Classical molecular dynamics simulations of fusion and fragmentation in fullerene-fullerene collisions

We present the results of classical molecular dynamics simulations of collision-induced fusion and fragmentation of C$_{60}$ fullerenes, performed by means of the MBN Explorer software package. The simulations provide information on structural differences of the fused compound depending on kinematics of the collision process. The analysis of fragmentation dynamics at different initial conditions shows that the size distributions of produced molecular fragments are peaked for dimers, which is in agreement with a well-established mechanism of C$_{60}$ fragmentation via preferential C$_2$ emission. Atomic trajectories of the colliding particles are analyzed and different fragmentation patterns are observed and discussed. On the basis of the performed simulations, characteristic time of C$_2$ emission is estimated as a function of collision energy. The results are compared with experimental time-of-flight distributions of molecular fragments and with earlier theoretical studies. Considering the widely explored case study of C$_{60}$--C$_{60}$ collisions, we demonstrate broad capabilities of the MBN Explorer software, which can be utilized for studying collisions of a broad variety of nanoscale and biomolecular systems by means of classical molecular dynamics

Dialogue Education vs Monologue Education: To the Problem of Overcoming Radicalism

The article deals with the peculiarities of monologue and dialogue education in their influence on the genesis of radicalism manifestation. Monologism in education is understood as the transfer of sociocultural knowledge without taking into account the learner. The disadvantage of such education is the lack of the ability to communicate and conduct a dialogue, the appearance of a reserved personality with monologue needs, that lead to radicalism. The loss of a critical assessment, binary thinking, certitude in one's own rightness, mean the “closing” of a human personality, the loss of one’s ability to look at oneself from the outside, the monologue of the main activities. The second type of education is dialogic, based on the dialogue, contact with other people, the ability to listen to and hear another person, the ability to be open to the Other person. It is a road to cognition, the development of such personal “navigation” skills as goal-setting, dialogue, reflexivity, creativity, cognition

Channeling and radiation of the 855 MeV electrons enhanced by the re-channeling in a periodically bent diamond crystal

Channeling properties and radiation spectra are studied on the grounds of numerical simulations for the 855 MeV electrons in a periodically bent diamond crystal. The bent crystalline profiles are shown to enhance the re-channeling of the projectiles and to produce distinct lines in the radiation spectra. The results obtained are analyzed and contrasted to the properties of the planar channeling and of the channeling in uniformly bent crystals.Comment: 8 pages, 5 figure

Channeling of electrons and positrons in straight and periodically bent diamond(110) crystals

In this paper we present the results of a systematic numerical analysis of the channeling properties of electrons and positrons in oriented straight and periodically bent diamond(110) crystals. We analyse dependence of the intensity of the radiation emitted on the projectile energy as well as on the bending amplitude. The analysis presented is based on the grounds of accurate numerical simulations of the channeling process. The simulation parameters, such as the crystal orientation, thickness and bending parameters of the crystals as well as the energy of the projectiles, were chosen to match those used in past and ongoing experiments. The peculiarities which appear in the radiation spectra are attributed to the interplay of various radiation mechanisms. The analysis performed can be used to predict and explain future experimental results.Comment: 14 pages, 8 figures, 1 tabl

Atomistic modelling and characterizaion of light sources based on small-amplitude short-period periodically bent crystals

The feasibility of gamma-ray light sources based on the channeling phenomenon of ultrarelativistic electrons and positrons in oriented crystals that are periodically bent with Small Amplitude and Short Period (SASP) is demonstrated by means of rigorous numerical modelling that accounts for the interaction of a projectile with all atoms of the crystalline environment. Numerical data on the spectral distribution, brilliance, number of photons and power of radiation emitted by 10 GeV electron and positron beams passing through diamond, silicon and germanium crystals are presented and analyzed. The case studies presented in the paper refer to the FACET-II beams available at the SLAC facility. It is shown that the SASP bending gives rise to the radiation enhancement in the GeV photon energy range where the peak brilliance of radiation can be as high as on the 10^{24} photons/s/mrad^2/mm^2/0.1BW. The parameters of radiation can be tuned by varying the amplitude and period of bending.Comment: 25 pages, 17 figure

Crystal-based intensive gamma-ray light sources

We discuss design and practical realization of novel gamma-ray Crystal-based Light Sources (CLS) that can be constructed through exposure of oriented crystals (linear, bent, periodically bent) to beams of ultrarelativistic charged particles. In an exemplary case study, we estimate brilliance of radiation emitted in a Crystalline Undulator (CU) LS by available positron beams. Intensity of CU radiation in the photon energy range $10^0-10^1$ MeV, which is inaccessible to conventional synchrotrons, undulators and XFELs, greatly exceeds that of laser-Compton scattering LSs and can be higher than predicted in the Gamma Factory proposal to CERN. Brilliance of CU-LSs can be boosted by up to 8 orders of magnitude through the process of superradiance by a pre-bunched beam. Construction of novel CLSs is a challenging task which constitutes a highly interdisciplinary field entangling a broad range of correlated activities. CLSs provide a low-cost alternative to conventional LSs and have enormous number of applications.Comment: 31 pages, 12 figures. In print in European Physical Journal D (2020

Simulation of Ultra-Relativistic Electrons and Positrons Channeling in Crystals with MBN Explorer

A newly developed code, implemented as a part of the \MBNExplorer package \cite{MBN_ExplorerPaper,MBN_ExplorerSite} to simulate trajectories of an ultra-relativistic projectile in a crystalline medium, is presented. The motion of a projectile is treated classically by integrating the relativistic equations of motion with account for the interaction between the projectile and crystal atoms. The probabilistic element is introduced by a random choice of transverse coordinates and velocities of the projectile at the crystal entrance as well as by accounting for the random positions of the atoms due to thermal vibrations. The simulated trajectories are used for numerical analysis of the emitted radiation. Initial approbation and verification of the code have been carried out by simulating the trajectories and calculating the radiation emitted by \E=6.7 GeV and \E=855 MeV electrons and positrons in oriented Si(110) crystal and in amorphous silicon. The calculated spectra are compared with the experimental data and with predictions of the Bethe-Heitler theory for the amorphous environment.Comment: 41 pages, 11 figures. Initially submitted on Dec 29, 2012 to Phys. Rev.