Abstracts Brochure - 2nd International Particle Accelerator Conference

Poster Panel 1
ID: 4068 - TUPZ028
Beam Based Optimization of the Squeeze at the
LHC, Xavier Buffat (EPFL, Lausanne),
Mike Lamont, Stefano Redaelli, Jorg Wenninger
(CERN, Geneva) - The betatron squeeze is a critical
operational phase for the LHC because it is carried
out at top energy, with the maximum stored energy
and with reduced aperture margins in the
superconducting triplets. A stable operation with
minimum beam losses must be achieved in order to
ensure a safe and efficient operation. The
operational experience at the LHC showed that this
is possible. The operation in 2010 is reviewed. In
particular, orbit, tune and chromaticity
measurements are investigated and correlated to
beam losses. Different optimizations are then
proposed towards a more efficient and robust
operation. The improvements obtained for the
operation in 2011 are presented.
Sub Classification: A01 Hadron Colliders
Poster Panel 2
ID: 3840 - TUPZ015
Electron Cloud Parameterization Studies in the
LHC, César Octavio Domínguez,
Gianluigi Arduini, Vincent Baglin, Giuseppe
Bregliozzi, José Miguel Jimenez, Elias Métral,
Giovanni Rumolo, Daniel Schulte, Frank
Zimmermann (CERN, Geneva) - During LHC beam
commissioning with 150, 75 and 50-ns bunch
spacing, important electron-cloud effects, like
pressure rise, cryogenic heat load, beam instabilities
or emittance growth, were observed. The main
strategy to combat the LHC electron cloud relies on
the surface conditioning arising from the chambersurface
bombardment with cloud electrons. In a
standard model, the conditioning state of the beampipe
surface is characterized by three parameters: 1.
the secondary emission yield; 2. the incident
electron energy at which the yield is maximum; and
3. the probability of elastic reflection of low-energy
primary electrons hitting the chamber wall. Since at
the LHC no in-situ secondary-yield measurements
are available, we compare the relative local
pressure-rise measurements taken for different beam
configurations against simulations in which surface
parameters are scanned. This benchmark of
measurements and these simulations is used to infer
the secondary-emission properties of the beam-pipe
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Classification 1: Circular Colliders
2
at different locations around the ring and at various
stages of the surface conditioning. In this paper we
present the methodology and first results from
applying the technique to the LHC.
Sub Classification: A01 Hadron Colliders
Poster Panel 3
ID: 3732 - TUPZ003
Simulation of Electron-cloud Build-Up for the
Cold Arcs of the LHC and Comparison with
Measured Data, Georfrey Humberto Israel Maury
Cuna, Jesús Guillermo Contreras Nuño
(CINVESTAV, Mérida), Gianluigi Arduini,
Giovanni Rumolo, Laurent Tavian, Walter Venturini
Delsolaro, Frank Zimmermann (CERN, Geneva) -
The electron cloud generated by synchrotron
radiation or residual gas ionization is a concern for
LHC operation and performance. We report the
results of simulations studies which examine the
electron cloud build-up, at injection energy, at 4
TeV and at 7 TeV for various operation parameters,
e.g. different bunch spacings. In particular we
determine the value of the secondary emission yield
corresponding to the multipacting threshold, and
investigate the electron density, electron flux, and
heat load as a function of bunch intensity for
dipoles, quadrupoles, and field-free regions. We also
include a comparison between simulations results
and measured heat-load data from the LHC
scrubbing runs in 2010 and 2011.
Sub Classification: A01 Hadron Colliders
Poster Panel 4
ID: 3326 - THPZ011
Dynamic Aperture Optimization at BEPCII
Storage Rings, Zhe Duan, Qing Qin (IHEP Beijng)
- The upgrade machine of the Beijing Electron-
Positron Collider (BEPCII) has reached about 2/3 of
its design luminosity. Further increase in its
efficiency requires a better dynamic aperture, which
is currently the bottle neck of the beam lifetime.
With only chromatic sextupoles placed in the arc
area and no local compensation in the low beta
insertion, the current 4 groups scheme of sextupole
configuration seems not good enough. Instead, 18
groups of sextupoles are optimized with genetic
algorithm and a better result of dynamic aperture is
obtained.
Sub Classification: A02 Lepton Colliders