“In early 2019 the CMS Phase-1 Pixel detector was extracted from the underground cavern after successful completion of the LHC Run 2 data taking campaign. Its sub-detectors, the Barrel Pixel (BPIX) and Forward Pixel (FPIX) detectors, were stored cool and dry in a clean room facility on the surface to protect the silicon sensors during the long shutdown (LS2) in 2019-2021. The detectors were refurbished and repaired during LS2 to improve the quality of the collected data and the operational stabiliy in the next period of the data taking (Run 3). At the end of June 2021, the detectors were installed in their habitual location inside the CMS detector.”
More information here.