A. Silaev

The Cosmic Ray Mass Composition in the Energy Range 1015–1018eV measured with the Tunka Array: Results and Perspectives

The final analysis of the Extensive Air Shower (EAS) maximum ( X m a x ) depth distribution derived from the data of Tunka-25 atmospheric Cherenkov light array in the energy range 3 ⋅ 10 15 – 3 ⋅ 10 16 eV is presented. The perspectives of X m a x studies with the new Cherenkov light array Tunka-133 of 1 km 2 area, extending the measurements up to 10 18 eV, are discussed.

Space Program KOSMOTEPETL (project KLYPVE and TUS) for the study of extremely high energy cosmic rays

The scientific goal of the KOSMOTEPETL program is to observe and to study ultra high energy cosmic rays through the fluorescent tracks that they produce in the Earth atmosphere with the help of satellite based optical cameras based on the technology of a large mirror-concentrator of light. At low orbits (400–600 km) a mirror with an area of 400 m2 will allow us to observe neutrino induced horizontal tracks starting at the energy threshold of 1 EeV. With these neutrinos, which have to be produced in collisions of extreme energy cosmic rays (with energy >50 EeV) with background photons at distances >100 Mpc, the most distant cosmic ray sources will be revealed. Design of the TUS and KLYPVE detectors (the first detectors of the KOSMOTEPETL program with a mirror area 2 and 10 m2) is presented.

KLYPVE/TUS space experiments for study of ultrahigh-energy cosmic rays

The KLYPVE space experiment has been proposed to study the energy spectrum, composition, and arrival direction of ultrahigh-energy cosmic rays (UHECR) by detecting from satellites the atmosphere fluorescence and scattered Cherenkov light produced by EAS, initiated by UHECR particles. The TUS setup is a prototype KLYPVE instrument. The aim of the TUS experiment is to detect dozens of UHECR events in the energy region of the GZK cutoff, to measure the light background, to test the atmosphere control methods, and to study stability of the optical materials, PMTs, and other instrumental parts in space environment.

Energy spectrum and mass composition of cosmic rays, by the data of the Tunka-133 array

The Tunka-133 Cherenkov light array for the detection of extensive air showers (EAS) acquires data over the five winters from 2009 to 2014. The direction of arrival, the shower core coordinates on the plane of observation, the primary energy, and the depth of the shower maximum are reconstructed for each EAS. A differential all-particle energy spectrum is obtained in the energy range of 6 × 1015–3 × 1018 eV over 1540 h, along with the energy dependence of the average depth of the shower maximum in the range of 6 × 1016–3 × 1018 eV. Based on this dependence, the variation in the average composition of the primary cosmic rays is estimated as a function of energy.

First results from the operation of the prototype Tunka-HiSCORE array

The Tunka-HISCORE wide-angle Cherenkov array, one part of the planned TAIGA integrated gamma observatory intended for investigations in the field of high-energy (>30 TeV) gamma-ray astronomy and cosmic-ray physics, is deployed in the Tunka Valley (Buryat Republic). The first results from operating a prototype array composed of nine stations spread over an area of ∼0.1 square kilometers during the winter of 2013–2014 are presented. Data processing techniques are described, along with data on the accuracy of reconstructing the position of a shower’s axis, energy, and angle of arrival. The differential spectrum of all cosmic-ray particles in a shower in the energy range of 2 × 1014 to 2 × 1016 eV is presented and compared to the available data.

Results and perspectives of cosmic ray mass composition studies with EAS arrays in the Tunka Valley

The study of the cosmic ray mass composition in the energy range 1016 - 1018 eV is one of the main aims of Tunka-133. This EAS Cherenkov array started data acquisition in the Tunka Valley (50 km from Lake Baikal) in autumn 2009. Tunka-133 provides a measurement of the EAS maximum depth (Xmax) with an accuracy of about 30 g/cm2 . Further mass composition analyses at the highest energies (1017 - 1018 eV) will be based on the comparison of primary energy measured by the radio method and the densities of charged particles measured by shielded and unshielded detectors. The high duty cycle of the common operation of the new scintillation array (Tunka-Grande) and the radio extension of the experiment (Tunka-REX) will provide a high statistics of events.

Electronics for the KLYPVE Detector

The KLYPVE optical detector on board the Russian segment of the ISS will observe 10 thousand km2 of the Earth atmosphere registering the extremely high energy cosmic ray (EHECR) particles producing fluorescent tracks in the atmosphere. In this article the design of the detector is presented, including: the Fresnel type mirror of 10 m2 area, the PMT retina of 2500 pixels, the pixel electronics, the data acquisition electronics, and the trigger system. The detector design is suited to conditions of the space experiment (wide range of temperature, short day-night cycle etc). The problem of selection of rare EHECR events in the presence of high intensity background light is discussed.

Temporal structure of scintillation detector pulse in EAS

At the Moscow University EAS array the detector pulse shapes were observed with the help of two scintillation detectors of area 4 , each separated by 23 m. The pulse shapes were analysed in EAS with a particle density of more than 10 . 13 pulses were observed in the EAS with sizes at core distances R > 200 m. Some of the pulses have fine temporal structure with secondary peaks corresponding to tens of particles. Comparison of the individual experimental pulse shapes with the pulse shapes expected for the EAS particles arriving randomly due to the average time distribution indicates the non-statistical temporal structure of the pulses.

PREPARATION OF THE TUS SPACE EXPERIMENT FOR UHECR STUDY

We report on the current status of the TUS space mission project: its goals and the progress achieved so far. The Fresnel mirrors design, performed checks and their production are discussed. Also we discuss our future plans including auxiliary analysis of the fluorescence light yield measured this year by LAPP (Annecy), JINR (Dubna) and LIP (Lisbon) MACFLY Collaboration.

The TAIGA experiment: from cosmic ray to gamma-ray astronomy in the Tunka valley

The physical motivations and advantages of the new gamma-observatory TAIGA (Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy) is presented. The TAIGA array is a complex, hybrid detector for ground-based gamma-ray astronomy for energies from a few TeV to several PeV as well as for cosmic ray studies from 100 TeV to several EeV. The TAIGA will include the wide angle Cherenkov array TAIGA-HiSCORE with ~5 km2 area, a net of 16 I ACT telescopes (with FOV of about 10x10 degree), muon detectors with a total area of up to 2000-3000 m2 and the radio array Tunka-Rex.