Operation and performance of the ATLAS semiconductor tracker

TL;DR

This paper details the operation, stability, and performance metrics of the ATLAS semiconductor tracker during initial LHC runs, highlighting high operational efficiency and stable alignment despite radiation exposure.

Contribution

It provides comprehensive operational data and performance analysis of the ATLAS silicon microstrip detector, including efficiency, noise, alignment, and radiation effects, during early LHC operation.

Findings

>99% detector module operational rate

Intrinsic hit efficiency of 99.74%

Stable detector alignment at micron level

Abstract

The semiconductor tracker is a silicon microstrip detector forming part of the inner tracking system of the ATLAS experiment at the LHC. The operation and performance of the semiconductor tracker during the first years of LHC running are described. More than 99% of the detector modules were operational during this period, with an average intrinsic hit efficiency of (99.74 +/- 0.04)%. The evolution of the noise occupancy is discussed, and measurements of the Lorentz angle, delta-ray production and energy loss presented. The alignment of the detector is found to be stable at the few-micron level over long periods of time. Radiation damage measurements, which include the evolution of detector leakage currents, are found to be consistent with predictions and are used in the verification of radiation background simulations.