Velo Module 0 minus minus Paula Collins. Investigating Module 0 thermal performance Baseline module...
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Transcript of Velo Module 0 minus minus Paula Collins. Investigating Module 0 thermal performance Baseline module...
Velo Module 0 minus minus
Paula Collins
Investigating Module 0 thermal performance
Baseline module design combines elements of different CTE (and Young’s Modulus)
Can the elements stand the strain? What about the bump bonds? What about repeated thermal cycling (-40 →+20 oC)?
Is the thermal performance in vacuum as expected?
Different approaches are possible to optimise (flexible glue, splitting silicon into smaller pieces)
Kapton: 30-80 10-6 C-1
Silicon: 2.8 10-6 C-1
Diamond: 1.5 10-6 C-1
Thermal Performance and Simulation
Power consumption varies as a function of lifetime
~ constant in chips: 0.5-? W/cm2
Silicon rises to ~0.3-0.5 W/cm2 in the part most remote from the cooling
See presentations of Steve Blusk and Brian Maynard from upgrade meetings for more details
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
0 10 20 30 40 50Distance from beam (mm)
Po
we
r/A
rea
(W
/cm
2 ) at -25 C
at -15 C
at 0 C
Chip power W/cm2
Ultimately the cooling attachment will be a huge challenge
Second stage of mechanical tests would be to investigate different methods of cooling pipe attachment
Could be clamped between additional diamond pieces
Or could go for ATLAS style approach: use RVC foams to couple round metallic tube to rest of structure
Use of small glass capillaries has been suggested by Nikhef
2 diamond piecesEnclose in CF frameCooling pipe around the edgeOrOne TPG core large hybrid?
Bus cable
Hybrids Coolant tube structure
Carbon honeycomb or foam
Carbon fiberfacingReadout
IC’s
Silicon sensors
Properties of Thermal GreaseExtensively studied for ATLAS and CMS upgrade (both strips and pixels)• >8 different compounds tried by ATLAS (dow corning, wlpg, cgl 7018 etc.• http://cdsweb.cern.ch/record/1238166/files/ATL-UPGRADE-PUB-2010-0
02.pdf• Example candidate for foam development is Allcomp, Inc but lots of R&D
even for non vacuum environments – lowering density of graphitic foams, increasing density of RVC foams etc. etc.
• No need to reinvent the wheel, but have to try things out in our scenario…
Some strain could be taken up in the glue
“Fluid Glues” exist and can be tried:• Dow Corning 734RTV (tens. strength= 16 Kg/cm2, 321%
elongation, CTE~300 10-6 C-1, er~2.5, dielectric rigidity~18KV/mm
• Epotek 353ND (flex. strength= 750 Kg/cm2, CTE=56 10-6 C-
1, viscosity = 2000 cps)
Other things to watch for: radiation resistance, outgassing properties, thermal conductivity
In view of the cost of the diamond.. Dismountable tests?
Maybe a hard glue needed for a one sided firm connection e.g. cyanoacrilate.
CERN interestWe are interested in procuring piece(s) of diamond from Diamond Materials and testing various aspects of the module 0 construction.
The initial try for the shape would be the rectangular 3x2 chip piece, plus a margin on 3 sides to allow for potential cooling pipe attachment
Initial thickness: 200 micron
Interest in mechanical and electrical tests7
Vacuum test stand developmentRaphael Dumps
Vacuum test stand essential for LHCb (and possibly other groups)
Design is in progress• Incorporate germanium window
and camera• Position measurements• Peltier cooling• High speed feedthroughs• Inerchangeable flanges for testing
different modules
8
Mechanical testsVerify planarity and surface roughness of diamond• Use of scanning EM at CERN metrology department
Populate with 6 pieces of silicon and heater chips (total thickness 300 micron), and temperature measuring sensors
First cooling try to tie back edge and sides to a plate of fixed temperature
Later can try various methods of attaching cooling pipes and mount in vacuum tank
Heat with various powers, and cooling temperatures and compare the temperatures achieved with the thermal simulations
Practice measurements of temperature with the thermal camera and deflection
Thermally cycle and check for damage
If severe deflections are seen, we possibly can try to attack this with structuring the diamond (e.g. grooves)• CERN has measurement devices for cryogenic tensile testing
9
Stage 0 minus one test300 um thick silicon piece glued onto diamond and instrumented with smd components to allow uniform and non uniform heating
Glued to diamond cooling plane
Loosely clamped with a lot of thermal grease to Peltier cooled heatsink
Possibility to mount assembly inside vacuum tank
Electrical testsOne piece of diamond to be instrumented as a timepix readout
See if a standard timepix planar silicon assembly can be read out via diamond metallisation lines
Check on issues such as metal deposition, reliable attachment of connectors, bonding issues, and thermal interface
To be done in collaboration with CERN PCB workshop
Device can go to testbeam and also be irradiated
First step will be to thermally cycle and check bump bond integrity
11LHCb VELO Upgrade MeetingApril 14th 2010 - Paula Collins
Irradiation tests (Phil, Jan, Maurice)
Diamond pieces are being irradiated
The evolution of the thermal conductivity will be checked
A number of samples will be irradiated in parallel and removed after a certain time
The performance will be calibrated against a non-irradiated piece
12LHCb VELO Upgrade MeetingApril 14th 2010 - Paula Collins