Neutrino Extended Submarine Telescope with Oceanographic Research

NESTOR is Europe's first collaborative effort for a deep sea high energy neutrino telescope. It is a tower of 12 hexagonal floors of 32 m diameter with highly sensitive photomultipliers of large surface area at the corner points (168 in total for phase 1). Each floor is located above the next at vertical intervals of 20 m. NESTOR will detect the Cherenkov radiation produced by muons in a large volume of transparent matter, water. For neutrinos with energy less than a few TeV, one must look for muons that are upcoming, ie their parent neutrinos have traversed the Earth. The muons are produced by neutrinos or by atmospheric interactions of cosmic rays. Though the muon is a very penetrating particle and can traverse hundreds or even km of water, its range in rock is comparatively short. For neutrinos with energies larger than a few TeV, one can look for downcoming muons because there are comparatively few cosmic rays at these extreme energies. This is the reason for going deep underwater; for neutrino energies less than a few TeV, the few kilometers of water above the detector act as a shield against cosmic rays and reduce this cosmic rate caused background by a factor of one million. NESTOR will investigate a wide range of physics topics such as: 

• High-energy neutrino astronomy, namely detecting neutrinos produced by galactic X-ray binaries, black holes or extragalactic sources, such as the active galactic nuclei (AGNs) et.c
• Neutrinos that are produced from the annihilation of dark matter particles, SUZY particles et.c.
• Neutrino oscillations (i.e. weighting of the neutrinos), using neutrinos produced in the atmosphere. 
• Neutrino oscillations, using neutrinos from a particle accelerator.

• the NESTOR photomultipliers for the detection of Cherenkov photons in the water, as well as bioluminescence, nephelometry, 
• the Titanium Spheres which house the electronics and the Controls system, 
• the calibration system for the photomultipliers that also monitors the light transmissivity of the water, 
• communication and data transmission systems, using optical fibers, with the shore station, 
• LAERTIS

There are only four neutrino related deep-water experiments in the world; AMANDA in the South Pole, BAIKAL in Baical Lake, NESTOR of S.W. of Peloponnese and ANTARES off Marseilles. NESTOR takes advantage of the unique fact that is deployed near the deepest part in Europe (depth up to 5200m). At a distance of about 14 km off the shore, at water depth of 4000m there is a fairly large abyssal plane that is perfectly suited for several deep-sea installations. In addition, the completely sheltered Bay of Navarino is very close to this offshore location (18 nautical miles) and has maximum water depth of about 60m. Further, within a distance of few miles from the deep location, there are three natural harbours (Methoni, Port Loggo (in the island of Sapienza) and Schiza)The small city of Pylos lies at the entrance of the bay. This combination of a protected, comparatively shallow bay for preliminary test operations with a deep-water site so close to shore seems to be optimal for the NESTOR research work. In fact this is a unique site in Europe. The most important requirements for a deep underwater neutrino telescope are: Clear water (i.e. water with small light attenuation coefficient), deep site (to filter out the atmospheric muons), proximity to the shore (to use a short electro-optical cable to power the detector and transfer the data to shore), low velocity underwater currents (for minimal mechanical stress on the detector), flat and wide sea bottom (to permit further expansion) and stable geological characteristics (for long life time of the detector) PLUS proximity to harbours for safety and easy operations at sea. In short the unique advantages that the selected site provides are: 

• Proximity of the deep sea to the shore
• The existence of a data highway with an electro-optical cable 
• The existence of the bay of Navarino for continuous testing of components. 
  

The selected site fulfils these requirements. We have designated as the NESTOR/LAERTIS site, a location with co-ordinates 36*37.5'N, 21*34.5'E, in the middle of the deep underwater basin (called the NESTOR basin) which has a gentle slope.