Test Beam Results and Performance Studies of ATLAS Micromegas Production Modules

The LHC at CERN plans to have a series of upgrades to increase its instantaneous luminosity up to $7.5\times10^{34}\text{cm}^{-2}\text{s}^{-1}$. The ATLAS experiment will upgrade its inner end-cap muon chambers to cope with the increased collision rate expected from the High-Luminosity-LHC. This project, called New Small Wheel, includes resistive Micromegas chambers together with small-strip Thin Gap Chambers, forming a system of $\sim$2.4 million readout channels in total. This is the first time that large Micromegas are built in such a scale. In total, 128 Micromegas modules up to $3\,\text{m}^2$ in size, and from different production sites spread across Europe, will be produced, targetting an installation at the end of the Long Shutdown 2 of the LHC. One of the first series modules, equipped with a prototype of the final front-end electronics based on the VMM chip, was tested in a muon/pion beam at the H8 line of SPS at CERN during the summer of 2018. We present the test setup and performance results namely efficiency and resolution for perpendicular and inclined tracks. These studies were focused on determining the working point of the ATLAS Micromegas detectors. Studies with several gas mixtures were also carried out and will be presented.