Liquid-phase purification for multi-tonne xenon detectors

Abstract: As liquid xenon detectors grow in scale, novel techniques are required to maintain sufficient purity for charges to survive across longer drifts. The Xeclipse test facility at Columbia University was built to test the removal of electronegative impurities through cryogenic filtration powered by a liquid xenon pump, enabling a far higher mass flow rate than gas-phase purification through heated getters. In this paper, we present results from Xeclipse, including measured oxygen removal rates for two sorbent materials, which were used to guide the design and commissioning of the XENONnT liquid purification system. Thanks to this innovation, XENONnT has achieved an electron lifetime greater than 10 ms in an 8.6 tonne total mass, perhaps the highest purity ever measured in a liquid xenon detector.