The two telescopes will consist of tens of thousands of optical sensors (photomultipliers), true electronic “eyes”, forming an underwater antenna capable of identifying the light trail (Cherenkov effect) produced in the sea by the rare interactions of neutrinos with the water.

The water will also serve to shield the detector from cosmic radiation.

Given its considerable size, KM3NeT will be the largest monitoring station (oceanographic, geophysical, chemical and acoustic) of the marine environment, as well as a hub for the development of cutting-edge technologies for the exploration of the deep sea.

Both the Italian and the French site host an underwater network of electro-optical cables for the distribution of electrical power and the broadband transmission of the telescopes’ data. A main electro-optical cable is connected to an onshore laboratory and is responsible for transmitting the data in real time.

The neutrino telescope at the Italian site (ARCA, Astroparticle Research with Cosmics in the Abyss) will be dedicated to high-energy neutrino astronomy, while the detector at the French site (ORCA, Oscillation Research with Cosmics in the Abyss) will be dedicated to the study of the fundamental properties of neutrinos.

Both detectors are made up of the same elements, but with a different density of optical sensors. The ARCA detector will have a total volume of about 1 km³ and will comprise 230 detection units, organised into two “blocks”, with a total of more than 4,000 optical sensors. It will be able to study neutrinos coming from astrophysical sources such as supernovae, gamma-ray bursts or active galactic nuclei.

The KM3NeT collaboration is made up of more than 250 researchers, mainly European, who have for years been engaged in the design and construction of the two detectors and of the infrastructure located on the seabed.

Galli e Morelli played a decisive role from the very phase of study and research of the Capo Passero deep-sea site, during the development of the NEMO pilot project (Neutrino Mediterranean Observatory).

Within the KM3NeT project, Galli e Morelli has produced (and is still producing) various mechanical parts commissioned by INFN-LNS, INFN Bari, INFN Naples, CNRS and NIKHEF.

Specifically, Galli e Morelli has already supplied:

• Over 15 LOM structures (Launcher of Optical Modules)
• Over 1,500 mechanical structures internal to the DOMs (Digital Optical Module)
• Over 20 anchoring structures for the strings
• Over 75 titanium containers (Base Container)

The LOMs are spherical launcher vehicles made of an aluminium structure on which the detection units (DUs) are stored and then deployed vertically in the sea.

The base materials used in the construction of the LOMs are profiles in aluminium alloys of type 6082 T6 or 5083 H32 with a thickness between 4 and 6 mm. These profiles are then bent, machined on CNC machines and TIG-welded following specific, certified procedures.

The DOMs consist of a high-pressure-resistant glass sphere 17 inches in diameter, which houses an aluminium structure on which the photomultipliers (PMTs) are mounted, along with the electronics for power distribution, readout, acquisition and transmission of the data.

The internal mechanical structure consists of a series of assembled aluminium parts, entirely machined on CNC machines.

The Base Containers are containers made of titanium Ti 6Al-4V, consisting of a cylinder and two flanges housing a mechanical frame made of aluminium, HDPE, copper and beryllium copper. The Base Containers are designed to house the electro-optical control components of a string.

The cylinder and the flanges are obtained from forged material and then machined on numerically controlled machine tools in order to achieve the extreme precision required by the project.

The Base Containers, closed at the ends by the two flanges and sealed by means of titanium screws and o-rings, are designed to withstand 350 bar for 20 years mechanically, without water infiltration or corrosion.

To guarantee the required specifications, each part is inspected on a CMM machine, and some containers undergo a hydrostatic test at a pressure of 400 bar.

The anchoring structures for the strings serve to carry to the seabed the LOM and the Base Container mounted on them, and are also used to interface with the seabed infrastructure connected to shore.

The anchoring structures consist of a carbon-steel frame on which parts made of HDPE and POM, machined on numerically controlled machine tools, are mounted.

The anchors are designed and built so as to require no maintenance of any kind for a period of at least 15 years in a marine environment at a depth of 3,500 metres and a temperature of 14°C.

All the welds were carried out by highly qualified operators, following specific, certified procedures.