Patent ID: 7372573

Claim:
An apparatus capable of measuring a trace gas, comprising: a source of a first beam of radiation; an interferometer receiving the first beam of radiation from the source and forming a second beam of radiation comprising an interference signal; a sample cell in optical communication with the interferometer, the sample cell comprising: a concave reflective field surface at a first end of the sample cell; and a substantially spherical, concave reflective objective surface at a second end of the sample cell in a confronting relationship to the field surface, the objective surface having a cylindrical component increasing coincidence of foci in at least one plane to maximize throughput of the second beam of radiation propagating through the sample cell via multiple reflections on each of the field surface and the objective surface; a flow mechanism establishing a flow of a sample of gas through the sample cell; a cooled detector in optical communication with the sample cell, the cooled detector receiving the interference signal propagating through the sample in the sample cell; a processor in electrical communication with the cooled detector, the processor determining from the interference signal an absorption profile for a trace gas in the sample; and a housing in which the source, the interferometer, the sample cell, the cooled detector and the processor are disposed; wherein the volume of the sample cell and the number of reflections of the second beam of radiation are optimized to detect a trace gas having a concentration of less than about 500 ppb in the sample of ambient air.