NESTOR - Neutrino Extended Submarine Telescope with Oceanographic Research

{\bf NESTOR} is a deep-sea neutrino telescope that is being deployed in the Mediterranean off the south-west coast of the Peleponnese in Greece. Neutrinos, when they interact in the earth below or in the seawater around the detector, produce muons that can be observed by the Cherenkov radiation, which they emit. At an operating depth of 4000 metres, the detector is effectively shielded from muons produced in atmospheric interactions. {\bf The site:} A major feature of the Ionian Sea floor is the Hellenic Trench, the deepest in the Mediterranean, which in places exceeds 5000 meters. It runs close to the western coast of the Peleponnese and is protected on its western side by the submarine Eastern Mediterranean Ridge. It is far from big city pollution or the effluent of major river systems flowing into the Mediterranean and is protected from deep-water perturbations.\\ The NESTOR site is located on a broad plateau some 8 $\times$ 9 kilometres in area on the eastern side of the Hellenic Trench at a mean depth of 4000 meters.\\ The centre of the plateau (Site coordinates: 36$^{o}$ 37.5'N, 21$^{o}$ 34.6'E) is only 7.5 nautical miles from land and 11 nautical miles from the port of Methoni at the south-western tip of the Peleponnese mainland. Detectors deployed in this area can be connected to the Methoni shore station by modest lengths of electro-optical cable. The water transmissivity at the site is 55 $\pm$ 10 meters at 460 nanometers wavelength, water currents are a few cm/sec and temperatures are constant at 14$^{o}$C: there is no evidence of any submarine rock falls for the last 40000 years. {\bf Infrastructure:} The NESTOR Institute is located in the town of Pylos some 11 km by road north of Methoni: Pylos lies on the Bay of Navarino which has port facilities for small boats and ocean going vessels. It is 280 km from Athens and 45 km from Kalamata, a major port and industrial city with an international airport.\\ The Institute building houses offices, laboratories, control centre and conference room. Mechanical workshops, hyperbaric test facilities and warehousing are located nearby.\\ A research vessel, several boats and a small deployment platform are already in use: a delta-shaped (55 m side), ballasted platform for deep-sea deployments will be delivered in 2002.\\ A permanent underwater test facility on the far side of the bay is connected to the Institute by a 4,5 km electro-optical submarine cable. All equipment is operated here before being deployed at the deep-sea site. {\bf The detector:} A full NESTOR tower will consist of 144 optical modules fixed on a semi-rigid structure which ensures good geometrical location: this is important in order to reconstruct the interaction point and direction of incoming neutrinos. The optical module, which is capable of operating in the sea at depths of up to 5000 meters, is based on a 15" phototube with good single photoelectron resolution and spectral response from 300 - 650 nanometers. The basic element of the detector is a hexagonal floor (star) of 32 metre diameter, made in titanium or aluminium. The floor electronics are housed in a 1 m $\O$ pressure vessel, mounted in a central casing. Six lightweight lattice girder arms are attached to the central casing: the elements are of 5 metres length: normally 3 elements are used per arm but the modular construction allows different detector configurations if required. Two optical modules (OM) are installed at the end of each arm, facing upwards and downwards. Using the OM's in pairs gives 4$\pi$ coverage, enhances the discrimination between upward and downward going particles and improves background rejection. A full tower will consist of 12such floors, spaced vertically by 30 meters: LED modules are installed between floors for calibration.\\ The floors are connected to a sea bottom unit, containing the anchor, the junction box/fan-out for the electro-optical cable from shore and a number of environmental monitoring packages.\\ All electrical and optical connections between the floors and the sea bottom unit are made in the air at the sea surface at the time of deployment. A first cable is laid from shore and is operating with a sea bottom unit at 4100 metres.\\ The collaboration has already demonstrated its ability to deploy equipment packages to a depth of 4000 metres, operate them and recover them several months later. {\bf Physics reach:} A tower represents a 300 kiloton detector with a threshold of 5 GeV for low energy neutrino studies and 10'000 m$^{2}$ sensitive area at 10 TeV threshold for neutrino astronomy.\\ A hexagon of 6 such towers, spaced at 150 m around the initial tower, would be equivalent to $>$ 40 Megaton detector. It would have a sensitive area of 100'000 m$^{2}$ for 10 TeV neutrinos giving a uniform 4$\pi$ angular response with better that 0.1 degree resolution. The principal physics topics to be covered are:- \begin{itemize} \itemsep 0pt \item Neutrino astronomy , both galactic and extra-galactic \item Particle physics beyond the Standard Model - Massive dark matter particles captured in the Earth, Sun or galactic centre - Multiple W, Z production etc. \item Atmospheric neutrino oscillations - Long base-line neutrino oscillations \item Magnetic monopoles - Supernova detection \item The Unexpected \end{itemize}