Thermal Simulation for nEXO Cryostat Cooling R&D

The search for neutrinoless double-beta decay probes new physics of the unknown neutrino mass discovered by oscillation experiments. The planned nEXO experiment wil have a half-life sensitivity of 10²⁸ years, covering the inverted mass hierarchy for mediation by light Majorana neutrinos. nEXO utilizes 5 tons of xenon enriched in isotope 136 arranged in a liquid time projection chamber immersed in an HFE thermal bath. The cryogenic cooling is planned via active recirculation of the HFE to an external heat exchanger. This project considers an alternative temperature setpoint maintenance strategy using thermosyphons to cool directly the HFE and motivated by the experience of the EXO-200 experiment and the approach of large liquid xenon dark matter experiments. Early thermal simulation results will be presented.