Gammas PMTs Gas Nuclear Recoils Secondary scintillation Ionization electrons E-Field Liquid Secondary vs primary light signal distributions measured in a 2.3 litres argon prototype. Nuclear recoils can be easily identified. Primary scintillation Interaction WARP (Wimp ARgon Programme) • Search for Dark Matter in the form of WIMPs best candidate lightest SUSY particle • New technique able to provide the sensitivity required to span the parameters space currently allowed in the context of the SUSY models (hundred tons year) LAr TPC technology (see ICARUS) • WIMP interactions produce nuclear recoils (E < 100 keV). They can be discriminated from g and b signals (radioactivity) by the relative amount produced atomic excitation (scintillation) and ionization. • for nuclear recoils, ionization is heavily suppressed Technique based on the simultaneous detection of primary scintillation and ionization in LAr. Ionization electrons are drifted in the LAr and then extracted in the gas phase by an electric field. They are accelerated in the gas to produce a second light signal. The relative amplitude of the two signals allows to discriminate WIMP signals from background.