Development of the gas system for the CLOUD experiment at CERN

The Cosmics Leaving Outdoor Droplets (CLOUD) experiment aims to recreate atmospheric conditions inside a large chamber where the mechanisms for the formation of aerosol and cloud are studied. Aerosol and cloud are recognized as representing the largest uncertainty in the current understanding of climate change together with the influence of the cosmic rays. The CLOUD chamber, a 26 m³ cylinder, has been built to the highest technical standard of cleanliness. A key aspect of the CLOUD experiment is the gas system. The present contribution describes the last modifications and upgrades introduced for the 2013 data taking period.