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NA62 Gigatracker cooling requirements. Gigatracker (GTK) modules will operate in vacuum and under high radiation Module has to be replaced on a regular basis Cooling system required to avoid performance loss The operation temperature for the frontend electronics will be 5°C or lower
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NA62 Gigatracker cooling requirements • Gigatracker (GTK) modules will operate in vacuum and under high radiation • Module has to be replaced on a regular basis • Cooling system required to avoid performance loss • The operation temperature for the frontend electronics will be 5°C or lower • Low material budget for the cooling system
Gigatracker Module support and alignement structure Cooling plate Readout chip (12 x 20 mm), heat production ca. 3.2W per chip (2 W/cm2) beam direction Sensor, silicon pixels (30 x 60 mm) 3D schematic drawing of the GTK module
Materials in the sensor area The total material budget (material in the beam) allowed for the GTK module is 0.5% X0(radiation length).
Our proposal: Microchannel cooling • Goals ofdevelopment: • Integration ofmicrochannelsintofrontendelectronics • Cooling via an separate coolingplatewithmicrochannels • 150mm thickness • 300mm thickness • Benefits: • Uniform temperaturedistribution in theareatobecooled • Small DT betweencoolantandreadoutchip => reduced thermal stress • Single-phaseandtwo-phasecoolingpossible • Technology studiedat EPFL with strong supportofindustrialpartners • Mutual understandingtoshareknowledge (EPFL <> CERN) • Specifityofourapplication: • Verylow material budget • Low heatflux
Tentative layoutofmicrochannelsfortheGigatracker • area to be cooled ~30 x 60mm • channel length ~40mm • channel cross section 50mm x 50mm • separation walls 25mm thick • heat flux in the cooling region 2W/cm2 • Support and Connection of services outside the sensor area and on one side • Single-phase cooling • Open pointsforthe prototype: • Thermal connectionofthereadoutchiptothecoolingplate • Total pressure in thechannels
Production priciples • Micro channels etched in thin wafer • Cover wafer is bonded to channels • Cover contains holes for inlet and outlet • Cover wafer will be thined by etching in the critical beam area
C6F14 cooling liquid of choice • radiationhard • thermallyandchemicallystable • nonflammable, nontoxic, nonconducting • knownandusedat CERN (CMS and Atlas Tracker) • used in liquid phase • C3F8is an option in caseoftohighpressure in thecoolingplatefor C6F14
Fluid temperature difference 12bar pressure drop 2bar pressure drop • Temperature difference between inlet and outlet for channels of 50mm x 50mm
CFD model – boundary conditions Coolingplate fixedtemperatureatthebackside Readoutchip 2 W/cm2, 12 x 20 mm Sensor, siliconpixels 30 x 60 mm • all remaining walls are considered adiabatic, since the GTK will operate in vacuum • heat source is the volume of the readout chip
Temperaturedistributionl=70W/mK Heat transfer coefficient between chips and cooling plate of l=70W/mK, for a material thickness of 25 mm
Temperaturedistributionl=7W/mK Heat transfer coefficient between chips and cooling plate of l=7W/mK, for a material thickness of 25 mm
Temperaturedistributionl=0.7W/mK Heat transfer coefficient between chips and cooling plate of l=0.7W/mK, for a material thickness of 25 mm
Plans for the next months September: • production of a prototype at the EPFL clean room • preparation teststand (cooling unit, instrumention …) • design of connecting component • further development of the CFD-Model Oktober/November: • commissioning teststand • first test at room temperature • preparation of test at cold temperature, cryostat • assembly prototype and mockup chips Thermal interface to be designed according to chip design and fabrication!!!