Performance of the new Readout Electronics for the ATLAS (s)MDT Chambers and Future Colliders at High Background Rates

TL;DR

This paper presents the development and testing of a new readout electronics system for small-diameter drift tube detectors, enhancing their performance at high background rates for future collider experiments.

Contribution

Introduction of a faster, more precise readout chip with baseline restoration to improve sMDT detector performance under high background conditions.

Findings

Improved spatial and time resolution with the new readout electronics.

Enhanced detection efficiency at high gamma-background rates.

Successful validation through extensive CERN tests.

Abstract

Small-diameter Drift Tube (sMDT) detectors with 15 mm tube diameter have proven to be excellent candidates for precision muon tracking detectors in experiments at future hadron colliders like HL-LHC and FCC-hh where unprecedentedly high background rate capabilities are required. sMDT chambers are currently being installed in the inner barrel layer of the ATLAS muon spectrometer. The rate capability of the sMDT drift tubes in terms of muon detection efficiency and spatial resolution is limited by the performance of the readout electronics. A new (s)MDT ASD (Amplifier-Shaper-Discriminator) readout chip for use at the HL-LHC and future hadron colliders with a faster peaking time compared to the old chip has been developed, reducing the discriminator threshold crossing time jitter and thus improving the time- and spatial resolution with and without $\gamma$-background radiation. Additionally, a method compensating the gas gain drop due to space charge at high $\gamma$-background hit flux by adjusting the sMDT operating voltage will be presented. Simulations show, that the addition of active baseline restoration circuits in the front-end electronics chips in order to suppress signal-pile-up effects at high counting rates further leads to significant improvement of both efficiency and resolution. Extensive tests using sMDT test chambers have been performed at the CERN Gamma Irradiation Facility (GIF++). Chambers equipped with new readout chips with improved pulse shaping and discrete readout circuits with baseline restoring functionality have been tested.