1. Micro-channel Cooling
P. Petagna
Acknowledging contributions from: A. Francescon; A. Mapelli; H. Michaud; M. Morel; J. Noel; G. Nuessle; G. Romagnoli
May 23rd, CSEM-CERN Meeting
P. Petagna: Micro-channel Cooling

2. Thermal Management of Tracking Detectors: Basics
Power densities involved ~ W/cm2
Large surfaces of silicon in tightly confined volumes
Total thermal dissipation up to few tens of kW
Detector layout packed and geometrically complex, thus only limited space is available for piping and connections.
In many cases, in order to preserve the silicon sensor from severe degradation caused by the high level of radiation, it is also necessary to operate and maintain the detectors at temperatures in the range -10 to -20 °C
Parameters to be minimized:
The amount of material crossed by particles;
The temperature difference between heat source and heat sink for a given quantity of heat to be removed;
The temperature gradients on the surface of the sensor
May 23rd, CSEM-CERN Meeting
P. Petagna: Micro-channel Cooling

3. Examples of Solutions Adopted in the Present LHC Detectors
ATLAS PIXEL
CMS TEC
Complex networks of mm-size metallic pipes brought in connection with the heat sources through customized low mass heat spreaders.
Small contact surfaces +
long chains of thermal resistances
temperature difference between the module surface and the coolant typically ranges between 15 and 25 °C for electronics power densities generally not exceeding 2 W/cm2.
CMS PIXEL
A. Andreazza – ATLAS Coll. “Status of the ATLAS Pixel Detector at the LHC and its performance after three years of operation”
NIMa,
CMS TIB
W. Erdmann - the CMS pixel group “The CMS pixel detector”, World Scientific Review Volume, 2009
May 23rd, CSEM-CERN Meeting
P. Petagna: Micro-channel Cooling

4. Example of material budget distribution for CMS PIX
Main Issues with Present “Standard” Solutions
Example of material budget distribution for CMS PIX
Impact of cooling material on detector’s material budget
Very low refrigerant temperature for cold sensor operation
Concentrated heat sink under the ASICS must indirectly keep the sensor cold
Small natural surface of thermal exchange
Large CTE mismatch between heat source and metal heat sink
May 23rd, CSEM-CERN Meeting
P. Petagna: Micro-channel Cooling

5. Detector Silicon Micro-channel Cooling: Concept
ORIGINAL CONCEPT (for high power IC):
Tuckerman, D.B., and Pease, R.F.W., “High Performance Heat Sink for VLSI,” IEEE Electron Dev. Lett., EDL-2, No. 5, 1981
May 23rd, CSEM-CERN Meeting
P. Petagna: Micro-channel Cooling

6. why? Advantages of Silicon Micro-channel Cooling
Silicon heat sink => Low mass
Distributed cooling in the substrate => Direct cooling both of ASICS and Sensor
Many parallel channels => Large heat exchange surface
Refrigerant flow distributed in small channels => High Heat Transfer Coefficient
No heat flows in the electronics/sensor plane => Small thermal gradients across the module
All material is silicon => No mechanical stress due to CTE mismatch
May 23rd, CSEM-CERN Meeting
P. Petagna: Micro-channel Cooling

7. NA62 GTK: First Application of Silicon Micro-channel Cooling
BEAM
Silicon m-fabricated
cooling device
Hydraulic optimization: EN/CV CFD team
Sensor and read-out chips
OPERATIONAL SPECS:
Detector surface: ~40 x 60 mm
Sensor surface: ~30 x 60 mm
Power dissipation (chips):
~4 W/cm2 on periphery
~0,5 W/cm2 under the sensor
Very high radiation level
Sensor T < 0 °C (as low as possible)
T uniformity on sensor: ±3 °C
Max cooling X-section in active area: eq. to 150 mm Si
Adopted solution
May 23rd, CSEM-CERN Meeting
P. Petagna: Micro-channel Cooling

8. NA62 GTK: Thermal and Mass Performance
150 parallel channels 70 x 200 mm
Deeper manifolds for DP reduction
Thickness in active area: 130 mm
Max thickness outside active: < 700 mm DT
sensitive area
Line1
Line2
Line3
DT = 0 °C
DT = 25 °C
48 W (~1.5 x nominal):
Min DT sensor – fluid = ~ 6 °C (center)
T uniformity on sensor = ±3 °C
DP (8 g/s -20 °C) = 8 bars
Tests under vacuum
May 23rd, CSEM-CERN Meeting
P. Petagna: Micro-channel Cooling

9. Other Examples of Application under Study
ALICE ITS
“Phase I” upgrade
Room Temperature
Two-phase refrigerant
Low pressure
Horizon 2015
20 °C
- 10 °C
0 power
1.5 W nominal
36 W
ATLAS Inner PIXEL
“Phase II” upgrade
Cold Temperature
Two-phase refrigerant
High pressure
Horizon 2018
May 23rd, CSEM-CERN Meeting
P. Petagna: Micro-channel Cooling

10. Directions for further Integration
Miniaturized reliable fluidic connections
Integrated front-back
electrical connections
May 23rd, CSEM-CERN Meeting
P. Petagna: Micro-channel Cooling

11. CERN-CSEM Collaboration
AGREEMENT KN2037/KT/PH/173C
Technical objectives of common interest
Matching of resources
Fixed (but realistic!) schedule
Protection of background IP
IP sharing of produced know-how
May 23rd, CSEM-CERN Meeting
P. Petagna: Micro-channel Cooling