1. M. Gilchriese Update on Pixel Prototype Mechanics/Cooling Structures at LBNL February 1, 2008 M. Cepeda, S. Dardin, M. Garcia-Sciveres, M. Gilchriese and R. Post LBNL W. Miller and W. Miller iTi

2. M. Gilchriese 2 What Are We Doing? R&D on module supports using low-density, thermally conducting carbon foam + carbon fiber structures Goal is to investigate both stave-like(or sector-like) structures and monolithic ie. half-shell(or half-disk) structures Build and test prototypes and do FEA to compare to measurements and predict performance. Note all barrel concepts assume active edge modules!! Flat surfaces.. Today –Update of thermal measurements on stave structure –Comparison of these measurements to FEA –Monolithic structure mockup made –Next steps and conclusions

3. M. Gilchriese 3 Foam Currently working with foam made by proprietary chemical- vapor-deposition (CVD) process using reticulated vitreous carbon (RVC) foam as a precursor The RVC has density ~ 0.05 g/cc and is poor thermal conductor with a K ~ 0.07 W/m-K The CVD-deposited carbon coats the ligaments in the RVC foam, has a very high K and thus raises the effective K by factor ~ 100 but the density only by factor 2-4. Note this foam (and RVC foam) is straightforward to machine, including moderately complex shapes and has reasonable mechanical properties eg. CTE similar to silicon So far we have worked with samples (free) of density 0.18 g/cc Made simple rectangular prototype – foam with tube in middle – to test concept

4. M. Gilchriese 4 Pixel Stave Prototype - I Foam with groove for tube. Three pieces joined. One side YSH-70 cloth 140 microns thick K13D2U laminate 300 microns thick

5. M. Gilchriese 5 Pixel Stave Prototype - II Tube with CGL7018 YSH-70 and K13D2U glued to foam Tube in foam with CGL7018

6. M. Gilchriese 6 Pixel Stave Prototype - III Final assembly(foam+fiber halves glued together around tube) Tube is sized for CO2 coolant ie. about 2.2mm ID Platinum-on-silicon heater in middle to simulate pixel module and copper-kapton heaters on either side to minimize end effects. 6.9 mm 24 mm Foam 260mg/cm 2 (exc. Pipe) => 130mg/cm 2 for Tube is 2.8mm OD

7. M. Gilchriese 7 Thermal Performance IR camera used Water coolant at 1.0 l/min at 20C. Vary power level in silicon heater And separately in copper-kapton LabelEmisBGAveSDMaxMinUnit A10.9519.027.410.6528.425.9C A20.9519.027.360.8028.423.8C T in boxes

8. M. Gilchriese 8 Results Note if CO2 used as coolant then reference temperature could be about -30C. Thus delta T of 10 => T of -20C. FE-I4 goal FE-I3 normal Max. spec  Includes sensors & power conv. But not cables.  

9. M. Gilchriese 9 FEA of Prototype Single-module in length, corresponding to silicon heater Heat from both sides Neglect kapton heaters on either side of silicon heater Instead have measured effect of additional heaters on the prototype Figure at right and summarized on next page

10. M. Gilchriese 10 FEA Comparison Measured  T for about 0.65W/cm 2 on both sides of stave is about 14.5C for either sided(very small difference between side with YSH-70 and K13D2U). Correction for kapton heaters is about -1C. So value to compare with FEA is about 13.5C FEA predicts 11-15C, taking into account errors in K and thickness of materials – see below. Biggest unknown is foam K.

11. M. Gilchriese 11 Improvements? We were conservative in the amount of foam (2mm) between the facing and tube. Subsequent machining trials show that we can reduce this to 0.5-1mm. Reducing to 1mm would reduce the  T by 1.5-2C (from calculation). The facing on the module side is there to (a) provide a surface to mount the module and (b) possibly for stiffness. We realized that at least (a) can be met with glue alone and this would also likely improve  T See samples with good surface quality that consist of Hysol 9396 + 30% boron-nitride(for thermal conductivity) about 125 microns thick. No facing on front side. See pictures next page. Would tune thickness and shape of backside carbon-fiber facing to provide required stiffness, if this technique were used.

12. M. Gilchriese 12 Glue Surface Samples

13. M. Gilchriese 13 Monolithic Concepts for B-Layer Single half-barrel structure Modules inside Drawings show concepts for CO2 cooling, but would just use bigger pipe for CnFm cooling Concept is simple –Conducting foam –Aluminum tube glued into foam –Tune carbon-fiber outer shell to minimize material but meet stiffness and other mechanical requirements –End-rings (not shown) for additional stiffness(glued to shell) and for inevitable cable and pipe strain relief Carbon high K foam Faces for module mounting Round aluminum tube Carbon fiber shell glued to foam

14. M. Gilchriese 14 Monolithic Mockup We have built a mockup of a monolithic foam-fiber structure(for SLHC B-layer with CO2 cooling) to understand how to do this. Used low-density RVC foam(not conducting foam) for convenience See next page for some pictures of details As built, about 1.7 g/cm for half-barrel(foam, tubes, adhesives, shell) => maybe 4 g/cm for real foam, real shell? Eg. 320 gm + end rings for 80 cm half-barrel Can easily see how to make mechanical/cooling structure to meet thermal/mechanical requirements. But mount and remove modules and connections? Needs considerable study – this is the hard part of this design

15. M. Gilchriese 15 Monolithic Construction

16. M. Gilchriese 16 Monolithic Options to Study Will do quick FEA look at alternative monolithic option proposed by Maurice One-module long model shown here. Mounting and connection access easier in this concept What K needed for foam to make this work with fewer tubes per module? Could keep one-tube per module, however Note in this case likely to need carbon fiber facings both sides for overall stiffness.

17. M. Gilchriese 17 Next Steps and Conclusions Foam –Measure thermal conductivity. Commercial firm, laser diffusivity –Anyone else interested and capable to test by other means? Have samples... –Have submitted proposal to develop foam and characterize it with company but wont know for a few months if approved. –Module removal trials on samples with glue surface + foam. Is this a problem? If yes, go back to thin laminate on surface, works for both stave and monolithic Stave/sector –Proof-of-concept complete…..could proceed to real design with existing materials. Note this would also work for disk sectors. Important to have unified concept for barrel and disks, in my opinion –Would like to test with CO2 if we can find someone interested with this capability…. Monolithic structure –Simple analysis of design variants to be done. What can work. –Would clearly work as is for flat half-disks….don’t have to worry about module mounting issues Need basic structural analysis(sag, stability…) to size carbon fiber aspects. But possible another step would be to model overall layout for both barrel and disks based on foam/fiber concept, mixing monolithic and stave approaches eg. B-layer and monolithic disks, remainder of barrel layers based on staves Would welcome collaboration with interested groups

18. M. Gilchriese 18 Backup Weight of monolithic mockup, roughly, without end rings –RVC foam+adhesives: 6.1 gms –Tubes: 3.6 gms –Shell: 3 gms –This gives only about 1.7 gm/cm per half-shell length Extrapolate to higher density foam –Foam x 3 or about 18 gms –Tubes same –Shell. Don’t know guess at least x 2 or 6 gms –About 4 gm/cm of half-shell length or roughly 320 gm for 80 cm length, not including end rings –Of course, really need full structural analysis….