Upgrades to the CMS Cathode Strip Chambers for the HL-LHC

The Large Hadron Collider (LHC) will be upgraded in several phases to significantly expand its physics program, and these upgrades present major challenges to the operations of the CMS Cathode Strip Chamber muon system. After the current long shutdown during 2018–2021 (LS2), the accelerator luminosity will have increased, exceeding the design value of 1034 cm−2s−1 and allowing the CMS experiment to collect approximately 100 fb−1/year. A subsequent upgrade in 2023–2024 will increase the luminosity up to 5 × 1034 cm−2s−1. The CMS muon system must be able to sustain a physics program after the LS2 shutdown that maintains and enhances sensitivity to electroweak scale physics and for TeV scale searches similar to what was achieved up to now. For the Cathode Strip Chamber (CSC) muon detectors, the electronics will be upgraded to handle the expected higher data rates. The design of the upgraded CSC electronics is discussed in this report. In addition, accelerated irradiation tests are being performed to study the behaviour of the CSC electronics under conditions that are nearly an order of magnitude beyond the original design values. Studies have also been performed of chamber gas mixtures to reduce greenhouse-gas impacts. The status of this irradiation campaign and results are presented.