An ultra-low-background detector for axion searches

A low background Micromegas detector has been operating in the CAST experiment at CERN for the search of solar axions since the start of data taking in 2002. The detector, made out of low radioactivity materials, operated efficiently and achieved a very low level of background (5×10^-5 keV^-1-cm^-2-s^-1) without any shielding. New manufacturing techniques (Bulk/Microbulk) have led to further improvement of the characteristics of the detector such as uniformity, stability and energy resolution. These characteristics, the implementation of passive shielding and the improvement of the analysis algorithms have dramatically reduced the background level (2×10^-7 keV^-1-cm^-2∣s^-1), improving thus the overall sensitivity of the experiment and opening new possibilities for future searches.