The first stage of the experiment on research of giant air showers has been completed at a new facility NEVOD-SHAL with the square of 10000 sqm, created at the territory of MEPhI as a part of Russian-Italian cooperation.
NEVOD-SHAL facility is aimed at registration of electron-photon component of giant air showers with energies of 1-100 petaelectronvolt and at determination of their parametres: power, arrival direction, and axis position. Currently, there is no possibility to conduct direct research of cosmic rays beyond atmosphere in this energy range: it is too expensive and difficult. That is why the only way to study energy spectrum and content of cosmic rays in this range is the research of giant air showers at above-ground launchers. The central part of NEVOD-SHAL facility in MEPhI is a system from 5 clusters of scintillation detect stations, placed on the rooftops of university buildings and on the Earth surface near NEVOD. Each cluster comprises 4 detect stations, connected to the local point of assembly and primary operation of signals, recorded by detect stations. Clusters are united in one system by a centre of control, synchronization, assembly, and processing of data with the help of fibre-optic links.
Photos of NEVOD-SHAL facility clusters
For the creation of NEVOD-SHAL facility the Italian side (University of Turin and INFN) allocated 192 scintillation detectors, equipped with photomultipliers Philips XP3462.
It should be mentioned that NEVOD Educational & Research Centre and University of Turin have cooperated in the field of cosmic ray research since 1992, and since then the only in the world coordinate tracking detector DECOR was created, aimed at the research of muon component from high zenith angles, and joint research has been conducted, the results of which were highly estimated by scientific community at different international and Russian conferences.
For the first time, cluster approach has been applied to determination of SHAL characteristics (RF patent № 2549612). The technical result of the invention is in the possibility of device application for determination of the arrival direction of giant air showers independent of relief and other peculiarities of the land because of nonuniform distribution of device detectors in space, in which detectors can be placed in any point of 3D space and have any geometrical shape.
Example of a recorded event. Arrows mark directions of arrival of giant air showers, restored by separate clusters
The aim of the research, conducted by MEPhI scientists, is the solution of a “muon puzzle”: growing with energy surplus of muon groups in broad atmospheric showers. Several years ago scientists’ attention was drawn by the fact that the number of muons, recorded by land detectors, is tens percent more than it should be according to existing theories. The solution of the “muon puzzle” will give a better understanding of nuclear cascade in interaction of ultrahigh energy particles, which is necessary for the research of characteristics of our Universe and studying processes, going on in it.
For the first time, reference to the “muon puzzle” was obtained in 2002-2007 during a long series of experiments at the DECOR facility, acting on MEPhI base. Later the existence of muon abundance was confirmed in experiments, conducted in the largest Pierre Auger Observatory in Argentina.
For its solution it is necessary to simultaneously measure muon energy release and the position of the axis of giant air showers. Such experiment was started at the unique research facility “Experimental complex “NEVOD” in MEPhI Institute of nuclear physics and technologies.
The experiment will be continued this year after the launch of 5 more clusters, which are now at the stage of erection and alignment.
