Scientists from the National Research Technological University "MISiS", together with the staff of the P. N. Lebedev Physical Institute of the Russian Academy of Sciences and the Dagestan State University, conducted an experiment on the non-invasive study of a room hidden in the ground located in the northwestern part of the Naryn-Kala fortress in Derbent.
The structure was examined using the method of muon radiography, a modern method of scanning the internal structure of substances. The information from the sensors is being processed now.
This 12-meter room is almost completely hidden underground, only a piece of a dilapidated dome is visible above the surface. The construction dates back to around 300 AD. Until recently, it was believed that it was originally an underground reservoir. However, recent research by archaeologists allows us to assert that this is the oldest Christian temple in the Russian Federation, which the Arabs fell asleep after they captured Derbent in about 700 AD. This is indicated by the cross-section of the building, the traces of the walled up entrances, the location of the walls of the structure on the cardinal points.
Not all archaeologists agree with the latter interpretation. It is difficult to judge their dispute with the help of the excavation of the temple, since, firstly, the Naryn-Kala fortress belongs to the UNESCO cultural heritage sites, and secondly, it is not clear how the walls of the structure, which have been exposed to precipitation for so long, will behave when freeing from the ground.
NUST MISIS scientists have the opportunity to “scan” the building and understand how it looked using muon radiography. The method has already proven its effectiveness - with its help, a secret room was found in the Cheops pyramid.
Not so long ago, under the leadership of Doctor of Physical and Mathematical Sciences, Professor Natalia Polukhina, the so-called track detectors were developed at MISiS, which allow not only to see muons falling on them, but also to determine the direction of their movement with high accuracy. By deciphering the readings from these detectors, it is possible to compile a three-dimensional picture of a variety of objects, from a meter-long voids in the soil to a map of caves in the mountain.
The essence of the method of muon radiography is to fix the muon flux density. Muons are unstable elementary particles with a negative electric charge, which are born in dense layers of the atmosphere and quickly perish, however, having time to pass through the entire atmosphere of the Earth during their lifetime (10 thousand muons fly to every square meter of the Earth's surface every minute) and even penetrate 8.5 kilometers under water or two kilometers into the earth.
The denser the substance, the faster the muon flux weakens. Therefore, if you place a solid object between the "space" and the detector, then the silhouette of the object under study will eventually appear on the detector. If there are cavities in the object, they will also be visible, since the muons flying through them overcome a smaller layer of solid material.
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Leading MISIS expert Professor Natalya Polukhina is one of the world's largest experts in this technique and is currently supervising the installation of muon sensors as part of the new SHiP (Search for Hidden Particles) experiment, which MISIS is implementing in cooperation with 40 leading universities of the world at the Large Hadron Collider.
A preliminary analysis of the fortress, carried out by experts from NUST MISIS and FIAN on topographic maps, suggests that in this case the technique is effective. It is important to note that the method allows you to distinguish between rocks with a difference in density of five percent, which will allow you to "see" the external appearance of the building.