Protection circuit for the T2 readout electronics of the TOTEM experiment

The TOTEM experiment (TOTal and Elastic Measurement) will measure the inelastic proton–proton interaction at the Large Hadron Collider (LHC). The T2 telescope will be based on Gas Electron Multiplier (GEM) detector technology. The tight geometric requirements for the readout electronics lead to the development of a miniaturised protection circuit for the front-end readout electronics to avoid damage caused by discharges occurring in the GEM detectors. We have developed an integrated protection circuit version of the discrete protection electronics used in the COMPASS experiment (Common Muon and Proton Apparatus for Structure and Spectroscopy). We have tested successfully such integrated protection circuits by connecting them to APV25 front-end readout chips and to the first GEM detector prototype of the TOTEM experiment. All channels of the APV25 chips worked properly after more than 2000 discharges generated in the GEM detector by heavily ionising α-particles, whereas tests done without protection circuit reported full damage of the APV25 chip after a single discharge occurring in the GEM detector.