Pixel Upgrade Carbon Foam and Outer Stave Update E. Anderssen, M. Cepeda, M. Garcia-Sciveres, M. Gilchriese, T. Johnson, J. Silber Lawrence Berkelely National Laboratory W. Miller, R. Ramirez, W. Shih Allcomp, Inc M. Oriunno and M. Convery SLAC AUW November 2010

Topics Outer stave concept Allcomp Inc carbon foam properties Prototypes constructed Prototype testing and design validation Finite element analysis summary Future plans Summary 2

Outer Pixel Stave Concept About 1.4m long, 4cm wide and 4-5mm thick. Thickness depends on final tube ID. Modules on both sides, overlap for full coverage, makes module mounting easier Embedded cable/wires for power, signals and HV (baseline). Option of cable on top (similar to strip staves) High-K, low density, all-carbon foam (Allcomp)(machined) + high stiffness/good K carbon fiber(K13D2U or better) Tube can be Ti or SS(or whatever). ID set by fluid/delta T requirements. CO2 cooling assumed End bend possible to minimize number of pixels hit, reduce material, reduce or eliminate need for disks 3

Support Concepts for Outer Staves 4 Similar to strip stave support. Conceptual. Deflections etc analyzed but no recent work Very conceptual. End support may be possible Bend angle, location not optimized

Carbon Foam – Key Component All designs in  last 2 years are based on carbon foam from Allcomp Inc. – Porosity (pores per inch or ppi) adjustable from about 30 to about 130 – Density and thus thermal conductivity (K)can be tuned from about 0.1 W/m-K to about 0.8, although this is porosity dependent. – Manufactured in blocks and machine to shape Significant development and foam properties measurement program since last AUW. Baseline Allcomp foam for recent and future development of outer staves – 130 ppi with  = (0.22 nominal) Also used for inner staves Blocks have now been sent to number of other groups. Buy directly from Allcomp Higher density (0.45 g/cc, K about 80) in use for strip stave prototypes 5

Foam Properties Talk at recent LBL meeting summarizing current knowledge at Access password mech What has been measured (130 ppi baseline) – Thermal conductivity, multiple methods at room T. K  35 – CTE of foam near room temperature – CTE of foam loaded with epoxy(Hysol 9396) and BN powder(  30%) for - 130C<T<30C. Significant T dependence(epoxy) – Compressive modulus and strength (room T) up to 25% strain – Tensile modulus and strength(room T) – Uniformity block to block and within block Limited statistics but acceptable uniformity achieved – Note do not expect significant T dependence of foam properties except when loaded with epoxy 6

Prototypes Made/Tested Many small prototypes during development of foam – not discussed here Standard small test staves, 12cm long, 4cm wide, about 5mm thick – Both SS(2.77mm OD) and Ti (2.2 mm OD) tubes used – Made at both LBL(6) and Allcomp (2, SS only so far) Two 1m staves (using older foam, not 130 ppi) – SS tube (2.77mm OD). – One with cable embedded and one with cable on top – Made at Allcomp ½ length (70cm) active stave (real cable) (baseline foam) – SS tube and made at LBL Short section of bent stave (20 degree bend) – SS tube made at LBL 7

Outer Stave Prototype Pictures 8 1m prototype with cable on top and silicon heaters ½ length (70 cm) with embedded active cable 12 cm prototype with silicon heaters in holder for testing Section of bent stave

Summary of Tests Done Short staves – Both SS and Ti tubes. 900 thermal cycles (20C -35C), then -70C(dry ice), then -175C(LN2), then 150 Mrad – Different set, 350 thermal cycles (20C -35C) – SS tube only, 1 GRad then 250 thermal cycles (20C -35C) – Thermal measurements using room T water at high flow (1 liter/min) (at both LBL and Allcomp). Very good agreement. 1m staves – Thermal measurements using room T water at high flow (1 liter/min)(for one at both LBL and SLAC) – CO2 tests (including dozens of thermal cycles to -35 or lower) at SLAC – Deflection measurements ½ length active stave – Thermal measurements using room T water at high flow (1 liter/min)(at LBL) – Continuity testing of active cable after assembly 9

Example of Thermal Test of ½ length (70 cm) Prototype Outer Stave 10 LBNL test and CFDesign Prediction ΔT (avg)=9.25C ΔT(avg)=9.52C CFDesign simulation 8W or 0.5 W/cm 2 Per heater/module On both sides Includes film drop in water And adhesive layer(SE4445) to heater

Summary of Pixel Outer Stave Prototypes and Tests - What Have We Learned Manufacturing – Straightforward but requires the usual attention to details to achieve tight dimensional tolerances – Very similar results from two places (LBL and Allcomp) After extensive thermal cycling – no change in thermal performance After irradiation to 1 GRad. Thermal performance (including module adhesive) degrades by < 10% e.g. by < 1C out of 9-10C total  T from bulk fluid T to module surface. Operation with CO2 is as expected, good performance Comparison of thermal measurements to FEA by different people and using different codes – agreement to within about 10% in  T with measurements for both water and CO2 11

FEA of Stresses Significant effort devoted to detailed FEA to understand why reliability after extensive thermal cycling is so good. And how stress margin might be improved. See talk at link below for many more details Access password mech Very detailed FEA model of short stave – Non-linear materials properties as measured – Include temperature dependence of properties (CTE) as known – Critical stress area in foam is in very small region at ends. Foam non-linear in compression. – Recognize that FEA treating foam as continuous material breaks down as mesh size approaches pore size, when not clear. And adhesive/foam interface impossible to model precisely. Summary below for  T of 85C 12 Tube not glued to endcap in any prototypes tested

FEA Predicted Distortions 13 Chips out of plane ~<10microns Cable ~<12microns Also for  T of 85C

Pixel Outer Stave Prototype Plans Foam characterization continuing at Allcomp. Others will have experience soon. Allcomp is repeating thermal cycle testing with short staves made by them Next step is to make at least two 1.4m staves, either both at Allcomp or one at LBL and one or two at Allcomp Design issues – Attach tube to endcaps or not? With attachment issue is reliability of adhesive joints (reinforce mechanically?) – Reduce amount of glue used. See talk by Tim Jones. Reliability after thermal cycle of co-curing either foam to facing or everything including cable has to be proven. FE-I4 chips only module on ½ length active stave by January and test electrical performance End-of-stave region – services integration has not been addressed yet and should be by Spring 2011 to assess impact on design 14

Summary – Pixel Upgrade Outer Staves Outer stave concept validated through prototyping, testing and analysis √ Reliability after extensive thermal cycling √ Reliability up to 1 GRad √ Operation with CO2 √ Manufacture of ½ length(70cm) “active stave” to baseline design √ Manufacture of “bent stave” Next steps – Build full-length (1.4m) prototypes – Electrical test on ½ length stave with FE-I4 chip module – Reduce material (and then repeat reliability testing) – Continue analysis to evaluate prototypes 15