Speaker
Description
DarkSide-20k is a direct detection dark matter experiment currently under construction at LNGS in Italy. The central detector is a time projection chamber (TPC) filled with 50 tonnes of liquid low-radioactivity underground argon (UAr). The TPC is surrounded by an additional 32 tonnes of UAr which acts as a neutron veto. The neutron veto plays a vital part in ensuring that DarkSide-20k achieves its goal of being instrumental background free in 200 tonne-years of exposure, by tagging neutrons that interact only once within the central detector. The neutron veto is instrumented with 120 veto photo-detector units (vPDUs) which are custom built 20cm x 20cm arrays containing 384 SiPMs split between 16 tiles that are assembled in the UK and tested in both the UK and Poland. DarkSide-20k is operated at 87K, thus during the production of the vPDUs it was essential to test them at cryogenic temperature.
This talk will focus on the characterization of the DarkSide-20k vPDUs in liquid nitrogen to ensure that they passed photon detection QA/QC standards before they were shipped to LNGS for installation. The three cryogenic test facilities in Edinburgh, Liverpool and AstroCeNT (Poland) conduct these tests for each vPDU and compare to the required standard for the DarkSide-20k neutron veto.