VELO Module Kickoff Summary

Richard Plackett – VELO Pixel Chip MeetingCERN, 13th November 09

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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

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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

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PumpHeat exchanger

Flooded evaporator

Restriction

2-Phase Accumulator

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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

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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

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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.

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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

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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

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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

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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

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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

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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

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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

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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…