Development, commissioning and operation of the large scale CO$_2$ detector cooling systems for CMS pixel phase I upgrade

Abstract

During the 2017 Year-end Technical Stop of the Large Hadron Collider at CERN, the CMS experiment has successfully installed a new pixel detector in the frame of Phase I upgrade. This new detector will operate using evaporative CO$_{2}$ technology as its cooling system. Carbon Dioxide, as state of the art technology for current and future tracking detectors, allows for significant material budget saving that is critical for the tracking performance. The road towards operation of the final CO$_{2}$ cooling system in the experiment passed through intensive prototype phase at the CMS Tracker Integration Facility (TIF) for both cooling process hardware and its control system. This paper briefly describes the general design of both the CMS and TIF CO$_{2}$ detector cooling systems, and focuses on control system architecture, operation and safety philosophy, commissioning results and operation experience. Additionally, experience in using the Ethernet IP industrial fieldbus as distributed IO is presented. Various pros and cons of using this technology are discussed, based on the solutions developed for Schneider Premium PLCs, WAGO and FESTO IOs using the UNICOS CPC 6 framework of CERN