1. Saga of the IBL Staves
Franck Cadoux on behalf of the ATLAS IBL engineering team (and Eric Vigeolas in particular)

2. Saga of the IBL Staves Topics to be discussed
IBL project & its challenges
Stave design and its history…
Stave manufacturing & Testing
From a bare object up to integration
What we’ve learnt…(still learning!)

3. Saga of the IBL Staves IBL project & its challenges
Beam pipe
Current PIXEL
detector
IBL location
(envelope in blue)
PIXEL after de CERN

4. Saga of the IBL Staves IBL project & its challenges
IBL project is really short in time (driven by LS1)
Beam pipe is now part of the IBL
Envelopes are tight ( ID=56mm < IBL < OD=85mm…see next!)
Tricky operations in the pit (insertion thru 7m long pipe called IST)
14 Staves (detectors) -40°C with an evaporative CO2 system
IST (ID85mm)
IPT (ID58mm)

5. Saga of the IBL Staves IBL project & its challenges
IBL overview
14 Staves (or Local support) arranged cylindrically around the IPT
(one of the two key structures, or Global supports)
The IST (or IBL Support Tube) is a 6.6m long cylinder tied to the PIXEL
The IPT will position the Staves and support their services
IST cutout
(to look at the IBL package)
IPT with services

6. Saga of the IBL Staves IBL project & its challenges
IST and IPT manufacturing challenges
IST and IPT manufacturing (both carried out in Seatlle)
Material is a prepreg of K13C (same as for Staves!)
Driven by weight reduction (extremely rigid CFRP… fiber around 900 Gpa)
IST is 0.45mm thick, 6600mm long, 5 segments jointed in a second step
IPT is 0.45mm thick, except in its central area (Staves)… 0.325mm thick!!
IST prototype segment
IPT proto assembly
with rings

7. Saga of the IBL Staves Stave design and its history
Main design requirements (Stave)
As usual the outstanding features are: Lightweight(X0), Stiffness, Stability
Support 2 types of modules to be cooled down to -40°C all way long (650mm)
Stave fixation to “Global structure” driven by the IBL insertion into the pit!
Radiation hardness for every material (350 MRad at maximum)
Overall Stave planarity should be within +/- 150 µm (see later…)
Cable bus (flex) bonded to Stave due to tight envelopes
Stave
IPT

8. Saga of the IBL Staves Stave design and its history
IBL Stave evolution over the last 4 years (coordinated by CPPM Marseille)
Based on the PIXEL experience, several concepts have been studied…
… on CFRP type for omega shape (M60 vs K13C), carbon foam (Poco vs K9),
cooling pipe (CFRP vs Titanium) and the stave shape!
Everything led by the material optimization, reliability… and manufacturing

9. Saga of the IBL Staves Stave design and its history
IBL Stave Design and details…
A bare stave (w/o module) is 748 mm long
3.5mm thick, and weighs about 26 g
Made of 12 parts glued together
K9 foam choice after LBNL investigations:
Low density (0.22 g/cm3)… but good Thermal conductivity (40 W/m.K)
Stave end parts made of peek CF (inspired by PIXEL staves…)
CFRP Face plate inserted between foam and Module
Prevent TH grease penetration, increase the stiffness,
and allow for HV protection (parylene coating)

10. Saga of the IBL Staves Stave design and its history
Some details on design…
Developed by Wuppertal, gluing tests
on 2 samples (between Ti pipe and foam)…
Clearly shows glue penetration issues
This led to some new ideas (face plate in K13C/RS3)… thanks to developments by SLAC + Seattle (avoid the grease underneath module to be soaked up by carbon foam)
Short length proto by SLAC UniGe)
Layup of K13C facings
(Omega and face plate)
[0°/90°/0°]
Overall thickness: 195µm (quite thin)
K9 CNC
machined
Tomography of K9
K9 plates from
Allcomp

11. Saga of the IBL Staves Stave design and its history
Some details on design…
Thermal Grease is scraped over the module surface by means of mask and centering tools (see next)
Tested without the face plate (grease tends to be soaked up or diffused into the foam pores)
Grease being applied onto the Stave face plate
+ scraping over the mask…
All those testes performed on prototypes led to the validation of the STAVE before mass production
Result of thermal grease “footprint” when mask is taken out
(in this way, the grease amount is well known)

12. Saga of the IBL Staves Stave manufacturing & Testing
Manufacturing was done in Germany (led by Wuppertal with IVW)…
An initial target of 32 bare Staves + 10 protos to be manufactured
(a bit less to be loaded at the end of the history)
Based on the PIXEL Stave experience (molds, counter molds, CNC machining)
Graphite material used for molds …
…due to high temperature curing
Co curing was abandoned (material saving OK, but
delimitation still an issue… further developments
needed!
Such a work (12 pieces to be assembled)
is long process and difficult for mass prod.
Remachining of foam
Tomography
of first proto
PIXEL shape legacy
Now it’s a V-shape due to Flex bonding
CFRP wrapping
@ 12 bars pressure
CFRP Omega at 195µm
(good homogeneity)

13. Saga of the IBL Staves Stave manufacturing & Testing
Main steps of the Stave manufacturing….
K13C/RS3 prepreg unrolling
(for Omega + face plate shaping)
K9 foam machining
(6 blocks per stave)
End blocks machining (peek CF)
Stave is complete
12 steps are needed to complete 1 bare Stave (post machining required some fine tuning…)

14. Saga of the IBL Staves Stave manufacturing & Testing
First lessons from the Stave “pre production” step
(improvements on fabrication process)
Strip on cooling pipes found on 2 staves  vacuum bag removal during stave gluing process was suspected
First staves prototypes showed cracks on Omega  Machining process was changed successfully … no crack observed afterwards …

15. Saga of the IBL Staves Stave manufacturing & Testing
Thermal qualification (on “Stavelet” + Stave full length proto)
Several dummy staves were tested to select the best design (thermal grease, glue…)
2 final staves equipped with Si heaters + CO2 cooling
TFOM (Thermal Figure Of Merit) < 15°C.cm2/W
(30°C.cm2/W is the maximum)
350 thermal cycles [-30°C; +40°C], 50 cycles [-40°C; +50°C],
10 pressure cycles [1;66 bars] and pressure shock up to
150 bars! No TFOM change has been seen!
Si heaters + thermal sensor
(over full length)

16. Saga of the IBL Staves Stave manufacturing & Testing
Some metrology results…
An extensive campaign of metrology was done to record any change in planarity before and after thermal cycling (with and w/o Flex glued to the Stave)
After Stave Module loading, thermal cycling is performed systematically to select things… so far, the deformations are close to the limits, but still OK!
Metrology at UniGe
Staves with
modules

17. Saga of the IBL Staves Stave manufacturing & Testing
Some detailed FEA were done to “help” designing the Staves
The policy was to get several lab working on Stave FEA to X-Check results (CPPM, LAPP, CERN, INFN Milano, UniGe)
Both mechanical and Thermo mechanical FEA have been carried out (ANSYS, Abaqus)
Tests on prototypes to get to the “MODEL calibration”…
Flex
Extensive FEA’s to validate the choice of
the Face plate option (1 ply, 3 plies, a few cut out
at module location…).
For ∆T= -60°C, the ∆Zmax =15 µm… instead of
65 µm w/o face plate!
No measurement of TH deflection has been done on proto
Flex

18. Saga of the IBL Staves Stave manufacturing & Testing
Comparison between Test and FEA (mechanics, simply loaded stave)
Stave is held by its handling frame (used from early step to final integration)
A concentrated loading is done at the ¼ of stave length (see below)
Stave with Flex
weights
Stave onto the handling frame: “final” boundary conditions …
Tends to lift up slightly
loading
Better than 15 % difference

19. Saga of the IBL Staves From a bare object to Integration
The first phase is about “Module Loading” onto the stave…
Aluminum jigs have been designed and successfully tested on the first protos
Every step of the process is safely recorded in a Data Base (useful in case of pb)
Precision is given by the jig thru the Handling frame
Loading jig
(main tool)
Stave on its handling frame

20. Saga of the IBL Staves From a bare object to Integration
The main steps of the loading process…
Now ready for final QA (electrical tests, thermal cycling, metrology…)
Repair on module is still doable… but risky!

21. Saga of the IBL Staves From a bare object to Integration
Integration onto the CERN (building SR1)
Pretty long object (the cooling line brazing is done before integration)… 7m long!
A dedicated Integration Stand is under fabrication (UniGe is responsible)…
sort of multi purpose object to …Integrate, store, insert thru the IST the IBL package
Brazing technique under CERN
+ Brazing Stand
The Integration stand
Multipurpose container (MPC) + Loading stand (central area)

22. Saga of the IBL Staves From a bare object to Integration
Integration onto the CERN (building SR1)
Stave are assembled first, then the services are connected …and tested!
The challenge is to insert a stave with very close neighbors (< 0.9mm clearance… so envelope check will be an issue!
Loading stand
IBL _ MPC
(6.6 m long)
Envelope checks
IPT
Stave Handling
frame
Loading stand
IPT

23. Saga of the IBL Staves What we’ve learnt…
Over the 4 years of manufacturing…
Stave manufacturing is a lengthy operation difficult to “duplicate” among institutes
(tooling, jigs, know how…)… so to be thought about for the next Upgrades!
Material procurement was always tricky (K13C, foam, pipe…)…even if for the layup we took advantage of the IST-IPT business!
So many pieces to glue together… but at the end, the result is pretty satisfactory (planarity, rigidity… and close to FEA predictions!).
Main drawback is about the brittleness of the Omega + Face plate (due to very high modulus fibers)… special care applied to the post machining
Towards the next years…
Still some challenges to be faced on Stave Integration (envelope issues)
About K13C layup…is it really needed ?? Seems to be “too much”…
Think about even thinner cooling pipe, and smaller diameters?? To save further material…
Try to optimize the amount of glue… especially at cooling line joint
… but the feeling that we are close to some current limits / mechanics…(material, glues, ?)
Optimize the links (number of fixations) to the Global structures (like IST) is challenging