BNO INR RAS - Laboratory Baksan underground scintillation telescope.

Academician G.T. Zatsepin and Doctor of Physical and Mathematical Sciences S.P. Mikheev. Most of the work is carried out jointly with the Department of High Energy Leptons and Neutrino Astrophysics at INR. BAKSAN UNDERGROUND SCINTILLATION TELESCOPE (BPST) In 1978, the 3200-channel underground scintillation telescope (UST), one of the largest underground installations of that time, was launched. In the 80s - 90s, its modernization began - an additional recording layer was installed, a second line for recording events was being manufactured, construction of the ANDYRCHI installation above the telescope and a muon detector under the COVER installation were underway. BPST is a multi-purpose underground installation designed to solve a wide range of problems in astrophysics, particle physics and cosmic rays (cosmic rays). The telescope is located in a mine opening with a volume of 12,000 cubic meters. meters at a distance of 550m from the beginning of the horizontal tunnel.

The effective thickness of the soil above the telescope is 850 g/cm2. The installation is a four-story building with a base area of (16.7 * 16.7) m2 and a height of 11.1 m. The telescope building is assembled from concrete blocks 0.8 m thick, made of low-radioactive concrete based on ultramafic rocks (dunites). Interfloor ceilings 0.8 m thick are covered with fine fractions of dunite crushed stone (150 g/cm2). Six outer and two inner recording layers (four horizontal and four vertical layers) are made from standard liquid scintillation detectors. The total number of detectors is 3,180, and the total weight of the scintillator in them is ~ 330 tons The standard module is an aluminum container with dimensions (0.7 * 0.7 * 0.3) m3, filled with a liquid scintillator based on white spirit with the additions of PPO (1 g/l) and POPOP (0.03 g/l).

The inner surface is covered with white enamel, which diffusely reflects light. The detector volume is viewed by one photomultiplier tube FEU-49 with a photocathode diameter of 0.15 m. The passage of a charged relativistic particle is accompanied by an energy release of ~50 MeV, which corresponds to the appearance of a signal with an amplitude of 70 mV at the anode of the photomultiplier at a load of 75 Ohms. The anode signals of the detectors of each layer are summed sequentially into groups of 25, 100 and 400 detectors. In addition to the signal from the anode, information is taken from the 5th and 12th dynodes and is supplied, respectively, to the amplitude (A) - time (T) converters and the integral discriminator located on the PMT casing. The threshold of the "A - T" converter corresponds to the passage of ten relativistic particles through the detector, and the dynamic range of the time-amplitude converter is ~2 * 103. The threshold of the integral discriminator corresponds to an energy release of 10 MeV.

Signals from individual "A - T" converters, integral discriminators and anode signals from groups of detectors of each layer of the telescope are supplied to recording devices located in the equipment room for: determining the coordinates of the detectors through which the particles passed; measurements of the relative time of flight of a particle through the telescope layer (accuracy 2 ns); measurements of energy releases in individual detectors in the range of 0.05 - 1000 GeV; measurements of energy releases in a separate plane from 10 MeV to several tens of TeV; recording the shape of the anode signals of each layer for rare events.