Evaluation of silicon photomultipliers for dual-mirror Small-Sized Telescopes of Cherenkov Telescope Array
journal contributionposted on 16.05.2018, 13:44 by A. Asano, D. Berge, G. Bonanno, M. Bryan, B. Gebhardt, A. Grillo, N. Hidaka, P. Kachru, J. Lapington, S. Leach, Y. Nakamura, A. Okumura, G. Romeo, D. Ross, M. Stephan, H. Tajima, M. C. Timpanaro, R. White, N. Yamane, A. Zink
All camera designs for Small-Sized telescopes (SSTs) proposed for the Cherenkov Telescope Array (CTA) utilize silicon photomultipliers (SiPM) as their baseline photon sensor technology. The dual-mirror SST (SST-2M) has a smaller plate scale (i.e. image size) than the single-mirror SST, allowing it to employ 2,000 square SiPMs with pixel sizes of approximately 6 mm, close to the mainstream SiPM sizes.In CTA, the night sky background level of typically ~25 Mcounts/s/pixel ( > 100 Mcounts/s/pixel at maximum) places severe constraints on the trigger capability due to accidental coincidence on neighboring pixels. In order to suppress such events, it is necessary to reduce optical crosstalk, a mechanism whereby a single optical photon can produce multiple avalanches in the SiPM, while keeping good photon detection efficiency. These are, in general, contradicting requirements.In this manuscript, we report on characterization of a variety of SiPM technologies for SST-2M cameras and compare results obtained at different participating institutions. We assess the harmonization of results and discuss the likely performance that will be achieved for the first production cameras.