The Cosmic Leaving OUtdoor Droplets (CLOUD) experiment at CERN studies new particle formation of aerosols, cloud formation and aerosol-cloud-interaction in the atmosphere. For this purpose, various atmospheric conditions are simulated under very precise and ultra-clean conditions in a 26 m³ stainless steel chamber and analysed by a suite of state-of-the-art instruments.

One of the main goals of this experiment is to study the relation between new particle formation and galactic cosmic rays. For this purpose the CLOUD experiment makes use of the proton synchrotron particle accelerator at CERN which is used to simulate the galactic cosmic rays at different altitudes and for various historical conditions.

The CLOUD project involves researchers from 17 institutes in 9 different countries, including atmospheric and environmental scientists, physicists and chemists.

The Cosmic Leaving OUtdoor Droplets (CLOUD) chamber at CERN.