Click here to download the abstract booklet in pdf format - MT19 - Infn

MOA06PO04
LHC Superconducting Dipoles Production Follow-up:
Results of Audit on QA aspects in industry
M. Modena, M. Bajko, M. Cornelis, D. Tommasini, P.
Fessia, J. Miles, G. De Rijk, F. Savary, S. Sgobba, J.
Vlogaert, C. Voellinger, E. Wildner, CERN.
The manufacturing of the 1232 Superconducting Main
Dipoles for LHC is under way at three European Industries
Alstom/Jeumont Consortium, Ansaldo Superconduttori
Genova (ASG) and Babcock, Noell Nuclear (BNN). The
manufacturing is proceeding in a very satisfactory way and
in March 2005 we passed the mid production. To intercept
eventually “weak points” of the production process still
present and in order to make a check of the Quality
Assurance and Control in place for the series production,
an Audit action was launched by CERN during summer-fall
2004. Aspects like: completion of Production and QA
documentation, structure of QC Teams, traceability,
calibration and maintenance for tooling, incoming
components inspections, were checked during a total of
seven visits at the five different production sites. The
results of the Audit in terms of analysis of “systematic” and
“random” problems encountered as well as corrective
actions requested are presented.
MOA06PO05
A correlation study between geometry of collared coils
and normal quadrupole multipole in the main LHC
dipoles
F. Bertinelli, S. Berthollon-Vitte, D. Glaude, I. Vanenkov,
CERN; E. Boter-Rebollo, CELLS.
The quality control implemented at all LHC dipole
manufacturers includes precise mechanical measurements
of the geometry of collared coils. A cross-analysis
performed between mechanical and magnetic
measurements data shows a correlation between collared
coils outer dimensions and the normal quadrupole
multipole (b2) for one dipole manufacturer. The profile
geometry of the single collars - as determined from 3D
measurements at the collar suppliers and CERN - could
not account alone for the significant left – right aperture
asymmetry observed. This triggered a deeper investigation
on different elements of the geometry of single collars. The
results of this work show that the relative positioning of the
collaring holes, allowing a small bending deformation of
collars under the effect of coil pre-stress, is an important
effect which generates a b2 multipole at the limit of
specification. The study has deepened the understanding
of the factors affecting collared coil geometry and field
quality. The precision of 3D measurements at the collar
suppliers and at CERN has been improved, and a tighter
quality control has been introduced at the collar suppliers.
MOA06PO06
Dependence of magnetic field quality on collar
manufacturing and dimensions in the main LHC
dipoles
B. Bellesia, F. Bertinelli, E. Boter-Rebollo, L. Rossi, C.
Santoni, E. Todesco, CERN.
In order to keep the electro-magnetic forces and to
minimize conductor movements, the superconducting coils
of the main Large Hadron Collider dipoles are held in place
by means of austenitic stainless steel collars. Two
manufacturers provide the collars necessary for the whole
LHC production, which has reached now more than 700
collared coils. In this paper we first assess if the different
collar manufacturers origin a noticeable difference on the
magnetic field quality measured at room temperature. We
then analyze the measurements of the collar dimensions
carried out at the manufacturers, comparing them to the
geometrical tolerances. Finally we use a magneto-static
model to evaluate the expected spread in the field
components induced by the actual collar dimensions.
These spreads are compared to the magnetic
measurements at room temperature over the magnet
production in order to identify if the collars, rather than
other components or assembly process, can account for
the measured magnetic field effects.
MOA06PO07
Electrical integrity tests during production of the LHC
main dipoles
G. de Rijk, M. Bajko, M. Cornelis, P. Fessia, J. Miles, M.
Modena, G. Molinari, F. Savary, J. Vlogaert, CERN.
For the LHC dipoles, mandatory electrical integrity tests are
performed to qualify the cold mass at four production
stages: individual pole, collared coil, cold mass before end
cover welding and final cold mass. A description of the
measurement equipment and its recent development are
presented. After passing the demands set out in the
specification, the results of the tests are transmitted to
CERN where they are further analysed. The paper
presents the most important results of these
measurements. We also report a review of the electrical
non-conformities encountered e.g. inter-turn shorts and
quench heater failure, their diagnostic and the cures.
MOA06PO08
Identification of assembly faults through the detection
of magnetic field anomalies in the production of the
LHC dipoles
C. Vollinger, E. Todesco, CERN.
Magnetic measurements at room temperature have been
used to monitor the production of the superconducting coils
of the Large Hadron Collider main dipoles. They have
made it possible to identify several assembly errors, e.g.
cases of bad gluing of the coil layers, bad conductor
positioning, missing pole shims and other problems related
to faulty procedures. This paper reviews the experience
accumulated so far considering almost 1000 dipoles. After
a short outline of the method used to pin out field
anomalies and deduce realistic deformation of the coil, an
exhaustive list of the cases met during the production is
given. A discussion follows on the findings after decollaring
as compared to the predictions, including the still open
cases.
MOA06PO09
Short circuit localization in the LHC main dipole with
room temperature magnetic field measurements
B. Bellesia, E. Todesco, G. Molinari, CERN; C. Santoni,
University of Clermont Ferrnad.
During the production of the LHC main dipole few cases of
short circuits have been found, some of them detectable
only under the collaring press. In this paper we present a
method based on the analysis of magnetic measurement at
room temperature which has allowed finding the position of
the defect, repairing it, and reusing the coils. The presence
of a short circuit strongly perturbs the magnetic field. The
observed field pattern is compared to a library of standard
perturbations that could arise from short circuits between
turns and layers. The longitudianl sampling of the magnetic
field allows identifying the position of the short circuit to
within the length of the magnetic field measuring mole. The
result of this localization procedure is presented and
correlation with extensive electric investigations and
actions to cure the short circuits are discussed.
MT-19 2005, Genova 34