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VELO Module Kickoff Summary
Richard Plackett – VELO Pixel Chip MeetingCERN, 13th November 09
-2-
Overview
Cooling System Module Cooling InterfaceThermal SupportsRF FoilModule GeometryModule DistributionSensor TechnologyTSVsHybridisationTimeline / Planning
A wide ranging discussion was held on a number of topics, technical, and otherwise
Due to time constraints we failed to discuss infrastructure and testing, or have any meaningful discussion about interconnects
-3-
Cooling
• Martin presented the current CO2 cooling system and explained with small modifications its power could be increased substantially if necessary
• Currently could supply 4 watts per chip, could go up to ~10 (although this would be a very bad idea)
• Marina showed some development work done for the BTev LN2 cooling project
Con
dens
er
PumpHeat exchanger
Flooded evaporator
Restriction
2-Phase Accumulator
He
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in
He
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in
He
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Fre
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stem
-4-
Cooling Interface
• The method of connecting to the modules was discussed, if connections to modules permanent then difficult to handle
• Currently cooling ‘cookies’ are welded to cooling system and clamped to modules, welding modules to long cooling pipes would make testing and assembly harder
-5-
Module Cooling Models
Jan presented ANSYS simulations showing it was better to cool from just the sides than just the back of the U shaped module
9 degrees C 4 degrees C
-6-
Module Support
• pCVD diamond presented by Jan – provides a vacuum compatible, low mass substrate with high thermal conductivity
• SiC foam Presented by Jaap – open foam through which some cooling fluid could pass with extremely low radiation length.
• Although foam might not replace diamond, could be used to mount two modules and increase rigidity and ease of handling. Need to test vacuum compatibility.
-7-
Module Geometry
• There were 3 ideas considered• ‘U’ shape - current straw man, closest to current VELO• ‘L’ shape - minimises distance around beam• ‘Angel of Amsterdam’ – angled planes maximise
resolution
-8-
Module Distribution
• Marco presented simulations of various module distributions and RF foil shapes. The 18-30 option lets us put layers of foam between two conventional modules
-9-
RF Foil
• Marina presented exploratory work with CMA (who made the RICH1 spherical mirrors) to make a coated carbon fiber RF shield
• This needs to be tested wit the coating to make sure its vacuum compatible
-10-
Sensor Technology
• The three usual suspects, planar silicon, double sided 3D silicon and Diamond
• Chris presented 3D
• Guianluigi (Liverpool) presented Planar with a variable guard ring
• Marina presented diamonds
-11-
TSVs
• Ronan McNulty (UCD) and I presented about our institutes work producing test vehicles for TSV development
• This is really quite critical for 4 side tiling of the chips
• Without it we have to go to a double sided module with worse radiation length due to overlaps
• CERN (Sami and Timo) have 10 completed test vehicle wafers at VTT
• UCD are working with Tyndal National Institute in Cork and have just put in an application
-12-
Hybridisation
• Chris presented explorations of Benzocyclobutene (BCB) deposited layers to produce a multilayer PCB effect on the sensor and be able to remove the hybrid substrate altogether
• Also presented some backthinning work
Sensor with meshed GND plane
Strip pad connections
-13-
Timeline
• Disagreement over how long it would take us to build the upgraded detector
• Agreed it needs to be as parallel as possible
• Can chip development go ahead before sensor choice is made?
• Things will not be included if there is not someone championing them
-14-
Summary
• Difficult to summarise a summary without removing all the information….
• We didn’t really decide much but did at least air all the ideas and start to get an idea of whats on the table…
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