1. M. Gilchriese Integrated Stave Mechanics/Cooling June 5, 2008 CERN

2. M. Gilchriese Outline Additional information at –http://www-physics.lbl.gov/~gilg/ATLASUpgradeRandD/StaveReview/stave_draft_note.pdfhttp://www-physics.lbl.gov/~gilg/ATLASUpgradeRandD/StaveReview/stave_draft_note.pdf Concept Prototype construction/test Thermal performance Structural studies Material Questions What if….. Development plan Production cost/schedule 2

3. M. Gilchriese Concept Approximate dimensions of mechanical/cooling core –Short-strips: length about 1 m + end-of-stave card (  2 m possible) –Long-strips: about 2 m long + end-of-stave card –About 11 cm wide –Thickness  3-3.5 mm (CO 2 ) or  5.5-6.5 mm(C 3 F 8 ) 3 Bus cable Hybrids Coolant tube structure Carbon honeycomb or foam Carbon fiber facing Readout IC’s Silicon sensors

4. M. Gilchriese Prototypes Prototype stave structures were fabricated and tested (thermal/mechanical) starting Fall ‘06 up to about one year ago. The design of the prototypes was fixed before choice of  10 x 10 cm 2 detectors and the prototypes are therefore  7 cm wide. Goals: gain experience with fabrication, thermal performance, simple mechanical properties and build 1 m object for modules 4 Prototype Number Facing Length (m) Facing Material# of Plies per Facing Tube TypePurpose 10.343CN6010FlattenedAssembly trial 20.343K13D2U10FlattenedThermal prototype 31.07K13D2U10FlattenedFor modules 40.343K13D2U34.8 mm round/ POCO foam Thermal prototype 50.343K13D2U 32.8 mm round/ POCO foam Thermal prototype

5. M. Gilchriese Prototype Construction 5 Honeycomb core Prototype #4 Prototype #3 Facing Carbon foam Prototype #5 Honeycomb  5 mm thick for all prototypes

6. M. Gilchriese Prototype Testing Thermal performance –Simulated heat loads(e.g. 3.3 W/”hybrid”) –IR imaging. Water coolant. Compare to FEA –Before & after T cycling -35 to 20C As built-accuracy (CMM scans) Deflection measurements –Compare to expected properties “Module” removal trials –Attach dummy silicon with adhesive, cure, remove, replace Detailed weights -> material estimates 6 Bus cable Alumina Heaters 0.3mm silicon Thermal measurements of prototypes Dummy detector removal

7. M. Gilchriese Prototype Lessons Fabrication straightforward –Obviously some learning but no surprises Thermal performance (  T/Watt) similar for all three tube types, 4.8 mm tube+foam being best, flattened tube or small tube about the same Thermal performance in good agreement with FEA within errors of measurement based on expected materials properties (and their errors). No change in thermal performance after 50 cycles from -35C to 20C Deflection measurements in reasonable agreement with expectations (within  20%) but small sample (two prototypes) As-built accuracy (planarity of facing plane) somewhat worse than we hoped (1 m prototype). –Deviation from average (rms) 30-60 . All points within  ± 100  window –Why? Non-uniformities in honeycomb as provided by vendor. Can be reduced Dummy module removal, clean-up and replacement easy with SE4445 (adhesive used to attach current pixel modules) 7

8. M. Gilchriese Models of Thermal Performance 8 Shown for  10 x 10 cm 2 detectors ¼-model, primarily for thermal runaway Agrees with multi-hybrid model  T Multi-hybrid model. More elements. Vary composition of stave. Assess  T change

9. M. Gilchriese Nominal Structure Thermal Performance Honeycomb core ¼ model run as function of tube wall temperature Take into account detector heating Can already tell from this that C 3 F 8 with T min =-25C is problematic 9

10. M. Gilchriese Modified Structure Performance Relevant for C 3 F 8 with T min =-25C Add more cooling – triple U-tube Or replace honeycomb with thermally conducting foam 10

11. M. Gilchriese More Improvements to Structure? Vary facing thermal properties. Practically gain  1C in  T Improve K of bus-cable? Assumed K=0.12. If K=0.38 (estimated from average metal content), gain  1.5C in  T. 11 Effects on thermal performance from variations in the facing properties assuming a 0 o C temperature for the coolant tube inner wall, 0.3 W/chip and no detector heating.

12. M. Gilchriese Bridged-Hybrid Models Some studies but not full thermal runaway estimates See backup note for materials Concept uses foam in addition to facings to carry heat from foot of bridge back to cooling tube 0.25 W/chip, -28C wall temperature, no detector heating for these results 12

13. M. Gilchriese Bridged-Hybrid Thermal Results Effect of air flow studied (not significant at T and flow studied) Nominal stave design (not bridge) at 0.25 W/chip, -28C wall and no detector heating has T max  -22C Bridge -20 to -18C depending on foam K Optimization of tube position (closer to bridge foot) not studied, expect would reduce  T max 13

14. M. Gilchriese Two-phase Flow Calculations Two-phase flow estimates for CO 2 (-35C) and C 3 F 8 (-25C) Thermal runaway estimated at entrance (worst case) 14 Entrance(   0) Exit (   1) T fluid  -35 o C 240 W heat load 2 m tube, 2.2 mm ID Vapor quality (  ) Complex calculations!  T  P  1 o C T wall  -35+1.75  -33C T wall  -35+1+2.5  -31C CO 2

15. M. Gilchriese Thermal Runaway – CO 2 Bulk fluid temperature -34C (entrance) Fixed heat transfer (film) coefficient 6833 (calculated at entrance) for 240 W Note film coefficient is heat dependent(goes up with more heat), not taken into account by us here Headroom OK 15

16. M. Gilchriese Thermal Runaway – C 3 F 8 (T min -25C) Heat transfer coefficient either calculated at entrance for 240 W(different for single and triple U-tube) or taken as 3000. Note that we would calculate value to be 3000 for 500 W (about at thermal runaway) Triple U – OK Foam(K=15 W/mK) instead of honeycomb  OK If C 3 F 8 (T min -25C)+foam, need measurement! 16

17. M. Gilchriese Thermal Performance Conclusions The baseline design with a honeycomb core and a single U-tube does not have acceptable headroom for T min = -25 o C, representative of current cooling performance with C 3 F 8 The baseline design with a triple U-tube and a honeycomb core has acceptable headroom for T min = -25 o C, representative of current cooling performance with C 3 F 8 A modified design with thermally conducting carbon foam instead of honeycomb and a single U-tube may have acceptable headroom for C 3 F 8 with T min = -25 o C (and colder fluids) The baseline design has acceptable headroom for a single U-tube and honeycomb core for T min  -35 o C, which could be applicable to CO 2 or perhaps mixtures of C 3 F 8 with other fluorocarbons. The headroom could be increased by small amounts from optimization of the carbon-fiber facings (gain  1 o C) and from improved thermal conductivity of the bus-cable (gain  1- 3 o C). These possible gains would be most important to realize if C 3 F 8 with T min about -25 O C were used. The headroom for a bridged-hybrid design with T min  -35 o C is likely to be sufficient (but more precise calculations remain to be done) 17

18. M. Gilchriese Structural Studies Preferred support concept is stave-on-shell Stave sag, vibrational modes, etc coupled with number of supports along length, shell design (minimize overall X 0 ) – not studied in detail. Simple calculation of sag (< 75  in horizontal position, worst) with support every  50 cm Stave distortions upon cool-down from 25C to operating temperature –Quick look taking artificially bad case of alternating modules top and bottom. Result is  11 microns out of plane for 50C temperature change –Should be less with balanced structure Shear stress between Al tube and foam estimated and looks OK – see ATLAS note Clearly much more structural analysis needed 18

19. M. Gilchriese Material Material estimates for simple stave only. Does not include coolant, bus-cable, modules, end-of-stave cards, support points, strain relief… Based partly on prototype weights (scaled) and from calculation Uncertainty in facing thickness/density, adhesive choices, tube diameters => plausible range below for different configurations Top three for nominal design (modules glued to bus-cable). Bottom estimate for bridged-hybrid 19 C3F8C3F8 CO 2

20. M. Gilchriese Questions Is it credible to assume the use of conducting carbon foam around the tube in the baseline design (with honeycomb core)? –Yes. Foam of density  0.5 g/cc (as used in prototypes) is available from at least two vendors. Production (batch size) is 150,000-200,000 cc, far more than we would need One of the design alternatives uses low density carbon foam (  ≤ 0.2 g/cc). Is this credible? –We think so. We are actively working with three vendors (for pixel staves) on conducting foam with the appropriate properties and have samples in hand from all three. The production rate is claimed to not be driven by . Are there any other “non-standard” materials proposed for use? –No. Could you make a 4 m stave for the long-strip layers? –Not in my opinion 20

21. M. Gilchriese What If…. What if the short-strips staves were 2 m long instead of 1 m? –Fabrication of 2 m stave cores would not be significantly more challenging than 1 m stave cores. Could be cheaper (less labor) since fewer parts. –CO 2 cooling at about -35C would work with a  4 m single U-tube but probably would increase tube ID by small amount (tenths of mm) –Structurally would be same as 1 m since supported along length (e.g. every 50 cm) except possibly for fixation scheme that accounts for CTE difference between stave and shell support but even this goes away if 2 m is fixed at center and 1 m fixed at an end. –Good experience handling 1 m prototype, including wire bonding. 2 m harder, but not by much –Survey of modules on 2 m stave harder, may require cross reference at 1 m scale, depends on survey capability. Not showstopper. What if stainless steel pipes were used? –Impact on thermal performance small (< 1C) –Bending (for larger diameter for C 3 F 8 ) – not sure –Radiation length increase CO 2 (C 3 F 8 )  0.3(0.5)% x ratio of wall thickness to Al 21

22. M. Gilchriese Development Plan These four principal activities would occur largely in parallel Thermal (  1 yr once coolant testing available) –Selection of coolant essential to make progress (or need to carry multiple design options) –Small-scale prototypes likely to be needed –Design, fabricate and test full-length prototype(s) Structural (  1.5 yrs) –Also coolant dependent. Once coolant selected….. –Combined design of stave and supporting structure (obviously also coupled with thermal design) => baseline design that meets thermal and structural requirements. –Build prototypes and test (in addition to thermal prototypes) Module interface (  2 yrs) –Define and prototype module mounting requirements: temporary holding for module mounting, survey, testing (boxes, how to cool), shipping (boxes), etc… Production planning interface (  2 yrs) –Tooling, procedures, who builds what, etc.. Durations shown ignore resource constraints! 22

23. M. Gilchriese 23 Production A preliminary estimate of production cost and duration made earlier this year: http://www-physics.lbl.gov/~gilg/ATLASUpgradeRandD/StaveReview/Cost%20Estimate%20for%20Integrated%20Stave%20Mechanics.doc http://www-physics.lbl.gov/~gilg/ATLASUpgradeRandD/StaveReview/Cost%20Estimate%20for%20Integrated%20Stave%20Mechanics.doc Covers barrel and simple extrapolation to disks. All staves/petals. Material and equipment costs in U.S. $. Cost and manpower range estimated. Includes contingency (but not escalation) Materials and equipment: $2-4M Engineering labor: 8-12 FTE years Technical labor: 28-48 FTE years Rough schedule –  2 years design/prototype –  1 year pre-production –  2 years production Resource constraints not included! Costs in U.S. ‘08 $