4,034 research outputs found
Influence of incoherent scattering on stochastic deflection of high-energy negative particle beams in bent crystals
An investigation on stochastic deflection of high-energy negatively charged
particles in a bent crystal was carried out. On the basis of analytical
calculation and numerical simulation it was shown that it exists a maximum
angle at which most of the beam is deflected. The existence of a maximum, which
is taken in the correspondence of the optimal radius of curvature, is a novelty
with respect to the case of positively charged particles, for which the
deflection angle can be freely increased by increasing the crystal length. This
difference has to be ascribed to the stronger contribution of incoherent
scattering affecting the dynamics of negative particles that move closer to
atomic nuclei and electrons. We therefore identified the ideal parameters for
the exploitation of axial confinement for negatively charged particle beam
manipulation in future high-energy accelerators, e.g., ILC or muon colliders
Planar channeling and quasichanneling oscillations in a bent crystal
Particles passing through a crystal under planar channeling experience
transverse oscillations in their motion. As channeled particles approach the
atomic planes of a crystal, they are likely to be dechanneled. This effect was
used in ion-beam analysis with MeV energy. We studied this effect in a bent
crystal for positive and negative particles within a wide range of energies in
sight of application of such crystals at accelerators. We found the conditions
for the appearance or not of channeling oscillations. Indeed a new kind of
oscillations, strictly related to the motion of over-barrier particles, i.e.
quasichanneling particles, has been predicted. Such oscillations, named planar
quasichanneling oscillations, possess a different nature than channeling
oscillations. Through computer simulation, we studied this effect and provided
a theoretical interpretation for them. We show that channeling oscillations can
be observed only for positive particles while quasichanneling oscillations can
exist for particles with either sign. The conditions for experimental
observation of channeling and quasichanneling oscillations at existing
accelerators with available crystal has been found and optimized.Comment: 25 pages, 11 figure
A model for the interaction of high-energy particles in straight and bent crystals implemented in Geant4
A model for the simulation of orientational effects in straight and bent
periodic atomic structures is presented. The continuum potential approximation
has been adopted.The model allows the manipulation of particle trajectories by
means of straight and bent crystals and the scaling of the cross sections of
hadronic and electromagnetic processes for channeled particles. Based on such a
model, an extension of the Geant4 toolkit has been developed. The code has been
validated against data from channeling experiments carried out at CERN
Low-latency analysis pipeline for compact binary coalescences in the advanced gravitational wave detector era
The multi-band template analysis (MBTA) pipeline is a low-latency coincident
analysis pipeline for the detection of gravitational waves (GWs) from compact
binary coalescences. MBTA runs with a low computational cost, and can identify
candidate GW events online with a sub-minute latency. The low computational
running cost of MBTA also makes it useful for data quality studies. Events
detected by MBTA online can be used to alert astronomical partners for
electromagnetic follow-up. We outline the current status of MBTA and give
details of recent pipeline upgrades and validation tests that were performed in
preparation for the first advanced detector observing period. The MBTA pipeline
is ready for the outset of the advanced detector era and the exciting prospects
it will bring.Comment: 18 pages, 10 figure
Progress in crystal extraction and collimation
Recent IHEP Protvino experiments show efficiencies of crystal-assisted slow
extraction and collimation of 85.3+-2.8%, at the intensities of the channeled
beam on the order of 10^12 proton per spill of 2 s duration. The obtained
experimental data well follows the theory predictions. We compare the
measurements against theory and outline the theoretical potential for further
improvement in the efficiency of the technique. This success is important for
the efficient use of IHEP accelerator and for implementation of
crystal-assisted collimation at RHIC and slow extraction from AGS onto E952,
now in preparation. Future applications, spanning in the energy from order of 1
GeV (scraping in SNS, slow extraction from COSY and medical accelerators) to
order of 1 TeV and beyond (scraping in Tevatron, LHC, VLHC), can benefit from
these studies.Comment: 7pp. Presented at HEACC 2001 (Tsukuba, March 25-30
Crystal experiments on efficient beam extraction
Silicon crystal was channeling and extracting 70-GeV protons from the U-70
accelerator with efficiency of 85.3+-2.8% as measured for a beam of 10^12
protons directed towards crystals of 2 mm length in spills of 1-2 s duration.
The experimental data follow very well the prediction of Monte Carlo
simulations. This success is important to devise a more efficient use of the
U-70 accelerator in Protvino and provides a crucial support for implementation
of crystal-assisted collimation of gold ion beam in RHIC and slow extraction
from AGS onto E952, now in preparation at Brookhaven Nat'l Lab. Future
applications, spanning in the energy from sub-GeV (medical) to order of 1 GeV
(scraping in the SNS, extraction from COSY) to order of 1 TeV and beyond
(scraping in the Tevatron, LHC, VLHC), can benefit from these studies.Comment: 12pp. Presented at 19-th Intern. Conference on Atomic Collisions in
Solids (ICACS-19: Paris, July 29 - August 3, 2001
Channeling of high energy beams in nanotubes
We present simulations of particle beam channeling in carbon nanotubes and evaluate the possibilities for experimental observation of channeling effect in straight and bent nanotubes at IHEP and LNF. Different particle species are considered: protons of 1.3 and 70 GeV, and positrons of 0.5 GeV. Predictions are made for the experiments, with analysis of requirements on the quality of nanosamples and resolution of the experimental set-up. Based on Monte Carlo simulations, the capabilities of nanotube channeling technique for particle beam steering are discussed
Experimental evidence of planar channeling in a periodically bent crystal
The usage of a Crystalline Undulator (CU) has been identified as a promising
solution for generating powerful and monochromatic -rays. A CU was
fabricated at SSL through the grooving method, i.e., by the manufacturing of a
series of periodical grooves on the major surfaces of a crystal. The CU was
extensively characterized both morphologically via optical interferometry at
SSL and structurally via X-ray diffraction at ESRF. Then, it was finally tested
for channeling with a 400 GeV/c proton beam at CERN. The experimental results
were compared to Monte Carlo simulations. Evidence of planar channeling in the
CU was firmly observed. Finally, the emission spectrum of the positron beam
interacting with the CU was simulated for possible usage in currently existing
facilities
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