Abstracts Brochure - CERN

TUPLS126
TUPLS127
TUPLS128
27-Jun-06 16:00 - 18:00 TUPLS — Poster Session
Interaction of the CERN Large Hadron Collider (LHC) Beam with Carbon Collimators
N.A. Tahir, D. Hoffmann (GSI) Y. Kadi, R. Schmidt (CERN) R. Piriz
(Universidad de Castilla-La Mancha) A. Shutov (IPCP)
258
The LHC will operate at 7 TeV with a luminosity
of 10 34 cm-2s-1. Each beam will
have 2808 bunches, with nominal intensity
per bunch of 1.1x10 11 protons. The energy
stored in each beam of 362 MJ. In a previous paper the mechanisms causing equipment damage in case of a failure
of the machine protection system was discussed, assuming that the entire beam is deflected into a copper target.
Another failure scenario is the deflection of beam into carbon material. Carbon collimators and beam absorbers are
installed in many locations around the LHC to diffuse or absorb beam losses. Since their jaws are close to the beam,
it is very likely that they are hit first when the beam is accidentally deflected. Here we present the results of twodimensional
hydrodynamic simulations of the heating of a solid carbon cylinder irradiated by the LHC beam with
nominal parameters, carried out using the BIG-2 computer code* while the energy loss of the 7 TeV protons in carbon
is calculated using the well known FLUKA code**. Our calculations suggest that the LHC beam may penetrate up to
10 m in solid carbon, resulting in a substantial damage of collimators and beam absorbers.
*V. E. Fortov et al. Nucl. Sci. Eng. 123 (1996) 169. **A. Fasso et al. The physics models of FLUKA: status and recent
development, CHEP 2003, La Jolla, California, 2003.
Permanent Deformation of the LHC Collimator Jaws Induced by Shock Beam Impact: an
Analytical and Numerical Interpretation
A. Bertarelli, O. Aberle, R.W. Assmann, A. Dallocchio, T. Kurtyka,
M. Magistris, M. Mayer, M. Santana-Leitner (CERN)
Inspections carried out on jaws of the LHC
collimator prototype, which underwent the
450 GeV robustness test in CERN TT40 extraction
line, revealed no visible damage, ex-
cept a permanent deformation of the jaw metal support of ∼300 um. An explanation of this phenomenon is proposed
in this paper. The temperature increase on the metal support induced by the thermal shock, though limited to ∼70 o C,
led to a sudden expansion of the copper-based support which was partially prevented by the inertia of the material
itself, thus generating compressive stresses exceeding the elastic limit of OFE-copper. An analytical assessment of
the process, followed by a finite-element transient elasto-plastic analysis, is presented. Numerical results are in good
agreement with measured data. In order to confirm this analysis, a special test on series production jaws, where OFEcopper
has been replaced by Dispersion Strengthened Copper (Glidcop®), is scheduled for the second half of 2006.
A New Analytical Method to Evaluate Transient Thermal Stresses in Cylindrical Rods Hit
by Proton Beams
This paper presents an analytical solution
A. Dallocchio, A. Bertarelli, T. Kurtyka (CERN)
for the thermo-mechanical problem of CNGS
target rods rapidly heated by fast extracted
high energy proton beams. The method allows the computation of the dynamic transient elastic stresses induced by a
proton beam hitting off-axis the target. The studies of such dynamic thermo-mechanical problems are usually made
via numerical methods. However, an analytical approach is also needed to quickly provide reference solutions for the
numerical results. An exact solution for the temperature field is first obtained, using Fourier-Bessel series expansion.
Quasi-static thermal stresses are then computed as a function of the calculated temperature distribution, making use