Ring-down cavity spectroscopy cell using continuous wave excitation for trace species detection
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1. An apparatus for detection and measurement of trace species in a sample gas comprising:
- a ring down cavity cell filled with said sample gas and adapted to resonate radiation, said ring down cavity cell having an optical axis;
a continuous wave laser emitting radiation;
means for directing said radiation emitted from said continuous wave laser to said ring down cavity cell;
a first photodetector measuring radiation levels resonated by said ring down cavity cell and producing a corresponding signal;
means, responsive to said signal from said first photodetector, for calculating the decay rate of said ring down cavity cell; and
means, responsive to said decay rate, for determining the level of trace species in said sample gas.
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Abstract
An apparatus for detection and measurement of trace species in a sample gas. A ring down cavity cell is filled with the sample gas. A continuous wave laser emits radiation, which is directed from the continuous wave laser to the ring down cavity cell where it resonates. A photodetector measures radiation levels resonated by the ring down cavity cell and produces a corresponding signal. The decay rate of the ring down cavity cell is calculated from the signal produced by the photodetector and is used to determine the level of trace species in the sample gas.
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26 Claims
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1. An apparatus for detection and measurement of trace species in a sample gas comprising:
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a ring down cavity cell filled with said sample gas and adapted to resonate radiation, said ring down cavity cell having an optical axis; a continuous wave laser emitting radiation; means for directing said radiation emitted from said continuous wave laser to said ring down cavity cell; a first photodetector measuring radiation levels resonated by said ring down cavity cell and producing a corresponding signal; means, responsive to said signal from said first photodetector, for calculating the decay rate of said ring down cavity cell; and means, responsive to said decay rate, for determining the level of trace species in said sample gas. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. An apparatus for detection and measurement of trace species in a sample gas comprising:
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a ring down cavity cell filled with said sample gas and adapted to resonate radiation, said ring down cavity cell having an optical axis, a front highly reflective mirror, and a rear highly reflective mirror, said mirrors aligned along said optical axis as an etalon; a narrow tube coaxial with said optical axis of said ring down cavity cell through which said sample gas flows; a single mode, tunable, continuous wave laser having a narrow band and emitting radiation; a temperature controller adapted to tune the wavelength of said laser on a predetermined spectral line wavelength of said laser on a predetermined spectral line of the trace species; means for tuning said laser to the peak of the predetermined spectral line of the trace species; means for directing said radiation emitted from said laser to said ring down cavity cell; a first photodetector measuring radiation levels resonated by said ring down cavity cell and producing a corresponding signal; means, responsive to said signal from said first photodetector, for calculating the decay rate of said ring down cavity cell; and means, responsive to said decay rate, for determining the level of trace species in said sample gas. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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Specification