1. Summary of activities for LHC-b vacuum chamber supports
L. Leduc, J. Chauré, M. Gallilee, C. Garion, R. Veness

2. OUTLINE Current layout
Material selection criteria – Optimization for transparency
New support system proposal
Testing
Safety

3. CURRENT LAYOUT LhCb current layout: 8 stainless steel rods
8 stainless steel cables
2 aluminium collars
2 vespel rings
The support system is a source of background signal
Need to optimize -> the materials involved
-> the geometry

4. Polymer based materials Carbon fiber reinforced epoxy λ= 230 mm
NEW MATERIALS
Criteria for selection:
1. Provide acceptable mechanical properties;
2. Improved radiation length.
Metallic materials
Polymer based materials
Stainless steel λ= 17.6 mm
Titanium λ= 35.6 mm
Aluminum λ= 70 mm
Beryllium λ= 354 mm
Carbon fiber reinforced epoxy λ= 230 mm
Kevlar λ= 280 mm
Epoxy λ= 352 mm

5. COLLARS Current design aluminum + stainless steel screws New design
Design described in EDMS n°
Current design
aluminum + stainless steel screws
New design
Beryllium instrumental grade I 220 H
S2F
S3F
Current Volume (105mm3)
1.47
7.35
New Volume (105mm3)
0.77
2.90
Volume reduction
47%
60%

6. WIRE SYSTEM Constraints on the design:
axial force F when the chamber is evacuated
stiffness : the axial displacement should be limited
-> axial stiffness should be high enough
Current solution:
8mm diameter stainless steel rods
3mm stainless steel wires F

7. WIRE SYSTEM 2 solutions described on EDMS n° 1177138 1st solution:
Flexible cables to be replaced by Vectran/Technora ropes
Rigid rods replaced by carbon fiber reinforced epoxy tubes
Spliced eye and vespel ring termination
2nd (backup) solution:
Aluminium tubes and rods

8. COMPARISON OF SOLUTIONS
Performance of both solutions
Radiation length λ (mm)
Gain in transparency
Stress safety factor
(termination)
Current supports
Rods
cables
17.6
Solution 1
CFRP tubes
ropes
230
>289
93%
90%
2.9
>>
Solution 2
Aluminum tubes 70
73%
40%
2.4
2.0
→ Much lighter solutions while keeping acceptable mechanical properties

9. INTERFACE RING Current solution:
Material : graphite reinforced Vespel (polyimide )
Aluminum ring for bake out
New solution
Material: Celazole [C20H12N4]
Could be used during bakeout
Comparison of material properties
Tensile strength
(MPa) at room temperature
Tensile Strength (MPa) at 250°C
Compression strength (MPa) at room temperature
Compression strength (MPa)
At 250 °C
Celazole
160
117
390
172
Vespel SP 21 66 38

10. INTERFACE RING Volume optimization Reduced thickness of the ring
Reduced number of fasteners
Material optimization
Currently stainless steel fasteners
New solution ->Titanium fasteners
Celazole is more transparent than Vespel
Volume Optimization
S2F
Fasteners
I Ring
75%
55%
S3F
62%
32%
Radiation length (mm)
Current support
Fasteners
I Ring
17.6
275
New supports
35.6
325

11. TESTS Radiation testing organized by G. Spiezia (RP):
LHCb calculated dose over 20 running years: 2MGy
Materials: Celazole , Vectran & technora ropes, carbon tubes
9 dose steps: 0-> 10 Mgy at dose rate of 70 kGy/h
one additional step at 1 kGy/h to 500kGy -> to assess dose rate effects
Required information: strength and stiffness
Results
technora ropes are validated against radiation
Tested in building 113 in February 2012 (S. Dos Santos, G.Chauré, H.Kos)
Vectran solution is discarded

12. TESTS
Results technora ropes

13. TESTS Celazole samples are validated against radiation
Tested in the mechanical lab (A. Gerardin)
Chemical analysis EDMS n° (EM Lungulescu)
No combined effect of radiation and temperature (Suisse technology partners)

14. UPCOMING TESTS Radiation testing of carbon fiber solution
irradiated samples sent to MECASEM
Creep tests:
Synthetic ropes, CFRP tubes (glue)
Possibility of accelerating creep rate by increasing temperature -> life time
tests organized at CERN in the mechanical measurement lab (M. Guinchard)
Chemical analysis of Technora
Temperature testing of Celazole
impact on Tg of several bakeout cycles
Assembly tests
Aluminum prototypes
for collar and interface ring
Mock up of the chamber
Wire system with a scale 1:3

15. SAFETY ASPECTS
discussion with J. Gulley, P. Silva and D.D Phan from safety
Use of Beryllium
documented in EDMS n°
procedure of the assembly
risk assessment (drop or scratch of the item, …)
procedure in case of hazards
ex: scratch of a piece
→ stop the handling
→ dismanteling
→ use of a glove box
Use of synthetic ropes
Safety team want to be present for the mockup tests

16. Safety has been carefully considered in the design
CONCLUSIONS
The proposed system is lighter than the current one: from 90% (wire) to 65% (fasteners)
Safety has been carefully considered in the design
Back up solutions are proposed, that are lighter than the current system
ACKNOWLEDGEMENTS
M. Guinchard, H. Rambeau, H. Kos, P. Coly, P. Lepeule, C. Loureaux, G. Foffano, S. Clément, G. Kirby, J. Gulley, P. Silva, D.D Phan, G. Spiezia.