The Micromegas chambers for the upgrade of the forward muon detector of ATLAS

The ATLAS collaboration at LHC has chosen the resistive Micromegas technology, along withthe small-strip Thin Gap Chambers (sTGC), for the high luminosity upgrade of the first muonstation in the high-ηregion (i.e.1.3 < |η| < 2.7), the so called New Small Wheel (NSW) project[1]. After the R&D phase, design and prototyping phase, the first series production Micromegasquadruplets are being constructed at the involved construction sites (France, Germany, Italy, Rus-sia and Greece). All the Micromegas boards produced in industries and delivered at CERN areundergoing a detailed quality control and quality assurance (QAQC) under the supervision of theCERN group. This is a big step forward towards the installation of the NSW foreseen for the LHClong shutdown in 2019 and 2020. The construction of the four types of large size quadruplets,all having trapezoidal shapes with surface areas between 2 and 3 m2, will be briefly described.The achievement of the requirements for these detectors revealed to be even more challengingthan expected, when scaling from the small prototypes to the large dimensions. The encounteredproblems and the proposed solutions are to a large extent common to other micro-pattern gaseousdetectors. Final quality assessment and validation results on the achieved mechanical precision,on the high-voltage stability during operation with and without irradiation are described togetherwith results from test-beam studies with the first production chambers.