Purification of Argon via Distillation with Aria and Purity Monitoring for Dark Matter Searches

The search for dark matter is one of the most promising fields of physics research. Approximately 80% of the universe’s matter is classifiable as non-baryonic dark matter. So far it has not yet been directly detected. To verify the existence of WIMPs, which are hypothesized to be dark matter particles, various methods, including direct interactions with ordinary matter, are being pursued. One of the most commonly used materials for WIMP detection is argon, forming the active target of the already completed DarkSide-50 experiment and the subsequent DarkSide-20k experiment. The latter will employ 20 tonnes of ultra-pure liquid argon to investigate interactions with dark matter. In this thesis, I’ve analyzed the data obtained from DarkSide-50 to measure the consequences of potential contaminants in argon and their influence on the measurements. This method will allow us to establish a threshold for contaminants, mainly nitrogen and oxygen, below which the measurements have minimal or no impact. The argon that is going to be used by DarkSide-20k, called Underground argon, will be extracted by the Urania facility in Colorado. To ensure that it attains the requisite level of purity, it must undergo chemical purification through cryogenic distillation. This constitutes the primary goal of the Aria project, the central focus of this thesis. Furthermore, a crucial aspect is the capability of the Aria distillation column to separate isotopes, which consequently can contribute to achieving radiopurity, in particular concerning the isotope 39Ar inside the argon extracted from the Urania facility. The purpose of Aria extends beyond the DarkSide-20k provision of argon. The Underground argon will also be provided for the veto system of the LEGEND-1000 experiment for neutrino-less double beta decay search. Moreover, Aria will be used for the isotopic enrichment of germanium for future expansion of LEGEND-1000, as well as the production of isotopes with various applications in different fields, such as 13C, 18O, 17O, 15N.