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					Statement in summary of VELO construction at time
of EDR
Author: T.J.V.Bowcock


At the time of the EDR (21 April 2005) the VELO module construction is delayed
relative to the expected state in January 2005, as communicated to the LHCC. We
estimate this delay is approximately 2 months.

The single largest contributor to the delay was the discovery that an additional batch
of K-04 hybrids ordered for pre-production modules were heavily warped compared
with earlier prototypes. There are two possible causes: the use of thicker kapton layers
by the manufacturer (the thinner layers are no longer available in the UK) and
changes to the production methodology. New processing should reveal within 1-2
weeks whether this problem/risk may be “retired”. We note that this risk was so
entirely unexpected it did not form part of the “risk register” maintained as part of our
project monitoring tool.

The problems facing transition to the production faced are summarized in another
document for the EDR. The problems that remain that present a serious risk to the
experiment
   1. Low yield of pitch adaptors
   2. Warping of hybrids (discussed above)
We expect a new batch of PA’s within the next few days.

If the remaining problems are overcome and the module losses incurred during
module production are kept to less than about 5% we remain confident (see the EDR
Gantt) the 40 assemblies may be delivered to CERN in early 2006 and of order 10-15
spare assemblies delivered by May 2006. No complete “physics level” assemblies are
expected to be delivered until at least September 2005 although K-04 versions will
start being constructed on receipt of the new batch of K-04’s. The group remains
committed to delivering all assemblies before April ’06 in time for the testbeam at
CERN.

Should the yield of assemblies drop to a (pessimistic) 60%, we expect the final
modules to be delivered in May 2006. In this scenario there will be no spares. This
will be dominated by loss of sensors and the cost of the hybrids. We note a completed
assembly costs approx 40kCHF (capital) and spares are very expensive to
manufacture.

The project is proceeding, even given the problems described above, within 1% of its
original spend profile.

				
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