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Abstract-We report on measurements on Ultra-Fast Silicon Detectors (UFSD) which are based on Low-Gain Avalanche Detectors (LGAD). They are n-on-p sensors with internal charge multiplication due to the presence of a thin, low-resistivity diffusion layer below the junction, obtained with a highly doped implant. We have performed several beam tests with LGAD of different gain and report the measured timing resolution, comparing it with laser injection and simulations. For the 300μm thick LGAD, the timing resolution measured at test beams is 120ps while it is 57ps for IR laser, in agreement with simulations using Weightfield2. For the development of thin sensors and their readout electronics, we focused on the understanding of the pulse shapes and point out the pivotal role the sensor capacitance plays.

In this paper we present an initial study on the effects induced by radiation on the signal generated by a minimum ionizing particle in silicon detector. The results are obtained by implementing in the simulation program Weightfield2 (WF2) charge carrier trapping and non linear distribution of the electric field. Results of sample simulations are presented, along with a discussion of the limitations of the current approach and ideas for future improvements.