200 research outputs found
Simulation of CRYSTAL, the Bent Crystal Based Collimation Experiment in the SPS
Crystal collimation is a possible variant of the two-stage collimation systems used in modern accelerators, by which the collimation efficiency may be strongly enhanced. An experiment is proposed in the CERN-SPS to check the improved performance on crystal collimation. Here we present the experiment layout and we perform simulations showing in quantitative manner the expected behavior of crystal collimation in the SPS
Radiation of photons in process of charge particle volume reflection in bent single crystal
New type of radiation in crystals is predicted and investigated in computer
simulation. It is shown that process of volume reflection of electrons and
positrons in bent crystals is accomplished with high-power radiation of
photons. Volume reflection radiation has intensity comparable with known
channeling radiation, but it is less sensitive to entrance angle and sign of
charge of a particle. Simulated spectra of radiation power are presented for 10
GeV and 200GeV particles.Comment: Latex, 8 pages, 4 fig
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
The UA9 experimental layout
The UA9 experimental equipment was installed in the CERN-SPS in March '09
with the aim of investigating crystal assisted collimation in coasting mode.
Its basic layout comprises silicon bent crystals acting as primary
collimators mounted inside two vacuum vessels. A movable 60 cm long block of
tungsten located downstream at about 90 degrees phase advance intercepts the
deflected beam.
Scintillators, Gas Electron Multiplier chambers and other beam loss monitors
measure nuclear loss rates induced by the interaction of the beam halo in the
crystal. Roman pots are installed in the path of the deflected particles and
are equipped with a Medipix detector to reconstruct the transverse distribution
of the impinging beam. Finally UA9 takes advantage of an LHC-collimator
prototype installed close to the Roman pot to help in setting the beam
conditions and to analyze the efficiency to deflect the beam. This paper
describes in details the hardware installed to study the crystal collimation
during 2010.Comment: 15pages, 11 figure, submitted to JINS
Deflection and extraction of Pb ions up to 33 TeV/c by a bent silicon crystal
The first results from an experiment to deflect a beam of fully stripped, ulta-relativistic Pb ions of 400 GeV/c per unit of charge, equivalent to 33 TeV/c, by means of a bent crystal are reported. Deflection efficiencies are as high as 14%, in agreement with theoretical predictions. In a second experiment a bent crsytal was used to extract 270 GeV/c per charge Pb82+ (22 TeV/c) ions from a coasting beam in the CERN-SPS, and a high extraction efficiency of up to 10% was found. These represent the first measurements to demonstrate applications of bent crystals in high energy heavy ion beams
Collimation of a Circulating Beam in the U_70 Synchrotron by Use of Reflections in Axially - Oriented Crystals
The possibilities of the extraction and collimation of a circulating beam by
a new method due to the reflection of particles in crystals with axial
orientation were experimentally investigated in the Fall-2010 run at the U_70
synchrotron. Such crystals have positive features, because the axial potential
is five times larger than the planar potential. It has been shown that the
collimation efficiency can reach 90% due to axial effects in the crystal.
Losses of the circulating beam on a collimator have been reduced by several
times; this makes it possible to suppress the muon jet near the steel
collimator of the circulating beam.Comment: 6 pages, 7 figure
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