概要
The pixel detector of the CMS experiment at the CERN LHC has been replaced by an entirely new one in March 2017. The phase 1 upgrade of the CMS pixel detector was motivated by the need of reducing dynamic data losses for instantaneous luminosities in excess of $1 \times 10^{34}$ cm$^{-2}$s$^{-1}$ due to bandwidth limitations in the readout chips of the old detector. In addition to new readout chips the upgraded CMS pixel detector features one extra sensitive layer, reduced distance from the beam for the innermost layer, a CO$_2$ cooling system and lighter support structures to reduce the material budget, and a $\mu$TCA-based backend control and readout system replacing the old VME-based system. This presentation summarizes the design, construction, and commissioning of the new detector, as well as the operational experience and lessons we learned, including results on the detector performance. Finally the plans for the detector maintenance during the year-end-technical stop of the LHC will be discussed, focusing on the repairs required to address a recent problem related to the DC-DC converters.