Purposeful investigation of radiation fluxes strongly delayed in relation to the main particles front of extensive air shower (EAS) was undertaken at the Tien Shan Mountain Cosmic Ray Station. It was found that the passage of the EAS can be accompanied by the delayed thermal neutrons and by the soft $(30-50)$ keV gamma rays, mostly concentrated within a region of about $(5-10)$ m around shower axis, where the integral radiation fluence can vary in the limits of $(10^{-4}-1)$ cm$^{-2}$ for neutrons, and of $(0.1-1000)$ cm$^{-2}$ for gamma rays. The dependence of signal multiplicity on the shower size $N_e$ has a power shape both for the neutron and gamma ray components, with a sharp increase of its power index around the value of $N_e\approx 10^6$, which corresponds to the position of the $3\cdot10^{15}$ eV knee in the primary cosmic ray spectrum. Total duration of detectable radiation signal after the EAS passage can be of some tens of milliseconds in the case of neutron component, and up to a few whole seconds for gamma rays. The delayed accompaniment of low-energy radiation particles can be an effective probe to study the interaction of the hadronic component of EAS.

The events of multiple neutron production under a 2000 g/cm2 thick rock absorber were studied at the Tien Shan mountain cosmic ray station, at an altitude of 3340 m above the sea level. From comparison of the experimental and Geant4 simulated neutron multiplicity spectra it follows that the great bulk of these events can be explained by interaction of cosmic ray muons with internal material of neutron detector. In synchronous operation of the underground neutron monitor with the Tien Shan shower detector system it was found that the characteristics of the muonic component of extensive air showers which is seemingly responsible for generation of neutron events underground do change noticeably within the energy range of the knee of primary cosmic ray spectrum. Some peculiar shower events were detected when the neutron signal reveals itself only ∼100–1000 µs after the passage of the front of shower particles which probably means an existence of corresponding delay of the muon flux in such events.

The events of multiple neutron production under 2000g/cm^2 thick rock absorber were studied at the Tien Shan mountain cosmic ray station, at the altitude of 3340m above the sea level. From comparison of the experimental and Geant4 simulated neutron multiplicity spectra it follows that the great bulk of these events can be explained by interaction of cosmic ray muons with internal material of the neutron detector. In synchronous operation of the underground neutron monitor with the Tien Shan shower detector system it was found that the characteristics of the muonic component of extensive air showers which is seemingly responsible for generation of the neutron events underground do change noticeably within the energy range of the knee of primary cosmic ray spectrum. Some peculiar shower events were detected when the neutron signal reveals itself only ∼(100–1000) μs after the passage of the shower particles front which probably means an existence of corresponding delay of the muon flux in such events.

We present the outlines of a new microcontroller based data acquisition system which is aimed for reliable operation in a typical cosmic ray particle registration experiment. The system supports connection of up to 16 input signals and ensures the following operation functionality: (1) stable monitoring of the intensity of a digital pulse signal, or digitization of a continuous potential level with a low time resolution (typically, about 1 s–100 s); (2) registration of uninterruptable high-resolution (up to 5–10 μs) time series of the input signal intensity; (3) synchronization of registered time series with both external (physical) or local (program-based) trigger signal; (4) possibility of an on-the-fly change of the whole configuration of informational system (both the combination and type of input signals, time resolution and sum duration of the time series measurements, trigger logic, etc.) immediately in operation time through convenient communication by plain text messages in dialog mode. In particular, the considered system is applied now for a long-term, high precision measurement of the counting rate of neutron signals at the NM64 type neutron supermonitor of the Tien Shan mountain cosmic ray station, with a real-time representation of the whole collected dataset in a WWW database.

К 80-летию со дня рождения академика Б.Б. Кадомцева. Научная сессия Отделения физических наук Российской академии наук, 10 декабря 2008 г., Смирнов В.П., Мирнов С.В., Коврижных Л.М., Гуревич А.В., Караштин А.Н., Рябов В.А., Чубенко А.П., Щепетов А.Л., Ильгисонис В.И.

The FLUKA code is used to check the method (proposed earlier for the INCA project) of detection of MeV-range neutrons originated in nuclear and pure electromagnetic cascades in multilayer image lead-scintillator calorimeter (with an admixture of cadmium or gadolinium) without neutron counters by delayed ionization. MeV-range neutrons lose their energy during several microseconds in collisions with light nuclei, diffuse, and become captured by Cd or Gd nuclei with subsequent emission of gamma-rays which, in their turn, are converted into electrons. Amplitudes, time windows, a lateral spreading of delayed ionization produced by these electrons in scintillator layers are calculated. It is shown that neutron signal measured by this way can be highly efficient for the separation of electron-initiated cascades from the proton-initiated ones up to energies of several TeV. This method is planned to be used in the new space projects HERO (High Energy cosmic Ray Observatory) and INCA (Ionization-Neutron Calorimeter) aimed at investigation of different species of high-energy cosmic radiation (protons, nuclei, electrons, diffuse gammaray emission) with a high accuracy.