## 7.1 Overview

The mechanical elements and services of the pixel detector are described
in this section. We also describe the integration of the major
components of the pixel detector and installation in ATLAS. The pixel
detector, including the internal services, is located within the pixel
support tube (PST) as already shown in Figure 2.1. A perspective view of
the pixel detector elements within the PST is shown in Figure 7.1.1.

![](media/image1.png){width="3.938888888888889in"
height="3.404166666666667in"}

Figure 7.1.1 A perspective view of the pixel detector and internal
services. \*\*\*\*Placeholder\*\*\*\*

The active regions of the pixel detector are divided into a barrel
region and two identical endcaps. The active elements in the barrel
region are staves (with integrated cooling) each supporting 13 modules.
The staves are held precisely by half-shells that are joined to form the
three barrel layers of the detector. The active elements in the endcap
regions are disk sectors (also with integrated cooling) each supporting
six modules. Eight disk sectors are supported on a disk support ring.
There are three disks in each of the two endcaps. The design and
construction of these barrel and endcap elements are described in
subsequent sections of this chapter.

The barrel shells and the disk rings are rigidly supported by a support
frame constructed in three sections -- a barrel section and two
identical endcap sections. The support frame is constructed from carbon
composites apart from small aluminum blocks in the regions where the
barrel and endcap frame sections are bolted together. A picture of the
support frame is shown in Figure 7.1.2. Four pixel mounts are mounted on
endplates attached to the support frame.. These precision mounts engage
mating supports in the PST when the support frame and the attached
services slide through the PST during the installation procedure.

![](media/image2.jpeg){width="3.002083333333333in"
height="2.071527777777778in"}

Figure 7.1.2The pixel detector support frame.
\*\*\*\*Placeholder\*\*\*\*

The beryllium beam pipe \[Ref\] within the ATLAS detector is held on
each side of the support frame by additional composite structures, the
Beam Pipe Support Structure (BPSS). The BPSS also supports the Service
Quarter Panels (SQP) that contain coolant pipes and all electrical
services for the pixel modules\[Section 6\]. A low mass cable from each
pixel module (Type 0 cable) is connected to the SQPs via small
connectors at Patch Panel 0 (PP0 -- see Figure 7.1.1). The connections
to the external services for the pixel detector are made to the SQPs at
Patch Panel 1 (PP1) that is at the end of the Pixel Support Tube.

A schematic overview of the pixel electrical and optical services is
given in Figure 7.1.3.

![](media/image3.png){width="5.302083333333333in" height="3.28125in"}

Figure 7.1.3 Schematic of the pixel electrical and optical services.
\*\*\*\*Placeholder\*\*\*\*

Optical transceivers (optoboards) are located on the SQPs (see 4.4 for a
description of the optical system). Power for the pixel modules is
supplied by power supplies located in the ATLAS services caverns \[Ref\]
and is regulated at the Patch Panel 2 (PP2) location. High voltage is
supplied by power supplies in the service caverns. Routing of low
voltages and high voltages occurs at the Patch Panel 4 (PP4) region.
Monitoring (and power distribution for the optical items) occurs at the
Patch Panel 3 (PP3) region.

Cooling connections are also made at PP0 and at PP1. Individual heat
exchangers for each pixel cooling circuit are embedded in the Service
Quarter Panels. The heater exchangers and these connections are
described briefly below in section 7.4. A general description of the
ATLAS evaporative cooling system may be found in \[Ref\].