Micromegas in CAST and prospects

A low background Micromegas X-ray detector has been used to search for solar axions in the CAST experiment at CERN. The detector has an active area of 7cm times 7cm, excellent spatial resolution (~70nm), and good energy resolution. It is built using low radioactivity materials and the obtained background level is below 5times10
^-5
counts/keV/cm
²
/s. The detector is being upgraded for the second phase of the experiment (2006-2007) with a reduced active area. A focusing X-Ray optic and improved shielding will be used to further reduce the background by approximately two orders of magnitude.