na62 gigatracker cooling requirements
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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
Cooling plate
Readout chip(12 x 20 mm), heat production ca. 3.2W per chip (2 W/cm2)
Sensor, silicon pixels(30 x 60 mm)
3D schematic drawing of the GTK module
support and alignement structure
beam direction
Component Material Thickness [μm] X0 [%]
Sensor Si 200 0.21
Bump Bonds Pb-Sn ~25 0.001
Readout Chip Si 100 0.11
Cooling Plate Si ~150 ~0.15
Sum ~0.47
Materials in the sensor areaThe total material budget (material in the beam) allowed for the GTK module is 0.5% X0(radiation length).
Our proposal: Microchannel coolingGoals of development:1. Integration of micro channels into frontend electronics2. Cooling via an separate cooling plate with micro channels
a) 150m thicknessb) 300m thickness
Benefits:• Uniform temperature distribution in the area to be cooled• Small T between coolant and readout chip => reduced thermal stress• Single-phase and two-phase cooling possible• Technology studied at EPFL with strong support of industrial partners• Mutual understanding to share knowledge (EPFL <> CERN)
Specifity of our application:• Very low material budget• Low heat flux
Tentative layout of micro channels for the Gigatracker
• area to be cooled ~30 x 60mm• channel length ~40mm • channel cross section 50m x
50m• separation walls 25m 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 points for the prototype:•Thermal connection of the readout chip to the cooling plate •Total pressure in the channels
area to be cooled
Inlet manifold
Outlet manifold
silicon plate
silicon cover wh
Ll
hwLl
channel heightchannel widthhydraulic channel lenghtthermodynamic channel lenght
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
C6F14 @ -20°C H2O @ +20°C
Density kg/m3] 1785 998
Viscosity [10-7 m2/s] 8.2 10
Heat capacity cp [J/(kg K)] 976 4183
Thermal conductivity [10-2 W/(m K)] 6.2 60
• radiation hard• thermally and chemically stable• nonflammable, nontoxic, nonconducting• known and used at CERN (CMS and Atlas Tracker)• used in liquid phase• C3F8 is an option in case of to high pressure in the cooling plate for C6F14
Fluid temperature difference
Tf Tf
12bar pressure drop 2bar pressure drop
Temperature difference between inlet and outlet for channels of 50m x 50m
CFD model – boundary conditionsCooling platefixed temperature at the backside
Readout chip2 W/cm2, 12 x 20 mm
Sensor, silicon pixels30 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
Temperature distribution =70W/mK
Heat transfer coefficient between chips and cooling plate of =70W/mK, for a material thickness of 25 m
Temperature distribution =7W/mK
Heat transfer coefficient between chips and cooling plate of =7W/mK, for a material thickness of 25 m
Temperature distribution =0.7W/mK
Heat transfer coefficient between chips and cooling plate of =0.7W/mK, for a material thickness of 25 m
Plans for the next monthsSeptember:
• 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!!!