## 2 The HORIZON-T Installation for Detection of High-Energy EAS and the Multi-modal Shower Events
The time delays between the scintillations are 318 ns and 465 ns, correspondingly for the second and third pulses relative to the leading one. The energy of the primary cosmic ray particle in the shower was \(\sim\)500 PeV and the zenith angle of the particle trajectory was about 30\({}^{\circ}\). Y axis title: normalized max value of ADC code. is seen that in the experimental events the intensity of the particles flux falls down much slower than it should be according to the simulation. The Tien Shan Ionization Calorimeter and Its Applicability for Selecting the Pure Electromagnetic Showers  
Currently, almost all experiments in the field of cosmic rays create or design installations for research in the field of gamma astronomy using the Cherenkov radiation method. This is due to the fact that the explosive processes of the formation and acceleration of protons and nuclei are accompanied by the generation of gamma quanta and neutrinos, which do not disperse, but fly in a straight line in the magnetic fields of the Universe. This in turn makes it possible to determine the place and study interactions with the release of tremendous energy in the Universe. Basically, the energy range of primary gamma quanta \(\leq\)10\({}^{12}\) eV is studied using installations that register Cherenkov radiation [11; 12; 13; 14; 15; 16]. In addition, various models and theories of the development of the Universe are created and tested based on experimental data obtained in the field of gamma astronomy. From the above mentioned, it becomes clear, that first of all, it is necessary to develop gamma-astronomical experimental research and methods for their observation. Hadron-55 is an experimental setup that has been modernized to improve the accuracy of registration of gamma quanta and can be used for research in the field of gamma astronomy. The principle of operation of this setup is to select events from interaction only in the gamma block, i.e., pure electron-photon components are selected. A network of high-resolution scintillation detectors (with accuracy to within nanoseconds) is used to increase the reliability of tracing the trajectory of primary particles. Upgraded ionization calorimeter with an array of scattered scintillation detectors is used for research in the region of high-energy gamma astronomy. To determine the zenith and azimuth angles of the EAS trajectory, scintillation detectors located around the calorimeter in a radius of 25, 40, and 100 m are used. The accuracy of determining the angles of a terrestrial gamma-ray flash is-0.2 degrees (refer to Figure 4). Figure 3: The distribution of the particle density \(\rho\) in dependence on the distance R in 217 multi-modal EAS events (scattered points), in comparison with the standard lateral distribution \(\rho\)(r) resulting from the CORSIKA simulation of the showers with primary energy 500 PeV (three lower curves) and 1000 PeV (upper curves). The introduction of an air gap between the upper and lower layers into the composition of this calorimeter makes it possible to increase the size of the shower. This, together with the scintillation detectors introduced at the level of the gamma block, increases the efficiency of the installation and makes it possible to use it for research in the field of high-energy gamma astronomy. The novelty of the research lies in carrying out gamma-astronomical studies, by the method of extensive air showers, i.e., without expensive Cherenkov detectors. It should be noted that the SHALON [17] installation with Cherenkov detectors is operating literally 50 m away, and the ongoing research will be compared with its results.