Liquid argon is used as the target for neutrino experiments and direct dark matter searches.
The interaction of a hypothetical WIMP particle with the argon nucleus produces scintillation light that is detected by photomultiplier tubes.
Two-phase detectors also use argon gas to detect the ionized electrons produced during the WIMP-nucleus scattering.
As with most other liquefied noble gases, argon has a high scintillation light yield (~ 51 photons/keV[33]), is transparent to its own scintillation light, and is relatively easy to purify.
Compared to xenon, argon is cheaper and has a distinct scintillation time profile which allows the separation of electronic recoils from nuclear recoils.