The discovery of high-energy astrophysical neutrinos in 2013 marked the birth of a new field of knowledge - high-energy neutrino astrophysics. This happened when the IceCube detector, located at the South Pole in the Antarctic ice, first detected neutrinos with energies above 1000 TeV. To date, the IceCube experiment has recorded over 100 high-energy astrophysical neutrinos in the Southern Hemisphere. To detect neutrinos from the entire celestial sphere, a gigaton-scale neutrino telescope in the Northern Hemisphere is required. Therefore, since 2015, the BAIKAL-GVD second-generation neutrino telescope is being actively built on Lake Baikal.
The Baikal Neutrino Telescope under construction is a unique scientific facility and, along with the IceCube, ANTARES and KM3NeT telescopes, is part of the Global Neutrino Network (GNN) as an essential element of the network in the Northern Hemisphere of the Earth.
Neutrino is an excellent "storyteller" about astrophysical cataclysms. It flies through the Universe, practically not being absorbed by anyone or anything. Since this particle is neutral, it is not deflected by magnetic and electric fields, which means that its source lies exactly in the direction from which the appearance of neutrinos was recorded. The sources of cosmic neutrinos reaching the Earth are supernova explosions, black holes, active galactic nuclei or binary star systems. That is why neutrinos are an excellent tool for studying the processes taking place in space.
The BAIKAL-GVD neutrino telescope is designed to register and study ultrahigh-energy neutrino fluxes from astrophysical sources. With its help, scientists plan to investigate processes with a huge release of energy that took place in the Universe in the distant past. One of the mysteries of modern astrophysics is the mechanism of birth of astrophysical neutrinos in the Universe, billions of times more energetic than solar neutrinos, and the Baikal neutrino telescope, thanks to its unique characteristics, will be able to shed light on this mystery.
The Baikal Neutrino Telescope is a neutrino detector located in Lake Baikal at a distance of 3.6 km from the coast, where the depth of the lake reaches 1366 m. The location for the installation was not chosen by chance. First, there is a railway in this area and power lines. A large industrial and scientific center, the city of Irkutsk, is located 55 km from the detector. Secondly, the lake water is fresh, which prevents possible damage to equipment. Thirdly, for two months a year, the lake is covered with a strong ice cover, which allows installation work to be carried out without fear. And, finally, Baikal lacks the background glow from K40 and bioluminescence, which has a flare character.
They could prevent the detector from working properly.
When neutrinos pass through the Baikal water column, there is a possibility that some of the elusive particles will still be stopped by water. In the case of such an interaction, either a muon or a shower cascade of high-energy particles is formed. Both the muon and the shower cascade cause the glow of water, which is called Cherenkov radiation in physics, a phenomenon discovered by Soviet physicists P. A. Cherenkov and S. I. Vavilov. Such a glow occurs when a charged particle (for example, a muon) moves in water at a speed greater than the speed of light in water (the speed of light in water decreases inversely with the refractive index). In fact, a phenomenon occurs in which the muon overtakes the light. The task of the detector is to register Cherenkov radiation and separate events with astrophysical neutrinos from other possible events.
The largest structural unit of the GVD is the cluster. For 2020, the detector has seven clusters located at a distance of 300 m from each other. Each cluster consists of 8 vertically suspended garlands on which glass optical modules hang - 36 on each garland. According to the project, the volume of the finished installation at Lake Baikal should be about one cubic kilometer.
The Baikal neutrino telescope is being built today by international collaboration with the leading role of the Institute for Nuclear Research of the Russian Academy of Sciences (Moscow) - the founder of this experiment and the direction of "neutrino astronomy" in the world, and the Joint Institute for Nuclear Research (Dubna). In total, over 70 scientists and engineers from ten research centers in Russia, Germany, Poland, the Czech Republic and Slovakia are taking part in the project.
Photos by Bair Shaybonov