Proton irradiation of analogue opto-hybrid circuits for the CMS tracker

Four analogue opto-hybrid circuits to be used in the front-end electronics of the Compact Muon Solenoid (CMS) tracker were irradiated with 26 MeV protons to fluences of 0.5×1014 and 0.8×1014 p/cm2 in the secondary beam of the cyclotron at the Forschungszentrum (FZK) in Karlsruhe (Germany). The purpose of the test was to measure the tolerance of the circuit to a radiation exposure as that foreseen in the CMS Tracker in 10 years of life. To this end, a set of electrical measurements of the static and dynamic behaviour of the irradiated circuits were made before and after the test. In order to monitor the variations due to the increasing irradiation, the output light power of the opto-hybrids was constantly measured during the test. The measurements taken during the irradiation test are reported and discussed in this paper and the circuit performance, tested before and after the irradiation, is compared.