SLHC Pixel Local Supports Based on Thermally Conducting Carbon Foam

1. SLHC Pixel Local Supports Based on Thermally Conducting Carbon Foam E. Anderssen, M. Cepeda, S. Dardin, M. Garcia-Sciveres, M. Gilchriese, N. Hartman and R. Post LBNL W. Miller and W. Miller iTi Henry Lubatti, Gordon Watts, Tianchi Zhao, Dept. of Physics Colin Daly, Bill Kuykendall, Dept. of Mech. Engr. University of Washington May 29, 2008 CERN

2. Outline • Concepts • Examples of implementation • Prototype fabrication and tests • Foam materials testing • Mechanical and thermal modeling • Foam development plans • Design optimization plans • Prototype fabrication plans • Conclusions

3. Concept Overview • Thermally conducting, low-density carbon foam as • Structural material and simultaneously • For conduction of heat to cooling tube(s) • Same concept for barrel and disk local supports • Implementation can differ for inner barrel elements, outer barrel elements and disks but keep basic concept same Foam

4. Outer Layers - Example • “Large” area planar sensors. Conservative module design (similar to current) Module on back 38.4 26.8 34.8 … 986mm CARBON FOAM

5. Inner Layers - Examples • Monolithic structures • R  4 cm only • Modules one side • Modules alternate sides • Single-sided staves • R  4 cm • R  10 cm • Single-chip modules(e.g. 3D) Potential cable location

6. Disks • Layout with radial and  overlap in progress – not trivial • Modules on both sides of structure as now • Radial overlap requires offset in Z Back modules Module offset in Z Front modules

7. 1st Pixel Prototype “Stave” Tube with CGL7018 YSH-70 and K13D2U glued to foam Tube in foam with CGL7018 Allcomp 1 foam VG 7

8. LBNL Thermal Test Set-Up Silicon heater VG 8

9. Thermal Results T does not depend strongly on facing thickness Note double - side heat not 2 x single – side heating

10. FEA Model Heater heat loads, 8.38W Silicon heater, 148 W/mK, 0.28mm thick Silicon heater adhesive, SE4445, 0.6 W/mK, 0.004in thick, two places YSH70 open cloth fabric, one layer, 0.6 W/mK, 0.14mm YSH70 adhesive, 1.55 W/mK, 0.002in Foam properties varied, from 6 to 30 W/mK Al cooling tube, 180 W/mK, 2.8mm OD and 2.19mm ID Water, convective film coefficient, 66,000 W/m2K, 1.0L/min Set 20.25ºC on inner tube wall K13D2U facing, 1 W/mK, 0.28mm thick K13D2U adhesive, 1.55 W/mK, 0.002in thick VG 10

11. FEA Thermal Solutions Double heater Single heater Agrees with direct measurement of foam(K = 5.8) within understanding of component K values

12. Additional Prototypes • Identical width, thickness and adhesives to older prototype (Allcomp 1) but shorter in length (7.4 cm). • YSH-70 facings on both sides. • Heater only on one side. Compare at 0.63 W/cm2 • IR and water flow same as older prototoype ( 1.0 l/min)

13. Thermal Results • First results quite encouraging • Work with companies to up K and keep  low • SBIR with Allcomp just starting • Koppers making samples with goal of   0.10 • POCO already there at sample basis but fragile Note that production batch e.g. Koppers is 150,000 – 200,000 cm3. An outer stave is 125-250 cm3 (depends on coolant, width) Single-sided W B-layer and L1 – recent cooling tests Present detector -10C power off

14. Foam Materials Testing • Done at U. of Washington • Preliminary results • Additional tests with bonded facings to be done at U. Washington and Allcomp • Practical note – Allcomp foam easier to handle, machine

15. Thermal Modeling • Structure models – fix tube wall T • Thermal runaway – just started • Example of outer stave concept • T depends on foam K H=6000W/m2K (CO2) T(fluid)=-34ºC @ inlet Coolant film ΔT=3ºC Detector peak ~ -24.7ºC

16. Thermal Runaway • Estimates of sensor heating (too simple, must be updated) • Part of optimization….see later Foam K=6 W/mK W/cm2 vs temperature Assumes 280 micron fully depleted silicon operating at 600V….too simplistic Note 3D sensors @100V more like “16 cm” column

17. 10 5 0 -5 -10 Peak Sensor Temperature-(C) -15 -20 baseline foam 6 W/mK -25 foam=15W/mK foam=15W/mK, CC=250/25/250 -30 foam=15W/mK, Cable=200W/mK -35 -35 -30 -25 -20 -15 -10 -5 0 Coolant Tube Inner Wall Temperature-(C) More Thermal • Outer stave • Variations – see plot • Note that these results also apply to single-chip wide stave • Needs detailed optimization • Monolithic designs • Not as well studied • Depends on number of tubes • For one tube per module about same as stave • For fewer….need colder 0.6 W/cm2 Differential from sensor to coolant wall is 10.6˚C

18. “Disk” Model • Single tube per 4-chip module – interest in differences, will do 2 tubes later • Issue is addition of step of foam Flex circuit Epoxy Sensor Chips Flex circuit Sensor Foam Carbon fiber Chips Foam Kapton cable and glue layers – not present in disk but for comparison with stave

19. “Disk” Model Thermal Results • Remember single tube • Tmax (no sensor heating) • Difference in T for module on step is small  1C or less => foam step is viable option for disks. Cable layer removed. Foam has k = 6 W/mK. Peak temperature is 21.5 C above the coolant.

20. Mechanical Analysis Examples All very preliminary. Needs much more work along with support structure design Gravity sag < few microns for rigid 5-point support Gravity sag <5 microns Thermal distortion < 10 microns Thermal distortion  50 microns

21. Foam Development Allcomp foam • Note that Allcomp foam is different than graphite foams from POCO or Koppers • POCO and Koppers interested, Koppers making low density samples for us to test • Allcomp foam uses RVC (reticulated vitreous carbon) foam as base and adds high thermal conductivity material to ligaments in the RVC foam • Allcomp has just received special funding to develop foam for HEP application • Make and test samples of different density, porosity, heat treatment, etc • Make stave-like test structures and measure mechanical & thermal performance 3in by 6in by 2in thickness block 100 ppi and 0.12 g/cc

22. Design Optimization • In the next few months we want to explore quickly a wide range of design options based on foam concept • Meet thermal requirements(based on sensor heating update to appear soon). Calculate thermal runaway (obviously depends on coolant assumed) • Some mechanical input(for material estimates) • Minimize material • Span many (all?) options • Tube types – Aluminum, carbon fiber, stainless, CuNi – and number of tubes per module(1 every 2 cm width or can we do better..) • Facing materials – none (just glue), fiber, carbon-carbon, TPG, diamond • Foam combinations • All one density and K • Mix low density and higher density • Overall design optimum(or optima) for different regions(inner, outer, disk)

23. Prototype Fabrication • Follows design optimization • Also depends on choice of coolant and when choice is made • Coolant path • Choice of coolant is critical • Prototype “stave” sent to CPPM for tests • Hope to establish CO2 capability in US relatively soon • Continue to make very small prototypes for foam characterization • Number and type of small prototypes depends on design optimization studies – what makes sense • Ambitious goal would be to build full-length prototype outer stave by early 2009 based on design and small prototype studies.

24. Conclusion • Local supports based on thermally conducting carbon foam continues to look like good idea • Two immediate next steps • Design optimization, for which a critical assumption is coolant type • Continue and expand foam development • Very small and small prototype development (limited mostly by resources) • Goal would be to build full-length outer stave prototype for thermal and mechanical tests by early 2009. Combine with electrical? • Note – have ignored implications of B-layer replacement pending Task Force Report.