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PHENIX FVTX
Status of Mechanical and Thermal Design Work
Eric Ponslet, Shahriar Setoodeh, Roger SmithHYTEC Inc.
FVTX Collaboration MeetingAlbuquerque, NMMarch 12, 2007
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 2
Latest Baseline Design• Still Evolving…
• Modular Design– Detector module (“wedge”) Half disk Half Cage (“clamshell”) FVTX
• Wedge is Built on a Graphite Fiber/Cyanate Ester Thermal Backplane– Serves as structural support and heat transfer path to edge cooling– 0.76mm thick K13CU/CyE
• Very high stiffness and thermal conductivity fiber• Symmetric, balanced layup (won’t warp from temperature changes)
• Wedges are Fastened to Support Panel– Two alignment pins (ceramic?) and 3 screws (nylon) per wedge– Thick RT-cured silicone bridge provides thermal interface to cooled support panel– Allows replacement of single defective wedge
• BUT: requires cutting the Silicone thermal bridge
• Half-Disk Support Panel and Support Cage– Sandwich construction: Graphite fiber (M55J) faces and aluminum honeycomb
• Liquid Cooling– Tube embedded in panel in place of core, near OD of half disk– Single phase coolant at high flow rate (turbulent)
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 3
Wedge Design
Backplane (0.76mm graphite fiber composite)
Screw (nylon)
Pin hole(for alignment)
Pin hole (for alignment)
HDI
Connectors for extension cables
Detector
ROC’s (26)
Screw (nylon)
All bonded with rigid epoxies
HDI
Detector
ROC’s
Backplane
Rigid, thermally conductive epoxy
Rigid epoxy
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 4
Half-Disk Assembly
Silicone bond(for heat transfer)
HDI
Detector
ROC
Screw
Pin
Support Tab
Support Tab
Support Panel
Support Tab
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 5
Cooling and Tab Detail
Screw hole (mounting to cage)
Pin hole (mounting to cage)Hose barb for coolant
Screw (holds wedge on disk)
Silicon detectors, HDIs, and back-planes made transparent for clarity
Pin (aligns wedge on disk)
ROC
Built-in cooling tube
Silicone heat transfer bridge(RT-cured, 2-part silicone)
Silicon detector
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 6
Half-Disk Assembly: Details
Thermally conductive
Silicone
Plastic inserts for screws and pins
Single piece plastic insert for screws and pins
Standoff plate
Foam core
Honeycomb core
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 7
Support Panel Construction
Locating pinInsert for pin (TBD plastic)
Insert for screw (TBD plastic)
GFRP Face sheet (0.25mm)
Honeycomb core (4.76mm, 32 kg/m3)
Foam core(TBD mat’l)
Core insert for pins and screws (TBD plastic)
Cooling tube
Hose barb
GFRP Face sheet (0.25mm)
Standoff plate (TBD Plastic)
Mounting tab
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 8
Half Cage Assembly
Cooling hose (silicone)
Sta
tion 1
Sta
tion 2
Sta
tion 3
Sta
tion 4
Z
Y
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 9
FVTX Assembly
VTX Pixel barrel (#4)
VTX Pixel barrel (#3)
VTX Pixel barrel (#2)
VTX Pixel barrel (#1)
Too close!(move FVTX station 1 back?)
FVTX
Sta
tion 1
FVTX
Sta
tion 2
FVTX
Sta
tion 3
FVTX
Sta
tion 4
57mm 54.5mm 54.5mm
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 10
Modularity & Testability• Three Levels of Subassemblies
– Can all be tested independently– Test stands will be designed– Single Wedge stand will need to incorporate cooling feature
Detector Module (aka Wedge)
Half Disk Module Half Cage Module
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 11
Summary of Key Requirements• Environment
– Operate in dry Nitrogen at atmospheric pressure and RT– Radiation dose: <200 kRad over 10 years (very low)– 10 year design life
• Functional– Detector modules must be individually removable during initial integration– FVTX must be assembled around beam line (“clamshell design”)
• Heat Dissipation– 100μW/channel, 128 channels/ROC– 26 ROC’s/detector (stations 2, 3, 4)– 10(?) ROC’s/detector (station 1)
• Temperature Limits (ROC and detector)– Not specified
• Radiation Length Limit of Station– Not specified
• Dimensional Accuracy/Stability– See next slide
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 12
Dimensional Accuracy Requirements• Initial Alignment or Surveying Tolerance
– Detector relative to station• Initial assembly/surveying of half-disks
X,Y < ±10μm
Z < ±200μm (75μm goal)– Station location
• Initial assembly/surveying of half cages and complete system
X,Y,Z < ±200μm
• Static Deformations– Non-rigid-body deformations such as temperature-induced bowing of detectors
X,Y < ±10μmZ < ±14μm
• Stability– Unsteady Deformations and displacements (vibrations,…)
X,Y < ±10μmZ < ±14μm
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 13
Radiation Length Status (1/2)• Total RL of Station 2, 3, or 4
– Area averaged to active area (45mm IR, 170mm OR) = 2.2%– Worst case local value = 4.3% (going through cooling tube)
Distribution of area-averaged, normal incidence RL
0.000%
0.100%
0.200%
0.300%
0.400%
0.500%
0.600%
0.700%
See notes on next slide
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 14
Radiation Length Status (2/2)
Distribution of worst-case, normal incidence RL
0.000%
0.200%
0.400%
0.600%
0.800%
1.000%
1.200%
1.400%
1.600%
Notes:•Assumes 35cm RL (X0/ρ) for coolant (no data)•Assumes 1.2cm RL (X0/ρ) for Nickel (no data)•Honeycomb core is treated as uniform mass distribution•Titanium fittings not included (outside of active area)•Screws not included (type TBD; likely nylon so small impact) •Alignment pins not included (material TBD; may be removable)
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 15
Cooling Assumptions• Keep FVTX (and VTX) near Room Temperature
– Eliminates difficulties with cold gas enclosure• flow dry nitrogen at RT
– Mitigates thermal stress and dimensional stability issues
• Power Removed– 8W per half disk (stations #2, 3, 4)
• Cooling Tube Embedded in 3/16” Support Panel– Square cross section (3/16” by 3/16”) with super-thin (<50μm) nickel wall
• Coolant– 3M Novec HFE-7000– Completely harmless to (even live) micro-electronics– Environmentally friendly– Dense (1.4 × water)
• Flow Regime– Single phase– Strongly turbulent
• Re ~ 10,000• Flow velocity ~ 0.7 m/sec• Flow rate ~ 20 g/sec = 14 mL/sec = 0.86 L/min (per ½ cage)
– Flow-induced vibrations?
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 16
Coolant to ROC Thermal Path• Use Simple Correlations to Evaluate
– Pressure drops– Temperature drop from fluid to cooling tube
Approximate temperatures with 10°C coolant flowing at Re~10,000(0.76mm K13CU backplane, 50μm Nickel tube, 0.2 W/mK epoxy, 0.75 W/mK silicone)
Inside of F.S: 12.2°C
Outside of F.S: 12.6°C
Warmest ROC: 20.3°C
Tube wall: 11.3°C
backplane (K13CU)
HDI
Panel core (Al HC)
Bulk coolant: 10°C
Back of wedge backplane: 15°C
Nickel tube (TBC)
Inner
Rad
ius
Oute
r R
ad
ius
Foam (TBC)Thermally Conductive Epoxy
Thermally Conductive Silicone
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 17
Liquid Cooling Circuit
FVTX Inlet: 10°C, ~5 psig
ROC station 4: ~20.6°C
Outlet plane 4: 10.3°C
FVTX Outlet: 11.1°C, ~3 psigROC station 3: ~20.9°C
ROC station 2: ~21.2°C
Outlet plane 4: 10.6°C
Outlet plane 4: 10.9°C
Warmest ROC, station 1: ~21.4°C
• Run 4 Half-disks in Series
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 18
Wedge Analysis: Assumptions• Bonds:
– Silicon detector to HDI: rigid, RT-cured epoxy– ROC to HDI: rigid, RT-cured, thermally conductive (1.5W/mK) epoxy– HDI to backplane: rigid, RT-cured epoxy
• HDI– Multi-layer Kapton HN/Cu (2 ground planes, 2 signal planes)– Total thickness 0.176mm
• Backplane– QI [0°/60°/-60°]2S K13CU/CyE graphite fiber composite
– Total thickness: 0.762mm
• Power Dissipation– 26 chips per wedge (stations 2, 3, 4)– 0.0128W/chip
• Effective Backplane Thermal Conductivities– Estimated, based on historical test data (conservative)
– Kx = Ky = 130 W/m.K (~5 times lower than encapsulated TPG)
– Kz=1 W/m.K
• Boundary Conditions– Bolted connections at 3 points– Silicone thermal bridge near OD– 15°C at back side of backplane, near cooling tube
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 19
Wedge Analysis: Temperature Distribution
3-D Temperature Contour
Max Tº = 20.3ºCWarmest ROC
Min Tº = 15ºC (Boundary condition at back side of backplane)
Radial Temperature Variation
Radius (from beam CL, meters)
Tem
pera
ture
(°C
)
• Warmest ROC is 5.3ºC Warmer than Back Edge of Backplane– 10.3ºC warmer than coolant
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 20
Wedge Analysis: Stresses and Distortions• Assuming Assembly at RT
– Max distortion of silicon detector = 10.4μm– Max normal stress in silicon = 0.5 MPa (<< 10MPa, conservative allowable)– Max shear stress in bonds = 0.8 MPa (< ~13MPa allowable)
Radius (from beam CL, meters)
Dis
tort
ion (
mete
rs)
Max deflection = 10.4μm
Zero deflection (boundary conditions)
Z deflection VS Radius
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 21
Wedge Design: Conclusions• GFRP Backplane is
– Conductive enough: 5.3°C from outer edge to ROC– Rigid enough: 340 Hz natural frequency
• HDI is Conductive Enough without Thermal Vias– Recommend using Kapton MT (higher conductivity)
• Distortions are Low– <11 μm with 10°C coolant (<14μm requirement)
• Stresses in Bond and Detector are Comfortably Low– No need for compliant adhesives
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 22
Disk-Level Modeling: Thermal distortion
Max deflection of detector ~8μm
Fundamental vibration mode: 164 Hz
• FEM of half disk, fully populated with detector modules• Used for stiffness & Deflection calculations
Distortion due to cooling
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 23
Assembly of Detector Module• Assembly Concept Based on
– Base tool• Vacuum chuck
– Keep backplane flat
• Holds backplane– Mechanically aligned (2 pins)
– Bonding tools • Aligned to base with two pins• Vacuum chucks
– Keep things flat
• One to hold HDI– HDI optically aligned (or use pins)
• Another to hold silicon detector– Detector optically aligned
– Two-step assembly1. Bond HDI to backplane2. Bond detector to HDI/backplane assembly
• Open Questions– Shim between tools to control bond thickness?– Continuous/discontinuous bonds?
1: bond HDI to Backplane
2: bond detector to HDI/Backplane
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 24
Key Remaining Technical Issues• Requirements:
– RL and ROC temperature requirements– Relate to science requirements and finalize
• Design:– Gas enclosure
• Concept & design
– Signal processing boards• Dimensions• Support structure• Cooling
– Cooling system• Refrigeration, pumping, and control system• Not currently within HYTEC’s scope
• Design Verification– Prototypes and performance testing
• Flow-induced vibrations• Cooling performance• Dimensional stability
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 25
Future Work: Before DOE Review• Finalize and Document Requirements (LANL)
– RL– Temperature limits
• Finish Preliminary Design (HYTEC, funded)– In progress, 3 more weeks
• Document Preliminary Design (HYTEC, funded)– In progress, report expected by April 6
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 26
Future Work: Before Construction Phase• Not Funded, but Manpower is currently available• Detailed Design
– Adhesive selection, inserts, station 1• System Design
– gas enclosure, “big wheel” • Cooling Hardware (not in HYTEC’s scope)
– Internal: tubing, clamps, etc.– External/system: refrigeration, circulation, and control system
• Prototyping– Detector module prototypes
• GFRP backplanes + dummy HDI + dummy SSD (passive silicon wafer) + resistive heaters (ROC heat)
• Used to– Test assembly tooling– Thermal cycling (stresses in bonds and SSD)– Heat transfer testing – Validate temperature induced deflections (TV Holography?)
– Station prototype• One half disk (large)• Supported by dummy structure (no cage)• Populated with dummy detector modules• Used to
– Test assembly and alignment concepts– Measure flow induced vibration (accelerometers)
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 27
Funding Issues• HYTEC has No Remaining FVTX Funds
– Will finish preliminary design work and write report by April 6
• Funding Needed Before DOE Review– Continue refining design and updating CAD and analysis – Support DOE review (if needed)
• Funding Needed Before Construction Phase– Complete and finalize design– Prototyping and testing
Without new funding by early April, current engineering team will have to be re-assigned to other projects
HPS-111006-0010 – FVTX Mechanical/Thermal Design Status – March 12, 2007 – Slide 28
Concluding Remarks• Structural/Thermal Design is Settling
– Rigid– Stable – Modular
• Numerous Details still TBD– Adhesives, joint details, tooling,…
• Various System Issues still TBD– Gas enclosure, support and cooling of big wheel,…
• One Technical Question– Flow induced vibrations?
• Need disk prototype to evaluate
• Need Bridge Funding through end of FY– Continuity of engineering support
• Inevitable design changes to come
– Remaining design tasks– Prototyping and performance testing