The ArDM (Argon Dark Matter) Experiment aims at direct Dark Matter detection based on a ton-scale liquid argon (LAr) double-phase time projection chamber (TPC). The experiment is located at the Laboratorio Subterráneo de Canfranc (LSC).
The ArDM-1t detector is the largest two-phase liquid argon detector for Dark Matter Searches in the world.
Astronomical observations give strong evidence for the existence of non-luminous and non-baryonic matter, presumably composed of a new type of elementary particle. A possible candidate is the Weakly Interacting Massive Particle (WIMP). If they exist, WIMPs should form a cold thermal relic gas, which could be detected via elastic collisions with nuclei of ordinary matter. The detection of these WIMPs is based on the capability of measuring the recoils of target nuclei with kinetic energy in the range of 10-100 keV. The signal is therefore quite elusive and is expected to be a rare event given the weak coupling between WIMPs and ordinary matter.
Noble liquid detectors using Xenon or Argon can efficiently act as targets for Weakly Interacting Massive Particles (WIMP) detection. Xenon or Argon provide a high event rate because of their high density and high atomic number and large target masses are readily conceivable. They have high scintillation and ionization yields because of their low ionization potentials. Both scintillation and ionization are measurable and can be used to very effectively discriminate between nuclear recoils and gamma/electron backgrounds. The use of noble liquid gases to detect WIMP dark matter is currently the subject of intense R&D carried out by a number of groups worldwide. In these detectors, one relies on the simultaneous detection of the ionization charge and of the scintillation light produced during a nuclear recoil event. A main subject for any such detector is the method of the readout for the ionization and scintillation.
Elastic scattering of Dark Matter particles (hypothetical WIMPs) off target argon nuclei is measurable by observing photons from scintillation and free electrons from ionisation, which are produced by the recoiling nucleus interacting with neighboring atoms. The ArDM detector is designed to measure both signals in its double-phase (liquid-vapour) TPC operation mode.