Construction procedure and first tests of the SM1 type microgas chambers for the new small wheel within the phase 1 upgrade of the forward muon spectrometer of the ATLAS Experiment

MICRO MEsh GASeous structure chambers, MicroMegas (MM), are an innovative designconcept for Micro-Pattern Gaseous Detectors, designed in order to provide highperformances, in terms of spatial resolution and efficiency, even with highlyirradiated environments. These chambers have been chosen as new precisiontracking detectors for the upgrade of the forward muon spectrometer of the ATLASexperiment. MM trapezoidal detector modules, with areas between 2 and 3 m 2 ,will be part of the two New Small Wheels (NSW) composing the innermost stationof the ATLAS muon tracking forward system. MM detectors are composed by 4 read-out layers, two for the reconstruction of the precision coordinate and two withstereo reading (±1.5 •) for the reconstruction of the second coordinate. MMchambers are designed to provide efficiency better than 95% per single plane atrate capability up to 15 kHz/cm 2 , in presence of magnetic fields up to 0.3 T.The Istituto Nazionale di Fisica Nucleare (INFN) is deeply involved in theconstruction of these chambers and in their validation at the Cosmic Ray Stand(CRS) in the Frascati National Laboratories (LNF) of the INFN. Preliminaryresults on the validation method and tests performed on INFN SM1 prototype arepresented