O. I. Mikhailova

Correlation of variations in the thermal neutron flux from the Earth’s crust with the Moon’s phases and with seismic activity

The results of the long-term recording of thermal neutron flux near the Earth’s surface with the use of an unshielded scintillation thermal-neutron detector are presented. The data obtained indicate the presence of periodic variations in the thermal neutron flux with the lunar diurnal and the lunar monthly periods. A hypothesis about the existence in the Earth’s crust of radon-neutron tidal variations in the concentration of thermal neutrons, correlated with the Moon’s phases and which have the gravitational origin, is formulated and confirmed experimentally. A simple mathematical model is proposed, which satisfactorily describes the observed variations. The case of the anomalous behavior of thermal neutrons is presented, which correlates with the high local seismic activity.

Underground hadronic calorimeter for EAS studies

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.

The Carpet-3 experiment to search for diffuse gamma rays with energies of more than 100 TeV

An experiment for measuring the flux of cosmic diffuse gamma rays with energies above 100 TeV (the Carpet-3 air shower array) is now being prepared at the Baksan Neutrino Observatory, Institute for Nuclear Research, Russian Academy of Sciences. The preparations entail a substantial increase of the areas of both the muon detector and the surface air shower array. The experiment’s sensitivity to showers generated by primary gamma rays is estimated for different configurations of the array. In addition, preliminary estimates of the upper limit on the flux of diffuse gamma rays with energies higher than 1.3 PeV, derived using experimental data from the old Carpet-2 array, are presented for a net exposure time of 9.2 years.

Hadrons with energies higher than 50 MeV in EASes with Ne = 105–107

Characteristics of the hadronic component of EASes with hadron energies Eh > 50 MeV were measured on the CARPET-2 complex shower array at the Baksan Neutrino Observatory of the Institute for Nuclear Research, Russian Academy of Sciences. Hadrons were registered using a 6-NM-64 neutron monitor; the data collection system of this array enables us to register the time intervals between pulses of neutron monitor counters with an error of up to 1 μs. For EASes with Ne = 105–107 whose axes are located in CARPET, we obtain the dependence of the mean neutron multiplicity in the neutron monitor on the total number of charged particles in the EAS.

Neutron multiplicity: Local hadronic showers and extensive air showers

A detailed analysis of events with neutron multiplicity M = 3−30 on neutron monitors (NMs) in Barentsburg (Spitsbergen), Baksan (North Caucasus), and Apatity (Murmansk region) is performed on the data obtained using a unique new data collection system. It is now possible for the first time to register local showers in cosmic rays on NMs and to investigate their structure with a high precision. Multiplicity on NMs is simulated using the GEANT4 Monte Carlo toolkit. Local hadronic cascades in the atmosphere with transverse sizes of 1 to 6 m were observed for the first time using the NM data. NM multiplicity generated by EAS hadronic cascades is studied on the data set on coupling NMs with the CARPET EAS facility.

The Carpet-3 air shower array for studying the knee region of the PCR spectrum

As a further development of the Carpet-2 air shower array [1], the Carpet-3 array [2, 3] is under construction at the Baksan Neutrino Observatory of Institute for Nuclear Research (Moscow). It is designed to study extensive air showers (EASes) around the knee region in energy spectrum of primary cosmic rays (PCRs). The array will simultaneously measure several (up to seven) EAS parameters, allowing us to analyze every event as a point in multi-dimensional space. By solving the inverse problem, the energy and atomic number of a primary particle will be determined from a set of these parameters. This work describes the current progress in constructing the array, and the physical problem to be solved by it is discussed.

Investigating hadronic cores of exstensive air showers at the CARPET-2 array

Characteristics of the hadronic component of exstensive air shower (EAS) trunks are investigated at the CARPET-2 array of the Baksan Neutrino Observatory, Institute for Nuclear Research, Russian Academy of Sciences. In this work, we study showers with axes that located within its muon detector (MD). We discuss the procedure for selecting such showers in our experiment. The relationship between the number of thermal neutrons detected by heat detectors installed in the muon detector’s tunnel and the total energy of a cascade generated by hadrons in the magnetic detector’s absorbent matter is presented.

Measurements of the thermal neutrons flux near the EAS core

The characteristics of the thermal neutrons flux have been measured near the EAS core at the Carpet-2 EAS array. The thermal neutron detectors were placed on the floor of the tunnel of the Muon Detector (MD) and showers with a core near the MD were selected. Thermal neutrons multiplicity spectrum has been obtained for these showers. Measurements of the lateral distribution function of thermal neutrons at distances of 1-16 m from the shower axis have been performed. The mean number of the recorded thermal neutrons as a function of the number of hadrons crossing the MD has been measured.

The Carpet-3 Multipurpose Air Shower Array of the Baksan Neutrino Observatory of the Institute for Nuclear Research, Russian Academy of Sciences

An experiment for measuring the flux of cosmic gamma rays with energy above 100 TeV is currently being prepared at the Baksan Neutrino Observatory of the Institute for Nuclear Research, Russian Academy of Sciences. For this purpose, based on the Carpet-2 shower array which has been operating for many years, the Carpet-3 multipurpose shower array is being constructed. In particular, the preparation of the experiment supposes an increase in the area of the muon detector (MD) and ground part of the array. For ground modules of the Carpet-3 array, a scintillation detector with a liquid scintillator in a plastic package has been elaborated. In this work, descriptions of the Carpet-3 array and working characteristics of the new scintillation detector are presented.