cell. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification