A part of the Pacific Ocean could be turned into a huge neutrino detector, scientists have proposed in a new paper. The project, dubbed by the authors as the Pacific Ocean Neutrino Experiment (P-ONE), would span several kilometers across to find the most energetic neutrinos in the universe.
For this, the scientists suggest finding a very isolated part of the ocean, building “wires” of photodetectors and sinking them to a depth of more than 2 kilometers in the sea floor. Weights for floats, they’d hang around like giant seaweed.
There would be seven groups of 10 strings, each with 20 optical elements. The result would be 1,400 photodetectors distributed over a large area, enough to provide much more coverage in detecting neutrinos than the IceCube Neutrino Observatory, installed deep in Antarctica.
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How to detect neutrinos
Known as “ghost particles,” neutrinos are difficult to detect because they barely interact with matter. This means that wherever he goes, he will not leave any “footprints”.
At this very moment, thousands of neutrinos emitted by the Sun pass through your body, and you don’t even notice. During their lifetime, probably only a few dozen — to be optimistic — will interact with their molecules, causing them to react (harmless to their organism).
These rare interactions are the only way to detect a neutrino and find out something about it. They can happen in any type of material, but scientists prefer to use pure water in the detectors, because then the data obtained by the sensors will be free from interference.
The IceCube, for example, consists of a cubic kilometer of ice at the South Pole, with dozens of Eiffel Tower-sized receiver wires sunk beneath the surface. When some neutrino reacts with water molecules in ice, it can create particles like electrons, muons or taus, which in turn can emit a type of energy called Cherenkov radiation.
This Cherenkov radiation arises whenever a charged particle travels through a medium faster than the speed of light in that same medium. This is what scientists try to observe in the detector. When radiation is emitted, the hundreds of photodetectors read the data.
Thanks to the purity of the water in the detectors, scientists can pinpoint the direction, angle and intensity of the flash very precisely, as well as discover what type of neutrino interacted there and where it came from.
The ocean neutrino detector
In the P-ONE proposal, things would be more complicated than stable ice below the surface of Antarctica. For example, the sea will cause the photodetector wires to move constantly, due to the movement of the water and the tides.
Plus, the Pacific Ocean doesn’t exactly have the purest water on the planet. It contains salt, plankton and debris left behind by fish, for example. This will change the behavior of light from Cherenkov radiation.
To get around the situation, scientists would have to constantly calibrate the readers, adjusting all the variables and canceling out the “noise” that will be obtained when the sensors scan the Cherenkov light. If this is implemented correctly, it will be possible to track the neutrinos.
Of course, the team behind the project is aware of the difficulties and is already working to overcome them. They currently have plans to build a small proof-of-concept demonstration of the detector. The study was published on the arXiv prepress server.
