Dr
Brennan Goddard
(CERN)
Case study: Energy deposition in superconducting magnets in IR6
A diluter block TCDQ, with a collimator TCS and shield TCDQM, will be
installed in front of the superconducting quadrupole Q4 magnet in
IR6, to protect it and other downstream LHC machine elements from an
unsynchronised beam dump. The system should also intercept particles
in the abort gap to prevent quenches during regular aborts, and must
also intercept the particles from the...
Dr
Vasilis Vlachoudis
(CERN)
Case study: Energy deposition in superconducting magnets in IR7
The IR7 insertion of the Large Hadron Collider (LHC) is dedicated to
beam cleaning with the design goals of absorbing part of the primary
beam halo and of the secondary radiation. The tertiary halo which
escapes the collimation system may heat the cold magnets at
unacceptable levels, if no absorber is used. In order to assess the
energy deposition in the sensitive components,...
Verena Kain
(CERN)
Experiment for energy deposition in a target
Material damage levels for LHC intensities and energies are in
general derived from computer simulations calculating static energy
deposition. A dedicated experiment was carried out to cross-check the
validity of this approach: With a 450GeV proton beam extracted from
the SPS in TT40, material was deliberately damaged in a controlled
way. A simple geometry was chosen for the high-Z...
Dr
Vincent Baglin
(CERN)
Heat loads from beam
The circulating beam in the LHC generates heat loads which are
dissipated onto the beam screen or in the cold masses of the elements
operating at cryogenic temperature. The synchrotron radiation emitted
by the proton beam is intercepted by the beam screens. These beam
screens are also carrying the beam image current which dissipates
power. Finally, the heat load induced by the...
Dr
Rob van Weelderen
(CERN)
Heat transfer in superconducting magnets
Using the present LHC inner triplets, functioning in pressurized
superfluid helium, I will classify the heat extraction paths from
coil until cold source and identify the limits of the present design.
This will be exemplified by the measurements made using the Inner
Triplet Heat eXchanger (IT-HXTU). The areas in need for improvement,
when going to higher heat loads, will be...
Prof.
George Smirnov
(Joint Institute for Nuclear Research)
Heavy ion interactions with matter
The effects of the interaction of heavy ions with matter caused by
strong electromagnetic fields produced by ultrarelativistic ions are
briefly reviewed. An important feature is that electromagnetic
processes compete with hadronic reactions. Moreover, in certain
kinematics, like in very peripheral collisions, electromagnetic
dissociation processes become dominant. The pair production...
Dr
Ralph Assmann
(CERN)
Introduction to the session
The crucial role of quench limits in LHC is pointed out and some
important workshop
and session goals are discussed.
Dr
Simone Gilardoni
(CERN)
Ion operation and beam losses
The electromagnetic collisions of Lead ions can change the ions charge
state due to electron capture via pair production (Bound-Free Pair
Production ).
Many electron-positron pairs are created in the intense
electromagnetic fields of the nuclei. In some cases, the electron is
created in a bound-state of one nucleus.
These wrongly charged ions are lost in the dispersion suppressor...
Mr
Rüdiger Schmidt
(CERN)
LHC and magnet operation
The current of the main dipole and quadrupole magnets will ramp
proportional to the momentum of the particles accelerated in the LHC,
for protons from 450 GeV/c to 7 TeV/c. For those magnets, the quench
margin will be largest at injection. For other magnets, the current
could follow different ramps that needs to be considered for
the quench margin.
When the beams are squeezed to...
Dr
ranko ostojic
(CERN)
Insertions magnets and IR radiation
The pp collisions in the LHC interaction points generate at nominal
luminosity about
900 W carried away by secondaries to each side of an experimental
insertion. This
energy is largely intercepted by the TAS and TAN absorbers, but a non-
negligable
part ends up in the coils of the superconducting low-beta
quadrupoles. These magnets
have to sustain and evacuate a load of...
Dr
Bertrand BAUDOUY
(CEA - SACLAY)
Liquid helium heat transfer in superconducting cables insulation of accelerator magnets
The electrical insulation of superconducting cables poses the largest
heat barrier between the heat exchanger and the cable for accelerator
magnets.
This issue is of major importance for current accelerator magnets and
undoubtedly will become a critical issue for magnets subjected to a
higher heat deposition. We will first present a review of heat
transfer studies on the LHC cable...
Dr
Arjan Verweij
(CERN)
Modelling stability on Nb-Ti cables; R&D on stability planned in the Cern cable test facility FRESCA
A brief overview will be given of the possibilities of modelling
stability in superconducting NbTi cables. It will be shown that in
many cases the accuracy of the modelling is poor (due to limited
knowledge on cooling and current redistribution phenomena), so that
additional experiments are needed. In the coming years, such
experiments will be performed in the CERN cable test...
Mr
Guillaume ROBERT-DEMOLAIZE
(CERN)
Multiturn beam losses
Due to the large amount of energy stored in the LHC ring, cleaning of
the beam halo is necessary in order to avoid quenches of the LHC
superconducting magnets.
We review the mechanisms of multi-turn beam losses and design
parameters of the LHC collimation system, and present the cleaning
performance for various beam lifetimes scenarios, both at injection
and top energy.
Results of...
Nikolai Mokhov
(FERMILAB)
Protecting Superconducting Magnets from Radiation at Tevatron, SSC, LHC and its upgrades.
The principal challenges arising from beam-induced energy deposition
in superconducting magnets at hadron colliders are described.
Radiation constraints are analyzed that include quench stability,
dynamic heat loads on the cryogenic system, radiation damage limiting
the component lifetime, and residual dose rates related to hands-on
maintenance. These issues are especially challenging...
Dr
Andrzej Siemko
(CERN)
Quench levels – experience from magnet tests at CERN
When does the magnet quench?
MQE and MPZ concept
Is it relevant for beam induced quenches?
Quench levels of various families of the main ring superconducting magnets
Outlook on further simulations and envisaged experiments
Conclusions
Kay Wittenburg
(DESY)
Quench levels and transient beam losses at HERA
The talk recalls the main parameters which defined the expected beam
loss generated quench levels (in 1985) and compares the results with
measurements of loss induced quenches at HERA during 1994-2005. The
parameters of the BLM system are discussed (like calibration,
positioning, alarm level, etc.) and the response of the system to
beam loss induced quenches with different time...
Mr
luca bottura
(CERN)
MEB and magnet sorting criteria
The allocation of magnets at MEB is presently following guidelines on
sorting derived from quench training curves. These guidelines are
based on working assumptions rather than well established results.
The presentation lists the open questions to be resolved for a sound
sorting.
Dr
Daniel Leroy
(CERN)
Review of past estimations of the induced quench levels by beam losses in the LHC dipoles
xxx
Dr
Marco Calvi
(CERN, AT Department, MTM group)
SPQR – could it contribute?
The thermal and electrical equations implemented in SPQR code are
presented and possible improvements underlined. The approach used to
numerically solve them is briefly recalled and the technique adopted
to calculate the minimum quench energy (MQE) clarified. Examples of
MQE calculations are presented for different space and time
perturbations and the minimum propagation zone (MPZ)...
Dr
Alexander Zlobin
(Fermilab)
Thermal analysis and its experimental verification for the present and future IR triplets
The first generation of low-beta quadrupoles for the LHC IR inner
triplets based on NbTi superconductor was developed by KEK and
Fermilab in collaboration with CERN. The magnets were designed to
achieve the nominal luminosity of 10^34 cm^- 2s^-1. They provide a
nominal field gradient of 200 T/m with a 20% margin at the high
luminosity insertions with 70-mm coils, and operate at 1.9K...
Dr
Francesco Broggi
(INFN - LASA Lab.)
Thermal modelling of IR quadrupoles
Abstract – In this talk is presented the work carried out at LASA
Laboratory in the years 1995 - 1999, related to the design of a new
type of quadrupoles for the LHC low-beta insertion based on Nb3Sn
technology.
The work deals of the power generated into the insertion quads from
the reaction products of the 7TeV p-p collision in the high
luminosity interaction point of LHC.
The...
Dr
Brennan Goddard
(CERN)
Transient beam losses at injection and during beam dump
The injection and beam dump processes are designed to avoid any beam
losses. However, situations will occur in which these processes are
not carried out correctly, for instance with out of tolerance beam
characteristics, wrong settings or equipment failures. In these cases
beam losses can occur. Damage to accelerator equipment should be
prevented by the Machine Protection systems,...
Mr
David Richter
(CERN)
Understanding AC losses for LHC magnets
Brief comparison of results of the direct heat transfer measurement
done on stacks of cables by B. Baudouy, L. Burnod, D. Leroy, C.
Meuris, and B. Szeless with corresponding results based on the ramp
rate limitation of the first LHC model dipoles by A. P. Verweij, in
the period 1991-99.
Bernd Dehning
(CERN)
Why do BLMs need to know the quench levels?
The LHC beam loss monitoring system is based of the detection of
secondary shower particles, which depose their energy in the
accelerator equipment and finally also in the monitoring detector. To
protect the equipment and to prevent quenches the likely loss
locations have to be identified by tracking simulations or by using
low intensity beams. To keep the operational efficiency...
