CAST Microbulk Micromegas in the Canfranc Underground Laboratory

During the last taking data campaigns of the CAST experiment, the micromegas detectors have achieved background levels about 5 to 9 ×10−6keV−1cm−2s−1 between 2 and 9 keV. This performance has been possible thanks to the introduction of the microbulk technology, the implementation of a shielding and the development of discrimination algorithms. It has motivated new studies towards a deeper understanding of CAST detectors background. One of the working lines includes the construction of a replica of the set-up used in CAST by micromegas detectors and its installation in the Canfranc Underground Laboratory. Different contributions to the detectors background have been evaluated and an upper limit < 2 × 10−7keV−1cm−2s−1 for the intrinsic background of the detector has been obtained.