Contribution to the search for solar axions in the CAST experiment

The CERN Axion Solar Telescope (CAST) is an implementation of the axion helioscope with the highest sensitivity to date. In the present thesis the results of the analysis of one of the Micromegas detectors in CAST (sunrise side) for the 2009 and 2010 data taking periods are presented. A new detector lab has been realized at CERN (162 S-065) with a variable energy calibration system based on an X-ray beam line built at the Max-Planck-Institut für extraterrestrische Physik/Garching (MPE). The purpose of this work is to calibrate for the first time the present and future CAST detectors, in a number of energies and test the efficiency of the software selection criteria.The results of the measurements in the lab were used in the analysis of the data acquired in 2009 and 2010 with the sunrise Micromegas detector of CAST.\nThe data are consistent with no axion signal, thus a limit in the coupling constant of axions to photons is extracted in the axion mass range 0.655 -1.01 eV/c2: gαγ ≤ 3.9×10-10 GeV-1 at 95% CL, which is expected to be slightly improved by the contribution of the rest of the detectors.