I. A. Shulzhenko

NEVOD-DECOR experiment: results and future

Russian-Italian NEVOD-DECOR experiment on the measurements of the local muon density spectra (LMDS) at various zenith angles gave possibility to obtain information on primary cosmic ray flux and interaction characteristics in a record wide energy range from 1015 to more than 1018 eV. Comparison of the measurement results with CORSIKA-based simulations showed the increase of LMDS slope at PeV energies of primaries (corresponding to the first knee); a trend to a heavier primary mass composition above the knee; indication for a second knee (a further increase of the spectrum slope near 1017 eV). At large zenith angles and high muon densities (corresponding to primary energies around 1018 eV) a considerable excess of muon bundle events in comparison with the expectation based on independent estimates of the primary spectrum and widely used hadron interaction models has been found. In 2011, a new phase of measurements of the energy spectrum of cascade showers initiated by high-energy muons in water and of the energy deposit of muon bundles at various zenith angles and muon multiplicities started. Further plans include the deployment of a traditional EAS array around the NEVOD-DECOR complex.

Measuring the spectrum of the local density of charged particles on the SCT setup

The first results from measuring spectra of the local density of charged particles in extensive air showers in the energy range of ∼1014–1015 eV on the SCT setup (part of the NEVOD experimental complex), obtained using two independent methods, are presented. Experimental data are compared to calculations performed using the CORSIKA program.

Application of the URAGAN muon hodoscope to calibrate charged particle detectors

Independent calibration of the charged particle detectors is often required in developing different devices for elementary particle physics. The use of the URAGAN muon hodoscope, created at MEPhI’s NEVOD Scientific and Educational Center, is described. The high accuracy of muon track reconstruction allows calibration and precision study of the sensitive working volume of such detectors.

Project of the URAN array for registration of atmospheric neutrons

The project of a new setup is directed at the registration of atmospheric neutrons (URAN) generated by hadronic component of extensive air showers (EAS). The setup includes 72 en-detector which simultaneously register two major EAS components: electromagnetic by the group passage of charged particles and hadron component by the thermal neutrons. The neutrons and charged particles are detected using a specialized scintillation composition made of granulated alloy of crystals based on the ZnS(Ag) powder with an admixture of B2O3.

Status of the NEVOD-EAS experiment

The NEVOD-EAS setup is designed for independent estimation of the EAS parameters recorded in the NEVOD-DECOR experiment in the region of the energy spectrum knee. The setup’s recording system is based on the clusters of scintillation detectors for the EAS electron-photon component, located on the territory of MEPhI. Characteristics of the shower array recording system that ensure detection, data acquisition and primary processing, and the time synchronization of clusters are discussed, along with results of studying the nonuniformity of NEVOD-EAS scintillation detector responses.

Proposal of NEVOD-EAS shower array

New setup for detection of EAS electromagnetic component at the knee region of primary energies is under construction on the basis of the experimental complex NEVOD (Moscow, Russia). The measuring system of the EAS array has a cluster organization. Clusters are located on the roofs of laboratory buildings of MEPhI (Moscow). Features of measuring and DAQ systems, results of investigations of characteristics of a single counter and the event formation algorithm from the data of separate clusters are discussed.

Muon Calibration of the Cherenkov Water Detector NEVOD

The problem of calibrating a Cherenkov water detector (CWD) and the possibilities for its use based on the example of the CWD NEVOD are discussed. Results of the calibration of quasi-spherical modules in water volume by means of vertical muons selected by scintillation telescopes and compared to the results from measurements performed at test facilities are presented.

Multisector scintillation detector with fiber-optic light collection

A new type of scintillation detector for the use in high energy physics is described. The octagonal detector consists of eight triangular scintillator sectors with total area of 1 m2. Each sector represents two plates of 2 cm thick plastic scintillator. Seven 1 mm thick WLS fibers are laid evenly between the plates. The space between the fibers is filled with silicone compound to provide better light collection. Fiber ends from all eight sectors are gathered in the central part of the detector into a bunch and docked to the cathode of a FEU-115m photomultiplier. The read-out of the counter signals is carried out from 7th and 12th dynodes, providing a wide dynamic range up to about 10000 particles. The front-end electronics of the detector is based on the flash-ADC with a sampling frequency of 200 MHz. The features of detecting and recording systems of the multisector scintillation detector (MSD) and the results of its testing are discussed.

Observing the second knee in the PCR spectrum in the region of 1017 eV using the method of local muon density spectra

The results from measuring EAS local muon density spectra at ultrahigh energies of primary particles are reported. These spectra are recorded by two instruments at the NEVOD experimental complex (MEPhI, Moscow). Muon bundles in inclined EAS at zenith angles exceeding 55° are registered by the DECOR coordinate detector. Mostly near-vertical muon bundles are registered at the bottom plane of scintillation counters in the calibration telescope system positioned underwater at a depth of approximately 9 m. The results from fitting the local muon density spectra measured by both instruments at primary particle energies below and above 1017 eV confirm the presence of the second knee (an increase in the slope) in the energy spectrum of cosmic rays in this region.

The URAN array for studying atmospheric neutrons

The URAN array is designed to study primary cosmic rays in the region of the knee by detecting neutrons produced as a result of interaction between EAS particles and nuclei in the atmosphere or matter near the installation. It consists of 72 detectors mounted on the roofs of experimental buildings and combined into cluster structures of 12 detectors. The registering element is scintillator based on natural boron. The area of each detector is 0.36 m2.