Design, construction and commissioning of the PandaX-30T liquid xenon management system

The PandaX-30T is a proposed next-generation experiment to study dark matter and neutrinos using a dual-phase time projection chamber with & SIM; 30 tons of liquid xenon. An innovative xenon handling subsystem of the PandaX-30T, the First-X, is described in this paper. The First-X is developed to handle liquid xenon safely and efficiently, including liquefying and long-term storing xenon without losses or contamination, and transferring cryogenic liquid xenon between the storage module and the detector safely and effectively without venting out. The storage module of the First X is five specially designed double-walled cylindrical vessels (Center Tanks) equipped with three heat exchangers each for pressure and temperature regulation. Each Center Tank is designed with a vacuum and multi-layer insulation and a maximum allowable working pressure of 7.1 MPa, allowing 6 tons of xenon to be stored at 165-178 K at 0.1-0.2 MPa in the liquid phase or up to 300 K and up to 6.95 MPa in the supercritical phase. High-pressure storage (> 0.2 MPa) only occurs in case of longterm detector shutdown or lack of nitrogen, ensuring no-loss storage of 6 tons of xenon in the range 178-300 K. In this paper, the thermophysical performances of the First-X and innovative scenario to conduct non-vented cryogen transportation were experimentally conducted and reported using liquid argon. The non-vented cryogenic liquid filling and pump-assisted cryogenic liquid recovery have been conducted with liquid argon at a mass flow rate of 1390 kg/h, corresponding to a xenon mass flow rate of 2140 kg/h. Compared with the PandaX-4T, the transportation of xenon between the detector and the storage module is conducted in the liquid phase rather than in the gaseous phase, and the filling rate (fill the detector) and the recovery rate (recover xenon from the detector) are increased by approximately 50 times and 30 times, respectively.