Status of the Development of a Silicon Photomultiplier based camera module for the Large Size Telescopes of the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) will observe the very high energy gamma-ray sky (20 GeV - 300 TeV) with unprecedented performance in terms of sensitivity, angular and energy resolution. CTA will be deployed in two sites, one in each hemisphere for full-sky coverage. In each site four Large Size Telescopes (LSTs) of 23 m diameter dish will cover the lowest energy range (20 GeV - 200 GeV). In Autumn 2018 the first LST has been inaugurated in the Canary Island of La Palma and has entered the commissioning phase. Its focal plane is composed by 265 modules, each one hosting 7 photomultiplier tubes (PMTs) with 1.5 inches diameter pupil.Thanks to their features, in particular their high photon detection efficiency, tolerance to high illumination level and small pixel size, Silicon Photomultipliers (SiPMs) are already the baseline photosensors for the dual mirror telescopes and the single mirror small telescopes of CTA. On the other hand the application of such devices in focal planes with larger plate scales is still challenging, but could provide improvements in the performance of the telescopes.For this reason we are developing a module for the LST camera, with each PMT replaced by a SiPM array whose outputs are summed into a single signal, read by the standard LST electronics. We present here the status of the project and the preliminary measurements obtained with our prototype.