Active Neutron Detector for direct Dark Matter searches with the DarkSide-50 experiment at Gran Sasso

The existence of dark matter is known from gravitational effects, and although its nature remains undisclosed, there is a growing indication that the galactic halo could be permeated by WIMPs with mass of the order of 100 GeV. Direct observation of WIMP-nuclear collisions in a laboratory detector plays a key role in dark matter searches. However, it also poses significant challenges, as the expected signals are low in energy and very rare. DarkSide is a project for direct observation of WIMPs in a liquid argon time-projection chamber that can meet these challenges. A limiting background for all dark matter detectors is the production in their active volumes of nuclear recoils from the elastic scattering of neutrons. DarkSide-50 is surrounded by a liquid scintillator, doped with Boron, which is used as an active high-efficiency neutron detector. In order to acquire the PMT signal we have developed custom front-end amplifiers with built-in trigger capabilities and a DAQ system based on high-resolution fast digitizers.