Detecting Ice Nuclei with a Continuous—Flow Diffusion Chamber-Some Exploratory Tests of Instrument Response

Abstract

A few basic experiments were performed with artificial cloud condensation nuclei and ice-nucleating aerosols in a continuous-flow thermal gradient diffusion chamber to investigate the instrument's response. Brief pulses of ice nuclei were input to the chamber and were detected approximately 8 s later as pulses of ice crystals at the outlet. The temporal rise and fall responses were of exponential type, with time constants of about 1 s. These fast response characteristics aye due to the chamber's laminar flow and the central location of the aerosol sample. Changes in the size distribution of crystals at the outlet of the chamber were monitored in response to changes in total airflow through the chamber. The results indicated that the crystals were fewer and smaller as their residence time in the chamber decreased.