Timing resolution of a plastic scintillator counter read out by radiation damaged SiPMs connected in series
Abstract
This paper discusses the effects of radiation damage to SiPMs on the performances of plastic scintillator counters with series-connected SiPM readout, focusing on timing measurements. The performances of a counter composed of a 120 × 40 ×5~mm3 scintillator tile read out by two sets of six SiPMs from AdvanSiD connected in series attached on the short sides are presented, for different combinations of SiPMs at various levels of irradiation. Firstly, six SiPMs were equally irradiated with electrons from 90Sr sources up to a fluence of e-≈ 3 × 1012~cm-2. The timing resolution of the counter gradually deteriorated by the increase in dark current. The dark current and the deterioration were reduced when the counter was cooled from 30 to 10. Secondly, 33 SiPMs were irradiated with reactor neutrons. The characteristics of counters read out by series-connected SiPMs with non-uniform damage levels, were investigated. The signal pulse height, the time response, and the timing resolution depend on the hit position in the counter, when SiPMs' irradiation is not uniform.