3,545 research outputs found
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.
Total spectrum of photon emission by an ultra-relativistic positron channeling in a periodically bent crystal
We present the results of numerical calculations of the channelling and
undulator radiation generated by an ultra-relativistic positron channelling
along a crystal plane, which is periodically bent. The bending might be due
either to the propagation of a transverse acoustic wave through the crystal, or
due to the static strain as it occurs in superlattices. The periodically bent
crystal serves as an undulator. We investigate the dependence of the
intensities of both the ordinary channelling and the undulator radiations on
the parameters of the periodically bent channel with simultaneous account for
the dechannelling effect of the positrons. We demonstrate that there is a range
of parameters in which the undulator radiation dominates over the channelling
one and the characteristic frequencies of both types of radiation are well
separated. This result is important, because the undulator radiation can be
used to create a tunable source of X-ray and gamma-radiation.Comment: published in J. Phys. G: Nucl. Part. Phys. 26 (2000) L87-L95,
http://www.iop.org ; 12 pages, 4 figures, LaTe
Channeling of Positrons through Periodically Bent Crystals: on Feasibility of Crystalline Undulator and Gamma-Laser
The electromagnetic radiation generated by ultra-relativistic positrons
channelling in a crystalline undulator is discussed. The crystalline undulator
is a crystal whose planes are bent periodically with the amplitude much larger
than the interplanar spacing. Various conditions and criteria to be fulfilled
for the crystalline undulator operation are established. Different methods of
the crystal bending are described. We present the results of numeric
calculations of spectral distributions of the spontaneous radiation emitted in
the crystalline undulator and discuss the possibility to create the stimulated
emission in such a system in analogy with the free electron laser. A careful
literature survey covering the formulation of all essential ideas in this field
is given. Our investigation shows that the proposed mechanism provides an
efficient source for high energy photons, which is worth to study
experimentally.Comment: 52 pages, MikTeX, 14 figure
The influence of the dechanneling process on the photon emission by an ultra-relativistc positron channeling in a periodically bent crystal
We investigate, both analytically and numerically, the influence of the
dechanneling process on the parameters of undulator radiation generated by
ultra-relativistic positron channelling along a crystal plane, which is
periodically bent. The bending might be due either to the propagation of a
transverse acoustic wave through the crystal, or due to the static strain as it
occurs in superlattices. In either case the periodically bent crystal serves as
an undulator which allows to generate X-ray and gamma-radiation.
We propose the scheme for accurate quantitative treatment of the radiation in
presence of the dechanneling. The scheme includes (i) the analytic expression
for spectral-angular distribution which contains, as a parameter, the
dechanneling length, (ii) the simulation procedure of the dechanneling process
of a positron in periodically bent crystals. Using these we calculate the
dechanneling lengths of 5 GeV positrons channeling in Si, Ge and W crystals,
and the spectral-angular and spectral distributions of the undulator over broad
ranges of the photons. The calculations are performed for various parameters of
the channel bending.Comment: published in J. Phys. G: Nucl. Part. Phys. 27 (2001) 95-125,
http://www.iop.or
Photon emission by an ultra-relativistic particle channeling in a periodically bent crystal
This paper is devoted to a detailed analysis of the new type of the undulator
radiation generated by an ultra-relativistic charged particle channeling along
a crystal plane, which is periodically bent by a transverse acoustic wave, as
well as to the conditions limiting the observation of this phenomenon. This
mechanism makes feasible the generation of electromagnetic radiation, both
spontaneous and stimulated, emitted in a wide range of the photon energies,
from X- up to gamma-rays
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