The Laboratoire Souterrain de Modane , LSM, is a French underground laboratory located in the French-Italian border, near the middle of the Fréjus highway tunnel between Modane (France) and Bardoneccia (Italy). The LSM, with a rock coverage of 1700 m, is the deepest underground laboratory in Europe.
Excavated in 1981, the laboratory has been opened on December 1982 to host a single experiment, a 900 ton detector dedicated to the search of the decay of the proton. The size of the cavern was adjusted to the size of the planned experiment, namely a hall of about 30 m long by 10 m wide by 10 m high, plus three additional smaller rooms. Then the experiment was dismounted in 1988 and progressively the lab hosted more and more activities requiring protection against cosmic rays.
The laboratory, jointly operated by CEA (Commissariat à l'Energie Atomique) and CNRS (Centre National de la Recherche Scientifique), has an external building with offices and workshops in the Modane area. A permanent staff of about 10 people ensures the daily functioning, provides a substantial contribution to the installation and running of the various experiments and ensures proper safety conditions.
Currently the lab is sheltering experiments in particle and astroparticle physics -dark matter and double beta decay searches, super heavy elements search- and very sensitive Germanium detectors for the measurement of extremely low radioactivity levels.
The experiment dedicated to the dark matter search is EDELWEISS, a French, German and Russian collaboration. They use Germanium crystals aiming at the detection of a new type of elementary particles, the WIMPs which could constitute the dark matter of our Galaxy. The detectors measure at the same time the deposited heat and the number of electrons produced when a particle strikes one of its nuclei. These two measurements allow to distinguish the very small signal expected from the WIMPs from the dominant radioactive background. A tiny temperature variation of a millionth of degree can be measured thanks to the fact that the detectors are kept at 20 mK (-273,13 ° C).
NEMO (France, Russia, Czeck Republic, UK, Finland, USA and Japan) and TGV (Russia, France and Slovakia) are detectors for double beta decay searches. As this type of decay is very rare, the detectors have to be protected from all sorts of parasites in order to be able to detect the interesting signal. NEMO is installed within a shielding made of iron, water and wood with a total weight of more than 200 tons. All materials have been carefully selected for having very low radioactivity levels. As a result, the residual activity of the 200 tons of NEMO is less than that of a human body!
The search for the presence of super heavy elements in nature is performed by SHIN, installed in the lab in November 2004 and built by a Russian team from Dubna.
In the last years a strong demand to measure lower and lower radioactivity rates emerged from several fields. At the LSM, 13 Germanium detectors belonging to 5 different institutions are operated. Protected from cosmic rays by the thick rock above the laboratory, these detectors have background levels 100 to 1000 times lower than when they are not underground. The detectors are used for a wide range of applications: selection of materials with low radioactivity for fundamental physics experiments, monitoring of environmental radioactivity levels and various other applications concerning climatology, oceanography, and dating, in particular of Bordeaux wines.