CMS Drift Tubes performance

The CMS muon barrel system includes 250 Drift Tubes (DT) stations that require 172,000 readout channels for triggering and measurement of the muon transverse momentum. After the first Long Shutdown (LS1) of CMS, the fraction of active channels remains higher than 99\%. The spatial resolution ranges between 200 and 250 $\mathrm{\mu m}$ in the phi direction, and the intrinsic time resolution is about 2ns. In addition the DT system showed excellent performance during Run 1, with very low associated down time and only a small fraction of data not qualified by the data certification procedure. However, the conditions anticipated for the High Lumi (HL)-LHC will require an upgrade of the on-board electronics to deal with the higher radiation environment and the higher trigger rate. Replacement of the so-called mini-crates installed alongside the chambers is scheduled for LS3.