Beam test results of 25 and 35 $$\mu$$m thick FBK ultra-fast silicon detectors

This paper presents the measurements on first very thin Ultra-Fast Silicon Detectors (UFSDs) produced by Fondazione Bruno Kessler; the data have been collected in a beam test setup at the CERN PS, using beam with a momentum of 12 GeV/c. UFSDs with a nominal thickness of 25 and 35 $$\mu$$ μ m and an area of 1 $$\times$$ × 1 $$\text {mm}^2$$ mm 2 have been considered, together with an additional HPK 50-$$\mu$$ μ m thick sensor, taken as reference. Their timing performances have been studied as a function of the applied voltage and gain. A time resolution of about 25 ps and of 22 ps at a voltage of 120 and 240 V has been obtained for the 25 and 35 $$\mu$$ μ m thick UFSDs, respectively.