Readout and data transfer systems in the detectors of the ATLAS experiment

Abstract

To benefit from the expected increase in luminosity of the upgraded LHC accelerator, the detector system "New Small Wheel (NSW)" replaced the innermost detection station in the forward region of the ATLAS Muon Spectrometer. NSW features two new detector technologies; the resistive Micromegas detectors (MM) and the small strip Thin Gap Chambers (sTGC), comprising more than 2 million readout channels. The large number of readout channels, the high data rates, and the harsh conditions under which the NSW will operate pose significant challenges to its trigger and data acquisition system. The Level-1 Data Driver Card (L1DDC) boards are part of the NSW detector electronics. Three types of L1DDC boards had massively been produced; two for the readout chain of the MMs and sTGCs and one for the trigger electronics chain of the sTGCs. A fully automated testing setup has been developed to evaluate the performance of 1184 L1DDC boards that have been tested at four testing sites; at the University of West Attica (UNIWA), the National Kapodistrian University of Athens (NKUA), the National Centre for Scientific Research (NCSR Demokritos), and CERN. Besides the L1DDCs testing setup development and the L1DDCs' performance evaluation and debugging, several off-detector boards have been designed and tested to address several problems of the NSW electronic systems that emerged during their integration on the detector. The most critical one was the severe noise problems which jeopardized the on-time installation of the NSW on the ATLAS detector given the LHC run startup. All possible noise sources have been investigated, and adequate repairs have been performed. The primary noise source has been identified to be the power supplies that power all the detector electronics. A filter has been designed and implemented on a mezzanine board hosted on the ICS power supplies' front panels reducing the noise to acceptable levels. The mezzanine boards (128) carrying the UNIWA logo have been installed on the NSW detector (Side-C) and the spare ICSes.