This section to be integrated into the barrel section

The surface integration {Ref 5} activity toke place in an assembling
building close to the ATLAS pit which was shared with the other two
sub-detector of the Inner Detector \[ID\]: TRT and SCT. The working area
is a clean-room class 10000 \[to check\] [equipped]{.mark} with ESD safe
mats to protect electronics during the integration.

![](media/image1.jpeg){width="1.1708333333333334in" height="2.875in"}The
integration activity begins at CERN with assembling of the Bi-stave. Two
staves, loaded respectively with 13 pixel modules, come together in an
assembly sharing a single cooling line. Cable bundles that will connect
each single module to the correspondence location at PP0 are connected
to the module and properly routed along the staves. A rigorous Quality
Assurance Plan (QA) has been set up for the Bi-stave assembling to
exclude electrical, mechanical failures as well the leaks {Ref 4}.
Specifically the leak tightness of the cooling loop has been guaranteed
better than 1x10^-7^ atm.cc/s.

A systematic failure in the micro-cables for the barrel modules was
discovered soon after bi-stave integration and half-shell loading
started. This led to additional quality control tests on all existing
micro-cables and manufacture of new cables with a revised process.
Approximately 50% of the original micro-cables and \>95% of the new ones
passed the final quality control. To minimize delay, the accepted
original cables were used for layer 2, while layers 0 and 1 were
assembled with new cables. The disk micro-cable design is different and
was not subject to this failure mode. Accidental damage to random
micro-cables during handling affected 9 modules. The damage was
accessible and could be repaired in 5 cases, and could be bypassed to
recover full module operation for 3 of the inaccessible cases, leaving
only 1 module lost for operation due to an open sensor bias line.
Electrical contact failures were also detected in 7 service panel
connections, but the exact point of the fault could not be isolated.
These were all bypassed using spare connections or by adding single
wires.

Staves, and consequently Bi-staves, have three different flavors. This
is due to the repair plan that has been set up to recover from a
dangerous corrosion problem that affected the pipes of the first
assembled stave \[see 7.xx.xx\]. One of the repairing scenarios has
foreseen to insert a smaller diameter pipe in the corroded one. The
consequence is a degradation of the thermal properties with an increase
of the temperature of the module. This temperature depends linearly upon
the power generated in the module that is also function of the
integrated fluence on the module. Since the irradiation decreases with
the square of the radius from the interaction point, the benefit of
confining the staves with poor thermal properties at the outermost layer
becomes evident.

Bi-staves are integrated into the HalfShells starting with the layer 2
and proceeding down to the B-Layer. Picture shows one of two HalfShells
with all the bi-staves installed. An electrical test is again performed
once a single bi-stave is loaded in order to detect failures along the
cable bundles or in the module wire-bonds.

![](media/image2.jpeg){width="1.5631944444444446in"
height="2.082638888888889in"}Once the HalfShells were completed they
underwent the geometrical survey. The stave reference point provided by
two ruby balls glued at the ends of each stave are surveyed with respect
to the HalfShell reference points. Since each module has been surveyed
during the modules loading respect to the same references, the location
of the modules in a HalfShell are known. (picture on the side shows the
L2 HalfShell with the ruby balls at the end of the staves). It's worth
to mention that although the modules position is know in Z with the
typical accuracy of a CMM (around 10μm) the inaccuracy in Φ and in R is
significantly worse. In fact stave can bow in HalfShell during fastening
up to 200 μm in Φ on the central support (Z=0). The induced deformation
is predictable only in term of deformation "modes" but not in amplitude
because module could not be surveyed directly on the HalfShell.