Serial powering and high hit rate efficiency measurement for the Phase 2 Upgrade of the CMS Pixel Detector.

A serially powered pixel detector is the baseline choice for the High Luminosity upgrade of the inner tracker of the CMS experiment. A serial power distribution scheme, compared to parallel powering, requires less cable mass, offers higher power efficiency and is less susceptible to voltage transients. A prototype pixel readout chip has been designed for serial powering in 65\,nm CMOS technology by the RD53 collaboration. Performance results from testing the prototype chip, called RD53A, are reported. The performance of RD53A operating in a chain consisting of four chips powered in series is compared with the performance under a conventional powering scheme. Additionally, the readout efficiency of RD53A in a high hit rate environment in different operation modes is presented for the first time. The results indicate that serial powering is a robust and reliable power distribution scheme.