1. Ultra Low Mass Mechanics with CO2 Cooling for a Future 4 Layer Barrel Pixel Detector
Silvan Steuli
Roland Horisberger
Stefan König
CMS Upgrade Workshop
FNAL
20 Novemer 2008

2. Current BPIX Mechanics
Two identical half shells
1 type of fullmodule
2 types of halfmodules
At least 100 different cablelenghts

3. Wishlist BPIX mechanics for 2013
Only one type of modules
Simpler mechanics
Two identical half shells
All modules with same cablelenght
More clearance between half shells
Layer 1 closer to beampipe (44mm → 39mm)
BPIX wheels adjustable in X andY (±3mm)
→ adapt to real situation
→ safer tolerances
CO2 cooling
....

4. Possible number of faces
18 faces (the current BPIX layer 1)
Top face displaced inwards
Bottom face displaced outwards
Half shells are not equal
This design requires: # faces = even number
16 faces (BPIX Layer 1, 2013)
Top & bottom faces displaced outwards
Half shells are equal
This design requires: # faces = multiple of 4

5. New BPIX layout for 2013 (proposal)
Two identical half shells
1 type of fullmodule only
Layer 1: R 39mm; 16 faces
Layer 2: R 68mm; 28 faces
Layer 3: R 109mm: 44 faces
Layer 4: R 160mm: 64 faces
Clearance to beampipe 4mm

6. Clearance to beampipe support
Insertion:
Minimum clearance to beampipe support is 10.5mm @ z= 1635mm.

7. 3D view BPIX halfshell mechanics 2013
Adjustable wheel
Half BPIX detector
only one endflange shown

8. 3D view BPIX detector mechanics 2013

9. h coverage of 4 Layer Pixel System10 20 30 40 50
Number of pixel modules in 4 layers system ~1.8 times of old 3 layers system.

10. Transverse View of 4 Layer Barrel with FPIX Envelope
BPIX supply tube
BPIX cabling envelope
FPIX envelope
need approval soon!

11. Modified Mechanics for CO2 Cooling
Cooling pipes stainless steel. Diameter d = 1.50mm and wall thickness t = 50mm
 pmax = 275 bar safety factor 3  pop = 90bar
Layer 1 r=3.9cm
Diamond filled Araldite
19 Nov 2008
90 bar
Old
New

12. Temperature Distribution of module around CO2 tube
Temperature profile of halfside of new BPIX module
Silicon Sensor (t=300mm)
ROC 75 mm
ROC Power 120mW
2/3 Periphery 2mm
1/3 Pixel area 8mm
C-fibre facets(t= 300mm)
 heat transfer to tube is ok with reduced option !

13. Cooling Pipe Connections to Supply Tube
Micro-SERTO
Stainless tubes
D=1.5mm, t= 50mm
20 coolling loops per half shell  2 m loop length !

14. Cassette with rails for pixel-insertion tests
Rails for FPIX / BPIX
Ribs to emulate TIB & bulkhead inner envelope
Cassette made out of Corapan (aluminium-styrofoam sandwich)
Rails milled out of 15mm PVC plates
Better studies for further pixel detector installation.
Corapan rail cassette top lid and top rails not shown

15. New wheelset for next shutdown
New detector top wheel
New detector bottom wheel
exchangeable
spacer
exchangeable
spacer
Old detector top wheel
Old detector bottom wheel

16. Summary Very low mass mechanics for new 4 layer BPIX looks feasable
Outer layer 4 has stiffness, layer 1,2 & 3 in very low mass construction
Long pigtail modules & ultra low mass construction with CO2 cooling should give large factors in material budget.
Impact parameter term due to multiple scattering in FPIX region (h =1.5–2.3) should reduce substantial
New BPIX layout with one module type only  # faces = multiple of 4
Layer 1 radius reduces from 44mm  39mm
Future BPIX wheelsets adjustable  adapt to real beampipe position
Workout detailed design of new BPIX mechanics and fabricate in 3D stereo lithography model inclusive new supply tubes  insertion tests, clearances !
Cassette with rails for pixel-insertion tests design completed → fabrication