Speaker
Description
Liquid argon is an excellent target for direct dark matter detection thanks to its scintillation and ionization responses combined with strong pulse-shape discrimination (PSD). The DarkSide-20k experiment, now under construction in the Gran Sasso National Laboratory (LNGS), Italy, will use a liquid argon dual-phase time projection chamber aiming at a background-free search for Weakly Interactive Massive Particles (WIMP). The use of argon sourced from the atmosphere would limit the size of such a detector by the presence of 39Ar, a 𝞫-emitter of cosmogenic origin whose activity poses significant background and pile-up concerns for a multi-tonne scale detectors. To mitigate this background the Global Argon Dark Matter Collaboration (GADMC) has developed a dedicated supply chain for the production of radiopure argon extracted from the underground, hence naturally shielded from cosmic rays and highly depleted in 39Ar.
The first phase of this program is the Urania extraction facility located in Colorado, USA. Urania is designed to obtain the underground argon (UAr) from the active gas wells. The plant is scaled to extract 121 tonnes of UAr at a purity of 99.99%, providing the raw target mass required for the forthcoming DarkSide-20k detector. To achieve ultimate detector-grade quality, the UAr is then transported to the Aria facility located in a mine shaft in Sardinia, Italy. Aria hosts a 350 meter tall cryogenic distillation column. It is designed to chemically purify the UAr to a purity exceeding 99.9999%. Together, Urania and Aria, represent a pioneering industrial scale effort in radiopure material production enabling the next generation rare-event detection technology. Additionally Aria can act as an active isotopic separation plant and has demonstrated the separation of stable argon isotopes (36Ar, 38Ar, and 40Ar). This unlocks broader enrichment opportunities for rare-event searches (using 136Xe, 76Ge) and medical diagnostics (with 18O).