phenix bnl reviewfebruary 19 th, 2007 1 mechanical design and studies for the fvtx detector, along...

PHENIX BNL Review February 19th, 2007 1

MECHANICAL DESIGN AND STUDIES FOR THE FVTX DETECTOR, ALONG WITH ITS INTEGRATION AS A PART OF THE VTX

WALTER SONDHEIM, LANL MECHANICAL SYSTEMS ENGINEER FOR THE VTX & FVTX ERIC PONSLET - HYTEC

PHENIX BNL Review February 19th, 2007

• Outline:– Mechanical Specifications and Requirements– Baseline Design– Initial Material Selection– HYTEC FEA Analysis– Wedge/Half-disk Assembly Scenario– Mechanical Integration with the VTX System

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Future home for the VTX and FVTX detectors: Muon arm acceptance: 12 – 35 degrees

As they say in Real Estate, “location, location, location”.


Basic components of the FVTX 15 degree wedge detector:

Silicon Sensor (1)

PHX readout chips (26)

HDI

Thermal back-plane, behind HDI

35.mm

Readout connectors (2)

Beam Axis


Each large detector panel would consists of 30 - 15 degree wedges, mounted to a honeycomb core panel front-to-back, offset by 7.5 degrees in phi.

PHENIX BNL Review February 19th,2007

• Mechanical Specifications and other Requirements:– The FVTX is expected to receive as much as 20 kRads exposure per

year.– Nominal detector design resolution is ~20. microns or better in r

and much larger in phi.– Require that the placement of the silicon sensors on a plane be

placed and surveyed to an accuracy of 10. microns in x and y.– Static distortions of the planes should also be at or below 10.

microns in x and y.– Static distortions in z, or a given sensor being out of plane, should

be kept to 10.microns/tan(35) = 14. microns or less. 35 degrees is the maximum acceptance track angle.

– Stability due to vibration must be kept less than 10. microns.– Station to station alignment in the FVTX has a goal of 75. microns,

could be as high as 200. microns. Verification with straight-through tracks.

– Survey installation < 200. microns.

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• Baseline Design & Material Choices:– The FVTX detector will consists of 4 planes, each plane is hermetic phi.– Each detector panel consists of:

• One structural panel consisting of 1/4” thick (6.35mm), 2 lb/ft3 aluminum honeycomb; 3/8” (9.5mm) cell size, .0007” (0.018mm) thick film, 5056 aluminum. Bonded using heat activated epoxy tape. Outer skins 10 mil (.25mm) thick, quasi isotropic GFRP (glass fiber reinforced polymer);– 4 plies [0/45/90/-45], pre-preg unidirectional tape– M55J graphite fiber, 954-3 cyanate ester matrix, 60% FVF– Each panel 7.1 mm thick, RL 0.376%

• Thermal back-plane– 0.25mm TPG core– 0.13mm GFRP face sheets, 2 layers M55J/954-3, [0/90]

• HDI– 176 micron thick– 4 copper planes (ground, power, 2ea. Signal), 5 Kapton films, 8 glue layers

• Mini-strip Silicon Sensor– 300 micron thick

• Bonds– Rigid bonds – unloaded, exception sensor to HDI thermally conductive epoxy

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PHENIX Radiation Length of Baseline Design

• Panel total %RL– Worst case = 2.16%RL

• Using average of ROC+bond and SSD+bond

– Area averaged = 1.84%RL

• Detector and HDI account for >40% of total (area averaged)

Stackup of RL contributions for ½ FVTX panel(from mid-plane to detectors)

0.0%

0.2%

0.4%

0.6%

0.8%

1.0%

1.2%

1.4%

1.6%

absolute / worst case area averaged

Panel core (1/2)Bond: core to FS

Backplane FS (1)

Backplane core

Backplane FS (2)

Bus

Bond: Detector to bus

Detector

Bond: ROC to bus

ROC

Panel FS

Bond: panel to backplane

Bond: bus to backplane

0.0%

0.2%

0.4%

0.6%

0.8%

1.0%

1.2%

1.4%

1.6%


Panel core (1/2)Bond: core to FS

Panel FS

Bond: panel to backplaneBackplane FS (1)

Backplane core

Backplane FS (2)Bond: bus to backplane

Bus

Detector

ROC

Bond: Detector to bus

Bond: ROC to bus

0.0%

0.2%

0.4%

0.6%

0.8%

1.0%

1.2%

1.4%

1.6%


Distribution of area-averaged RL: 1/2 FVTX plane

0.000%

0.050%

0.100%

0.150%

0.200%

0.250%

Strip

Detec

tor

Reado

ut Chip

SD-Bus

bon

d

ROC-B

us bon

d

Bus/H

DI

Bus-B

ackp

lane

bon

d

Backp

lane

FS

Backp

lane

core

Backp

lane

FS

Backp

lane-

pane

l bon

d

Face sh

eet

Face sh

eet-C

ore

bond

Core

(1/2

)

One or the other, not both

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Baseline design for the VTX and FVTX detectors;

FVTX-ROC

FVTX - 4 detector planes each end

Each big wheel will have 5 planes of read-out electronics, with one cooling plate for each plane


FVTX support cage: 4 stations:

Support cage is a similar structure to the detector support panels – aluminum honeycomb with GFRP skins. Each half cage meshes to the mating half cage to help relieve “drum-head” effects. Each station has 15 degree sensor panels mounted on both sides – offset in phi by 7.5 degrees.

FVTX mounting tabs


sensor

HDI

thermal planeCooling tube

Detail view of FVTX support cage with panels:

PHX chips

Support cage – al. honeycomb with graphite fiber reinforced polymer (GFRP) face sheets


HYTEC has integrated the proposed HDI to the “wedge”, that will work for all wedges.

Note that the current model allows for a mech mounting for each wedge using pins and screws

PHENIX HYTEC - THERMAL FEA:• Model represents old (worst case) baseline

– 35.mm IR– 28 - ROC’s per SSD– About 8% more heat, and 8% longer radial heat transfer path

• Readout chip heat generation:– Waste heat per channel: 100 W– Channels per chip: 128– One chip volume : 0.009×0.0015×0.0003=4.05×10-9m3

– Heat generation per chip: 0.0128/4.05×10-9=3.16049×106W/m3

• Backplane layup:– TPG core, 0.246mm thick– Symmetric [0°/90°] Gr/CyE face sheets (each layer 0.0635mm thick)– Total thickness: 0.5mm

• Effective backplane thermal conductivities (estimated):– Kx=755.83 W/m.K– Ky=755.83 W/m.K– Kz=1.88 W/m.K

• Edge cooling at 0°C (arbitrary temperature at this point)– Backplane nodes on the outer edge are kept at 0°C– Additional temp. drop from backplane OD to fluid bulk temperature not yet included

• HT coefficient + TTT drops in tube wall, face sheets, bonds, etc.

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PHENIX 3-D FE Model

• Mesh:– 158,225 nodes and 270,220 elements

– 3-D solid elements for: backplane, glues, Kapton bus, readout chips, and strip detector

• Loads:– Volumetric heat generation in the readout chips

– Edge cooling at 0°C

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PHENIX 3-D Temperature Contour

• With conductive epoxy (1.5W/mK) between ROC & HDI• Temperature in ºC

– Assuming outer edge of TPG held at 0ºC• Warmest ROC at 2.55ºC

– 2.5ºC <<< 50ºC– Backplane much more conductive than required

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PHENIX Concluding Remarks on Thermal FEA

• Baseline design is simple and modular – still evolving– Duplicate functions: backplane + panel face sheets– Lots of bonds– Expensive & problematic materials (TPG) may not be needed– Good enough?

• Easily meets temperature requirements with edge cooling alone? (TBC)– ROC temperature < 2.6ºC– Not accounting for convection into N2, i.e. conservative– Using TPG (~750 W/mK) may be a waste

• Try CC (~240 W/mK, or 3× lower) or even GFRP (~75 W/mK, 10× lower)?– No need for thermal vias through HDI

• Future work– Finalize specification document?– Extend model to mid-plane (represent panel)

• More detailed representation of cooling channel– Explore other back-plane material options– Evaluate stresses and select adhesives– Evaluate effect of convective HT (negligible?)– Cooling & flow calculations– Iterate!

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Comments by Eric Ponslet from HYTEC

PHENIX HYTEC - MECHANICAL FEA:

System level FEA Summary PHENIX VTX & FVTX

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PHENIX FVTX Disks

•Honeycomb core sandwich panel are used for the disks

-Symmetric quasi-isotropic [-45/90/45/0] M55J/954-3 face-sheets (ti=0.0635mm)

-Aluminum honeycomb core (32.0Kg/m3, t=6.35mm)

-Total thickness: 6.858mm

-Attached electronics are modeled as non-structural mass (~4.255 Kg/m2)

-Approximate mass of half disk: 0.234Kg (everything included)

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PHENIX FVTX Cage

•Honeycomb Al Core with Gr/E face sheets is used for the FVTX cage

•Cutout design is a baseline design

•Disks are attached to the cage at three tabs in the current design

•Each half of the cage is connected to the space frame at two tabs

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PHENIX FVTX Stand Alone Modal Analysis

Assumed to be fixed at the support tabs– First mode: 83.9 Hz (over predicted because of the fixed support assumption)– Even higher than the “ideal” frequency of 75Hz!– Potentially a less stiff structure could be used– Adding additional supports at the back of the cage would improve the frequency– Connecting half disks for each layer using pins and/or clips

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PHENIX VTX & FVTX Assembly

First Mode: 38Hz (derived by the barrel mounts)

Can be improved by:– Connecting layer 4 barrel mounts to the space frame at 3 points rather than 2.– Increasing the thickness of the HC Al Core for the barrel mounts– Increasing the width of the barrel mounts at the base.

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PHENIX System Level FEM Model

•System level model as of 10/13/2006 (cf. HTN-111006-0002)

•First Mode: 24.5Hz (Drum Head mode)

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PHENIX Barrel Mount Bracings

•Bracings (baseline HC core sandwich panels) are added to improve the stiffness

•First mode increases by 55% to 38Hz

Barrel Mount Bracings

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PHENIX VTX Deformation Summary

X Y Z X Y Z X Y Z

Normal toTP Plane

In TP Plane Long. AxisNormal toTP Plane


In TP Plane Long. Axis

1 -8.1 -7.3 -0.9 -73.2 32.5 6.1 -75.0 32.0 6.2

2 -12.5 -13.0 -1.1 -89.9 25.0 6.4 -97.5 25.3 6.5

3 -33.0 -24.9 -1.2 -194.6 8.1 9.5 -215.7 -25.0 9.4

4 -89.7 -56.5 2.2 -302.6 -6.8 11.3 -386.6 -56.6 12.5

Stave Absolute Deformations (microns)Bottom and Top Kinematic Supports

VTX with Barrel Mount Bracings

Gravity Thermal (-21.11°C) Gravity+Thermal

Layer

• Staves deformation summary with barrel mount bracings installed- Max deflection is reduced by 4%

• Staves deformation summary with barrel mount bracings and FVTX installed

X Y Z X Y Z X Y Z

Normal toTP Plane



In TP Plane Long. Axis

1 -8.1 -7.4 -0.6 -73.2 32.5 6.1 -75.0 32.1 6.1

2 -12.5 -13.0 -0.8 -89.9 25.0 6.4 -97.5 25.4 6.4

3 -33.0 -25.0 -0.9 -194.6 8.1 9.6 -215.8 -25.0 9.3

4 -89.7 -56.5 1.9 -302.6 -6.8 11.4 -386.5 -56.6 12.3

Stave Absolute Deformations (microns)Bottom and Top Kinematic Supports

VTX with Barrel Mount Bracings

Gravity Thermal (-21.11°C) Gravity+Thermal

Layer

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PHENIX PHENIX Assembly on Support Stand

•System level model with Support Stands/Rails–118,814 Nodes–147,536 Elements–712,884 degrees of freedom–First mode: 24Hz –First mode is driven by the support rails

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PHENIX VTX (No Bracings)

First Mode: 24Hz

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PHENIX VTX with Bracings

First Mode: 38Hz

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PHENIX VTX+Bracing+FVTX

First Mode: 38Hz

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PHENIX PHENIX Assembly on Support Stands

First Mode: 24Hz

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• Assembly steps:– 15 degree wedge –

• Mount HDI to the Graphite thermal plane;– Using vacuum fixtures– The HDI Kapton must be mounted as flat as possible, surfaces must

be kept clean prior to bonding – suggest plasma cleaning.• Install surface mount components on to the HDI;

– Be certain that all solder “grunge” has been removed prior to the attachment of the silicon sensor.

• Silcon sensor is attached to the HDI;– Using vacuum fixtures– A suggested bonding agent is 3M 9882 thermally conductive transfer

tape (CMS), 50. microns thick.– http://multimedia.mmm.com/mws/mediawebserver.dyn?

6666660Zjcf6lVs6EVs666yazCOrrrrQ-

• Make wire-bond connections and encapsulate attachment points• Characterize completed 15 degree wedge sensor assembly using a CMM

(Coordinate Measurement Machine).• Mount 15 degree wedges to support panel• Again characterize assemby using CMM

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SIDET lab optical CMM machine, optical resolution in x-y; 3.1 microns uncertainty


SIDET example of touch probe stations, resolution 3.5 micron uncertainty

PHENIX FVTX integration with VTX 33

FVTX mounts to the VTX space frame off of tabs at the front of support cage.

We plan to improve the stabilization of this support cage by adding a “diving board” to the VTX space frame that will pick up an additional support point on the FVTX cage in Z.

PHENIX BNL Review February 19th,2007

• Summary:– A baseline design has been developed that has been studied and

modeled for mechanical and thermal stability, which meet our design requirements.

– A first pass at a process for the assembly of the detectors panels and their integration into the VTX detector system has been developed.

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phenix bnl reviewfebruary 19 th, 2007 1 mechanical design and studies for the fvtx detector, along...

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