  A Silicon Photomultiplier (SiPM)-based photodetector is being built to
demonstrate its feasibility for an alternative silicon-based camera design for
the Large Size Telescope (LST) of the Cherenkov Telescope Array. It has been
designed to match the size of the standard Photomultiplier Tube (PMT) cluster
unit and to be compatible with mechanics, electronics and focal plane optics of
the first LST camera. Here, we describe the overall SiPM cluster design along
with the main differences with respect to the currently used PMT cluster unit.
The fast electronics of the SiPM pixel and its layout are also presented. In
order to derive the best working condition for the final unit, we measured the
SiPM performances in terms of gain, photo-detection efficiency and cross-talk.
One pixel, a unit of 14 SiPMs, has been built. We will discuss also some
preliminary results regarding this device and we will highlight the future
steps of this project.
