Dynamics of windowless vapour containment systems for absorption spectroscopy

The relations between mass loss-rates and path number-density integrals for certain windowless dynamic vapour containment system geometries are developed for non-turbulent vapour flow. The results are applicable not only to the design and performance prediction of such devices, but to integrated number density measurement. A simple relation is found between the flow regime required to observe optical absorption and the ratio of absorption to gas collisional cross sections. A furnace employing tubular flow impedance elements extending nearly from the vapour source to the ends of the system appears to optimize optical absorption depth with respect to mass loss rate over a wide range of pressures, giving order-ofmagnitude improvements over simple orifice impedances. Containment system designs based on this geometry have been tested at the Bonn synchrotron radiation facility and shown to be practical