Frontend electronics for the Phase-II upgrade of the ATLAS small-diameter Muon Drift Tube detector

The ATLAS monitored drift tube (MDT) chambers are the main component of the precision tracking system in the ATLAS muon spectrometer. The MDT system is capable of measuring the sagitta of muon tracks to an accuracy of 60 μm, which corresponds to a 10% momentum accuracy for muons with transverse momentum (pT) of 1 TeV. ATLAS plans to use the MDT detector at the first-trigger level to improve the muon transverse momentum resolution and reduce the trigger rate expected from the High-Luminosity LHC (HL-LHC) runs. A new trigger and readout system has been proposed. Prototypes for two frontend ASICs (Amplifer-shaper-discriminator – ASD, and Time-to-digital converter – TDC) and a data transmission board (Chamber service module – CSM) have been designed and tested. I will present the design of the new TDC ASIC, its performance, and the joint tests with CSM with a small-diameter MDT chamber.