1、Integrated Stave Mechanics/Cooling Backup,ATLAS Upgrade Workshop Valencia December 2007 M. Cepeda, S. Dardin, M. Gilchriese, C. Haber and R. Post LBNL W.Miller and W. Miller iTi,2,Introduction,We collect here some backup information for the presentation on integrated stave mechanics/cooling. A few n
2、otes Work on the integrated stave began in the Fall of 2006 The dimensions of prototypes, and a number of FEA calculations, were set then when detectors were assumed to be about 6cm in width. Thus prototypes were built assuming about 6 cm wide detector dimensions rather than the current 10cm “baseli
3、ne”. Thus a principal goal of the “6 cm” prototypes is to validate FEA estimates of the thermal performance, and then use the FEA to calculate for 10 cm In addition, the properties assumed for materials, particularly for thermal FEA calculations have evolved somewhat with time as have assumptions fo
4、r detector power after irradiation. Link to information on integrated stave mechanics/cooling http:/phyweb.lbl.gov/atlaswiki/index.php?title=ATLAS_Upgrade_RandD_-_Mechanical_Studies,Prototypes,4,Reminder of Prototype Concept,71.5mm,For prototypesfixed 1 year ago K13D2U, high-modulus facings Adjust f
5、acing thickness(layers) to achieve stiffness desired Carbon-fiber honeycomb in-between facing, fixed thickness Three types of tubes Flattened(C3F8) Big round with POCO foam(C3F8/C2F6) Small round with POCO foam(CO2),POCO foam: about 0.5 g/cc thermally conducting carbon foam,Link to drawings is here,
6、5,Prototype Stave Core Assembly,6,Weight and Material,Measured weights for 1m prototype(10 ply facings) and extrapolation to thinner facings(3 ply) and width for 10cm detectors given below. Note assumes minimal side closeouts Tube is flattened. Would get similar numbers for POCO foam+smaller tube,7,
7、Thermal Measurements,Measurements before and after thermal cycle 50 times to -35C are summarized below Delta T calculated from average of inlet+outlet water T for convenience. Max and min given to nearest 0.5C. Delta T rounded to nearest degree. No difference between before and after thermal cycle w
8、ithin errors Note tube(4.8) with foam compared to flattened is better as is smaller tube with foam. We attribute this to better coupling to tube FEA results are given(for fixed fluid temperature everywhere). Agreement within 20% or roughly 1.5C. Writeup of FEA is at link here,8,Remove/Replace,We hav
9、e completed a number of trials of gluing glass and silicon with SE4445 adhesive that was used to attach all pixel modules to local supports in the current pixel detector. Has decent thermal properties and already tested to 50 MRad for pixels. Attach, let cure(both week long and about 2 month long te
10、sted), remove, clean and replace. Straightforward mechanically, only need simple tooling for close-together detectors promising (no surprise since did this already for pixels) Pictures on next pages, although hard to see,9,Removal Pictures,Glass slide after removal(slide at bottom of picture) Starti
11、ng to peel SE4445,Silicon detector after removal and before cleanup After about 2 month cure. Done with two detectors, same result,Thermal FEA,11,Comments,Some of the most recent results are included here Many previous studies with somewhat different parameters. See the wiki,http:/phyweb.lbl.gov/atl
12、aswiki/index.php?title=ATLAS_Upgrade_RandD_-_Mechanical_Studies,12,Thermal Runaway in 10cm Module,Thermal Runaway Issue: Based on new detector heating curve- (revised by Nobu-MIWG meeting November 2007) Quarter section from 10cm wide stave, single U-Tube Spacing of U-Tube divides heat load collected
13、 by each symmetrically Chip heat load and surface heating treated as variables,13,Thermal Runaway Model Parameters,14,Surface Heating Curve,New curve based on 1mW/mm2 at 0C (Nobu-MIWG Nov. 2007) and exponential temperature dependence,15,Thermal Runaway Solutions,Plot of peak detector temperature lea
14、ding up to runaway(as function of tube surface wall temperature),Surface heating 1mW/mm2 0C Exponential temperature dependency,(Nobu-MIWG Mtg. Nov. 2007),16,Thermal Runaway-Variable Surface Heating,Comparing effect of surface heating using 0.25W/chip as baseline,Surface Heating,0,1mW/mm2,2mW/mm2,17,
15、Detector Surface Heating,Curve at right shows slight deviation of solution convergence,Deviation caused by using peak silicon nodal temperature whereas solution is based on the detector outer surface edge average,18,Thermal Runaway-Typical Thermal Plot,Chip: 0.5W Coolant Tube Surface -16.8C Peak chi
16、p: 6.18C Peak detector edge: 5.17C,Throughout solutions peak chip and peak detector differential temperature stays near 1.0 to 1.1C,With 0.25W/chip the temp difference is nominally 0.5C,Nearly thermal runaway point,19,Bridge Thermal Model,Salient Features High conductivity (700W/mK, 0.5mm thick) CC
17、bridge material support for 0.28mm thick hybrid(1W/mK) 40 chips 0.25W/chip Detector 0.28mm thick, 148W/mK Allcomp carbon foam for bridge support (isotropic 45W/mK) Carbon Foam for tube support (45/45/45 W/mK) Reduced density over POCO foam (0.2g/cc versus 0.5 g/cc) Sandwich foam Allcomp foam option,
18、 0.1g/cc 3W/mK Comparison with Hybrid on 10cm Detector Thermal solution with both with inner tube wall at -28C Simulates -30C with 8000W/m2K No change made to material properties in 10cm detector with integrated hybrid,20,10cm Detector-No Bridge,Material Properties See previous slide (#2) 40 chips p
19、er detector, 80 total 0.25W/chip Q (Si)=0W Tube inner surface -28C, no convection coefficient Interest in T from chip and detector surface to tube surface Peak chip temperature Middle hybrid region: -20.5C Peak Detector Middle hybrid region: -21.5C T in region of max gradient: 6.5C,21,10 CM Wide Sta
20、ve-No Bridge,Solution Replaced honeycomb core with Allcomp carbon foam (0.2g/cm3: 45W/mK) Also, replaced POCO foam tube support with same foam Peak Chip Temp: -22.7C Peak Detector: -24C T (referenced to tube wall) 4C,22,10 CM Wide Stave-No Bridge,Solution: Simulate “outer” long strip detector One up
21、per and power hybrid for 10cm detector 20 chips 0.25W/chip Coolant tube inner surface: -28C Materials, see slide (#2) Detector Peak temp beneath hybrid: -24.8C T in region of max gradient: 3.2C Chip Peak Temp: -24.1C,23,Thermal Bridge Model (1/2 of 10cm),Wire bonds, simulated as thin solid, reduced
22、K to 97W/mK,Chips 0.38mm thick (148W/mK),Al Cooling tube 0.21mm ID,Separation between facings 4.95mm,10cm,Foam bridge support,1mm air gap for bridge,24,Bridge Thermal Model,Enclosed bridge model in an air box. Air participates only through pure conduction. Air fills all cavities not occupied by a so
23、lid,Air box,25,Model Parameters,Cable and adjacent adhesive layers modeled as single layer 0.227mm and K=0.31W/mK,26,Solution with -30C Tube 8000 W/m2K 0.5W/chip Q (Si)=0,Slight asymmetry caused by variance in interior coolant wall temperature,Detector max=-21.4C,Chip peak=-16.5C,27,Solution with -3
24、0C Tube 8000 W/m2K 0.25W/chip Q (Si)=0,Slight asymmetry caused by variance in interior coolant wall temperature,Detector max=-25.8C,Chip peak=-23.3C,28,Solution with -30C Tube 8000 W/m2K 0.25W/chip Q (Si)=0,Bridge foam and tube foam 45W/mk, density 0.2 g/cm3 (no POCO foam),Peak detector temp -24.2C,
25、Sandwich foam core 3W/mK, density 0.06 g/cm3,Peak chip=-21.8C,Wire bonds 97W/mK,29,Fluid Calculations,C3F8 calculations are here for flattened tube and here for round tube CO2 calculations are here and here. Summary from main talk reproduced below Note T(film) is an average around the loop T(loop) f
26、ollows from the P vs T curves for the fluids and is rounded to the nearest 0.5C These calculations are complex and need validation by measurements,30,Adhesive Joint Considerations,There are numerous analytic solutions for adhesive joint shear stress caused by thermal expansion of dissimilar material
27、s General theme is that the shear stress is a maximum at the ends of joint, and essentially zero at the center Maximum shear stress at the end is independent of the length of the joint Key factors are:modulus of elasticity, CTE, and thickness of joined materials thickness and shear modulus of the ad
28、hesive Temperature differential A useful reference to bound the problem: Thermal Stresses in Bonded Joints, W.T. Chen and C.W. Nelson Suggests for carbon foam joined to aluminum tube with CGL7018 (very compliant adhesive) or EG7658 (semi-rigid) that shear stresses remain within material limits for a
29、 100C temperature change Prototype testing will confirm our expectations,31,Carbon Foam to Aluminum Tube Joint,100C temperature differential Cure temp to -25C Foam thickness=8mm, G=690MPa, =4ppm/C Aluminum wall thickness 0.305mm, E=10Msi, =12ppmC Adhesive thickness=0.10mm, Compliant G=40MPa (5862psi
30、), Rigid G=1 GPa Max shear stress, =1062psi, compliant = 42psi,32,Computer-Based Solutions,Structural Problems NASTRAN FE solver Recent solutions with NE NASTRAN with FEMAP interface Prior work with MSC NASTRAN, but MSC no longer can bundle the NASTRAN solver with FEMAP pre-processor Choose not to u
31、se PATRAN pre-processor Fluid/Thermal Problems Use CFDesign computational fluids dynamics code Very versatile Allows use of shell elements for describing interface resistances HEP Silicon-Based Tracking Detectors Issue with very, very thin solids mixed in with larger solids In reasonable sized geometry, some solids may have only surface nodes, and no internal nodes; possible consequence is reduction of solution accuracy,
