A COOLABLE LONG PATH ABSORPTION CELL FOR LABORATORY SPECTROSCOPIC STUDIES OF GASES

A long path absorption cell (Long White Cell) which has been designed and built for laboratory spectroscopic studies of gases found in terre strial and planetary atmospheres is described. Factors influencing the design and construction are discussed, including aspects of the optic al, mechanical, cryogenic, vacuum, gas handling and safety systems, an d the pressure and temperature monitoring systems. The practical capab ilities of the cell include absorber pathlengths up to 512 m, gas samp le pressures up to 5 bar and temperatures between 190 and 300 K, and t he suitability for use with corrosive and flammable gases. The perform ance of the cell is discussed in relation to spectroscopic measurement s of mixtures of gaseous methane and hydrogen.