The isothermal haze chamber with discontinuous flow: a new experimental device for CCN measurements at low supersaturation

Ž . An isothermal haze chamber IHC has been designed, incorporating results from the tests of Ž . earlier instruments held at the 1981 Reno NV workshop. This instrument, named isothermal haze Ž . chamber with discontinuous flow IHCDF , periodically discontinues the flow through the haze chamber in order to form a well-defined region of 100% RH in the center of the chamber. Indeed, tests performed with our conventional continuous flow IHC showed a poorly defined 100% RH field in the chamber, mainly due to an unsteady laminar air flow through the chamber during measurement. Experiments with polydispersed NaCl aerosol showed that a supersaturation spectrum could be obtained within a growth time of 300 s, over a supersaturation range of 0.01–0.1%. The instrument is suitable for field use. It is contained in a package 1.4 m high and weighs 5 kg. Three minutes is required to collect the air sample and 5 min for drop growth, thus permitting the analysis of seven samples per hour. q 2000 Elsevier Science B.V. All rights reserved.