Upgrades of the ATLAS Muon Spectrometer with sMDT Chambers

TL;DR

This paper discusses the development and deployment of small-diameter Muon Drift Tube (sMDT) chambers in the ATLAS muon spectrometer, enhancing rate capability, installation efficiency, and spatial resolution.

Contribution

The paper introduces the design, construction, and successful installation of sMDT chambers, significantly improving detector performance and installation efficiency over traditional MDT chambers.

Findings

sMDT chambers have ten times higher rate capability.

Installation time reduced by a factor of seven.

Improved sense wire positioning accuracy to better than ten microns.

Abstract

With half the drift-tube diameter of the Monitored Drift Tube (MDT) chambers of the ATLAS muon spectrometer and otherwise unchanged operating parameters, small-diameter Muon Drift Tube (sMDT) chambers provide an order of magnitude higher rate capability and can be installed in detector regions where MDT chambers do not fit. The chamber assembly time has been reduced by a factor of seven to one working day and the sense wire positioning accuracy improved by a factor of two to better than ten microns. Two sMDT chambers have been installed in ATLAS in 2014 to improve the momentum resolution in the barrel part of the spectrometer. The construction of an additional twelve chambers covering the feet regions of the ATLAS detector has started. It will be followed by the replacement of the MDT chambers at the ends of the barrel inner layer by sMDTs improving the Performance at the high expected background rates and providing space for additional RPC trigger chambers.