A.P. Chubenko

The influence of background radiation on the events registered in a neutron monitor at mountain heights

We have made an experimental check of an influence caused by external background of slow thermal neutrons on the temporal distribution of the signals from the standard NM64 supermonitor used as a detector of hadron component of extensive air showers with the energy above 1015 eV. Special attention in our study was paid to the possible connection of this background with the anomalously (up to a few milliseconds) delayed signals from the neutron monitor which were detected when the shower cores passed in its close vicinity. It has been found that in spite of the long, up to tens of milliseconds, presence of thermal neutrons nearby the shower axis, these external neutrons do not have any effect on the temporal behaviour of the neutrons diffusing inside the monitor as well as on the distribution of gamma-radiation accompanying the absorption of the latter.

A new method of ionization-neutron calorimeter for direct investigation of high-energy electrons and primary nuclei of cosmic-rays up to the “knee” region

Abstract A new technique of the Ionization Neutron Calorimeter (INCA) to be installed aboard a satellite or a space station is capable of opening new horizons for cosmic-ray physics. The main goal of the experiment proposed is studying local nearby sources of high-energy cosmic rays by measuring the spectrum and composition of the nuclear component with the energy resolution of better than 30% that is sufficient for solution of these problems in the energy range 0.1–10 PeV, i.e., in the so-called “knee” region, and the spectrum of primary electrons in the energy range 0.1–10 TeV with the proton-background suppression factor up to 107. In addition, this experiment can provide new information on the cosmic-ray gamma-radiation in the energy interval 30 GeV–1 TeV, neutrons and gamma-rays from solar flares, and the existence of very massive exotic charged particles in cosmic radiation. The INCA is a calorimeter combining properties of conventional ionization calorimeters and classical neutron monitors. It can measure both the ionization produced by charged particles and evaporation neutrons arising as a result of excitation of heavy-absorber nuclei by cascade particles. The advantages of the INCA are not only excellent electron–proton separation but a high geometry factor of about 2 m 2 sr / ton owing to the INCA optimized composition and shape, whereas conventional ionization calorimeters are usually limited by geometry factor on the order of 0.1 m 2 sr / ton . To verify the INCA concept, a prototype was constructed and exposed to pion and proton accelerator beams with energies of 4 and 70 GeV, respectively, and to an electron beam with an energy of 200–550 MeV. The experimental data obtained agree well with the results of a Monte Carlo simulation by the SHIELD code.

The modern conception of the INCA project

Abstract The goals and status of the INCA Project are presented. New technique based on the ionization-neutron calorimeter (INCA) and designed to study the energy spectrum and composition of the primary cosmic radiation in the “knee” region as well as the spectrum of primary electrons in the range 0.1–10 TeV is discussed.

PCR nuclear composition at 1–30 PeV according to lateral distributions of electrons in EAS accompanied by high energy particles in emulsion chambers

New data on the primary cosmic ray nuclear composition were derived from the electron lateral distributions of EAS at Tien-Shan. The dependence on EAS electron size is presented from Ne = 5·105 to 3·107. Data were obtained for all EAS as well as for EAS accompanied by high energy gamma-rays and hadrons in X-ray emulsion chambers. According to model simulations the latter events are generated predominantly by primary protons. Results showed that the fraction of protons and light nuclei does not decrease above the “knee” from Ne = 106 up to 107 (∼10 – 20 PeV primary energy).

The INCA project: present status and outlook

Abstract Scientific objectives, foundations, status, and outlook of the INCA Project are presented. Fundamentally new technique based on the ionization-neutron calorimeter (INCA) and designed to study local nearby sources of high-energy cosmic rays by direct measuring the spectrum and composition of the nuclear component in the “knee” region and the spectrum of primary electrons in the energy range 0.1–10 TeV with the proton-background suppression factor up to 107 is discussed. Experimental data on exposition of the INCA prototypes to electron, pion, and proton beams at various energies and corresponding simulation results are presented. Prospects are considered.

On absorption of the hadron component of EAS cores in a large lead calorimeter at 'knee'-range energies

The absorption of the core particles of extensive air showers (EAS) in the large 36 m2 lead ionization calorimeter (at the Tien-Shan mountain station) is analyzed in comparison with full Monte Carlo simulations. The EAS development in the atmosphere is simulated in the framework of CORSIKA+QGSJET code whereas the passage of hadrons and muons through the calorimeter has been simulated using the FLUKA transport code. It is shown that in EAS with energies of a few PeV the value of absorption length, Λ, of core hadron energy increases with energy much faster than that expected from simulations. This effect may be connected with the appearance of a small (a few per cent) excess of abnormal EAS cores with large ionization deposited in the lower layers of the calorimeter. It is shown that the shape of ionization curves in the lead calorimeter observed in abnormal EAS resembles that of high-energy muon groups. This effect cannot be explained by the increase of heavy nuclei in the PCR in the knee region. The hypothesis of prompt muons originated in the interaction of particles with atomic nuclei in the atmosphere also cannot explain the excess of abnormal absorption even at large values of charmed particle production cross sections.

Thunderstorm model of the temporal EAS disc structure

It is sliowu that non-relativistic neutrons evaporated by the air nuclei after the propagation of the main shower front produce a signal in neutron sensitive detectors, which can be delayed by milliseconds with respect to the signal from shower electrons and muons. Such temporal structure is analogous to that observed in another atmospheric phenomenon - the thunderstorm, when due to the different velocity of light and sound the thunder appears with a significant delay after the lightning.