The nEXO cryogenics and fluid handling and purification systems

The nEXO experiment will search for neutrinoless double beta decay in ¹³⁶Xe, reaching a half life sensitivity beyond 10²⁸ years. The experiment will consist of 5 tons of liquid Xe enriched to 90% in the isotope ¹³⁶Xe, which will be used as both the decay source and detection medium. In order to reach the low background requirement, nEXO will utilize a dual fluid system based on the successful implementation in EXO-200. The liquid Xe is contained in a thin, high-purity copper vessel surrounded by a refrigerant, HFE-7000, to transfer the pressure to a dual walled carbon-composite cryostat. This allows isolation of the detector from radiogenic backgrounds with a minimum amount of material near the detector. The conceptual design of the fluid and cryogenic plants for the circulation, cooling, and pressure maintenance of the fluids, as well as the state-of-the-art, in-situ fabrication of the cryostats will be presented.