Properties of FBK UFSDs after neutron and proton irradiation up to 6 · 10 15 neq / cm 2

The properties of 60-μm thick Ultra-Fast Silicon Detectors (UFSD) detectors manufactured by Fondazione Bruno Kessler (FBK), Trento (Italy) were tested before and after irradiation with minimum ionizing particles (MIPs) from a Sr β-source . This FBK production, called UFSD2, has UFSDs with gain layer made of Boron, Boron low-diffusion, Gallium, carbonated Boron and carbonated. The irradiation with neutrons took place at the TRIGA reactor in Ljubljana, while the proton irradiation took place at CERN SPS. The sensors were exposed to a neutron fluence of 4·10, 8·10, 1.5·10, 3·10, 6·10 neq/cm and to a proton fluence of 9.6·10 p/cm, equivalent to a fluence of 6·10 neq/cm. The internal gain and the timing resolution were measured as a function of bias voltage at -20C. The timing resolution was extracted from the time difference with a second calibrated UFSD in coincidence, using the constant fraction method for both. PACS: 29.40.Gx, 29.40.Wk, 78.47jc