The hunt for neutrinos — once called “the most tiny quantity of reality ever imagined by a human being” — is one of the most exciting areas of research in particle physics. Scientists believe that these tiny, exotic subatomic particles — billions of which are passing unimpeded through your body every second — can provide us invaluable information about some of the least understood events and phenomena in the universe, including black holes and dark matter.
In order to detect these ghostly particles, scientists need massive and extremely sensitive detectors placed in areas far removed from cosmic rays and other disturbances. This is the reason why the IceCube Neutrino Observatory has thousands of detectors buried deep within the Antarctic ice, and why the KM3NeT (an acronym for Cubic Kilometre Neutrino Telescope) collaboration wants to construct the world's largest neutrino detector in the depths of the Mediterranean Sea.
“The weak interaction between neutrinos and normal matter is a blessing and curse. It makes detecting them notoriously difficult, which is why you need a giant detector,” KM3NeT spokesman Maarten de Jong, who has been involved with the project since 2006, said in a statement. “It turns out that the deep waters in the Mediterranean are ideal. These natural waters come for free, are very transparent to the Cherenkov light, and sufficiently accessible to allow the deployment of strings of photo-sensors.”
Cherenkov light is the bluish electromagnetic radiation produced when a charged particles move through a medium at a speed faster than the speed of the light in the medium. (Although nothing can travel faster than the speed of light in vacuum, it is possible for a particle to exceed the speed of light in other media, including water).
If a neutrino interacts with an atomic nucleus, it produces charged particles that cause Cherenkov light to be emitted, which can then be detected using sensitive photo-sensors.
According to a detailed report published in the latest edition of the Journal of Physics G: Nuclear and Particle Physics , the KM3NeT detectors will consist of a number of vertical strings, with spherical glass modules attached to them. Each sphere would be tethered to a string of others with cables, and each module would contain sensors that would search for neutrinos.
“The KM3NeT collaboration has developed what it believes is a cost-effective plan for building out this research infrastructure at the bottom of the sea,” the collaboration said in the statement. “The phased rolled-out will consist of three so-called building blocks, where each building block comprises 115 strings of 18 optical modules.”
The collaboration has so far raised 31 million euros, and the researchers believe that the telescope, which may be completed by 2020, would cost another 95 million euros.
“If we observed a neutrino [source] in the sky, we’re talking about a whole new field of research,” De Jong told Popular Science. “For me it would be heaven.”