The article presents a description of the ISNP/GNEIS testing facility with a neutron spectrum that reproduces the spectrum of atmospheric neutron radiation. The facility was developed at the Petersburg Nuclear Physics Institute (PNPI) of the National Research Center Kurchatov Institute in collaboration with the Institute of Space Device Engineering, a branch of JSC (Joint Stock Company) United Rocket and Space Corporation. The spallation neutron source of the facility is based on the 1-GeV SC-1000 proton synchrocyclotron at the PNPI. The internal neutron-production lead target produces 10-ns pulses of neutrons with a repetition rate of 45–50 Hz and an average neutron intensity of 3 × 1014 n/s (in the 4σ solid angle). In the irradiation area located at a distance of 36 m from the neutron source, a high-quality collimated neutron beam with a broad energy spectrum of 1–1000 MeV and a neutron flux of 4 × 105 n/(cm2 s) allows conducting accelerated single-event soft error testing of electronic components. In the course of the irradiation, the neutron energy spectrum and intensity and the spatial profile of the beam are controlled using a fission ionization chamber (beam monitor) and a position-sensitive multiwire proportional counter (beam profile meter). The data acquisition system of the ISNP/GNEIS facility utilizes 250 MS/s 12 bit CAEN waveform digitizers for the processing of signals from the monitor and profile meter by the neutron time-of-flight technique. In the report, parameters of the ISNP/GNEIS testing facility are discussed in comparison with analogous world-class facilities, as well as requirements and recommendations of the standards used in this field.

Using the Geant4 software package, a numerical simulation of a neutron source of the time-offlight spectrometer GNEIS created on the basis of the SC-1000 synchrocyclotron with 1 GeV proton energy at the NRC Kurchatov Institute—PNPI (Gatchina) has been carried out. The influence of the structural features of the neutron source of the spectrometer on the spatial and energy distributions of neutrons has been studied. The intensity and spectral characteristics of the neutron flux in the range of 1–1000 MeV have been determined on the basis of the obtained information and detailed allowance for all elements of the neutron beam guide system. It is found that the best agreement between the experiment and calculation performed by means of Geant4 is observed when using the QGSP_INCLXX_HP model. In the neutron energy range of 1–200 MeV, the difference between the experimental and calculated shapes of the spectra is less than 25%.

The properties of the avalanche processes that develop on a dynamical lattice, the structure of links in which changes due to a specific characteristic of each lattice node, namely, its “activity,” which determines the probability of connection of a certain node with neighboring nodes in one step of lattice evolution. The statistics of the sizes of the avalanches appearing in the lattice system is studied as a function of the node activity and the link lifetime (the lifetime of the links formed in the system). It is analytically and numerically shows that the type of avalanche dynamics in the system changes as a function of these parameters. The following three regimes can take place in the system: (1) avalanches of any sizes, from small to catastrophic, can appear, which is reflected in the power-law behavior of the probability density function of the appearance of avalanches of certain sizes; (2) avalanches of a certain average size mainly appear in the system, and the probability density is close to that of a normal distribution; and (3) transient regime, where the probability density function of the appearance of avalanches of certain sizes is close to an exponential function. These results open up the possibilities of controlling the behavior of a complex system; in particular, they can be used to prevent catastrophic avalanches by changing the link lifetime and the average node activity.

The model of a superconducting metamaterial, which is a disordered lattice of Josephson junctions, has been studied theoretically and by computer simulation. The aim of this work is to reveal and analyze the conditions under which the generation frequencies of constituting junctions are locked in the system under study placed in a spatially nonuniform magnetic field. The main result is the demonstration of the possibility of locking of the generation frequencies of junctions in individual layers of the system under study. This result is particularly important in view of the possibility of the use of superconducting metamaterials for the creation of devices, in particular, generators capable of working in the terahertz frequency range.

The theory of the bulk-SQUID effect in discrete superconductors is constructed for the first time. It is shown that the bulk-SQUID effect emerges in the system of 2D intrinsically stochastic multijunction SQUID (i.e., with random values of critical currents of the junctions, injection currents, and the coupling coefficients between the junction) due to generation frequency locking in all junctions. It is demonstrated that the bulk-SQUID effect occurs in a wide range of random parameters of the system. This domain of variation of the system parameters can be divided into three subdomains. The first one is the subdomain of coherent dynamics of phases at the junctions, the second is the subdomain of incoherent dynamics, in which the phases of the junctions are not locked, but the bulk-SQUID effect persists, and the third is the subdomain of transient dynamics, in which coherent dynamics and the bulk-SQUID effect are observed in parts. A simple mathematical model of noninteracting junctions, which correctly describes basic features of the dynamics of the initial system and makes it possible to calculate some of its statistical characteristics, is proposed and analyzed.

The effect of the structure of a complex network on the properties of an avalanche dynamical process on it has been studied. It has been found that such a structural characteristic of the network as the degree of its assortativity (disassortativity), which is numerically expressed by the assortativity coefficient r, is a control parameter determining the properties of the dynamical process on the network.

The effect of the structure of a complex network on the properties of avalanche dynamical process on it has been analyzed for the first time. It has been shown that the assortativity (disassortativity) degree, which is a structure characteristic of the network and is numerically characterized by the assortativity coefficient r , is a control parameter governing the properties of the dynamical process on the network. The structure of individual avalanches on networks with various r values has been studied. It has been shown that the number of nodes involved in an avalanche is a periodic function of the time.

The dynamics of the phases in a discrete superconductor model has been studied both theoretically and in computer simulation for the case of the passage of a direct current higher than the total critical current of junctions. It has been shown that a bulk-SQUID phenomenon appears in the system in this case and the system is nonergodic. This means that the dynamics of the system certainly depends on the initial conditions and dynamical attractors are limit cycles each having an attracting domain in the configuration space of initial conditions. A mathematical technique for recovering ergodicity in the system under investigation has been proposed. It has also been demonstrated that the bulk-SQUID phenomenon is not observed when the ergodicity is recovered in the system. It has been shown that the results are quite general and describe the behavior of a class of dynamical systems.

The critical state of a 1D multijunction SQUID with intrinsic spatial randomness has been studied. It is shown that the system behavior is independent of the SQUID parameter and the critical state under consideration is self-organized.

The critical dynamics of a two-threshold system with the law of conservation of the basic quantity z and in the absence of sink on a scale-free network has been studied. It has been shown that the critical state that is a set of metastable states appears in such a system. The structure of the metastable states is a set of stable clusters of nodes at which the z values are close to the positive and negative threshold values. Avalanches transforming the system from one metastable state to another state appear in the system. The absence of sink is effectively replaced by the annihilation process. The statistics of avalanches in such a system has been analyzed. It has been shown that the self-organized critical state can appear in the system.

The critical state of a two-dimensional discrete superconductor in an external magnetic field is studied. This state is found to be self-organized in the generalized sense, i.e., is a set of metastable states that transform to each other by means of avalanches. An avalanche is characterized by the penetration of a magnetic flux to the system. The sizes of the occurring avalanches, i.e., changes in the magnetic flux, exhibit the power-law distribution. It is also shown that the size of the avalanche occurring in the critical state and the external magnetic field causing its change are statistically independent quantities.

Properties of small clusters with icosahedric symmetry, isolated or embedded in an fcc matrix, were investigated for different metals by the molecular-dynamics method. It is shown that the energy specific features of clusters and the height of the barrier for the transition from an fcc to icosahedric structure for isolated clusters are determined to a great extent by the properties of the interatomic-interaction potentials. In this case, the lower the transition barrier, the "softer" the potential is. Vice versa, the clusters embedded in a matrix are most stable in metals with a rigid potential. It is established that the stability of an embedded cluster increases the number of vacancies at the boundary between two structures and depends on the orientation of the cluster with respect to the matrix. An embedded cluster introduces significant perturbations into the surrounding matrix, which extend to distances of about one and a half cluster sizes.

We give a theoretical description of avalanche-like dynamics of magnetic flux in the critical state of "hard" type-II superconductors using a model of a one-dimensional multijunction SQUID that well reproduces the main magnetic properties of these objects. We show that the system under consideration demonstrates the self-organized criticality. The avalanches of vortices manifest themselves as jumps of the total magnetic flux in the sample. The sizes of these jumps have a power-law distribution. Our results are in qualitative agreement with experiments.

By both the structural-analysis and computer-simulation methods, the radiation-induced states appeared in metallic materials within the certain range of radiation parameters under the high levels of radiation damage are investigated. As shown, the nanocluster structures are formed within the range of presence of such states; the X-ray pattern is changed; the material properties related to both ionic and electronic subsystems of a metal are also changed. The comparison of structural experiments and computer-modelling results allows us to suppose that the reinforcing clusters of icosahedral symmetry are formed in a vicinity of radiation defects within the matrix due to the local deformation of its crystal lattice, and that leads to the changes of the material properties observed.

A nonequilibrium state has been discovered which is induced by ion irradiation in metallic materials (solid solutions of Fe–Ni, Fe–Cr–Ni, Ni–Cr, Cu–Ni, Fe–Cr, and V–Ti–Cr systems and in pure metals Zr and Ti) at high levels of radiation damage, and the features of this state are considered. In the region of existence of this state, both the ion and the electron subsystems of the metal show highly anomalous properties. Moreover, the occurrence of this state is accompanied by substantial diffraction effects – X-ray line splitting – and, as indicated by electron microscopy, by the formation of a cluster structure. Simulation by the methods of molecular dynamics suggests that the clusters observed are atomic groups of icosahedral (quintuple) symmetry formed in the neighborhood of radiation vacancies. These clusters reinforce the matrix, and this should result in substantial changes in strength and electronic properties of the material. The results of the computer simulation agree with the observed diffraction effects.