231 research outputs found
Summary of session 3 on synchrotron radiation and beam dynamics
Below we summarize presentations, discussions and general conclusions of the
Workshop session on "Beam Dynamics Issues". Major subjects include effects due
to synchrotron radiation (SR), cryogenic loads, electron cloud, impedances,
intra-beam scattering (IBS) and beam-beam interactions.Comment: 2 pp. EuCARD HE-LHC10 AccNet mini-workshop on a High-Energy LHC,
14-16 Oct 2010: Villa Bighi, Malt
Transverse Instabilities of Coasting Beams with Space Charge
Transverse beam stability is strongly affected by the beam space charge.
Usually it is analyzed with the rigid-beam model. However this model is only
valid when a bare (not affected by the space charge) tune spread is small
compared to the space charge tune shift. This condition specifies a relatively
small area of parameters which, however, is the most interesting for practical
applications. The Landau damping rate and the beam Schottky spectra are
computed assuming that validity condition is satisfied. The results are applied
to a round Gaussian beam. The stability thresholds are described by simple fits
for the cases of chromatic and octupole tune spreads.Comment: 6 pages, 2 figures, accepted by Phys. Rev. ST - Accel. Beam
Chromaticity dependence of the transverse effective impedance in the CERN Proton Synchrotron
The current knowledge of the transverse beam coupling impedance of the CERN Proton Synchrotron (PS) has been established with beam-based measurements at different energies. The transverse coherent tune shift as a function of the beam intensity has been measured in order to evaluate the total effective imaginary part of the transverse impedance in the accelerator at the energies of 7, 13 and 25 GeV. Measurements have been performed changing the vertical chromaticity
for each vertical tune scan with intensity. The data analysis revealed an increase of impedance with chromaticity for all the considered energies. The transverse impedance
can be compared with the previously evaluated theoretical impedance budget taking into account the individual contribution of several machine devices
Baseline LHC machine parameters and configuration of the 2015 proton run
This paper shows the baseline LHC machine parameters for the 2015 start-up.
Many systems have been upgraded during LS1 and in 2015 the LHC will operate at
a higher energy than before and with a tighter filling scheme. Therefore, the
2015 commissioning phase risks to be less smooth than in 2012. The proposed
starting configuration puts the focus on feasibility rather than peak
performance and includes margins for operational uncertainties. Instead, once
beam experience and a better machine knowledge has been obtained, a push in
and performance can be envisaged. In this paper, the focus is on
collimation settings and reach in ---other parameters are covered in
greater depth by other papers in these proceedings.Comment: submitted for publication in a CERN yellow report (Proceedings of the
LHC Performance Workshop - Chamonix 2014
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Transverse impedance localization using intensity dependent optics
Measurements of transverse impedance in the SPS to track the evolution over the last few years show discrepancies compared to the analytical estimates of the major contributors. Recent measurements to localize the major sources of the transverse impedance using intensity dependent optics are presented. Some simulations using HEADTAIL to understand the limitations of the reconstruction and related numerical aspects are also discussed
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
Status of LHC Crab Cavity simulations and beam studies
The LHC crab cavity program is advancing rapidly towards a first prototype which is anticipated to be tested during the early stages of the LHC phase I upgrade and commissioning. The general project status and some aspects related to crab optics, collimation, aperture constraints, impedances, noise effects, beam transparency and machine protection critical for a safe and robust operation of LHC beams with crab cavities are addressed here
Observation of focusing of 400 GeV/c proton beam with the help of bent crystals
The results of observation and studies of focusing of 400 GeV/ c proton beam with the help of bent single crystals are presented. Two silicon crystals have been used in the measurements. The focal length of the first and second crystals is found to be 1.48 m and 0.68 m, respectively. The mean square size of the horizontal profile in the focus was 3.1 and 4.3 times as small as at the exit of the crystals
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