1,246 research outputs found
Polarization properties of DCR from relativistic channeled electrons
Based on the modification of the dynamic theory of DCR from axially channeled electrons, the formulas for the angular distributions of the directions of DCR linear polarization are obtained. The calculations of the angular distributions
of the directions of DCR linear polarization from planar (Ξ³ = 80) and axially (Ξ³ = 20) channeled electrons in Si and LiF crystals are performed. These calculations show significant differences in the polarization properties of DCR compared with those of PXR, which can be useful in future experiments on the observation of DCR
Angular distributions of Cherenkov radiation from relativistic heavy ions: Stopping and isotopic effects
We studied numerically the structure of angular distributions of Cherenkov radiation (ChR) from moderately relativistic heavy ions (RHI) taking into account the decrease of the ion velocity due to stopping in the radiator. The calculations clearly show that both the width and fine structure of the ChR angular distribution in the vicinity of the Cherenkov cone are remarkably different for isotopes with different masses, at equal initial relativistic factor (velocity) of isotopes. This stopping and isotopic effects in ChR can be observed using RICH detectors of RHI
Absorption in Ultra-Peripheral Nucleus-Atom Collisions in Crystal
The Glauber theory description of particle- and nucleus-crystal Coulomb
interactions at high-energy is developed. The allowance for the lattice thermal
vibrations is shown to produce strong absorption effect which is of prime
importance for quantitative understanding of the coherent Coulomb excitation of
ultra-relativistic particles and nuclei passing through the crystal.Comment: 8 pages, LaTe
Photonuclear reactions by relativistic electron channeling radiation
The research for newly developing branch of nuclear physics, the nuclear photonics, has been accompanied sinc
Channeling of Relativistic Electrons in Half-Wave Silicon Crystal and Corresponding Radiation
The new experiments on channeling of 255 MeV in a 0.7 ?m silicon half-wavelength crystal were performed at SAGA LS facility. Both experimental and simulated electron angular distribution after the crystal and corresponding radiation spectra reveal the number of peculiarities
Planar channelling of relativistic electrons in half-wave silicon crystal and corresponding radiation
New experimental data on planar channeling of 255 MeV electrons in a 0.74 Β΅m Si Half-Wave Crystal (HWC) obtained at SAGA-LS facility are presented. The computer simulation showed that the angular distribution of electrons after penetration through the HWC revealed the number of unknown before peculiarities is connected with specific electron trajectories in HWC. These specific trajectories lead to specific radiation, the properties of which are analyzed
Bulk Nanocrystalline Thermoelectrics Based on Bi-Sb-Te Solid Solution
A nanopowder from p-Bi-Sb-Te with particles ~ 10 nm were fabricated by the
ball milling using different technological modes. Cold and hot pressing at
different conditions and also SPS process were used for consolidation of the
powder into a bulk nanostructure and nanocomposites. The main factors allowing
slowing-down of the growth of nanograins as a result of recrystallization are
the reduction of the temperature and of the duration of the pressing, the
increase of the pressure, as well as addition of small value additives (like
MoS2, thermally expanded graphite or fullerenes). It was reached the
thermoelectric figure of merit ZT=1.22 (at 360 K) in the bulk nanostructure
Bi0,4Sb1,6Te3 fabricated by SPS method. Some mechanisms of the improvement of
the thermoelectric efficiency in bulk nanocrystalline semiconductors based on
BixSb2-xTe3 are studied theoretically. The reduction of nanograin size can lead
to improvement of the thermoelectric figure of merit. The theoretical
dependence of the electric and heat conductivities and the thermoelectric power
as the function of nanograins size in BixSb2-xTe3 bulk nanostructure are quite
accurately correlates with the experimental data.Comment: 35 pages, 24 figures, 4 tables, 52 reference
Computer simulation of electron-positron pair production by channeling radiation in amorphous converter
We consider the radiator-converter approach at 200 MeV channeled electrons (the SPARC_LAB LNF facility energies) for the case of using W crystalline radiator and W amorphous converter. A comparison of the positron production by the axial channeling radiation and the bremsstrahlung is performed. The positron stopping in the convertor is studied by means of computer simulations. It is shown that for the maximum yield of positrons the thickness of the W amorphous converter should be taken 0.35 cm in the case of using the axial channeling radiation resulting to total yield of positrons 5 10-3 e+/e- and 0.71 cm in the case of using the bremsstrahlung resulting to total yield of positrons 3.3 10-3 e+/e-
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