Beam test results of a 16 ps timing system based on ultra-fast silicon detectors

Abstract

In this paper we report on the timing resolution obtained in a beam test with pions of 180GeV/c momentum at CERN for the first production of 45µm thick Ultra-Fast Silicon Detectors (UFSD). UFSD are based on the Low-Gain Avalanche Detector (LGAD) design, employing n-on-p silicon sensors with internal charge multiplication due to the presence of a thin, low-resistivity diffusion layer below the junction. The UFSD used in this test had a pad area of 1.7mm2. The gain was measured to vary between 5 and 70 depending on the sensor bias voltage. The experimental setup included three UFSD and a fast trigger consisting of a quartz bar readout by a SiPM. The timing resolution was determined by doing Gaussian fits to the time-of-flight of the particles between one or more UFSD and the trigger counter. For a single UFSD the resolution was measured to be 34ps for a bias voltage of 200V, and 27ps for a bias voltage of 230V. For the combination of 3 UFSD the timing resolution was 20ps for a bias voltage of 200V, and 16ps for a bias voltage of 230V.