## 7.6 Integration

In this section we summarize the final integration of the major detector
sub-elements: the barrel half-shells, the endcap units and the internal
services and related supports. The integration of these elements was
carried out in large clean-room area (nominally about class 10,000) that
was used to assemble all of the Inner Detector sub-detectors.

The pixel detector with internal services was assembled on a large,
custom built frame, the Integration and Test Tool (ITT). The ITT was
constructed to allow the use of custom tooling for all assembly and to
allow rotation of the assembled detector to facilitate the assembly and
testing. The basic sequence of assembly was, in order: barrel region,
beam pipe(with temporary supports), endcap units, support units for the
beam pipe and internal services and finally the internal services.
Testing to verify functionality was done as possible in between major
assembly steps. The basic assembly sequence is described below.

![](media/image1.jpeg){width="3.359722222222222in"
height="2.522222222222222in"}Barrel Layer 2 and Layer 1 were in turn
constructed by clamping together the respective half-shells with
bi-staves (described in section 7.2). These layers were inserted
sequentially into the global support frame by using tooling on the ITT.
The Layers 1 and Layer 2 exhaust pipes and capillaries were added only
after the shells were clamped and loaded into the support frame on the
ITT.

![](media/image2.jpeg){width="2.957638888888889in"
height="2.4881944444444444in"}

For the B-layer, exhaust pipes had to be added prior to clamping the
shells because of the reduced access to fittings (at the ends of the
bi-staves) due to the proximity of the beam pipe. The B-layer
half-shells were clamped together around the beam pipe after the beam
pipe was loaded onto the ITT. Figures 7.6.1 (a) and (b) show,
respectively, Layer 2 in the support frame and the full barrel completed
with the beam pipe. Electrical services were temporarily folded back
onto the frame.

Both endcap units were fully integrated into their respective support
frames, including attachment of exhaust pipes and capillaries, prior to
transport to CERN and loading on the ITT. Each endcap was bolted and
pinned for accurate location to the barrel support frame section, again
using tooling on the ITT.

The integration of the Beam Pipe Service Support (BPSS) followed the
attachments of the endcaps. The BPSS has the dual function to support
and adjust the position of the beam pipe and support the Services
Quarter Panels (described in section 7.4).

The four SQP's per side were mounted directly to their respective BPSS.
SQPs were lifted by a small crane and guided by hand onto the BPSS for
final connection. Cooling pipes were connected first at PP0, pressurized
and leak checked. Electrical connectors were plugged into PP0 and an
electrical test performed on each SQP. Figure 7.6.2 shows how the
package looked like with the first SQP installed. Figure 7.6.3 is a view
of the PP0 area after all the services had been connected.

![](media/image3.jpeg){width="2.3868055555555556in"
height="2.0180555555555557in"}![](media/image4.jpeg){width="6.402777777777778in"
height="2.59375in"}

Cooling pipe circuits underwent vacuum leak checks after each fitting
connection. Within the pixel package, each cooling circuit has a U-link
with two fittings ganging staves or sectors, one exhaust tube with two
fittings connecting a bi-stave or bi-sector to a service panel heat
exchanger exhaust, and one capillary with two fittings connecting to the
same heat exchanger. A pressurization test at 4 bar absolute using dry
air was carried out for one minute after the capillaries and exhaust
pipes had been added and for 24 hours after the full package had been
integrated, always followed by a vacuum leak check. This was the highest
pressure for which the local supports (sectors and staves) had been
qualified. While this pressure should not be reached in the exhaust
circuits during normal operation, all inlet circuits must operate at 16
bar(a), and therefore have not been individually tested at final
pressure in the full package. A small number of cooling fittings (4) and
one capillary tube failed during the integration process. These were
repaired in place and subsequently tested successfully.

The integration of a single service panel was also followed by a
connectivity test. This was performed using the full readout chain and
employed the same services as the system test (section 8). Its general
goal was to make sure that the full pixel package was ready for the
installation in the ATLAS underground hall. More specifically the module
micro-cable mapping was checked, the environmental and electrical
connections were exercised and the optical connections were tuned. Note
that this test was performed without cooling.

Active component failures not caused by handling were encountered at a
low level in the integrated package. One front-end readout chip failed
in a disk module by developing an internal short. The module
functionality except for this chip was recovered by breaking wire bonds
to isolating the failed chip. Two optical components failed: one channel
of a laser diode array and one channel of a photodiode array. In both
cases the failure was confirmed to be internal to the component and
could not be repaired. However, in both cases the affected modules were
moved to spare service slots. One module was discovered with an unusual
defect that prevents it from operating with the final optical
communication, yet it operated with a pure electrical readout as used
for production testing.

The data from the connectivity test, combined with the detailed
production data, tell us that 99.7% of the detector is currently
operational (0.1% due to module/optoboard-level failures, 0.2% due to
pixel-level failures). Table 7.6.1 summarizes the fraction of
non-working parts of the pixel detector as a function of the barrel and
end-cap layers, both before and after the connectivity test.

  --------- ------------- ------------------ ------- -------------- ---------------- -------
            After disk                               After                           
            and bistave                              connectivity                    
            integration                              test                            

            pixel         Fe or Module       total   pixel          Fe or Module     total

  L2        0.29          0                  0.29    0.29           0                0.29

  L1        0.20          0                  0.20    0.20           0.20             0.40

  L0        0.07          0                  0.07    0.07           0                0.07

  D1C       0.12          0                  0.12    0.12           0                0.12

  D2C       0.11          0                  0.11    0.11           2.08             2.19

  D3C       0.18          0                  0.18    0.18           0.13             0.31

  D1A       0.14          0                  0.14    0.14           0                0.14

  D2A       0.10          0.13               0.23    0.10           0.13             0.23

  D3A       0.26          0.13               0.36    0.26           0.13             0.39
  --------- ------------- ------------------ ------- -------------- ---------------- -------

Table 7.6.1 Inefficiency in % for barrel and disk layers (1) before
final integration and (2) after final integration and connectivity test
described in the text. Pixel inefficiencies are those seen in individual
module testing(section 6) and are assumed to be the same after final
integration as before. The column FE or Module indicates the fraction
resulting from inoperative front-end chips or complete modules.