CLOUD

The CLOUD (Cosmics Leaving OUtdoor Droplets) experiment is an atmospheric simulation chamber at CERN, which studies nucleation and growth processes in the atmosphere. The reactor is a 26 cubic meter electro-polished stainless steel vessel that minimizes the influence of wall effects. It is filled with ultrapure cryogenic nitrogen and oxygen, making it one of the cleanest simulation chambers in the world. Its temperature can be adjusted over a wide range (-70C - +100C) to imitate different atmospheric environments, as well as humidity and illumination from different light sources. The cloud facility also allows to study cloud formation by adiabatic expansion and cooling.

CLOUD is located at the accelerator facility CERN to assess the influence of ionizing radiation on nucleation, as it exists in the upper atmosphere. Cosmic radiation underlies mid- and long-term variations. With a pion beam, and be removing ions with an electric clearing field, this charging effect can be studied systematically. The CLOUD collaboration includes a comprehensive suit of state of the art instruments from 17 institutes that measure the concentration, the size, and the composition of particles, and the gas phase concentrations of precursors.

 

CLOUD

Chamber at CLOUD (Image credit: H. Finkenzeller)

CLOUD

Image credit: CERN