The ARIA project

Author: Arianna Steri

The ARIA project

The ARIA project is located within the Monte Sinni mining complex, a former coal mine in southwestern Sardinia (Carbosulcis S.p.A.), Italy. It consists of a 350-meter-tall cryogenic distillation column, housed in a disused mining shaft, with the purpose of purifying underground argon extracted from Colorado, pre-treated through the Urania project. In fact, the purified argon will play a key role as a scintillator in the DarkSide-20k dark matter detector. The Urania facility in Colorado extracts and pre-purifies the argon, removing impurities like methane and oxygen. The final purification is done via cryogenic distillation at the ARIA facility.

Cryogenic Distillation

Cryogenic distillation stands out among isotope separation methods for its high efficiency, purity, scalability, and ability to handle large quantities of material. It involves cooling gases to liquid form, exploiting volatility differences between substances for separation. The key steps are:

  1. Vaporization: Gas is heated at the bottom of the column.
  2. Partial Condensation: As it rises, the gas cools, causing heavier isotopes to condense first.
  3. Evaporation-Condensation Cycles: Through repeated cycles, lighter isotopes concentrate at the top, and heavier ones at the bottom.

Because isotopic differences in volatility are small, the process requires tall columns and precise control for effective separation.

Figure 1: Simplified scheme of the ARIA plant [1].

Plant Details

The ARIA distillation column, constructed from stainless steel, consists of 30 modular sections, each 12 meters tall and weighing 2.5 tons. Inside, a structured packing enhances heat exchange and separation between gas and liquid phases. Fabricated by an Italian company, tested at CERN, and now stored in the mine’s warehouses, the column is awaiting installation in Shaft 1.

Figure 2: Aria plant top module, ready for the installation.

Phase 0 – Prototype

While waiting for full installation, a test column was assembled using three modules—top, bottom, and middle. Tests with nitrogen and argon successfully demonstrated isotope separation, resulting in two scientific publications (see references at the bottom of this page, as well as our Dissemination page).

Figure 3: The prototype Aria plant, Seruci-0, in the Laveria building of the Carbosulcis mine, Nuraxi-Figus site, viewed from the basis of the column.

Further Applications

Beyond dark matter research, ARIA will serve as a leading center for stable isotope production, especially for medical uses. Isotopes like 13-Carbon, 15-Nitrogen, and 17-Oxygen, critical for MRI and PET scans, are rare but can be concentrated using ARIA’s technology. These isotopes possess unique magnetic property: they contain a sort of permanent magnet within their nucleus, making them highly sensitive for medical imaging. This burgeoning market, currently valued at nearly a billion euros, will benefit greatly from ARIA’s increased isotope production capabilities.

Moreover, ARIA will enable pilot studies for isotopes relevant to neutrino research, such as 76-Gemanium, 82-Selenium, and 136-Xenon, contributing to scientific advances in fundamental physics at INFN’s Gran Sasso Laboratory.

References

[1] Eur.Phys.J.C 81 (2021) 4, 359   

[2]Eur.Phys.J.C 83 (2023) 5, 453