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— The review is devoted to ultrahigh-energy gamma-ray astronomy, a branch of gamma-ray astronomy that studies photons with energies higher than 100 TeV. Gamma quanta of such energies can be generated in sources that accelerate protons and electrons to energies above 1 PeV. Such sources are commonly called PeVatrons, the study of which is important for understanding the origin of cosmic rays. The article briefly discusses possible galactic PeVatrons, research methods, setups, and results in the field of ultrahigh-energy gamma-ray astronomy. The second part of the article is devoted to the history, results and prospects of Russian installations in the region of ultrahigh energy gamma-ray astronomy.

The TAIGA observatory addresses ground-based gamma-ray astronomy at energies from a few TeV to several PeV, as well as cosmic ray physics from 100 TeV to several EeV and astroparticle physics. The TAIGA experiment current status, recent results and development prospects are presented.

This work is a methodical study of another option of the hybrid method originally aimed at gamma/hadron separation in the TAIGA experiment. In the present paper this technique was performed to distinguish between different mass groups of cosmic rays in the energy range 200 TeV - 500 TeV. The study was based on simulation data of TAIGA prototype and included analysis of geometrical form of images produced by different nuclei in the IACT simulation as well as shower core parameters reconstructed using timing array simulation. We show that the hybrid method can be sufficiently effective to precisely distinguish between mass groups of cosmic rays.

The scintillation experiment of the TAIGA astrophysical complex comprises two systems: Tunka-Grande and Taiga-Muon. The main objective of these systems is to study the energy spectrum and mass composition of cosmic rays in the energy range of eV, as well as to search for gamma radiation in the same energy range. An additional task of the experiments is to search for a signal from gamma quanta in the sub-PeV energy range in conjunction with wide angle Cherenkov detectors TAIGA-HiSCORE and Tunka-133. The report presents the objectives and status of the facility and a description of the design of scintillation counters and clusters. The results of the study of EAS with an unusual spatiotemporal structure are presented together with the results of a study of the joint operation of the Tunka-Grande and TAIGA-HiSCORE setups in order to search for sub-PeV gamma quanta. Estimates are made of the expected number of registered gamma quanta from the Crab Nebula.

This paper proposes a method for separation the light component of cosmic rays in the energy range of 200 TeV–20 PeV (the knee region in the PCR spectrum) from hybrid events detected by two Cherenkov setups IACT + HiSCORE in TAIGA experiment. The possibility of such separation is demonstrated using Monte Carlo calculations and the first experimental estimates are made.

The TAIGA gamma observatory is continuing its deployment at the Tunka valley, close to lake Baikal. The new, original detectors, able to work under severe conditions of Siberia, were developed to increase the TAIGA sensitivity for the study of gamma-quanta at energies about 1 PeV and above. The distinguishing feature of the detectors is the use of the wavelength shifting light guides for scintillation light collection on a photodetector. Several designs of the counters have been tested: equipped with PMT or SiPM photo-detectors, acrylic or polystyrene based scintillators with thickness from 1 to 5 cm and detecting area from 0.75 to 1.0 m 2 . The data on the amplitude of the signal from cosmic muons measured in different points within the counter are presented. The first 48 counters were produced and deployed in 2019 at the TAIGA experiment. They form 3 stations each with 8 surface detectors and 8 underground detectors buried at the depth of 1.7 m. After two winters, all counters are working.

The current status of the equipment development for the new wide-angle gamma-ray imaging air Cherenkov telescope for TAIGA hybrid installation is presented. A front-end electronic and data acquisition system board based on the Zynq family Xilinx FPGA chips specially designed for this project have been produced and are being tested. A detailed description if presented for internal structure of the four main subsystems: four 8-channel 100 MHz ADCs, board’s control system, internal clock and synchronization system and the power supply system. Additionally, the current status of a small scale prototype telescope SIT consisting of 49 SiPM is presented. The telescope includes a digital camera for observing the stars and weather condition. The SIT-HiSCORE synchronization systems and the telemetry information collection had been tested.

The Tunka-Grande array is part of a single experimental complex, which also includes the Tunka-133 and TAIGA-HiScORE (High Sensitivity COsmic Rays and gamma Explorer) wide-angle Cherenkov arrays, TAIGA-IACT array (Imaging Atmospheric Cherenkov Telescope) and TAGA-MUON scintillation array. This complex is located in the Tunka Valley (Buryatia Republic, Russia), 50 km from Lake Baikal. It is designed to study the energy spectrum and the mass composition of charged cosmic rays in the energy range 100 TeV - 1000 PeV, to search for diffuse gamma rays above 100 TeV and to study local sources of gamma rays with energies above 30 TeV. This report outlines 3 key points. The first is the description of the Tunka-Grande scintillation array. The second one presents the computer simulation strategy of the Tunka Grande array based on the Geant4 software. The third one is devoted to the prospects for future research in the field of cosmic ray physics and gamma-ray astronomy using simulation results.

In TAIGA Observatory (Tunka Advanced Instrument for cosmic ray physics and Gamma-ray Astronomy) we are commissioning the first Imaging Atmospheric Cherenkov Telescope (IACT). The telescope has an alt-azimuth mount and 17-bit shaft encoder for each axis, stepper motors are used for axis control. For the pointing calibration of the telescope a CCD-camera is installed on the dish of the telescope and its position allows to capture simultaneously both the Cherenkov camera with LEDs and the sky with observed source. Since October 2017, the telescope has been operating in tracking mode. In this work the TAIGAIACT telescope pointing calibration approach and first results of the tracking operations are described.

The Tunka-Grande scintillation array is described. Scientific results obtained over the first five years of its operation are presented. Prospects for studying cosmic rays in the 10 16 –10 18 eV range of energies are discussed.