Radiation experience with the CMS pixel detector

TL;DR

This paper reports on the radiation effects observed in the CMS pixel detector during LHC operation, analyzing sensor degradation and performance impacts due to high-radiation environment.

Contribution

It provides detailed measurements and analysis of radiation damage effects on the CMS pixel detector sensors during LHC's first run.

Findings

Leakage current increased with radiation fluence

Depletion voltage showed significant variation over time

Hit reconstruction efficiency was affected by radiation damage

Abstract

The CMS pixel detector is the innermost component of the CMS tracker occupying the region around the centre of CMS, where the LHC beams are crossed, between 4.3 cm and 30 cm in radius and 46.5 cm along the beam axis. It operates in a high-occupancy and high-radiation environment created by particle collisions. Studies of radiation damage effects to the sensors were performed throughout the first running period of the LHC. Leakage current, depletion voltage, pixel readout thresholds, and hit finding efficiencies were monitored as functions of the increasing particle fluence. The methods and results of these measurements will be described together with their implications to detector operation as well as to performance parameters in offline hit reconstruction.