  Silicon-based photosensors (SiPMs) working in the Geiger-mode represent an
elegant solution for the readout of particle detectors working at low-light
levels like Cherenkov detectors. Especially the insensitivity to magnetic
fields makes this kind of sensors suitable for modern detector systems in
subatomic physics which are usually employing magnets for momentum resolution.
In our institute we are characterizing SiPMs of different manufacturers for
selecting sensors and finding optimum operating conditions for given
applications. Recently we designed and built a light concentrator prototype
with 8x8 cells to increase the active photon detection area of an 8x8 SiPM
(Hamamatsu MPPC S10931-100P) array. Monte Carlo studies, measurements of the
collection efficiency, and tests with the MPPC were carried out. The status of
these developments are presented.
