453 research outputs found
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 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 fragmentation via preferential C 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 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--C 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
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
Radiation Emission by Electrons Channeling in Bent Silicon Crystals
Results of numerical simulations of electron channeling and emission spectra
are reported for straight and uniformly bent silicon crystal. The projectile
trajectories are computed using the newly developed module [1] of the MBN
Explorer package [2,3]. The electron channeling along Si(110) crystallographic
planes is studied for the projectile energy 855 MeV.Comment: 9 pages, 7 figures; submitted to European Physical Journal D. arXiv
admin note: text overlap with arXiv:1307.678
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 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
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