Test Beam Results and Performance Studies of ATLAS Micromegas Production Modules

Abstract

The LHC at CERN plans to have a series of upgrades to increase its instantaneous luminosity up to 7.5 × 1034 cm−2·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 ˜2.4 million readout channels in total. This is the first time that Micromegas detectors are built in such a large scale. In total, 128 Micromegas modules up to 3 m2 in size, will be produced in different sites spread across Europe, targetting for 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 beam line of SPS at CERN during the summer of 2018. We present the test setup and performance results, namely effciency and resolution, for perpendicular and inclined tracks. These studies were focused on determining the high voltage working point of the ATLAS Micromegas detectors. Studies with several gas mixtures were also carried out and will be presented.