lXe

Liquid xenon (LXe) is the cryogenic liquid form of the noble gas xenon. In scientific literature it is commonly abbreviated as LXe and used as a detection medium in a range of particle- and nuclear-physics experiments. Its combination of high density, high atomic number, and favorable optical and electronic properties makes it well suited for detecting scintillation light and ionization electrons.

Physically, xenon becomes a dense liquid when cooled to about 165 K at standard pressure, with a melting point near 161 K. LXe has a relatively high density (around 3 g/cm3) and a high atomic number (Z = 54), which contributes to strong interaction probabilities for gamma rays. The liquid emits scintillation light predominantly in the vacuum-ultraviolet range near 178 nm when excited, and it also yields free electrons that can be collected under an electric field. LXe detectors commonly operate as two-phase time projection chambers, where prompt scintillation (S1) is followed by delayed electroluminescence (S2) produced in the gas phase above the liquid.

Detection and applications. LXe is used extensively in dark matter searches and rare-event experiments because of its scalability, radiopurity, and the ability to measure both scintillation and ionization signals for event characterization. Leading experiments include XENON1T, XENONnT, and LUX-ZEPLIN (LZ). Beyond dark matter, LXe has applications in gamma-ray and neutrino detectors and has been explored for medical and imaging technologies.

Purity and handling. The performance of LXe detectors depends on ultra-clean, impurity-free xenon, as electronegative contaminants quench scintillation light and capture drifting electrons. Purification is achieved by continuous gas-phase circulation through getters and cryogenic filtration, with strict material selection to minimize radioisotopic background. Safety considerations include the cryogenic nature of LXe and the risk of oxygen displacement in enclosed spaces.