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The unique scientific facility NEVOD, created by the scientists of the National Research Nuclear University MEPhI, is one of the most interesting experimental complexes for the study of cosmic rays in our country and the world. Understanding how it works
Life and its development on Earth are largely subject to the laws and processes taking place in the Universe. The action of gravity, oceanic and sea tides and other phenomena familiar to us exist as a result of the constant interaction of our planet with its cosmic neighbors – the Sun and the Moon.
What are cosmic rays
Cosmic rays are one of the most interesting and not fully understood phenomena, which has a significant impact on the life of our planet. Rays are born in the depths of space, but their origin is still a mystery.
Rays are protons and nuclei of various atoms that move in outer space at high speeds. Some of these particles reaching the Earth have colossal energies, millions of times greater than the energy of particles in the Large Hadron Collider. The study of the flow and interaction of cosmic rays with our planet, as well as the search for answers to questions about their origin, open the way to New Physics. This is exactly what scientists, graduate students and students of NRNU MEPhI are doing at the NEVOD Experimental Complex.
How NEVOD works
The experimental complex NEVOD (or the NEUTRINO WATER Detector) is a unique facility in terms of scale and capabilities for recording and studying cosmic rays. The name NEVOD echoes the “fishing net” for catching cosmic particles by registering them in water.
The complex includes several physical detectors and installations. The basis of NEVOD is the Cherenkov water detector, which works with radiation named after the Soviet scientist Pavel Alekseevich Cherenkov, who discovered it. Cherenkov radiation is a glow caused by the movement of a charged particle in a transparent medium, when its speed exceeds the speed of light in the same medium.
Nothing can travel faster than light in a vacuum, but in matter the speed of light can be much slower. If a particle passes through a transparent medium, such as water, its speed can be faster than the speed of light in water. By analogy, you can imagine a fighter whose speed is greater than the speed of sound: in this situation, the fighter will fly first, followed by a sound wave. The same effect occurs in water, where Cherenkov radiation is in the visible part of the spectrum, you can see it with your own eyes, for example, during the operation of a nuclear reactor.
Cherenkov radiation is widely used in detectors of elementary particles. So, the basis of the NEVOD complex is a huge pool with a volume of 2 thousand cubic meters. m, in which there is a “capture” of light from cosmic particles. In comparison, if you turn on two bathroom taps at the same time, it will take several months to fill a pool of this size.
For stable operation of the detector and prevention of metal corrosion, the water in the pool must be very clean, therefore, distilled water is used in the detector, and to avoid external light, the pool is covered with steel covers and a special leatherette coating.
Inside the pool, quasi-spherical measuring modules (QSM) are located in the form of a spatial lattice. QSMs are the main detecting element of the design of the Cherenkov detector. They make it possible to detect Cherenkov radiation using built-in photomultipliers.
A photomultiplier is a highly sensitive light detector in various ranges of the electromagnetic spectrum. Each module has six photomultipliers, which are directed along all axes of coordinates, that is, they look in six different directions: to the right, to the left, up, down, forward and back in relation to the center of the module.
The modules in the pool are staggered at a small distance from each other, which creates a dense spatial grid. This design makes it possible to detect particles from any direction with almost the same high efficiency and to measure Cherenkov radiation with high accuracy. This is a unique feature of quasi-spherical modules, the creation of which was awarded the Lenin Komsomol Prize. Their concept was decades ahead of its time; such measuring modules began to be designed in Europe only 30 years later.
will catch everyone
Another significant feature is the location of the NEVOD complex itself: it is located on the Earth’s surface, which is not typical for such detectors. They are usually placed deep underground or in ice. Thanks to this position, NEVOD has an advantage and can detect a wide variety of particles, both “classical” muons for such devices, and others. What are these particles?
Being born, cosmic rays move in space and fall into the heliosphere – the outer shell of the Sun. There, cosmic rays begin to deviate and interact with the interplanetary magnetic field and its perturbations. When primary cosmic rays, which consist of atomic nuclei, reach the Earth’s atmosphere, they collide with the nuclei of nitrogen and oxygen atoms, the main gases of the atmosphere. As a result of such interaction of cosmic particles, secondary particles appear – pions, which “live” for only 0,03 microseconds. Pions decay into even smaller particles – muons, which “live” almost a hundred times longer and have time to reach the Earth’s surface. Thus, 70% of the particles reaching the Earth’s surface are precisely muons, which received their name from the letter “mu” of the Greek alphabet.
Every minute a 10 m detector2 registers 80 thousand such particles. Each detector has a monitor that collects the received data and controls the operation of the detector. The monitors are located in a single information collection center, where data from all NEVOD systems and detectors are accumulated and stored.
Harness the Sun
The analysis of registered cosmic rays is extremely important both for new scientific discoveries and for practical applications in everyday life. First, cosmic rays are a powerful free accelerator that can be used to conduct experiments similar to those conducted on accelerators. Secondly, the study of cosmic rays helps to understand the activity of the Sun and the peculiarities of solar-terrestrial relations. The sun is a powerful thermonuclear reactor that determines many processes on our planet. The activity of the Sun is unstable, various flares and ejections of plasma clouds often occur there.
Plasma clouds have a very high temperature and can fly out in different directions. If the cloud moves towards the Earth, it can lead to the appearance of strong magnetic storms and turbulence zones that can disable satellites, global positioning systems, and disrupt aviation routes.
To recognize such phenomena in the NEVOD complex, the URAGAN installation was created, designed to study the variations of cosmic rays that exist in the heliosphere, magnetosphere, and atmosphere. In real time, the installation registers particle flows from all directions, analyzes their distribution and various variations. Particle streams are captured in the form of images, where the intensity of the muon stream is highlighted in a certain color. Green means some average value, normal muon background. Blue color is a decrease in intensity, and red-yellow signals disturbances in the direction of particle movement. Such a process is called muon diagnostics and makes it possible to detect anomalous disturbances in the Earth’s magnetic field in advance.
On the way to New Physics
Thus, the NEVOD complex is a unique research center that has no analogues in the world. NEVOD was developed and created by MEPhI students, graduate students and scientists, and is one of the largest university research centers. Now employees are faced with the task of upgrading existing and developing new detectors for subsequent challenges and discoveries in search of New Physics. Achieving these goals will make the NEVOD complex part of the global network of mega-science research centers.