Gas analysis system having buffer gas inputs to protect associated optical elements

An apparatus for the analysis of a gas sample comprising:

• a laser light source for producing a laser beam, said laser source comprising:
• a resonant cavity;
• and
• a lasing medium located within said resonant cavity;
• and
• a gas cell positioned within said resonant cavity, said gas cell comprising:
• a housing;
• an analysis chamber within said housing, said analysis chamber having a sample interaction region;
• a sample gas inlet port formed in said housing for introducing a gas sample into said analysis chamber and sample interaction region;
• a buffer gas inlet port formed in said housing for receiving a flow of buffer gas;
• a bas outlet port formed in said housing wherein said outlet port provides an outlet for said buffer gas and said gas sample in a manner which substantially prevents mixing of the sample gas and the buffer gas in said sample interaction region;
• and
• a light output channel for transporting light which is scattered out of said laser beam by said gas sample in said sample interaction region, said light output channel configured so that it prevents the transport of light scattered by said sample gas which, after scattering from said sample gas, propagates through any region containing buffer gas.

A gas analysis system comprising:

• a laser, said laser having a longitudinal resonant cavity for propagating a light beam, wherein the ends of said cavity are defined by first and second high reflectivity mirrors;
• a gas analysis cell positioned within said resonant cavity intermediate said mirrors, said gas analysis cell comprising:
• an analysis chamber having a first end, a second end, and an interaction region;
• a sample gas inlet port located intermediate said analysis chamber first and second ends for introducing a gas sample into said analysis chamber and interaction region;
• first and second buffer gas inlet ports located at said first and second ends of said analysis chamber for introducing a flow of buffer gas into said analysis cell;
• and
• first and second outlet ports located at said first and second ends of said analysis chamber for removing said buffer and sample gases from said analysis cell such that the flow of buffer gas between said buffer gas inlet ports and said outlet ports confines said gas sample to said analysis chamber substantially prevents mixing of said sample gas and said buffer gas in said interaction region;
• and
• a detector for sensing light scattered out of said light beam by said gas sample in said interaction region, wherein the path of said scattered light from said interaction region to said detector does not traverse any region containing said buffer gas.

A method for constraining and analyzing a gas sample within a gas analysis cell having a sample interaction region, said method comprising the steps of:

• introducing said ga sample into said gas analysis cell and sample interaction region;
• introducing a flow of buffer gas into said analysis cell such that said flow of buffer gas through said gas analysis cell substantially confines said gas sample within said gas analysis cell and substantially prevents mixing of said buffer gas and said sample gas within said sample interaction region;
• illuminating said gas sample with electromagnetic radiation;
• and
• collecting and detecting electromagnetic radiation scattered by said gas sample in said sample interaction region such that the only scattered electromagnetic radiation which is detected traverses a path from said sample interaction region through regions containing pure sample gas.

A device for the analysis of gases in a gas sample utilizing light scattering, comprising:

• a light source;
• an optical cavity which propagates light produced by said light source;
• a gas analysis chamber for receiving a gas sample, said chamber including a sample interaction region, wherein said chamber is positioned within said optical cavity and in fluid communication with at least a portion of said cavity located outside said analysis chamber;
• a buffer gas inlet port for introducing buffer gas into said gas analysis chamber but not into said sample interaction region of said analysis chamber, thereby creating in said sample interaction region a region of pure sample gas;
• a detector for sensing light scattered from said gas sample in said sample interaction region of said gas analysis chamber, wherein said sensed scattered light traverses a path from the sample gas scattering location to the detector which is devoid of said buffer gas.