Search

The Baksan Underground Scintillation Telescope has been operating under the program of searching for neutrino bursts since the middle of 1980. The target is two parts of the facility with the total mass of 240 t. The actual observation time over the period from June 30, 1980, to December 31, 2016, is 31.27 years. No candidate for the stellar core collapse has been detected during the observation period. The upper bound for the mean rate of the supernova core collapse in our Galaxy is 0.074 y $$^{{ - 1}}$$ (90% CL).

The characteristics of fast neutrons produced by cosmic-ray muons at the Baksan Underground Scintillation Telescope (BUST) are investigated. A novel approach to the problem consists in estimating the neutron flux by the production rate of the unstable radioactive nuclide 12B in the (n, p) reaction on carbon nuclei of the BUST organic scintillator. The processing of the data collected in 2002–2015 yielded $${N_{{{12}_B}}} = 337 \pm 2.5$$ events consistent with those of the reaction 12C(n, p)12B. For the BUST internal planes, the background of fast neutrons with E > 28.6 MeV is experimentally estimated as Φ ∝ 10−11cm–2 s–1. This is lower than the theoretically predicted total neutron flux by nearly two orders of magnitude. The disagreement with predictions is attributed to the suppression of neutron flux in the external scintillator planes of the detector.

The Baksan Underground Scintillation Telescope has operated within the program of searching for neutrino bursts since the mid-1980s. We present the current status of the experiment and some results related to the investigation of background events and the stability of facility operation. Over the period from June 30, 1980, to December 31, 2016, the pure observation time was 31.27 years. No neutrino burst candidate event from the explosion of a core-collapse supernova in the Galaxy was recorded in this time. This sets an upper bound of 0.074 yr–1 on the mean frequency of gravitational stellar collapses in the Galaxy at a 90% confidence level.

The MMIS-32 scaled multichannel measurement system, which is based on 32-channel charge-to-digital converters and has been developed and built, is described here. This system is intended for data acquisition from arrays of silicon photomultipliers used as multichannel photosensors in scintillation detectors. The basic parameters of the measurement system are presented.

Preliminary results of a neutron background measurement at the Baksan underground scintillation telescope (BUST) are presented. The external planes of the BUST are fully covered with standard scintillation detectors shielding the internal planes and suppressing thus background events due to cosmogenic and local radioactivity. The shielded internal planes were used as target for the neutron flux registration. The experimental method is based on the delayed coincidences between signals from any of the BUST counters. It is assumed that the first signal is due to inelastic interaction of a neutron with the organic scintillator, while the second signal comes from the decay of an unstable radioactive isotope formed when the fast neutron interacts with the 12C nuclei. Using the Monte-Carlo method (GEANT4) we also simulated propagation of neutrons through a layer of scintillator. The experimentally found muon induced neutron flux is j =1.3-0.3+0.7 ×10-10cm-2s-1 for neutron energies E ≥ 22MeV, which is in a qualitative agreement with similar measurements of other underground laboratories as well as with predictions of the GEANT4.

The current status of the experiment on recording neutrino bursts from core collapse stars is presented. The actual observational time is 29.76 years. An upper bound of the mean frequency of core collapse supernovae in our Galaxy is f col < 0.077 year–1 (90% CL).

A way of estimating a muon-enduced neutron flux has been proposed. The technique is used to estimate the neutron background at the Baksan Underground Scintillation Telescope (BUST). A two-pulse signature (unstable 12B production and its subsequent decay) is used to identify neutron events. The integrated average neutron flux on the external planes of detector is an order of magnitude higher than the one on the internal planes. Within the limits of statistical error, the resulting neutron flux agrees with predictions from simulations for the depth at which the BUST lies using the FLUKA program.

The search for muon neutrinos with energy ≥1 GeV correlated with Gamma-Ray Bursts (GRBs) has been carried out at the Baksan Underground Scintillation Telescope (BUST). Between 1978 December and 2013 December more than 1500 localized gamma-ray bursts occurred in the field of view of the BUST were coincided with the BUST operation periods. No neutrino signal from GRBs was detected. Upper limits on associated gamma-ray burst neutrino production are presented.

The origin of gamma-ray bursts is still one of the unresolved problems in physics. They are short, intense, and non-repeating flashes of MeV gamma-rays with a wide range of spectral and temporal properties. Also these bursts are perhaps sources of neutrino emission. Unlike the photons, which may scatter or be absorbed, the neutrinos, due to their small interaction cross section, arrive at the Earth unaffected. This paper describes experimental methods for detection of low energy neutrinos in the range from 20 MeV to 100MeV at the Baksan Underground Scintillation Telescope. In the analysis we search neutrinos in time coincidence with a gamma-ray burst. We use filtered data collected at the Telescope during 2012. We also use the catalogue of gamma-ray bursts of the SWIFT satellite experiment.

The current status of the experiment on recording neutrino bursts is presented. As the target, we use two parts of the facility with the total mass of 240 tons. Over the period of June 30, 1980 to December 31, 2016, the actual observational time is 31.27 years. No candidate for the stellar core collapse has been detected during the observation period. An upper bound of the mean frequency of core collapse supernovae in our Galaxy is f < 0.074 per year (90% CL).

The results from a 29-month investigation into the EAS electromagnetic component using the PRISMA-32 array are presented, notably for the central density spectrum and energy deposit spectrum. The array consists of 32 en-detectors in which specialized inorganic scintillators (SL6-5 phosphorus composition) based on silver-activated zinc sulfide (ZnS) with LiF enriched to 90% 6Li (ZnS(Ag) + 6LiF) are used as detecting layers. The possibility of detecting the electromagnetic component using a thin scintillation neutron detector with the multiple passage of charged particles is shown. The experimental data are compared to the results from simulations.

The matrices formed of silicon photomultipliers (SiPMs) are very promising photosensors for the scintillation detectors. The use of SiPM matrices with appropriate optical collector gives, in principle, a possibility to do a snapshot of glowing track of charged particle traversing a scintillator. The prototype of such scintillation detector is under development now in INR RAS. The preliminary results of characterization study of the matrix ArrayC-60035-64P-PCB (SensL company) for the prototype of such detector are presented., Poster contribution to the International Conference on New Photo-detectors (July 6-9, 2015, Moscow, Troitsk, Russia), to be published in PoS (PhotoDet2015)

A method is proposed for automatic tuning and stabilization of the energy threshold in scintillation detectors by maintaining the constancy of the average detector counting rate from Γ rays of natural radiation background or cosmic rays. Stabilization is automatically performed by controlling the photodetector supply voltage, which makes it possible to stabilize the detector threshold with an error of 0.73–2.40%, depending on the used circuitry. The stabilization electronics for scintillation detectors with avalanche multipixel photodiodes and photomultipliers is described. A circuit ensuring the increased precision of threshold stabilization is also proposed.

The first results of measurements of the thermal-neutron flux in extensive air showers (EASs) using an unshielded scintillation thermal-neutron detector in the Multicom prototype array at the Baksan Neutrino Observatory of the Institute for Nuclear Research are reported. The operating capacity of the new method for studying the EAS hadron component via detection of thermal neutrons and good prospects of this method are demonstrated.

The Andyrchy facility was created for studying the energy spectrum and nuclear composition of primary cosmic rays in the region of a knee in the cosmic-ray spectrum. The position of this facility above the Baksan underground scintillation telescope allows simultaneous detection of electron-photon and high-energy muon components of extensive air showers. The parameters of this facility also allow it to be used for solving a number of other problems of cosmic-ray physics. Data since 1996 have been collected for several physical problems. The facility is described, and its performance characteristics are presented.

A procedure for measuring energy releases in scintillation detectors by using a logarithmic RC converter in combination with a device that suppresses photomultiplier tube afterpulses is described. The total range of measured energies is 5.8 MeV to 11.6 GeV. The afterpulse suppression ratio is more than 200. The output pulse of the RC converter is synchronized with the leading edge of the anode signal from the photomultiplier tube.

Two circuits of wide-range converters of the dynode current amplitude of photomultiplier tubes (PMTs) into duration are presented. They are intended for measuring the energy released in large scintillation detectors. The first-type converter has a protective switch at the input, which eliminates the influence of PMT afterpulses on the conversion process. The second-type converter is weakly sensitive to PMT afterpulses, and its output pulse is synchronized with the leading edge of the input signal. Both devices have a dynamic range of 2 × 103.

The project of the Baksan Underground Scintil- lation Telescope (BUST) upgrade is presented. Additional outer layers of the detectors with fine spatial resolution will be mounted around BUST. Optimal dimensions of a counter, 0.125m◊ 0.125m◊ 0.03m were chosen with a simulation program. The functional diagram of BUSTs DAQ additional layers is presented. Modernization allows us to study the knee region using muon number spectrum measurements. BUST located underground at a depth of 850 m of wa- ter equivalent was designed to solve a number of physical problems which predetermined its construction and location (Alekseev et al., 1998). The telescope is a four-store building with dimensions of 16.7m◊ 16.7m◊ 11.1m and consists of four horizontal and four vertical planes. The total number of detectors is 3180. The analysis of the muon groups registered by BUST gives us an opportunity to obtain information about spectrum and composition of primary cosmic rays in the energy range of 1013 1016 eV (Petkov et al., 2008). The coordinates of fired detectors give the initial information for identification parameters of muon groups (arrival direction and number of muon tracks). In general, the number of muons cross- ing the telescope, n, and the number of the reconstructed muon tracks in a selected event, ntr, should not necessar- ily coincide with each other. When two or more muons are crossing BUST close enough to each other (comparable with the size of the detector), the number of reconstructed muon tracks will be less than the number of muons crossing BUST. Construction of additional external scintillation layers pro

An innovative method for studying the properties of extensive air showers (EASes) that is based on the detection of thermal neutrons generated by high energy hadrons under a soil absorber of 500 g cm−2 is proposed and tested. It is shown that underground hadronic calorimeter can be performed with special scintillation detectors developed by the authors. The method could be quite useful in gamma shower selection and investigations of EAS properties, primary cosmic ray mass composition, EAS core location, and so on.

Current status and results of the experiment on recording neutrino bursts are presented. The observation time (since 1980) is 22.6 years. The upper bound of collapse frequency in our Galaxy is 0.10 y i1 (90% CL).

Search for neutrino bursts from collapsing stars with the Baksan underground scintillation telescope has been carried out since 1980. In this study, the experimental data obtained during the period from 2001 to 2005 inclusive are analyzed. The upper limit of the mean frequency of collapses in the Galaxy over the entire period of observations (the total live time is 21.83 yr) was found to be 0.105 yr−1.

A signal of 5 events within 9.1 s was found in the Baksan scintillation telescope with a fiducial mass of 200 t at the KAMIOKANDE-II and IMB times on February 23, 1987. We have performed an analysis of the temporal distribution of the signals and obtained energy estimates of the signal. The properties of the Baksan events are very close to those of the KAMIOKANDE-II signal.

Since June 1980 a continual Galaxy observation to search for electron antineutrino signal accompanying a massive star core collapse and neutron star formation is running at the underground scintillation telescope of the INR Baksan Neutrino Observatory. There were no events undoubtedly interpreted as a collapse neutrino burst. However, the LSD group /1/, the KAMIOKANDE-II /2/ and the IMB /3/ collaborations reported the detection of the neutrino burst from the supernova 1987A in the Large Magellanic Cloud on February 23 at the times 2:52:36 UT, 7:35:35 UT and 7:35:41 UT respectively. In the fiducial mass (200 tons) of the Baksan telescope we observed only 1 event at the LSD time and a burst of 5 events spread over 9.1 seconds at the KAMIOKANDE-II — IMB time.