The possible influence of cosmic rays on aerosols and clouds is of considerable interest. The CLOUD (Cosmic leaving outdoor droplets) experiment at CERN aims to study under controlled conditions the effects of cosmic rays on particle formation, cloud droplets and ice particles. In the atmosphere, some molecules can agglomerate to form a “big” particle which can act as a seed for a cloud droplet. The number and size of droplets affect the clouds’ properties like their brightness or life time, and therefore influence the climate. Using the CLOUD chamber, different mechanisms of particle formation are investigated under various controlled atmospheric conditions, like temperature, humidity, air purity and ionization. The CERN Proton Synchrotron beam is used to vary the ionization rate of the molecules inside the CLOUD chamber, like natural galactic cosmic rays do in the atmosphere. This allows to quantify the effect of the variation of galactic cosmic rays on cloud seed formation.
Technical input for the CLOUD design was obtained in 2006 in a pilot experiment located in the CERN PS T11 beam line. The present CLOUD experimental facility was installed in the same beam line in 2009. Two successful campaigns have been carried out, in November-December 2009 and June 2010, to study ion-induced and neutral binary nucleation of H2SO4 and H2O. In this seminar the CLOUD experimental facility and the atmospheric detectors brought by the collaborating institutes will be described.
Organizer: Joachim Baechler PH-TOT