are generated by the moving atom and detected, often with PMTs. Experiments such as DEAP at SNOLAB and DarkSide at the LNGS instrument a very large target mass of liquid argon for sensitive WIMP searches. ZEPLIN, and XENON used xenon to exclude WIMPs at higher sensitivity, with the most stringent limits to date provided by the XENON1T detector, utilizing 3.5 tons of liquid xenon. Even larger multi-ton liquid xenon detectors have been approved for construction from the XENON, LUX-ZEPLIN and PandaX collaborations. Crystal scintillators – Instead of a liquid noble gas, an in principle simpler approach is the use of a scintillating crystal such as NaI(Tl). This approach is taken by DAMA/LIBRA, an experiment that observed an annular modulation of the signal consistent with WIMP detection (see ). Several experiments are attempting to replicate those results, including ANAIS and DM-Ice, which is codeploying NaI crystals with the IceCube detector at the South Pole. KIMS is approaching the same problem using CsI(Tl) as a scintillator. Bubble chambers – The PICASSO (Project In Canada to Search for Supersymmetric Objects) experiment is a direct dark matter search experiment that is located at SNOLAB in Canada. It uses bubble detectors with Freon as the active mass. PICASSO is predominantly sensitive to spin-dependent interactions of WIMPs with the fluorine atoms in the Freon. COUPP, a similar experiment using trifluoroiodomethane(CF3I), published limits for mass above 20 GeV in 2011. The two experiments merged into PICO collaboration in 2012. A bubble detector is a radiation sensitive device that uses small droplets of superheated liquid that are suspended in a gel matrix. It uses the principle of a bubble chamber but, since only the small droplets can undergo a phase transition at a time, the detector can stay active for much longer periods. When enough energy is deposited in a droplet by ionizing radiation, the superheated droplet becomes a gas bubble. The bubble development is accompanied by an acoustic shock wave that is picked up by piezo-electric sensors. The main advantage of the bubble detector technique is that the detector is almost insensitive to background radiation. The detector sensitivity can be adjusted by changing the temperature, typically operated between 15 °C and 55 °C. There is another similar experiment using this technique in Europe called SIMPLE. PICASSO reports results (November 2009) for spin-dependent WIMP interactions on 19F, for masses of 24 Gev new stringent limits have been obtained