Performance of the Fermi-LAT silicon strip tracker after 14 years of operation

Abstract

The Large Area Telescope (LAT) is the primary instrument onboard the Fermi Gamma-ray Space Telescope launched on June 11 2008. It is an imaging, wide field-of-view, gamma-ray telescope, covering the energy range from 30 MeV to more than 300 GeV. The LAT tracker is formed by silicon strip planes alternated with tungsten foils and is used to convert the incoming photon into an electron-positron pair and to measure its direction. Here we describe the performance of the LAT tracker, that has been constantly monitored using calibration and science data. In particular we show that, after almost 14 years of continuous operation in space, the fraction of defective channels is less than 0.5% while the readout noise increased less than 5%.