Wikipedia
The ArDM (Argon Dark Matter) Experiment is a particle physics experiment based on a liquid argon detector, aiming at measuring signals from WIMPs (Weakly Interacting Massive Particles), which probably constitute the Dark Matter in the universe. Elastic scattering of WIMPs from argon nuclei is measurable by observing free electrons from ionization and photons from scintillation, which are produced by the recoiling nucleus interacting with neighbouring atoms. The ionization and scintillation signals can be measured with dedicated readout techniques, which constitute a fundamental part of the detector.
In order to get a high enough target mass the noble gas argon is used in the liquid phase as target material. Since the boiling point of argon is at 87 K at normal pressure, the operation of the detector requires a cryogenic system.