Abstracts Brochure - CERN

TUODFI — Circular Colliders 27-Jun-06 15:00 - 16:00
TUODFI — Circular Colliders
The Final Collimation System for the LHC
The LHC collimation system has been re-designed
over the last three years in order to R.W. Assmann (CERN)
address the unprecedented challenges that
are faced with the 360 MJ beams at 7 TeV. The layout of the LHC has now been fixed and a final approach for
collimation and cleaning has been adopted. In total 132 collimator locations have been reserved in the two LHC
rings and can be installed in a phased approach. Ninety collimators of five different types will be available for initial
beam operation. The system has been fully optimized for avoiding quenches of super-conducting magnets during
beam losses and for sufficient survival of beamline components against radioactive dose. The phased approach for
LHC collimation is described, the various collimators and their functionalities are explained, and the expected system
performance is summarized.
DAFNE Experience with Negative Momentum Compaction Factor
There are several potential advantages for a
collider operation with a lattice having a negative
momentum compaction factor (alfa):
bunches can be shorter and have a more reg-
M. Zobov, D. Alesini, M.E. Biagini, A. Drago, A. Gallo, C. Milardi,
P. Raimondi, B. Spataro, A. Stella (INFN/LNF)
ular shape; longitudinal beam-beam effects and synchrobetatron resonances are predicted to be less dangerous;
requirements on sextupole strengths can be relaxed because there is no head-tail instability with the negative chromaticity.
Since the lattice of the Frascati e + e − Phi-factory DAFNE is flexible enough to provide collider operation with
alfa < 0, we have exploited this possibility to study experimentally the beam dynamics. The negative momentum
compaction lattices have been successfully implemented and stable 1 A currents have been stored in both the electron
and positron rings without any problem for RF cavities and feedback systems operation. First collisions have been
tested at low currents. In this paper we describe the experimental results and compare them with expectations and
numerical simulations. Present limitations to DAFNE operation with alfa < 0 are also discussed.
Operational Status of CESR-c
We summarize recent running experience at
the Cornell Electron Storage Ring operating J.A. Crittenden (Cornell University, Department of Physics)
as a high-statistics production-threshold factory
for mesons containing charm quarks. Since beginning operation at beam energies near 2 GeV in late 2003, CESR
has accumulated world-record samples of D and Ds meson decays and has also operated in an energy-scanning
mode, making unique contributions to the presently very active field of charm spectroscopy. CESR lattice design is
characterized by the versatility provided by the variety of beam-line components applied to the challenges imposed
by the beam-beam interactions at the parasitic crossing points in the pretzel orbits and the necessity of powerful
superconducting wiggler magnets used to tune damping and emittance. We describe the observed tune-plane, beamcurrent
and luminosity limits, as well as our understanding of their sources and near-term plans for operational
improvements.
Chair: E. Levichev (BINP SB RAS, Novosibirsk) 159
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