Abstracts Brochure - CERN

MOPLS — Poster Session 26-Jun-06 16:00 - 18:00
thresholds for quenches. Further simulations of beam losses caused by collimation and electromagnetic interactions
peculiar to heavy ion collisions determine the positions of extra BLMs needed for ion operation in the LHC.
Beam Halo on the LHC TCDQ Diluter System and Thermal Load on the Downstream Superconducting
Magnets
The moveable single-jawed graphite TCDQ
diluter must be positioned very close to the
circulating LHC beam in order to prevent
damage to downstream components in the
B. Goddard, R.W. Assmann, A. Presland, S. Redaelli, G. Robert-
Demolaize, L. Sarchiapone, Th. Weiler, W.J.M. Weterings (CERN)
event of an unsynchronised beam abort. A two-jawed graphite TCS collimator forms part of the TCDQ system. The
requirement to place the TCDQ and TCS jaws close to the beam means that the system can intercept a substantial
beam halo load. Initial investigations indicated a worryingly high heat load on the Q4 coils. This paper presents the
updated load cases, shielding and simulation geometry, and the results of simulations of the energy deposition in the
TCDQ system and in the downstream superconducting Q4 magnet. The implications for the operation of the LHC
are discussed.
The LHC as a Proton-nucleus Collider
Following its initial operation as a proton-proton
(p-p) and heavy-ion (208Pb J.M. Jowett, C. Carli (CERN)
82+ -
208Pb 82+ ) collider, the LHC is expected to
operate as a p-Pb collider. Later it may collide protons with other lighter nuclei such as 40Ar 18+ or 16O 8+ . We show
how the existing proton and lead-ion injector chains may be efficiently operated in tandem to provide these hybrid
collisions. The two-in-one magnet design of the LHC main rings imposes different revolution frequencies for the two
beams in part of the magnetic cycle. We discuss and evaluate the consequences for beam dynamics and estimate the
potential performance of the LHC as a proton-nucleus collider.
Measurement of Ion Beam Losses Due to Bound-free Pair Production in RHIC
When the LHC operates as a Pb 82+ ion collider,
losses of Pb 81+ ions, created through
Bound-free Pair Production (BFPP) at the collision
point, and localized in cold magnets,
J.M. Jowett, S.S. Gilardoni (CERN) R. Bruce (MAX-lab) K.A. Drees,
W. Fischer, S. Tepikian (BNL) S.R. Klein (LBNL)
are expected to be a major luminosity limit. With Au 79+ ions at RHIC, this effect is not a limitation because the Au 78+
production rate is low, and the Au 78+ beam produced is inside the momentum aperture. When RHIC collided Cu 29+
ions, secondary beam production rates were lower still but the Cu 28+ ions produced were predicted to be lost at a welldefined
location, creating the opportunity for the first direct observation of BFPP effects in an ion collider. We report
on measurements of localized beam losses due to BFPP with copper beams in RHIC and comparisons to predictions
from tracking and Monte Carlo simulation.
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