In this paper we report measurements of the uniformity of time resolution, signal amplitude, and charged particle detection efficiency across the sensor surface of low-gain avalanche detectors (LGAD). Comparisons of the performance of sensors with different doping concentrations and different active thicknesses are presented, as well as their temperature dependence and radiation tolerance up to 6×1014 n/cm2. Results were obtained at the Fermilab test beam facility using 120 GeV proton beams, and a high precision pixel tracking detector. LGAD sensors manufactured by the Centro Nacional de Microelectrónica (CNM) and Hamamatsu Photonics (HPK) were studied. The uniformity of the sensor response in pulse height before irradiation was found to have a 2% spread. The signal detection efficiency and timing resolution in the sensitive areas before irradiation were found to be 100% and 30–40 ps, respectively. A “no-response” area between pads was measured to be about 130 μm for CNM and 170μm for HPK sensors. After a neutron fluence of 6×1014 n/cm2 the CNM sensor exhibits a large gain variation of up to a factor of 2.5 when comparing metalized and non-metalized sensor areas. An irradiated CNM sensor achieved a time resolution of 30 ps for the metalized area and 40 ps for the non-metalized area, while a HPK sensor irradiated to the same fluence achieved a 30 ps time resolution.

This work was supported by the Fermilab LDRD 2017.027 ; by the United States Department of Energy grant DE-FG02-04ER41286 ; by the California Institute of Technology High Energy Physics under Contract DE-SC0011925 ; by the European Union’s Horizon 2020 Research and Innovation funding program, under Grant Agreement no. 654168 (AIDA-2020) and Grant Agreement no. 669529 (ERC UFSD669529) ; by the Italian Ministero degli Affari Esteri under the Italy-US scientific collaboration program and INFN Gruppo V UFSD project; and by the Spanish Ministry of Economy, Industry and Competitiveness through the Particle Physics National Program (ref. FPA2014-55295-C3-2-R and FPA2015-69260-C3-3-R ) co-financed with FEDER funds.

This document was prepared using the resources of the Fermi National Accelerator Laboratory (Fermilab), a U.S. Department of Energy, Office of Science, HEP User Facility. Fermilab is managed by Fermi Research Alliance, LLC (FRA), acting under Contract No. DE-AC02-07CH11359. Part of this work was performed within the framework of the CERN RD50 collaboration.

Peer reviewed