16 Integration of Detectors into a Large Experiment: Examples from ATLAS. . .
717
Fig. 16.9 Drawing showing the sensors and structural elements traversed by two charged tracks
of 10 GeV p T in the ATLAS end-cap inner detector (η = 1.4 and 2.2). The end-cap track at η =
1.4 traverses successively the beryllium beam-pipe, the three cylindrical silicon-pixel layers with
individual sensor elements of 50 × 400 μm 2 , four of the disks with double layers (one radial and
one with a stereo angle of 40 mrad) of end-cap silicon-microstrip sensors (SCT) of pitch ∼80 μm,
and approximately 40 straws of 4 mm diameter contained in the end-cap transition radiation tracker
wheels. In contrast, the end-cap track at η = 2.2 traverses successively the beryllium beam-pipe,
only the first of the cylindrical silicon-pixel layers, two end-cap pixel disks and the last four disks
of the end-cap SCT. The coverage of the end-cap TRT does not extend beyond |η| = 2
Table 16.6 Main parameters of the ATLAS tracker system
Item
Radial extension
[mm]
Length [mm]
Overall tracker
envelope
0 < R < 1150
0 < |z| < 3512
Beam-pipe
29 < R < 36
Pixel
Overall envelope
45.5 < R < 242
0 < |z| < 3092
3 cylindrical layers
Sensitive barrel
50.5 < R < 122.5
0 < |z| < 400.5
2 × 3 disks
Sensitive end-cap
88.8 < R < 149.6
495 < |z| < 650
SCT
Overall envelope
255 < R < 549
(barrel)
0 < |z| < 805
251 < R < 610
(end-cap)
810 < |z| < 2797
4 cylindrical layers
Sensitive barrel
299 < R < 514
0 < |z| < 749
2 × 9 disks
Sensitive end-cap
275 < R < 560
839 < |z| < 2735
TRT
Overall envelope
554 < R < 1082
(barrel)
0 < |z| < 780
617 < R < 1106
(end-cap )
827 < |z| < 2744
73 straw planes
Sensitive barrel
563 < R < 1066
0 < |z| < 712
160 straw planes
Sensitive end-cap
644 < R < 1004
848 < |z| < 2710