88,500 research outputs found
Negative Particle Planar and Axial Channeling and Channeling Collimation
While information exists on high energy negative particle channeling there
has been little study of the challenges of negative particle bending and
channeling collimation. Partly this is because negative dechanneling lengths
are relatively much shorter. Electrons are not particularly useful for
investigating negative particle channeling effects because their material
interactions are dominated by channeling radiation. Another important factor is
that the current central challenge in channeling collimation is the
proton-proton Large Hadron Collider (LHC) where both beams are positive. On the
other hand in the future the collimation question might reemerge for
electron-positron or muon colliders. Dechanneling lengths increase at higher
energies so that part of the negative particle experimental challenge
diminishes. In the article different approaches to determining negative
dechanneling lengths are reviewed. The more complicated case for axial
channeling is also discussed. Muon channeling as a tool to investigate
dechanneling is also discussed. While it is now possible to study muon
channeling it will probably not illuminate the study of negative dechanneling.Comment: 15 pages, 1 figure, docx fil
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
Coherent radiation of atoms and a channeling particle
New mechanism of radiation emitted at channeling of a relativistic particle
in a crystal is studied. Superposition of coherent radiation of the atoms in a
crystal lattice which are excited by a channeling particle and radiation of the
channeling particle itself is considered. It is shown that coherent radiation
of the chain of oscillating atoms forms a resonance peak on the background of
radiation of the channeling particle.Comment: 7 pages, 4 figure
Channeling of protons through carbon nanotubes
This book contains a thorough theoretical consideration of the process of
proton channeling through carbon nanotubes. We begin with a very brief summary
of the theoretical and experimental results of studying ion channeling through
nanotubes. Then, the process of ion channeling is described briefly. After
that, the crystal rainbow effect is introduced. We describe how it was
discovered, and present the theory of crystal rainbows, as the proper theory of
ion channeling in crystals and nanotubes. We continue with a description of the
effect of zero-degree focusing of protons channeled through nanotubes. It is
shown that the evolution of the angular distribution of channeled protons with
the nanotube length can be divided in the cycles defined by the rainbow effect.
Further, we analyze the angular distributions and rainbows in proton channeling
through nanotubes. This is done using the theory of crystal rainbows. The
angular distributions are generated by the computer simulation method, and the
corresponding rainbow patterns are obtained in a precise analysis of the
mapping of the impact parameter plane to the transmission angle plane. We
demonstrate that the rainbows enable the full explanation of the angular
distributions. We also investigate how the effect of dynamic polarization of
the carbon atoms valence electrons influences the angular and spatial
distributions of protons transmitted through short nanotubes in vacuum and
embedded in dielectric media. In addition, we explore the channeling star
effect in 1 GeV proton channeling through bundles of nanotubes, which appears
when the proton beam divergence angle is larger than the critical angle for
channeling.Comment: 58 pages, 22 figures, the book "Channeling of Protons through Carbon
Nanotubes" (published by Nova Science Publishers 2011
Studies of Nanotube Channeling for Efficient Beam Scraping at Accelerators
While particle beam steering (and in particular, "scraping") in accelerators
by bent channeling crystals is an established technique extensively tested at
IHEP Protvino and other major high-energy labs, an interesting question is how
one could improve channeling capabilities by applying modern nanotechnology.
Theoretical research of nanotube channeling was in progress over recent years.
In this work, we assess potential benefits from nanotube channeling for real
accelerator systems. We report simulation studies of channeling in
nanostructured material (carbon SWNT and MWNT) tested for possible serving as a
primary scraper for the collimation systems of hadron colliders. The advantages
of nanostructured material as a potential choice for a primary scraper in a
high-energy accelerator such as LHC or the Tevatron are discussed in comparison
to crystal lattices and amorphous material. We evaluate physical processes
relevant to this application and reveal nanotechnology requirements.Comment: Presented at the Int. Conf. on Atomic Collisions with Solids
(ICACS-21, Genova 4-9 July 2004
Channeling of high-energy particles in a multi-wall nanotube
Channeling of high-energy particles in straight and bent multi-wall nanotubes
(MWNT) has been studied in computer simulations and compared to the channeling
properties of single-wall nanotubes (SWNT) and bent crystal lattices. It is
demonstrated that MWNT can efficiently channel positively-charged high-energy
particles trapped between the walls of MWNT. Bending dechanneling in MWNT has
been computed as a function of the particle momentum to nanotube curvature
radius ratio, . It is found that a bent MWNT can steer a particle beam
with bending capabilities similar to those of bent silicon crystal lattice and
to those of best (i.e. the narrowest) SWNT. In view of channeling applications
at particle accelerators, MWNT appear favored as compared to SWNT, because MWNT
can be produced quite straight (and in aligned array), while SWNT is typically
very curved, thus posing a severe problem for channeling applications.
Therefore, we suggest that MWNT provide a better candidate for channeling than
SWNT.Comment: 16 pages, 6 figures, to appear in Phys. Lett.
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