3,048 research outputs found
Electron-based crystalline undulator
We discuss the features of a crystalline undulator of the novel type based on
the effect of a planar channeling of ultra-relativistic electrons in a
periodically bent crystals. It is demonstrated that an electron-based undulator
is feasible in the tens of GeV range of the beam energies, which is noticeably
higher than the energy interval allowed in a positron-based undulator.
Numerical analysis of the main parameters of the undulator as well as the
characteristics of the emitted undulator radiation is carried out for 20 and 50
GeV electrons channeling in diamond and silicon crystals along the (111)
crystallographic planes.Comment: 16 pages, 8 figures, Latex, IOP styl
Coherent radiation of an ultra-relativistic charged particle channeled in a periodically bent crystal
We suggest a new type of the undulator radiation which is generated by an
ultra-relativistic particle channeled along a periodically bent
crystallographic plane or axis. The electromagnetic radiation arises mainly due
to the bending of the particle's trajectory, which follows the shape of the
channel. The parameters of this undulator, which totally define the spectrum
and the angular distribution of the radiation (both spontaneous and
stimulated), depend on the type of the crystal and the crystallographic plane
(axis), on the type of a projectile and its energy, and on the shape of the
bent channel, and, thus, can be varied significantly by varying these
characteristics.
As an example, we consider the acoustically induced radiation (AIR) which is
generated by ultra-relativistic particles channeled in a crystal which is bent
by a transverse acoustic wave. The AIR mechanism allows to make the undulator
with the main parameters varying in wide ranges, which are inaccessible in the
undulators based on the motion of particles in the periodic magnetic fields and
also in the field of the laser radiation. The intensity of AIR can be easily
made larger than the intensity of the radiation in a linear crystal and can be
varied in a wide range by varying the frequency and the amplitude of the
acoustic wave in the crystal. A possibility to generate stimulated emission of
high-energy photons (in keV - MeV region) is also discussed.Comment: published in J. Phys. G: Nucl. Part. Phys. 24 (1998) L45-L53,
http://www.iop.or
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
Stable propagation of a modulated positron beam in a bent crystal channel
The propagation of a modulated positron beam in a planar crystal channel is
investigated. It is demonstrated that the beam preserves its modulation at
sufficiently large penetration depths which opens the prospect of using a
crystalline undulator as a coherent source of hard x-rays. This finding is a
crucial milestone in developing a new type of lasers radiating in the hard
x-ray and gamma-ray range.Comment: 11 pages, 4 figures, iopar
One-dimensional Model of a Gamma Klystron
A new scheme for amplification of coherent gamma rays is proposed. The key
elements are crystalline undulators - single crystals with periodically bent
crystallographic planes exposed to a high energy beam of charged particles
undergoing channeling inside the crystals. The scheme consists of two such
crystals separated by a vacuum gap. The beam passes the crystals successively.
The particles perform undulator motion inside the crystals following the
periodic shape of the crystallographic planes. Gamma rays passing the crystals
parallel to the beam get amplified due to interaction with the particles inside
the crystals. The term `gamma klystron' is proposed for the scheme because its
operational principles are similar to those of the optical klystron. A more
simple one-crystal scheme is considered as well for the sake of comparison. It
is shown that the gamma ray amplification in the klystron scheme can be reached
at considerably lower particle densities than in the one-crystal scheme,
provided that the gap between the crystals is sufficiently large.Comment: RevTeX4, 22 pages, 4 figure
SPECIFIC INFLAMMATORY PROTEINS IN THE BLOOD AND URINE OF PATIENTS WITH RECURRENT PYELONEPHRITIS
The aim of our study was to investigate the content of specific inflammatory proteins (C-reactive protein, fibronectin, cystatin C) in the blood and urine ofpatients with pyelonephritis, depending on the frequency of recurrences.
Patients and methods. A cross-sectional study was carried out and included 64 female patients with uncomplicated pyelonephritis, over 18 years (mean 32.3 ± 9 years). We determined C-reactive protein (CRP), fibronectin (FN), and cystatin C CysC) in the blood and urine of patients using test kits «Dialab» (Austria) by immunoturbidimetric method. After the examination patients were divided into II groups: I (n = 34) – women with recurrent pyelonephritis and II (n = 30) – patients with sporadic pyelonephritis (up to 2 times per year).
Results. The patients of group I showed the highest level of blood concentrations of CysC (p = 0.02) and a decrease of FN (p = 0.01). We found an inverse correlation between the number of recurrences of pyelonephritis per year and the blood level of FN (r = -0.42, p = 0.007). In addition, we determined a strong direct correlation between the urinary FN and blood level of CysC (r = 0.6, p <0.0001).
Conclusions. Decrease of FN and growth of CysC in the blood ofpatients with recurrent pyelonephritis is the result offrequent inflammatory activity. Determination of specific inflammatory proteins in the blood and urine ofpatients with pyelonephritis can be used as alternative markers for diagnosis and monitoring of diseas
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