1. BCM Overview
Placement such that system is sensitive to all types of beam accidents. => 2 independent subsystems
Halo losses inside the Pixel volume
ie interactions with the Be beampipe section
Showering from outside the TK volume
Concerns for interference
Subsystem 1: One as close as possible to BP
Target = same radius as the inner layer of the pixel barrel
Target = 8mm from beampipe at final position
With no FPix squeeze dist= 14 mm
With FPix squeeze dist =23mm
Subsystem 2: At larger radius
Not at risk of interfence with BP or FPix
Support services
Placement of frontend electronics and services must be adjusted once rail system agreed upon ( BCM treats this issue as secondary, although limited space between BCM rail and FPix service tube feet)
Beam Pipe support wires
Must respect envelop around wires. At present the BP group is requesting an envelop of R= 15mm

2. Concerns
Lateral movement of FPix service cylinder toward beampipe “cuts off” space for BCM insertion
Cabling FPix should done with FPix in final position and before beampipe hook up
BCM and FPix should be independent system
There should not be any holes in coverage of the FPix

3. The problem: BCM and FPix envelopes overlap at rear (z=~2
The problem: BCM and FPix envelopes overlap at rear (z=~2.6m) of FPix service tube

4. Possible “solution”: Very difficult
Kinked BCM rail, straight rail after kink

6. Rotating hinged on the front foot =» outer edge move ~2.5 mm
D = 166mm
d=~2.5mm
Question of gaps in
coverage
Rotating hinged on the front foot =» outer edge move ~2.5 mm

7. Full Squeeze

8. 10mm Squeeze: 1st Layer

9. 10mm Squeeze: 2nd layer

10. 10mm Squeeze: 3rd Layer

11. Notes from Kurt
The reason for the final rotation of the disk structure was of course to get the disk plane perpendicular to the beam.
The advantage was also that from the rear face of the barrel service tube to the rear face of the disk cylinder there was some lateral room which facilitates the sorting of cables/pipes going to the patch panel PP0.
No (or only partial) final rotation would on the other hand facilitate the mounting of the horizontal beam pipe suspension.
No (or only partial) final rotation will of course complicate a lot the software describing the geometry (track reconstruction from hits, alignment....). Also one should check whether there is still overlap of the two half-disks of the most remote disk.
My first guess is that it should be possible to omit the final rotation.
It would imply a correction of the lengths of cables/pipes from the disk structure's end flange to PP0 which have been determined so far assuming full rotation.
For a more educated guess, I should have a layout of the rear face of the disk cylinders as it is foreseen now, in particular the arrangement of cables/pipes exiting the rear end flange of the disk structure.

12. From Bruno

13. Comments on the FWD pixel track
transversal movement in the rail slot of ~35 mm, hinged on front foot with a lever arm of 2209mm: