VELO Module Kickoff Summary Richard Plackett – VELO Pixel Chip Meeting CERN, 13th November 09

-2-Overview Cooling System Module Cooling Interface Thermal Supports RF Foil Module Geometry Module Distribution Sensor Technology TSVs Hybridisation Timeline / 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 Condenser Pump Heat exchanger Flooded evaporator Restriction 2-Phase Accumulator Heat in Heat out Freon system

-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 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…