Abstracts Brochure - CERN

TUPLS012
TUPLS013
TUPLS014
27-Jun-06 16:00 - 18:00 TUPLS — Poster Session
and good electrical behaviour. Beam impedance and magnetic field measurements for the selected stripes are also
presented.
Dynamic Stresses in the LHC TCDS Diluter from 7 TeV Beam Loading
B. Goddard, A. Presland, W.J.M. Weterings (CERN) L. Massidda
(New Affiliation Request Pending)
222
In the event of an unsynchronised beam
abort, the MSD extraction septum of the LHC
beam dumping system is protected from
damage by the TCDS diluter. The simulta-
neous constraints of obtaining sufficient beam dilution while ensuring the survival of the TCDS make the design
difficult, with high thermally induced dynamic stresses occurring in the material needed to attenuate the particle
showers induced by the primary beam impact. In this paper, full 3D simulations are described where the worstcase
beam loading has been used to generate the local temperature rise and to follow the resulting time evolution
of the mechanical stresses. The results and the accompanying design changes for the TCDS, to provide an adequate
performance margin, are detailed.
Protection of the LHC against Unsynchronised Beam Aborts
B. Goddard, R.W. Assmann, E. Carlier, J.A. Uythoven, J. Wenninger,
W.J.M. Weterings (CERN)
An unsynchronised beam abort in the LHC
could cause major damage to other downstream
accelerator components, in particular
the extraction septum magnets, the experi-
mental low-beta triplet magnet apertures and the tertiary collimators. Although the LHC beam dumping system
includes design features to minimise their frequency, such unsynchronised aborts can arise from several sources and
cannot be excluded. A system of protection devices comprising fixed and moveable passive diluters and collimators
will be built to safely protect the downstream LHC aperture from the mis-directed bunches in case of such a failure.
The sources of unsynchronised abort events are described, together with the requirements and design of the protection
devices and their expected performance. The accompanying operational requirements and envisaged solutions
are discussed, in particular the problem of ensuring the local orbit at the protection devices.
Optics Flexibility and Dispersion Matching at Injection into the LHC
A. Koschik, H. Burkhardt, B. Goddard, V. Kain, V. Mertens, T.
Risselada (CERN)
The LHC requires very precise matching of
transfer line and LHC optics to minimise
emittance blow-up and tail repopulation at
injection. The recent addition of a compre-
hensive transfer line collimation system to improve the protection against beam loss has created additional matching
constraints and removed a significant part of the flexibility contained in the initial optics design of the transfer lines.
Optical errors, different injection configurations and possible future optics changes require, however, to preserve
a certain tuning range. Here we present methods of tuning optics parameters at the injection point by using orbit
correctors in the main ring, with the emphasis on dispersion matching. The benefit of alternative measures to enhance
the flexibility, such as the use of more separately powered quadrupoles both in the transfer lines and in the LHC, is
also evaluated.