Gas cell for the optical analysis of gases

Abstract

A measuring cell for a gas analysis spectrometer has an inner chamber ( 23 ) for a sample gas to be analyzed and an inlet ( 21 ) and an outlet ( 22 ) which are connected thereto. A traversing optical path for a measuring beam ( 14 ) is formed in the inner chamber ( 23 ). The measuring cell is tubular, the inlet ( 21 ) and the outlet ( 22 ) are arranged at opposite ends, and the inner chamber ( 23 ) of the measuring cell has a cross-sectional shape that is monotonic over the length of the tube and which has an oval-shape at the start, which disappears toward the end. That special shape results in fast gas exchange and thus high dynamics, even with larger measuring cells, which have high sensitivity due to the long optical paths thereof. Two characteristics which until now appeared to be conflicting are thereby combined.

1 - 8 . (canceled) 
     
     
         9 . A flow-through measuring cell for a gas analysis spectrometer, the measuring cell comprising:
 a casing defining a tubular inner chamber for a sample gas to be analyzed, said tubular chamber having an outer surface, a first end and a second end;   an inlet communicating with said tubular chamber at said outer surface and proximate said first end, said inlet having a tangential component;   an outlet communicating with said tubular chamber at said outer surface and proximate said second end, said outlet having an axial component, wherein said tubular chamber has a substantially oval cross-sectional shape proximate said inlet, which decreases monotonically along a length thereof and substantially vanishes proximate said outlet;   a first concave mirror disposed at said first end of said tubular chamber;   a second concave mirror disposed at said second end of said tubular chamber, wherein said first and said second mirrors induce a multiply reflected, fanned out optical path for a measuring beam in said tubular chamber.   
     
     
         10 . The measuring cell of  claim 9 , wherein said inlet is disposed in said casing of the measuring cell. 
     
     
         11 . The measuring cell of  claim 9 , wherein said axial component of said outlet is disposed in such a way that said outlet forms an angle of no more than 30° with a center axis of the measuring cell. 
     
     
         12 . The measuring cell of  claim 11 , wherein said outlet has a cross-section that is tapered towards an outside. 
     
     
         13 . The measuring cell of  claim 9 , wherein said tubular chamber has a substantially circular cross section proximate said outlet. 
     
     
         14 . The measuring cell of  claim 9 , wherein said cross sectional shape of said tubular chamber at said inlet and said outlet differ but have a substantially same surface area. 
     
     
         15 . The measuring cell of  claim 9 , further comprising an additional element which is connected to an outlet end and has a cross-section progression, which is inverse with respect to said tubular chamber.