Abstract
The Analog Hadronic Calorimeter (AHCAL) is one option of highly granular calorimeters optimised with the Particle Flow Algorithm (PFA) and considered for experiments at future lepton colliders. It consists of dense steel plates as absorber interleaved with plastic scintillator tiles, individually read out by Silicon Photomultipliers (SiPMs). A novel SiPM developed by the Novel Device Laboratory (NDL) with an active area of 1 mm2 and a pixel pitch of 12.5 micron[NDL-SiPM-12.5] has been mainly investigated. The characterisation studies include single photon calibration, dynamic range and performance of crosstalk as well as Minimum Ionising Particle (MIP) detection efficiency of a detector unit. Combined tests with a dedicated ASIC (SPIROC2E) for multi-channel SiPMs show that single photon spectra can be obtained, given the relatively small SiPM gain (∼2 × 105). The linearity of the SiPMs in response to incident photons of less than 10,000 (500 MIPs) is within 5% from measurements. Meanwhile, the dark count rate (DCR) is around 2×10-3 Hz at a threshold 0.5 MIP (10 p.e.) and the MIP detection efficiency of a detector unit can be near 95% from the MIP spectrum. These studies indicate the NDL-SiPM-12.5 can be a photosensor candidate for the future scintillator-based hadronic calorimeters.