E. Popova

The Silicon Photomultiplier (SiPM) is a semiconductor device consisting of many photon microcounters (103 mm−2) positioned on a common Si substrate. SiPM operates in a limited Geiger mode and has single photoelectron gain (106) and photon detection efficiency (20%) similar to vacuum PMT. Main SiPM features are described and a number of examples of its possible applications are demonstrated, such as scintillator fiber readout, scintillator tiles+WLS readout, imaging Cherenkov counter timing. These SiPM applications are based on experimental test data and SiPM performance is compared with other photodetectors (PMT, APD, HPD, VLPC).

The state of art of the Silicon Photomultipliers (SiPM's)—their features, possibilities and applications—is given. The significant progress of this novel technique of photo detection is described and discussed.

Recent results on Limited Geiger-mode Microcell Silicon Photodiode (LGP) are described. Two new modifications of LGP have been designed and produced. Each of them consists of 104 pixels 10×10μm2 size with area of 1mm2. These pixels operate as an independent photon counters, giving the output signal as a sum of the signals from pixels fired by photons. The effective “gain” is large (≈105). The efficiency of the visible light photon detection of few percents has been measured. Low-temperature dark rate dependence has been studied. The timing by LGP at the level of 100 ps (FWHM) was found.

The EAS Cherenkov light array Tunka-133, with ~3 km2 geometric area, is taking data since 2009. The array permits a detailed study of cosmic ray energy spectrum and mass composition in the PeV energy range. After a short description of the methods of EAS parameter reconstruction, we present the all-particle energy spectrum and results of studying CR composition, based on 3 seasons of array operation. In the last part of the paper, we discuss possible interpretations of the obtained results.

A new EAS Cherenkov light array, Tunka-133, with ∼1km2 geometrical area has been installed at the Tunka Valley (50 km from Lake Baikal) in 2009. The array permits a detailed study of cosmic ray energy spectrum and mass composition in the energy range 1016–1018 eV with a uniform method. We describe the array construction, DAQ and methods of the array calibration. The method of energy reconstruction and absolute calibration of measurements are discussed. The analysis of spatial and time structure of EAS Cherenkov light allows to estimate the depth of the EAS maximum Xmax. The results on the all particles energy spectrum and the mean depth of the EAS maximum Xmax vs. primary energy derived from the data of two winter seasons (2009–2011) are presented. Preliminary results of joint operation of the Cherenkov array with antennas for the detection of EAS radio signals are shown. Plans for future upgrades – deployment of remote clusters, radioantennas and a scintillator detector network and a prototype of the HiSCORE gamma-telescope – are discussed.

The silicon photomultiplier (SiPM) is a novel photon detector based on Geiger mode operating avalanche photodiodes. In this paper, we present results from a test, demonstrating the feasibility of SiPM as readout elements in scintillator-based positron emission tomography (PET). As scintillator we use the newly developed LYSO crystals having similar characteristics as LSO. With our setup we measure an energy resolution of about 22% and a time resolution of a single crystal element of (1.51±0.07)ns, both full-width at half-maximum. A significant improvement in time resolution could be achieved by triggering on the first photoelectron in the signal. We also present the coincidence rate of two detector channels vs. the position of a small point-like 22Na positron source.

The advanced study of new photo detector Silicon Photomultiplier (SiPM) is presented. SiPM consists of many (∼103 mm−2) silicon micro pixels, which are independent photon micro counters working in limited Geiger mode with a gain of 106. The SiPM output signal is a sum of the signals from a number of pixels fired by photons. The main features of SiPM are: low excess noise factor, the photon detection efficiency at the level of vacuum PMT, low bias voltage (∼24V). The timing of the SiPM is about 30 ps for 10 photoelectrons. The possibilities of SiPM applications based on experimental tests are demonstrated: sci fiber readout, scintillator-shifter system readout, possible application for hadron calorimeters.

We present the results of a search for high energy extraterrestrial neutrinos with the Baikal underwater Cherenkov detector NT200, based on data taken in 1998 - 2002. Upper limits on the diffuse fluxes of $\nu_e+\nu_{\mu}+\nu_{\tau}$, predicted by several models of AGN-like neutrino sources, are derived. For an $E^{-2}$ behavior of the neutrino spectrum, our limit is $E^2 \Phi_{\nu}(E)<8.1 10^{-7} cm^{-2} s^{-1} sr^{-1} GeV$ over an neutrino energy range $2 10^4 - 5 10^7 GeV$. The upper limit on the resonant $\bar{\nu}_e$ diffuse flux is $\Phi_{\bar{\nu}_e}< 3.3 10^{-20} cm^{-2} s^{-1} sr^{-1} GeV^{-1}$.

The Silicon Photomultipliers (SiPMs) with large area up to 10×10mm2 are considered and their optimal parameters, such as efficiency, gain, dark rate, afterpulsing probability and optical crosstalk are discussed. The 3×3mm2 SiPM is described and its performance is demonstrated. Three examples of 3×3mm2 SiPM application are given: (1) transition radiation X-ray detection; (2) time of flight measurements with fast scintillators; (3) detection of PET gammas using LYSO crystals. Corresponding experimental results are presented and discussed.

Characteristics of cosmic-ray hadronic interactions in the 1015 − 1017 eV range are studied by observing a total of 429 cosmic-ray families of visible energy greater than 100 TeV found in emulsion chamber experiments at high mountain altitudes, Chacaltaya (5200 m above sea level) and the Pamirs (4300 m above sea level). Extensive comparisons were made with simulated families based on models so far proposed, concentrating on the relation between the observed family flux and the behaviour of high-energy showers in the families, hadronic and electromagnetic components. It is concluded that there must be global change in characteristics of hadronic interactions at around 1016 eV deviating from thise known in the accelerator energy range, specially in the forwardmost angular region of the collision. A detailed study of a new shower phenomenon of small-pT particle emissions, pT being of the order of 10 MeV/c, is carried out and its relation to the origin of huge "halo" phenomena associated with extremely high energy families is discussed as one of the possibilities. General characteristics of such super-families are surveyed.

The EAS Cherenkov light array Tunka-133, with ~ 3 km2 geometric area, is taking data since 2009.The array permits a detailed study of energy spectrum and mass composition of cosmic rays in the energy range from 6 · 1015 to 1018 eV. We describe the methods of time and amplitude calibration of the array and the methods of EAS parameters reconstruction. We present the all-particle energy spectrum, based on 7 seasons of operation.

The novel type of the Silicon Photodiode — Limited Geiger-mode Photodiode (LGP) has been produced and studied. The device consists of many ≈104 mm−2 independent cells ≈10 mkm size around n+ -“pins” located between p-substrate and thin SiC layer. Very high gain more than 104 for 0.67 mkm wave length light source and up to 6·105 for single electron have been achieved. The LGP photon detection efficiency at the level of one percent has been measured.

We report on the design, construction and performance of a prototype for a high-granularity tile hadronic calorimeter for a future international linear collider detector. Scintillating tiles are read out via wavelength-shifting fibers that guide the scintillation light to a novel photodetector, the silicon photomultiplier. A prototype has been tested using a positron test beam at DESY. The results are compared with a reference prototype calorimeter equipped with multichannel vacuum photomultipliers. Detector calibration, noise, linearity and stability are discussed, and the energy response in a 1–6 GeV positron beam is compared with simulations. The present results demonstrate that the silicon photomultiplier is well-suited as photodetectors in calorimeters and thus has been selected for the construction of a 1m3 calorimeter prototype to operate in hadron beams.

We have studied a novel semiconductor photon detector (silicon photomultiplier) as a readout for LSO scintillator crystals used in PET detectors. Silicon photomultipliers (SiPMs) of a (1×1) mm2 area were coupled to LSO crystals of (2×2×10) mm3. Two elements were exposed to a 22Na positron source emitting two 511 keV gamma quanta. Coincidence studies yielded a FWHM of the photopeak spectrum around 35% and a time resolution of 3 ns. Extrapolating from the large area mismatch in the readout area allows us to conclude that the novel SiPM is a very promising element for PET applications.

We present physical motivations and advantages of the new gamma-observatory TAIGA (Tunka Advanced Instrument for cosmic ray physics and gamma-ray astronomy). TAIGA will be located in the Tunka valley, 50 km to the west of Lake Baikal, at the same place as the integrating air Cherenkov detector for cosmic rays Tunka-133. 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 array will consist of a wide angle Cherenkov array – TAIGA-HiSCORE with 5km2 area, a net of 16 IACT telescopes (with FOV of about 9.72°×9.72°) as well as muon and other detectors. We present the current status of the array construction.

The new TAIGA-HiSCORE non-imaging Cherenkov array aims to detect air showers induced by gamma rays above 30 TeV and to study cosmic rays above 100 TeV. TAIGA-HiSCORE is made of integrating air Cherenkov detector stations with a wide field of view (0.6 sr), placed at a distance of about 100 m. They cover an area of initially ∼0.25 km2 (prototype array), and of ∼5 km2 at the final phase of the experiment. Each station includes 4 PMTs with 20 or 25 cm diameter, equipped with light guides shaped as Winstone cones. We describe the design, specifications of the read-out, DAQ and control and monitoring systems of the array. The present 28 detector stations of the TAIGA-HiSCORE engineering setup are in operation since September 2015.

We present the first neutrino induced events observed with a deep underwater neutrino telescope. Data from 70 days effective life time of the BAIKAL prototype telescope NT-96 have been analyzed with two different methods. With the standard track reconstruction method, 9 clear upward muon candidates have been identified, in good agreement with 8.7 events expected from Monte Carlo calculations for atmospheric neutrinos. The second analysis is tailored to muons coming from close to the opposite zenith. It yields 4 events, compared to 3.5 from Monte Carlo expectations. From this we derive a 90% upper flux limit of 1.1 · 10−13 cm−2 sec−1 for muons in excess of those expected from atmospheric neutrinos with zenith angle > 150 degrees and energy > 10 GeV.

One of the major drawbacks of a SiPM is due to the so-called cross-talk effect. Often, one single photon in a chain reaction can generate more photons and thus can fire more than one micro-cell of a SiPM. This can be considered as a noise in the signal multiplication process and this degrades the signal/noise ratio. In self-trigger schemes this noise can be so high that it can make operating them difficult at low threshold settings. For the past few years, we have dwelt on this effect aiming to suppress it at the design stage. One can use (a) trenches around the micro-cells for suppressing the direct photon “communication” channel and (b) the so-called double p–n junction for suppressing photon-induced charge “communication” in neighbor pixels. The low cross-talk is mandatory, for example, for producing SiPM-based light sensor modules for the Imaging Atmospheric Cherenkov Technique projects for ground-based gamma-ray astrophysics. We produced and tested a few modules consisting of 4 SiPMs, each with a size of 5 mm×5 mm of custom production type. We report here on the main parameters of these units.

A new analysis of the data from the NT200 neutrino telescope based on the reconstruction of parameters for high-energy showers generated in neutrino interactions has yielded new upper limits on the diffuse neutrino fluxes predicted by a number of theoreticalmodels. The upper limit on the all-flavor neutrino flux with an energy spectrum E −2 is E 2Φ ν < 2.9 × 10−7 GeV cm−2 s−1 sr−1.

We present results of a search for relativistic magnetic monopoles with the Baikal neutrino telescope NT200, using data taken between April 1998 and February 2003. No monopole candidates have been found. We set an upper limit 4.6 × 10−17 cm−2 s−1 sr−1 for the flux of monopoles with βm = 1. This is a factor of 20 below the Chudakov–Parker bound which is inferred from the very existence of large-scale galactic magnetic fields.

TAIGA stands for ``Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy'' and is a project to built a complex, hybrid detector system for ground-based gamma-ray astronomy from a few TeV to several PeV, and for cosmic ray studies from 100 TeV to 1 EeV. TAIGA will search for ``PeVatrons'' (ultra-high energy gamma-ray sources) and measure the composition and spectrum of cosmic rays in the knee region (100 TeV–10 PeV) with good energy resolution and high statistics. TAIGA will include Tunka-HiSCORE — an array of wide-angle air Cherenkov stations, an array of Imaging Atmospheric Cherenkov Telescopes, an array of particle detectors, both on the surface and underground and the TUNKA-133 air Cherenkov array.

We report early optical linear polarization observations of two gamma-ray bursts made with the MASTER robotic telescope network. We found the minimum polar- ization for GRB150301B to be 8% at the beginning of the initial stage, whereas we detected no polarization for GRB150413A either at the rising branch or after the burst reached the power-law afterglow stage. This is the earliest measurement of the polarization (in cosmological rest frame) of gamma-ray bursts. The primary intent of the paper is to discover optical emission and publish extremely rare (unique) high- quality light curves of the prompt optical emission of gamma-ray bursts during the non-monotonic stage of their evolution. We report that our team has discovered the optical counterpart of one of the bursts, GRB150413A.

The TAIGA observatory addresses ground-based gamma-ray astronomy at energies from a few TeV to several PeV, cosmic ray physics from 100 TeV to several EeV as well as for search for axion-like particles, Lorentz violations and another evidence of New Physics. In 2020 year a one square kilometer TAIGA setup should be put in operation.

We review the status of the Baikal neutrino telescope, which is operating in Lake Baikal since 1998 and has been upgraded to the 10 Mton detector NT200+ in 2005. We present selected physics results on searches for upward going neutrinos, relativistic magnetic monopoles and for very high-energy neutrinos. We describe the strategy of creating a detector on the Gigaton (km3) scale at Lake Baikal. First steps of activities towards a km3 Baikal neutrino telescope are discussed.

The objective of the Baikal Project is the creation of a kilometer-scale high-energy neutrino observatory: the Gigaton Volume Detector (GVD) in Lake Baikal. Basic elements of the GVD – new optical modules, FADC readout units, and underwater communication systems – were investigated and tested in Lake Baikal with prototype strings in 2008–2010. We describe the results of prototype strings operation and review the preliminary design and expected sensitivity of the GVD telescope.

We review the status of the Lake Baikal Neutrino Experiment. Preparation towards a km3-scale Gigaton Volume Detector (GVD) in Lake Baikal is currently a central activity. As an important milestone, a km3-prototype string comprising of 12 optical modules and based on a completely new technology, has been installed and was put in operation together with NT200+ in April, 2009. We also present recent results from the long-term operation of NT200, including an improved limit on the diffuse astrophysical neutrino flux.

The Cherenkov light array for the registration of extensive air showers (EAS) Tunka-133 collected data during 5 winter seasons from 2009 to 2014. The differential energy spectrum of all particles and the dependence of the average maximum depth on the energy in the range of 6 ⋅ 1015–1018 eV measured for 1540 hours of observation are presented.

Data obtained with two detectors located at the Tunka Cosmic Ray facility are presented. The Cherenkov light array for registration of extensive air showers (EAS) Tunka-133 collected data during 5 winter seasons since 2009 to 2014. The differential energy spectrum of all particles and the dependence of the average maximum depth on the energy in the range of 6 · 1015−1018 eV measured for 1540 hours of observation are presented.

We report on the MASTER Global Robotic Net discovery of an eclipsing binary, MASTER OT J095310.04+335352.8, previously known as unremarkable star TYC 2505-672-1, which displays extreme orbital parameters. The orbital period P = 69.1 yr is more than 2.5 times longer than that of ε-Aurigae, which is the previous record holder. The light curve is characterized by an extremely deep total eclipse with a depth of more than 4.5 mag, which is symmetrically shaped and has a total duration of 3.5 yr. The eclipse is essentially gray. The spectra acquired with the Russian 6 m BTA telescope both at minimum and maximum light mainly correspond to an M0-1III–type red giant, but the spectra taken at the bottom of eclipse show small traces of a sufficiently hot source. The observed properties of this system can be better explained as the red giant eclipsed by a large cloud (the disk) of small particles surrounding the invisible secondary companion.

This article considers the effect of MoO3 and SiO additives in telluride glasses on the shielding characteristics and protection of electronic microcircuits operating under conditions of increased radiation background or cosmic radiation. MoO3 and SiO dopants were chosen because their properties, including their insulating characteristics, make it possible to avoid breakdown processes caused by radiation damage. The relevance of the study consists in the proposed method of using protective glasses to protect the most important components of electronic circuits from the negative effects of ionizing radiation, which can cause failures or lead to destabilization of the electronics. Evaluation of the shielding efficiency of gamma and electron radiation was carried out using a standard method for determining the change in the threshold voltage (∆U) value of microcircuits placed behind the shield and subjected to irradiation with various doses. It was established that an increase in the content of MoO3 and SiO in the glass structure led to an increase of up to 90% in the gamma radiation shielding efficiency, while maintaining the stability of microcircuit performance under prolonged exposure to ionizing radiation. The results obtained allow us to conclude that the use of protective glasses based on TeO2-WO3-Bi2O3-MoO3-SiO is highly promising for creating local protection for the main components of microcircuits and semiconductor devices operating under conditions of increased background radiation or cosmic radiation.

The purpose of this work is development of glasses for radioactive materials encapsulation. Borosilicate-based glass systems "R7/T7" (B2O3-ЅіO2-Al2O3-Na2O-СaO) doped with Eu3+, with various concentrations of activator were studied. The composition of the obtained glasses was investigated using electron-probe microanalysis technique. Optical properties of glasses were investigated using the following methods – cathodoluminescence, photoluminescence and absorption spectra. The range of the optimal activator concentration was determined. Samples of borosilicate glass (B2O3-ЅіO2-Al2O3-Na2O-СaO) doped with varied content of Eu3+ were synthesized and studied using electron probe microanalysis (EPMA) and optical techniques such as cathodoluminescence (CL), photoluminescence (PL) and light absorption spectroscopy. Glass composition was related to development of nuclear waste form or encapsulation matrix with sufficient resistance to radiation damage. It was observed that electron beam irradiation suppresses intensity of glass cathodoluminescence and this process is correlated with sodium diffusion outside irradiated area at comparable interval of time.

We present the results of a search for high-energy neutrinos with the Baikal underwater Cherenkov detector NT-96. An upper limit on the diffuse flux of νe+νμ+νμ̄ of E2Φν(E)<1.4×10−5cm−2s−1sr−1GeV within neutrino energy range 104–107GeV is obtained, assuming an E−2 behavior of the neutrino spectrum.

We review the present status of the Baikal Neutrino Project and present results on upward going atmospheric neutrinos, results of a search for high energy extraterrestrial neutrinos as well as preliminary results of searching for acoustic signals from EAS in water. We describe the moderate upgrade of NT-200 planned for the next years and discuss a possible detector on the Gigaton scale.

We review the status of the Lake Baikal Neutrino Experiment. The Neutrino Telescope NT200 has been operating since 1998 and has been upgraded to the 10 Mton detector NT200+ in 2005. We present selected astroparticle physics results from long-term operation of NT200. Also discussed are activities towards acoustic detection of UHE-energy neutrinos, and results of associated science activities. Preparation towards a km3-scale (Gigaton volume) detector in Lake Baikal is currently a central activity. As an important milestone, a km3-prototype string, based on completely new technology, has been installed and is operating together with NT200+ since April, 2008.

A prototype string for the future km3-scale Baikal neutrino telescope has been deployed in April, 2008, and is fully integrated into the NT200+ telescope. All basic string elements–optical modules (with 12″/13″ hemispherical photomultipliers), 200 MHz FADC readout and calibration system–have been redesigned following experience with NT200+. First results of in-situ operation of this prototype string are presented.

Development of solid state photon detectors is a mature field of engineering and technology based on well-established grounds of solid state physics, and, in the same time, a frontier area of research and innovations faced with dramatic challenges. The ultimate challenge for the modern developments is a detection of optical signals at a quantum level – resolving arrival time and spatial location of individual photons – to realize a formula “every photon counts”. To succeed, the developments are focused on improvements in three directions: threshold sensitivity and photon number resolution, fast timing and time resolution, and fine granularity imaging with fast readout. There are many inherent trade-offs to be resolved in each direction. Development of Silicon Photomultiplier (SiPM) is considered as one of the most promising innovations toward “near ideal” photon detector. SiPMs of various designs have been developed in the 1990s–2000s in Russia, and their unique performance in the photon number and time resolution has been demonstrated and recognized in the mid-2000s. Now SiPMs are widely implemented in nuclear medicine, high energy physics, astrophysics, and Cherenkov light detection. However, developers of Geiger Mode APD or SPAD arrays based on active quenching also found new approaches and opportunities for considerable improvements using modern CMOS technology, namely: reduction of a dead space occupied by electronics, multiplexing readout architecture, backside illumination, and 3D integration of photosensor and electronic layers (3D digital SiPM). Detection of Cherenkov light is one of the most challenging applications for photodetectors. Superior photon number resolution starting from single photons, picosecond-scale time resolution, and large-area imaging are typical requirements, and all these highly demanded capabilities are contradictory. This report presents overview and analysis of the state-of-art in the modern solid state photon detectors as well as their potential and perspectives to meet the quantum imaging challenge.

The Silicon Photomultiplier (SiPM) is a mature photodetector concept that is applied in a variety of applications ranging from medical imaging to automotive LiDAR systems. Over the last few years, improvements of the sensor performance are gradually approaching to a saturation. In this work we present our new concept to overcome the intrinsic limitations of planar configurations of electrodes. Our non-planar technology is based on focusing and enhancing the electric fields by tip-like electrodes. The shape of the electric field and the lack of typical micro-cell edges, allows us to exclude cell separation boundaries and eliminate dead space around active cell areas. Our design provides a high-density micro-cell layout with a high geometric efficiency. It resolves the well-known trade-off between the detection efficiency and the dynamic range. The first “Tip Avalanche Photodiode” (TAPD) prototypes show a remarkable geometric efficiency above 80% for a micro-cell pitch of 15 μm. This directly translates into a photon detection efficiency (PDE) record peak value of 73% at 600nm with respect to the state-of-the-art SiPMs. Moreover, the PDE remains above a value of 45% up to a wavelength of 800nm with another record value of 22% at 905nm. The reduced micro-cell capacity allows for a fast recovery time below 4ns, which improves the operation at high photon rates. Overall, the TAPD is anticipated to be a very promising SiPM generation for various wide-spectral and high-dynamic-range applications in health science, biophysics, particle physics and LiDARs.

Within the framework of the CALICE collaboration, our group has characterized Silicon Photomultipliers (SiPMs) from various producers, in order to enhance the single cell performances of a highly granular analog hadron calorimeter, with particular emphasis on improving the linearity of the response, ensuring environmental stability, calibration portability and reducing the parameters spread among the different channels. As an outcome, new plastic scintillator tiles coupled to KETEK PM1125 SMD SiPM have been commissioned, characterized and mounted on calorimeter modules: details and results of the characterization procedure, together with the performances of the new tile and SiPM design will be discussed. The radiation tolerance to X-rays of KETEK PM1125 is also under investigation. The amount and type of damage caused by irradiation of the devices exposed to 3 kGy and 20 MGy doses will be presented.

We present measurements of the reduction of light output by plastic scintillators irradiated in the CMS detector during the 8 TeV run of the Large Hadron Collider and show that they indicate a strong dose rate effect. The damage for a given dose is larger for lower dose rate exposures. The results agree with previous measurements of dose rate effects, but are stronger due to the very low dose rates probed. We show that the scaling with dose rate is consistent with that expected from diffusion effects.

The investigation of energy spectrum and mass composition of primary cosmic rays in the energy range 1016–1018 eV and the search for diffuse cosmic gamma rays are of the great interest for understanding mechanisms and nature of high-energy particle sources, the problem of great importance in modern astrophysics. Tunka-Grande scintillator array is a part of the experimental complex TAIGA (Tunka Advanced Instrument for Cosmic Ray and Gamma Astronomy) which is located in the Tunka Valley, about 50 km from Lake Baikal. The purpose of this array is the study of diffuse gamma rays and cosmic rays of ultra-high energies by detecting extensive air showers. We describe the design, specifications of the read-out, data acquisition (DAQ) and control systems of the array.

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.

Abstract The Maser Monitoring Parkes Project (M2P2) is an ongoing project to observe masers towards high mass star forming regions (HMSFRs) using the 64m CSIRO Parkes radio telescope, Murriyang. In this paper we outline the project and introduce Stokes-I data from the first two years of observations. For the 63 sightlines observed in this project we identify a total of 1514 individual maser features: 14.4% of these (203) towards 27 sightlines show significant variability. Most of these (160/203) are seen in the main-line transitions of OH at 1665 and 1667 MHz, but this data set also includes a significant number of variable features in the satellite lines at 1612 and 1720MHz (33 and 10 respectively), most of which (24 and 9 respectively) appear to be associated with the HMSFRs. We divide these features into 4 broad categories based on the behaviour of their intensity over time: flares (6%), periodic (11%), long-term trends (33%) and ‘other’ (50%). Variable masers provide a unique laboratory for the modelling of local environmental conditions of HMSFRs, and follow-up publications will delve into this in more detail.

Experimental results are presented on high energy cosmic-ray hadron interactions recorded in homogeneous-type thick lead chambers (total thickness being 60 cm and 110 cm) exposed at the Pamirs (atmospheric depth 595 g/ cm2). High energy cosmic-ray hadron flux is measured. The attenuation mean free path of the arriving cosmic-ray hadrons of Ehγ ≥ 6 TeV measured in the chamber is obtained as 252 ± 30 g/cm2 of lead. However, for the high energy hadrons (E(γ) ≥ 10 TeV) constituting cosmic-ray families of the highest energy range, ΣE(γ) ≥ 700 TeV, which have been accumulated so far in the series exposures at the Pamirs and analysed by MSU group, the attenuation mean free path of hadrons in lead has turned out to be as short as 170−26+47 g/cm2 with 95% CL by the maximum likelihood method. The present experimental result of such a short attenuation length of hadrons in cosmic-ray families is essentially consistent with that obtained for high energy hadrons (E(γ) ≥ 10 TeV) constituting the “Chiron-type” families of ΣE(γ)>100 TeV in the Chacaltaya two-storeyed chamber experiments. The anomalous transition characteristics of high energy hadrons in lead is found and examples are presented. The physical significance of the experimental results on extremely high energy hadron interactions is discussed.

The Baikal Neutrino Telescope has been operating in its NT200 configuration since April, 1998. The telescope has been upgraded in April, 2005 to the 10 Mton scale detector NT200+. It's main physics goal is the detection of signals from high energy neutrino cascades. NT200+ reaches a 3-year sensitivity of 2×10-7cm-2s-1sr-1GeV for an all-flavor diffuse cosmic E-2 neutrino flux for energies 102TeV–105TeV. Design and sensitivity of NT200+ are described. NT200+ is forming the basic building block of a future km3-scale (gigaton-volume) Baikal Telescope. Research and development work on that next stage detector has started.

We discuss the prospects to use a novel photon detector — the so-called SiPM — for the high energy astroparticle physics experiments EUSO and MAGIC. We explain the principle of these photon sensors and present results obtained with some prototypes. Peak photon detection efficiency (PDE) of the devices available is currently about 20%. Already in its existing form Geiger mode APDs offer a very promising replacement candidate for conventional photomultiplier tubes (PMTs) in both experiments, provided some improvements can be achieved.

We discuss the silicon photomultiplier as a novel photon detector for the Major Atmospheric Gamma Imaging Cerenkov Telescope and the Extreme Universe Space Observatory. For these astroparticle experiments we pursue two different developments of the SiPM. One development is pursued at MEPhI, where prototypes are available. In the course of this paper we will describe some characteristics of these devices. The second development, which is using the back illumination principle is at present in its design phase.

For about ten years the collaboration MEPhI-Max Plank Institute for Physics in Munich has been developing SiPMs for the MAGIC and EUSO astro-particle physics experiments. The aim was to develop UV sensitive sensors of very high photon detection efficiency, substantially exceeding that of the classical photo multiplier tubes. For very high photo detection efficiency one needs to operate SiPM under the highest Geiger efficiency, i.e., to apply a high over-voltage. This means operating SiPM under high gain that in its turn produces a very high cross-talk. For suppressing the latter adverse effect we used isolating trenches and a second p–n junction, but also special implantation profiles and layers. We produced UV sensitive SiPMs of sizes 1 mm×1 mm and 3 mm×3 mm showing a peak Photon Detection Efficiency in the range of 50–60% at a cross-talk level of only 3–5%. One of the outstanding features of the new SiPM is their extremely low sensitivity of gain to temperature variations, amounting to 0.5%/°C. Below we report on new SiPMs.

We present a status of the Baikal-GVD Project. The objective of this project is a construction of a km3-scale neutrino telescope in the Lake Baikal. As an important milestone, the first GVD engineering array has been deployed and ran in April, 2011. Application of a completely new technology gave us an opportunity to study all the basic elements of the future full detector and to finalize the GVD technical design. We discuss the configuration and the design of the engineering array as well as data performance with the preliminary results.

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.

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 . TAIGA will be located in the Tunka valley, ∼ 50 km West from Lake Baikal. The different detectors of the TAIGA will be grouped in 6 arrays to measure Cherenkov and radio emission as well as electron and muon components of atmospheric showers. The combination of the wide angle Cherenkov detectors of the TAIGA-HiSCORE array and the 4-m Imaging Atmospheric Cherenkov Telescopes of the TAIGA-IACT array with their FoV of 10×10 degrees and underground muon detectors offers a very cost effective way to construct a 5 km2 array for gamma-ray astronomy.

It is planned that new TAIGA-Muon detectors will complement the existing Tunka-GRANDE facility of scintillation detectors of the TAIGA gamma-observatory in the Tunka valley, Russia. The new design of scintillation detector with wavelength shifting bars and PMTs is developed. The first prototype of the counter was installed and tested using infrastructure of the Tunka-GRANDE installation in 2017. The mass production of counters has begun in 2018 at the Novosibirsk State University.

The combination of a wide angle timing Cherenkov array and Imaging Atmospheric Cherenkov Telescopes operated in mono mode offers a cost-effective way to construct a few square kilometers array for ultrahigh-energy gamma astronomy. The first stage of the TAIGA Observatory (Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy) is described here. It will comprise TAIGA-HiSCORE - 120 wide angle Cherenkov stations distributed over an area of 1.0 km2 and three IACTs (TAIGA-IACT).

The performance of the 200×2.5×1cm3 plastic scintillator strip with wavelength shifting fiber read out by two novel photodetectors called Silicon PhotoMultipliers (SiPMs) is discussed. The advantages of SiPM relative to the traditional multichannel photomultiplier are shown. Light yield and light attenuation measurements are presented. This technique can be used in muon or calorimeter systems.

The Silicon Photomultiplier (SiPM) is intrinsically a very fast device, its single photoelectron timing resolution is about 100 ps FWHM. Therefore real timing properties of the system scintillator+SiPM is determined mostly by timing properties of the scintillator+light collection system. We present the experimental results for timing properies of SiPM+scintillator (or Cherenkov radiator) for two cases: (1) timing resolution in a few GeV electron beam with fast plastic scintillator or Cherenkov radiator+SiPMs with a size of 1×1 mm2 and 3×3 mm2 and (2)time-of-flight resolution for detection of 511 KeV photons by two LSO crystals+SiPM (3×3 mm2), as a possible application for PET.

We present the results of our search for neutrino events coinciding in time and direction with gamma-ray bursts (GRBs) with the Baikal underwater neutrino telescope NT200. No events confirming a neutrino accompaniment of GRBs have been detected. Model-independent limits (Greens function) on the neutrino flux from GRBs have been obtained. For the Waxman-Bahcall neutrino spectrum, the limit on the neutrino flux from a GRB has been found to be E 2 Φ ν ⩽ 1.1 × 10−6 GeV cm−2 s−1 sr−1.

The Silicon Photomultiplier (SiPM) is a promising photo-detector for a variety of applications. However, the high dark count rate (DCR) of the SiPM is still a contemporary problem. Decreasing the DCR would significantly broaden the range of possible applications. In this work we present a novel method for the spatially resolved characterization of crystal defects in SiPMs. The contribution of crystal defects to the DCR is evaluated by exploiting the effect of "hot carrier luminescence" (HCL), which is light that is emitted during the Geiger mode operation of avalanche photodiodes (SiPM micro-cells). Spatially confined regions with an enhanced light emission intensity (hotspots) are identified within the active areas of SiPM micro-cells. By correlating the detected light intensity and the DCR, a significant contribution of up to 56 % of the DCR can be attributed to less than 5 % of the micro-cells. The analysis of the temperature dependence of the emitted light identifies the Shockley-Read-Hall-Generation to be the dominant mechanism responsible for the occurrence of hotspots. The motivation of this work is to generate a deeper understanding of the origin of hotspots in order to suppress their contribution to the DCR of SiPMs.

This paper presents results obtained with the combined CALICE Scintillator Electromagnetic Calorimeter, Analogue Hadronic Calorimeter and Tail Catcher & Muon Tracker, three high granularity scintillator-silicon photomultiplier calorimeter prototypes. The response of the system to pions with momenta between 4 GeV/c and 32 GeV/c is analysed, including the average energy response, resolution, and longitudinal shower profiles. Two techniques are applied to reconstruct the initial particle energy from the measured energy depositions; a standard energy reconstruction which is linear in the measured depositions and a software compensation technique based on reweighting individually measured depositions according to their hit energy. The results are compared to predictions of the GEANT 4 physics lists QGSP_BERT_HP and FTFP_BERT_HP.

An exotic cosmic-ray family event is observed in the large emulsion chamber exposed by the joint at the Pamirs (4360 m above sea level). The family is composed of 120γ-ray-induced showers and 37 hadron-induced showers with individual visible energy exceeding 1 TeV. The decisive feature of the event is the hadron dominance: ΣEγ, ΣE(γ)h, 〈Eγ, 〈E(γ)h〉, 〈Eγ·Rγ〉 and 〈E(γ)·Rh〉 being 298 TeV, 476 TeV, 2.5 TeV, 12.9 TeV, 28.6 GeV m and 173 GeV m, respectively. Most probably the event is due to a Centauro interaction, which occured in the atmosphere at ∼700 m above the chamber. The event will constitute the second beautiful candidate for a Centauro observed at the Pamirs.

A project of the NT1000 deep-water neutrino telescope with an effective volume of ∼1 km3 is currently being developed by the BAIKAL collaboration. The telescope will be located in Lake Baikal in close vicinity of the NT200+ detector, which is currently in operation. The telescope will be composed of 12 clusters with 8 similar strings of optical modules in each (each string has two sections of the NT1000 optical modules). The section of the NT1000 optical modules has been developed using higher-efficiency photomultiplier tubes and state-of-the-art electronics. The field tests of the experimental string consisting of two sections with six optical modules in each have been performed. The results of these investigations are used in the project of the NT1000 neutrino telescope and in the hydrological study of Lake Baikal.

We present the current status of high-energy cosmic-ray physics and gamma-ray astronomy at the Tunka Astrophysical Center (AC). This complex is located in the Tunka Valley, about 50 km from Lake Baikal. Present efforts are focused on the construction of the first stage of the gamma-ray observatory TAIGA - the TAIGA prototype. TAIGA (Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy) is designed for the study of gamma rays and charged cosmic rays in the energy range 1013 eV–1018 eV. The array includes a network of wide angle timing Cherenkov stations (TAIGA-HiSCORE), each with a FOV = 0.6 sr, plus up to 16 IACTs (FOV - 10∘× 10∘). This part covers an area of 5 km2. Additional muon detectors (TAIGA-Muon), with a total coverage of 2000 m2, are distributed over an area of 1 km2.

The spatial development of hadronic showers in the CALICE scintillator-steel analogue hadron calorimeter is studied using test beam data collected at CERN and FNAL for single positive pions and protons with initial momenta in the range of 10–80 GeV/c. Both longitudinal and radial development of hadron showers are parametrised with two-component functions. The parametrisation is fit to test beam data and simulations using the QGSP_BERT and FTFP_BERT physics lists from GEANT4 version 9.6. The parameters extracted from data and simulated samples are compared for the two types of hadrons. The response to pions and the ratio of the non-electromagnetic to the electromagnetic calorimeter response, h/e, are estimated using the extrapolation and decomposition of the longitudinal profiles.

The TAIGA complex-detector is designed to study gamma and cosmic rays in the energy range above 30 TeV. We are developing a novel wide-angle imaging air Cherenkov telescope with a SiPM based camera with a field of view of 15–20o and an aperture of around 1 m2. In this report we present the design of the telescope imaging camera (optical and data acquisition systems), based on 1000–1200 SiPMs. The prototype of such camera, based on 49 SiPMs, is operating at the TAIGA's site in the Tunka valley since September 2019. The design of the prototype and the preliminary results of data analysis is presented.

We review the present status of the Baikal Neutrino Project and present preliminary results of a search for upward going atmospheric neutrinos, WIMPs and magnetic monopoles obtained with the detector NT-2000 during 1998. Also the results of a search for very high energy neutrinos with partially completed detector in 1996 are presented.

We review the present status of the Baikal Neutrino Project and present the results obtained with the deep underwater neutrino

Abstract In recent years, a few scientific groups are developing a novel type light sensor. These so-called silicon photo multipliers (SiPM) operate at relatively low bias voltage of 20–60 V, show unprecedented amplitude resolution and already now can provide photon detection efficiencies (PDE) comparable to or better than that of classical photo multipliers (PMT). We are developing the novel sensors for the astro-particle physics experiments MAGIC [J. Albert, et al., Astrophys. Lett. 642 (2006) L119. [6] ] and also for EUSO [M. Teshima, et al., EUSO (The Extreme Universe Space Observatory), in: Scientific Objectives Proceedings ICRC, 2003, p. 10690. [7] ]. The front-illuminated SiPM are developing with the group from MEPhI in Moscow and the back-illuminated Avalanche Drift Diodes (ADD) with the semiconductor laboratory (HLL) attached to the MPI for Physics. Our goal is to produce 5–10 mm size ultra-fast, low-noise and very high PDE (60–80%) sensors operating in the wavelength range 300–600 nm. Together with MEPhI, we have already produced and successfully tested 1.3×1.3, 3×3 and 5×5 mm 2 size SiPMs. Very recently, the first ADD test structures were produced and are under evaluation at the HLL. In this report, we want to outline the main parameters of the new sensors for the needs of astro-particle physics experiments.

In the recent twenty five years the technique of imaging atmospheric Cherenkov telescopes for ground-based very high energy gamma-ray astrophysics has emerged and rapidly established itself as a new powerful discipline in science. The next generation large instrument, known under the name Cherenkov Telescope Array, will soon move from the prototyping into the construction phase. Its sensitivity will be an order of magnitude higher than that of the currently leading instruments VERITAS, H.E.S.S. and MAGIC. Currently, the standard light sensors for IACTs are the classical photo multipliers. Since very recently photo multipliers with a peak quantum efficiency of 40% are becoming available. In addition, also the photo electron collection efficiency on the first dynode has been increased to ~95-98%, providing a photon detection efficiency that is almost as high as the quantum efficiency. SiPMs, also known as MPPC, GAPD, Micro-channel APD, are novel semiconductor light sensors that are rapidly maturing. Compared to photo multiplier tubes the currently best SiPM have comparable photon detection efficiency, better amplitude and time resolution, but much worse noise. Their parameters are steadily improving and sometime in the future they may become almost ideal light sensors, substituting classical photo multiplier tubes in many applications. Also in astrophysics they can find wide applications. In this report we will dwell on the potential and advantages of using SiPM for Cherenkov telescopes.

Observations of gamma rays up to several 100 TeV are particularly important to spectrally resolve the cutoff regime of the long-sought Pevatrons, the cosmic-ray PeV accelerators. One component of the TAIGA hybrid detector is the TAIGA-HiSCORE timing array, which currently consists of 28 wide angle (0.6 sr) air Cherenkov timing stations distributed on an area of 0.25 km2. The HiSCORE concept is based on (non-imaging) air shower front sampling with Cherenkov light. First results are presented.

A dedicated single-cell SiPM structure is designed and measured to investigate the radiation damage effects on the gain and turn-off voltage of SiPMs exposed to a reactor neutron fluence up to Φ = 5e13 cm−2. The cell has a pitch of 15μm. The fluence dependence of gain and turn-off voltage are reported. A reduction of the gain by 19% and an increase of Voff by ≈0.5 V is observed after Φ = 5e13 cm−2.

The concept of the TAIGA experiment is to combine wide-angle timing and imaging Cherenkov telescopes as well as electron and muon detectors. The TAIGA facility aims at gamma-ray astrophysics at energies from a few TeV to several PeV and cosmic-ray physics from 100 TeV to several EeV but also pursues searches for astrophysical nanosecond transients, axion-like particles, Lorentz invariance violation and other unexpected manifestations of New Physics. TAIGA-1, a hybrid detector complex with an area of 1 km2, operating since 2021 in the Tunka valley, 50 km to the West from the southernmost tip of lake Baikal, and the plans for its upgrade are presented.

Measurements of optical properties in media enclosing Cherenkov neutrino telescopes are important not only at the moment of the selection of an adequate site, but also for the continuous characterization of the medium as a function of time. Over the two last decades, the Baikal collaboration has been measuring the optical properties of the deep water in Lake Baikal (Siberia) where, since April 1998, the neutrino telescope NT-200 is in operation. Measurements have been made with custom devices. The NEMO Collaboration, aiming at the construction of a km3 Cherenkov neutrino detector in the Mediterranean Sea, has developed an experimental setup for the measurement of oceanographic and optical properties of deep sea water. This setup is based on a commercial transmissometer. During a joint campaign of the two collaborations in March and April 2001, light absorption, scattering and attenuation in water have been measured. The results are compatible with previous ones reported by the Baikal Collaboration and show convincing agreement between the two experimental techniques.

We review the present status of the Baikal Neutrino Project and present selected results obtained from data taken in 1998 - 2000 (780 live days). We describe the moderate upgrade of NT-200 planned for the next years and discuss a possible detector on the Gigaton scale.

Connective tissue growth factor (CTGF) is a secreted protein that is strongly induced in human and experimental heart failure.CTGF is said to be profibrotic; however, the precise function of CTGF is unclear.We generated transgenic mice and rats with cardiomyocyte-specific CTGF overexpression (CTGF-TG).To investigate CTGF as a fibrosis inducer, we performed morphological and gene expression analyses of CTGF-TG mice and rat hearts under basal conditions and after stimulation with angiotensin II (Ang II) or isoproterenol, respectively.Surprisingly, cardiac tissues of both models did not show increased fibrosis or enhanced gene expression of fibrotic markers.In contrast to controls, Ang II treated CTGF-TG mice displayed preserved cardiac function.However, CTGF-TG mice developed age-dependent cardiac dysfunction at the age of 7 months.CTGF related heart failure was associated with Akt and JNK activation, but not with the induction of natriuretic peptides.Furthermore, cardiomyocytes from CTGF-TG mice showed unaffected cellular contractility and an increased Ca 2+ reuptake from sarcoplasmatic reticulum.In an ischemia/reperfusion model CTGF-TG hearts did not differ from controls.Our data suggest that CTGF itself does not induce cardiac fibrosis.Moreover, it is involved in hypertrophy induction and cellular remodeling depending on the cardiac stress stimulus.Our new transgenic animals are valuable models for reconsideration of CTGF's profibrotic function in the heart.

The first stage Baikal Neutrino Telescope NT200 has been operating since 1998 and was upgraded to the 10 Mton detector NT200+ in 2005. The preparation towards a development of a km3-scale detector in Lake Baikal is currently a central activity point. As an important milestone a km3-prototype Cherenkov string, based on completely new technology, was installed in 2008 and has been successfully operating together with NT200+. It was upgraded in April 2009. Also, we review the status of high-energy acoustic neutrino detection activities in Lake Baikal.

The construction of a km 3 -scale neutrino telescope -the Gigaton Volume Detector (GVD) in Lake Baikal -is the central goal of the Baikal collaboration.During the R&D phase of the GVD project in 2008-2010 years the basic elements of GVD -new optical modules, FADC readout units, underwater communications and trigger systems -have been developed, produced and tested in situ by long-term operating prototype strings in Lake Baikal.The prototyping phase of the GVD project has been started in April 2011 with the installation of a three string array (prototype cluster) which comprises all basic elements and systems of the GVD-telescope in Lake Baikal.We describe configuration and technical design of the GVD, present selected results obtained during 2008-2010 with prototype strings, and describe configuration and design of the 2011 prototype cluster.

The amplitude and timing properties of a Geiger discharge in a stand-alone SiPM cell have been investigated in detail. Use of a single stand-alone SiPM cell allows us to perform measurements with better accuracy than the multicell structure of conventional SiPMs. We have studied the dependence of the output charge and amplitude from an SiPM cell illuminated by focused light vs the number of primary photoelectrons. We propose a SPICE model which explains the amplitude over saturation (when the SiPM׳s amplitude is greater than the sum over all cells) characteristics of SiPM signals for more than one initial photoelectrons. The time resolutions of a SiPM cell have been measured for the case of single (SPTR) and multiphoton light pulses. The Full Width Half Max (FWHM) for SPTR has been found to be at the level of 30 ps for focused and 40 ps for unfocused light (100 μm cell size).

In special tests, the active layers of the CALICE Digital Hadron Calorimeter prototype, the DHCAL, were exposed to low energy particle beams, without being interleaved by absorber plates. The thickness of each layer corresponded approximately to 0.29 radiation lengths or 0.034 nuclear interaction lengths, defined mostly by the copper and steel skins of the detector cassettes. This paper reports on measurements performed with this device in the Fermilab test beam with positrons in the energy range of 1 to 10 GeV. The measurements are compared to simulations based on GEANT4 and a standalone program to emulate the detailed response of the active elements.

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.

Abstract The EAS Cherenkov array Tunka-133, with about 3 km 2 sensitive area, has been installed in the Tunka Valley, Siberia. The accessible energy range is 10 15 –10 18  eV. In this contribution, a description of the array and main results obtained so far are presented. A current update of the array includes the deployment of scintillation stations, radio antennas, as well as optical stations. The deployments of these optical stations are the first step towards Tunka-HiSCORE, a wide-angle, large field-of-view gamma-ray telescope.

Extremely low dose, fast human-screening systems constitute a vital instrument in a modern world under terrorist threats. Only X-ray scanners provide visualization of concealed items hidden under clothing or inside the body. However, existing systems are inadequate in many large-crowd scenarios (including public transport) because of restrictions on dose load per person. The main aim of this paper is to develop an alternative system that provides satisfactory control. X-ray counting with energy resolution is recognized as the most promising technique to achieve the maximum sensitivity of X-ray detection. Therefore, combining the high sensitivity of silicon photomultiplier (SiPM) to low-intensity light pulses with the high X-ray detection efficiency of modern fast inorganic scintillators, we are developing a prototype low-dose X-ray energy-resolved counting system for routine security purposes. Such an approach allows a reduction in the absorbed dose in a human body and can also improve the image quality for the typical doses currently used in the conventional X-ray systems. Moreover, a charge integration mode for high-intensity X-ray can extend the dynamic range of the system. In this paper, we present results obtained using a mature SiPM-based fast scintillation detector proof-of-concept prototype, incorporating an extremely low-dose X-ray scanner in counting mode, with energy discrimination.

The TAIGA-Muon scintillation array is located in the Tunka Valley. It is a part of the single TAIGA experimental complex. Its construction has started in the summer of 2019. By the autumn of 2019, the first three clusters were installed. We describe the design of the TAIGA-Muon array, the data acquisition (DAQ) sistem, reading and control systems.

The physical motivations and performance of the TAIGA (Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy) project are presented.The TAIGA observatory addresses ground-based gamma-ray astronomy and astroparticle physics at energies from a few TeV to several PeV, as well as cosmic ray physics from 100 TeV to several EeV.The pilot TAIGA complex is located in the Tunka valley, ~50 km West from the southern tip of the lake Baikal.It includes the air Cherenkov light integrating TAIGA-HiSCORE array with 120 wideangle optical stations distributed over on area of ~1 km 2 and three 4-m class Imaging Atmospheric Cherenkov Telescopes of the TAIGA-IACT array.The latter array has a shape of a triangle with side lengths of about 300m, 400m and 500m.The expected integral sensitivity of the 1 km 2 TAIGA detector will be about 2,5 × 10 -13 TeV cm -2 sec -1 for detection of E ≥ 100 TeV gamma-rays in 300 hours of observations.The combination of the wide angle Cherenkov array with IACTs offers a cost-effective way to build a really large (up to 10 km 2 ) array for very high energy gamma-ray astronomy.The reconstruction of the given EAS energy, incoming direction and the core position, from the TAIGA-HiSCORE data, allows one to increase the distance between the relatively expensive IACTs of to 600-800 m.These, together with the surface and underground electron/muon detectors will be used for selection of gamma-ray induced EAS.Present status of the project, together with the current array description and the first experimental results and plans for the future are presented.

The physics motivations and advantages of the hybrid detector complex TAIGA are presented. TAIGA aims to address gamma-ray astronomy at energies from a few TeV to several PeV units, as well as cosmic-ray physics from 100 TeV to several EeV units and astroparticle physics problems. In 2021 deployment and commissioning of the one square kilometer TAIGA setup in the Tunka valley $$\sim$$ 50 km West from Lake Baikal will be finished. The first experimental results with the TAIGA are presented.

We review the present status of the Lake Baikal neutrino experiment and present selected physics results obtained during the consecutive stages of the stepwise upgrade of the detector: from NT-36 to NT-96. The results cover atmospheric muons, neutrino events, neutrinos of very high energy, searches for neutrino events from WIMP annihilation, searches for magnetic monopoles, and environmental studies. We also describe an air Cherenkov array developed for studying the angular resolution of NT-200.