Speaker
Description
DarkSide-20k (DS-20k) is a direct dark matter search experiment under construction in Hall C at Laboratori Nazionali del Gran Sasso (LNGS), L’Aquila, Italy. It aims to probe the cross-section between argon nuclei and Weakly Interacting Massive Particles (WIMPs), one of the most promising dark matter candidates, down to 10$^{-48}$ cm$^2$. DS-20k will feature a double-phase time projection chamber (TPC) with a fiducial target of 20 tonnes of the so-called underground argon with a specific activity of 0.066 mBq/kg. It is extracted from the Urania mine, Colorado, where the rock overburden has prevented cosmogenic activation of isotopes, especially $^{39}$Ar, responsible for a specific activity of 1 Bq/kg in atmospheric argon. An extensive material screening carried out from the DarkSide collaboration allowed to reach an expected radiogenic background of 0.1 events in a 200 ton∙year exposure after analysis. An additional irreducible background of 3.5 coherent neutrinos, indistinguishable from WIMP-nucleus scattering, is foreseen. Electron recoils from ionizing particles ($e^-$, $\gamma$, $\alpha$) are clearly identified by pulse shape discrimination, whose rejection power exceed 10$^8$ in liquid argon, making DS-20k an almost background-free experiment. High-quality silicon photomultiplier (SiPM) arrays, grouped in two optical planes of 10.5 m$^2$ each, will detect the light emitted in the two phases of the TPC. Their production, now at regime, is ongoing in Nuova Officina Assergi (NOA) at LNGS, where 5 × 5 cm$^2$ SiPM tiles are assembled and tested also in liquid nitrogen at a rate of 40 per day. 16 of them are mounted in the so-called Photo Detection Units (PDUs) to tesselate the optical planes. PDUs are validated in their performance in liquid nitrogen at Photosensor Test Facility (PTF) in Naples. Test results and production throughputs of NOA and PTF will be presented and discussed.
| Main Contribution topic | Direct detection |
|---|---|
| Secondary contribution topic | Instrumentation for Dark Matter |